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In 2007, hundreds of seabirds were found stranded or dead in California’s Monterey Bay. The birds were coated with an unknown yellow-green substance that was eating away at the coating and oils on their feathers. Without this protection, the birds were vulnerable, starving, and suffering from hypothermia. When it was all over, a total of 550 birds were stranded and 207 died during this unexplained event.
In a study partly funded by NOAA, scientists in California recently solved this puzzling case and published their findings last week in the online journal PloS One. Today, we hear from one of the authors of the study to learn what happened.
It's Friday, March 6th, and this is Making Waves from NOAA's National Ocean Service.
What caused the mysterious strandings and deaths of so many seabirds? Dr. Raphael Kudela, one of the authors of the new study, said the cause wasn't readily apparent at the time.
DR. KUDELA: "Right about Thanksgiving of 2007 there started to be a series of bird strandings, so 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, they were having trouble cleaning themselves, and they were actually showing up on the beach dead. And they looked otherwise healthy."
Kudela is an associate professor of ocean science at the University of California in Santa Cruz. He's also an investigator funded by NOAA's Monitoring and Event Response of Harmful Algal Blooms program. A more common name for an algal bloom is a 'red tide,' and as it turned out, there was a big red tide happening in Monterey Bay at the time of the strandings. But scientists already knew that the algae turning the waters red in the Bay weren't the kind of organisms that produce toxins that could harm marine life.
So attention turned to another possible culprit: farther north, 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, they could have been exposed to oil spilled from this ship.
DR. KUDELA: "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."
In cases like this when there are large numbers of strandings and deaths, the California Department of Fish and Game will investigate if there is a human source--in this case, the Golden Gate spill. But after analyzing some of the Monterey birds, they found no evidence of petroleum products, fish oil, or any other sign that the yellow-green goo 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 new study, suggested that the researchers turn their attention back to the ongoing red tide in Monterey Bay.
DR. KUDELA: "He contacted a number of us and said 'We've got these birds coming in, we don't know why, but there's this big red tide going on. Do you think that could be part of the problem?' And we said, 'well, we've been keeping track of the red tide, but it's generally considered harmless. It's not a toxin producer, it shouldn't be causing any impact, but we'll go ahead and test'"
That test seemed to lead to another dead end. Although no toxins were identified, Jessup still had a hunch. He asked for more data about the red tide event.
DR. KUDELA: "We started sending him images of the red tide using satellite imagery, and we overlaid on that the coastal currents from high frequency radar. And we were very surprised when Dave came back and said, 'well, this is great, you're predicting where the bird strandings will occur about 48 hours in advance.'"
Part of imagery and data sent to Jessup came from a program called CalPReEMPT, the California Program for Regional Enhanced Monitoring for PhycoToxins. PhycoToxins are toxins produced by certain algae when they bloom into so-called 'red tide' events. NOAA is funding several projects like CalPReEMPT along the Pacific coast. These projects focus on making red tide monitoring and prediction better to help communities plan for and deal with environmental and health effects associated with these events.
When the red tide imagery was overlaid with the local currents, it clearly showed that the red tide and the bird strandings were somehow connected. The next step was to figure out just what that connection was. 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.
DR. KUDELA: "It looked very much like dirty cool whip, and it had that same sort of consistency. It's the normal sea foam you get during large algal blooms, but David noticed that where the birds were stranding, there was a lot of this sea foam and the foam was coming from the red tide, because there was a lot of red tide. And so they had this brilliant idea of testing it. "
Dr. Jessup's team collected some sea foam, and rubbed it on some healthy seabird feathers. Sure enough, the sea foam was causing the problem. While the algae wasn't toxic, the sea foam produced as a residue from the decaying algae had qualities similar to detergent. The foam would mat down the birds’ feathers and allow cold seawater to reach their skin. They were, in effect, freezing to death.
This is the first documented case linking foam produced by an algal bloom with the deaths and strandings of hundreds of birds.
Kudela said the conditions that produced the foam and brought the seabirds into contact with it was sort of a perfect storm. First, the number of red tides has been increasing every year ... and they've been occurring 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. Third, seasonal swells moved into the Bay in late November, churning up the algae, and producing lots and lots of sea foam – just in time to snare flocks of migrating sea birds making their way through central California on their way to their winter feeding grounds.
DR. KUDELA: "And so those three events together ended up causing this huge bird mortality. And we went back and we looked at the number of strandings was about a factor of six to a factor ten higher than is normal if we look at the last ten years of bird stranding data. And so we had this kind of unusual event when everything came together and caused this impact that nobody has ever reported before. And so we've never seen in the literature that a foam event like this can impact marine birds, but it very clearly did."
But that doesn't necessarily mean it's the first time 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.
DR. KUDELA: "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. And ten years later, 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, and tell the rest of the world that 'if you see an event like this, you should be looking for these things.'"
DR. KUDELA: "For the last ten or fifteen years, we've all been moving towards more interdisciplinary science. That's where the really exciting things are and that's where we're really going to solve some of these issues, and I think NOAA has done a fantastic job at taking the lead on that. If we look at something like harmful algal blooms, the biology is really important, but these organisms are in the ocean, so we can't ignore the physics, the chemistry, and the weather, and everything else, because if we do ignore that, we're never going to solve the problem because it's a complex and complicated problem."
The study of the mysterious seabird strandings not only brought researchers from many different fields together, it also brought together people and resources from state, federal, academic, and non-profit organizations. 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.
That was Dr. Raphael Kudela helping us piece together the clues that led to his team’s solving the mystery of the 2007 mass bird deaths in California. Dr. Kudela is an associate professor of ocean science at the University of California in Santa Cruz and an investigator funded by NOAA's Monitoring and Event Response of Harmful Algal Blooms program. The study was funded in part by NOAA's Center for Sponsored Coastal Ocean Research, as well as the Integrated Ocean Observing System.
Well, that's all for this week.
If you have any questions about this episode, about our oceans, or about the National Ocean Service, send us an email at email@example.com.
Don't miss next week's episode. In recognition of the 20th anniversary of the Exxon Valdez oil spill in Alaska, we're going to talk with Dr. Alan Mearns, a marine ecologist at NOAA's Hazardous Materials Response Division in the Office of Response and Restoration. Dr. Mearns was not only on-scene during the clean up of the Exxon Valdez oil spill, but he also led a long-term monitoring survey to document the recovery of injured shoreline marine life in Prince William Sound.
And don't forget that you can visit us online at oceanservice.noaa.gov. There you'll find an accompanying print story about the study we discussed today, and you'll links to all of the offices and programs we've mentioned in this podcast.
Now let's bring in the ocean.
This is Making Waves from NOAA's National Ocean Service.