Grazing and viral lysis rates of the different phytoplankton groups. Grazing and viral lysis rates were determined using the modified dilution assay. The phytoplankton groups include Synechococcus (Syn, sample size N=19), low-light-adapted Prochlorococcus (Prochl LL, N=13), picoeukaryotes (Pico I–II, N=45) and nanoeukaryotes (Nano I–III, N=28). High-light-adapted Prochlorococcus was largely absent at the depths sampled for the modified dilution assays. Error bars S.E. Bars with different letters are significantly different (P<0.05), as tested by two-way analysis of variance followed by post-hoc comparison of the means using Tukey's honest significant difference.