Seasonal protistan grazing in Narragansett Bay
The impact of heterotrophic protist grazing on phytoplankton abundance was measured in a coastal estuary from January 2010 to February 2011 in Narragansett Bay, RI, USA. Plankton samples were collected within the long-term phytoplankton monitoring project in Narragansett Bay, initiated in the 1950s. Concurrent with weekly dilution experiments, samples were assessed for phytoplankton species composition and environmental conditions. Over the year, grazing removed an average of 94% (range 20–200%) of daily primary production, with peaks in both phytoplankton growth and heterotrophic grazing rates occurring during the summer. Phytoplankton growth rates averaged 0.69 ± 0.58 day−1 for the year, while protistan grazing rates averaged 0.66 ± 0.61 day−1. Phytoplankton growth rates were negative in both winter and spring. Negative growth rates in the winter did not result from nutrient limitation, although, nutrient limitation was evident during the summer. There was no relationship between protistan grazing rates and initial chl a concentration. Grazing rates were positively correlated with temperature as well as changing phytoplankton community composition. Seasonal patterns of protistan grazing and phytoplankton community composition and abundance may be better understood when examined in relation to species composition and environmental conditions rather than bulk measures of biomass, including chl a. Overall, results suggest that grazing by heterotrophic protists accounts for a large proportion of phytoplankton mortality in Narragansett Bay, as is true in many coastal estuaries and indeed the global oceans as well.^
"Seasonal protistan grazing in Narragansett Bay"
Dissertations and Master's Theses (Campus Access).