Abstract
To understand the role of viruses in the marine environment, it is important to know the factors affecting their temporal distribution and the abundance of lysogens. We therefore performed a seasonal and a diel study on viral distribution in Tampa Bay, Florida, USA, and detected the abundance of lysogens and bacteriocinogens amongst marine bacterial isolates from diverse marine environments. We investigated the distribution of viruses, bacterial direct counts, chlorophyll a (chl a), salinity and temperature during a 13 mo period in the Tampa Bay estuary. The results indicated that the viral population had a strong seasonal pattern with the highest concentrations (2.0 f 0.8 X 10') in the summer and lowest (4.8 k 1.4 X 106) in the winter Viral abundance was negatively correlated with salinity ( r = -0.8031, and positively correlated with chl a concentration (r = 0.725). A dlel study in a seawater mesocosm indcated that viral abundance did not vary on a diel rhythm, but rather peaked after a maximumin bacterial abundance and chl a. Dissolved DNA concentrations displayed diel rhythmicity, suggesting that viruses were not the main source of dissolved DNA. An estimation of the percentage of the bacterial standing stock lysed by viruses based on 4 h intervals ranged from 3.0 to 53.3 % per day. Screening bacterial isolates for the presence of inducible prophages indicated that 43 % were lysogens or bacteriocinogens, suggesting that lysogeny and bacteriocinogeny are common in the marine environment.
Highlights
The existence of viruses in the marine environment has been known for nearly half a century (e.g. Kriss & Rukina 1947, Spencer 1955)
Heldal & Bratbak 1991, Bratbak et al 1992).Natural viral populations may play a role in the mortality of marine phytoplankton (Suttle et al 1990, Suttle 1992, Suttle & Chan 1993),and the addition of concentrated native viral populations to seawater reduced primary production by as much as 78 % (Suttle et al 1990, Suttle 1992). the first attempt to incorporate viruses into a carbon budget resulted in a 6-fold overestimation of viral lysis of the bacterial population (Bratbak et al 1992),the results support the idea that viral lysis may be a quantitatively significant process that needs to be incorporated into budgets of microbial carbon transfer
To understand the role of viruses in the marine environment, it is important to know the temporal distribution of viral abundance in relation to the distribution of bacteria, phytoplankton and other biological parameters
Summary
The existence of viruses in the marine environment has been known for nearly half a century (e.g. Kriss & Rukina 1947, Spencer 1955). Ser. 104: 163-172, 1994 terial abundance (Paul et al 1991, Cochlan et al 1993), chl a concentration (Paul et al 1993),or both (Boehme et al 1993). These results suggest that bacterioplankton and phytoplankton were the major viral hosts
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