Impact of short-term warming on seasonal variations in bacterial growth, grazing, and viral lysis in coastal waters of Taiwan

Abstract

Although temperature is a key parameter controlling the activity and growth of all microorganisms, information about how water temperature may affect the trophic interactions and carbon flow patterns of microbial food webs is not consistent. We investigated the response in bacterial gross growth, grazing rates, and viral lysis to small temperature changes (3°C above in situ values) in coastal waters of Taiwan using a modified dilution method approach over a 1 yr period from September 2013 to September 2014. Warming increased the bacterial gross growth rates and bacterial losses to grazing, demonstrating clear seasonality. The warming conditions led to a 5 to 200% increase in bacterial gross growth rates. The increase ratios of bacterial gross growth rates were low (5 to 25%) at higher ambient temperatures (>25°C) but increased exponentially at lower ambient temperatures (<25°C) with warming. Grazing increased in parallel with seasonal bacterial growth, while viral lysis did not. These results could prove useful in forming a testable hypothesis about the possible directions of change of microbial carbon fluxes that may accompany the warming of the coastal waters of Taiwan.