Climate change could increase our exposure to water-borne disease from ocean, coastal and lake ecosystems, scientists told a conference in Washington today.
Researchers from the US National Oceanic and Atmospheric Administration (NOAA) said their studies had shown how climate change makes ocean and freshwater environments more susceptible to toxic algal blooms and the proliferation of harmful microbes and bacteria.
Delegates at the American Association for the Advancement of Science (AAAS) heard how studies predict longer seasons of harmful algal bloom in Washington State’s Puget Sound.
The study looked at blooms of Alexandrium catenella, or “red tide,” which produces saxitoxin, a poison that can accumulate in shellfish. If consumed by humans, it can cause gastrointestinal and neurological symptoms including vomiting and muscle paralysis or even death.
"Changes in the harmful algal bloom season appear to be imminent and we expect a significant increase in Puget Sound and similar at-risk environments within 30 years, possibly by the next decade,” said the NOAA’s Stephanie Moore.
"Our projections indicate that by the end of the 21st century, blooms may begin up to two months earlier in the year and persist for one month later compared to the present-day time period of July to October."
The same model can be applied to other coastal areas around the world increasingly affected by harmful algal blooms, the NOAA said.
Another NOAA study conducted at the University of Georgia looked at how global desertification — and the resulting increase in atmospheric dust — could fuel the presence of harmful bacteria in the ocean and seafood.
Desert dust and its associated iron, when deposited into seawater, significantly stimulates the growth of Vibrios, ocean bacteria that can cause gastroenteritis and infectious diseases in humans, the research suggests
“Within 24 hours of mixing weathered desert dust from Morocco with seawater samples, we saw a 10-1,000-fold growth in Vibrios, including one strain that could cause eye, ear, and open wound infections, and another strain that could cause cholera ,” said Erin Lipp.
“Our next round of experiments will examine the response of the strains associated with seafood-related infections.”
Since 1996, Vibrio cases in the United States have jumped 85 percent according to reports that primarily track seafood-related illnesses. It is possible this additional input of iron, along with rising sea-surface temperatures, will affect these bacterial populations and may help to explain both current and future increases in human illnesses from exposure to contaminated seafood and seawater.
To add to the doom and gloom, the increasing likelihood of rainstorms - brought on by climate change - could up the risk of dated sewage systems overflowing, causing the release of disease-causing bacteria, viruses and protozoa into drinking water and onto beaches.
Sandra McLellan at the University of Wisconsin-Milwaukee School of Freshwater Sciences, found spring rains are expected to increase in the next 50 years, and areas with dated sewer systems are more likely to overflow because the ground is frozen and rainwater can’t be absorbed. As little as 1.7 inches of rain in 24 hours can cause an overflow in spring and the combination of increased temperatures — changing snowfall to rainfall and increased precipitation — can act synergistically to magnify the impact.
McLellan and colleagues predict that, in the worst case scenario, there could be an average 20 per cent increase in the volume of overflows, and they expect overflows to last longer.
“Hundreds of millions of dollars are spent on urban infrastructure, and these investments need to be directed to problems that have the largest impact on our water quality,” said McLellan. “Our research can shed light on this dilemma for cities with ageing sewer systems throughout the Great Lakes and even around the world."
“Understanding climate change on a local level and what it means to county beach managers or water quality safety officers has been a struggle,” said Juli Trtanj, director of NOAA’s Oceans and Human Health Initiative and co-author of the inter-agency report A Human Health Perspective on Climate Change.
"These new studies and models enable managers to better cope and prepare for real and anticipated changes in their cities, and keep their citizens, seafood and economy safe."