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- Albertsson, Jan, 1959-, et al.
(författare)
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Deposit-feeding amphipods (Monoporeia affinis) reduce the recruitment of copepod nauplii from benthic resting eggs in the northern Baltic Sea
- 2001
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Ingår i: Marine Biology. - Umea Univ, Dept Ecol & Environm Sci, S-90187 Umea, Sweden. Umea Univ, Umea Marine Sci Ctr, S-90187 Umea, Sweden. : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 138:4, s. 793-801
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally investigated the effect of different densities of the burrowing, deposit-feeding amphipod Monoporeia affinis on the recruitment of zooplankton from benthic resting eggs. Intact sediment cores with in situ density and species composition of zooplankton resting eggs and benthic fauna were collected in the northern Bothnian Sea, part of the Baltic Sea. We removed as many M, affinis as possible from the cores and then added different numbers of ill. affinis to the cores to generate a range of densities. The cores were exposed to different densities of M. affinis for either 3 or 40 days, after which the hatched zooplankton was registered. One subset of the cores were initially incubated under low temperature (2-3 degreesC, to prevent hatching) for 37 days (the resting phase), to allow for effects of M. affinis on unhatched resting eggs. These cores were then incubated under higher temperature (13 degreesC) for 3 days (the hatching phase), to induce hatching and allow for effects on hatching or hatched specimens. In a second subset of cores with the same time and temperature schedule, the M. affinis density was experimentally reduced at the start of the hatching phase, to evaluate the effect of M. affinis during the hatching phase. To a third subset of cores, we immediately initiated the hatching phase, without an experimental resting phase, to evaluate the effects induced during the resting phase. The most common zooplankton species that hatched was Eurytemora affinis (Copepoda), followed by Bosmina longispina maritima (Cladocera). In all cores that were subjected to a resting phase, the numbers of hatched E. affinis were log-linearly negatively related to density of M. affinis. An increase of M. affinis density from 1,000 to 5,000 individuals m(-2), normal field densities, reduced the hatching by 60-70%. The negative impact was mainly exerted during the hatching phase, suggesting predation on, burial of or physical injury of hatching nauplii or eggs in a late development stage as likely mechanisms. Also, the number of B. longispina maritima that hatched was reduced by M. affinis during the hatching phase, but no clear relation to density of M. affinis could be identified. The results show that M. affinis can reduce recruitment to zooplankton from benthic resting eggs. Such impact by the benthos on resting stages of zooplankton is therefore a potentially significant link between the benthic and pelagic systems.
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- Albertsson, Jan, 1959-, et al.
(författare)
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Impact of a borrowing deposit-feeder, Monoporeia affinis, on viable zooplankton resting eggs in the northern Baltic Sea
- 2000
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Ingår i: Marine Biology. - Umea Univ, Dept Ecol & Environm Sci, S-90187 Umea, Sweden. : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 136:4, s. 611-619
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the effect of different densities of the burrowing deposit-feeding amphipod Monoporeia affinis on the potential for recruitment of zooplankton from benthic resting eggs. Hatching of resting eggs was induced in the laboratory on sliced and resuspended 1-cm depth-sections of sediment cores, collected at six stations ill an archipelago area of the Gulf of Bothnia, Baltic Sea. The uppermost 5 cm of the sediment was studied. The most common species that hatched was Eurytemor affinis (Copepoda). Individuals from another copepod genus, Acartia, hatched in significant numbers only in the cores from two stations with low amphipod abundance. Cores from stations with high amphipod densities showed a deeper distribution of emerging E. affinis nauplii compared with stations with few amphipods: the oxidised sediment layer was also deeper at high M. affinis densities than at low. Total (0 to 5 cm strata pooled) number of hatched E. affinis nauplii was independent of amphipod density. This indicates that the effect of M. affinis on E. affinis eggs involves deeper burial due to bioturbation, rather than predation. Decreased benthic recruitment of zooplankton at localities with high M. affinis density is suggested, since more deeply positioned eggs are less likely to hatch. When hatching was induced in intact, non-sliced cores from one station, the number of E. affinis nauplii that hatched was on average 43% of the number that hatched in the upper centimetre of the sliced cores from the same station. This fraction (43%), if applied to the other stations, implied a potential for benthic recruitment of up to 80000 ind m(-2) for E. affinis. Due to its high abundance, M. affinis is likely to greatly reduce benthic recruitment of zooplankton in this system.
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| 3. |
- Aljetlawi, A A, et al.
(författare)
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Effect of food and sediment pre-treatment in experiments with a deposit-feeding amphipod, Monoporeia affinis
- 2000
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Ingår i: Journal of Experimental Marine Biology and Ecology. - Umea Univ, Dept Ecol & Environm Sci, SE-90187 Umea, Sweden.. - 0022-0981 .- 1879-1697. ; 249:2, s. 263-280
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally investigated the effects of different pre-treatments of the sediment, and the effect of daily addition of fresh phytoplankton, on the growth and survival of 1-year-old (1 +) individuals of the deposit feeder Monoporeia affinis (Amphipoda). We used three different types of sieved sediment: pre-frozen muddy clay, non-pre-frozen muddy clay, and fine sand. The muddy clay contained phytoplankton originating from the surface sediment sampled in the field during the late spring bloom. No phytoplankton was initially present in sand. The experiment lasted for 18 days. M. affinis responded to the daily phytoplankton addition by increasing growth. Phytoplankton addition had no significant effects on the survival of M. affinis. Upon phytoplankton addition, the sandy and non-frozen muddy clay gave similar growth and survival responses. In contrast, the pre-frozen sediment resulted in significantly lower growth and survival. The growth was negative in all treatments without phytoplankton. Thus, the high initial chlorophyll content in the muddy clay was not of sufficient quality or concentration to allow a positive growth response in M. affinis. The growth of M. affinis was significantly correlated with the reduction of the chlorophyll. Our results indicated that M. affinis is capable of assimilating settled phytoplankton with no, or only a few days' time delay. (C) 2000 Elsevier Science BN: All rights reserved.
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- Kiviloog, Jaan, 1975, et al.
(författare)
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EN STUDIE AV SMOLTVANDRING MED RADIOTELEMETRI OCH STRÖMNINGSMODELLERING
- 2004
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Ingår i: Proceedings Hidroenergía 04, Falkenberg, Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A study on the effect of the flow field on downstream migration of smolts in a major northern Swedish river (Umeälv) is presented. The study comprises telemetric studies of downstream migrating smolts and three-dimensional computational fluid dynamics (CFD) studies of the flow. The CFD studies are validated with velocity data from field measurements with an Acoustic Doppler Profiler (ADP). The objective of this study is to determine the migration paths of salmon and trout smolts and relate these paths to the flow field. The results from the study can be used to improve smolt survival by taking appropriate measures to divert smolts from the turbines, e.g. by changing spill rules or installing bypass systems. Results from this telemetry show that the smolts move along the main stream of the river. Since this data only yield information on the smolt positions on a 2-dimensional plane it cannot directly be concluded whether the smolt migration is passive or active. Acomparison of the downstream migration speed of fish with the water velocities in the upper water column indicates that the downstream migration is passive.
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| 9. |
- Kiviloog, Jaan, 1975, et al.
(författare)
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Hydraulic modelling and validation for the study of smolt migration
- 2004
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In order to assess the prerequisites for downstream migration of smolt the flow field upstream two hydropower stations in two large Swedish rivers have been made, and the simulations have been validated against stream velocities measured on site. The validated models have been used to compare the flow paths with the measured swimming paths of smolts. The simulations were done by solving the three dimensional Reynolds-averaged Navier-Stokes equations using the Fluent computational fluid dynamics (CFD) package. One of the studied rivers, Ume älv, whose main course is completely regulated, has a large unregulated tributary river, Vindelälven, which holds important spawning grounds for salmon (Salmo salar) and trout (Salmo trutta), and downstream of the confluence of the two rivers there is only one hydropower plant, the Stornorrfors power plant. This constitutes a major hindrance for fish migrating between the Bothnian Sea and the spawning grounds of the river Vindelälven. The juvenile fish, smolt, leaving the Vindelälven downstream towards the ocean can migrate either through the turbines and deep rock tunnels of the power plant or through the surface weirs at the regulating dam. Because of the flow regime during the migration period of smolts most smolts are believed to follow the main stream through the turbines leading to a mortality of approximately 25 %. The other studied river, Pite älv, also contain some spawning grounds in smaller tributaries upstream its first power plant. Although this plant is more like a-run-of-the-river plant most smolt passes the turbines instead of going over the spillways.The objective of the study is to determine the migration paths of salmon and trout smolts and relate their behaviour to hydraulic factors. The results from the study could then be used to improve smolt survival by taking appropriate measures to divert the smolts from the turbines, e.g. by changing spill rules or installing diversion systems.In Ume älv in Spring 2002, 22 salmon and 22 trout smolts were tagged with internal, individually coded radio transmitters (ATS). After the release approximately five kilometres upstream of the dam at Stornorrfors power plant their passages were registered at three stationary recorders and their movements tracked manually in the horizontal plane along their swimming paths. Simultaneously, velocity profiles were measured in selected cross-sections using an Acoustic Doppler Profiler (ADP). In spring 2003 16 smolt were tagged, released and tracked in the same way in Pite älv. In 2004 also the swimming depth was recorded.Results from the tracking, flow measurements and flow simulation indicate that the smolts move along the main stream of the river. In Ume älv the tracking data only yielded information on the smolt positions in the horizontal plane but it was found that the water velocities in the upper part of the water column along the smolts migration paths were close to the mean transport velocity of the smolt. In Pite älv Spring 2004 the swimming depth was measured to between 0.5 to 2 m below the surface. It can thus be concluded that the smolt migration is passive i.e. the smolt drift passively with the water.This study is part of a more extensive project that comprises studies of both upstream and downstream migration of fish. The objective of the project is to study the correlation between flow hydraulics and fish migratory behaviour. The ultimate goal is to create numerical fish models that are programmed to act as real fish in the CFD model. To get realistic models it is then first necessary to map real fish migratory behaviour to get to know the rules of the fish behaviour.
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