Langmuir circulation and small-scale patchiness of marine phytoplankton and zooplankton

Net and bottle sampling programs were used to test the hypotheses that Langmuir circulations can influence the small-scale distribution of marine phytoplankton and zooplankton. Phytoplankton were concentrated in Langmuir cell convergences in densities which were two to four times those measured in divergences. An index of chorophyll a patchiness indicated that patchiness of phytoplankton was greatest over the windspeed range, 3 to 5 m/s, which is the lower range of windspeeds over which Langmuir circulations can occur. Net tows indicated the presence of near surface zooplankton patches oriented parallel to the wind direction over the windspeed range of 5 to 7 m/s. Selected zooplankton taxa were concentrated in Langmuir cell divergences in densities which were two to five times those in convergences. An analysis of windspeeds over a one year period in the Santa Barbara Channel indicated that concentration of phytoplankton and zooplankton can occur regularly on an hourly, daily and monthly basis.