Response of phytoplankton dynamics to 19-year (1991–2009) climate trends in Potter Cove (Antarctica)

King George Island (KGI, Isla 25 de Mayo) is located within one of the most rapidly warming regions on Earth at the north-western tip of the Antarctic Peninsula. Since 1991 hydrographical characteristics and phytoplankton dynamics were monitored at two stations in Potter Cove, a fjord-like environment on the south-eastern KGI coastline. Seawater temperature and salinity, total suspended particulate matter (TSPM) and chlorophyll-a (Chl-a, a proxy for phytoplankton biomass) concentrations were measured in summer and winter over a 19-year period, together with local air temperature. Mean air temperatures rose by 0.39 and 0.48 °C per decade in summer and winter, respectively. Positive anomalies characterized wind speeds during the decade between the mid '90 and the mid 2000 years, whereas negative anomalies were observed from 2004 onwards. Day of sea ice formation and retreat, based on satellite data, did not change, although total sea ice cover diminished during the studied period. Surface water temperature increased during summer (0.36 °C per decade), whereas no trend was observed in salinity. Summer Chl-a concentrations were around 1 mg m^− 3 Chl-a with no clear trend throughout the study period. TSPM increased in surface waters of the inner cove during the spring-summer months. The Southern Annular Mode (SAM) climate signal was apparent in the fluctuating interannual pattern of the hydrographic variables in the outer Potter Cove and bottom waters whereas surface hydrography was strongly governed by the local forcing of glacier melt. The results show that global trends have significant effects on local hydrographical and biological conditions in the coastal marine environments of Western Antarctica.