A professor in Stony Brook’s School of Marine and Atmospheric Sciences and the Endowed Chair of Coastal Ecology and Conservation, Dr. Christopher Gobler, presented his research on how harmful algal blooms threaten coastal ecosystems to students and faculty on Wednesday, Oct. 3.

Harmful algal blooms (HABs), Gobler explained, occur when algae grows so dense that it starts to produce toxins that negatively impact humans and marine ecosystems.

One of the most common types of HABs is known as red tide. Despite its nickname, red tide comes in a variety of colors, and though some have a minimal impact on an ecosystem, others can cause irreparable damage. Responsible for killing sea life, these are known as ecosystem disruptors.

Over the years, the threat caused by HABs has accelerated.

“If you go back to 1970, there were a few isolated incidents and now this is truly a global phenomenon,” Gobler said.

Some of the factors that Gobler attributes to the expansion of HABs are anthropogenic nutrient loading — the process of nutrients entering an ecosystem due to human activity — and climate change.

One type of anthropogenic nutrient loading for HABs begins with microcystis, a type of freshwater photosynthetic bacteria. Microcystin, a form of microcystis, is highly toxic. Gobler shared an example from the city of Toledo, Ohio to demonstrate how dangerous the bacteria can be.

“Usually the western part of Lake Eerie has the highest population density around it,” Gobler said. “It’s the shallowest, and therefore is the most sensitive to anthropogenic nutrients. It was just a few summers ago where [Toledo] had their drinking water shut down for an extended period because of microcystin getting into the public water supply.”

Microcystin flourishes in ecosystems where there are high levels of nitrogen and phosphorus present in the water. Microcystin is a particularly “nitrogen-rich compound,” Gobler said.

While in most cases, microcystin flourishes when there is a large amount of phosphorus, Lake Erie is unusual in that microcystin thrives there despite low phosphorus levels.

“We saw that actually with more phosphorus, microcystis became less abundant within the communities. It’s consistent with the idea that it actually likes this low phosphorus environment,” Gobler said.

However, according to the Environmental Protection Agency’s website, HABs typically prefer high levels of phosphorus, unlike what was seen in the Lake Erie case study.

“Too much nitrogen and phosphorus in the water causes algae to grow faster than ecosystems can handle,” the EPA wrote in an article about nutrient pollution. “Large growths of algae are called algal blooms and they can severely reduce or eliminate oxygen in the water, leading to illnesses in fish and the death of large numbers of fish.”

Gobler also spoke about the role that temperature changes play in contributing to HAB growth.

Increasing temperatures lead to longer bloom seasons and can cause blooms to become more widespread. As temperature is projected to increase over the next century, this is not a good sign for ecosystems, Gobler explained.

“The blooms are more intense now than they have been in the past,” he said. “You see an increased season length and an increased growth rate.”

Mentioned earlier were red tides, but another dangerous ecosystem disruptor Gobler identified is the brown tide, a HAB that has been found in the Great South Bay and waters in Rhode Island, New Jersey and South Africa.

“Brown tides have been incredibly damaging to Long Island ecosystems. The scallop fishery on Eastern Long Island…declined dramatically following the first brown tide and really has never recovered,” he said.

In addition to scallop fisheries, brown tides have also impacted seagrass.

“With this brown water, it’s difficult to get any light penetration to the bottom. And that’s where seagrasses live and if they’re not getting any light, they’re going to lose their habitat. There was a mass loss of seagrass with these brown tides, as well,” Gobler said.

Gobler pointed out the relevancy of HABs right now as red tides continue to become more common in Florida, in the Gulf of Mexico and even right here on Long Island.

Gobler presented a map, which detailed areas with different types of algal bloom that have sprung up across Long Island in the past four to five months.

Stony Brook graduate students are concerned about the growing HAB problem.

Michael Schrimpf, a Ph.D. candidate in the department of ecology and evolution, says algal bloom is “one of the many problems we deal with in coastal oceans.”

“Certainly human health is a very important issue for a lot of people. As a wild biologist, I’m also interested in effects on other wildlife,” he said. “Anything that alters ecosystems is something we need to keep our eyes on in a changing world.”

Emily Herstoff, another Ph.D. candidate in the department of ecology and evolution, agreed that HABs are worrisome.

“Economically, it’s very damaging. There are a lot of risks to human health and wildlife health,” she said. “There’s societal issues and it has a negative impact on ecosystems.”