VERTICAL PROFILES OF VIRUS-LIKE PARTICLES AND BACTERIA IN THE WATER COLUMN AND SEDIMENTS OF CHESAPEAKE-BAY, USA

Vertical profiles of virus-like particles (VLPs) and bacteria were det ermined by near-synoptic sampling through the water column and 15 to 2 5 cm into the sediment at 5 stations across the mouth of Chesapeake Ba y, USA. VLPs were about 10 times more abundant in the pore water (gran d mean = 3.6 x 10(8) VLPs ml(-1)) than in the water column (grand mean = 3.8 x 10(7) VLPs ml(-1)). Similarly, bacteria counts were about 3 t imes higher in the pore water (grand mean = 6.5 x 10(6) bacteria ml(-1 )) than in the water column (grand mean = 2.4 x 10(6) bacteria ml(-1)) . The virus to bacteria ratio (VBR) was greater in the pore water (ran ge = 29 to 85) than in the water column (range = 12 to 17). The VER wa s lowest in the water-over-boxcore samples and variable in the pore wa ter. Counts of VLPs and bacteria were positively correlated in the wat er column, although neither was correlated to chlorophyll a. In the wa ter column, VLPs and bacteria counts exhibited significant differences among stations, with the highest values on the southern side of the B ay mouth. In the pore water, VLP abundance varied with depth and was n egatively correlated to grain size. Bacteria abundance was highest at the sediment-water interface, decreased in the first cm of sediment, w as uniform in the deeper horizons, and showed no significant relations hip with grain size. Bacteria counts in pore water were not significan tly different among stations. In contrast, VLP abundances in pore wate r were significantly different among stations, although they did not i ncrease in abundance from north to south across the Bay mouth. as did counts of water-column VLPs. These are the first data indicating the a bundance of VLPs below the surface layer of sediment in aquatic system s and demonstrate that VLPs are components of the sedimentary microbia l community to at least 25 cm depth.