Change search
Refine search result
1234 51 - 100 of 200
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 51.
    Griffiths, Jennifer R.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Kadin, Martina
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Tamelander, Tobias
    Törnroos, Anna
    Bonaglia, Stefano
    Stockholm University, Faculty of Science, Department of Geological Sciences. Lund University, Sweden.
    Bonsdorff, Erik
    Brüchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gårdmark, Anna
    Järnström, Marie
    Kotta, Jonne
    Lindegren, Martin
    Nordström, Marie C.
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Olsson, Jens
    Weigel, Benjamin
    Zydelis, Ramunas
    Blenckner, Thorsten
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Niiranen, Susa
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Winder, Monika
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    The importance of benthic-pelagic coupling for marine ecosystem functioning in a changing world2017In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 23, no 6, p. 2179-2196Article, review/survey (Refereed)
    Abstract [en]

    Benthic-pelagic coupling is manifested as the exchange of energy, mass, or nutrients between benthic and pelagic habitats. It plays a prominent role in aquatic ecosystems, and it is crucial to functions from nutrient cycling to energy transfer in food webs. Coastal and estuarine ecosystem structure and function are strongly affected by anthropogenic pressures; however, there are large gaps in our understanding of the responses of inorganic nutrient and organic matter fluxes between benthic habitats and the water column. We illustrate the varied nature of physical and biological benthic-pelagic coupling processes and their potential sensitivity to three anthropogenic pressures - climate change, nutrient loading, and fishing - using the Baltic Sea as a case study and summarize current knowledge on the exchange of inorganic nutrients and organic material between habitats. Traditionally measured benthic-pelagic coupling processes (e.g., nutrient exchange and sedimentation of organic material) are to some extent quantifiable, but the magnitude and variability of biological processes are rarely assessed, preventing quantitative comparisons. Changing oxygen conditions will continue to have widespread effects on the processes that govern inorganic and organic matter exchange among habitats while climate change and nutrient load reductions may have large effects on organic matter sedimentation. Many biological processes (predation, bioturbation) are expected to be sensitive to anthropogenic drivers, but the outcomes for ecosystem function are largely unknown. We emphasize how improved empirical and experimental understanding of benthic-pelagic coupling processes and their variability are necessary to inform models that can quantify the feedbacks among processes and ecosystem responses to a changing world.

  • 52.
    Guban, Peter
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Wennerström, Lovisa
    Stockholm University, Faculty of Science, Department of Zoology.
    Elfvving, Tina
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Sundelin, Brita
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Laikre, Linda
    Stockholm University, Faculty of Science, Department of Zoology.
    Genetic diversity in Monoporeia affinis at polluted and reference sites of the Baltic Bothnian Bay2015In: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 93, no 1-2, p. 245-249Article in journal (Refereed)
    Abstract [en]

    The amphipod Monoporeia affinis plays an important role in the Baltic Sea ecosystem as prey and as detritivore. The species is monitored for contaminant effects, but almost nothing is known about its genetics in this region. A pilot screening for genetic variation at the mitochondrial COI gene was performed in 113 individuals collected at six sites in the northern Baltic. Three coastal sites were polluted by pulp mill effluents, PAHs, and trace metals, and two coastal reference sites were without obvious connection to pollution sources. An off-coastal reference site was also included. Contaminated sites showed lower levels of genetic diversity than the coastal reference ones although the difference was not statistically significant. Divergence patterns measured as Phi(ST) showed no significant differentiation within reference and polluted groups, but there was significant genetic divergence between them. The off-coastal sample differed significantly from all coastal sites and also showed lower genetic variation.

  • 53. Gustafsson, Camilla
    et al.
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Quantifying the importance of functional traits for primary production in aquatic plant communities2019In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 107, no 1, p. 154-166Article in journal (Refereed)
    Abstract [en]

    1. Aquatic plant meadows are important coastal habitats that sustain many ecosystem functions such as primary production and carbon sequestration. Currently, there is a knowledge gap in understanding which plant functional traits, for example, leaf size or plant height underlie primary production in aquatic plant communities.

    2. To study how plant traits are related to primary production, we conducted a field survey in the Baltic Sea, Finland, which is characterized by high plant species and functional diversity. Thirty sites along an exposure gradient were sampled (150 plots), and nine plant morphological and chemical traits measured. The aim was to discern how community-weighted mean traits affect community production and whether this relationship changes along an environmental gradient using structural equation modelling (SEM).

    3. Plant height had a direct positive effect on production along an exposure gradient (r=0.33) and indirect effects through two leaf chemical traits, leaf delta N-15 and leaf delta C-13 (r=0.24 and 0.18, respectively) resulting in a total effect of 0.28. In plant communities experiencing varying exposure, traits such as root N concentration and leaf delta N-15 had positive and negative effects on production, respectively.

    4. Synthesis. Our results demonstrate that the relationship between aquatic plant functional traits and community production is variable and changes over environmental gradients. Plant height generally has a positive effect on community production along an exposure gradient, while the link between other traits and production changes in plant communities experiencing varying degrees of exposure. Thus, the underlying biological mechanisms influencing production differ in plant communities, emphasizing the need to resolve variability and its drivers in real-world communities. Importantly, functionally diverse plant communities sustain ecosystem functioning differently and highlight the importance of benthic diversity for coastal ecosystem stability.

  • 54.
    Gustafsson, Erik
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Deutsch, Barbara
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Carbon cycling in the Baltic Sea - The fate of allochthonous organic carbon and its impact on air-sea CO2 exchange2014In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 129, p. 289-302Article in journal (Refereed)
    Abstract [en]

    A coupled physical-biogeochemical model (BALTSEM) is used to estimate carbon fluxes in the Baltic Sea over the 1980-2006 period. Budget calculations for organic carbon indicate that of the total allochthonous organic carbon (TOCT) supplied to the system, on average 56% is mineralized, 36% is exported out of the system, and the remainder is buried. River discharge is the main source of dissolved inorganic carbon (DIC) to the Baltic Sea. However, model results indicate that in the Gulf of Bothnia (northern Baltic Sea), the contribution to the DIC stock by TOCT mineralization is of the same order as direct river input of DIC In the Kattegat and Danish Straits (southwestern Baltic Sea) on the other hand, net uptake of atmospheric CO2 comprises the major DIC source. Despite large variations within the system, with net outgassing from some sub-basins and net absorption in others, the Baltic Sea as a whole was estimated to be a net sink for atmospheric CO2. Mineralization of allochthonous dissolved organic carbon (DOCT) influences air-sea CO2 exchange. A sensitivity study indicates that depending on the labile fraction of DOCT, the contribution from CO2 absorption to total external DIC sources can amount to 10-25%.

  • 55.
    Gustafsson, Erik
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Hagens, Mathilde
    Sun, Xiaole
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Reed, Daniel C.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. University of Helsinki, Finland.
    Slomp, Caroline P.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. University of Helsinki, Finland.
    Sedimentary alkalinity generation and long-term alkalinity development in the Baltic Sea2019In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 16, no 2, p. 437-456Article in journal (Refereed)
    Abstract [en]

    Enhanced release of alkalinity from the seafloor, principally driven by anaerobic degradation of organic matter under low-oxygen conditions and associated secondary redox reactions, can increase the carbon dioxide (CO2) buffering capacity of seawater and therefore oceanic CO2 uptake. The Baltic Sea has undergone severe changes in oxygenation state and total alkalinity (TA) over the past decades. The link between these concurrent changes has not yet been investigated in detail. A recent system-wide TA budget constructed for the past 50 years using BALTSEM, a coupled physical-biogeochemical model for the whole Baltic Sea area, revealed an unknown TA source. Here we use BALTSEM in combination with observational data and one-dimensional reactive transport modelling of sedimentary processes in the Fårö Deep, a deep Baltic Sea basin, to test whether sulfate reduction coupled to iron (Fe) sulfide burial can explain the missing TA source in the Baltic Proper. We calculated that this burial can account for 26% of the missing source in this basin, with the remaining TA possibly originating from unknown river inputs or submarine groundwater discharge. We also show that temporal variability in the input of Fe to the sediments since the 1970s drives changes in sulfur burial in the Fårö Deep, suggesting that Fe availability is the ultimate limiting factor for TA generation under anoxic conditions. The implementation of projected climate change and two nutrient load scenarios for the 21st century in BALTSEM shows that reducing nutrient loads will improve deep water oxygen conditions, but at the expense of lower surface water TA concentrations, CO2 buffering capacities and faster acidification. When these changes additionally lead to a decrease in Fe inputs to the sediment of the deep basins, anaerobic TA generation will be reduced even further, thus exacerbating acidification. This work highlights that Fe dynamics play a key role in the release of TA from sediments where Fe sulfide formation is limited by Fe availability, as exemplified for the Baltic Sea. Moreover, it demonstrates that burial of Fe sulfides should be included in TA budgets of low oxygen basins.

  • 56.
    Gustafsson, Erik
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Björk, Göran
    Stranne, Christian
    Stockholm University, Faculty of Science, Department of Geological Sciences. University of New Hampshire, USA.
    Andersson, Leif G.
    Geibel, Marc C.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Sundbom, Marcus
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Semiletov, Igor P.
    Thornton, Brett F.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Carbon cycling on the East Siberian Arctic Shelf – a change in air-sea CO2 flux induced by mineralization of terrestrial organic carbon2017In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189Article in journal (Refereed)
    Abstract [en]

    Measurements from the SWERUS-C3 and ISSS-08 Arctic expeditions were used to calibrate and validate a new physical-biogeochemical model developed to quantify key carbon cycling processes on the East Siberian Arctic Shelf (ESAS). The model was used in a series of experimental simulations with the specific aim to investigate the pathways of terrestrial dissolved and particulate organic carbon (DOCter and POCter) supplied to the shelf. Rivers supply on average 8.5 Tg C yr−1 dissolved inorganic carbon (DIC), and further 8.5 and 1.1 Tg C yr−1 DOCter and POCter respectively. Based on observed and simulated DOC concentrations and stable isotope values (δ13CDOC) in shelf waters, we estimate that only some 20 % of the riverine DOCter is labile. According to our model results, an additional supply of approximately 14 Tg C yr−1 eroded labile POCter is however required to describe the observed stable isotope values of DIC (δ13CDIC). Degradation of riverine DOCter and POCter results in a 1.8 Tg C yr−1 reduction in the uptake of atmospheric CO2, while degradation of eroded POCter results in an additional 10 Tg C yr−1 reduction. Our calculations indicate nevertheless that the ESAS is an overall small net sink for atmospheric CO2 (1.7 Tg C yr−1). The external carbon sources are largely compensated by a net export from the shelf to the Arctic Ocean (31 Tg C yr−1), and to a smaller degree by a permanent burial in the sediments (2.7 Tg C yr−1).

  • 57.
    Gustafsson, Erik
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. Stockholm University, Faculty of Science, Department of Geological Sciences.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Modelling the C-13 and C-12 isotopes of inorganic and organic carbon in the Baltic Sea2015In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 148, p. 122-130Article in journal (Refereed)
    Abstract [en]

    In this study, C-12 and C-13 contents of all carbon containing state variables (dissolved inorganic and organic carbon, detrital carbon, and the carbon content of autotrophs and heterotrophs) have for the first time been explicitly included in a coupled physical-biogeochemical Baltic Sea model. Different processes in the carbon cycling have distinct fractionation values, resulting in specific isotopic fingerprints. Thus, in addition to simulating concentrations of different tracers, our new model formulation improves the possibility to constrain the rates of processes such as CO2 assimilation, mineralization, and air-sea exchange. We demonstrate that phytoplankton production and respiration, and the related air-sea CO2 fluxes, are to a large degree controlling the isotopic composition of organic and inorganic carbon in the system. The isotopic composition is further, but to a lesser extent, influenced by river loads and deep water inflows as well as transformation of terrestrial organic carbon within the system. Changes in the isotopic composition over the 20th century have been dominated by two processes the preferential release of C-12 to the atmosphere in association with fossil fuel burning, and the eutrophication of the Baltic Sea related to increased nutrient loads under the second half of the century.

  • 58.
    Gustafsson, Erik
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Omstedt, Anders
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    The air-water CO2 exchange of a coastal sea – a sensitivity study on factors that influence the absorption and outgassing of CO2 in the Baltic Sea2015In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 120, no 8, p. 5342-5357Article in journal (Refereed)
    Abstract [en]

    In this study, the BALTSEM model is used to estimate how air-water CO2 fluxes in the Baltic Sea respond to parameterizations of organic alkalinity (Aorg), gas transfer, and phytoplankton growth, and further to changes in river loads. The forcing data include the most complete compilation of Baltic river loads for dissolved inorganic and organic carbon (DIC and DOC) and total alkalinity (TA). In addition, we apply the most recent estimates of internal TA generation in the system. Our results clearly demonstrate how air-water CO2 fluxes of a coastal sea depend on river loads of carbon, TA, and nutrients as well the freshwater import itself. Long-term changes in DIC loads are shown to be compensated by corresponding changes in air-water CO2 exchange. By adding Aorg, a discrepancy in the carbonate system calculations was removed, and the simulated net CO2 absorption of the system decreased by 11%. A new parameterization for cyanobacteria growth significantly improved the seasonal development of pCO2 in the central Baltic Sea, although the net effect on CO2 fluxes was below 5%. By applying either a linear, quadratic, or cubic wind speed dependence for gas transfer, the long-term net CO2 exchange was adjusted by less than 5%. There is no clear indication that any one of these parameterizations provides a more accurate estimate of CO2 fluxes than the other two. Our findings are applicable in other coastal areas that are heavily influenced by river loads of TA, DIC, and DOC.

  • 59.
    Gustafsson, Erik
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Savchuck, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Müller-Karulis, Bärbel
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Key processes in the coupled carbon, nitrogen, and phosphorus cycling of the Baltic Sea2017In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 134, no 3, p. 301-317Article in journal (Refereed)
    Abstract [en]

    In this study we examine pools of carbon (C), nitrogen (N), and phosphorus (P) in the Baltic Sea, both simulated and reconstructed from observations. We further quantify key fluxes in the C, N, and P cycling. Our calculations include pelagic reservoirs as well as the storage in the active sediment layer, which allows a complete coverage of the overall C, N, and P cycling on a system-scale. A striking property of C versus N and P cycling is that while the external supplies of total N and P (TN and TP) are largely balanced by internal removal processes, the total carbon (TC) supply is mainly compensated by a net export out of the system. In other words, external inputs of TN and TP are, in contrast to TC, rather efficiently filtered within the Baltic Sea. Further, there is a net export of TN and TP out of the system, but a net import of dissolved inorganic N and P (DIN and DIP). There is on the contrary a net export of both the organic and inorganic fractions of TC. While the pelagic pools of TC and TP are dominated by inorganic compounds, TN largely consists of organic N because allochthonous organic N is poorly degradable. There are however large basin-wise differences in C, N, and P elemental ratios as well as in inorganic versus organic fractions. These differences reflect both the differing ratios in external loads and differing oxygen conditions determining the redox-dependent fluxes of DIN and DIP.

  • 60.
    Gustafsson, Erik
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Wällstedt, Teresia
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Humborg, Christoph
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    External total alkalinity loads versus internal generation: The influence of nonriverine alkalinity sources in the Baltic Sea2014In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 28, no 11, p. 1358-1370Article in journal (Refereed)
    Abstract [en]

    In this study we first present updated riverine total alkalinity (TA) loads to the various Baltic Sea sub-basins, based on monthly measurements in 82 of the major rivers that represent 85% of the total runoff. Simulations in the coupled physical-biogeochemical BALTSEM (BAltic sea Long-Term large Scale Eutrophication Model) model show that these river loads together with North Sea water inflows are not sufficient to reproduce observed TA concentrations in the system, demonstrating the large influence from internal sources. Budget calculations indicate that the required internal TA generation must be similar to river loads in magnitude. The nonriverine source in the system amounts to about 2.4mmolm(-2) d(-1) on average. We argue here that the majority of this source is related to denitrification together with unresolved sediment processes such as burial of reduced sulfur and/or silicate weathering. This hypothesis is supported by studies on sediment processes on a global scale and also by data from sediment cores in the Baltic Sea. In a model simulation with all internal TA sources and sinks switched on, the net absorption of atmospheric CO2 increased by 0.78mol C m(-2) yr(-1) compared to a simulation where TA was treated as a passive tracer. Our results clearly illustrate how pelagic TA sources together with anaerobic mineralization in coastal sediments generate a significant carbon sink along the aquatic continuum, mitigating CO2 evasions from coastal and estuarine systems.

  • 61.
    Halling, Christina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Tano, Stina
    Eggertsen, Maria
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Buriyo, Amelia
    Msuya, Flower
    Wikström, Sofia
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    The introduction of South East Asian seaweed and its ecological implications; Can native East African Eucheuma denticulatum and Kappaphycus alvarezii be a potential alternative for farming?Manuscript (preprint) (Other academic)
    Abstract [en]

    The seaweed farming of eucheumoids in East Africa is solely based on introduced South East Asian (SEA) haplotypes of the carrageenophytes Eucheuma and Kappaphycus. As overexploitation of natural seaweed resources lead to a decline in harvest and export, commercial seaweed farming was started using highly productive SEA strains of the same genus introduced from the Philippines to Zanzibar in 1989.  Initially, productivity was high, the sector grew rapidly and seaweed farming soon became an important livelihood. Today, the industry faces various challenges such as decreased productivity and high rates of diseases and epiphytic infestations. Continuous introduction of foreign stock for cultivation vitalization might not be the solution, as escapees of SEA Eucheuma denticulatum have been found spreading into natural environments around Zanzibar with uncertain ecological consequences.  We suggest that indigenous haplotypes of E. denticulatum and Kappaphycus alvarezii should be re-evaluated for farming potential,  for increasing the genetic diversity and hence resilience within stocks.

    This study is a first step towards a reassessment of farming potential of East African (EA) haplotypes. Molecularly identified haplotypes of E. denticulatum and K. alvarezii were tested in in-situ farming conditions in Zanzibar, and growth rates, grazing and epiphytes were compared between EA and SEA haplotypes. Results show, except for an overall decreased growth compared to previous studies, that growth rate was site dependent and that SEA Eucheuma haplotypes have a higher growth rate (1.3 ±1.8 - 3.6 ±1.9% per day) compared to EA haplotypes (0.2 ±1.0 - 2.0 ±0.4% per day). No significant differences were found in grazing rate between native and introduced Eucheuma haplotypes, while native Kappaphycus was more prone to grazing. 

    In conclusion the farming potential for native E. denticulatum, is not rejected but underlines that there is an urgent need of continued search for native East African seaweed resources and a further identification of their desirable traits. If successful, this would enable East African seaweed industry to further expansion and secure its ecological and economical sustainability.

  • 62.
    Hansen, Joakim
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Uppföljning av bottenvegetation i grunda Östersjövikar: Varians- och precisionsanalyser av data insamlade med visuella metoder genom snorkling2016Report (Other academic)
    Abstract [sv]

    Syftet med den här studien var att analysera variation i bottenvegetation i tid och rum, samt precision i insamlandet av data för att ge rekommendationer för uppföljning av grunda vikar i Östersjön (habitatdirektivets naturtyp laguner 1150, med undergrupperna 1153 och 1154). I studien har variation analyserats avseende skillnader på olika geografisk skala (vik, län, havsområde) samt inventeringsår. Analysen utfördes på data som samlats in i den här miljön i lite mer än ett decennium (2001–2014), där stickprovsmetoder med visuell observation i 50×50-cm prov längs transekter eller slumpvist placerade stationer á 10 m diameter tillämpats. De responsvariabler som studerades var antal arter, antal typiska arter, täckningsgrad, två index baserade på indikatorarter, samt andelen långskottsvegetation. Variationen i de undersökta variablerna var störst inom vikar och mellan vikar, medan den var liten mellan län och havsområden. Det var även en viss variation mellan år, men den var inte samstämmig mellan vikar de olika åren. Vegetationens täckningsgrad varierade mest medan antalet arter och indexet beräknat på antalet indikatorarter varierade minst. Baserat på resultaten föreslås för samtliga havsområden att minst 100 små inventerings-rutor (0,25 m2) eller 30 större stationer (79 m2) bör inventeras per vik för att få en god precision* i medelvärdesskattning av antal arter och täckningsgraden av bottenvegetation per vik. Detta motsvarar ungefär 8 arbetstimmar med den första metoden, respektive 20 arbetstimmar med den andra metoden (fördelat på två personer). Med en lägre provtagningsinsats om 70 små inventeringsrutor (ca 6 h) eller 12 stationer (8 h) per vik nås en lägre men acceptabel precision**. Vid uppföljning av antal arter, typiska arter, täckningsgrad, indikatorartsindexen och andel långskottsvegetation på havsområdesnivå krävs att minst 16 vikar undersöks för att nå en god precision* i norra Egentliga Östersjön. För kumulativt artantal krävs att minst 8 vikar per naturtypsundergrupp provtas eftersom antalet arter och artsammansättningen skiljer mellan naturtypsundergrupperna i det här havsområdet. Då variationen mellan vikar var större i södra Egentliga Östersjön och Bottniska viken än i norra Egentliga Östersjön krävs en provtagning av 20 till 30 vikar per havsområde för att nå en god precision* i medelvärdesskattningar av de undersökta responsvariablerna i de två förstnämnda havsområdena. Med 16 vikar per havsområde når man dock en lägre, men acceptabel, precisionsnivå**. För god precision avseende mellanårsvariation föreslås en provtagning om sex år för de undersökta uppföljningsvariablerna. Resultaten som redovisas i den här studien kompletterar de undersökningar som gjorts av variation i fiskyngelförekomst i samma typ av Östersjövikar och tillsammans kan studierna utgöra en grund för att utforma uppföljningsprogram av grunda vikar i Östersjön.

  • 63.
    Hansen, Joakim P.
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Snickars, Martin
    Applying macrophyte community indicators to assess anthropogenic pressures on shallow soft bottoms2014In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 738, no 1, p. 171-189Article in journal (Refereed)
    Abstract [en]

    Vegetated soft bottoms are under pressure due to a number of anthropogenic stressors, such as coastal exploitation and eutrophication. The ecological value of these biotopes has gained recognition through international conventions and the EU directives, which request methods for assessment of the environmental status of coastal areas. However, currently there is no appropriate method for assessing the status of shallow vegetated soft bottoms in the northern Baltic Sea. Therefore, we developed a macrophyte community index and tested its response in relation to important pressures (eutrophication and boating activity) and natural gradients (topographic openness, depth and salinity) on shallow bays in the northern Baltic Sea. The macrophyte index, and hence the proportion of sensitive to tolerant species, decreased with increasing phosphorus concentration, turbidity and level of boating activity, while the cumulative cover of macrophytes only showed a negative trend in response to increasing turbidity. Juvenile fish abundance was positively related to the index, indicating importance of sensitive macrophyte species for ecosystem functioning. As the index was tested in a wide geographic area, and showed a uniform response across natural gradients, it is a promising tool for assessment of environmental status that may be applied also in other vegetated soft-bottom areas.

  • 64.
    Hansen, Joakim P.
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Sundblad, Göran
    Bergström, Ulf
    N. Austin, Åsa
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Donadi, Serena
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Swedish University of Agricultural Sciences (SLU), Sweden.
    Eriksson, Britas Klemens
    Eklöf, Johan S.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Recreational boating degrades vegetation important for fish recruitment2019In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 48, no 6, p. 539-551Article in journal (Refereed)
    Abstract [en]

    Recreational boating increases globally and associated moorings are often placed in vegetated habitats important for fish recruitment. Meanwhile, assessments of the effects of boating on vegetation, and potential effects on associated fish assemblages are rare. Here, we analysed (i) the effect of small-boat marinas on vegetation structure, and (ii) juvenile fish abundance in relation to vegetation cover in shallow wave-sheltered coastal inlets. We found marinas to have lower vegetation cover and height, and a different species composition, compared to control inlets. This effect became stronger with increasing berth density. Moreover, there was a clear positive relationship between vegetation cover and fish abundance. We conclude that recreational boating and related moorings are associated with reduced cover of aquatic vegetation constituting important habitats for juvenile fish. We therefore recommend that coastal constructions and associated boating should be allocated to more disturbance tolerant environments (e.g. naturally wave-exposed shores), thereby minimizing negative environmental impacts.

  • 65.
    Hedberg, Nils
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Stenson, Isabell
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Nitz Pettersson, Mika
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Warshan, Denis
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Nguyen-Kim, H.
    Tedengren, Michael
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Kautsky, Nils
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Antibiotic use in Vietnamese fish and lobster sea cage farms; implications for coral reefs and human health2018In: Aquaculture, ISSN 0044-8486, E-ISSN 1873-5622, Vol. 495, p. 366-375Article in journal (Refereed)
    Abstract [en]

    Several papers have reported on the development of antibiotic resistance and implications for human medicine but fewer deal with environmental impacts of antibiotic use. Marine sea cage aquaculture in SE Asia is often established close to coral reef ecosystems. Large amounts of antibiotics are used in the cultivation of fish and lobster and hence released directly into the environment. This study investigates the antibiotic practices in sea cage farms producing fish and spiny lobster in Vietnam, mainly for the domestic market. There are approximately 3500 sea cage farms in Vietnam and we performed semi-structured interviews with 109 sea cage farmers asking them if they use antibiotics and if so; what sort/when/how often/how much. We found that the Vietnamese cage farmers are using antibiotics in an unstructured way, which seems to have little or no effect on the survival of the stock, or profit of the farm. The fact that the farmers live at their farm and use the sea next to the cages both for fishing and collecting filter-feeding bivalves for direct consumption, as well as a toilet, poses an additional risk for the spreading of human antibiotic resistant pathogens. Thirteen different antibiotics were found in the study. Eighty-two percentage of the lobster farmers and 28% of the fishfarmers used antibiotics. The average amounts used were over 5 kg per produced ton of lobster and about 0.6 kg per ton of fish, which is much higher than in other studies. Several antibiotic substances listed as critical and highly important for human medicine by WHO were used prophylactically and routinely with little control and enforcement of regulations. We tested and detected antibiotic resistance to Tetracycline, Vancomycin and Rifampicin in the coral associated bacteria Bacillus niabensis as far as 660m from fish farms with resistance decreasing with distance from the cage farms. The antibiotics are likely to have negative effects on the coral-symbiont relationship adding further risks to an already stressed environment.

  • 66. Hermans, Martijn
    et al.
    K. Lenstra, Wytze
    van Helmond, Niels A. G. M.
    Behrends, Thilo
    Egger, Matthias
    Séguret, Marie J. M.
    Gustafsson, Erik
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. University of Helsinki, Finland.
    Slomp, Caroline P.
    Impact of natural re-oxygenation on the sediment dynamics of manganese, iron and phosphorus in a euxinic Baltic Sea basin2019In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 246, p. 174-196Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea is characterized by the largest area of hypoxic (oxygen (O2) < 2 mg L−1) bottom waters in the world’s ocean induced by human activities. Natural ventilation of these O2-depleted waters largely depends on episodic Major Baltic Inflows from the adjacent North Sea. In 2014 and 2015, two such inflows led to a strong rise in O2 and decline in phosphate (HPO42−) in waters below 125 m depth in the Eastern Gotland Basin. This provided the opportunity to assess the impact of such re-oxygenation events on the cycles of manganese (Mn), iron (Fe) and phosphorus (P) in the sediment for the first time. We demonstrate that the re-oxygenation induced the activity of sulphur (S)-oxidising bacteria, known as Beggiatoaceae in the surface sediment where a thin oxic and suboxic layer developed. At the two deepest sites, strong enrichments of total Mn and to a lesser extent Fe oxides and P were observed in this surface layer. A combination of sequential sediment extractions and synchrotron-based X-ray spectroscopy revealed evidence for the abundant presence of P-bearing rhodochrosite and Mn(II) phosphates. In contrast to what is typically assumed, the formation of Fe oxides in the surface sediment was limited. We attribute this lack of Fe oxide formation to the high flux of reductants, such as sulphide, from deeper sediments which allows Fe(II) in the form of FeS to be preserved and restricts the penetration of O2 into the sediment. We estimate that enhanced P sequestration in surface sediments accounts for only ∼5% of water column HPO42− removal in the Eastern Gotland Basin linked to the recent inflows. The remaining HPO42− was transported to adjacent areas in the Baltic Sea. Our results highlight that the benthic O2 demand arising from the accumulation of organic-rich sediments over several decades, the legacy of hypoxia, has major implications for the biogeochemical response of euxinic basins to re-oxygenation. In particular, P sequestration in the sediment in association with Fe oxides is limited. This implies that artificial ventilation projects that aim at removing water column HPO42− and thereby improving water quality in the Baltic Sea will likely not have the desired effect.

  • 67. Heymans, Johanna J.
    et al.
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Regime shifts in the Northern Benguela ecosystem: Challenges for management2016In: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 331, p. 151-159Article in journal (Refereed)
    Abstract [en]

    An existing Ecopath with Ecosim model of the Northern Benguela ecosystem for 1956, previously fitted to time series for 50 years, was used to describe the impact that the different pressures (fishing and climate drivers) had on the structure of the ecosystem. Ecological network analysis indices and Integrated Trend Assessment of the input data and model outputs were used to describe the changes in this ecosystem over time. We test the hypothesis that the system has been reorganised over the course of the past 50 years, probably due to the cumulative effects of overfishing and environmental drivers such as the Benguela Nifio, showing two large changes, with a transition period between the early 1970s and the early 1980s. The ecosystem has moved into a new stable state and this reorganised system will need a large shift to change with the consequential change not necessarily being back towards the pre-existing system.

  • 68. Hong, Bongghi
    et al.
    Swaney, Dennis P.
    McCrackin, Michelle
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Svanbäck, Annika
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Gustafsson, Bo
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Yershova, Alexandra
    Pakhomau, Aliaksandr
    Advances in NANI and NAPI accounting for the Baltic drainage basin: spatial and temporal trends and relationships to watershed TN and TP fluxes2017In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 133, no 3, p. 245-261Article in journal (Refereed)
    Abstract [en]

    In order to assess the progress toward eutrophication management goals, it is important to understand trends in land-based nutrient use. Here we present net anthropogenic nitrogen and phosphorus inputs (NANI and NAPI, respectively) for 2000 and 2010 for the Baltic Sea watershed. Overall, across the entire Baltic, between the 5-year periods centered on 2000 and 2010, NANI and NAPI decreased modestly by -6 and -4%, respectively, but with substantial regional variation, including major increases in the Gulf of Riga drainage basin (+19 and +58%, respectively) and decreases in the Danish Straits drainage basin (-25 and -40% respectively). The changes were due primarily to changes in mineral fertilizer use. Mineral fertilizers dominated inputs, at 57% of both NANI and NAPI in 2000, increasing to 68 and 70%, respectively, by 2010. Net food and feed imports declined over that period, corresponding to increased crop production; either fewer imports of food and feedstocks were required to feed humans and livestock, or more of these commodities were exported. A strong linear relationship exists between regional net nutrient inputs and riverine nutrient fluxes for both periods. About 17% of NANI and 4.7% of NAPI were exported to the sea in 2000; these relationships did not significantly differ from those for 2010. Changes in NANI from 2000 to 2010 across basins were directly proportional rather than linearly related to changes in total N (TN) fluxes to the sea (i.e., no change in NANI suggests no change in TN flux). Similarly, for all basins except those draining to the Baltic Proper, changes in NAPI were proportional to changes in total P (TP) fluxes. The Danish Straits decreased most between 2000 and 2010, where NANI and NAPI declined by 25 and 40%, respectively, and corresponding fluxes of TN and TP declined 31 and 18%, respectively. For the Baltic Proper, NAPI was relatively unchanged between 2000 and 2010, while riverine TP fluxes decreased 25%, due possibly to lagged effects of fertilizer reduction resulting from socio-political changes in the early 1990s or improvements in sewage treatment capabilities. For most regions, further reductions in NANI and NAPI could be achieved by more efficient production and greater substitution of manure for imported mineral fertilizers.

  • 69. Horbowy, Jan
    et al.
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Extension of biomass estimates to pre-assessment periods using density dependent surplus production approach2017In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 11, article id e0186830Article in journal (Refereed)
    Abstract [en]

    Biomass reconstructions to pre-assessment periods for commercially important and exploitable fish species are important tools for understanding long-term processes and fluctuation on stock and ecosystem level. For some stocks only fisheries statistics and fishery dependent data are available, for periods before surveys were conducted. The methods for the backward extension of the analytical assessment of biomass for years for which only total catch volumes are available were developed and tested in this paper. Two of the approaches developed apply the concept of the surplus production rate (SPR), which is shown to be stock density dependent if stock dynamics is governed by classical stock-production models. The other approach used a modified form of the Schaefer production model that allows for backward biomass estimation. The performance of the methods was tested on the Arctic cod and North Sea herring stocks, for which analytical biomass estimates extend back to the late 1940s. Next, the methods were applied to extend biomass estimates of the North-east Atlantic mackerel from the 1970s (analytical biomass estimates available) to the 1950s, for which only total catch volumes were available. For comparison with other methods which employs a constant SPR estimated as an average of the observed values, was also applied. The analyses showed that the performance of the methods is stock and data specific; the methods that work well for one stock may fail for the others. The constant SPR method is not recommended in those cases when the SPR is relatively high and the catch volumes in the reconstructed period are low.

  • 70.
    Humborg, Christoph
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Geibel, Marc C.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Anderson, Leif G.
    Björk, Göran
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Sundbom, Marcus
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Thornton, Brett F.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Deutsch, Barbara
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Gustafsson, Erik
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Gustafsson, Bo
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Ek, Jörgen
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Semiletov, Igor
    Sea-air exchange patterns along the central and outer East Siberian Arctic Shelf as inferred from continuous CO2, stable isotope, and bulk chemistry measurements2017In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 31, no 7, p. 1173-1191Article in journal (Refereed)
    Abstract [en]

    This large-scale quasi-synoptic study gives a comprehensive picture of sea-air CO2 fluxes during the melt season in the central and outer Laptev Sea (LS) and East Siberian Sea (ESS). During a 7 week cruise we compiled a continuous record of both surface water and air CO2 concentrations, in total 76,892 measurements. Overall, the central and outer parts of the ESAS constituted a sink for CO2, and we estimate a median uptake of 9.4 g C m(-2) yr(-1) or 6.6 Tg C yr(-1). Our results suggest that while the ESS and shelf break waters adjacent to the LS and ESS are net autotrophic systems, the LS is a net heterotrophic system. CO2 sea-air fluxes for the LS were 4.7 g C m(-2) yr(-1), and for the ESS we estimate an uptake of 7.2 g C m(-2) yr(-1). Isotopic composition of dissolved inorganic carbon (delta C-13(DIC) and delta C-13(CO2)) in the water column indicates that the LS is depleted in delta C-13(DIC) compared to the Arctic Ocean (ArcO) and ESS with an offset of 0.5% which can be explained by mixing of delta C-13(DIC)-depleted riverine waters and 4.0 Tg yr(-1) respiration of OCter; only a minor part (0.72 Tg yr(-1)) of this respired OCter is exchanged with the atmosphere. Property-mixing diagrams of total organic carbon and isotope ratio (delta C-13(SPE-DOC)) versus dissolved organic carbon (DOC) concentration diagram indicate conservative and nonconservative mixing in the LS and ESS, respectively. We suggest land-derived particulate organic carbon from coastal erosion as an additional significant source for the depleted delta C-13(DIC).

  • 71.
    Humborg, Christoph
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Geibel, Marc C.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Sun, Xiaole
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    McCrackin, Michelle
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Stranne, Christian
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gustafsson, Bo
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Sokolov, Alexander
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Norkko, Joanna
    High Emissions of Carbon Dioxide and Methane From the Coastal Baltic Sea at the End of a Summer Heat Wave2019In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 6, article id 493Article in journal (Refereed)
    Abstract [en]

    The summer heat wave in 2018 led to the highest recorded water temperatures since 1926 - up to 21 degrees C - in bottom coastal waters of the Baltic Sea, with implications for the respiration patterns in these shallow coastal systems. We applied cavity ring-down spectrometer measurements to continuously monitor carbon dioxide (CO2) and methane (CH4) surface-water concentrations, covering the coastal archipelagos of Sweden and Finland and the open and deeper parts of the Northern Baltic Proper. This allowed us to (i) follow an upwelling event near the Swedish coast leading to elevated CO2 and moderate CH 4 outgassing, and (ii) to estimate CH4 sources and fluxes along the coast by investigating water column inventories and air-sea fluxes during a storm and an associated downwelling event. At the end of the heat wave, before the storm event, we found elevated CO2 (1583 mu atm) and CH4 (70 nmol/L) concentrations. During the storm, a massive CO2 sea-air flux of up to 274 mmol m(-2) d(-1) was observed. While water-column CO2 concentrations were depleted during several hours of the storm, CH4 concentrations remained elevated. Overall, we found a positive relationship between CO2 and CH4 wind-driven sea-air fluxes, however, the highest CH4 fluxes were observed at low winds whereas highest CO2 fluxes were during peak winds, suggesting different sources and processes controlling their fluxes besides wind. We applied a box-model approach to estimate the CH4 supply needed to sustain these elevated CH4 concentrations and the results suggest a large source flux of CH4 to the water column of 2.5 mmol m(-2) d(-1). These results are qualitatively supported by acoustic observations of vigorous and widespread outgassing from the sediments, with flares that could be traced throughout the water column penetrating the pycnocline and reaching the sea surface. The results suggest that the heat wave triggered CO2 and CH4 fluxes in the coastal zones that are comparable with maximum emission rates found in other hot spots, such as boreal and arctic lakes and wetlands. Further, the results suggest that heat waves are as important for CO2 and CH4 sea-air fluxes as the ice break up in spring.

  • 72. Hutchings, Alec M.
    et al.
    Antler, Gilad
    Wilkening, Jean
    Basu, Anirban
    Bradbury, Harold J.
    Clegg, Josephine A.
    Gorka, Marton
    Lin, Chin Yik
    Mills, Jennifer
    Pellerin, Andre
    Redeker, Kelly R.
    Sun, Xiaole
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Turchyn, Alexandra
    Creek Dynamics Determine Pond Subsurface Geochemical Heterogeneity in East Anglian (UK) Salt Marshes2019In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 7, article id 41Article in journal (Refereed)
    Abstract [en]

    Salt marshes are complex systems comprising ephemerally flooded, vegetated platforms hydraulically fed by tidal creeks. Where drainage is poor, formation of saline-water ponds can occur. Within East Anglian (UK) salt marshes, two types of sediment chemistries can be found beneath these ponds; iron-rich sediment, which is characterized by high ferrous iron concentration in subsurface porewaters (up to 2 mM in the upper 30 cm); and sulfide-rich sediment, which is characterized by high porewater sulfide concentrations (up to 8 mM). We present 5 years of push-core sampling to explore the geochemistry of the porewater in these two types of sediment. We suggest that when organic carbon is present in quantities sufficient to exhaust the oxygen and iron content within pond sediments, conditions favor the presence of sulfide-rich sediments. In contrast, in pond sediments where oxygen is present, primarily through bioirrigation, reduced iron can be reoxidised and thus recycled for further reduction, favoring the perpetuation of iron-rich sedimentary conditions. We find these pond sediments can alter significantly over an annual timescale. We carried out a drone survey, with ground-truthed measurements, to explore the spatial distribution of geochemistry in these ponds. Our results suggest that a pond's proximity to a creek partially determines the pond subsurface geochemistry, with iron-rich ponds tending to be closer to large creeks than sulfide-rich ponds. We suggest differences in surface delivery of organic carbon, due to differences in the energy of the ebb flow, or the surface/subsurface delivery of iron may control the distribution. This could be amplified if tidal inundations flush ponds closer to creeks more frequently, removing carbon and flushing with oxygen. These results suggest that anthropogenic creation of drainage ditches could shift the distribution of iron- and sulfide-rich ponds and thus have an impact on nutrient, trace metal and carbon cycling in salt marsh ecosystems.

  • 73. Isaev, A. V.
    et al.
    Eremina, T. R.
    Ryabchenko, V. A.
    Savchuk, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. St. Petersburg State University, Russia.
    Model estimates of the impact of bioirrigation activity of Marenzelleria spp. on the Gulf of Finland ecosystem in a changing climate2017In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 171, p. 81-88Article in journal (Refereed)
    Abstract [en]

    Drastic changes have occurred in the Eastern Gulf of Finland ecosystem after recent invasion and establishment of polychaete Marenzelleria spp. Possible mechanisms of these changes are explored with the help of three-dimensional ecosystem model SPBEM. Relative significance of bioirrigation activity is studied by comparison of two climate change scenario simulations, which include or disregard Marenzelleria effects. The novel results obtained with this approach demonstrate that on a system level biogeochemical consequences of both implemented climate changes scenario and polychaete activity are equivalent to a weakening of vicious circle of the Baltic Sea eutrophication. The eutrophication-mitigating effects of the Marenzelleria invasion into the Eastern Gulf of Finland, revealed by the long-term field measurements, are explained by simulation-based considerations.

  • 74.
    Jakobsson, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Stranne, Christian
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Greenwood, Sarah L.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gustafsson, Bo
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Weidner, Elizabeth
    Stockholm University, Faculty of Science, Department of Geological Sciences. University of New Hampshire, USA.
    Bathymetric properties of the Baltic Sea2019In: Ocean Science, ISSN 1812-0784, E-ISSN 1812-0792, Vol. 15, no 4, p. 905-924Article in journal (Refereed)
    Abstract [en]

    Baltic Sea bathymetric properties are analysed here using the newly released digital bathymetric model (DBM) by the European Marine Observation and Data Network (EMODnet). The analyses include hypsometry, volume, descriptive depth statistics, and kilometre-scale seafloor ruggedness, i.e. terrain heterogeneity, for the Baltic Sea as a whole as well as for 17 sub-basins defined by the Baltic Marine Environment Protection Commission (HELCOM). We compare the new EMODnet DBM with IOWTOPO the previously most widely used DBM of the Baltic Se aproduced by the Leibniz-Institut fur Ostseeforschung Warnemiinde (IOW), which has served as the primary gridded bathymetric resource in physical and environmental studies for nearly two decades. The area of deep water exchange between the Bothnian Sea and the Northern Baltic Proper across the Aland Sea is specifically analysed in terms of depths and locations of critical bathymetric sills. The EMODnet DBM provides a bathymetric sill depth of 88 m at the northern side of the Aland Sea and 60 m at the southern side, differing from previously identified sill depths of 100 and 70 m, respectively. High-resolution multibeam bathymetry acquired from this deep water exchange path, where vigorous bottom currents interacted with the seafloor, allows us to assess what presently available DBMs are missing in terms of physical characterization of the seafloor. Our study highlights the need for continued work towards complete high-resolution mapping of the Baltic Sea seafloor.

  • 75. Jansson, Torbjörn
    et al.
    Andersen, Hans Estrup
    Hasler, Berit
    Höglind, Lisa
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Can investments in manure technology reduce nutrient leakage to the Baltic Sea?2019In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 48, no 11, p. 1264-1277Article in journal (Refereed)
    Abstract [en]

    In this study, quantitative models of the agricultural sector and nutrient transport and cycling are used to analyse the impacts in the Baltic Sea of replacing the current Greening measures of the EU's Common Agricultural Policy with a package of investments in manure handling. The investments aim at improving nutrient utilization and reducing nitrogen leaching, based on the assumption that lagging farms and regions can catch up with observed good practice. Our results indicate that such investments could reduce nitrogen surpluses in agriculture by 18% and nitrogen concentrations in the Baltic Sea by 1 to 9% depending on the basin. The Greening measures, in contrast, are found to actually increase nitrogen leaching.

  • 76. Jansson, Torbjörn
    et al.
    Estrup Andersen, Hans
    Hasler, Berit
    Höglind, Lisa
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Can investments in manure technology reduce nutrient leakage to the Baltic Sea?2019In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 48, no 11Article in journal (Refereed)
    Abstract [en]

    In this study, quantitative models of the agricultural sector and nutrient transport and cycling are used to analyse the impacts in the Baltic Sea of replacing the current Greening measures of the EU's Common Agricultural Policy with a package of investments in manure handling. The investments aim at improving nutrient utilization and reducing nitrogen leaching, based on the assumption that lagging farms and regions can catch up with observed good practice. Our results indicate that such investments could reduce nitrogen surpluses in agriculture by 18% and nitrogen concentrations in the Baltic Sea by 1 to 9% depending on the basin. The Greening measures, in contrast, are found to actually increase nitrogen leaching.

  • 77.
    Jaramillo, Fernando
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Stockholm University, Faculty of Science, Stockholm Resilience Centre. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Desormeaux, Amanda
    Hedlund, Johanna
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Jawitz, James W.
    Clerici, Nicola
    Piemontese, Luigi
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Alexandra Rodríguez-Rodriguez, Jenny
    Adolfo Anaya, Jesús
    Blanco-Libreros, Juan F.
    Borja, Sonia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Celi, Jorge
    Chalov, Sergey
    Chun, Kwok Pan
    Cresso, Matilda
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Dessu, Shimelis Behailu
    Di Baldassarre, Giuliano
    Downing, Andrea
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Espinosa, Luisa
    Ghajarnia, Navid
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Girard, Pierre
    Gutiérrez, Álvaro G.
    Hansen, Amy
    Hu, Tengfei
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kalantary, Zahra
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Labbaci, Adnane
    Licero-Villanueva, Lucia
    Livsey, John
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Machotka, Ewa
    Stockholm University, Faculty of Humanities, Department of Asian, Middle Eastern and Turkish Studies.
    McCurley, Kathryn
    Palomino-Ángel, Sebastián
    Pietron, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Price, René
    Ramchunder, Sorain J.
    Ricaurte-Villota, Constanza
    Ricaurte, Luisa Fernanda
    Dahir, Lula
    Rodríguez, Erasmo
    Salgado, Jorge
    Sannel, A. Britta K.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Carolina Santos, Ana
    Seifollahi-Aghmiuni, Samaneh
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Sjöberg, Ylva
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Sun, Lian
    Stockholm University, Faculty of Science, Department of Physical Geography. Beijing Normal University, China.
    Thorslund, Josefin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Vigouroux, Guillaume
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Wang-Erlandsson, Lan
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Xu, Diandian
    Stockholm University, Faculty of Science, Department of Physical Geography. Hohai University, China.
    Zamora, David
    Ziegler, Alan D.
    Åhlén, Imenne
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Priorities and Interactions of Sustainable Development Goals (SDGs) with Focus on Wetlands2019In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 11, no 3, article id 619Article in journal (Refereed)
    Abstract [en]

    Wetlands are often vital physical and social components of a country's natural capital, as well as providers of ecosystem services to local and national communities. We performed a network analysis to prioritize Sustainable Development Goal (SDG) targets for sustainable development in iconic wetlands and wetlandscapes around the world. The analysis was based on the information and perceptions on 45 wetlandscapes worldwide by 49 wetland researchers of the Global Wetland Ecohydrological Network (GWEN). We identified three 2030 Agenda targets of high priority across the wetlandscapes needed to achieve sustainable development: Target 6.3-Improve water quality; 2.4-Sustainable food production; and 12.2-Sustainable management of resources. Moreover, we found specific feedback mechanisms and synergies between SDG targets in the context of wetlands. The most consistent reinforcing interactions were the influence of Target 12.2 on 8.4-Efficient resource consumption; and that of Target 6.3 on 12.2. The wetlandscapes could be differentiated in four bundles of distinctive priority SDG-targets: Basic human needs, Sustainable tourism, Environmental impact in urban wetlands, and Improving and conserving environment. In general, we find that the SDG groups, targets, and interactions stress that maintaining good water quality and a wise use of wetlandscapes are vital to attaining sustainable development within these sensitive ecosystems.

  • 78. Jilbert, Tom
    et al.
    Conley, Daniel J.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Funkey, Carolina P.
    Slomp, Caroline P.
    Glacio-isostatic control on hypoxia in a high-latitude shelf basin2015In: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 43, no 5, p. 427-430Article in journal (Refereed)
    Abstract [en]

    In high-latitude continental shelf environments, late Pleistocene glacial overdeepening and early Holocene eustatic sea-level rise combined to create restricted marine basins with a high vulnerability to oxygen depletion. Here we show that ongoing glacio-isostatic rebound during the Holocene may have played an important role in determining the distribution of past hypoxia in these environments by controlling the physical exchange of water masses and the distribution of large-scale phosphorus (P) sinks. We focus on the Baltic Sea, where sediment records from a large, presently oxic sub-basin show evidence for intense hypoxia and cyanobacteria blooms during the Holocene Thermal Maximum. Using paleobathymetric modeling, we show that this period was characterized by enhanced deep-water exchange, allowing widespread phosphorus regeneration. Intra-basin sills then shoaled over a period of several thousand years, enhancing P burial in one of the sub-basins. Together with climate forcing, this may have caused the termination of hypoxia throughout the Baltic Sea. Similar rearrangements of physical and chemical processes likely occurred in response to glacio-isostatic rebound in other high-latitude shelf basins during the Holocene.

  • 79.
    Joakim, Hansen
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Undervattensvegetation på mjukbottnar i Blekinge läns kustvatten: En sammanställning och analys av inventeringar utförda 2001–20082010Report (Other academic)
    Abstract [sv]

    I den här studien sammanställdes inventeringar av vattenväxter utförda mellan år 2001 – 2008 i 25 vattenförekomster i Blekinge skärgård. Syftet med studien var att analysera rumsliga variationer i växtartsammansättning på mjukbotten, samt undersöka vilka arter som är representativa respektive unika för en viss typ av miljö. Vidare syftade projektet till att undersöka hur väl variationen i artsammansättning kan förklaras av skillnader i vågexponering, djup och närsaltsbelastning. Resultaten visade att artsammansättningen på mjukbotten i Blekinge skärgård är relativt lika mellan flertalet vattenförekomster. Endast några få vattenförekomster hade en artsammansättning markant skild från de övriga. De vanligaste arterna i det sammanställda datamaterialet var borstnate Potamogeton pectinatus, lösliggande blåstång Fucus vesiculosus, natingar Ruppia spp., ålgräs Zostera marina, axslinga Myriophyllum spicatum samt trådformiga alger. Dessa arter påträffades i flertalet av vattenförekomsterna. Ovanliga arter var rödsträfse Chara tomentosa, murkelalg Leathesia difformis, hjulmöja Ranunculus circinatus, slangalger Vaucheriaceae, korsandmat Lemna trisulca och havsrufse Tolypella nidifica. Dessa arter påträffades endast i enstaka vattenförekomster. Artsammansättningen i vågexponerade djupa miljöer skilde sig signifikant från artsammansättningen i vågexponerade grunda och i skyddade grunda miljöer. Vidare skilde artsammansättningen signifikant mellan vattenförekomster med hög närsaltsbelastning och vattenförekomster med lägre närsaltbelastning. Vattenförekomster med hög närsaltbelastning hade högre täckningsgrad av trådformiga alger, natingar Ruppia spp., ålnate Potamogeton perfoliatus och havsnajas Najas marina än vattenförekomster med lägre närsaltsbelastning. Omvänt hade vattenförekomster med lägre närsaltsbelastning högre täckningsgrad av blåstång Fucus vesiculosus, ålgräs Zostera marina, borstnate Potamogeton pectinatus och sudare Chorda filum. Skillnader i koncentration av totalfosfor och totalkväve kunde förklara en förhållandevis stor del av variationen i artsammansättning mellan vattenförekomsterna. Skillnader i närsaltsbelastning samvarierade med skärgårdsgradienten, exempelvis fanns entydlig samvariation mellan koncentrationen totalkväve och salthalt. Detta gör det svårt att urskilja effekter av enskilda miljöfaktorer på artsammansättningen.

  • 80.
    Joakim P., Hansen
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Effects of shore-level displacement on the ecology of Baltic Sea bays2013Report (Other academic)
    Abstract [en]

    This report presents the up to date understanding of changes in ecological structure of small Baltic Sea bays following shore-level displacement and isolation of bays from the sea. It was producedas a part of the biosphere research programme, which has a strong emphasis on the characterization of properties and processes affecting the fate of potentially released radionuclides from the suggested repository of nuclear waste in the bedrock of the Forsmark area. The report has a focus on ecology and gives a description of input data, methodology and results on changes in flora and fauna communities, as well as some abiotic factors, with topographic isolation of bays from the sea. It is intended to describe the properties and conditions at the Forsmark site and to give information essential for demonstrating site specific understanding of processes and properties linked to a sea-to-lake succession. Long-term landscape development in the Forsmark area is dependent on two main and partly interdependent factors; shore-level displacement and climate variations. These two factors in combination strongly affect a number of processes, which in turn influence the development of ecosystems. Some examples of such processes are erosion and sedimentation, primary production and decomposition of organic matter. In this work focus has been to report changes in the structure and biomass of flora and fauna communities, which affect primary production, and influence the processes of decomposition of organic matter and sedimentation. A section of the study also deals with the biological processes of primary production, autotrophic carbon uptake and influence of allochtonous energy. The study is part of a description of the Forsmark ecosystem succession during a glacial cycle, which is one of the main objectives of the biosphere modelling at the Swedish Nuclear Fuel and Waste Management Company (SKB). The biomass of macrofauna was found to decrease with increasing isolation of bays. The changes in the macrofauna community also reflected the animals ability to re-colonize an unstable habitat, where slow colonizers with passively dispersed larvae were almost absent from the most isolated bays. Fast colonizers – particularly the ones with flying adults (insects) – were however found inhigher proportions in isolated bays. Contrary to the macrofauna and flora, the zooplankton and juvenile fish increased in biomass with increasing bay isolation. This study describes a significant change in ecological properties of Baltic Sea bays with shore-level displacement. This change affects ecosystem processes which may be of importance for the fate of potentially released radionuclides to the biosphere.

  • 81. Joensuu, M.
    et al.
    Pilditch, C. A.
    Harris, R.
    Hietanen, S.
    Pettersson, H.
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Sediment properties, biota, and local habitat structure explain variation in the erodibility of coastal sediments2018In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 63, no 1, p. 173-186Article in journal (Refereed)
    Abstract [en]

    Sediment resuspension is a frequent phenomenon in coastal areas and a key driver for many ecosystem functions. Sediment resuspension is often linked to biological and anthropogenic activities, which in combination with hydrodynamic forcing initiate sediment erosion and resuspension, if the erosion threshold (tau(c)) is exceeded. Despite its importance to ecosystem functions very few studies have provided measurements on natural assemblages for subtidal sediments. The aim of this study was to determinate key environmental variables regulating sediment resuspension potential across a sedimentary gradient in a subtidal coastal environment. In order to explore this, we sampled 16 sites encompassing a wide variety in environmental variables (e.g., grain size distribution, macrofaunal communities, vegetation) in the Gulf of Finland, Baltic Sea. A core-based erosion device (EROMES) was used to determine sediment resuspension potential measures of erosion threshold, erosion rate (ER), and erosion constant (m(e)). Based on abiotic and biotic properties sampled, sediments diverged into two distinct groups; cohesive (muddy) and noncohesive (sandy) sediments. Results showed that abiotic sediment properties explained 38-53% and 15-36% of the total variation in resuspension potential measures in muddy and sandy sediments, respectively. In cumulative models, biota accounted for 12-26% and 6-24% to the total variation in muddy and sandy sediments, respectively. Sediment erodibility and resuspension potential of natural sediments is highly variable from local habitats to a larger seascape scale. Our results underline the importance of biota to resuspension potential measures in spatially variable environments.

  • 82. Jones, Holly P.
    et al.
    Jones, Peter C.
    Barbier, Edward B.
    Blackburn, Ryan C.
    Benayas, Jose M. Rey
    Holl, Karen D.
    McCrackin, Michelle
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Meli, Paula
    Montoya, Daniel
    Mateos, David Moreno
    Restoration and repair of Earth's damaged ecosystems2018In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 285, no 1873, article id 20172577Article in journal (Refereed)
    Abstract [en]

    Given that few ecosystems on the Earth have been unaffected by humans, restoring them holds great promise for stemming the biodiversity crisis and ensuring ecosystem services are provided to humanity. Nonetheless, few studies have documented the recovery of ecosystems globally or the rates at which ecosystems recover. Even fewer have addressed the added benefit of actively restoring ecosystems versus allowing them to recover without human intervention following the cessation of a disturbance. Our meta-analysis of 400 studies worldwide that document recovery from large-scale disturbances, such as oil spills, agriculture and logging, suggests that though ecosystems are progressing towards recovery following disturbances, they rarely recover completely. This result reinforces conservation of intact ecosystems as a key strategy for protecting biodiversity. Recovery rates slowed down with time since the disturbance ended, suggesting that the final stages of recovery are the most challenging to achieve. Active restoration did not result in faster or more complete recovery than simply ending the disturbances ecosystems face. Our results on the added benefit of restoration must be interpreted cautiously, because few studies directly compared different restoration actions in the same location after the same disturbance. The lack of consistent value added of active restoration following disturbance suggests that passive recovery should be considered as a first option; if recovery is slow, then active restoration actions should be better tailored to overcome specific obstacles to recovery and achieve restoration goals. We call for a more strategic investment of limited restoration resources into innovative collaborative efforts between scientists, local communities and practitioners to develop restoration techniques that are ecologically, economically and socially viable.

  • 83.
    Juston, John
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Data-driven Nutrient-landscape Relationships across Regions and Scales2016In: Water environment research, ISSN 1061-4303, E-ISSN 1554-7531, Vol. 88, no 11, p. 2023-2031Article in journal (Refereed)
    Abstract [en]

    Previous studies have identified relationships between nutrient exports and upstream conditions, but have often disconnected interpretations from hydrological flows and changes. Here, we investigated basic relationships between largely flow-independent nutrient concentrations and two key descriptors of upstream landscape and human activity: population density and arable land cover. Consistent data were gathered from previous studies of the Baltic Sea and Mississippi River basins. These data span wide ranges of subcatchment scales, hydroclimatic conditions, and landscape characteristics. In general, investigated relationships were stronger in the Baltic than in the Mississippi region and stronger for total nitrogen (TN) than total phosphorous (TP) concentrations. However, TN concentration was both highly and consistently correlated to arable land cover across all scales and both regions. These findings support that TN export from catchments is dictated principally by retention and slow release from subsurface legacy stores while export TP concentrations appear to be dictated more by faster particulate surface transport.

  • 84. Kahru, Mati
    et al.
    Elmgren, Ragnar
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Di Lorenzo, Emanuele
    Savchuck, Oleg
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Unexplained interannual oscillations of cyanobacterial blooms in the Baltic Sea2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 6365Article in journal (Refereed)
    Abstract [en]

    Population oscillations in multi-species or even single species systems are well-known but have rarely been detected at the lower trophic levels in marine systems. Nitrogen fixing cyanobacteria are a major component of the Baltic Sea ecosystem and sometimes form huge surface accumulations covering most of the sea surface. By analysing a satellite-derived 39-year (1979–2017) data archive of surface cyanobacteria concentrations we have found evidence of strikingly regular interannual oscillations in cyanobacteria concentrations in the northern Baltic Sea. These oscillations have a period of ~3 years with a high-concentration year generally followed by one or two low-concentration years. Changes in abiotic factors known to influence the growth and survival of cyanobacteria could not provide an explanation for the oscillations. We therefore assume that these oscillations are intrinsic to the marine system, caused by an unknown, probably mainly biological mechanism that may be triggered by a combination of environmental factors. Interactions between different life cycle stages of cyanobacteria as well as between predator-prey or host-parasite are possible candidates for causing the oscillations.

  • 85. Kahru, Mati
    et al.
    Elmgren, Ragnar
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Savchuk, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Changing seasonality of the Baltic Sea2016In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 13, no 4, p. 1009-1018Article in journal (Refereed)
    Abstract [en]

    Changes in the phenology of physical and ecological variables associated with climate change are likely to have significant effect on many aspects of the Baltic ecosystem. We apply a set of phenological indicators to multiple environmental variables measured by satellite sensors for 17-36 years to detect possible changes in the seasonality in the Baltic Sea environment. We detect significant temporal changes, such as earlier start of the summer season and prolongation of the productive season, in several variables ranging from basic physical drivers to ecological status indicators. While increasing trends in the absolute values of variables like sea-surface temperature (SST), diffuse attenuation of light (Ked490) and satellite-detected chlorophyll concentration (CHL) are detectable, the corresponding changes in their seasonal cycles are more dramatic. For example, the cumulative sum of 30 000 W m(-2) of surface incoming short-wave irradiance (SIS) was reached 23 days earlier in 2014 compared to the beginning of the time series in 1983. The period of the year with SST of at least 17 degrees C has almost doubled (from 29 days in 1982 to 56 days in 2014), and the period with Ked490 over 0.4 m(1) has increased from about 60 days in 1998 to 240 days in 2013 -i.e., quadrupled. The period with satellite-estimated CHL of at least 3 mg m(-3) has doubled from approximately 110 days in 1998 to 220 days in 2013. While the timing of both the phytoplankton spring and summer blooms have advanced, the annual CHL maximum that in the 1980s corresponded to the spring diatom bloom in May has now shifted to the summer cyanobacteria bloom in July.

  • 86. Kauppi, L.
    et al.
    Bernard, G.
    Bastrop, R.
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Norkko, J.
    Increasing densities of an invasive polychaete enhance bioturbation with variable effects on solute fluxes2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 7619Article in journal (Refereed)
    Abstract [en]

    Bioturbation is a key process affecting nutrient cycling in soft sediments. The invasive polychaete genus Marenzelleria spp. has established successfully throughout the Baltic Sea increasing species and functional diversity with possible density-dependent effects on bioturbation and associated solute fluxes. We tested the effects of increasing density of M. arctia, M. viridis and M. neglecta on bioturbation and solute fluxes in a laboratory experiment. Benthic communities in intact sediment cores were manipulated by adding increasing numbers of Marenzelleria spp. The results showed that Marenzelleria spp. in general enhanced all bioturbation metrics, but the effects on solute fluxes varied depending on the solute, on the density and species identity of Marenzelleria, and on the species and functional composition of the surrounding community. M. viridis and M. neglecta were more important in predicting variation in phosphate and silicate fluxes, whereas M. arctia had a larger effect on nitrogen cycling. The complex direct and indirect pathways indicate the importance of considering the whole community and not just species in isolation in the experimental studies. Including these interactions provides a way forward regarding our understanding of the complex ecosystem effects of invasive species.

  • 87. Kauppi, L.
    et al.
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Norkko, J.
    Seasonal population dynamics of the invasive polychaete genus Marenzelleria spp. in contrasting soft-sediment habitats2018In: Journal of Sea Research, ISSN 1385-1101, E-ISSN 1873-1414, Vol. 131, p. 46-60Article in journal (Refereed)
    Abstract [en]

    Three species of the invasive polychaete genus Marenzelleria are among the dominant benthic taxa in many, especially deeper, areas in the Baltic Sea. The population dynamics of the polychaetes in the Baltic are, however, still largely unknown. We conducted monthly samplings of the benthic communities and environmental parameters at five sites with differing depths and sediment characteristics in the northern Baltic Sea (59 degrees 50.896', 23 degrees 15.092') to study the population dynamics, productivity and growth of Marenzelleria spp. from April 2013 to June 2014. The species of Marenzelleria occurring at the study sites were identified by genetic analyses. At the deepest site (33 m) only M. arctia was present, while all three species were found at the shallower, muddy sites (up to 20 m depth). At the shallow (6 m) sandy site only M. viridis and M. neglecta occurred. The sites differed in the seasonal dynamics of the Marenzelleria spp. population, reflecting the different species identities. The muddy sites up to 20 m depth showed clear seasonal dynamics, with the population practically disappearing by winter, whereas more stable populations occurred at the deepest site and at the sandy site. The highest density, biomass and production were observed at the 20 m deep, organic-rich muddy site where all three species recruited. The seasonally very high densities are likely to have important consequences for organic matter processing, and species interactions at these sites. The observed high productivity of the populations has possibly facilitated their establishment, and considerably increased secondary production in especially the deeper areas.

  • 88. Kauppi, L.
    et al.
    Norkko, J.
    Ikonen, J.
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Seasonal variability in ecosystem functions: quantifying the contribution of invasive species to nutrient cycling in coastal ecosystems2017In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 572, p. 193-207Article in journal (Refereed)
    Abstract [en]

    Benthic ecosystems at temperate and high latitudes experience marked seasonal variation in the environmental factors affecting nutrient remineralization processes both directly and indirectly through their effects on the benthic communities. The invasive polychaete genus Marenzelleria represents new functionality in Baltic Sea sediments through its deep burrowing and extensive gallery formation, thus possibly greatly affecting benthic oxygen and nutrient fluxes. We assessed the seasonal contribution of Marenzelleria spp. to fluxes of solutes in monthly field measurements at 2 sites, 10 and 33 m deep, in the northern Baltic Proper over 1 yr. In general, the fluxes of inorganic nutrients and oxygen were higher during summer than during winter, and the seasonal variation was more pronounced at the deeper, more biologically active site. By using variation partitioning, we were able to demonstrate that Marenzelleria and other macrofauna could account for up to 92% of the variation in the fluxes depending on the site and season. Fauna was the most important in predicting the fluxes in spring when the sediment organic content and the abundance of juvenile Marenzelleria spp. were highest, while during e.g. winter, the influence of Marenzelleria spp., even though abundant, on solute fluxes was negligible. The results from this study have implications for management, and, importantly, for the modelling of nutrient budgets often based on values from studies conducted during the summer period only, thus possibly greatly miscalculating the annual nutrient fluxes.

  • 89.
    Kautsky, Lena
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Qvarfordt, Susanne
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Schagerström, Ellen
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Fucus vesiculosus adapted to a life in the Baltic Sea: impacts on recruitment, growth, re-establishment and restoration2019In: Botanica Marina, ISSN 0006-8055, E-ISSN 1437-4323, Vol. 62, no 1, p. 17-30Article in journal (Refereed)
    Abstract [en]

    Fucus vesiculosus is common both on the tidal coasts of the North Atlantic and in the Baltic Sea, where it has adapted to low salinity and nontidal conditions over the last 7000 years. During the late 1970s and early 1980s, extensive declines of F. vesiculosus populations were reported in the Baltic Proper, mainly attributed to high nutrient loads. During the past 30-40 years, considerable efforts have been made to reduce nutrient runoff to coastal areas but few successful initiatives to restore F. vesiculosus populations have been performed. In this paper, we present how substratum manipulation, i.e. clean rocky surfaces, brushing rocks, Hildenbrandia rubra cover and different filamentous algae, as well as different algal exudates, affect the recruitment and survival of juvenile F.vesiculosus. Further, we show through a 5-year field experiment that it will take at least 4-5 years to reach reproductive age for F. vesiculosus in the Baltic Sea. We also present transplantation studies from two different areas, showing that epiphytic load, light, grazing and type of substratum are some of the factors that need to be taken into consideration in order to achieve successful restoration of F. vesiculosus.

  • 90. Korth, F.
    et al.
    Deutsch, Barbara
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Frey, C.
    Moros, C.
    Voss, M.
    Nitrate source identification in the Baltic Sea using its isotopic ratios in combination with a Bayesian isotope mixing model2014In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, no 17, p. 4913-4924Article in journal (Refereed)
    Abstract [en]

    Nitrate (NO3-) is the major nutrient responsible for coastal eutrophication worldwide and its production is related to intensive food production and fossil-fuel combustion. In the Baltic Sea NO3- inputs have increased 4-fold over recent decades and now remain constantly high. NO3- source identification is therefore an important consideration in environmental management strategies. In this study focusing on the Baltic Sea, we used a method to estimate the proportional contributions of NO3- from atmospheric deposition, N-2 fixation, and runoff from pristine soils as well as from agricultural land. Our approach combines data on the dual isotopes of NO3- (delta N-15-NO3- and delta O-18-NO3-) in winter surface waters with a Bayesian isotope mixing model (Stable Isotope Analysis in R, SIAR). Based on data gathered from 47 sampling locations over the entire Baltic Sea, the majority of the NO3- in the southern Baltic was shown to derive from runoff from agricultural land (33-100 %), whereas in the northern Baltic, i.e. the Gulf of Bothnia, NO3- originates from nitrification in pristine soils (34-100 %). Atmospheric deposition accounts for only a small percentage of NO3- levels in the Baltic Sea, except for contributions from northern rivers, where the levels of atmospheric NO3- are higher. An additional important source in the central Baltic Sea is N-2 fixation by diazotrophs, which contributes 49-65% of the overall NO3- pool at this site. The results obtained with this method are in good agreement with source estimates based upon delta N-15 values in sediments and a three-dimensional ecosystem model, ERGOM. We suggest that this approach can be easily modified to determine NO3- sources in other marginal seas or larger near-coastal areas where NO3- is abundant in winter surface waters when fractionation processes are minor.

  • 91. Krogseth, Ingjerd S.
    et al.
    Undeman, Emma
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Evenset, Anita
    Christensen, Guttorm N.
    Whelan, Mick J.
    Breivik, Knut
    Warner, Nicholas A.
    Elucidating the Behavior of Cyclic Volatile Methylsiloxanes in a Subarctic Freshwater Food Web: A Modeled and Measured Approach2017In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 51, no 21, p. 12489-12497Article in journal (Refereed)
    Abstract [en]

    Cyclic volatile methylsiloxanes (cVMS) are used in personal care products and emitted to aquatic environments through wastewater effluents, and their bioaccumulation potential is debated. Here, a new bentho-pelagic version of the ACC-HUMAN model was evaluated for polychlorinated biphenyls (PCBs) and applied to cVMS in combination with measurements to explore their bioaccumulation behavior in a subarctic lake. Predictions agreed better with measured PCB concentrations in Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta) when the benthic link was included than in the pelagic-only model. Measured concentrations of decamethylcyclopentasiloxane (D5) were 60 +/- 1.2 (Chironomidae larvae), 107 +/- 4.5 (pea clams Pisidium sp.), 131 +/- 105 (three-spined sticklebacks: Gasterosteus aculeatus), 41 +/- 38 (char), and 9.9 +/- 5.9 (trout) ng g(-1) wet weight. Concentrations were lower for octamethylcyclotetrasiloxane (D4) and dodecamethylcyclohexasiloxane (D6), and none of the cVMS displayed trophic magnification. Predicted cVMS concentrations were lower than measured in benthos, but agreed well with measurements in fish. cVMS removal through ventilation was an important predicted loss mechanism for the benthic-feeding fish. Predictions were highly sensitive to the partition coefficient between organic carbon and water (K-OC) and its temperature dependence, as this controlled bioavailability for benthos (the main source of cVMS for fish).

  • 92.
    Larsson, Ulf
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Nyberg, Svante
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Zakrisson, Anna
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hajdu, Susanna
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Elmgren, Ragnar
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Walve, Jakob
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Rolff, Carl
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Baltic Sea phytoplankton: Long-term variability of major groups and primary production in spring and summer related to nutrients and temperatureManuscript (preprint) (Other academic)
  • 93. Lastra, Mariano
    et al.
    López, Jesús
    Rodil, Iván F.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Warming intensify CO2 flux and nutrient release from algal wrack subsidies on sandy beaches2018In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 24, no 8, p. 3766-3779Article in journal (Refereed)
    Abstract [en]

    Algal wrack subsidies underpin most of the food web structure of exposed sandy beaches and are responsible of important biogeochemical processes that link marine and terrestrial ecosystems. The response in decomposition of algal wrack deposits to global warming has not been studied in ocean-exposed sandy beaches to date. With this aim, passive open top chambers (OTCs) were used to increase soil temperature within the range predicted by the IPCC for western Europe (between 0.5 and 1.5 degrees C), following the hypothesis that the biogeochemical processing of macroalgal wrack subsidies would accelerate in response to temperature increase. The effect of temperature manipulation on three target substrates: fresh and aged macroalgae, and bare sand, was tested. Results indicated that a small warming (< 0.5 degrees C) affected the wrack decomposition process through traceable increases in soil respiration through CO2 flux, inorganic nutrients within the interstitial environment (N and P), sediment organic contents measured through the amount of proteins and microbial pool through the total soil DNA. The different responses of soil variables in the studied substrates indicated that the decomposition stage of stranded macroalgae influences the biogeochemical processing of organic matter in sandy beaches. Thus, CO2 fluxes, releases of organic and inorganic nutrients and microbial activity intensify in aged wrack deposits. Our results predict that expected global warming will increase the release of inorganic nutrients to the coastal ocean by 30% for the N (21 Gg/year) and 5.9% for P (14 Gg/year); that increase for the flow of C to the atmosphere as CO2 was estimated in 8.2% (523 Gg/year). This study confirms the key role of sandy beaches in recycling ocean-derived organic matter, highlighting their sensitivity to a changing scenario of global warming that predicts significant increases in temperature over the next few decades.

  • 94. Lehtoranta, Jouni
    et al.
    Savchuk, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Elken, Juri