OBSERVATION AND SIMULATION OF THE SPRING BLOOM IN THE NORTHWESTERN IRISH SEA

A two-layer, coupled physical-biological model was used to investigate phytoplankton dynamics in the north-western Irish Sea. The model was parameterized with values obtained from the published literature, and predicted the concentration of chlorophyll and dissolved inorganic nit rogen in an upper and lower layer. Simulations were driven with measur ed hourly values of meteorological data. The timings of the spring blo om predicted by the model at a summer thermally stratified site and a vertically mixed site were compared with observations made during 1992 . At the mixed site, good agreement was found between the model and ob servations. At the stratified site, the results are less satisfactory and show that the model predicted a spring bloom 13 days later than ob served. The difference was probably due to overestimation of the surfa ce mixed-layer depth leading to underestimation of upper-layer irradia nce. A simple numerical experiment demonstrated that the timing of the spring bloom was best simulated using the maximum theoretically justi fiable value for photosynthetic efficiency.