CONTROL OF PHYTOPLANKTON BIOMASS IN ESTUARIES - A COMPARATIVE-ANALYSIS OF MICROTIDAL AND MACROTIDAL ESTUARIES

Macrotidal estuaries (mean tidal range > 2 m) generally exhibit a tolerance to pollution with nitrogen-containing nutrients despite high loadings originating from freshwater outflows. These systems, which are characterized by high tidal energy, generally exhibit lower levels of chlorophyll a than systems with lower tidal energy. A comparative analysis of data from 40 microtidal and macrotidal estuaries shows that mean annual chlorophyll a levels are significantly lower in systems with high tidal energy even when nitrogen concentrations are equal to nitrogen levels in the microtidal systems. Tidal range and associated processes (e.g., tidal mixing, current velocity, light penetration, and sediment resuspension) influence phytoplankton biomass in some estuaries.