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Algae Outbreaks: Fed by Drought, Climate Change, Pollution

The recent outbreak of aquatic algae blooms across California’s waters is part of a global problem. But drought and higher temperatures have fueled the blooms, says environmental scientist Peggy Lehman.

Written by Matt Weiser Published on Read time Approx. 7 minutes
An algae bloom at Pinto Lake near Watsonville, Calif.State Water Resources Control Board

From the Klamath River in the north to Lake Elsinore in the south, aquatic algae blooms seem to be hitting every part of California this year.

A kind of algae known as Micrycystis aeruginosa is the culprit in most cases. This algae, which is also a kind of cyanobacteria, creates a repulsive bright-green muck on the surface of the water. It contains a toxin that can kill dogs and other animals if they ingest enough of the algae while swimming or drinking. In humans, exposure to the algae can cause rashes, skin and eye irritation and gastrointestinal problems. The toxin can also cause cancer.

The problem can be particularly acute in the Sacramento-San Joaquin Delta, the source for the State Water Project, which serves 25 million Californians. As a result, understanding and containing these algae blooms is important to public health.

In one recent outbreak at Pyramid Lake near Los Angeles, a number of people reported feeling sick after contact with algae-infested waters. Lake Elsinore was closed for a week from July 28, and swimming is still not permitted in its waters.

Unfortunately, not much is known about the cause of these blooms, and even less is known about how to contain them safely. To help us understand the problem, Water Deeply recently spoke with Peggy Lehman, a staff environmental scientist at the California Department of Water Resources, who has a Ph.D. in ecology and has been studying algae blooms in the Delta for more than 15 years.

Water Deeply: What interests you about these bacteria?

Peggy Lehman: These organisms have been developing and creating water problems worldwide. In the Delta, it’s important to us because we have a large population base that uses this water, and protecting the water quality is of huge ecological importance. With the State Water Project drawing from the Delta, we have to take a look at the importance of anything like this because it could be quite detrimental to human health and water quality.

Water Deeply: Have outbreaks like this always occurred in the Delta?

Lehman: We started seeing blooms of Microcystis in 1999, and they’ve occurred almost every year since then. Microcystis itself has been recorded in the Delta all the way back to 1913. But no one I’ve talked to – people who know the Delta back to 1968 – has ever seen anything like these blooms occur before 1999.

Water Deeply: What started all this in 1999?

Lehman: We don’t know. I’ve talked to quite a few scientists in California, as well as other people around the world, and no one knows. A number of places have seen increases in cyanobacteria around the same time. It seems to be a larger-scale phenomenon.

Water Deeply: Is there a climate change connection?

Lehman: Microcystis does much better at warmer temperatures. So the increase in water temperature that has occurred over the past years does promote the growth of Microcystis. It does promote the other cyanobacteria as well.

Water Deeply: Do we have other problem cyanobacteria in California besides Microcystis?

Lehman: Yes. We have a number in the Delta. We have seen growth of quite a bit of Anabaena and Aphanizomenon. Both are toxic cyanobacteria. There’s a growing concern that these other bacteria – some of them are more toxic – will take a greater hold in future and become a bigger problem than Microcystis.

Water Deeply: What is it that’s more toxic about Anabaena and Aphanizomenon?

Lehman: Anabaena, for instance, contains anatoxin-a, a neurotoxin, which is rapidly toxic to aquatic organisms. Microcystis doesn’t have a neurotoxin. Instead, it has a hypatotoxin – a cancer-causing toxin.

Water Deeply: Do these other cyanobacteria have the same triggers that cause them to bloom?

Lehman: They have some of the same triggers. Most cyanobacteria seem to like warmer temperatures. As it turns out, Anabaena and Aphanizomenon like it slightly cooler. But we do see them together with Microcystis in the water column.

Water Deeply: Are these really algae, or are they bacteria?

Lehman: People normally refer to these organisms as blue-green algae or cyanobacteria. They are called blue-green because of the pigments in them, and they are called algae because they photosynthesize. But they are called bacteria because their inner cellular structure isn’t developed: They don’t have internal membranes.

Dogs are vulnerable to illness and death if they swim in waters infested with blue-green algae. People shouldn't swim in infested waters either, especially children. (Santa Clara County Parks)

Dogs are vulnerable to illness and death if they swim in waters infested with blue-green algae. People shouldn’t swim in infested waters either, especially children. (Santa Clara County Parks)

Water Deeply: Why are dogs more likely to become ill from exposure to Microcystis?

Lehman: Dogs are not more likely to become ill. Animals, including dogs, often drink right at the edge of the river or water body, and that’s where there’s a lot of algal scum. So they are likely to not only imbibe the water with the toxins in it, but they also get the toxin on their fur; when they lick that off they get a very high concentration of toxin in their body in a short period of time. Any animal is similarly vulnerable.

Water Deeply: Humans too?

Lehman: Absolutely. People who swim in Microcystis-infested water commonly refer to having responses that are flu-like symptoms: nausea, diarrhea, that sort of thing. Some people swimming in the water get rashes. We have a lot of staff here who work in the water regularly, and they can get rashes on their arms.

People rarely report acute problems. But again, Microcystis toxins are cancer-causing. They affect the liver, so you wouldn’t necessarily see an impact right away. We have done studies on fish in the lab and we find that upon exposure to Microcystis, the fish liver becomes affected with signs of cancer.

Water Deeply: Are people at risk of cancer from exposure to Microcystis?

Lehman: Yes, but there haven’t been any studies in this country which demonstrated that Microcystis caused cancer in humans. The risk to each person is different, because they have a different sensitivity. The most important issue affecting response is size. A smaller person is going to have a greater potential response than a larger one. So children are more sensitive than adults, which is why the EPA sets much more stringent criteria for drinking water for children than adults.

Water Deeply: What advice do you have for people who encounter Microcystis or other obvious algae outbreaks?

Lehman: The most important thing for them to do is to stay out of it. If they’re boating through it, that’s usually no problem. But make sure they stay out of the water, and certainly don’t accidentally or purposely drink it.

It is important to make sure children stay out of it. They have a much smaller mass and, therefore, the risk to them is much greater. Children are also much less careful about drinking water when they swim.

If they really want to know more about a specific bloom, they can contact the SWAMP Program (Surface Water Ambient Monitoring Program) at the State Water Resources Control Board. They have more of a handle on exactly which species are present in different water bodies throughout the state, and hopefully over time, there will be websites that have daily information, so people will know their risk. Right now, we’re developing a website at DWR (Department of Water Resources), where we can inform people about outbreaks in the waters we manage. We’re all working on new ways to provide real-time information about these bacteria to the public.

The public can also call their local health agency or take a water sample and send it to SWAMP. The program has a small amount of funding for sample analysis.

Water Deeply: Is it dangerous to eat fish that have been caught where Microcystis is blooming?

Lehman: In some countries they find that Microcystis toxins accumulate in shellfish. So they pose a great risk. The general statement here for fish is that in areas where you have low concentrations of Microcystis, it might be all right to eat the fish, as long as you only eat the flesh. But if there are high concentrations of Microcystis, the advice is to not eat the fish.

Water Deeply: What have you learned about the cause of algae blooms in the Delta?

Lehman: Most of the Microcystis seems to be in the San Joaquin River. It spreads out from there to the rest of the Delta.

It is also true that as you have more ammonium in the water column, Microcystis increases. It thrives on ammonia as a nutrient source and outcompetes other plankton for the use of ammonium. Warm water temperature and ammonium combined enhance Microcystis blooms.

Low flows, warm conditions, and high nutrients increase Microcystis blooms in the San Joaquin River. A lot of nutrients, though, in the San Joaquin River do come from the Sacramento River, and the two are important in the overall mix of what’s out there.

Water Deeply: What are the primary sources of ammonia in the Delta?

Lehman: Some of the sources are wastewater treatment plants, bottom sediment and nutrient recycling in the water column. We are currently working to sort out these sources and their contribution to the bloom.

Water Deeply: What is that you still don’t know about these bacteria?

Lehman: How to get rid of them. The delta is very large and some of the systems that have been developed for small water bodies won’t work. We also have a lot of environmental issues we have to address whenever we try to implement management actions.

We can’t just go and put a Microcystis-eating fish out there. Of course, spraying anything in the Delta is always associated with some risk that you might hurt other organisms that are important to the food web. So we have to be very careful.

How do you manage Microcystis blooms in a sensitive system like ours? It’s a large challenge. However, we are not alone in this challenge. Microcystis blooms are a worldwide problem.

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