You’ve probably heard of algae in the context of toxic blooms in local waterways – stinky slimes that close beaches, suffocate fish, sicken swimmers, and even kill pets. “Beware the Toxic Algae that Can Kill Your Dog”, “Toxic Algae Kills Dogs Across the Country”, “Two Tennessee Dogs Die Suddenly After Swim, Water Being Tested for Toxic Algae”… These are just a few of the headlines pulled from the thousands of news stories published across the country that are raising concerns for dog owners everywhere. News of dogs dying after swimming in or drinking algae-fouled water has left many pet owners afraid to go to the beach. But are these fears founded? Let’s look at the facts.

What is toxic algae?

First, it’s important to know that not all varieties of algae are toxic. There are many kinds of algae all around the world, and most are harmless. Algae (also known as phytoplankton) is technically a type of plant, and it commonly forms the base of aquatic and marine food chains. Like other plants, it produces oxygen through photosynthesis. In general, the presence of algae in a waterway is a good thing.

But some types of algae have given the others a bad name. Or, rather, an algae imposter has been framing its lookalikes for its delinquent deeds. Blue-green algae, more correctly known as cyanobacteria, is not really algae at all, and also it isn’t blue-green – it can be found in many shades and colors. While cyanobacteria photosynthesize like algae, in addition to producing oxygen, they also produce toxins that can make you sick. These bacteria are the bad guys you need to watch out for.

What do cyanobacteria toxins do?

Cyanobacteria toxins can cause health effects in humans and animals that ingest them (by drinking the water they’re in) or that even just touch them. These effects can range from skin irritation to nausea. In severe cases, cyanobacteria toxins can cause death.

Effects on humans tend to stay towards the mild end of the scale; it’s rare for a person to die from swimming in water contaminated with cyanobacteria toxins. Domestic animals, including livestock and pets, are more at risk from these severe effects. And wildlife are in danger too: toxic algae blooms are not really natural, so even animals that live in the water – like fish, turtles, and frogs – can get sick or die from the toxins. These effects on wildlife can ripple through an entire ecosystem, harming plants and animals that aren’t hurt directly by the cyanobacteria.

What causes algae blooms?

It’s normal for both cyanobacteria and non-toxic kinds of algae to be present in waterways (and even in some places on land!), but problems arise when the algae “blooms”, or reproduces exponentially. This happens when waterways have high levels of nutrients like nitrogen and phosphorus, allowing the algae to thrive, just like plants that have been given fertilizer. When nutrient levels increase in warm, shallow, slow-moving water, that creates perfect conditions for algae to bloom.

Sometimes these blooms are made up of cyanobacteria, the toxic fake algae. But even when the blooms consist of real algae that doesn’t produce toxins, they can still harm some animals. How does this happen? First, the algae on the top of these floating mats block sunlight from reaching their cousins lower down. Unable to photosynthesize, these less fortunate algae quickly die. The bacteria that show up to feast on the dead algae use a lot of oxygen in their feeding frenzy, leaving less oxygen for fish and other water-breathers. It’s easy to see that these animals, and other species that depend on them, will soon suffer the same fate as the lower-level algae.

The most famous algae bloom is the “dead zone” in the Gulf of Mexico. The nutrients that enabled this bloom traveled to the Gulf via the Mississippi River, after escaping from fertilizer spread on Midwestern farmland. The nutrients that cause algae blooms in the Chesapeake Bay, in contrast, are likely fugitives from fertilizer used on residential lawns.

What can we do about it?

The Izaak Walton League is on the job. Through the Save Our Streams program, League volunteers are monitoring water quality around the country, keeping an eye out for high nutrient levels and other problems that can make water unsafe for drinking and swimming.

You can become a volunteer water monitor. Consider “adopting” a small stream that you think might be carrying nutrients towards rivers and lakes, contributing to current or future algae blooms in these larger waterways. Or, test oxygen levels near an algae bloom to collect evidence of the bloom’s effect on wildlife. You can use this data to ask your local decision-makers to change policies, enforce regulations more vigorously, carry out stream restoration projects, and partner with organizations that are working towards better water quality. Learn how.

We shouldn’t have to worry about our health, or the safety of our pets, when we go to enjoy a day at the beach. You have the power to help make your local lakes and ponds safe for swimming again. Don’t put Rover at risk – learn more about water monitoring now.