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| 2. |
- 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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| 5. |
- Albertsson, Jan, 1959-
(författare)
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Trophic interactions involving mysid shrimps (Mysidacea) in the near-bottom habitat in the Baltic Sea
- 2004
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Ingår i: Aquatic Ecology. - Cty Adm Board Vasterbotten, S-90186 Umea, Sweden.. - 1386-2588 .- 1573-5125. ; 38:3, s. 457-469
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Tidskriftsartikel (refereegranskat)abstract
- In a six month mesocosm tank experiment, hypotheses were tested concerning the role of benthopelagic mysid shrimps (Mysidacea) in the near-bottom food web of the Bothnian Sea, in the northern Baltic Sea. The first hypothesis tested was that the mysids interact, through predation, with benthic deposit-feeding Monoporeia affinis amphipods. A second hypothesis tested was that the sediment type is important for the overwintering success of the mysids. Changes in abundance and mass were recorded for M. affinis and mysids when separate and when coexisting, in two sediment types differing in organic content (food level); soft muddy clay (rich) and fine sand (poor). Despite the fact that newborn M. affinis offspring, a plausible target for predation by mysids, were present in substantial numbers in the tanks, no consistent evidence for any interaction between these taxa was found. The biomass of mysids was slightly higher in the muddy clay than in the sand tanks, and the mechanism behind this substrate effect is discussed. A third hypothesis, that the mysids interact with near-bottom zooplankton, was investigated. The tanks were continually supplied with in situ near-bottom sea-water containing a seminatural assemblage of near-bottom plankton. As a result of mysid predation, tanks with mysids had lower abundance and biomass of cyclopoid copepods than tanks without mysids. Thus, the major interaction found was predation on near-bottom zooplankton by mysids and it is suggested that this interaction could potentially be an important food link, especially during periods with low food availability in the pelagic system.
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| 7. |
- Albertsson, Jan, 1959-
(författare)
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Uppföljning av naturtypen 1140 blottade ler- och sandbottnar i Bottenviken och Södra Östersjön : En pilotstudie
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- En uppföljning av naturtyp blottade ler- och sandbottnar (naturtypskod 1140) i Södra Östersjöns och Bottenvikens vattendistrikt samt utvärdering av undersökningstypen för denna naturtyp har utförts i form av en pilotstudie under sommar-höst 2014. Arbetet har fokuserat på bottenfaunan i dessa grunda områden. Stora skillnader i mängd och artsammansättning hos bottenfaunan konstaterades mellan Södra Östersjön och Bottenviken. Totalt påträffades 34 och 13 taxa i Södra Östersjön respektive Bottenviken där endast två var gemensamma för bägge distrikten. Totala individantalen och biomassa var avsevärt högre i Södra Östersjön, samtidigt som variationen mellan prov var mindre där vilket gjorde att flera parametrar gav godtagbar precision. I Bottenviken var precisionen betydligt sämre p.g.a. stor variation mellan prov. Användning av 0,5 mm sållstorlek som alternativ i Bottenviken förbättrade flera parametrar något men sammantaget kanske inte tillräckligt för att motivera inkluderandet av detta i undersökningstypen i dagsläget. Ett flertal typiska och karakteristiska arter som finns listade i den svenska vägledningen för naturtypen påträffades i södra Östersjön, varav någon enstaka förekom frekvent och med en låg relativ variation som medförde god mätprecision. I Södra Östersjön hittades också en art som är ny för Sverige, märlkräftan Grandidierella japonica. I Bottenviken förekom inga listade typiska eller karakteristiska arter överhuvudtaget, och det finns därför ett behov av att se över listan över sådana arter. Det bör utredas framöver hur zonen för provtagning inom naturtyp 1140 bättre ska definieras då Östersjön i stort sett saknar tidvattenvariationer. Att särskilja en zon som upplever en lämplig frekvens och varaktighet av torrläggning bör vara ett viktigt mål för att kunna undersöka ett faunasamhälle som är karakteristiskt för naturtyp 1140. Sammantaget tyder resultaten på att undersökningstypen kan fungera relativt väl i Södra Östersjön med rimliga arbetsinsatser, när det gäller att ta fram momentanvärden av godtagbar precision för flera parametrar. För Bottniska viken däremot krävs betydligt större arbetsinsats för att åstadkomma detta, men i och med att typiska arter, och kanske andra lämpliga arter, saknas där är det tveksamt om det är lönt att öka insatserna i dagsläget. Framgången i framtida uppföljningar beror också starkt av storleken på den slumpmässiga variationen i tiden för faunan i naturtypen, men denna är okänd och har inte studerats i den aktuella pilotstudien.
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| 9. |
- 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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| 10. |
- Andersson, Agneta, et al.
(författare)
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Changes in the pelagic microbial food web due to artificial eutrophication
- 2006
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Ingår i: Aquatic Ecology. - Umea Univ, Dept Ecol & Environn Sci, Marine Ecol, SE-90187 Umea, Sweden. Umea Marine Sci Ctr, SE-91020 Hornefors, Sweden. Linkoping Univ, Dept Mol & Clin Med, Div Med Microbiol, SE-58185 Linkoping, Sweden. Univ Copenhagen, Bot Inst, DK-1353 Copenhagen K, Denmark. : Springer Science and Business Media LLC. - 1386-2588 .- 1573-5125. ; 40:3, s. 299-313
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Tidskriftsartikel (refereegranskat)abstract
- The effect of nutrient enrichment on the structure and carbon flow in the pelagic microbial food web was studied in mesocosm experiments using seawater from the northern Baltic Sea. The experiments included food webs of at least four trophic levels; (1) phytoplankton-bacteria, (2) flagellates, (3) ciliates and (4) mesozooplankton. In the enriched treatments high autotrophic growth rates were observed, followed by increased heterotrophic production. The largest growth increase was due to heterotrophic bacteria, indicating that the heterotrophic microbial food web was promoted. This was further supported by increased growth of heterotrophic flagellates and ciliates in the high nutrient treatments. The phytoplankton peak in the middle of the experiments was mainly due to an autotrophic nanoflagellate, Pyramimonas sp. At the end of the experiment, the proportion of heterotrophic organisms was higher in the nutrient enriched than in the nutrient-poor treatment, indicating increased predation control of primary producers. The proportion of potentially mixotrophic plankton, prymnesiophyceans, chrysophyceans and dinophyceans, were significantly higher in the nutrient-poor treatment. Furthermore, the results indicated that the food web efficiency, defined as mesozooplankton production per basal production (primary production + bacterial production - sedimentation), decreased with increasing nutrient status, possibly due to increasing loss processes in the food web. This could be explained by promotion of the heterotrophic microbial food web, causing more trophic levels and respiration steps in the food web.
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