Viruses in Antarctic lakes

Water samples collected from four perennially ice-covered Antarctic lakes d uring the austral summer of 1996-1997 contained high densities of extracell ular viruses. Many of these viruses were found to be morphologically simila r to double-stranded DNA viruses that are known to infect algae and protozo a. These constitute the first observations of viruses in perennially ice-co vered polar lakes. The abundance of planktonic viruses and data suggesting substantial production potential (relative to bacterial secondary and photo synthetic primary production) indicate that viral lysis may be a major fact or in the regulation of microbial populations in these extreme environments . Furthermore, we suggest that Antarctic lakes may be a reservoir of previo usly undescribed viruses that possess novel biological and biochemical char acteristics.