The abundance, distribution, and correlation of viruses, phytoplankton, and prokaryotes along a Pacific Ocean transect

Concentrations of virus-like particles (VLP), prokaryote-like particles (PLP), chlorophyll a, and zeaxanthin were determined at 9-12 depths (0-250 m) for each of 13 stations along a 3,800-km transect from the coastal waters of Monterey Bay, California (36.62degreesN, 122.25degreesW) to the open ocean Hawaii Ocean Time-Series (HOTS) station near Hawaii (22.69degreesN, 158.12degreesW). We collected VLP and PLP, the latter of which included heterotrophic bacteria and cyanobacteria, in glutaraldehyde-fixed samples on 0.02-mum Anodisc filters. The samples were stained with the nucleic acid dye Yo-Pro-1 and quantified by epifluorescence microscopy. Measurements of Chl a and zeaxanthin were used as indicators of total phytoplankton and cyanobacteria biomass, respectively. With the exception of the most coastal station, depth-integrated VLP and PLP abundance was similar at all stations along the transect; all stations showed a decrease of VLP and PLP with depth. Standard multiple regression analysis showed that logarithmically transformed PLP abundance (sr(2) = 0.64) was the only variable that contributed significantly to the prediction of (log of) VLP. These results confirm and extend results elsewhere that indirectly suggested that prokaryotes are the major host organisms for viruses throughout the ocean. Simple linear regression suggests that VLP abundance is similar to15 times that of PLP across the central eastern Pacific transect surveyed in this study (VLP ml(-1) = 14.7 x PLP ml(-1) + 9.6 x 10(5); r(2) = 0.80, n = 90).