| 1. |
- Angeler, David
(författare)
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Effects of shrimp-farm effluents on the food web structure in subtropical coastal lagoons
- 2011
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 402, s. 65-74
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Tidskriftsartikel (refereegranskat)abstract
- Although numerous studies have reported the negative effects of shrimp aquaculture on water quality, little is known about the ecological effects of these practices in coastal lagoons and near-shore marine habitats. The impact of shrimp-farm effluents on the food webs of an impacted subtropical coastal lagoon in the Gulf of California was evaluated through measurements of isotopic (delta C-13, delta N-15) signatures in sediments, plants and animals, and compared with the results of a near-pristine reference site. Degradation was manifested in a strong reduction on fish diversity at the perturbed site. delta C-13 signatures provided ambiguous evidence of degradation while delta N-15 was a better descriptor of shrimp-farm effluent impact on coastal lagoon food webs. The site receiving nutrient-rich discharges showed significant enrichment of delta N-15 (approximate to 5 parts per thousand) in sediments, macroalgae, benthic algae, filterfeeders and omnivorous feeders, resulting in qualitative differences in foodweb structure between both lagoons. The food web in the perturbed site was sustained by sediment detritus and dominated by opportunistic species. The lowest influence on delta N-15 signatures by aquaculture discharges recorded in the upper trophic levels could be explained by the shift in the composition of biotic communities, and associated feeding strategies. While alterations in resource availability do not affect directly food chain length, trophic linkages between food web compartments can be reduced as a result of shrimp farm impacts. Our study demonstrates that nutrient-enriched discharges from shrimp-farm aquaculture generate changes in the availability of food sources, which reduce biodiversity and alter structural and functional food web characteristics. (C) 2011 Elsevier B.V. All rights reserved.
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| 2. |
- Berkström, Charlotte, et al.
(författare)
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Trade-offs in the ecological versatility of juvenile wrasses : An experimental evaluation
- 2014
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 453, s. 91-97
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Tidskriftsartikel (refereegranskat)abstract
- A number of theories have been advanced to explain the evolution of specialists and generalists and how they coexist. According to trade-off theory, a species can improve performance by specialising on one habitat but does so at a cost of reduced performance in others. Specialists will outperform generalists in their preferred habitats but will be outperformed by generalists in other habitats. This study aimed to examine trade-offs in juvenile coral reef wrasses that vary in their degree to which they are specialised on microhabitats. We predicted that specialists would exhibit highest survival and growth on preferred habitats, and in contrast, generalists would tend to do equally well on all habitats. Furthermore, we predicted that specialists would outperform generalists on their preferred habitat, while generalists would outperform specialists on less preferred habitats. The predictions were tested by transplanting juveniles from four different species (two specialists, and two generalists) to patch reefs constructed from different kinds of microhabitats (live coral, dead coral, and rubble) and measuring growth and survival after 3 weeks in Kimbe Bay, Papua New Guinea. Prior to this, the degree of specialisation was assessed using resource selection ratio-based field observations of habitat use and availability. Results provided mixed evidence for the trade-off hypothesis. Specialists conformed to predictions, while generalists did not. Specialist species showed higher survival rate on their preferred habitat than generalist species and the mean growth was significantly higher on the preferred habitat than less preferred habitats for one specialist species. However, generalist species did not survive on all reefs, regardless of microhabitat Growth rates between habitats could therefore not be compared for generalists and the presence of a trade-off in fitness expressed in growth may have been missed for these species. It is thus premature to reject the trade-off theory, and we encourage examining a greater range of specialist and generalist species, under conditions in which the fate of all individuals can be more accurately determined.
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| 3. |
- Carlsson, Per, et al.
(författare)
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Bacterial and phytoplankton nutrient limitation in tropical marine waters, and a coastal lake in Brazil
- 2012
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 418, s. 37-45
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Tidskriftsartikel (refereegranskat)abstract
- Bioassay experiments were performed two times (with 2 years in between) in order to investigate if nitrogen (N, ammonium), phosphorus (P, phosphate) and carbon (C, glucose) additions would stimulate the growth of bacteria and phytoplankton differently in three different tropical aquatic environments. The water and their indigenous microbial communities were taken from a freshwater coastal lake (Cabiunas), a coastal (Anjos), and an offshore marine station (Sonar) in the Atlantic outside Cabo Frio, Rio de Janeiro State, Brazil. Ammonium, phosphate and glucose were added alone or in combination to triplicate bottles. In the lake, P seemed to be the primary limiting factor during the first experiment, since both bacterial production and phytoplankton growth was stimulated by the P addition. Two years later, however, addition of P inhibited phytoplankton growth. During both years, C was closely co-limiting for bacteria since CP additions increased the response considerably. For both the coastal and offshore seawater stations, phytoplankton growth was clearly stimulated by N addition in both years and the bacteria responded either to the P, N or C additions (alone or in combination). To conclude, the results from these tropical aquatic systems show that it is possible that phytoplankton and bacteria may compete for a common resource (P) in lakes, but can be limited by different inorganic nutrients in marine waters as well as lakes, suggesting that phytoplankton and bacteria do not necessarily compete for the same growth limiting nutrient in these environments. (C) 2012 Elsevier B.V. All rights reserved.
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| 4. |
- Engstedt, Olof, 1980-, et al.
(författare)
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Strontium (Sr) uptake from water and food in otoliths of juvenile pike (Esox lucius L.)
- 2012
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 418-419, s. 69-74
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Tidskriftsartikel (refereegranskat)abstract
- The strontium (Sr) or Sr:Ca ratio in otoliths has been widely used in the last decade to describe the migration histories of fish between fresh and marine waters. However, reference experimental studies of particular species and waters are necessary to confirm the underlying assumptions and evaluate the applicability of this tool to field data. Laboratory experiments indicated that juvenile, anadromous pike (Esox lucius L) from the Baltic Sea reared in successively increasing salinities (from 0 to 7 parts per thousand) for 110 d accumulated Sr in their otoliths according to a positive relationship with waterborne Sr. When the pike were given prey fish from brackish (7 parts per thousand) environments, the otolith Sr:Ca ratio increased more than in fish given prey from freshwater lakes. Pike held at constant salinity (7 parts per thousand) and given prey fish from the same salinity environment had an Sr:Ca ratio of 6.9 x 10(-3). The ratio decreased successively for fish given prey from freshwater (4.4 x 10(-3)) or kept in freshwater and given food from brackish water (3.1 x 10(-3)). Fish exposed to freshwater and given prey fish from freshwater displayed no increase in Sr:Ca ratio (1.6 x 10(-3)). The experiments demonstrated that the Sr:Ca ratio may be used to describe the migration history of pike between rivers and the Baltic Sea. The maximum Sr:Ca value for pike given marine-origin food corresponded to those of fish collected from the Baltic Sea.
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| 5. |
- Hedman, Jenny E., et al.
(författare)
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Particle reworking and solute transport by the sediment-living polychaetes Marenzelleria neglecta and Hediste diversicolor
- 2011
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 407:2, s. 294-301
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Tidskriftsartikel (refereegranskat)abstract
- This experimental study quantified and compared particle-mixing and solute transport by the polychaetes Marenzelleria neglecta (2 g ww, 3200 ind.m(-2)) and Hediste diversicolor (2 g ww, 800 ind.m(-2)) in Baltic Sea sediments. Particle tracers (luminophores) were added to the sediment surface and their vertical distribution in the sediment was measured after 10 d. The rate of particle mixing was quantified using a gallery-diffusion model calculating the biodiffusion coefficient D(b) and the non-local transport parameter r. Bioirrigation was measured by adding an inert solute tracer (bromide) to the overlying water 1, 1.5 and 2 d before the end of the experiment, and quantified by calculating the net bromide flux and fitting the bromide profiles to a 1D diffusion model providing an apparent biodiffusion coefficient D(a). The two polychaete worms displayed similar particle-mixing and solute transport efficiencies (based on total biomass) despite different modes of bioturbation. However, H. diversicolor was a more efficient particle-reworker and M. neglecta a more efficient bioirrigator, on an individual level. H. diversicolor buried a higher percentage (13%) of luminophores below the top 0.5 cm surface layer than M. neglecta (6%). D(b) did not differ between the two species (2.4 x 10(-3) cm(2) d(-1)) indicating a similar rate of diffusive mixing of the top sediment, however, the non-local transport parameter r was 2.5 y(-1) for H. diversicolor and zero for M. neglecta, suggesting no significant particle-transport below the biodiffusive layer by M. neglecta. The average individual net bromide fluxes obtained were ca. 0.01 mL min(-1) for H. diversicolor and 0.003 mL min(-1) for M. neglecta, corresponding to an area-specific rate of ca. 12 L m(-2) d(-1) at the used densities. D(a) did not differ between the two polychaetes, suggesting a higher individual solute exchange efficiency of M. neglecta considering the much higher ventilation rates reported for H. diversicolor than for Marenzelleria sp. The ongoing colonization of Baltic Sea sediments by M. neglecta at high densities may thus lead to an enhanced soluble release of both nutrients and contaminants. These results add information to the understanding of the potential effects of the invasion of M. neglecta on sediment biogeochemistry when competing with and/or replacing native species.
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| 6. |
- Hylander, Samuel, et al.
(författare)
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UV protective compounds transferred from a marine dinoflagellate to its copepod predator
- 2010
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 389:1-2, s. 38-44
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Tidskriftsartikel (refereegranskat)abstract
- Planktonic organisms living in surface waters can be exposed to harmful levels of ultraviolet radiation (UVR), but few studies have examined accumulation of UV protective compounds in marine zooplankton. Zooplankters are suggested to lack the ability to synthesize these substances and hence must accumulate them from their algal food. Here, we show that both phytoplankton (dinoflagellates) and their zooplankton grazers (copepods) respond strongly to UVR exposure by, respectively, synthesizing and accumulating the natural sunscreens mycosporine-like amino acids (MAAs). In our experiment, the MAAs content increased approximately four times in dinoflagellates exposed to UVR and PAR, as compared to non-UVR controls only receiving PAR (PAR = photosynthetically active radiation). The elevated MAAs level in the dinoflagellates was mirrored in the copepods, which accumulated more MAAs when exposed to UVR as compared to a non-UVR treatment. Overall, copepods accumulated approximately 2-5% of the total MAAs pool. Other UV protective compounds, like carotenoids, were however not accumulated by the copepods. The ability of some species to produce or accumulate photoprotective compounds may lead to increased fitness, and thus these taxa may become more dominant in plankton communities. (C) 2010 Elsevier B.V. All rights reserved.
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| 7. |
- Lefébure, Robert, et al.
(författare)
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Temperature and size-dependent attack rates of the three-spined stickleback (Gasterosteus aculeatus) : are sticklebacks in the Baltic Sea resource-limited?
- 2014
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 451, s. 82-90
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Tidskriftsartikel (refereegranskat)abstract
- The three-spined stickleback Gasterosteus aculeatus is a small omnivorous fish, widely distributed in the northern hemisphere. In the Baltic Sea, recently observed increases in their population densities have been attributed to declines of piscivorous predators. Concurrent with this predator release, an alternative hypothesis is that past and present consumption rates and resource limitation thresholds may have contributed to the recent increases in stickleback abundance. To evaluate this hypothesis, we estimated the size- and temperature-dependent attack rate and the critical resource density (CRD) of three-spined sticklebacks. We incorporated laboratory results with time series of zooplankton abundance to estimate historical trends in degrees of resource limitation in sticklebacks and evaluate if increases in individual consumption rates could be a plausible mechanism facilitating the suggested population increase. Attack rates increased with body size and temperature in laboratory experiments. Estimated CRD increased with size but decreased with temperature, suggesting that stickleback scope for individual and population growth might increase at temperatures above 15 degrees C. Our results further suggest that sticklebacks have been living closer to maximum consumption capacity in the coastal areas of the Bothnian Sea (BS) and Bothnian Bay (BB). Moreover, decreasing levels of resource limitation in the corresponding off-shore zones may have facilitated increases in stickleback densities for these areas. However, in the coastal zones of the Baltic proper (BP), resource levels have declined and are approaching the CRD, suggesting that stickleback populations in BP may not increase further. The decrease in CRD with temperature implies that increasing summer temperatures will increase the scope of individual and population growth in the three-spined stickleback and may favor the three-spined stickleback's competitive ability over other species under a warmer climate. (C) 2013 Elsevier B.V. All rights reserved.
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| 8. |
- Meunier, Cedric Leo, et al.
(författare)
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Impact of swimming behaviour and nutrient limitation on predator-prey interactions in pelagic microbial food webs
- 2013
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 446, s. 29-35
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Tidskriftsartikel (refereegranskat)abstract
- Heterotrophic dinoflagellates are motile protozoans, important consumers of phytoplankton in aquatic environments. Motility is a main advantage for predators during grazing activities, but can also serve as defence mechanisms against being grazed. Thus, numerous microalgal species are also motile. We hypothesise that the nutrient status of an organism affects its swimming speed and especially that nutrient limitation has a negative impact on cell motility. Such altered motility of both predator and prey should influence feeding success of grazers. We tested those hypotheses by investigating the impact of nutrient (phosphorus) limitation on motility of two algal species, Rhodomonas sauna and Teleaulax sp., and the heterotrophic dinoflagellate Oxyrrhis marina and examined how differences in prey swimming speed affect grazing of O. marina. We show that nutrient limitation had a strong impact, reducing algal swimming speed and escape success and in turn significantly influencing food uptake of O. marina which was maximal for intermediate prey swimming speed. We also tested the importance of algal behaviour on O. marina selective feeding and observed that Teleaulax sp. presented an escape behaviour, which appeared to be an effective defence mechanism against grazing of O. marina. While this study has focused on the trophic interactions between two algal species and one dinoflagellate, the impact of nutrient limitation and escape strategy on feeding success of the predator is likely to be found in the whole range of plankton trophic interactions.
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| 9. |
- Vehmaa, Anu, et al.
(författare)
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How will increased dinoflagellate:diatom ratios affect copepod egg production? : a case study from the Baltic Sea
- 2011
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 401:1-2, s. 134-140
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Tidskriftsartikel (refereegranskat)abstract
- Mild winters are modifying the plankton spring bloom composition so that diatoms are decreasing and dinoflagellates increasing. We used two common spring bloom phytoplankton species, a diatom and a dinoflagellate to study the effects of changing bloom composition on the reproduction of the calanoid copepod Acartia bifilosa Giesbrecht, a dominant species in the northern Baltic Sea. Egg production was significantly higher when copepods were fed with Scrippsiella hangoei (Schiller) Larsen dinoflagellates or a mixture of Scrippsiella and Skeletonema marinoi Sarno and Zingone diatoms than when they were provided with Skeletonema only. This effect was observed despite the fact that the Skeletonema strain did not produce polyunsaturated aldehydes (PUAs) and its nutritional quality was high according to polyunsaturated fatty acid (PUFAs) and sterol measurements, and moderate according to mineral (C:N and C:P) measurements. When offered mixtures of Skeletonema and Scrippsiella, copepods ingested both, even when the other one was rare. This indicates potential positive effect of multispecies diets not verified in this study. Here we show that increasing dinoflagellate:diatom ratio might have a positive effect on copepod reproduction.
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| 10. |
- Waldeck, Peter, et al.
(författare)
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Effects of winter water temperature on mass loss in Baltic blue mussels : Implications for foraging sea ducks
- 2013
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 444, s. 24-30
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Tidskriftsartikel (refereegranskat)abstract
- Water temperature may through its effects on body mass, reproductive output and recruitment of bivalves also influence organisms higher up the food chain. The small sized Baltic blue mussel (Mytilus trossulus × Mytilus edulis) is a dominant key species in the Baltic Sea food web and it is an important food source for sea ducks such as the common eider (Somateria mollissima) and the long-tailed duck (Clangula hyemalis) and for some species of fish. Possible links between winter water temperature and the quality of blue mussels as food for wintering sea ducks were investigated by measuring the soft body mass loss of mussels during winter in an experimental set-up and in the field. Results demonstrated that warmer water temperatures in winter had a significant negative effect on soft body mass of Baltic blue mussels. Analysed mussels, on average 15 mm in length, kept in experimental aquaria between January and March and exposed to a 3.6 °C elevated water temperature regime corresponding to conditions during mild winters, had about 11% smaller tissue dry mass in March than mussels exposed to a water temperature regime corresponding to conditions in cold winters. At two field study areas, the body mass loss of mussels from October to March in a mild winter was significant and more pronounced (15% and 19%, respectively) than in a cold winter (11% and 4% respectively). This difference is of importance because in winter and spring, sea ducks build up energy stores for the subsequent breeding season by consuming large quantities of blue mussels and the energy gain of the birds per dive will be affected by the soft body tissue content of the mussels. The results improve our possibilities to predict the seasonal and yearly variation of the quality of the main food of sea ducks and help us to better understand the causes for the variable reproductive success and the present population declines of sea ducks. The results may also improve our possibilities to model the effects on Baltic Sea food webs of possible future increases in water temperature.
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