What is that Green Stuff in the Water?

With lakes, ponds, and rivers on Cape Cod being threatened by toxic algal blooms, which can disrupt ecosystems and endanger people and pets if consumed or touched, Assistant Professor of Chemistry Daniel Rogers, a Cape resident and a chemical oceanographer, who studies nutrient cycling in coastal waters, explains why this is occurring.

“Toxic algal blooms are a national challenge, affecting coastal ponds, lakes and other coastal waters around the country,” says Rogers. “In 2019, for instance, Lake Erie had a 300-700 square mile bloom.”

Rogers adds that with increasing populations and changing environmental conditions, we see the lowering of water quality and an increase in nutrients and a decrease in available oxygen, which is called eutrophication. These added nutrients act like adding fertilizer to your garden, stimulating the growth of plants (cyanobacteria and algae).

“As your garden attracts rabbits that eat your vegetables, the algal blooms are followed by more grazing organisms, consuming the plants but also the oxygen in the water,” says Rogers. “That loss of oxygen— called hypoxia and anoxia—drives a cascade of environmental effects such as diminishing water quality, fish migration or fish kills.”

Powerful Toxins

Eutrophication can lead to algal blooms, some of which produce toxins. Harmful algal blooms (HABs), like red tides, are the blooming of specific phototrophic species that produce a toxin—in some cases, more powerful than cyanide.

For example, Rogers says, shellfish may eat the HAB organisms, concentrating the toxin in the shellfish tissue. Humans may then consume the shellfish and react to the elevated toxin levels—called paralytic shellfish poisoning, which can be fatal.

Climate Change Impact

With global warming, the biology goes faster, some organisms can double every 30 minutes under ideal conditions.

“Cells breathe more rapidly, consuming more oxygen, and oxygen is also less available as water temperature increases,” explains Rogers, who works within the Environmental Sciences and Studies Program. “As plants in your garden respond differently to summer heat—weeds bloom and flowers wilt—the increase in water temperatures may favor a different set of organisms, maybe the organisms producing HABs.”

According to Rogers, increasing nutrient levels—like climate change—may alter the composition of the bloom and is a result of human activity.

“As population densities increase, the nitrogen we introduce into the environment enters the water systems. About half the world’s population lives within 60 miles of the coasts, and all of our activities impact the coastal ecosystem,” Rogers says.

Student Opportunity

The Chemistry Department has received funding from trustee Elizabeth Hayden ’76 for a project next summer called the Cape Cod Environmental Restoration Internship.

With the nonprofit Friends of Bass River, in Yarmouth, two student interns will collect samples, process data from the Bass River and conduct the scientific testing to ascertain if the health of the ecosystem is improving through the nonprofit’s restoration efforts.

“This opportunity will provide the interns with hands-on training as they examine the science behind the Bass River ecosystem and conduct valuable research,” says Rogers. “It will also introduce them to the public engagement and outreach aspects of environmental restoration.”