Distribution and impact of algal blooms leading to domoic acid events in Southern California

The term harmful algal bloom (HAB) is used to describe any bloom of microalgae that has a detrimental impact to the local ecosystem and/or economy.;A variety of HAB-forming species of microalgae occur in southern California, and several of these species are known to produce potent neurotoxins. The impact of algal toxin presence on both the intake and reverse osmosis (RO) desalination process and whether or not the naturally occurring algal toxins can pass through the RO membrane and into the desalination product was addressed through bench-scale RO experiments and monitoring for algal toxins at a pilot RO desalination plant.;Monitoring of HAB species and other pertinent chemical/physical parameters at two piers in southern California, Newport and Redondo Beach, was used to investigate the development of a site-specific bloom definition for identifying emerging DA events. The neurotoxin DA is produced by the chain forming diatom Pseudo-nitzschia, and it is the most common HAB organism in southern California. Emphasis was given to abundances of the P. seriata size category of Pseudo-nitzschia due to the prevalence of this size class in the region. P. seriata bloom thresholds were established for each location based on deviations from their respective long-term mean abundances, allowing the identification of major and minor blooms. Sixty five percent of blooms identified at Newport Beach coincided with measurable DA concentrations, while 36% of blooms at Redondo Beach coincided with measurable DA. Bloom definitions allowed for increased specificity in multiple regression analysis of environmental forcing factors significant to the presence of DA and P. seriata. The strongest relationship identified was between P. seriata abundances two weeks following upwelling events at Newport Beach.;Blooms of Pseudo-nitzschia can develop at depth in offshore waters not encompassed by coastal HAB monitoring programs. California sea lions are predominately associated with DA mortality events on the US west coast undoubtedly due to their large population sizes and overlapping distribution with Pseud-nitzschia. Quantifying the amount of DA in these animals and correlating this information with the presence of DA in phytoplankton and the local food web has become a research focus for many scientists. However differences in materials, equipment, technical capability, budgets and objectives of the various groups and/or agencies involved in this work have influenced the DA quantification platforms employed. The performance of two commercially available enzyme-linked immunosorbent assays for the analysis of DA in a spectrum of California sea lion body fluids was compared to the results obtained with liquid chromatography-mass spectrometry of the same samples. The results indicated differences among these approaches, presumably owing to matrix effects (particularly urine) and antibody reactivities.;The Orange County Sanitation District diverted flow of secondarily treated effluent from a discharge pipe located 8.0 km offshore at 60 m depth to a pipe located 1.6 km from shore at 17 m depth for three weeks in September of 2012. Two incubation experiments were performed to examine the influence of treated effluent at various dilutions on natural, coastal phytoplankton communities, the first initiated a week prior to the diversion ('Pre-Diversion') and the second initiated a week after the start of the diversion ('Mid-Diversion'). The overall community response observed in both experiments following effluent addition was an increase in diatom and picoeukaryote abundances, a decrease in picophotocyanobacteria and a dramatic increase in heterotrophic bacteria abundance. The 1:10 effluent additions yielded significant increases in chlorophyll a concentrations, although the Pre-Diversion 1:10 experiments exhibited a lag in response to effluent addition. The DA producing diatom Pseudo-nitzschia was present throughout both experiments, however DA production was only detected in the Mid-Diversion experiment. The highest concentration of DA measured, 0.42 +/- 0.057 microg/L coincided with phosphate and silicate concentrations below the detection limit of the method, suggesting limitation by these macronutrients. (Abstract shortened by UMI.).