A review of phytoplankton ecology in estuarine and coastal waters around Ireland

Abstract

A review of the distribution of phytoplankton in coastal, shelf and estuarine waters around Ireland was undertaken to consolidate our understanding of the ecology of these organisms in the region. In broad terms, the review has highlighted the relative importance of vertical water column stability and horizontal transport processes in influencing the abundance and composition of phytoplankton. In coastal waters, the seasonal stabilization and de-stabilization of the water column accounts for most of the natural variation in both phytoplankton species composition and biomass. Much of the remaining natural variability can be explained by the interaction of phytoplankton with a number of oceanographic features and processes such as the presence of tidal and thermohaline fronts, wind and topographically associated coastal upwelling, advection landward of offshore water masses and the flow of coastal and oceanic currents. In estuarine waters, the scenario is somewhat reversed, and although seasonality is important in broad terms, the structure of phytoplankton populations is determined more by local factors operating over much smaller time-scales in the order of days and weeks. The interplay of these factors, such as the periodic rise and fall of the tide and episodic changes in river flow, creates a broad range of conditions that result in greater variation in phytoplankton biomass, while at the same time selecting for a reduced number of species that are adapted to survive in this highly changeable environment.