Assistant Professor of Biology Pepperdine University, California, United States
Domoic acid (DA) is a toxin produced by marine diatoms of the genus Pseudo-nitzschia (Pn) and bioaccumulates in California sea lions (Zalophus californianus). DA toxicosis can cause neurological issues and death, and the rate at which Z. californianus become stranded due to this condition has been increasing since it was first diagnosed in a marine mammal in 1998. We compared geotemporal data of sea lion strandings with data from the California Harmful Algae Risk Mapping (C-HARM) Model to analyze patterns that may indicate when and where a sea lion stranding due to DA toxicosis will occur. C-HARM geographically visualizes the probabilities that Pn diatoms exceed 10,000 cells/L, that cellular domoic acid (cDA) exceeds concentrations of 10 pg per Pn cell, and that particulate domoic acid (pDA) concentrations exceed 500 ng/L in a given area. We defined the parameters within which we would analyze the data according to sea lion foraging behavior: a 100 km area around each stranding location and a time frame of 15 days leading up to and including the date of a stranding observation. Within these parameters we took the means of probabilities of each variable (cDA, pDA, and Pn) and so far have found that Pn shows promise of being the most useful indicator of the three. If a significant relationship between C-HARM and strandings can be established, it could serve as a powerful tool in the management of sea lions and other marine mammals suffering from the effects of DA.
