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Different responses of two common Arctic macrobenthic species ( Macoma balthica and Monoporeia affinis) to phytoplankton and ice algae: Will climate change impacts be species specific?
Recent reductions in sea ice cover and thickness in the Arctic will lead to changes in food supplies for benthic consumers. We experimentally assessed responses of two common Arctic macrobenthic species, Macoma balthica (Bivalvia) and Monoporeia affinis (Crustacea) from Kotzebue Sound (Alaska, USA)...
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Published in: | Journal of experimental marine biology and ecology 2009-08, Vol.376 (2), p.110-121 |
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Main Authors: | , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Recent reductions in sea ice cover and thickness in the Arctic will lead to changes in food supplies for benthic consumers. We experimentally assessed responses of two common Arctic macrobenthic species,
Macoma balthica (Bivalvia) and
Monoporeia affinis (Crustacea) from Kotzebue Sound (Alaska, USA) to varying food materials (phytoplankton and ice algae). Phytoplankton and
13C-labelled ice algae were added separately or together to pre-sieved sediment cores containing known numbers of
Macoma or
Monoporeia. After 8
d, sediments and animals were analyzed for bulk C/N contents, isotopic signatures, fatty acid compositions and compound-specific δ
13C values. Our results showed that the two species responded differently to varying food materials. Loss of characteristic fatty acids and changes in δ
13C values in the surrounding sediments indicate that
Macoma preferentially consumed ice algae compared to phytoplankton, while
Monoporeia non-selectively ingested both food materials. Feeding behaviors also differed between the two species:
Macoma fed primarily on material from the sediment surface, and did not appear to mix material to depth, while
Monoporeia mixed some fresh food material from the surface down to subsurface sediments (1–2
cm). Analysis of animal biomass showed more
13C-labelled organic carbon from ice algae was assimilated by individual
Macoma compared to individual
Monoporeia. Moreover, δ
13C values of fatty acids in
Macoma were much higher than those in
Monoporeia, suggesting that
Macoma directly assimilates fatty acids from their food source while
Monoporeia might
de novo biosynthesize fatty acids in their biomass. Additionally, both species had higher fatty acid contents and proportion of polyunsaturated components when they fed on ice algae compared to phytoplankton, implying that ice algae may be a better food than phytoplankton for Arctic benthos. Finally, analysis of bacteria-specific fatty acids in sediments (from both types of animal cores) showed that the δ
13C values were enriched up to 400‰ relative to natural background values (−25% to −30‰), suggesting that organic carbon from fresh ice algae could be rapidly incorporated into bacteria biomass. The collective results of this experimental study suggest that the changes in food supplies due to reduction of ice coverage will have a greater impact on those benthic organisms that prefer ice algae to phytoplankton. This may lead to the potential changes in community structure favoring those |
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ISSN: | 0022-0981 1879-1697 |
DOI: | 10.1016/j.jembe.2009.06.018 |