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  • 1.
    Blenckner, Thorsten
    et al.
    Stockholm University, Stockholm Resilience Centre.
    Noges, Tiina
    Tranvik, Lars
    Pettersson, Kurt
    Naddafi, Rahmat
    Preface2011In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 660, no 1, p. 1-2Article in journal (Refereed)
  • 2.
    Das, Supriyo Kumar
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Routh, Joyanto
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Roychoudhury, Alakendra N.
    Val Klump, J.
    Ranjan, Rajesh Kumar
    Phosphorus dynamics in shallow eutrophic lakes: an example from Zeekoevlei, South Africa2009In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 619, p. 55-66Article in journal (Refereed)
    Abstract [en]

    Zeekoevlei is the largest freshwater lake in South Africa and has been suffering from hyper-eutrophic conditions since last few decades. We have used total P (TP), dissolved phosphate (PO4 (3-)), organic P (OP), calcium (Ca) and iron (Fe) bound P fractions to investigate the relevant physical, chemical and biological processes responsible for sedimentation and retention of P and to study phosphorus (P) dynamics in this shallow lake. In addition, redox proxies (V/Cr and Th/U ratios) are used to study the prevailing redox conditions in sediments. Adsorption by CaCO3 and planktonic assimilation of P are found to control P sedimentation in Zeekoevlei. Low concentration of the labile OP fraction in surface sediments restricts the release of P by bacterial remineralisation. Low molar Ca/P and Fe/P ratios indicate low P retention capacity of sediments, and P is most likely released by desorption from wind-induced resuspended sediments and mixing of pore water with the overlying water column.

  • 3. Euclide, Peter T.
    et al.
    Hansson, Sture
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Stockwell, Jason D.
    Partial diel vertical migration in an omnivorous macroinvertebrate, Mysis diluviana2017In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 787, no 1, p. 387-396Article in journal (Refereed)
    Abstract [en]

    Partial migration, whereby only a portion of a population migrates, has just recently received attention in aquatic systems. Partial diel vertical migration (DVM) has received even less attention but could significantly influence our understanding of trophic interactions and nutrient movement in open water systems. Recent work in the Baltic Sea shows differences in isotope composition between benthic and pelagic Mysis salemaai sampled at night, suggesting that partial DVM may be fixed at the individual level. Historic observations of North American M. diluviana suggest partial DVMin this species, but this behavior has largely been ignored in the literature. We used length, occurrence of gravid females, and body delta C-13, delta N-15, delta S-34, and C:N ratio as markers to test for differences among adult M. diluviana collected from benthic and pelagic habitats at night in Lake Champlain, USA. We found differences in body length and occurrence of gravid females between pelagic- and benthic-caught M. diluviana and differences in C: N between pelagic-and benthic-caught non-gravid individuals, consistent with life stage and body condition hypotheses for partial migration. Partial DVM of M. diluviana could have significant impacts on population assessments which could bias food web models used in basic research and management.

  • 4.
    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.

  • 5.
    Kratzer, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Tett, Paul
    Using bio-optics to investigate the extent of coastal waters: A Swedish case study2009In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 629, no 1, p. 169-186Article in journal (Refereed)
    Abstract [en]

    In order to develop an optical model to map the extent of coastal waters, the authors analyzed variations in bio-optical constituents and submarine optical properties along a transect from the nutrient-enriched coastal bay, Himmerfjärden, out into the open Baltic Sea. The model is a simple implementation of the “ecosystem approach,” because the optical constituents are proxies for important components of ecosystem state. Yellow substance or colored dissolved organic matter (CDOM) is often a marker for terrestrial freshwater or decay processes in the littoral zone. Phytoplankton pigments, especially chlorophyll a, are used as a proxy for phytoplankton biomass that may be stimulated by fluvial or coastal inputs of anthropogenic nutrients. Suspended particulate matter (SPM) is placed in suspension by tidal or wind-wave stirring of shallow seabeds, and is therefore an indicator for physical forcing. It is the thesis of this article that such constituents, and the optical properties that they control, can be used to provide an ecological definition of the extent of the coastal zone. The spatial distribution of the observations was analyzed using a steady-state model that assumes diffusional transport of bio-optical variables along an axis perpendicular to the coast. According to the model, the resulting distribution along this axis can be described as a low-order polynomial (of order 1–3) when moving from a “source” associated with land to the open-sea “sink.” Order 1 implies conservative mixing, and the higher orders imply significant biological or chemical processes within the gradient. The analysis of the transect data confirmed that the trend of each optical component could be described well using a low-order polynomial. Multiple regression analysis was then used to weigh the contribution of each optical component to the spectral attenuation coefficient K d(490) along the transect. The results showed that in this Swedish Baltic case study, the inorganic fraction of the SPM may be used to distinguish between coastal and open-sea waters, as it showed a clear break between coastal and open-sea waters. Alternative models may be needed for coastal waters in which fronts interrupt the continuity of mixing.

  • 6. Kruitbos, Laura M.
    et al.
    Tetzlaff, Doerthe
    Soulsby, Chris
    Buttle, Jim
    Carey, Sean K.
    Laudon, Hjalmar
    McDonnell, Jeffrey J.
    McGuire, Kevin
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Cunjak, Richard
    Shanley, Jamie
    Hydroclimatic and hydrochemical controls on Plecoptera diversity and distribution in northern freshwater ecosystems2012In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 693, no 1, p. 39-53Article in journal (Refereed)
    Abstract [en]

    Freshwater ecosystems in the mid- to upper-latitudes of the northern hemisphere are particularly vulnerable to the impact of climate change as slight changes in air temperature can alter the form, timing, and magnitude of precipitation and consequent influence of snowmelt on streamflow dynamics. Here, we examine the effects of hydro-climate, flow regime, and hydrochemistry on Plecoptera (stonefly) alpha (alpha) diversity and distribution in northern freshwater ecosystems. We characterized the hydroclimatic regime of seven catchments spanning a climatic gradient across the northern temperate region and compared them with estimates of Plecoptera genera richness. By a space-for-time substitution, we assessed how warmer temperatures and altered flow regimes may influence Plecoptera alpha diversity and composition at the genus level. Our results show wide hydroclimatic variability among sites, including differences in temporal streamflow dynamics and temperature response. Principal component analysis showed that Plecoptera genera richness was positively correlated with catchment relief (m), mean and median annual air temperature (A degrees C), and streamflow. These results provide a preliminary insight into how hydroclimatic change, particularly in terms of increased air temperature and altered streamflow regimes, may create future conditions more favorable to some Plecopteras in northern catchments.

  • 7.
    Kånneby, Tobias
    et al.
    The Swedish Museum of Natural History .
    Todaro, M. Antonio
    Jondelius, Ulf
    The Swedish Museum of Natural History.
    A Phylogenetic approach to species delimitation in freshwater Gastrotricha from Sweden2012In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 683, no 1, p. 185-202Article in journal (Refereed)
    Abstract [en]

    Gastrotricha is a cosmopolitan group of aquatic invertebrates. To date approximately 765 species have been described. This study is the first to deal with species delimitation and cryptic species of freshwater Gastrotricha. Three commonly encountered species, Heterolepidoderma ocellatum, Lepidochaetus zelinkai and Lepidodermella squamata, are investigated for cryptic speciation. Most of the material is based on Swedish specimens but closely related species from other parts of the world are also included. Taxonomic revisions are supported by phylogenies based on 18S rRNA, 28S rRNA and COI mtDNA of freshwater Chaetonotidae from several genera and inferred from Bayesian and maximum likelihood approaches. Heterolepidoderma ocellatum f. sphagnophilum is raised to species level, becoming H. acidophilum n. sp. Moreover, genetic data based on COI indicates high variation between two morphologically very similar groups of Lepidodermella squamata. The extent of cryptic speciation in L. zelinkai appears low. Based on the phylogenetic hypothesis presented in this paper the new species, Lepidodermella intermedia n. sp., from northernSweden is also described. The phylogenetic hypothesis generated show that Chaetonotidae is a non-monophyletic group.  

  • 8. Lund-Hansen, Lars Chresten
    et al.
    Nielsen, Jens Munk
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bluthgen, Jonas
    Hai, Doan Nhu
    Nielsen, Morten Holtegaard
    Lam, Nguyen Ngoc
    Estuarine morphometry governs optically active substances, K-d(PAR) and beam attenuation: assessments from a tropical ria and a temperate coastal plain estuary2013In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 711, no 1, p. 19-30Article in journal (Refereed)
    Abstract [en]

    Data on optical properties such as diffuse attenuation coefficient K (d)(PAR), beam attenuation coefficient (c (p)) and the optically active constituents (OACs) CDOM, Chl-a and suspended particulate matter were obtained in a Danish temperate coastal plain estuary (56A degrees N) and a Vietnamese tropical ria (12A degrees N) at high discharges. The major difference was the spatial distribution of the optical properties against distance, best described by significant power functions in the ria, compared to significant linear functions in the coastal plain. It was hypothesized that estuarine morphometry could explain this spatial distribution. Partition and multiple regression analyses showed that Chl-a governed K (d)(PAR) and beam attenuation coefficient in both estuaries. Significant, high correlations were obtained by multiple regression analyses in the estimation of K (d)(PAR) and beam attenuation coefficients in the two estuaries using OACs as input parameters. It is concluded that there are no large differences in OAC concentrations between the two estuaries. The spatial distributions of OACs and optical properties were significantly different and governed by the estuary morphometry, i.e. a power distribution in the tropical ria and a linear function in the temperate coastal plain estuary, and applicable to similar estuary types.

  • 9. Naddafi, Rahmat
    et al.
    Blenckner, Thorsten
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Eklöv, Peter
    Pettersson, Kurt
    Physical and chemical properties determine zebra mussel invasion success in lakes2011In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 669, no 1, p. 227-236Article in journal (Refereed)
    Abstract [en]

    To address the question whether the abundance of an invasive species can be explained by physical and chemical properties of the invaded ecosystems, we gathered density data of invasive zebra mussels and the physical and chemical data of ecosystems they invaded. We assembled published data from 55 European and 13 North American lakes and developed a model for zebra mussel density using a generalized additive model (GAM) approach. Our model revealed that the joint effect of surface area, total phosphorus and calcium concentrations explained 62% of the variation in Dreissena density. Our study indicates that large and less productive North American lakes can support larger local populations of zebra mussels. Our results suggest that the proliferation of an exotic species in an area can partially be explained by physical and chemical properties of the recipient environment.

  • 10.
    Nordemar, Ingrid
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Lilliesköld Sjöö, Gustaf
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Mörk, Erik
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    McClanahan, Tim
    Effects of estimated herbivory on the reproductivepotential of four East African algal species – a mechanismbehind ecosystem shifts on coral reefs?2007In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 575, no 1, p. 57-68Article in journal (Refereed)
    Abstract [en]

    The aim of this field study was toinvestigate effects of estimated fish- and seaurchin herbivory on the reproductive potential offour species of macroalgae; Halimeda macroloba(Decasine), H. renschii (Hauck), Turbinaria ornata(Turner) and Padina boergesenii (Allender etKraft). Fish and sea urchin herbivory were calculatedbased on reported consumption rates fortheir biomass estimates. We hypothesized thatreduced herbivory would increase algal size andthe reproductive potential, which may promotealgal recruitment and be one of the drivingmechanisms behind algal shifts and persistent algae-dominated reefs. Algae were investigated infield sites where the estimated fish- and or seaurchin herbivory differed. Our results suggest thatalgal fecundity of T. ornata and P. boergesenii arepositively correlated to their size. Fecundity ofT. ornata was higher and individuals grew largerin areas where estimated fish herbivory was lower.The two species of Halimeda grew larger andhad higher fecundity in areas where estimatedsea urchin herbivory was lower. P. boergeseniiresponded ambiguously to patterns in herbivory.Due to species-specific responses to differentherbivores, it is difficult to generalize abouteffects of overfishing on algal fecundity.

  • 11.
    Savchuk, Oleg P.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Wulff, Fredrik
    Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Long-term modeling of large-scale nutrient cycles in the entire Baltic Sea2009In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 629, p. 209-224Article in journal (Refereed)
    Abstract [en]

    Management of eutrophication in marine ecosystems requires a good understanding of nutrient cycles at the appropriate spatial and temporal scales. Here, it is shown that the biogeochemical processes controlling large-scale eutrophication of the Baltic Sea can be described with a fairly aggregated model: simple as necessary Baltic long-term large scale (SANBALTS). This model simulates the dynamics of nitrogen, phosphorus, and silica driven by the external inputs, the major physical transports, and the internal biogeochemical fluxes within the seven major sub-basins. In a long-term hindcast (1970–2003), the model outputs reasonably matched observed concentrations and fluxes. The model is also tested in a scenario where nutrient inputs are reduced to levels that existed over 100 years ago. The simulated response of the Baltic Sea trophic state to this very large reduction is verified by a similar simulation made with a much more complex process-oriented model. Both models indicate that after initial, rather rapid changes the system goes into much slower evolution, and nutrient cycles would not become balanced even after 130 years.

  • 12.
    Savchuk, O.P.
    et al.
    Stockholm University, Stockholm Resilience Centre, Baltic Nest Institute.
    Eremina, T.R.
    Isaev, A.V.
    Neelov, I.A.
    Response of eutrophication in the eastern Gulf of Finland to nutrient load reduction scenarios.2009In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 629, p. 225-237Article in journal (Refereed)
  • 13.
    Sowersby, Will
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Monash University, Australia.
    Lehtonen, Topi K.
    Wong, Bob B. M.
    Temporal and sex-specific patterns of breeding territory defense in a color-polymorphic cichlid fish2017In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 791, no 1, p. 237-245Article in journal (Refereed)
    Abstract [en]

    In biparental species, the costs and benefits of parental investment can vary between the sexes and shift over time. However, such sex-specific and temporal changes in territory defense are not well understood. Here, we experimentally investigated parental investment in breeding territory defense in a feral population of the color-polymorphic, biparental cichlid fish, the red devil (Amphilophus labiatus). We presented either gold- or dark-colored conspecific intruder models (i.e., dummy models) to A. labiatus pairs at three key stages during the breeding cycle (i.e., after pair formation, after eggs have been laid, and when fry were free-swimming). We found that males were more aggressive when the pair first formed, whereas females significantly increased their territory defense with time, and were most aggressive when fry were free-swimming. These results show that parental roles in territory defense can markedly shift over key stages of the breeding cycle. Our results demonstrate that parental behaviors may not only vary between the sexes, but can also shift dramatically over the course of the brood cycle.

  • 14. Tavera, Rosaluz
    et al.
    Diez, Beatriz
    Stockholm University, Faculty of Science, Department of Botany.
    Multifaceted approach for the analysis of the phototrophic microbial community in a freshwater recreational area of Xochimilco, M,xico2009In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 636, no 1, p. 353-368Article in journal (Refereed)
    Abstract [en]

    The freshwater microbial community in a recreational area of Xochimilco, M,xico was investigated and compared based on spatial (three different sites) and temporal (dry and rainy seasons) environmental variables. Many of the 16S- and 18S rRNA gene sequences recovered by DGGE fingerprinting analysis were related to phototrophic microbial phylotypes of known identity. Our genetic and morphological analysis indicated the ubiquitous presence of the microeukaryotic green algae Desmodesmus-Scenedesmus spp. and of the unicellular cyanobacteria Cyanobium spp. as the most representative populations in the samples. While 18S rRNA-DGGE fingerprinting analysis revealed a homogeneous community composition across sites and seasons, the 16S rRNA showed significant differences between localities and seasons. None of the cyanobacteria species with potential to produce toxins were identified across the investigated samples. Correlations between biotic and abiotic variables evidenced an important difference between the dry and the rainy season, with a greater consistency in data from the rainy season. According to Principal Component Analysis (PCA), a strong relation between inorganic nitrogen, species richness, and subaquatic irradiance determines environmental variability in Xochimilco. Complementary and relevant data in results obtained from microscopy, fingerprinting, and statistical analysis applied in ecology indicate that a multifaceted approach to the study of microbial communities is necessary to accomplish a comprehensive scientific framework and to generate proper management strategies.

  • 15.
    Winder, Monika
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Sommer, Ulrich
    Phytoplankton response to a changing climate2012In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 698, no 1, p. 5-16Article, review/survey (Refereed)
    Abstract [en]

    Phytoplankton are at the base of aquatic food webs and of global importance for ecosystem functioning and services. The dynamics of these photosynthetic cells are linked to annual fluctuations of temperature, water column mixing, resource availability, and consumption. Climate can modify these environmental factors and alter phytoplankton structure, seasonal dynamics, and taxonomic composition. Here, we review mechanistic links between climate alterations and factors limiting primary production, and highlight studies where climate change has had a clear impact on phytoplankton processes. Climate affects phytoplankton both directly through physiology and indirectly by changing water column stratification and resource availability, mainly nutrients and light, or intensified grazing by heterotrophs. These modifications affect various phytoplankton processes, and a widespread advance in phytoplankton spring bloom timing and changing bloom magnitudes have both been observed. Climate warming also affects phytoplankton species composition and size structure, and favors species traits best adapted to changing conditions associated with climate change. Shifts in phytoplankton can have far-reaching consequences for ecosystem structure and functioning. An improved understanding of the mechanistic links between climate and phytoplankton dynamics is important for predicting climate change impacts on aquatic ecosystems.

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