| 1. |
- Aarestrup, K., et al.
(författare)
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Survival and progression rates of anadromous brown trout kelts Salmo trutta during downstream migration in freshwater and at sea
- 2015
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 535, s. 185-195
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Tidskriftsartikel (refereegranskat)abstract
- The marine migration of post-spawning anadromous fish remains poorly understood. The present study examined survival and progression rates of anadromous brown trout Salmo trutta L. after spawning (kelts) during downriver, fjord, and sea migration. Kelts (n = 49) were captured in the Danish River Gudenaa, tagged with acoustic transmitters and subsequently recorded by automatic receivers. Kelts spent on average 25 d moving down the 45 km river and through the brackish fjord. The fish entered the Kattegat Sea between 14 April and 30 May. Eighteen of the 49 kelts disappeared in the river and fjord during outward migration, likely due to mortality. Survival was not significantly related to gill Na+/K+-ATPase activity, suggesting that physiological adaptation to saltwater may be less critical for adults compared to juveniles (smolts). Of the 31 fish that entered the Kattegat Sea, 45% survived and returned to the fjord. The duration of the entire marine migration, from leaving to entering the river, was on average 163 d. The fish returned from the Kattegat Sea to the fjord between 22 July and 21 October. Upon return, the fish spent 1-90 d passing through Randers Fjord, with most individuals completing the reach within 4 d, suggesting that the kelts spent limited time foraging after returning to the fjord. The total survival during the entire marine migration, including the fjord, was a minimum of 29%. Our study provides data that are important for management of anadromous brown trout, and the high survival highlights that kelts may represent a valuable resource for both population reproduction and recreational fisheries.
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| 2. |
- Aldvén, David, 1986, et al.
(författare)
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Migration speed, routes, and mortality rates of anadromous brown trout Salmo trutta during outward migration through a complex coastal habitat
- 2015
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 541, s. 151-163
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about migratory routes and habitat use of anadromous brown trout Salmo trutta at sea. We therefore conducted a 2 yr study (2011-2012) on sea trout in the River Himlean system (a river, an estuary, and a coastal sea environment) in western Sweden. The main objectives were to investigate migration speed, migration routes, and mortality both for adult brown trout returning to the sea (kelts) and smolts (generally 2 yr old trout migrating to the sea for the first time). Brown trout were captured and tagged with hydro-acoustic transmitters, after which they were released and monitored during their initial migration. Migration was primarily nocturnal in the river and estuary, whereas no tendency for nocturnal migration was observed along the coast. Migration speed tended to decrease as individuals progressed from the river through the estuary and along the coast, and we found no differences in absolute migration speed between kelts and smolts. Smolts and kelts showed similar mortality. Mortality during the initial part of the migration ranged between 5 and 51% and was significantly higher in 2011, for both smolts and kelts. Our study is the first to compare migratory patterns and mortality rates between sea trout kelts and smolts during the transition from freshwater into an open coastal system.
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| 3. |
- Alegria Zufia, Javier, Ph.D. 1992-, et al.
(författare)
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Growth and mortality rates of picophytoplankton in the Baltic Sea Proper
- 2024
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Ingår i: Marine Ecology Progress Series. - : Inter-Research. - 0171-8630 .- 1616-1599. ; 735, s. 63-76
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Tidskriftsartikel (refereegranskat)abstract
- Picophytoplankton (<2 m diameter), a diverse group of picocyanobacteria and photosynthetic picoeukaryotes, are significant contributors to primary production. Predatory mortality controls picophytoplankton biomass and thereby energy transfer in the marine food web. The 2 major pathways of picophytoplankton mortality are grazing and viral lysis. Grazing passes carbon directly to higher trophic levels, while lysis products are passed into the viral loop. Picophytoplankton are abundant in the Baltic Sea but little is known about their predatory mortality. Using a modification of the dilution approach, we calculated growth and mortality rates of picophytoplankton and studied the effect of predation on community structure during late August and September. The experiments were conducted coinciding with the peak in picophytoplankton abundance (similar to 10(5) cells ml(-1)) at the Linnaeus Microbial Observatory in the Baltic Sea Proper. The results showed that grazing is an important controller of picocyanobacteria and photosynthetic picoeukaryote populations, while no significant viral lysis effect was detected. Grazing on picocyanobacteria was proportional to growth rates, while grazing on photosynthetic picoeukaryotes exceeded growth. Selective grazing of phylogenetically distinct picocyanobacterial clades had a significant effect on community structure, suggesting that grazing has an impact on the seasonal dynamics of co-occurring clades. Picocyanobacteria had a higher carbon transfer contribution to higher trophic levels than photosynthetic picoeukaryotes at the time of the experiments. The study shows that picophytoplankton are important contributors to carbon cycling in the Baltic Sea microbial food web and should be considered for future ecological models.
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| 4. |
- 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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| 5. |
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| 6. |
- Andersson, Agneta, et al.
(författare)
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Release of aminoacids and inorganic nutrients by heterotrophic marine microflagellates
- 1985
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Ingår i: Marine Ecology Progress Series. - 0171-8630 .- 1616-1599. ; 23, s. 99-106
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Tidskriftsartikel (refereegranskat)abstract
- Heterotrophic microflagellates isolated from the Baltic Sea and grown under laboratoryconditions were shown to release dissolved free amino acids (DFAA) when grazing bacteria. Flagellatesreleased 3H-amino acids when fed 3H-leucine-labelled bacteria, and concentrations of aminoacids increased in the experimental medium. Serine showed a strong positive correlation withflagellate feeding. Aspartic acid, glutamic acid and ornithine also increased more than other aminoacids. During consumption of bacteria, the flagellates released 13% of the ingested nitrogen asammonia, and 30 % of the ingested phosphorus as phosphate. In a field experiment off Scripps Pier, wemeasured bacterial production, flagellate abundance, and concentration of DFAA over a 28 h period.The concentration of DFAA showed a covariation with the flagellate numbers. Results from our fieldand laboratory experiments suggest that flagellates may be a source of DFAA in the sea.
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| 7. |
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| 8. |
- Andersson, Agneta, et al.
(författare)
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Vertical transport of lipid in seawater
- 1993
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 98:1-2, s. 149-155
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Tidskriftsartikel (refereegranskat)abstract
- Lipids in seawater act as solvents and transporters of lipophilic organic pollutants. To investigate a possible transport route of lipophilic pollutants, the vertical flux of lipid was quantified during an annual cycle in the northern Baltic Sea. The lipid content in both sedimenting material and different size fractions of seawater was analyzed. During the year, 8 g lipid m-2 sedimented out from the photic zone to the benthic system. The sedimentation of lipid accounted for 300 to 400 % of the average standing stock of pelagic lipid and was concentrated in the spring bloom period (April-June) when 70 % of the total lipid sedimentation occurred. About 30 % of the produced pelagic lipid settled out from the system. In seawater the lipid maximum occurred at the end of the spring bloom, shortly after nutrient depletion, indicating a stress response in the algae. Since lipid sedimentation is concentrated in the spring bloom, removal of lipophilic organic pollutants may be important during this period.
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| 9. |
- Andre, C., et al.
(författare)
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Predation on Settling Bivalve Larvae by Benthic Suspension Feeders - the Role of Hydrodynamics and Larval Behavior
- 1993
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 97:2, s. 183-192
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Tidskriftsartikel (refereegranskat)abstract
- Predation by the suspension-feeding infaunal bivalve Cerastoderma edule on settling C. edule larvae was studied in a flume boundary-layer flow. The density of settled larvae was reduced by 33% in an area of 5 cm2 enclosing individual adults. Mean survival time for competent C. edule larvae drifting over sediment populated with feeding adults (380 ind. m-2) was 64 s, and 75% of the observed larvae were inhaled by adults. Observations of the siphonal currents produced by C. edule and the swimming behaviour of larvae were combined in a computer model to assess the importance of adult density and boundary-layer flow on the predation risk experienced by settling larvae. Survival of settling larvae decreased drastically with increasing adult density, whereas increased flow velocity caused only a slightly higher predation risk. Although reduction in larval settlement on the scale of individual adults may be small or moderate, inhalation of settling larvae by populations of resident suspension feeders may cause a significant decrease in settlement on a larger scale (10(1) to 10(3) m).
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| 10. |
- 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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