Variability of primary production in an antarctic marine ecosystem as estimated using a multi-scale sampling strategy

A major objective of the multidisciplinary Palmer Long Term Ecological Rese arch (LTER) program is to obtain a comprehensive understanding of various c omponents of the Antarctic marine ecosystem-the assemblage of plants, anima ls, ocean, sea ice, and island components south of the Antarctic Convergenc e. Phytoplankton production plays a key role in this polar ecosystem, and f actors that regulate production include those that control cell growth (lig ht, temperature, nutrients) and those that control cell accumulation rate a nd hence population growth (water column stability, advection, grazing, and sinking). Several of these factors are mediated by the annual advance and retreat of sea ice. In this study, we examine the results from nearly a dec ade (1991-2000) of ecological research in the western Antarctic Peninsula r egion. We evaluate the spatial and temporal variability of phytoplankton bi omass (estimated as chlorophyll-a concentration) and primary production (de termined in-situ aboard ship as well as estimated from ocean color satellit e data). We also present the spatial and temporal variability of sea ice ex tent (estimated from passive microwave satellite data). While the data reco rd is relatively short from a long-term perspective, evidence is accumulati ng that statistically links the variability in sea ice to the variability i n primary production. Even though this marine ecosystem displays extreme in terannual variability in both phytoplankton biomass and primary production, persistent spatial patterns have been observed over the many years of stud y (e.g., an on to offshore gradient in biomass and a growing season charact erized by episodic phytoplankton blooms). This high interannual variability at the base of the food chain influences organisms at all trophic levels.