WH A T W E H A V E L E A R N E D
The Chukchi Sea floor continues to be rich and productive… Large amounts of organic matter continue to sink to the seafloor, and support high productivity in benthic communities. However, the composition of this material is changing, with possible nutritional consequences for organisms that live on or feed at the seafloor. Particulate organic matter that falls to the seafloor (including ice algae, dead phytoplankton, and zooplankton fecal pellets) provides nutrition that sustains bottom-dwelling organisms. For example, as ice begins to melt in spring, algae living on the under- side of the ice fall to the seafloor. The Chukchi Sea is shallow enough that sunlight can reach the bottom, and detached ice algae can continue to photosyn- thesize there. Fecal pellets from zooplankton also rapidly settle to the seafloor. Initially, we thought that changes in sea ice and water temperature would increase consumption by zooplankton and fishes and prevent as much organic matter from reaching the seafloor. Instead we found that large amounts of organic matter continued to reach the seafloor.
… but changes are already occurring Changing food sources may contribute to shifts in the dominant species on the seafloor, and this has already been observed in some areas. Important prey items such as clams and amphipods have widely different needs in terms of caloric intake. Changes in the species that comprise benthic communities will impact how rapidly organic material is consumed in sediments and will have implications for the seabirds and marine mammals that rely on them. By 2100, some bottom-dwelling animals may find themselves in waters that are warmer than they prefer and perhaps even warmer than they can survive. As water temperatures warm, the metabolism and food consumption of animals on the seafloor will likely increase significantly, potentially resulting in food limitation for some species. These animals include the prey for bottom-feeding whales, seals and walruses, seabirds, and benthic fishes. Larger- bodied prey items like some clams may be replaced by smaller animals with reduced energy demands. Snow crab will likely benefit from warmer bottom sea temperatures.
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