Virus infection of Emiliania huxleyi deters grazing by the copepod Acartia tonsa

Abstract

Copepods are an important link in marine food webs bridging primary and secondary production with higher trophic levels. Viral infections of phytoplankton can short circuit this traditional food web and release significant quantities of carbon from phytoplankton into the dissolved organic pool. The magnitude of the carbon released is in part dependent on the direct and indirect effects of viral infections on the grazing rates of copepods. During viral infection, phytoplankton undergo significant physiological and biochemical changes which could influence their susceptibility to herbivorous zooplankton. In this study, grazing experiments were conducted to investigate the impact of Emiliania huxleyi infection by the coccolithovirus EhV-86 on the ingestion rates of the calanoid copepod Acartia tonsa. Our results showed significantly lower ingestion of infected cells as compared to uninfected cells. High-resolution grazing experiments suggest that the lower ingestion rates are initiated within hours of infection. These results suggest that viral infections can alter food web structure and may result in lower food web efficiency. Hence, the overall impact of coccolithovirus infection on ecosystem function and carbon transfer during the progression of an E. huxleyi bloom should be considered in the context of copepod grazers.