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Photograph: Ice algal lumps under melting sea ice were a food source for sympagic organisms in late July, 2012. Photograph: Peter Leopold
Ice algal lumps under melting sea ice. From Sea Ice Biota. Photograph: Peter Leopold

Marine Ecosystems Summary

Section Coordinators: Mike Gill1, Sue Moore2

1Canadian Wildlife Service, Environment Canada, Whitehorse, YT, Canada & CAFF/CBMP
2NOAA/Fisheries Office of Science and Technology, Seattle, WA, USA

November 8, 2013

The Marine Ecosystems section provides some insights into how the marine ecosystem is responding to changes in environmental conditions, especially the rapid and dramatic loss of sea ice (see the essay on Sea Ice). The central role of sea ice in structuring various components of the marine ecosystem is highlighted in essays on Sea Ice Biota, Marine Benthic Communities and Marine Fish of the Arctic.

Sea ice-derived organic matter continues to be an important early food source for sympagic (ice-associated), benthic (lowermost water column and seafloor) and pelagic (offshore water column) biota in the Arctic. However, sea ice habitats appear to be changing - for example, there is less multiyear ice (see the essay on Sea Ice), but melt ponds are becoming more frequent - in ways that are relevant for ice-associated biota, as indicated by regional decreases in their abundance and biomass. Arctic benthic communities are particularly good biological indicators of the impact of longer-term climate changes on the marine ecosystem, versus seasonal oscillations, because contributing species typically have long life spans (see the essay on Benthos in Report Card 2012). Responses of Arctic benthic communities to climate and anthropogenic factors can be observed from shifts in species distribution patterns and in the appearance of new species. The detection of changes and trends in Arctic benthic communities depends on sustained long-term observing programs, such as the HAUSGARTEN observatory in the Atlantic sector and the Distributed Biological Observatory (DBO) in the Pacific sector of the Arctic (see the essay on Ecosystem Observations in Barrow Canyon in Report Card 2012).

Observed and expected continuing reductions in sea ice and associated changes in productivity (see the essay on Arctic Ocean Primary Productivity in Report Card 2011) will likely affect marine and anadromous fish fauna in the Arctic and the adjacent sub-Arctic seas. There are strong gradients in species richness from warmer, sub-Arctic waters to colder, Arctic waters, implying a strong potential for species to expand their ranges into Arctic waters as temperatures increase. New (to the Arctic) fish species have been reported from several areas, especially the Canadian Beaufort Sea, which likely represent both altered distributions resulting from climate change and previously occurring but undetected species. Here again, comprehensive research surveys are required, extending to more northerly and deeper ocean regions, to establish baselines critical for assessing fish responses to Arctic change.