9315029 Smith The annual expansion and retreat of pack ice in the Southern Ocean are the largest seasonal processes in the World Ocean. This seasonal migration of the ice cover has a profound impact on the pelagic community in the upper 100 m of the oceanic water column where the interactions between ice cover and apex predators, such as seabirds and mammals, are most intense. This unique pelagic community has been mainly studied with ship-based operations. However, there are well recognized problems associated with shipboard sampling of the epipelagic community under pack ice and the need to monitor this community on long-time scales sufficient to examine the extreme temporal variability of this environment. To examine continuous temporal variability, the project will develop a vertically-profiling pump sampler for the collections of zooplankton and micronekton over programmable depth intervals under pack ice in the Weddell Sea. Once developed and field tested, this instrument will be deployed concurrently with previously developed upward-looking, vertically-profiling acoustic arrays for a period of one year. The combined mooring project will monitor the vertical distribution, abundance and size frequency of acoustically detectable zooplankton and micronekton in the upper 100 m of the water column in an area that experiences ice cover during 7-8 months of the year. This project will also include seasonal shipboard sampling on three cruises over the course of the one year field study. A successful deployment of these long-term mooring arrays and retrieval of data from the field will contribute to a greater understanding of how epipelagic communities function under pack ice in the Southern Ocean. This is a jointly sponsored project of the Office of Polar Programs and the Division of Ocean Sciences. ***
