Enzymatic activities of Antarctic microplankton: relationship with primary productivity, phosphate and nitrate
Iriarte; Gonzalez; Quinones; 강성호
Biochemical adaptations of microplankton are crucial in the modulation of primary productivity, especially in a severe environment such as Antarctica. The enzymatic activities of nitrate reductase (NR), alkaline phosphatase (AP) and malate-dehydrogenase (MDH) of the microplankton (< 210 um) were studied during a cruise in Shetland Islands (Antarctica), during austral spring. Two distinct zones were found based on primary productivity and autotrophic biomass. Zone I included stations with primary productivity higher than 2 mg C m-3 h-1 and mean biomass concentrations of about 0.75 ug Chl. L-1, and Zone II presented values less than 2 mg C m-3 h-1 and 0.17 ug Chl. L-1 for primary productivity and mean chlorophyll concentration respectively. Enzymatic activities of NR, PA and MDH were higher in the Zone I compared to Zone II. AP specific activity was negatively correlated with phosphate concentrations lower than 2.0 uM, which indicates that microplankton were under limiting phosphate condition. There was an inverse relationship between primary productivity and nitrate, and a direct relationships between NR and NO3, suggesting the occurrence of nitrate respiration by the microplankton community.