CS29 Phytoplankton & Primary Production
Date: Monday, June 10, 2002
Time: 11:45:00 AM
Location: Oak Bay
 
DeLizoL, VIMS, College of William and Mary, Gloucester Pt., USA, delizo@vims.edu
Smith, W, O, VIMS, College of William and Mary, Gloucester Pt., USA, wos@vims.edu
 
TAXONOMIC COMPOSITION AND GROWTH RATES OF PHYTOPLANKTON AT THE NEW ZEALAND SUBTROPICAL CONVERGENCE
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Off the eastern coast of New Zealand, warm, nutrient-poor Subtropical Waters (STW) are delineated from cool, nutrient-rich Subantarctic Waters (SAW) at the Subtropical Convergence (STC). The Chatham Rise limits mixing of STW and SAW, creating sharp gradients in temperature and in macro- and micronutrient concentrations. Shipboard incubations were conducted during austral spring 2000 and 2001 to test the hypothesis that these gradients might affect the taxonomic composition and/or growth rates of phytoplankton on either side of and at STC. HPLC was used to determine pigment concentrations, from which taxonomic composition of phytoplankton was derived. During both years, we found that STW phytoplankton were dominated by diatoms, whereas dinoflagellates dominated SAW assemblages. Phytoplankton growth rates (determined by 14C-pigment labeling) were higher in STW than in SAW or at STC (ca. 0.7-1.95 per day in STW vs. 0.07-0.7 and 1.0 per day in SAW and STC, respectively, in 2000). We suggest that there are specific conditions to which resident phytoplankton species are adapted within each region; however, phytoplankton growth rates may be controlled by iron.