Phytoplankton blooms and a coastal thermocline boundary along the West Coast of Ireland

The boundary between stratified and mixed water along the Connemara coast (west of Ireland) is described using data collected from 1980 to 1985. The summer thermocline sinks to the bottom close to an underwater escarpment, rather than outcropping on the surface. A series of diatom blooms which are more developed at spring tides occur at depth along the mixed side of the boundary in summer. Chlorophyll concentrations diminish as summer progresses. This decline is associated with a retreat of the thermocline offshore and the steady increase in bottom temperature. Occasional dinoflagellate blooms develop in September, these may be associated with nutrient accumulation below the thermocline. These observations are compared with other descriptions of stratified-mixed boundaries.