Contribution of small phytoplankton to total primary production in the Chukchi Sea

Abstract

Given a projection of thriving small phytoplankton in the Arctic Ocean under climate-induced environmental changes, it is important to estimate the contribution of small phytoplankton (0.7-5 mu m) to the total primary production in the Chukchi Sea, which is an important conduit of organic matter from the North Pacific to the Arctic Ocean. Based on a C-13-N-15 dual isotope tracer technique, small phytoplankton productivity measurements were taken during two consecutive cruises in the Chukchi Sea in 2004. The total phytoplankton carbon uptake rates ranged from 0 to 25.38 mg C m(-3) h(-1), whereas the uptake rates of small phytoplankton ranged from 0 to 2.87 mg C m(-3) h-1. In comparison with the carbon uptake rates, total phytoplankton nitrate uptake rates ranged from 0 to 4.40 mg N m(-3) h-1 while small phytoplankton nitrate uptake rates ranged from 0 to 0.39 mg N m(-3) h(-1). Ammonium uptake rates ranged from 0 to 8.34 mg N m(-3) h(-1) and from 0.01 to 2.18 mg N m(-3) h(-1), for total and small phytoplankton, respectively. Small phytoplankton contributed 24.80% (S.D.= +/- 23.0%) to the total chlorophyll-a concentration, and 59.41% (S.D.= +/- 52.12%) to the total carbon biomass due to its higher particulate organic carbon per chlorophyll-a unit during the two cruises in 2004. In the Chukchi Sea, the average contributions of small phytoplankton to carbon and total nitrogen (nitrate +ammonium) uptake rates were 31.72% (S.D.= +/- 23.59%) and 3731% (S.D.= +/- 26.06%), respectively. (C) 2013 Elsevier Ltd. All rights reserved.