VERTICAL-DISTRIBUTION OF VIRUS-LIKE PARTICLES (VLP) AND VIRUSES INFECTING MICROMONAS-PUSILLA DURING LATE SUMMER IN THE SOUTHEASTERN SKAGERRAK, NORTH-ATLANTIC

Vertical profiles were made at one offshore station and one coastal st ation, on 4-5 September 1996, in the south-eastern Skagerrak. The surf ace water of the two stations differed significantly with respect to b oth temperature and salinity, as the outer station (A) was situated in high-saline water originating from the North Sea, while the low-salin e surface water at the inner station (B) was influenced by the Baltic current. Virus-like particle (VLP) abundance was 5 x 10(9)-25 x 10(9) l(-1) in the 0-50 m water column. Maximal VLP values were found in the surface water, although a lower number was detected in the low-saline surface water (0 m depth) at station B. Viruses infective to Micromon as pusilla were estimated to similar to 0.01% of the VLP number. The a mbient concentrations of dissolved inorganic nutrients were typical fo r a stratified summer situation, i.e. generally low in the surface wat ers, although a raised ammonium concentration was associated with the sharp halocline at 5 m depth at station B, and all nutrient levels wer e increasing below 30 m depth.