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Phytoplankton population dynamics and the fate of production during the spring bloom in Auke Bay, Alaska 1
Author(s) -
Laws Edward A.,
Bienfang Paul K.,
Ziemann David A.,
Conquest Lytha D.
Publication year - 1988
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1988.33.1.0057
Subject(s) - phytoplankton , photic zone , spring bloom , zooplankton , oceanography , bloom , bay , biomass (ecology) , environmental science , water column , new production , grazing pressure , population , irradiance , nitrate , chlorophyll a , grazing , ecology , biology , nutrient , botany , geology , physics , demography , quantum mechanics , sociology
Primary production rates and the concentrations and vertical fluxes of phytoplankton pigments were measured in Auke Bay, Alaska, on a twice‐weekly basis over a period of 56 d spanning the 1985 spring bloom. Application of a slightly modified version of the Welschmeyer‐Lorenzen equations yielded growth rates that were in excellent agreement with the ratio of primary production to particulate carbon in the water column. These results suggest that the assumption in the Welschmeyer‐Lorenzen model that chlorophyll a is converted to pheopigments with an efficiency of about 66% as a result of zooplankton grazing is probably close to the truth in this system. Of the primary production that occurred during the study period, about 40% was lost from the euphotic zone due to the sinking of viable cells and 58% was lost due to zooplankton grazing. Only about 1.5% of the primary production remained in the euphotic zone in the form of additional phytoplankton biomass at the end of the study. Herbivorous zooplankton were estimated to be assimilating at least 58% of the phytoplankton carbon they ingested—a conclusion in reasonable agreement with previously published laboratory studies. Although phytoplankton biomass in this system appears to be limited by the supply of nitrate, phytoplankton growth rates seem to be limited by either irradiance or temperature.