Vertical distribution of virus-like particles (VLP) and viruses infecting Micromonas pusilla during late summer in the southeastern Skagerrak, North Atlantic

Abstract

Vertical profiles were made at one offshore station and one coastal station, on 4-5 September 1996, in the south-eastern Skagerrak. The surface water of the two stations differed significantly with respect to both temperature and salinity, as the outer station (A) was situated in high-saline water originating from the North Sea, while the low-saline surface water at the inner station (B) was influenced by the Baltic current. Virus-like particle (VLP) abundance was 5 × 10 9 −25 × 10 9 1 −1 H 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 Micromonas pusilla were estimated to ∼0.01% of the VLP number. The ambient concentrations of dissolved inorganic nutrients were typical for a stratified summer situation, i.e. generally low in the surface waters, although a raised ammonium concentration was associated with the sharp halocline at 5 m depth at station B, and all nutrient levels were increasing below 30 m depth.