Interactions among nutrients, microalgae, and algal grazers regulate the occurrence and severity of ecosystem disruptive algal blooms
An ecosystem model newly developed by NCCOS and NMFS scientists reveals the complex ecosystem interactions and environmental factors that promote the formation and severity of harmful blooms that disrupt and degrade ecosystems.
The model shows that such ecosystem disruptive algal blooms (EDABs) are caused by complex interactions among a number of key factors that were previously not known to interact. These factors include competition between harmful and beneficial algal species for growth-limiting nutrients, different grazing mortality rates for harmful species and competing beneficial ones, and positive feedback interactions tied to grazer-linked recycling of nutrients.
The model predicts that the incidence and severity EDAB events are promoted by decreased flushing rates of coastal bays, and that bloom severity is greatly increased by increased nutrient concentrations. Thus, both decreases in rainfall linked to climate change and anthropogenic inputs of nutrients should promote such blooms and their harmful effect on ecosystems and fisheries.
The new model should help environmental managers to identity causative factors, and to design strategies to minimize or mitigate harmful blooms and their negative environmental and societal impacts. The new findings will appear in an upcoming issue of Marine Ecology Progress Series.