Response of nutrients and the surface phytoplankton community to ice melting in the central Arctic Ocean

Abstract

During the fourth Chinese National Arctic Research Expedition cruise in summer 2010, a time-seriesobservation was carried out to examine the response of nutrients and phytoplankton community in the ice-waterinterface to the ice melting ice in the central Arctic Ocean. Phosphate and silicate in the ice-water interface wererich relative to dissolved inorganic nitrogen (DIN), based on the Redfield ratio (16N:1P:16Si), suggesting that DINwas the potential limiting nutrient. DIN concentrations in the sea ice were about 3-4 times that in the surfaceseawater, indicating that melting ice delivered DIN to the surface water. Pigment analysis showed that fucoxanthinand chlorophyll a contribute to carotenoids and chlorophylls in particles. The mean concentrations of chlorophyll c ,diatoxanthin, diadinoxanthin and fucoxanthin from 15 August to 18 August were 6 µ g.m-3, 22 µ g.m-3, 73 µ g.m-3and 922 µ g.m-3, respectively, suggesting that diatoms dominated in the phytoplankton community composition.Furthermore, a notable enhancement in fucoxanthin and chlorophyll a during a large-scale ice melting was likelyattributed to senescent diatoms released from the bottom sea-ice as well as phytoplankton diatoms growth in thewater column due to the input of nutrients (i.e., DIN) and reducing light limitation from melting ice. Temporaldistribution patterns of prasinoxanthin and lutein diffred from fucoxanthin, indicating that the response of greenalgae and diatoms to ice melting were different.