The phytoplankton of an offshore station in the north-west Irish Sea w
ere sampled daily at a depth of 15m by an automated sampler between Ap
ril and August 1995. Specific rates of net population increase were ca
lculated from the daily data for five species of diatom; the rates lay
mostly in the range 0.2-0.5 day(-1), except for Lauderia annulata, wh
ich increased at 1.4 day(-1) The 39 diatom species found are listed.