| 1. |
- Alsterberg, Christian, 1982, et al.
(författare)
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Experimental warming and toxicant exposure can result in antagonistic effects in a shallow-water sediment system
- 2013
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 488, s. 89-101
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that future warming will exacerbate the effect of local stressors such as toxicants. In this study the individual and combined effects of warming (+4 degrees C above ambient) and a toxicant (the antifouling substance copper pyrithione) on natural intact shallow-water sediment were studied in an outdoor flow-through facility. Functional (oxygen and inorganic nutrient fluxes in light and dark, bacterial production) and structural (biomass and composition of microphytobenthos and meiofauna) variables were measured. Warming was found to modify the toxicant response antagonistically, i.e. warming removed the negative effect of the toxicant exposure. This antagonism was found for functions depending on light (gross primary production, 24 h net oxygen fluxes, oxygen and silica fluxes). Most functional variables were, however, affected by warming alone, while structural variables were affected by the toxicant alone. At the end of the experiment, the system had 2 types of microalgal communities, a typical benthic algal mat and a floating periphytic mat. Both the benthic and floating microalgal mats were significantly affected by the toxicant alone, but in opposite directions. The biomass of the benthic algal mat was significantly higher under toxicant exposure, whereas the biomass of the floating periphytic mat was lower. Our results suggest that the effects of toxicants in aquatic environments may be reduced (rather than amplified) by warming. We also show that autotrophic communities can respond differently within the same ecosystem and that habitat may determine the mode of response to warming-toxicant exposures in aquatic environments.
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| 2. |
- Arendt, Kristine Engel, et al.
(författare)
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Differences in plankton community structure along the Godthåbsfjord, from the Greenland Ice sheet to offshore waters
- 2010
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Ingår i: Marine Ecology Progress Series. - 0171-8630. ; 401, s. 49-62
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Tidskriftsartikel (refereegranskat)abstract
- This study describes differences in plankton community structure and in chemical and physical gradients between the offshore West Greenland Current system and inland regions close to the Greenland Ice Sheet during the post-bloom in Godthåbsfjorden (64° N, 51° W). The offshore region had pronounced vertical mixing, with centric diatoms and Phaeocystis spp. dominating the phytoplankton, chlorophyll (chl) a (0.3 to 3.9 μg l–1) was evenly distributed and nutrients were depleted in the upper 50 m. Ciliates and heterotrophic dinoflagellates constituted equal parts of the protozooplankton biomass. Copepod biomass was dominated by Calanus spp. Primary production, copepod production and the vertical flux were high offshore. The water column was stratified in the fjord, causing chl a to be concentrated in a thin sub-surface layer. Nutrients were depleted above the pycnocline, and Thalassiosira spp. dominated the phytoplankton assemblage close to the ice sheet. Dinoflagellates dominated the protozooplankton biomass, whereas copepod biomass was low and was dominated by Pseudocalanus spp. and Metridia longa. Primary production was low in the outer part of the fjord but considerably higher in the inner parts of the fjord. Copepod production was exceeded by protozooplankton production in the fjord. The results of both physical/chemical factors and biological parameters suggest separation of offshore and fjord systems.
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| 3. |
- Baden, Susanne P., 1952, et al.
(författare)
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Shift in seagrass food web structure over decades is linked to overfishing
- 2012
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Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 451, s. 61-73
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Tidskriftsartikel (refereegranskat)abstract
- Empirical field studies in seagrass have revealed that overgrowth by filamentous algae which reduces seagrass growth can be explained by a top-down cascading effect caused by declines in top predators, which is enforced by eutrophication. On the Swedish west coast, 60% of the seagrass has disappeared since the 1980s. We hypothesised that overfishing, responsible for a >90% decline in the cod stock, and the 4 to 8 times increase in nutrient load since the 1930s have altered the seagrass structure and function during recent decades. We used quantitative samples from the 1980s and 2000s and analysed the trends in abundance of the 4 feeding guilds: top predatory fish, intermediate predatory fish, crustacean omnivores and mesoherbivores. Since the 1980s, the commercial catch of gadoids on the Swedish west coast has decreased by >90 %, and here we found that the biomass of top predators (gadoids and trout) that forage in seagrass has decreased by approximately 80%. In contrast, the biomass of intermediate predatory fish (gobids and sticklebacks) has increased 8 times during summer and 11 times during autumn, while mesoherbivores (idoteids and gammarids >7 mm) have more or less disappeared from the seagrass bed. We thus found clear evidence that a shift in seagrass food web structure has taken place over the last 3 decades. Combining these findings with our recent empirical results from field cage experiments in the Skagerrak seagrass, where we manipulate top-down and bottom-up regulation, we conclude that lack of grazers in concert with eutrophication most likely contributed to the overgrowth by filamentous algae and disappearance of the seagrass on the Swedish west coast.
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| 4. |
- Bartolino, Valerio
(författare)
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Scale-dependent detection of the effects of harvesting a marine fish population
- 2012
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 444, s. 251-272
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Tidskriftsartikel (refereegranskat)abstract
- Certain ecological processes dominate others at particular scales, and the response of populations to exogenous and endogenous forces are typically scale dependent. In spite of this central role played by scale, the temporal and spatial scales of human impacts on ecosystems and populations remain almost unknown. We applied a multiscale regression analysis to investigate the spatiotemporal scales which characterize the fisheries exploitation of yellowfin sole Limanda aspera in the Bering Sea. We found that harvesting affects the abundance of this species simultaneously at local and regional scales. At the local scale harvesting produced a negative effect on local fish densities, particularly in those areas and seasons of high fish aggregation, when both the vulnerability of the fish and the fishing effort increase. At the regional scale harvesting was characterized by a widespread negative effect on the whole fish population. Our findings demonstrate that (1) detection of the fisheries exploitation effects on natural populations is sensitive to the scale of investigation, (2) fisheries harvesting can simultaneously affect multiple ecological scales which are not linearly correlated with each other. We developed analytical techniques for the detection of scale-dependent processes, which can be readily applied to other systems. Our results provide insights on the risks of extrapolating the effects of harvesting on natural populations across scales, making the issues of scale and space central to the management and conservation of natural populations.
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| 5. |
- Bekkevold, D., et al.
(författare)
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Genetic mixed-stock analysis of Atlantic herring populations in a mixed feeding area
- 2011
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 442, s. 187-199
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Tidskriftsartikel (refereegranskat)abstract
- Determining spatio-temporal distributions of fish populations is of interest to marine ecology, in general, and to fisheries science in particular. Genetic mixed-stock analysis is routinely applied in several anadromous fishes for determining migratory routes and timing but has rarely been used for marine fishes, for which population differentiation is commonly weak and the method presumably less powerful. We used microsatellite information for Northeast Atlantic herring Clupea harengus L. populations and mixed stocks to address 2 questions. We used simulated mixture samples and 3 different statistical approaches to determine whether mixed stock composition could be determined with accuracy. Simulations showed that the applied approaches and mixture samples of 100 individuals enabled detailed composition analyses on a regional level, with resolution for tracing the ecologically dominant Rügen (Greifswalder Bodden) herring population. We then estimated spatio-temporal variation in herring migratory behaviour in the Skagerrak from 17 mixed samples collected over 2 seasons and 2 yr, and identified hitherto undescribed differences in distributions among populations that feed and winter in the area.
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| 6. |
- Bergmark, Paulina, et al.
(författare)
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Lophelia pertusa conservation in the North Sea using obsolete offshore structures as artificial reefs
- 2014
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 516, s. 275-280
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Tidskriftsartikel (refereegranskat)abstract
- Deep-water coral reefs are classified as vulnerable marine ecosystems, with trawling identified as the primary cause of reef destruction. Lophelia pertusa is the main reef-building species in deep-water coral reefs. In addition to occurring on natural hard substrates, the species has been previously observed on standing offshore oil and gas structures in the North Sea. In this study, we review the available published information about Lophelia growth on standing offshore oil and gas industry structures in the North Sea. We discuss the potential uses of obsolete offshore structures repurposed as artificial reefs for targeted Lophelia habitat. Our survey of previous studies indicates that artificial reefs created from obsolete structures have a strong potential to form Lophelia reef communities similar to those found on natural substrates, although the absence of the polychaete worm Eunice norvegica poses some concerns about the completeness of the coral communities that develop on artificial reef structures.
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| 7. |
- Bergström, Lena, et al.
(författare)
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Effects of an offshore wind farm on temporal and spatial patterns in the demersal fish community
- 2013
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 485, s. 199-210
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Tidskriftsartikel (refereegranskat)abstract
- The rapid increase in offshore wind energy worldwide has raised concern about its potential risks to marine biodiversity due to habitat alteration, disturbance from noise and electromagnetic fields. This study presents results of surveillance studies performed at the Lillgrund wind farm in Sweden to investigate the integrated effects of these factors on the abundance and distribution patterns of benthic fish communities. The studies revealed no large-scale effects on fish diversity and abundance after establishment of the wind farm when compared to the development in 2 reference areas. Changes in some species and in community composition were observed over time but occurred in parallel in at least one reference area, indicating that fish communities in the wind farm area were mainly driven by the same environmental factors as those in surrounding areas. However, changes at smaller spatial scales were evident. Increased densities of all studied piscivores (cod, eel, shorthorn sculpin), as well as the reef-associated goldsinny wrasse, were observed close to the foundations in the first years of operation. The increase was probably attributed mainly to local changes in distribution rather than to immigration or increased local productivity. Simultaneously, weak or no aggregation of black goby, eelpout and shore crab, all potentially reef-associated but also prey species of the studied piscivores, was observed, which may indicate enhanced top-down control near the foundations.
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| 8. |
- Berkström, Charlotte, 1978-, et al.
(författare)
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Ecological connectivity and niche differentiation between two closely related fish species in the mangrove−seagrass−coral reef continuum
- 2013
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 477, s. 201-215
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Tidskriftsartikel (refereegranskat)abstract
- We aim to understand ontogenetic shifts in habitat use and feeding patterns by 2 fish species, Lutjanus fulviflamma and L. ehrenbergii, within a tropical seascape in East Africa. Stomach contents and stable isotope signatures of muscle tissues (δ13C and δ15N) were compared between and within species. Fish of all life stages and potential food items were sampled from mangrove creeks, seagrass beds, and coral reefs around Mafia Island, Tanzania. Due to similarities in morphology between species, correct species identity was confirmed using genetic barcoding (mtDNA, partial sequence of cytochrome oxidase subunit I [COI]). Stable isotope analysis in R (based on mixing models) confirmed that δ13C and δ15N values in L. fulviflamma and L. ehrenbergii reflected those of prey items caught in different habitats. Diets and mean δ13C and δ15N values of muscle tissue differed between life stages of fish, indicating ontogenetic changes in habitat and diet. L. fulviflamma and L. ehrenbergii differed in diet and δ13C and δ15N values of muscle tissue, although they overlapped in habitat use, suggesting food resource partitioning between the 2 species. Furthermore, diet overlap indexes were low between subadult species in mangrove and seagrass or coral habitats. L. fulviflamma displayed a diet shift with decreasing importance of small crustaceans in juveniles and an increasing importance of prey fishes in subadults and adults. L. ehrenbergii showed the opposite pattern. The study verifies feeding interlinkage within the mangrove-seagrass-coral reef continuum in Mafia Island by providing strong evidence of ontogenetic migration. Understanding these connections will enhance our ability to manage tropical seascapes, and highlights the need to include multiple habitats in marine protected areas.
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| 9. |
- Berkström, Charlotte, et al.
(författare)
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Ecological versatility and its importance for the distribution and abundance of coral reef wrasses
- 2012
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 461, s. 151-163
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Tidskriftsartikel (refereegranskat)abstract
- Ecological versatility, the degree to which organisms fully exploit the available resources, is an important component of ecological and evolutionary theory. However, patterns and consequences of versatility in coral reef fish have received little attention. Using a comparative approach, this study tested the consequences of ecological versatility on the distribution and abundance of juvenile wrasses (family: Labridae) in Kimbe Bay, Papua New Guinea. Resource use was examined along 4 different resource axes (horizontal distribution or reef zone, vertical distribution or depth, microhabitat and diet). Stepwise multiple regressions were used to test for relationships between niche breadth and patterns of abundance and distribution. Most exhibited a degree of apparent specialisation on at least one resource, but none were specialised along all resource axes. In terms of juvenile diet, the majority of species exhibited a high reliance on harpacticoid copepods. Microhabitat specialisation was associated with low local abundance and narrow distribution among depth zones. However, diet and macrohabitat specialisation were poor predictors of local abundance, and no relationships between local abundance, and local and regional distribution were observed. We conclude that the relationship between versatility and abundance/distribution is dependent on the resource in question. A greater understanding of the degree of ecological versatility in relation to different resources is necessary to predict how reef fishes will respond to escalating human impacts on coral reefs.
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| 10. |
- Bonaglia, Stefano, et al.
(författare)
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Effect of reoxygenation and Marenzelleria spp. bioturbation on Baltic Sea sediment metabolism
- 2013
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Ingår i: Marine Ecology Progress Series. - : Inter Research. - 0171-8630 .- 1616-1599. ; 482, s. 43-55
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Tidskriftsartikel (refereegranskat)abstract
- Nutrient reduction and the improvement of bottom water oxygen concentrations are thought to be key factors in the recovery of eutrophic aquatic ecosystems. The effects of reoxygenation and bioturbation of natural hypoxic sediments in the Baltic Sea were studied using a mesocosm experiment. Anoxic sediment box cores were collected from 100 m depth in Kanholmsfjärden (Stockholm Archipelago) and maintained in flow-through mesocosms with 3 treatments: (1) hypoxic: supplied with hypoxic water; (2) normoxic: supplied with oxic water; and (3) Marenzelleria: supplied with oxic water and the polychaete Marenzelleria spp. (2000 ind. m–2). After a 7 wk long conditioning period, net fluxes of dissolved O2, CH4, Fe2+, Mn2+, NH4+, NO2-, NO3-, PO43- and H4SiO4, and rates of nitrate ammonification (DNRA), denitrification and anammox were determined. Phosphate was taken up by the sediment in all treatments, and the uptake was highest in the normoxic treatment with Marenzelleria. Normoxic conditions stimulated the denitrification rate by a factor of 5. Denitrification efficiency was highest under normoxia (50%), intermediate in bioturbated sediments (16%), and very low in hypoxic sediments (4%). The shift from hypoxic to normoxic conditions resulted in a significantly higher retention of NH4+, H4SiO4 and Mn2+ in the sediment, but the bioturbation by Marenzelleria reversed this effect. Results from our study suggest that bioturbation by Marenzelleria stimulates the exchange of solutes between sediment and bottom water through irrigation and enhances bacterial sulfate reduction in the burrow walls. The latter may have a toxic effect on nitrifying bacteria, which, in turn, suppresses denitrification rates.
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