(Table 1) Characteristics of air temperature, sea surface temperature, sea surface salinity, nutrients, and total particulate matter for Admiralty Bay and Potter Cove, King George Island, Antarctica

Since the early 1990s, phytoplankton has been studied and monitored in Potter Cove (PC) and Admiralty Bay (AB), King George/25 de Mayo Island (KGI), South Shetlands. Phytoplankton biomass is typically low compared to other Antarctic shelf environments, with average spring - summer values below 1 mg chlorophyll a (Chl a)/m**3. The physical conditions in the area (reduced irradiance induced by particles originated from the land, intense winds) limit the coastal productivity at KGI, as a result of shallow Sverdrup's critical depths (Zc) and large turbulent mixing depths (Zt). In January 2010 a large phytoplankton bloom with a maximum of around 20 mg Chl a/m**3, and monthly averages of 4 (PC) and 6 (AB) mg Chl a/m**3, was observed in the area, making it by far the largest recorded bloom over the last 20 yr. Dominant phytoplankton species were the typical bloom-forming diatoms that are usually found in the western Antarctic Peninsula area. Anomalously cold air temperature and dominant winds from the eastern sector seem to explain adequate light : mixing environment. Local physical conditions were analyzed by means of the relationship between Zc and Zt, and conditions were found adequate for allowing phytoplankton development. However, a multiyear analysis indicates that these conditions may be necessary but not sufficient to guarantee phytoplankton accumulation. The relation between maximum Chl a values and air temperature suggests that bottom-up control would render such large blooms even less frequent in KGI under the warmer climate expected in the area during the second half of the present century

On the phytoplankton bloom in coastal waters of southern King George Island (Antarctica) in January 2010: An exceptional feature?

Since the early 1990s, phytoplankton has been studied and monitored in Potter Cove (PC) and Admiralty Bay (AB), King George/25 de Mayo Island (KGI), South Shetlands. Phytoplankton biomass is typically low compared to other Antarctic shelf environments, with average spring–summer values below 1 mg chlorophyll a (Chl a) m23. The physical conditions in the area (reduced irradiance induced by particles originated from the land, intense winds) limit the coastal productivity at KGI, as a result of shallow Sverdrup’s critical depths (Zc) and large turbulent mixing depths (Zt). In January 2010 a large phytoplankton bloom with a maximum of around 20 mg Chl a m23, and monthly averages of 4 (PC) and 6 (AB) mg Chl a m23, was observed in the area, making it by far the largest recorded bloom over the last 20 yr. Dominant phytoplankton species were the typical bloom-forming diatoms that are usually found in the western Antarctic Peninsula area. Anomalously cold air temperature and dominant winds from the eastern sector seem to explain adequate light : mixing environment. Local physical conditions were analyzed by means of the relationship between Zc and Zt, and conditions were found adequate for allowing phytoplankton development. However, a multiyear analysis indicates that these conditions may be necessary but not sufficient to guarantee phytoplankton accumulation. The relation between maximum Chl a values and air temperature suggests that bottom-up control would render such large blooms even less frequent in KGI under the warmer climate expected in the area during the second half of the present century

An interdisciplinary approach to climate and coastal systems changes on King George Island

Local climate warming recorded at maritime Antarctica since 50 years dramatically affects small ice caps such as on King George Island (KGI) at the Northern tip of the Antarctic Peninsula. DGPS measurements revealed surface lowering in elevations up to 270 m above ellipsoid with a maximum of 14 m over 11 years. Glacial area loss at KGI amounted to 20 sqkm between 2000 and 2008. Newly ice free areas opened and succession of diatoms, ostracods and foraminifers can be read in sediments cores. Input of glacial melt water and mineral suspension into coastal areas reach highest monthly yields in January. Timing of the annual discharge wave and volume have increased during the past 5 years. Coastal biota are severely affected by melt water, shading, sedimentation and increased intensity of iceberg scour. 20 years of coastal monitoring indicate that sediment discharge in summer combines with slowly rising water temperatures and freshening in coastal surface waters fronting melting glaciers. Shifts in pelagic communities from larger diatoms to smaller phytoflagellates in the highly stratified summer scenario correlate with large quantities of beaching dead krill. Shifts in the lower distribution limit of macroalgae have cascading effects on grazers and change community structure. Elevated rates of sediment deposition on the seafloor distinctly affect different groups of benthic macrofauna and shifts in benthic community and population age structure can be well explained with species specific sensitivity to sediment and iceberg impact. Most Antarctic macrofauna are highly vulnerable to change, but in some cases we observe unexpected adaptability