Unusually warm weather has caused an unprecedented amount of toxic algae to accumulate in the Pacific waters stretching from Alaska to California. The powerful neurotoxin produced by the algae is poisoning sea life along the coast, causing authorities to shut down fisheries to prevent the poisoning from traveling up the food chain and affecting humans.

The toxic tides, or red tides as they are commonly referred to, are a cyclical natural occurrence caused when ocean plant life known as algae simultaneously blooms in such large quantities it discolors the water. According to The Associated Press, this year’s red tide currently measures around 40 miles wide and 650 feet deep, making it one of the largest tides ever recorded.

Red tides are predominantly made of a species of algae known as Pseudo-nitzschia. This type of algae can produce the neurotoxin domoic acid, which can cause food poisoning when consumed by humans and marine life. In most serious cases, the neurotoxin can trigger amnesic shellfish poisoning, a condition that causes permanent short-term memory loss in humans.

Unfortunately, this year’s tide is also one of the longest lasting and poisonous red tides scientists have documented. Although the tide was first detected in early May, as a precaution, fisheries up and down the West Coast have remained shut down for fear of seafood poisoning. In Washington state, tests showed the highest levels of toxins in Dungeness crabmeat ever seen and have forced the closure of more than half of the state’s coast for the remaining crabbing season.

“We think it’s just sitting and lingering out there,” said Anthony Odell, a University of Washington research analyst, who is part of the team surveying the harmful algae bloom, The AP reported. “It’s farther offshore, but it’s still there.”

Although the exact cause of this year’s super red tide has not been confirmed, oceanographers believe a small patch of water slightly warmer than the surrounding Pacific Ocean, nicknamed “the blob,” may be the culprit. These blooms occur on a yearly basis but have become increasingly more frequent and widespread since the 1980s. Many suggest that global warming may be to blame.

“The question on everyone’s mind is whether this is related to global climate change. The simple answer is that it could be, but at this point it’s hard to separate the variations in these cycles,” said Donald Boesch, professor of marine science at the University of Maryland, AP reported. “Maybe the cycles are more extreme in the changing climate.”

This is not the first time that warming ocean temperatures have been linked to human health risks. In the early 1990s, warm waters off the coast of South America were attributed to causing a surge in plankton populations. This burst in plankton numbers was a main contributor to the cholera epidemic of 1991 and 1992 throughout Peru and much of South and Central America. Again, in 2004, warm waters in Alaska allowed bacteria known as Vibrio parahaemolyticus to move much further north than before. This contributed to an outbreak of gastroenteritis in cruise ship passengers who had eaten contaminated oysters, Slate reported.

This past week, President Barack Obama revealed his Clean Power Plan to the nation as a way to address warming ocean temperatures believed to be causing climate change. The plan includes realistic and achievable goals to help cut America’s carbon dioxide emissions and address this serious international problem.

So far, there have been no reports of human illnesses linked to this year’s red tide, but footage of sea lions having seizures and reports of sick pelicans has demonstrated just how serious the situation has become.

“It’s really working its way into the food web and we’re definitely seeing the impacts of that,” said Raphael Kudela, a professor of ocean sciences at University of California, Santa Cruz, the AP reported.