A seasonal study of the distribution of surface state variables in Liverpool Bay. IV. The spring bloom

Physical, chemical, and phytoplankton distributions observed in Liverpool Bay during early and terminal stages in development of the spring bloom in May, 1977, are described. Qualitative and quantitative changes in phytoplankton distributions are interpreted with respect to the contemporaneous chemical and physical hydrography and quantified changes in the hydrography between the periods of observation. In early May, a physical discontinuity demarcated the biological, physical, and most of the chemical characteristics of the offshore and coastal waters. Phytoplankton numbers were greatest in the inshore waters and decreased seaward. The diatom bloom was concentrated in coastal areas where the nutrient status of the waters was least favourable to sustain it. The waters bounded by the front and the coast were composed of a number of physically and chemically distinct water types and each had associated with it a qualitatively distinct phytoplankton population. During the early stage of the spring bloom no abnormal concentrations or accumulations of phytoplankton were associated with the front. By late May areas of diverse phytoplankton density had developed in the inshore waters, major differences in qualitative composition were associated with various density fields and the physical discontinuity, separating offshore and coastal waters, had developed into the site of greatest phytoplankton density. The spatial and temporal changes in the phytoplankton populations are shown to be related to the nutrient status of the waters both within and at the boundaries of the various density fields.