ENVIRONMENTAL DRIVERS OF PHYTOPLANKTON GROWTH AND GRAZING MORTALITY

In an effort to better understand what factors govern phytoplankton growth (μ, d-1) and mortality due to herbivorous protist grazing (g, d-1) in different biogeographic regions of the oceans, I analyzed data from 401 dilution experiments performed over a decade by the Menden-Deuer laboratory. Measurements were made in the North Atlantic, North Pacific, West Antarctic, Narragansett Bay, and along the Northeast U.S. Shelf. Experiments were performed over temperatures that ranged from -1.5 to 27.4 °C, salinity from 14.1 to 36.5, photosynthetically active radiation (PAR) from 0.24 to 60.0 mol/m2.s chlorophyll a (chl a) concentration from 0.03 to 2.43 μg/L, and sampling depths from surface to 80 m. Growth rates (μ, d-1) ranged from -0.61 to 2.43 d-1 and grazing rates ranged (g, d-1) from 0 to 1.81 d-1. On average, 61% of primary production was grazed (0-550%). Growth and grazing rates were positively correlated with both temperature and light availability, suggesting these environmental variables as important drivers that may be used as predictors of growth and grazing rates to better understand the global impacts of microzooplankton grazing. Improved knowledge of the impacts of grazing is important in accurately predicting carbon flow through ecologically diverse marine food webs