Algal Blooms in Freshwater and Marine Systems

What do dogs in Ohio and sea otters in California have in common? Death by liver failure as a result of algal blooms.

Sick People and Dead Dogs in Ohio

In Ohio this year (and in many previous years), a cyanobacteria bloom at Grand Lake St. Marys is killing animals that come in contact with the water. More than fifteen people have reported stomachaches, dizziness, and numbness after touching the water in the lake. Several dogs have died.

Grand Lake St. Marys has been closed for swimming, fishing, and boating. Fish kills are a regular sight. Tourism around the lake – normally a $160 million business – is nonexistent. Local residents say they have seen dogs die shortly after taking a drink from the lake.

Dan Jenkins’ dog, a black lab, died after a quick dip in the Grand Lake St. Marys. Jenkins said his dog ran into the water and back out and was covered in bright green slime. Jenkins wiped the slime off his dog and took him home to bathe him.

The dog later died and Jenkins spent four days in the hospital after he had difficulty seeing and walking and his legs and arms went numb. Weeks later, he still had problems with memory loss and fatigue.Β  Doctors say it’s because of the toxins from the algal bloom.

What Is an Algal Bloom?

An algal bloom occurs whenever an excess of nutrients enters a water system and the algae reproduce quickly. Algal blooms can be many colors – blue green algae (cyanobacteria) produce bright green blooms, mostly in freshwater systems; golden algae produce bright yellow blooms, again mostly in freshwater systems; red algae produce β€œred tides”, which are not associated with tides and occur mainly in marine systems. There is still some debate over exactly what causes red tides, but we know cyanobacteria blossom wherever there is significant agricultural runoff.

Harmful Algal Blooms

When an algae produces toxins, the bloom is known as a harmful algal bloom (HAB). State parks, wildlife, or fisheries departments are often the ones charged with monitoring HABs and making decisions about when to close lakes and other waterways. Even if an algal bloom does not qualify as an HAB, it can still kill fish and other aquatic organisms by using up all the oxygen in the water.

Cyanobacteria can produce several toxins. Some toxins include cylindrospermopsin, microcystin, saxitoxin. Some cyanobacteria produce more than one toxin. One species of cyanobacteria found in Grand Lake St. Marys in western Ohio this year produces seven different toxins.

The different toxins have different effects on people and animals. Effects range from rash and itching, to vomiting and dizziness, to liver and nerve damage. Animals have died and people have become severely ill just from coming in contact with the water containing cyanobacteria toxins.

Not all cyanobacteria are toxic to us or other large animals. Cyanobacteria are used in fertilizers, food, feed, and dyes. Spirulina is a cyanobacteria.

Sure HABs Happen in Lakes, But What About Rivers?

Grand Lake St. Marys is the headwaters for two rivers: the St. Marys River, which feeds into the Great Lakes and on into the Atlantic Ocean, and the Wabash River, which eventually reaches the Mississippi River. The Great Lakes have their own algal blooms that can cause scarring on any skin that touches the water. The Mississippi River is already quite polluted, ending in a dead zone in the Gulf of Mexico.

Laura Walker, watershed coordinator for the Grand Lake-Wabash Watershed Alliance, isn’t worried that the algae in Grand Lake St. Marys will get to the Great Lakes or the Gulf of Mexico. She says the algae needs still water and the rivers will keep it from blooming.

Plans to Combat the HAB

With sixteen bodies of water in Ohio closed for toxic algal blooms, something needs to be done. Not to worry, the state of Ohio has plans. They’re going to put a chemical in the lakes to see if the chemical can slow the growth of the cyanobacteria. Starting in March 2012, putting manure on fields in the winter will be banned.

But the biggest and best solution they’ve come up with is…wait for it…ship the manure from Ohio CAFOs to Indiana.

What About the Sea Otters?

So, if the waters from Ohio are draining into the Atlantic, what does that have to do with sea otters in the Pacific?

Well, since 1999, twenty-one dead sea otters were pulled from the ocean in the Monterey Bay area. Their corpses were yellow and bloated, indicating liver failure. Autopsies revealed that they had died of microcystin poisoning. The number of sea otters dying of microcystin-induced liver failure increased from one sea otter in 1999 to eleven sea otters in 2007, the most recent year of the study.

Scientists traced the source of the microcystin to shellfish and crustaceans – a prime food source for the sea otters. The dead sea otters were found near river mouths, estuaries, and sheltered bays, places where microcystin flows from rivers could collect.

Cyanobacteria Toxins Travel From Lakes Through Rivers and into the Ocean

The microcystin had traveled from Pinto Lake, down the Pajaro River, and into the Monterey Bay. Further testing indicated that other rivers in the area also carried the algae and its toxins into the bay where the toxins were taken up by filter feeders, such as oysters and mussels.

Additionally, microcystin was found in several locations up and down the California coast.

So, algal blooms don’t stay in inland lakes like they’re supposed to. Rivers are no barrier to the toxins.Β  And the toxins accumulate in seafood enjoyed by both sea otters and humans.


Miller MA, Kudela RM, Mekebri A, Crane D, Oates SC, et al. 2010 Evidence for a Novel Marine Harmful Algal Bloom: Cyanotoxin (Microcystin) Transfer from Land to Sea Otters. PLoS ONE 5(9): e12576. doi:10.1371/journal.pone.0012576 – Free and online.

Death of a Lake.Β  The Journal Gazette, 29 Aug 2010.

Illnesses of at least 9 people, dog deaths may be linked to toxic algae in Ohio lake.Β  Washington Examiner, 30 Jul 2010.

Monterey Sea Otters Killed by Algae.Β  San Francisco Chronicle, 11 Sep 2010.

Sea Otter at the top of the post by *~Dawn~*, used with a Creative Commons license.

Black Lab by pmarkham, used with a Creative Commons license.

Great Lakes by NASA Goddard Photo and Video, used with a Creative Commons license.

Second sea otter photo by VicBurolla, used with a Creative Commons license.

Written by Heather Carr


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    • I googled and it looks like you’re referring to Nualgi. Has it been tested in the U.S.?

      Also, I can’t find any scientific papers on it. It would be great if you would point me to them. It looks like it has a lot of potential.

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