Sources, diversity and circulation of biogenic compounds in Admiralty Bay, King George Island, Antarctica

Abstract

AbstractThis paper presents horizontal and seasonal differences in the concentrations of nitrogen and phosphorus in the surface waters of Admiralty Bay. The average annual concentrations of total nitrogen and total phosphorus were found to be 1.054 and 0.129 mg dm-3 respectively. Organic nitrogen constituted 59% of total nitrogen on average, while N-NO3- was substantially higher than N-NH4+ (0.362 and 0.062 mgN dm-3, respectively). Organic phosphorus constituted 34% of total phosphorus on average, and the mean annual concentration of reactive phosphorus was 0.085 mgP dm-3. The observed concentrations of N and P were higher in the nearshore area and lower in the central part of the Admiralty Bay basin. In explaining this account was taken of surface runoff into the bay, the decay of marine macroalgae in the tidal area and the excretion of N and P by marine animals. The concentrations of total nitrogen and total phosphorus in freshwater streams varied from 0.528–5.698 mgN dm-3 and from 0.088–1.709 mgP dm-3. In laboratory experiments, 24-hour loads of total nitrogen and total phosphorus released from the remains of macroalgae into the waters of the bay were estimated at about 6.2 tN and 10.3 tP, while the approximate quantities excreted by macrozoobenthos were 482 kgN and 48 kgP. The availability of N-NH4+ was seen to be greater in the waters of the bay than has been reported for open water in this part of the ocean and water from the Bransfield Strait had a diluting effect on the concentrations of nitrogen and phosphorus in the bay. The role of the wind in carrying mineral salts from waters of the Bay to the inland environment was also discussed.