By Daniel Dunaief
Christopher Gobler searches the waters around Long Island for signs of trouble, which can appear starting in April. This year, he found it, in Shinnecock Bay. Monitoring for a toxin carried by algae called Alexandrium, Gobler recently discovered levels that were three times the allowable limit from the Food and Drug Administration. His finding, along with measurements from the New York State Department of Environmental Conservation of toxins in shellfish in the bay, have caused the recent closure of shellfishing in the bay for the fourth time in seven years.
While Gobler, a marine science professor at the School of Marine and Atmospheric Sciences at Stony Brook University, watches carefully for the appearance of red tides from these algae locally, he recently completed a much broader study on the spread of these toxins.
Gobler led a team that explored the effect of ocean warming on two types of algae, Alexandrium and Dinophysis. Since 1982, as the oceans have heated up, these algae have become increasingly common, particularly in the northern Atlantic and Pacific oceans, according to a study Gobler and his colleagues recently published in the Proceedings of the National Academy of Sciences. When they become concentrated in shellfish, these algae can lead to diarrhea, paralysis and even death if people consume enough of them.
Over the course of the study, algae have begun to form “denser populations that are making shellfish toxic,” Gobler said. Temperature is one of many factors that can affect the survival, growth and range of organisms like the algae that can accumulate toxins and create human illness. “As temperatures get higher, they are becoming closer to the ideal for some species and out of the ideal for other species,” Gobler said.
The strongest effect of changing temperatures are at higher latitudes, which were, up until recently, prohibitively cold for these types of algae. The biggest changes over the course of the study came in the Bay of Fundy in Canada, in Scotland, Ireland, Scandinavia, Iceland, Greenland and Alaska. The toxic algal blooms increased in frequency between 40 and 60 degrees north latitude, according to the study. These are places where toxic algae lived but weren’t as prevalent, but the warming trend has created a more hospitable environment, Gobler said.
Raphael Kudela, a professor of ocean sciences at the University of California, Santa Cruz who wasn’t involved in this research, explained that other papers have suggested a similar link between temperature and the movement of these algae. “We’ve seen the expansion of ciguatera fish poisoning, as the temperature range has moved poleward for those algae,” Kudela wrote in an email. NOAA biological oceanographer Stephanie Moore has documented an expanded window of opportunity for paralytic shellfish poisoning linked to changes in temperature, Kudela said. “While we can point to specific events, and it makes intuitive sense, the Gobler paper actually documented these trends using a long time series, which hasn’t been done before,” Kudela continued.
R. Wayne Litaker, a supervisory ecologist at NOAA’s National Ocean Service, collaborated with Gobler on the project. He said small differences in temperature are significant for the growth rate of these toxic algae. Extending this to other organisms, Litaker explained that fish are also extending their ranges amid a rise in global temperatures. “There’s been a general movement of temperate species toward the poles,” Litaker said. He’s seen tropical fish, such as butterfly fish, off the docks of North Carolina that he hadn’t seen that far north before.
Gobler and his colleagues estimate that the need to close shellfish beds, the increase in fish kills, and the health care damage to people has exceeded a billion dollars since 1982. The largest problem for people in areas like Alaska is their lack of experience with red tides.
“Communities are being exposed to these blooms where they had not been in the past,” Gobler said. “[The blooms] can be most dangerous when they take a community by surprise.” Gobler said this happened in Alaska during the study. In the last decade, shellfish toxins that are 1,000 times more potent than cyanide caused illnesses and were suspected in two deaths in Haines, Alaska.
Litaker said he gave a talk several years ago at a conference. Gobler approached him and asked if they could work together. “One of the wonderful things about these meetings is that you see things that trigger possibilities and whole new projects are born,” Litaker said.
Litaker described Gobler as a “major player in the field” who has done “fantastic work over the years.” Litaker said he was “quite impressed with what he’s done.” Litaker explained that the climate is changing and urged fisheries and shellfish experts to prepare to respond throughout the country. “As we get warmer and more run off of nutrients, toxic cyanobacteria [algal blooms] are causing problems in all 50 states,” Litaker said.
Kudela suggested that the “new records every year for the last several years … will undoubtedly continue to impact the range, duration and toxicity of blooms.”
Locally, Gobler continues to monitor dozens of sites on Long Island, where he suggested that Alexandrium could become less prevalent with warming, while Dinophysis could become more common. Temperature and other factors favorable for algae growth have led to red tides in the past.
In oceans across the world, Kudela said the next logical step would be to explore the interaction of temperature and nutrients. “We know both are changing, and they are likely to have additive or synergistic effects, but we haven’t done the same careful study as the Gobler paper looking at how the trends are interacting,” he explained.