In waters surrounding James Ross Island (JRI), which is generally inaccessible, high chlorophyll-a concentration [Chla] can often be detected during summer periods by ocean color imagery. The region is influenced by a retreating sea ice edge from Weddell Sea and freshwater runoff from JRI glaciers, factors that probably trigger phytoplankton growth. In this work, we relate phyto-plankton composition and biomass [Chla and carbon] with environmental factors in two successive late summer periods , in 2008 (1–3 March) and 2009 (17–20 February). Remote sensing data were used to corroborate the findings during those few sampling days. High surface [Chla] patches were observed through both remote sensing and field data (up to 7.61 mg Chla m-3 in 2009), and associated with a relatively shallow upper mixed layer (UML) (19–109 m in 2008 and 16–74 m in 2009). Sea surface temperatures were lower in 2008 (-1.19 to-0.62 °C) than in 2009 (-0.87 to-0.46 °C). Sea ice coverage was greater in 2008 than in 2009 summer, implying an earlier sea ice retreat in the latter year, when higher average [Chla] was obtained from field samples (3.3 mg m-3 , compared to 1.5 mg m-3 in 2008). The eastern side of JRI appeared to be relatively sheltered from the dominant pattern of large-scale westerly winds. Diatoms dominated the phytoplank-ton community, with presence of large diatom species (e.g., Odontella weissflogii) typical of an advanced sea ice melt condition. Those blooms were sustained by a shallow UML associated with relative shelter from winds, due to proximity with the island. Keywords Antarctic Peninsula Á Sea ice Á Ice melting Á Upper mixed layer depth Á Phytoplankton community Á Diatoms