HABs modeling tool developed to predict influence of nutrients on when, where toxin-producing events will occur

SCCWRP and the University of California, Los Angeles have developed a modeling tool that predicts when and where toxins produced by a common type of marine algal bloom can be expected to occur along the California coast, and how land-based nutrient discharges to Southern California coastal waters are influencing the frequency and extent of these events.

The findings, described in a manuscript published in January by the journal Harmful Algae, involved comparing modeling predictions for domoic acid – a toxin produced by a ubiquitous type of HAB known as Pseudo-nitzschia – to field-collected data on when and where toxin-producing blooms actually occurred.

The model predicted that land-based nutrient discharges amplify domoic acid production by a non-trivial amount relative to the natural susceptibility of Southern California coastal waters to these blooms (i.e., as a result of ocean processes like natural coastal upwelling events). Domoic acid produced by the blooms can poison mammals and contaminate commercially important species like Dungeness crab.

The modeling work is helping managers understand to what extent local, land-based sources of nutrients are exacerbating coastal conditions. The model makes use of a coupled physical-biogeochemical ocean model that predicts how land-based discharges affect coastal acidification and hypoxia.