Marine and Freshwater Algal Toxins Co-occur at the Land-Sea Interface in Coastal California

Miranda Roethler, Southern California Coastal Water Research Project, Costa Mesa, CA, United States, Meredith D.A, Howard, Central Valley Regional Water Quality Control Board, Rancho Cordova, CA, United States, David A Caron, University of Southern California, Biological Sciences, Los Angeles, CA, United States, Raphael Martin Kudela, University of California Santa Cruz, Santa Cruz, United States, Kendra Negrey, University of California Santa Cruz, Ocean Sciences, Santa Cruz, CA, United States, Avery O Tatters, University of California Los Angeles, California NanoSystems Institute, Los Angeles, CA, United States and Jayme Smith, Southern California Coastal Water Research Project, Costa Mesa, United States
Abstract:
Harmful algal blooms (HABs) are a persistent problem in aquatic environments, particularly in California where waterbodies are often characterized by high nutrient loading and low flow. Although most HAB research focuses exclusively on either marine or freshwater algal toxins, recent work has shown that freshwater toxins from cyanobacteria blooms can be transported through the watershed and into estuarine and marine environments. Freshwater toxins may be present regularly at the land-sea interface, yet are rarely monitored in marine environments. The goal of this work was to determine the diversity and concentration of marine and freshwater HABs toxins in estuaries and nearshore coastal zones in California. We also studied the temporal patterns of algal toxins in these systems and whether freshwater toxins were episodically or constantly present in these environments. Seven estuarine and nearshore stations in California were sampled monthly in 2017, using both water grabs and passive samplers (Solid Phase Adsorption Toxin Tracking). Algal toxins, dissolved nutrients and algal taxonomy were measured, along with environmental parameters (temperature, salinity, pH, alkalinity). Analyses revealed that cyanotoxins and marine toxins are relatively ubiquitous and consistently present in estuaries throughout California. Microcystin, anatoxin-a, okadaic acid, and domoic acid were all routinely present in multiple locations, and in many locations two or more algal toxin classes co-occurred. Toxins were most abundant and diverse during the fall, particularly in the Klamath River Estuary and Santa Cruz Wharf. PCA analysis revealed that different geographic areas were influenced by different suites of environmental variables. This study demonstrates the value of using passive samplers as a complimentary technique to traditional whole water samples in HAB monitoring studies, as they may detect long-term environmental signals missed by single-timepoint sampling techniques.
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