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  • 51. Mwandya, A. W.
    et al.
    Mgaya, Y. D.
    Öhman, M. C.
    Stockholm University, Faculty of Science, Department of Zoology.
    Bryceson, I.
    Gullström, M.
    Stockholm University, Faculty of Science, Department of Zoology.
    Distribution patterns of striped mullet Mugil cephalus in mangrove creeks, Zanzibar, Tanzania2010In: AFR J MAR SCI, ISSN 1814-232X, Vol. 32, no 1, p. 85-93Article in journal (Refereed)
    Abstract [en]

    Spatial and seasonal variations in density of striped mullet Mugil cephalus were investigated in four mangrove creeks in Zanzibar, Tanzania, during a one-year cycle. Fish were collected monthly in the lower, intermediate and upper reaches of each creek using a beach-seine net. All fish collected were juveniles between 2 and 16 cm standard length. The density of juvenile mullet differed significantly among the creeks, but the spatial patterns within them were consistent with higher densities upstream in three of the creeks. Generally, small mullet (2-10 cm) were more abundant in the upper reaches compared to the lower and intermediate reaches. Seasonal patterns were weak, although mullet densities were high during the period of heavy rains (March-May). Principal component analysis showed that a muddy substrate with microphytobenthos was positively correlated with high mullet densities, although site-specific variables such as shallow water depth and water clarity were also significantly correlated. Our findings suggest that the densities of juvenile striped mullet vary among sites and creeks in response to refuge availability from turbid, shallow water and the accessibility of food from benthic microalgae.

  • 52.
    Mwandya, Augustine
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Science, Department of Systems Ecology.
    Andersson, Mathias H.
    Stockholm University, Faculty of Science, Department of Zoology.
    Öhman, Marcus C.
    Stockholm University, Faculty of Science, Department of Zoology.
    Mgaya, Yunus D.
    Ian, Bryceson
    Spatial and seasonal variation of fish assemblages in mangrove creek systems in Zanzibar (Tanzania)2010In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 89, no 4, p. 277-286Article in journal (Refereed)
    Abstract [en]

    Spatial and seasonal variations of fish assemblage composition were studied in three non-estuarine mangrove creeks of Zanzibar (Tanzania). Fish were collected monthly for one year at three sites (lower, intermediate and upper reaches) in each creek using a seine net (each haul covering 170 m(2)). Density, species number and diversity of fish were all higher at sites with dense cover of macrophytes (seagrass and macroalgae) than over unvegetated sandy sites. In general, fish assemblages mainly comprised juveniles of a few abundant taxa, e.g. Mugil cephalus, Mugilidae spp. and Leiognathus equulus at sites with mud substratum and Germs oyena, Lethrinus harak and Sillago sihama at sites dominated by macrophytes. Multivariate analyses revealed significant separations in fish assemblage composition within the two creeks where the bottom substratum differed among sites. Overall, season seemed to have little effect on density, species number, diversity index (H') and assemblage structure of fish. Water condition variables were also relatively stable across the season, although a short-term fluctuation primarily induced by decreased salinity, occurred during the heavy rains in April and May. Fish assemblage structure was not significantly affected by any of the abiotic factors tested. However, significant regressions were found between the other fish variables and environmental variables, but since these associations were mostly species-specific and generally inconsistent, we suggest that the overall distribution patterns of fish were mainly an effect of particular substrate preferences of fish species rather than contemporary water conditions.

  • 53.
    Mwandya, Augustine
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Influence of mangrove deforestation on trophic organization of fish assemblages in creek systemsManuscript (Other academic)
    Abstract [en]

    The mangrove biotopes in Tanzania are under increasing pressure from domestic uses and changes in land-use for aquaculture and solar salt farms. To investigate the impacts of man-made activities on trophic structure of mangrove-associated fish species, sampling of fish from various trophic groups was performed in mangrove creeks. Trophic organization and stable isotope signatures (δ 13C and δ 15N) of fish in undisturbed areas of mangrove creeks were compared with clear-cut areas of mangrove as well as with reservoirs for saltworks or fish farms constructed after mangrove clearing. Results showed significantly higher densities, species numbers, diversity (H’) and numbers of trophic groups in undisturbed sites compared to both types of disturbed sites. Overall, omnivorous fish comprised the most abundant feeding guild, with the highest number of individuals found in the cleared sites followed in order by the uncleared sites and the reservoirs. The feeding guild zoobenthivores/piscivores was the most diverse group, with the highest species richness in the undisturbed areas. Multivariate analysis showed that assemblage structure of omnivores in the reservoirs was separated from those in the uncleared and cleared sites, while zoobenthivores/piscivores differed between uncleared sites and the disturbed areas (cleared sites and reservoirs). Stable isotope ratios of δ13C and δ15N values in fish tissue muscles indicate significant diet shifts between undisturbed and disturbed mangrove creek systems, although the effects are species-specific. Our findings suggest that mangrove deforestation combined with land-use changes, such as salt- or fish farm constructions, has a greater impact on the trophic structure of fish in mangrove creeks than mangrove deforestation only. Hence, the extent and severity of disturbance seem to be important in predicting fish assemblage composition.

  • 54.
    Mwandya, Augustine
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Öhman, Marcus C
    Stockholm University, Faculty of Science, Department of Zoology.
    Andersson, Mathias H
    Stockholm University, Faculty of Science, Department of Zoology.
    Mgaya, Yunus
    Fisheries and Aquaculture.
    Fish assemblages in Tanzanian mangrove creek systems influenced by solar salt farm constructions2009In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 82, no 2, p. 193-200Article in journal (Refereed)
  • 55.
    Mwandya, Augustine
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Mgaya, Yunus
    Fisheries and Aquculture.
    Öhman, Marcus
    Stockholm University, Faculty of Science, Department of Zoology.
    Ian, Bryceson
    International Environment and Development Studies.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Distribution patterns of the striped mullet (Mugil cephalus) in mangrove creeks of Zanzibar, TanzaniaManuscript (Other academic)
    Abstract [en]

    Spatial and seasonal variations in density of the striped mullet Mugil cephalus were investigated in four mangrove creeks in Zanzibar (Tanzania) during a one-year cycle. Fish were collected monthly in the lower, intermediate and upper reaches of each creek using a beach seine net (each haul covering 170 m2). All individuals collected were juveniles with a mean size of 2 to 16 cm (standard length). The density of juvenile mullets inhabiting mangrove creeks differed significantly among the different creeks, but the patterns within creeks were consistent, with higher densities upstream in three of the creeks. In general, small-sized juvenile mullets (2-10 cm) were more abundant in the upper reaches compared to the lower and intermediate sites in most creeks. Seasonal patterns were fairly weak, although high mullet densities were observed during the period of heavy rains (from March to May). Principal component analysis (PCA) showed that a muddy bottom with microphytobenthos was likely important to explain high mullet densities, although site-specific variables like low water depth and water clarity may also be important. Our findings suggest that the densities of juvenile striped mullet vary among sites and creeks in response to refuge availability from turbid shallow waters and the accessibility of food resources from benthic microalgae.

  • 56.
    Nascimento, Francisco J. A.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Dahl, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Deyanoya, Diana
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lyimo, Liberatus D.
    Bik, Holly M.
    Schuelke, Taruna
    Pereira, Tiago José
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Creer, Simon
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Above-below surface interactions mediate effects of seagrass disturbance on meiobenthic diversity, nematode and polychaete trophic structure2019In: Communications biology, ISSN 2399-3642, Vol. 2, article id 362Article in journal (Refereed)
    Abstract [en]

    Ecological interactions between aquatic plants and sediment communities can shape the structure and function of natural systems. Currently, we do not fully understand how sea- grass habitat degradation impacts the biodiversity of belowground sediment communities. Here, we evaluated indirect effects of disturbance of seagrass meadows on meiobenthic community composition, with a five-month in situ experiment in a tropical seagrass meadow. Disturbance was created by reducing light availability (two levels of shading), and by mimicking grazing events (two levels) to assess impacts on meiobenthic diversity using high- throughput sequencing of 18S rRNA amplicons. Both shading and simulated grazing had an effect on meiobenthic community structure, mediated by seagrass-associated biotic drivers and sediment abiotic variables. Additionally, shading substantially altered the trophic structure of the nematode community. Our findings show that degradation of seagrass meadows can alter benthic community structure in coastal areas with potential impacts to ecosystem functions mediated by meiobenthos in marine sediments.

  • 57. Nordlund, Lina Mtwana
    et al.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Biodiversity loss in seagrass meadows due to local invertebrate fisheries and harbour activities2013In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 135, p. 231-240Article in journal (Refereed)
    Abstract [en]

    Seagrass meadows provide a wide variety of ecosystem services, but their distribution and health are adversely affected by man. In the present study, we examined the influence of coastal exploitation in terms of invertebrate harvesting and harbour activity on invertebrate community composition in subtropical seagrass meadows at Inhaca Island, Mozambique, in the Western Indian Ocean. There was a fivefold higher invertebrate density and biomass, and clearly higher invertebrate species richness, in the protected (control) site compared to the two exploited sites. The causes for the clear differences between protected and exploited sites were probably a result of (1) the directional outtake of large edible or saleable invertebrates (mostly molluscs) and the absence of boat traffic in the harvested site, and (2) harbour activities. Invertebrate community composition in the two exploited sites also differed (although less clear), which was likely due to inherent distinction in type of disturbance. Our findings revealed that protection of seagrass habitat is necessary and that disturbances of different origin might require different forms of management and conservation. Designing protected areas is however a complex process due to competition for use and space with activities such as invertebrate harvesting and harbours.

  • 58.
    Nyqvist, A
    et al.
    Göteborgs universitet.
    André, C
    Göteborgs universitet, Tjärnö.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Baden, SP
    Göteborgs universitet, Kristineberg.
    Åberg, P
    Göteborgs universitet.
    Dynamics of Seagrass Meadows on the Swedish Skagerrak Coast2009In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 38, no 2, p. 85-88Article in journal (Refereed)
    Abstract [en]

    Seagrasses have declined in many places around the world, and the Swedish Skagerrak coast is no exception. Between the 1980s and 2000, the cover of eelgrass (Zostera marina L.) on the Swedish Skagerrak coast decreased about 60%. In the present study, the sites that were investigated in the 1980s and 2000 were revisited (1655 ha) in 2003 and 2004 to investigate long and short term temporal and spatial differences in eelgrass coverage. The distribution of eelgrass was mapped from a small boat using an aquascope and a GPS receiver. No variation in total (about 150 km) or regional (about 20 km) eelgrass cover was found between 2000 and 2004, but there were substantial changes (both losses and gains) in meadow size on a local (less than about 2 km) scale. The results have implications for management of shallow soft bottoms, particularly because it was shown that even though no eelgrass is found in a single survey in a specific area, there could be eelgrass growing there in the following years.

  • 59.
    Perry, Diana
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Staveley, Thomas A. B.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Habitat Connectivity of Fish in Temperate Shallow-Water Seascapes2018In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 4, article id 440Article in journal (Refereed)
    Abstract [en]

    Movements of organisms comprise a fundamental aspect of coastal habitat connectivity. Determining the distribution and co-existence of habitat specialists and generalists in shallow-water seascapes leads to a better understanding of the strength of connectivity-driven community patterns in coastal areas. In this study, unbaited Remote Underwater Video (RUV) systems were used to examine habitat usage and connectivity of fish within six shallow-water coastal seascapes on the Swedish west coast. Within each seascape, video sampling was conducted at three different shallow-water habitats: seagrass meadows, rock-macroalgae and unvegetated areas, in June 2014. Comparative analyses showed that the shallow-water fish community was similar in adjacent habitats within a seascape, though abundances of fish were higher within the structurally complex habitats. All habitats were dominated by juveniles, highlighting the importance of the coastal seascape for early fish life stages. The findings demonstrate that adjacent shallow-water habitats in temperate coastal waters are linked through similar species utilization and that the coastal matrix could be regarded in terms of a seascape nursery for fish. The study highlights the importance of considering shallow-water seascape connectivity in coastal conservation planning and management.

  • 60.
    Perry, Diana
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Staveley, Thomas A. B.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hammar, Linus
    Meyers, Alyssa
    Lindborg, Regina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Temperate fish community variation over seasons in relation to large-scale geographic seascape variables2018In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 75, no 10, p. 1723-1732Article in journal (Refereed)
    Abstract [en]

    In shallow-water marine environments, ecosystem functioning is a complex interworking of fine-scale characteristics and region-wide factors, and the importance of these variables can vary on multiple temporal and spatial scales. This underwater video study targeted seasonal changes in the fish community of seagrass habitats along the Swedish west coast and the influence of offshore seascape variables (latitudinal position, wave exposure, open ocean, and deep water). Results showed that fish assemblage structure exhibited seasonal changes between summer and autumn and strong spatiotemporal variations in the importance of offshore factors affecting shallow-water fish communities. In summer, abundance from the Gobiidae family responded to wave exposure, whereas the Gadidae family and juvenile migrant habitat preference guild responded to latitudinal position and proximity to deep water. In autumn, deep water was related to abundance of Gadidae and juvenile migrants, whereas latitudinal position influenced Gasterosteidae. These findings underscore the importance of understanding the influence of offshore factors on facets of coastal fish assemblages to address large-scale geographic connectivity along nearshore–offshore gradients.

  • 61. Procaccini, Gabriele
    et al.
    Ruocco, Miriam
    Marin-Guirao, Lazaro
    Dattolo, Emanuela
    Brunet, Christophe
    D'Esposito, Daniela
    Lauritano, Chiara
    Mazzuca, Silvia
    Serra, Ilia Anna
    Bernardo, Letizia
    Piro, Amalia
    Beer, Sven
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Buapet, Pimchanok
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Prince of Songkla University, Thailand.
    Rasmusson, Lina M.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Felisberto, Paulo
    Gobert, Sylvie
    Runcie, John W.
    Silva, Joao
    Olive, Irene
    Costa, Monya M.
    Barrote, Isabel
    Santos, Rui
    Depth-specific fluctuations of gene expression and protein abundance modulate the photophysiology in the seagrass Posidonia oceanica2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 42890Article in journal (Refereed)
    Abstract [en]

    Here we present the results of a multiple organizational level analysis conceived to identify acclimative/adaptive strategies exhibited by the seagrass Posidonia oceanica to the daily fluctuations in the light environment, at contrasting depths. We assessed changes in photophysiological parameters, leaf respiration, pigments, and protein and mRNA expression levels. The results show that the diel oscillations of P. oceanica photophysiological and respiratory responses were related to transcripts and proteins expression of the genes involved in those processes and that there was a response asynchrony between shallow and deep plants probably caused by the strong differences in the light environment. The photochemical pathway of energy use was more effective in shallow plants due to higher light availability, but these plants needed more investment in photoprotection and photorepair, requiring higher translation and protein synthesis than deep plants. The genetic differentiation between deep and shallow stands suggests the existence of locally adapted genotypes to contrasting light environments. The depth-specific diel rhythms of photosynthetic and respiratory processes, from molecular to physiological levels, must be considered in the management and conservation of these key coastal ecosystems.

  • 62.
    Rasmusson, Lina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Gothenburg, Sweden.
    Buapet, Pimchanok
    George, Rushingisha
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Tanzania Fisheries Research Institute (TAFIRI), Tanzania.
    Gunnarsson, Pontus
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Effects of temperature and hypoxia on respiration, photorespiration and photosynthesis of seagrassesManuscript (preprint) (Other academic)
  • 63.
    Rasmusson, Lina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Gothenburg, Sweden.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gunnarsson, Pontus
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    George, Rushingisha
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Tanzania Fisheries Research Institute (TAFIRI), Tanzania.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Seagrass productivity during temperature variations: estimation of a whole plant Q10 for respiration and photosynthesis in Zostera marinaManuscript (preprint) (Other academic)
  • 64.
    Rasmusson, Lina M.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Effects of increased temperature on respiration and photosynthesis differ among different leaf parts and with tissue age of the seagrass Zostera marinaManuscript (preprint) (Other academic)
  • 65.
    Rasmusson, Lina M.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Gothenburg, Sweden.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Gothenburg, Sweden.
    Gunnarsson, Pontus C. B.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    George, Rushingisha
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Tanzania Fisheries Research Institute (TAFIRI), Tanzania.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Estimation of a whole plant Q10 to assess seagrass productivity during temperature shifts2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 12667Article in journal (Refereed)
    Abstract [en]

    Through respiration and photosynthesis, seagrass meadows contribute greatly to carbon and oxygen fluxes in shallow coastal waters. There is increasing concern about how shallow-water primary producers will react to a near-future climate scenario with increased temperature variation. When modelling primary productivity under high temperature variability, Q10 values are commonly used to predict rate changes depending on biophysical factors. Q10 values are often assumed to be constant and around 2.0 (i.e. a doubling of the rate with a temperature increase of 10 degrees C). We aimed to establish how the gas exchange of seagrass (Zostera marina) tissues at various maturity stages would respond over a broad range of temperatures. Seagrass shoot maturity stage clearly affected respiration and apparent photosynthesis, and the Q10 results indicated a skewed balance between the two processes, with a higher photosynthetic Q10 during periods of elevated temperatures. When estimating whole-plant Q10 in a realistic maximal temperature range, we found that the overall response of a seagrass plant's net O-2 exchange balance can be as much as three to four times higher than under ambient temperatures. Our findings indicate that plant tissue age and temperature should be considered when assessing and modelling carbon and oxygen fluctuations in vegetated coastal areas.

  • 66.
    Rasmusson, Lina M.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lauritano, Chiara
    Department of Integrative Marine Ecology, Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy.
    Procaccini, Gabriele
    Department of Integrative Marine Ecology, Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Respiratory oxygen consumption in the seagrass Zostera marina is affected by light and varies on a diel basis: a combined gas exchange and gene expression studyManuscript (preprint) (Other academic)
  • 67.
    Rasmusson, Lina M.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lauritano, Chiara
    Procaccini, Gabriele
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Buapet, Pimchanok
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Prince of Songkla University, Thailand.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Respiratory oxygen consumption in the seagrass Zostera marina varies on a diel basis and is partly affected by light2017In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 164, no 6, article id 140Article in journal (Refereed)
    Abstract [en]

    The seagrass Zostera marina is an important marine ecosystem engineer, greatly influencing oxygen and carbon fluctuations in temperate coastal areas. Although photosynthetically driven gas fluxes are well studied, the impact of the plant's mitochondrial respiration on overall -CO2 and -O-2 fluxes in marine vegetated areas is not yet understood. Likewise, the gene expression in relation to the respiratory pathway has not been well analyzed in seagrasses. This study uses a combined approach, studying respiratory oxygen consumption rates in darkness simultaneously with changes in gene expression, with the aim of examining how respiratory oxygen consumption fluctuates on a diel basis. Measurements were first made in a field study where samples were taken directly from the ocean to the laboratory for estimations of respiratory rates. This was followed by a laboratory study where measurements of respiration and expression of genes known to be involved in mitochondrial respiration were conducted for 5 days under light conditions mimicking natural summer light (i.e.,15 h of light and 9 h of darkness), followed by 3 days of constant darkness to detect the presence of a potential circadian clock. In the field study, there was a clear diel variation in respiratory oxygen consumption with the highest rates in the late evening and at night (0.766 and 0.869 mu mol -O-2 m(-2) s(-1), respectively). These repetitive diel patterns were not seen in the laboratory, where water conditions (temperature, pH, and oxygen) showed minor fluctuations and only light varied. The gene expression analysis did not give clear evidence on drivers behind the respiratory fluxes; however, expression levels of the selected genes generally increased when the seagrass was kept in constant darkness. While light may influence mitochondrial respiratory fluxes, it appears that other environmental factors (e.g., temperature, pH, or oxygen) could be of significance too. As seagrasses substantially alter the proportions of both oxygen and inorganic carbon in the water column and respiration is a great driver of these alterations, we propose that acknowledging the presence of respiratory fluctuations in nature should be considered when estimating coastal carbon budgets. As dark respiration in field at midnight was approximately doubled from that of midday, great over-, or underestimations of the respiratory carbon dioxide release from seagrasses could be made if values are just obtained at one specific time point and considered constant.

  • 68. Snickars, M.
    et al.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Sundblad, G.
    Bergström, U.
    Downie, A. -L
    Lindegarth, M.
    Mattila, J.
    Species-environment relationships and potential for distribution modelling in coastal waters2014In: Journal of Sea Research, ISSN 1385-1101, E-ISSN 1873-1414, Vol. 85, p. 116-125Article in journal (Refereed)
    Abstract [en]

    Due to increasing pressure on the marine environment there is a growing need to understand species-environment relationships. To provide background for prioritising among variables (predictors) for use in distribution models, the relevance of predictors for benthic species was reviewed using the coastal Baltic Sea as a case-study area. Significant relationships for three response groups (fish, macroinvertebrates, macrovegetation) and six predictor categories (bottom topography, biotic features, hydrography, wave exposure, substrate and spatiotemporal variability) were extracted from 145 queried peer-reviewed field-studies covering three decades and six subregions. In addition, the occurrence of interaction among predictors was analysed. Hydrography was most often found in significant relationships, had low level of interaction with other predictors, but also had the most non-significant relationships. Depth and wave exposure were important in all subregions and are readily available, increasing their applicability for cross-regional modelling efforts. Otherwise, effort to model species distributions may prove challenging at larger scale as the relevance of predictors differed among both response groups and regions. Fish and hard bottom macrovegetation have the largest modelling potential, as they are structured by a set of predictors that at the same time are accurately mapped. A general importance of biotic features implies that these need to be accounted for in distribution modelling, but the mapping of most biotic features is challenging, which currently lowers the applicability. The presence of interactions suggests that predictive methods allowing for interactive effects are preferable. Detailing these complexities is important for future distribution modelling.

  • 69.
    Staveley, Thomas A. B.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. AquaBiota Water Research, Sweden.
    Jacoby, David M. P.
    Perry, Diana
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Agricultural Sciences, Sweden.
    van der Meijs, Felix
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lagenfelt, Ingvar
    Cremle, Mikael
    Gullstrom, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Gothenburg, Sweden.
    Sea surface temperature dictates movement and habitat connectivity of Atlantic cod in a coastal fjord system2019In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758Article in journal (Refereed)
    Abstract [en]

    While movements of organisms have been studied across a myriad of environments, information is often lacking regarding spatio-seasonal patterning in complex temperate coastal systems. Highly mobile fish form an integral part of marine food webs providing linkages within and among habitats, between patches of habitats, and at different life stages. We investigated how movement, activity, and connectivity patterns of Atlantic cod (Gadus morhua) are influenced by dynamic environmental conditions. Movement patterns of 39 juvenile and subadult Atlantic cod were assessed in two coastal sites in the Swedish Skagerrak for 5 months. We used passive acoustic telemetry and network analysis to assess seasonal and spatial movement patterns of cod and their relationships to different environmental factors, using statistical correlations, analysis of recurrent spatial motifs, and generalized linear mixed models. Temperature, in combination with physical barriers, precludes significant connectivity (complex motifs) within the system. Sea surface temperature had a strong influence on connectivity (node strength, degree, and motif frequency), where changes from warmer summer waters to colder winter waters significantly reduced movement activity of fish. As the seasons changed, movement of fish gradually decreased from large-scale (km) linkages in the summer to more localized movement patterns in the winter (limited to 100s m). Certain localized areas, however, were identified as important for connectivity throughout the whole study period, likely due to these multiple-habitat areas fulfilling functions required for foraging and shelter. This study provides new knowledge regarding inshore movement dynamics of juvenile and subadult Atlantic cod that use complex, coastal fjord systems. The findings show that connectivity, seasonal patterns in particular, should be carefully considered when selecting conservation areas to promote marine stewardship.

  • 70.
    Staveley, Thomas A. B.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Perry, Diana
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lindborg, Regina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Seascape structure and complexity influence temperate seagrass fish assemblage composition2017In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 40, no 8, p. 936-946Article in journal (Refereed)
    Abstract [en]

    Understanding how spatial patterning relates to ecological processes is fundamental to define important species-environment associations at broader scales. Analyses targeting habitat structure (i.e. composition and configuration) in terrestrial landscapes are increasing, but similar studies in marine landscapes are still relatively uncommon. In this study, we explored how seascape structure and complexity (determined from significant spatial pattern metrics) influenced summer and autumn fish assemblage composition in 30 seagrass (Zostera marina) meadows along the west coast of Sweden. Species density was not influenced by seascape structure in any season. In contrast, the majority of significant fish assemblage variables were influenced by seascape structure during the summer (i.e. abundance and proportion of juveniles, abundance of Labridae and abundance of occasional shallow-water visitors) whilst fewer in the autumn (i.e. abundance of occasional shallow-water visitors and Synganthidae). For instance, less complex seascapes were more suitable for juvenile assemblages in summer, as these seascapes exhibit larger patch sizes of appropriate habitat (e.g. Z. marina) and less edge boundaries providing refuges from predators and food resources. Abundances of migrating fish, such as the sea trout Salmo trutta, also responded positively to a less complex seascape in the summer though perhaps ecological processes, such as prey availability, were additional contributing factors driving this relationship. High complexity seascapes only had a positive influence on the abundance of taxa using multiple habitats (Labridae during the summer). Our study shows that fish assemblages in temperate marine environments are significantly linked to spatial habitat patterning and seascape complexity. This offers valuable insights into species-habitat-seascape linkages, information important for coastal conservation and marine spatial planning.

  • 71.
    Staveley, Thomas
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hernvall, Patrick
    Stjärnkvist, Nellie
    van der Meijs, Felix
    Wikström, Sofia
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Exploring seagrass fish assemblages in relation to the habitat patch mosaic in the brackish Baltic SeaManuscript (preprint) (Other academic)
  • 72.
    Staveley, Thomas
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Jacoby, David
    Perry, Diana
    van der Meijs, Felix
    Lagenfelt, Ingvar
    Cremle, Mikael
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Sea surface temperature dictates movement and connectivity of Atlantic cod in a coastal fjord systemManuscript (preprint) (Other academic)
  • 73.
    Wallner-Hahn, Sieglind
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    de la Torre-Castro, Maricela
    Stockholm University, Faculty of Science, Department of Physical Geography. Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Eklöf, Johan S.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Muthiga, Nyawira A.
    Uku, Jacqueline
    Cascade effects and sea-urchin overgrazing: An analysis of drivers behind the exploitation of sea-urchin predators for management improvement2015In: Ocean and Coastal Management, ISSN 0964-5691, E-ISSN 1873-524X, Vol. 107, p. 16-27Article in journal (Refereed)
    Abstract [en]

    Marine ecosystems generate a wide variety of goods and services, but are globally deteriorating due to multiple drivers associated with anthropogenic activities. Intense fishing pressure can lead to changes in structure and function of marine food webs. Particularly overfishing of predatory species at high trophic levels can cause cascading effects leading to ecosystem degradation, affecting both marine organisms and people dependent on them. In the Western Indian Ocean region, intensive fishing takes place and degradation of coral reefs and seagrass beds has been documented. One reason behind this degradation is overgrazing by increasing numbers of sea urchins. An essential step towards better management is to thoroughly understand the drivers leading to such changes in ecosystems. Against this background, the general aim of this study was to gain understanding about whether sea urchin predators in the WIO region are fished, and to identify the drivers behind the fishing of these species. The study had four objectives: (i) to document if and how predatory fish eating sea urchins are caught in smallscale fisheries, (ii) to assess if, and if so why, sea urchin predators are targeted species, (iii) to assess if and to what degree local ecological knowledge (LEK) on ecological complexity involving sea urchins and their predators (e.g. trophic cascades) is present among local fishers, and (iv) to identify fishers' suggestions for management that can reduce problems linked to sea urchin overgrazing. The results show that all investigated species of sea urchin predators are fished by local small-scale fishers. Most sea urchin predators are not actively targeted, are not popular local food fish, and have minor use and economic importance for fishers. This stands in sharp contrast to their ecological keystone role by controlling sea urchin populations. The fishers' awareness and LEK were weak and partly lacking. Management suggestions targeted mostly the symptoms of food web changes rather than the drivers behind them.

    Based on the results we suggest that management of degraded ecosystems, as a result of food web changes, should encompass a wide variety of strategies and scales. Specific suggestions for sea urchin predator management are education of local stakeholders on destructive gear effects and food web complexity, further investigations of catch- and release fishing as well as the use of selective gears.

  • 74.
    Wilhelmsson, Dan
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Zoologiska Institutionen.
    Malm, T.Thompson, R.Tchou, J.Sarantakos, G.McCormick, N.Luitjens, S.Gullström, MartinStockholm University, Faculty of Science, Department of Zoology.Patterson Edwards, J. K.Amir, O.Dubi, A.
    Greening Blue Energy: Identifying and managing the biodiversity risks and opportunities of offshore renewable energy2010Collection (editor) (Other academic)
  • 75.
    Yahya, Saleh A. S.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Science, Department of Systems Ecology.
    Öhman, Marcus C.
    Stockholm University, Faculty of Science, Department of Zoology.
    Jiddawi, Narriman
    Andersson, Mathias H.
    Stockholm University, Faculty of Science, Department of Zoology.
    Mgaya, Yunus D.
    Lindahl, Ulf
    Coral bleaching and habitat effects on colonisation of reef fish assemblages: an experimental study2011In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 94, no 1, p. 16-23Article in journal (Refereed)
    Abstract [en]

    Degradation and mortality of corals is increasing worldwide and is expected to have significant effects on coral reef fish; hence studies on these effects are essential. In the present study, a field experiment was set up within Mafia Island Marine Park in Tanzania (East Africa) to examine the effects of bleaching and habitat structure on colonisation of coral reef fish assemblages. Live and bleached staghorn coral Acropora formosa was transplanted onto plots in a site dominated by sand and rubble, and the experimental design comprised of three treatments: live coral, bleached coral and eroded coral rubble. There was an immediate increase (within 24 h) in fish abundance and diversity in the two treatments with standing corals. Overall, live and bleached coral plots showed similar effects, but differed from the eroded coral plots which had a much lower abundance and diversity of fish. In general, fish species diversity changed with time over the study period while fish abundance did not. Multivariate analyses showed that while there were differences in fish assemblage structure between standing corals and the eroded coral treatment, there was neither a difference between live and bleached coral treatments nor any temporal effects on fish assemblage structure. Our findings suggest that physical structure and complexity of habitat have stronger effects on colonisation of reef fish assemblages than changes in coral health (such as bleaching) which do not affect coral structure. This may have important implications for appropriate coral reef management.

  • 76.
    Yahya, Saleh A.S.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Öhman, Marcus
    Stockholm University, Faculty of Science, Department of Zoology.
    Jiddawi, Narriman
    Mgaya, Yunus
    Fish assemblages in relation to quality, structure and configuration of staghorn coral reefs at Mafia and Zanzibar islands, TanzaniaManuscript (Other academic)
  • 77.
    Yahya, Saleh A.S.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Muhando, Christopher
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Fish and sea urchin community patterns and habitat effects on Tanzanian coral reefsManuscript (preprint) (Other academic)
12 51 - 77 of 77
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