Some researchers point to climate change in algae blooms and other water woes

10/28/13 Janelle Irwin
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Tags: water, algae, nutrient pollution, climate change, global warming, fisheries, the Gulf of Mexico


Stony Brook University professor Christopher Gobler explains the effects of ocean acidification on fisheries.

photo by Janelle Irwin

Scientists are studying the effects of harmful algae blooms on water supplies and ecosystems. During a five-day symposium in Sarasota looking at the science behind algae blooms and other harmful outbreaks, experts tied increasing water problems to climate change. Patricia Tester, a researcher with the National Oceanic and Atmospheric Administration, studies bacteria that cause Ciguatera fish poisoning.

“The Food and Drug Administration picked up Ciguatera fish poisoning cases in different locations from Washington D.C. and St. Louis and perhaps it was because it was happening in more populous areas that it got the attention. However, those fish were traced back to being caught in the area near the Flower Garden Banks National Marine Sanctuary and for that reason, the Food and Drug Administration said there was a reasonable likelihood that Grouper and Snapper and Hogfish captured within ten miles of those salt domes could be harmful.”

The Flower Garden Banks are located about 200 miles off the coast of Texas in the northern Gulf of Mexico. Bacteria that contribute to Ciguatera fish poisoning have a lower survival rate in cooler water.

“So, if we decide to move forward to the end of the century and look at water temperatures there from what the models are telling us, it’s going to be about a two degree increase in the northern Gulf of Mexico. So, if you overlay that two degree increase on our bottom water temperatures for that region, we’re going to see about 55 more days of optimal growth time at the East and West banks and about 46 more days at Stetson Banks.”

Similar effects are being studied in other parts of the world too. Hans Paerl, a UNC Chapel Hill professor of Marine Science, used a water basin in a town in China called Taihu as an example. The increased algae blooms there are rendering the water supply often unsafe.

“You have a huge excess of nitrogen in the Spring – most of it coming from runoff and agricultural inputs – then the bloom develops and sucks all the nitrogen out of the water and the system becomes nitrogen limited and you actually have free orthophosphate in the water. So, you’ve got a situation where nitrogen is limiting in the Summer, phosphorus, we think, in the Spring. ... And that repeats itself … Our hypothesis has been that we’re probably going to need to deal with both nutrients.”

He also suspects that some of the nutrient imbalances that lead to algae blooms are being furthered by global warming trends.

“This is the air temperature in Shanghai for about thirty years or so, and the recent warming trend – you can see the surface water temperature in Taihu has increased … and you can see this really, really dramatic spike most recently and we don’t think that’s just nutrients. We think there is an interaction there with warming…”

Fisheries are also at risk if nutrient pollution, which contributes to harmful algae blooms, isn’t kept in check. An excess of carbon dioxide in water can affect the pH and lead to brown tide. Water in those areas becomes more acidic. Christopher Gobler from Stony Brook University in New York says some species affected include scallops, muscles and clams.

“They’re calcifying larvae and therefore high levels of CO2 interferes with their ability to calcify and so, that’s sort of the ocean acidification effect that a lot of people have looked at. We also see that Aureococcus knocks down their survival significantly and when they’re exposed to both stressors there’s actually a synergistic effect. That is to say, statistically, this is lower survival than would have been predicted from either individual stressor.”

Not all species are affected by ocean acidification, but what other fisheries could be affected is still being studied.

The seventh annual symposium on harmful algae blooms is being held through Thursday at the Sarasota Hyatt Regency Hotel.

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