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You're listening to Making Waves from NOAA's National Ocean Service.
It's summertime! That means it's time for trips to the beach, vacations ... and re-runs! We have a previously-aired episode for you today, but you may not have heard this one before. That's because we had a problem with our syndicated feed when this episode came out back in March, so you may have not even known it was released. And that would be a shame, because it's a really interesting episode with two scientists talking about their latest research.
Earlier this year, thousands of people descended on Washington, DC, for the 177th American Association for the Advancement of Science meeting. Today, you're going to hear about two studies funded in part by NOAA's Oceans and Human Health Initiative presented at the science gathering on Feb. 19th, 2011. Broadly speaking, this new research is related to climate change. You've probably heard of climate change studies that deal with big-picture things like drought or sea level rise ... well, these new studies look at the problem from a different angle and on a smaller scale. Let's listen in.
Our first story today is about a new study that considers how global desertification -- the gradual transformation of habitable land into desert -- may help fuel the growth of harmful bacteria in the ocean.
Dr. Erin Lipp is the lead author of the study. Erin's a public health microbiologist and marine scientist at the University of Georgia's Department of Environmental Health Science. I caught up with her after she presented her research at the meeting to learn more about the study. Erin said her team focused on a group of ocean organisms that share the scientific name Vibrio. While many types of harmful bacteria in the ocean come from land-based sources like sewage, Vibrio is different because it naturally occurs in the marine environment.
For this study, her team experimented with two species of this organism that can cause gastroenteritis and infectious diseases in humans.
[Lipp] "We used Vibrio cholerae, which is the species that causes epidemic cholera. We also used the species Vibrio alginolyticus, they're similar in some ways, but quite different in others. Vibrio cholerae is of course notorious for causing a very severe disease. Vibrio alginolyticus is growing in importance, especially in tropical areas, it's one of the main species that we see on an increase, especially in area like Florida. Unlike Cholera, it primarily infects people by wound infections, or it infects their eyes and ears, so the symptoms are much less dramatic, but certainly still a cause for public health concern where people are recreating in marine waters."
Now, to put this in context...since 1996 Vibrio cases have jumped 85 percent in the U.S. based on reports that primarily track seafood-illnesses. So you can see why it'd be a good thing to better understand why we're seeing this trend. Erin said that Vibrio are complex organisms to study because scientists just don't know all the risk factors that can increase their populations. One thing we do know is that Vibrio bacteria do better in warmer marine waters -- that their populations are closely tied to water temperature ...
[Lipp] "...but it's not the only thing that affects that group of organism. It can also be affected by ocean chemistry. A major player in ocean chemistry is the availability of iron. Iron is not well soluble in marine waters, one of the ways we get soluble iron (or bioavailable iron) is through the production and transport of desert dust. And so we were interested in whether or not that desert dust can be a component in the natural population dynamics of Vibrio species."
Iron is an essential ingredient for life for Vibrio bacteria -- along with most other forms of life on the planet. But there's not a lot of iron in the ocean. So dust falling into the sea from the atmosphere is sort of like an iron delivery machine for these microscopic creatures.
[Lipp] "Vibrios, as part of their mechanism of being pathogens, are really, really good at scavenging iron, and so we suspected that with an influx of this dust that comes from desert areas around the world that carries a lot of iron in it, that when the Vibrio bacteria are exposed to that, they may be able to take advantage of it and see an increase in their growth rate."
And that's definitely what they found. Within 24 hours of mixing weathered desert dust from Morocco with seawater samples, they saw a 10-1000-fold growth in Vibrios, including the alginolyticus strain that can cause eye, ear, and open wound infections, and the cholerae strain that can lead to cholera.
With desert areas increasing in size on the planet, some climate change scenarios predict that we're going to see a lot more dust in the atmosphere. In fact, there's evidence that we're already seeing just that. Erin said this study is a small step in linking what's happening on a global scale with population changes at the local level for these types of harmful bacteria. While this study was conducted using ocean water off the coast of Florida, Erin suspects it may be a wider issue.
[Lipp] "The work that we've done has really been focused in the United States and in Florida in particular, but I really suspect this could be a global phenomenon. There are certainly areas of the world that are seeing a rapid expanse in Vibrio exposure, including the Mediterranean, The Mediterranean is an area that gets a lot of desert dust, and so I suspect that this may be something that is going on on a pretty large scale, but we just don't know anything about it yet. So I'm hoping there's going to be further study to look at it."
So it's possible that this additional input of iron through dust, along with rising sea surface temperatures from climate change, are affecting bacterial populations. And that may help to explain both current and future increases in human illnesses from exposure to contaminated seafood and seawater.
The University of Georgia hosts a graduate training consortium with NOAA's Oceans and Human Health Initiative. You can read more about this study on our website at oceanservice.noaa.gov.
Next, we're going to turn our attention to a new model created by researchers in the Pacific Northwest that predicts longer seasonal outbreaks of harmful algal blooms may be in store for Washington State's Puget Sound.
To tell us all about it, we're going to hear from lead author Dr. Stephanie Moore with NOAA's West Coast Center for Oceans and Human Health in Seattle. I spoke with Stephanie a few hours after she presented her findings at the meeting ... and I began with a very basic question: what's a harmful algal bloom?
[Moore] "Well, a harmful algal bloom is a natural phenomena that is caused by the proliferation of algae, so its like an overgrowth of algae. The particular harmful algal bloom species that I've been working on is a uni-cellular algal species -- so it's a single celled organism -- and it grows in coastal environments, and it produces a toxin. Many harmful algal blooms species produce toxins that can accumulate in shellfish and also fish species, and then be passed on to humans or marine mammals."
Now the species Stephanie focused on in Puget Sound -- named Alexandrium catanella -- is particularly toxic. She said it produces a bunch of toxins, but one, called Saxitoxin, is really nasty.
[Moore] "...so what this toxin can do if we consume enough of it, is paralyze the muscles of our chest and abdomen, and then death can result in extreme cases."
Yikes. To make matters worse, there are no known antidotes to saxitoxin, and you can't destroy it by cooking your seafood.
[Moore] "Fortunately, our Departments of Health in the United States do a very good job of monitoring our seafood, so that we don't get sick. So there's not many cases in the United States these days, although in Alaska there's such a big coastline that it's very difficult to get around to monitor all the sites, and two deaths did occur in 2010. So it still poses a significant health risk, and it costs a lot of money to run these monitoring programs. The other big economic associated with these blooms is that the commercial shellfish growers, they can't sell their product during bloom events, so they suffer from huge economic losses during big blooms."
You may be wondering why deaths still occur in Alaska. Stephanie said it's because there just aren't enough resources available to agencies to conduct monitoring on the scale required to protect public health along Alaska's vast coastline. The only option in these remote areas is to close large areas of coastline often unnecessarily for much of the year. The problem with that is that people tend to lose faith in the advisories and collect and eat shellfish anyway ... and sometimes they get sick.
Of course, toxic algal blooms aren't just a problem for Washington State and Alaska. They're a problem in coastal areas around the world. So wouldn't it be good to have an advance warning system to give us a better idea of when to expect these toxic blooms? That's the idea behind Stephanie's research.
What she and her team did is look at a 15-year record of toxic bloom events, focusing on five 'hotspot' areas in the Sound where the most intense toxicity was consistently measured in shellfish. Then they looked at the weather and ocean conditions preceding the times when those most intense toxic conditions were measured -- the idea being that the conditions were ripest to produce the deadly blooms before the high toxin levels were measured. What they found is that ideal conditions to form the deadly toxins were those times when the water was warm, and there was little mixing in the water column. Stephanie calls this the 'window of opportunity.' The next step was to look into the past., back to the 1960s. While there aren't very good shellfish toxicity records spanning back to this time, there are very good records of weather and environmental conditions. This allowed her team to figure out those times -- those 'windows of opportunity' -- when conditions were ripe to form the toxic algal blooms.
[Moore] "And what we found was that the window of opportunity had been widening each year since the late 1960s. And just so that we're clear, a wider window of opportunity means that there's an increased risk of harmful algal bloom events."
So they found more days each year, as time went on, when harmful algal bloom events were likely to occur. The next step was to look to the future, using climate change models to see how those 'windows of opportunity' might change in years to come ... in the 2020s, the 2040s, and out to the 2080s. What they found was that the 'window' will likely continue to widen.
[Moore] "Not only do we see an increase in the number of days in any given month within a typical bloom period, which is from (present day) a typical bloom is from July to October. So we see an increase in the number of days each month during that typical time period from July to October that conditions are favorable for a bloom event, but we also start to see that period widen. So we're starting to see longer bloom seasons as we go out into the future. So much so that by the end of the century, we project that blooms may occur up to two months earlier in the year and persist for one month longer."
What this model can do is give public health authorities and shellfish growers in Puget Sound a much more refined and accurate projection of when they should expect toxic algal blooms.
[Moore] "So if you're a manager, and you're in charge of protecting public health from these toxic events, we want to make sure that they have the information that they need to know when in the year to start looking for a bloom. So the results of our study indicate that we're going to have to be on-guard and looking for these blooms events to be occurring a lot earlier in the year than what we're seeing now."
That's pretty powerful information to have. Not only will coastal managers better know when they should expect harmful blooms, by knowing what sea and air conditions to look for, they may be able to more efficiently open and close smaller areas to shellfish harvesting instead of just closing off a huge swath of coast.
While this study focused on a small area in the Pacific Northwest, the predictive prowess behind the new model may have a big future in helping people in similar coastal areas around the world better prepare for toxic algae outbreaks.
That was Dr. Stephanie Moore from NOAA's West Coast Center for Oceans and Human Health. Check our website at oceanservice.noaa.gov for more details about this new research.
Thanks to Drs. Erin Lipp and Stephanie Moore for joining us today. We only had time to cover two of the three NOAA-funded studies presented at the American Association for the Advancement of Science meeting.
Head to oceanservice.noaa.gov for a detailed look at a third study from Dr. Sandra McLellan of the University of Wisconsin-Milwaukeee School of Freshwater Sciences. You should really check it out. It's about how a changing climate with more rainstorms on the horizon could increase the risk of overflows of dated sewage systems. This could cause the release of disease-causing bacteria, viruses and protozoa into drinking water and onto beaches. Do you live in a city? You may be interested in what this report has to say about urban infrastructure, climate change, and water quality.
Thank you for joining us this week. Write to us as firstname.lastname@example.org if you have any questions or comments about the podcast, the National Ocean Service, or our ocean. And visit us online. Our home on the Web is oceanservice.noaa.gov. And don't forget that you can subscribe to this podcast on our website so you'll never miss an episode … We serve up a feed for your feed reader and we're also on iTunes. You can get those links on our website.
See you in a couple of weeks.