A major objective of the multidisciplinary Palmer Long Term Ecological Research (LTER) program is to obtain a comprehensive understanding of various components of the Antarctic marine ecosystem—the assemblage of plants, animals, ocean, sea ice, and island components south of the Antarctic Convergence. Phytoplankton production plays a key role in this polar ecosystem, and factors that regulate production include those that control cell growth (light, temperature, nutrients) and those that control cell accumulation rate and 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 decade (1991–2000) of ecological research in the western Antarctic Peninsula region. We evaluate the spatial and temporal variability of phytoplankton biomass (estimated as chlorophyll-a concentration) and primary production (determined in-situ aboard ship as well as estimated from ocean color satellite data). We also present the spatial and temporal variability of sea ice extent (estimated from passive microwave satellite data). While the data record is relatively short from a long-term perspective, evidence is accumulating that statistically links the variability in sea ice to the variability in primary production. Even though this marine ecosystem displays extreme interannual variability in both phytoplankton biomass and primary production, persistent spatial patterns have been observed over the many years of study (e.g., an on to offshore gradient in biomass and a growing season characterized by episodic phytoplankton blooms). This high interannual variability at the base of the food chain influences organisms at all trophic levels.