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Algae Bloom and Climate Change

Posted in Water on September 25, 2018

Any serious beachgoer has seen it before. They’ve seen the light. On certain warm summer nights, you might have the chance to see it too. Waves breaking in the twilight with a froth that shines green, like a glowstick near the end of its lifespan. Stick around and watch, and they’ll grow brighter as the sun fades, their foam brilliant with what looks like captured moonlight. It’s an algae bloom.

It isn’t the moon or the sun that causes that light. It’s brought on by algae. As the world heats up, they’re growing in number, and they’re starting to show up in greater and greater concentrations in places where they previously were sparse or controlled. What does this mean for us and our shores?

Growing Concerns (No Pun Intended)

One rising concern reported recently by NPR is the incidence of algae in drinking water reservoirs. Salem, Oregon draws its water from a nearby reservoir called Detroit Lake; an algal bloom there mucked up the water so much that the tiny cells, and the toxins they produce, overwhelmed Salem’s sand filtration and were visible in the city’s water supply. The city notified residents of a civil emergency and ended up dumping millions of dollars of charcoal into the contaminated water to soak up the algae and toxins.

It’s not just Salem that’s facing down algae coming out the tap. According to the New York Times, a similar event saw Toledo temporarily shut down their water supply in 2014; according to the Cleveland Plain Dealer, the city’s water was so contaminated that citizens subsisted on bottled water for three days while municipals officials worked to disinfect it. Subsequent to that event, Toledo has taken a page from Salem’s book and begun to regularly test their drinking water for levels of algae and toxins – a practice that one expert quoted by NPR thinks will become more and more widespread as warming temperatures bring algae on to the radar of more municipalities.

This Year Alone

This summer saw algal blooms shut down tourism and fishing on Lake Superior and parts of Lake Erie. And ocean-borne blooms from Florida to China to the west coast of the Americas have been increasing in length, intensity, and size, fouling up beaches and waterways.

Are these events ramping up because of climate change? Like anything to do with weather on a global scale, that’s a difficult question to answer. Many inputs and confounding variables that muddy the waters and make causality difficult to prove. Still, there are a number of factors associated with climate change that would seem to create a more agreeable environment for algae to thrive.

Warmer weather causes evaporation, which means wetter weather, which in turn increases agricultural runoff into streams and bodies of water. That’s a boon for many types of algae, for whom the phosphorus in fertilizer is an important nutrient. One hallmark of our CO2-saturated atmosphere are summers that grow ever longer and warmer; that’s also good news for algae, who thrive in warm water and typically reach their peak populations during the heat of summer. As sea levels creep upwards, much of the low-lying terrain that’s found along our world’s coasts will be submerged. Where once was a beach, you’ll find a shallow, brackish lagoon. The water is quite warm and the perfect environment for algae and other pathogenic nasties to thrive.

Are We Seeing This More?

That means that those nights with glowing waves breaking on the beach might not be such a rare event. What you see in such events in a natural phenomenon called bioluminescence. Fireflies and deep-sea fish use this trick to generate light through a chemical reaction in the body. During the summer, temperatures in the northern hemisphere climb, and algae that live in oceans and lakes begin to multiply. There’re all different sorts of algae; kelp and seaweed are among the biggest. Cyanobacteria, another type, are commonly in the news for their toxin-emitting properties. Waves that glow with bioluminescence are a sign of a “red tide,” a massive spike in the population of a microscopically small type of algae called dinoflagellates.

A recent study examined this phenomenon:

“Climate change pressures will influence marine planktonic systems globally, and it is conceivable that harmful algal blooms may increase in frequency and severity. These pressures will be manifest as alterations in temperature, stratification, light, ocean acidification, precipitation-induced nutrient inputs, and grazing, but absence of fundamental knowledge of the mechanisms driving harmful algal blooms frustrates most hope of forecasting their future prevalence.”

The glowing waves of a red tide are more than a pretty show. For many millennia, the coastal peoples of California and elsewhere have known them to be a portent, a kind of message from the natural world to avoid shellfish for the time being. Algae saturate their environment with different sorts of toxins during a bloom. The toxins are potent enough to harm people. This means, in low doses, they cause symptoms like food poisoning. Some types produced by cyanobacteria can cause liver damage. In high enough doses, they can kill.


Plankton filter toxins and algae from the seawater. From there, the toxins work their way up the food chain. Shellfish suck up the plankton or snapped up by one predator or another. The marine life we eat (like oysters and other shellfish) becomes so concentrated by toxins that they’re rendered unsafe for human consumption. During these events, government agencies restrict aquaculture, fisheries, and shellfish foraging. The government monitors the levels of algae and toxins in the water and in seafood. They also monitor recalls of products or temporary shutdowns of businesses are increasingly common.

So are cases of poisoning from algal blooms. Almost every year, there’s stories of cruises or seafood dinners that go horribly wrong from shellfish poisoning. One sort of toxin, called domoic acid, is particularly frightening. In mild cases, the toxin causes confusion and disorientation. But the toxin can, at higher doses, cause persistent short-term memory damage. Remember Alfred Hitchcock’s seminal horror thriller The Birds? The inspiration? Domoic acid poisoning drove massive flocks of seabirds to apparent madness.

By: Sean McNulty, Contributing Writer (Non-Lawyer)