Variations of microbial loop carbon flux in western subtropical Pacific coastal water between warm and cold season

Viral lysis and protist grazing differ in their impact on the aquatic food web. In this experimental study, an adapted version of the dilution technique was applied to simultaneously estimate the effect of grazing by protists (nanoflagellates and ciliates) and viral lysis on bacteria and carbon flow in western subtropical Pacific coastal water. Four separate experiments were carried out: two experiments in the warm season (> 25 °C) and two in cooler seasons (< 25 °C). In the warm season, grazing by protists (nanoflagellates and ciliates) removed about 69% of bacterial production. In the cooler seasons, ciliate grazing did not have a significant impact on bacteria, but viral lysis had a significant and major impact, removing 79% of the bacterial production. Grazing by protists and viral lysis play critical and seasonal roles in the functioning of marine microbial food webs.