Dissolved ATP turnover in the Bransfield Strait, Antarctica during a spring bloom

M. P. Nawrocki¹ and D. M. Karl^1,2

¹Department of Oceanography, University of Hawaii, Honolulu, Hawaii 96822, USA

²Division of Oceanic Biology, Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii 96822, USA

Abstract

Ambient concentrations and turnover rates of dissolved adenosine triphosphate (D-ATP) were measured at 5 stations in the Bransfield Strait, Antarctica during the 1986-87 Research on Antarctic Coastal Ecosystem Rates (RACER) field program. The study area was pre-selected to include several different coastal and oceanic habitats expected to vary considerably in timing and magnitude of the annual spring phytoplankton bloom. D-ATP concentrations varied both spatially and temporally during the 4 mo of observation. Durring the initial stages of bloom development, there was a significant positive correlation between the concentration of particulate (P) ATP (i.e. biomass) and D-ATP; however, this relationship deteriorated later in the season. At the height of the spring bloom (January), we observed a D-ATP concentration gradient in excess of an order of magnitude for our coastal to open ocean transect. Dissolved ATP fluxes (uptake rate times ambient concentration; ng l^-1 d^-1) were highly correlated with D-ATP concentrations, indicating that bloom conditions stimulated both production and removal processes. We assessed the potential role of 3 independent processes as a source of D-ATP in Antarctic coastal waters: excretion/exudation, production during micro- or macrozooplankton grazing and cell death/autolysis. Results are most consistent with a model that includes phytoplankton release durlng active growth and metabolism as a major source of D-ATP in our study area.