The role of pelagic foodfalls in subsidizing deep-sea bottom communities in a changing ocean

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The deep sea is the largest environment on the planet, a sink for carbon and an unexplored biodiversity reservoir. Large gaps exist in our understanding of how the deep regions of the oceans are sustained and how deep-sea communities are impacted by climate change and other human pressures. This project combines deep-sea sampling and experiments, laboratory analyses, and the analysis of unique databases of in situ observations to investigate the link between deep-sea pelagic and benthic carbon flux, biodiversity and food-webs. It will establish basic knowledge that is essential to study and predict the effect of climate change and human pressures on deep-sea communities, and their biodiversity. Part I An ecological paradox that exists in many ocean carbon budgets is that the amount of organic matter that reaches the seafloor, as measured by sediment traps, cannot explain the respiration rates and biomass of many benthic communities. I will test the hypothesis that medium size (invertebrate) foodfalls can explain part of the gap in regional carbon budgets. Using existing databases of deep seafloor observations and by performing benthic surveys during ocean expeditions, I will characterize and quantify natural foodfalls in the Arctic, North Atlantic and North Pacific. To aid the detection of consumed foodfalls, I will analyze environmental DNA in deep-sea sediment to qualify eDNA of nekton and large macrozooplankton. Part II To test the hypothesis that large invertebrate foodfalls are drivers of biodiversity in the deep ocean, this project will perform baited lander experiments in the Arctic, Pacific and Atlantic comparing the scavenging communities and successional stages, as well as processing time, between carrion of fish, cephalopods, and large gelatinous zooplankton. This information will serve to predict how changing pelagic communities as a result of trophic cascades and range expansion may alter diversity and carbon distribution by benthic scavenging communities. Part III We will establish a pelagic baseline at the LTER (Long-term Ecological Research) site HAUSGARTEN to investigate the composition, abundance and distribution of pelagic carrion species in a hotspot of climate change. The Arctic pelagic baseline will be compared to existing baselines of pelagic fauna in the Pacific and Atlantic, and will serve as a starting point to delineate the coupling between the benthic and pelagic environments in a rapidly changing (Arctic) ocean.