Viral lysis and nanoflagellate grazing on prokaryotes: effects of short-term warming in a coastal subtropical marine system

Although temperature is a key parameter in the control of the activity and growth of all microorganisms, little is known about how temperature might simultaneously affect viral lysis and nanoflagellate grazing on prokaryotes. This study investigated the effect of rising temperatures on nanoflagellate grazing, viral lysis, and prokaryotic growth in coastal waters of the western subtropical Pacific Ocean during winter (<25°C) and summer (>25°C) in 2013. To do this, water samples were incubated for 24 h at ambient and experimentally increased temperatures (averages 2–3°C higher than in situ values) and analyzed for prokaryotic gross growth, grazing, and viral lysis using a modified dilution method. The experimental warming conditions were found to cause an increase in prokaryotic gross growth rates in the winter and summer season, respectively. Although the experimental warming conditions also caused an increase in the average rate at which prokaryotes were being grazed, they also caused a general decrease in viral lysis during summer. These findings suggest that short-term warming influenced the function of the microbial food web by increasing the rates of prokaryotic production and flux in prokaryotic carbon to predators.