ROLE OF PHYTOPLANKTON PARASITES IN FOOD WEBS OF THE COLUMBIA RIVER COASTAL MARGIN
Although often overlooked, parasitism in aquatic systems may play an important role in food web dynamics and biogeochemical cycling. In the Columbia River, fungal parasites of phytoplankton (‘chytrids’) have been observed annually during spring blooms. Chytrids efficiently re-package organic material from the large, often inedible, colonial diatoms they infect into fungal zoospores, which are easier for zooplankton to consume. We developed a specific qPCR assay to quantify zoospores in the Columbia River in order to estimate the amount of carbon shunted from large diatom hosts into zoospores. Field samples were collected from 2010-2013 and size fractionated to separate host-attached and free-swimming parasite life stages. Free-swimming zoospore concentrations were low in the summer, fall, and winter. However, in spring, when host diatoms bloom, zoospores were detected at levels up to 1600 per mL, accounting for 17.1 µg/L of particulate organic carbon. The data indicate that parasites of microalgae actively shape the food web by increasing the availability of large diatom carbon to higher trophic levels, in addition to influencing species composition and the density of primary producers.
Maier, M. A., Oregon Health and Science University, USA, firstname.lastname@example.org
Needoba, J. A., Oregon Health and Science University, USA, email@example.com
Peterson, T. D., Oregon Health and Science University, USA, firstname.lastname@example.org
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