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9 April 2014 Share This Share this article

Study of harmful algal blooms builds on year-to-year experience

Note: Preliminary observations from the Spring ECOHAB experiment are desribed here

This satellite image shows the temperature of the ocean surface in and around San Pedro Bay on April 2, 2014. The purple and blue areas have colder water, possibly due to "upwelling" of cold water near the north end of the bay. The red lines show the courses of underwater gliders. The white crosses labeled "Mack" and "Bruce" indicate the locations of Environmental Sample Processors that are being used in the ECOHAB experiment. Image: © 2014 MBARI
In late March 2014, like stealthy electronic sharks, two underwater gliders began cruising the ocean in and around San Pedro Bay, off Southern California. But instead of looking for a meal of fish or sea lions, these robotic vehicles were looking for signs of microscopic algae. These gliders are just the first of a small menagerie of instruments that scientists will be placing in the ocean over the next month to track harmful algal blooms as part of this year’s spring ECOHAB (Ecology and Oceanography of Harmful Algal Blooms) experiment.

2014 marks the third year of the ECOHAB project, which is sponsored by the National Oceanic and Atmospheric Administration (NOAA) and includes researchers from MBARI; the University of California, Santa Cruz; Moss Landing Marine Laboratories; the University of Southern California; the Southern California Coastal Water Research Project; NOAA's National Centers for Coastal Ocean Science; and NASA.

The short-term goal of the ECOHAB project is to determine what environmental conditions are likely to lead to harmful algal blooms. The long-term goal is to build computer models that will allow researchers to predict when and where blooms are most likely to occur.

This year, the researchers will be building on discoveries made during previous ECOHAB experiments conducted in San Pedro Bay in the spring of 2010 and 2013. These experiments indicated that harmful algal blooms often occured in April. This finding prompted researchers to schedule the 2014 experiment during this month.

These images show two views of data collected by an underwater glider during late March, 2014. The zig-zag line shows the path of the glider as it traveled across San Pedro Bay and over deeper water offshore (to the left); the vertical scale is enlarged in the lower image. The colors of the line represent different concentrations of chlorophyll. The deep-red patch near shore (upper right) indicates high chlorophyll concentrations associated with an algal bloom. Image: © 2014 MBARI
In addition to the underwater gliders, two robotic DNA labs known as Environmental Sample Processors (ESPs) have already been moored at two locations in the bay. The ESPs are being used to identify types and concentrations of algae and measure the toxins they produce in real time. By the time the experiment reaches its peak in mid April, ECOHAB scientists will be collecting data from the two ESPs, two research vessels, five autonomous underwater vehicles (AUVs), and five drifters.

MBARI’s long-range AUV Daphne will patrol the waters around the ESPs, collecting information on the temperature and chemistry of the water as well as the total amount of algae present. Meanwhile, MBARI’s Dorado AUV will travel back and forth across San Pedro Bay, gathering data and collecting water samples using its on-board artificial intelligence system to identify patches of algae. Along with data collected from ship-board sampling systems and moorings, the AUV data will allow researchers to know when and where harmful blooms are occurring and to examine the processes controlling these blooms.

The large amount of data flowing from all of these observing system components will be challenging to process and analyze. However, software developed by MBARI will enable researchers to manage and visualize the data in real-time. This will help them make day-to-day decisions throughout the experiment.

Algal blooms develop off the California coast in the spring, when blustery northwest winds push surface waters away from the coast. This allows nutrient-rich water to rise up toward the surface. The resulting “upwelled” water acts like fertilizer for diatoms and dinoflagellates—the microscopic algae that dominate California’s coastal waters. Although upwelling is particularly intense in exposed coastal areas such as Monterey Bay (another ECOHAB study site), it also plays a role in producing blooms in the more sheltered waters of San Pedro Bay.

MBARI Postdoctoral Fellow Holly Bowers collects microscopic algae using a plankton net during the 2013 ECOHAB experiment. Image: John Ryan © 2013 MBARI
Data from last year’s ECOHAB experiment suggested that two different types of upwelling may affect San Pedro Bay. In addition to upwelling generated by regional northwest winds blowing in the Catalina Channel, upwelling may also be generated in northern San Pedro Bay by brisk afternoon sea breezes. One of the challenges of this year’s experiment will be to determine the relative effects of these two types of upwelling on microscopic algae.

Another exciting result from the 2013 experiment was that researchers discovered a surprising amount of diversity within one group of harmful algae, and learned how the different species within this group were distributed in the water column. After analyzing hundreds of water samples from the 2013 experiment, MBARI Postdoctoral Fellow Holly Bowers found several different species of diatoms in the genus Pseudo-nitzschia that are capable of producing a potent neurotoxin called domoic acid.

ECOHAB researchers are also interested in understanding how the effects of nutrients in upwelled water compare with the effects of nutrients introduced by human-related activities such as urban runoff and sewage disposal in the ocean. This year’s dry winter, followed by late rains, may provide data to help answer this question.

By building on the results of the 2013 ECOHAB experiment, the research team is optimistic that they will get even more useful data this year. As John Ryan, chief scientist on this year’s ECOHAB cruise aboard the R/V Rachel Carson explained, “The data show that our 2013 sampling and monitoring strategy was good. The instruments were in the right place. We were just a bit early. Early indications this year are that we arrived at the right time.”

Note: At the same time as MBARI researchers are busy with the ECOHAB experiment in Southern California, a related project, funded by NOAA's MERHAB program, will be underway in the Gulf of Maine, under the direction of Woods Hole Oceanographic Institution (WHOI) Senior Scientist Don Anderson. In this experiment, four different ESPs will be used to monitor blooms of a microscopic alga that can cause paralytic shellfish poisoning (PSP) in humans. The ESPs in the Gulf of Maine will also carry a sensor developed by NOAA’s National Centers for Coastal Ocean Science and WHOI that can measure concentrations of the PSP toxin. The data from these ESPs will complement state-run programs that monitor PSP and naturally occurring marine toxins in shellfish.

For more information on this article, please contact Kim Fulton-Bennett:
(831) 775-1835,

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