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New Study Links Sea Foam to Unexplained Seabird Deaths and Strandings

seabird feathers

The effects of sea foam produced by a massive bloom of Akashiwo sanguinea algae. While the algae were nontoxic, the sea foam produced as a residue from the decaying organisms matted down the protective feathers of hundreds of migrating seabirds, exposing their skin to the cold sea. A total of 550 birds were stranded and 207 died during this event.

(photo courtesy of Laura Miller, California Department of Fish and Game)

A new study published in the online journal PLoS One documents the first known case of foam produced by a bloom of nontoxic algae causing the death and strandings of seabirds.

In 2007, hundreds of birds were found stranded or dead in California’s Monterey Bay, coated with an unknown yellow-green substance that was eating away at the protective covering on their feathers.

Dr. Raphael Kudela, one of the authors of the study, said that the cause of the strandings was initially a mystery.

While there was an ongoing bloom of algae in Monterey Bay at the time, this 'red tide' consisted of organisms that didn't show any signs of toxicity.

"Marine birds were coming into the bird rescue centers and they were exhibiting basically oil-spill type signs where they were coated with some material," he said, "They were having trouble cleaning themselves, and they were actually showing up on the beach dead."

Kudela, an associate professor of ocean sciences at the University of California in Santa Cruz, is an investigator funded by NOAA's Monitoring and Event Response of Harmful Algal Blooms program.

At the time of the strandings, a ship named the Cosco Busan had recently struck the Golden Gate Bridge in San Francisco Bay, dumping 58,000 gallons of bunker oil into the ocean. Since it was the time of year when the seabirds were migrating South, researchers thought that the stranded birds may have been exposed to oil spilled from this ship.

"The very first thing we thought was that the birds had simply managed to get from San Francisco to Monterey, which is a little bit far, but not unreasonable," Kudela said.

red tide sampling from Monterey Bay, California

A red tide sample collected in Monterey Bay in 2006. The frequency of red tide events in the Bay have been on the rise in recent years.

(photo courtesy of Raphael Kudela, University of California at Santa Cruz, Ocean Sciences Department)

Upon analysis, however, the California Department of Fish and Game found no evidence of petroleum products, fish oil, or any other sign that the yellow-green substance on the birds came from a human contaminant.

At that point, Dave Jessup, a researcher with the California Department of Fish and Game and the lead author of the study, suggested that the researchers turn their attention back to the ongoing red tide in Monterey Bay.

To their surprise, Jessup discovered that a time series of satellite images of the red tide in the Bay overlaid with coastal currents predicted where the bird strandings were occurring.  These surface currents, revealed by high frequency radar systems, were served through the national Integrated Ocean Observing System.

These radar systems measure speed and direction of ocean surface currents in near real time, which scientists can then use to track the probable path of harmful algal blooms, oil spills, or pollutants.  The data can also support search and rescue operations, water quality assessments, and more.

Part of the imagery and data sent to Jessup also came from a program called CalPReEMPT, the California Program for Regional Enhanced Monitoring for PhycoToxins. NOAA funds several projects like CalPReEMPT along the Pacific coast. These projects focus on improving red tide monitoring and prediction to help communities plan for and deal with environmental and health effects associated with these events.

These new data clearly showed that the red tide and the bird strandings were somehow connected. The next step was to figure out the nature of that connection.

Kudela said the pivotal clue was something that they hadn't paid attention to earlier: sea foam. There was a lot of it in the Bay.

"It looked very much like dirty cool whip, and it had that same sort of consistency," he said.

Testing of the foam determined it was causing the problem. While the algae were not toxic, the sea foam produced as a residue from the decaying algae had qualities similar to detergent. The foam was matting down the birds’ feathers, allowing cold seawater to reach their skin. They were, in effect, freezing to death.

Kudela said the conditions that produced the foam and brought the seabirds into contact with it was an unusual concurrence of events.

First, the number of red tides in Monterey Bay have been increasing every year and lasting later and later into the year. In 2007, the red tide showed up in August and persisted all the way until late December.

Second, surface currents were weak that year, keeping the red tide in one place.

Akashiwo sanguinea

A close up of Akashiwo sanguinea. The deaths of hundreds of seabirds were linked to a soap-like foam produced by this red-tide algae.

(photo courtesy of Rapheal Kudela, University of California at Santa Cruz, Ocean Sciences Department)

Third, seasonal swells moved into the Bay in late November, churning up the algae, producing lots of sea foam – just in time to snare flocks of migrating seabirds making their way through central California on their way to winter feeding grounds.

It may not have been the first time that this has happened in Monterey Bay. There was a similar event about ten years earlier, but at the time the mystery of the deaths and strandings of seabirds went unsolved. When Kudela's team checked the records, it turned out there was a red tide in the area at the same time.

"Ten years ago, it was a mystery still, and they said 'well, it's not a petroleum product and that's all we know, and so we're just going to chalk it up to some unknown event,'" Kudela said, "And ten years later, in 2007, because NOAA and other agencies have really been pushing that we need to answer these questions with all the disciplines working together, we've been able to go from saying 'it's an unknown mystery spill' to saying 'this is exactly what happened and this has never been seen before.'"

The study of the mysterious seabird strandings brought together specialists from areas as diverse as red tides, seabirds, animal medicine, water pollution, ocean monitoring, and ocean currents. The authors of the study came from the California Department of Fish and Game, the Monterey Bay Aquarium Research Institute, the Ocean Sciences Department and Institute for Marine Sciences at the University of California Santa Cruz, and Moss Landing Marine Laboratory.

The study was funded in part by the National Centers for Coastal Ocean Science’s Center for Sponsored Coastal Ocean Research.