Changes in the water quality characteristics during a macroalgal bloom in a coastal lagoon

The shift from seagrass to macroalgae, particularly the “boom and bust” cycle of the ephemeral Chlorophyta in estuarine environments has occurred worldwide, most likely as a result of anthropogenic nutrient loading. Contrary to popular view, these algal blooms are not harmful to humans, although they are perceived as unsightly and negatively affect aquatic leisure activities. Macroalgal blooms mostly occur in spring and summer when rainfall prior to and during this time is low and temperatures are high. Water quality data have been collected before and during an algal bloom at Avoca lagoon on the Central Coast of NSW, Australia, to identify changes in water quality associated with a bloom. Water dissolved oxygen declined significantly whereas turbidity and available phosphate increased significantly during the bloom. The changes could be detected only using intensive spatial and temporal replication. Identifying water quality changes during a bloom is a crucial first step for understanding the conditions under which extensive growth of algae occur and has important implications for prediction and management of the blooms in coastal lagoons.