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A Regional Comparison of Upwelling and Coastal Land Use Patterns on the Development of HAB Hotspots Along the California Coast

Project Status: This project began in January 2011 and was completed in December 2016

We are comparing coastal “hot spots” of harmful algal blooms (HABs) in central and southern California to determine why hot spots exist and how human influences, such as nutrient runoff, and natural upwelling of deep ocean water interact to cause blooms. Models will predict bloom emergence via remote sensing and routine monitoring techniques. The focus is primarily on toxic Pseudo-nitzschia. We will improve monitoring and develop predictive models for early warning of HABs and their impacts.

Why We Care
Blooms of Pseudo-nitzschia occur at “hot spots” scattered along the west coast. Some Pseudo-nitzschia species produce a potent neurotoxin, domoic acid that can accumulate in shellfish, other invertebrates, and sometimes fish, leading to illness and death in a variety of birds and marine mammals and necessitating shellfish harvesting closures to protect human health. In California, blooms of toxic Pseudo-nitzschia now problematically recur; these blooms were first reported in central California during the 1990s and on an annual basis in southern California since 2003.

NCCOS-funded projects are already examining hot spots in Washington and Oregon; these regions are thought to be primarily influenced by natural processes. Two recently completed projects in southern and central California have demonstrated from shore-based sampling that HAB hot spots are present in California, and led to the hypothesis that human activities as well as upwelling may be stimulating HAB growth.  However, no oceanographic studies aim at understanding the relative contribution of human influences and natural processes causing HABs.

We are comparing HAB initiation and development at two California hot spots where the relative importance of upwelling and human activities differs. Although the project focuses on Pseudo-nitzschia, the occurrence of other HABs, especially Alexandrium, will also be investigated if they occur during the study.

What We Are Doing
Over a period of 5 years there will be three intensive field sampling years in two regions combined with physical and statistical models. They will rely on cutting-edge, high tech, tiered sampling methodology, including existing shore-based monitoring efforts, deployment of two remotely operated underwater vehicles (gliders) with chlorophyll sensors, and two Environmental Sample Processors with sensors for cell/toxin detection (one in each region) on moorings. The sampling data plus satellite imagery will be assimilated into physical and statistical models to identify potential cell/toxin initiation events. When a possible HAB is detected ship-based field experiments will be conducted to assess species assemblage, growth conditions, toxicity, and response to fundamental parameters such as temperature, light, nutrients.
The purposes of the sampling are:

  • to develop a better understanding of HAB initiation and bloom dynamics in California in response to physical and environmental forcing factors, leading to predictive models, 
  • to develop a cutting-edge HAB alert detection system, and
  • to demonstrate the utility of an integrated observing system for HABs as part of the Regional Coastal Ocean Observing System.

The two sampling locations are:

  1. Monterey Bay in central California that represents an open embayment strongly affected by upwelling, and where extensive agricultural use of coastal land influences river outflow and land runoff.
  2. San Pedro Shelf area in southern California, which experiences some degree of coastal upwelling (with significant eddying around the Channel Islands) but situates near a highly urbanized region of the country (greater Los Angeles), and thus influenced by very different chemical composition of runoff, river output and sewage discharges.

The first major field year focused on the Orange County Sewage District diversion of wastewater effluent from the main pipe (located 5 miles offshore and at depth of 60 meters) to a short pipe (1 mile offshore and 17 meters deep) to evaluate the main pipe for maintenance. The diversion occurred in September/October 2012. An earlier, very short diversion resulted in an algal bloom dominated by dinoflagellates and included the potentially harmful Akashiwo sanguinea and Cochlodinium fulvescens. This diversion represented an unparalleled opportunity to investigate the impact of large increases in nutrients derived from human activities on a natural ecosystem. Many regional scientific and management organizations monitored the impact of the diversion using an unprecedented, diverse array of new and proven technologies.

The multi-disciplinary and multi-institutional project team is led by Dr. Raphael Kudela of the University of California at Santa Cruz with co-investigations from the University of Southern California, University of California at Los Angeles, NOAA National Centers for Coastal Ocean Science, Southern California Coastal Water Research Project, California State University-Moss Landing Marine Laboratories, and the Monterey Bay Aquarium Research Institute.  The project collaborates with Central and Northern California Ocean Observing System (CeNCOOS) and Southern California Ocean Observing System (SCOOS), regional associations for coastal and ocean observing and the California Harmful Algal Bloom Monitoring and Alert Program (CalHABMAP).

Benefits of Our Work
Our work will lead to improved models and monitoring that provide early warning of HAB events and impacts, which will in turn aid state managers and local wildlife rescue groups. If human activities are found to stimulate HAB occurrence in some regions, it may lead to strategies for HAB prevention.

Region of Study: California

Primary Contact: Quay Dortch

Research Theme: Harmful Algal Blooms 

Related NCCOS Center: CSCOR

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