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This week, we take a virtual journey to San Diego for the annual meeting of the American Association for the Advancement of Science.
At the event, NOAA’s Oceans and Human Health Initiative unveiled six new studies this week. These studies offer new insights into how diseases found in dolphins and other marine mammals are similar to humans, and the studies provide new clues into how the health of these mammals are being impacted by degraded oceans.
Today, we’re going to talk with NOAA scientists who led two of the six studies presented at the meeting to learn more about their new research. After the show, be sure to head over to oceanservice.noaa.gov. There, you’ll find a round up of all the new science presented at this NOAA symposium.
It’s Thursday, February 18th, and you’re listening to Making Waves from NOAA’s National Ocean Service.
(Dolphins and PCBs)
Our first story today is about polychlorinated biphenyls, or PCBs. The term PCB covers a wide range of manmade contaminants that have been banned in the U.S. since the 1970s because they are very harmful to animals and to humans, and they have a nasty tendency to stick around in the environment for a long, long time.
Last summer, Dr. Lori Schwacke, a NOAA wildlife epidemiologist and biostatistician, co-led a study with investigators from NOAA’s National Marine Fisheries Service to test the levels of these chemicals in dolphins that live near an industrial site near Brunswick, Georgia. We spoke with Lori on the phone at her office at NOAA’s Hollings Marine Lab in Charleston, South Carolina, where she works as the principal scientist for NOAA's Oceans and Human Health Initiative Center of Excellence.
She said her team expected to find high levels of contaminates in the dolphins that lived in the waterways near this area, but what they found were levels of PCBs that were higher than have ever been seen in any other marine mammals:
“They were even higher than levels that we’re measuring in transient killer whales in the Pacific Coast. These are the transient pods of killer whales that feed on other marine mammals, so they’re at an even higher level of the food chain and before have been reported as having the highest levels of persistent contaminants in wildlife, but these dolphins have beat them out with even higher levels.’
After they tested the dolphins in this area, they moved 30 miles up the coast to test dolphins at the Sapelo Island National Estuarine Research Reserve, where they expected the levels to be much lower.
“This is a beautifully scenic area, with very little development in the area, and we anticipated -- we originally moved up there thinking that we wanted to investigate health impacts of these contaminants that this would be a good control site. And we found that levels in that region were also around 140 parts per million, which is higher actually than what’s been seen in other coastal sites. It’s still lower than Brunswick, significantly lower than Brunswick, still higher than what we anticipated.”
After the saw such unexpectedly high levels of PCBs in the dolphins in this area, too, they decided to medically examine some of the dolphins at the Brunswick site and at the Sapelo reserve.
“So far we only have preliminary results, but we’re seeing evidence of suppressed immune function, altered level of thyroid hormones, and elevated liver enzymes.”
By tagging the dolphins, they were also able to track their movements. What they found is that a few of the male dolphins were moving up and down the coast, but mostly the dolphins didn’t range that far. This suggests that the contaminants are moving along the coast through the marine food web.
Lori said the knowledge gained by this study adds to what scientists know about cetaceans -- the group of marine mammals that includes dolphins, porpoises and whales. It turns out not much is known because these types of mammals are really hard to study in the wild.
“It’s been difficult for scientists to get a firm handle on how much of a risk these contaminants really pose to the health and sustainability of cetacean populations. Because this population along the Georgia coast has such incredibly high levels of PCBs, it’s a good opportunity for us to study and understand the impacts that PCBs can have, specifically on cetacean health.”
Now the big question is, what effects are these PCBs having on the dolphins ... and on humans?
“A number of adverse health effects have been associated with PCB exposure in both humans and animals. The primary effects include lowered immune response, which can cause increased susceptibility to disease; poor cognitive development; liver damage; and impaired reproduction. Also, some PCBs are endocrine disruptors and can alter levels of thyroid or reproductive hormones, so there are a number of reasons to be concerned about the high levels of PCBs we’re seeing in these dolphins.”
Because of the unprecedented levels of PCBs that Lori’s team found in the dolphins in this area, other studies are already underway or planned. The National Center for Environmental Health, for example -- that’s part of the Centers for Disease Control -- is looking at how seafood may contribute to what’s called the ‘body burden’ of environmental contaminants in coastal communities. They’re planning to do a pilot study with volunteers who live in the area near the Sapelo Island reserve who eat local seafood to understand whether marine mammal populations and humans in the same area who share the same seafood resources also share similar exposures to PCBs from their diet.
While there is much more to learn about the problem in this region, Lori said one thing is already very clear:
“ We have to be careful with what we’re doing on our coasts. I mean, these contimants have been banned in the U.S. since the 1970s, yet here we’re seeing incredibly high levels in dolphins, and the health of these dolphins could be impacted by them, and could be impacting the health of people who consume seafood in the same area. These contaminants don’t go away, they last for generations, so I think what we have to think about is that the pollutants we’re allowing to seep from our coasts into our waters today are going to be around for decades to come.”
(HABs and Epilepsy)
Our next story is not about manmade toxic chemicals in our coastal waters, it’s about toxins produced by algae, little microscopic plants that live in the ocean.
What we’re talking about here are harmful algal blooms, more commonly known as red tides. Well there’s a particular kind of algae that sometimes grows out of control, and when it does so, it produces a toxin called domoic acid. This is nasty stuff, and that’s something we’ve known for years. But in a new study unveiled at the symposium, Dr. James Ramsdell discovered that this toxin can produce lasting effects on mammals. It can lead to seizures that can lead to epilepsy.
We talked to John by telephone from his offices in South Carolina, we’re he works as a research physiologist and chief of the Harmful Algal Blooms and Analytical Response Branch at NOAA's Center for Coastal Environmental Health and Biomolecular Research.
We asked him about the kind of algae that produce the toxin known as domoic acid.
“These are very common algae. In fact, as opposed to most of the harmful algal blooms which are composed of dinoflagelletes, which are thought to be more of the ‘rogue‘ type of plant cells in the marine environment, these toxins are made by diatoms, which are generally thought to be fairly benign and very productive parts of the marine ecosystem.”
But he added that not all of these types of algae always produce this type of toxin. Certain conditions have to be met. First, there have to be the right conditions to create a big bloom of algae -- this has to do with ocean currents and temperatures that help to concentrate a large number of these plants in one area. Then, all of these plants need food, right? Well, they’re fed by things like runoff of manmade nutrients coming from the land from things like fertilizers. What happens is that when these nutrients run out, this mass of algae starts to run out of food, they get stressed out, and that’s when they start producing the toxin. And when marine mammals like dolphins and sea lions eat fish that have eaten this algae, they’re poisoned. It’s a pattern that John said is well documented, but there was a mystery that was unresolved. Over the past decade, scientists at the Marine Mammal Center in Sausalito, Calif., had documented many cases of sea lions that were showing signs of domoic acid poisoning and having epileptic seizures long after the algae had come and gone ...
“And they found that some sea lions were stranding with domoic acid symptoms at times when there were not blooms. Simultaneously, they had been following many of these animals in their clinics for extended periods, and they’d find that after the animal recovered from its acute seizures and seemed to be OK, all of the sudden they’d start to develop epilepsy again.”
So the question at hand was if domoic acid could cause epilepsy in the long term. John said that researchers had tried to prove this link before, but without success. He decided to tackle the problem again using rats as a model in the laboratory. He said that scientists knew pretty well that domoic acid could cause seizures, but ...
“...what we didn’t know was the long term consequences of this. And so, we had to be very careful with domoic acid, because it’s a toxin and it’s lethal. And I think the reason the previous work did not work well -- the previous attempts to show that domoic acid could induce epilepsy -- was that it killed the animals before it could before it could cause enough damage.”
So what they did is use a really small dose of domoic acid in the rats, just enough to induce epilepsy once, then they stopped. And they took really good care of the rats and just waited to see what would happen.
“What we found was that, over the course of six months, 92 percent of the animals became epileptic.”
John said that the important point is that the domoic acid doesn’t cause epilepsy, it’s that the toxin causes seizures that damage the brain, and this damage to the brain leads to lifelong epilepsy in almost all of the rats his team tested in the lab. It’s a similar pattern to what can happen to humans when exposed to factors like high fevers during childhood, brain trauma, or exposure to lead.
“So the real common denominator is the damage to specific areas in the brain, and there are multiple ways to cause that damage to lead to this.”
So as you listen to this, you may be asking yourself if it’s safe to eat seafood given the threat posed by these toxin-producing algae.
“In terms of domoic acid poisioning from seafood, most seafood is monitored pretty carefully. But it’s very unusual to get enough domoic acid in seafood to make a normal person sick, particularly a healthy person. Over all, domoic acid is particularly a risk to those people who have problems with their kidneys or advanced age, but generally it’s not a big hazard to healthy people.”
The knowledge gained from this new study will help guide future research and emergency response efforts for future harmful algal bloom outbreaks. John stressed that harmful algal blooms are going to continue to happen, so we need to continue to learn more about them so we can better manage them. He added that we also need to recognize that human activities may be playing a significant role in prolonging these toxin-producing phenomena:
“Harmful algal blooms are a natural phenomena, and they’re going to happen. However, it’s quite likely that human influences do prolong them. For example, pollution provides nutrients that can prolong their growth and problematic effects -- it won’t cause them, but it will prolong them. Likewise, the destruction of wetlands is a very big factor. You know, wetlands are the filters for many of the natural nutrients as well as poisonous things that come off the land, and when one lacks these filters, once again you’re going to enhance the effects. And those could well be contributing to the more intense blooms and more intense animal mortality events we’re observing.”
A special thanks to Dr. Lori Swchacke and Dr. John Ramsdell for taking the time to discuss their latest research.
Don’t forget that you can find more about these studies and the other research announced this week at the American Association for the Advancement of Science meeting this week. Just surf over to oceanservice.noaa.gov.
If you have any questions about this week’s podcast, about the National Ocean Service, or about our ocean -- or if you have an ocean fact you’d like answered -- send us a note at email@example.com.
Now let’s bring in the ocean....
This is Making Waves from NOAA’s National Ocean Service.