MICROPLANKTON AND ITS FUNCTIONAL-ACTIVITY IN THE BY-SHORE HYDROTHERMAL AREAS IN THE WESTERN PACIFIC

The waters above the active underwater volcanoes on the slopes of Epi Isl (New Hebrides) and Raul Isl (Kermadek), and in the <<Callisto>> ga s anomaly area (Bay of Plenty, New Zealand), being enriched with metha ne and hydrogen, contain an abundant bacterioplankton with biomass sev eral times exceeding that in surrounding oceanic waters. The dark micr obial CO2 uptake there was 10 to 30 times higher than in nearby waters . In areas of shallow underwater volcanic hydrotherms around Whale Isl and While Isl (New Zealand), as well as in Matupi Harbour Bay (New Br itain Isls), a significant rates of microbial chemosynthesis were reco rded in water column (5-10 mg C/m3 day). The microbial biomass was the re 20-69 mg C/m3, and above the field of a algalbacterial mats it was 100 mg C/m3. The volume of microbial cells in waters influenced by hyd rothermal activity was up to 0.4 mum3 which is 2-4 times higher than i n surrounding areas. The primary phytoplankton production was also sig nificantly higher in these waters, along with notable activity of hydr ogen- and methane-oxidizing bacteria and thiobacilli. In the areas inf luenced by hydrotherms (Whale Isl), planktonic amoebae dominated in mi croplankton communities reaching 30x10(3) individuals per liter. Under discussion are probable mechanisms of influence of shallow hydrotherm al effluents upon the biota of coastal waters.