What is in this article?:
• In several studies funded by NOAA’s Oceans and Human Health Initiative, findings shed light on how complex interactions and climate change alterations in sea, land and sky make ocean and freshwater environments more susceptible to toxic algal blooms and proliferation of harmful microbes and bacteria.
University of Georgia work
Researchers at the University of Georgia, a NOAA Oceans and Human Health Initiative Consortium for Graduate Training site, looked at how global desertification — and the resulting increase in atmospheric dust based on some climate change scenarios — could fuel the presence of harmful bacteria in the ocean and seafood.
Desert dust deposition from the atmosphere is considered one of the main contributors of iron in the ocean, has increased over the last 30 years and is expected to rise based on precipitation trends in western Africa. Iron is limited in ocean environments and is essential to most forms of life.
In a study conducted in collaboration with the U.S. Geological Survey, Erin Lipp, and graduate student Jason Westrich demonstrated that the sole addition of desert dust and its associated iron into seawater significantly stimulates growth and persistence of Vibrios, a group of ocean bacteria that occur worldwide and can cause gastroenteritis and infectious diseases in humans.
“Within 24 hours of mixing weathered desert dust from Morocco with seawater samples, we saw a 10-1000-fold growth in Vibrios, including one strain that could cause eye, ear, and open wound infections, and another strain that could cause cholera ,” said Lipp. “Our next round of experiments will examine the response of the strains associated with seafood-related infections.”
Since 1996 Vibriocases have jumped 85 percent in the United States based on reports that primarily track seafood-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.
A changing climate with more rainstorms on the horizon could increase the risk of overflows of dated sewage systems, causing the release of disease-causing bacteria, viruses and protozoa into drinking water and onto beaches. In the past 10 years there have been more severe storms that trigger overflows. While there is some question whether this is due to natural variability or to climate change, these events provide another example as to how vulnerable urban areas are to climate.
Using fine-tuned climate models developed for Wisconsin, 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 showed that under worst case scenarios there could be an average 20 percent increase in volume of overflows, and they expect the overflows to last longer. In Milwaukee, infrastructure investments have reduced sewage overflows to an average of three times per year, but other cities around the Great Lakes still experience overflows up to 40 times per year.
“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 aging 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 interagency 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.”