Every year, from summer into early fall, there are stories in the news across the country and the world regarding blue-green algae poisonings, mostly of dogs and occasionally livestock, often resulting in death.
Species that cause such harmful effects do occur throughout Delmarva. It is important to recognize that, while this is a serious problem, blue-green algae blooms are not a new phenomenon and blue-green algal poisonings long predate the internet, where the vast majority of stories circulate. From 1990-2017, I was an aquatic ecologist with the Delaware Department of Natural Resources and Environmental Control. I monitored and studied water quality in Delaware’s streams, ponds, lakes, rivers and bays, including blue-green algae blooms.
On Delmarva, blue-green algae blooms typically begin to develop in sluggish to stagnant freshwater in June, persisting well into October. Years, and periods within years, that are droughty, with low water flow and stagnation, tend to have more intense blooms than years with above-average rainfall and flushing do. Among Delaware waterbodies known to develop these blooms is Silver Lake in Dover, which has exhibited such a bloom annually for longer than anyone living.
The most reliable visual characteristic is turbid, pea green-colored water that may have a paintlike surface scum of various colors. Concentrations of toxin are generally highest in the scum but have also been found in water without scum. At the time of writing of this article, such a bloom was present on Silver Lake, and a good place to observe it is the area between the old swimming beach and the boat ramp, particularly when the wind is not creating waves along that shoreline that break up and disperse the scum.
The greatest health threat is severe sickness to death in animals drinking out of bloom waters, with the effects developing quickly, within an hour to a day of exposure. People swimming, water skiing or taking part in any activity that results in immersion may swallow a mouthful or two, as well. That’s not good and may be followed by some gastrointestinal upset, but people are not getting the dose that a dog gets lapping up the water and licking it off their fur or the dose that livestock would get drinking out of a pasture pond. In perspective, anyone who swam or water skied in Silver Lake in Dover until these activities were discontinued several years ago swam in blue-green algae blooms, as has anyone who has water skied in Red Mill Pond over the past 40-plus years.
There is information that blue-green blooms can cause dermatitis from skin contact and respiratory problems from breathing aerosols coming off the water. I worked in close contact with these blooms, hands in water collecting samples for many years, and did not experience any such symptoms. Beware that if you don’t feel well when in contact with a bloom or soon thereafter, that feeling may have something to do with the bloom. Consider that exposure of skin, particularly with abrasions and cuts, to soupy, warm water and scums that are concentrated masses of organic matter is not without risk of infection from other associated pathogens.
Fishing in waters with blue-green algae
People may choose to fish in blue-green blooms. Some of the ponds in Delaware that are known for big largemouth bass are also known for their annual blue-green algae bloom. Fish kills may occur during blue-green blooms. The evidence is that fish die not from algal poisoning but from extremely low dissolved oxygen contributed to by the bloom, in combination with some other factors. It is common knowledge that plants utilize sunlight to produce oxygen during the day. It is much less considered that plants, including algae, consume oxygen at night. The combination of massive concentrations of algae consuming oxygen at night, combined with the 24/7 consumption by bacteria, can, in certain uncommon circumstances, drive the oxygen concentration below the level that fish need to survive. Fortunately, this is an infrequent occurrence.
One seldom mentioned characteristic of fish residing in blue-green algae ponds is their edibility. Some sources may say to avoid eating these fish. I don’t know of any information that is definitive that eating fish from a blue-green algae situation is actually harmful, but I do know from my own experience that fish from blue-green waters have a very undesirable taste and that such tainting of the taste of fish received a fair amount of attention in the scientific literature about 30 years ago. I found the taste of the first bite to be bad enough to spit it out and throw the rest away. So if you must fish a blue-green pond/lake, just throw them back. It’s not worth their lives or your work to clean and cook them.
Do not be deceived by the presence of waterfowl swimming in blue-green blooms without apparent ill effect. I have seen domestic mallards and geese swimming in waters that tested very high in toxin. I do not know why this is, but it is. I would not take such an observation as a “green light” to let my dog swim with them.
Study up. Look at some state environmental websites. You’ll likely see some points I’ve touched on here and some I’ve not. They do a good job of presenting useful information in a measured, dispassionate way. Delaware and Maryland both have pages. Look at some of the websites from northern midwestern states (for example, Minnesota, Wisconsin and Nebraska). Their primary recreational areas are freshwater lakes, and they have been dealing with this problem a long time.
Algae blooms can have different looks
Finally, learn to recognize blue-green blooms. Don’t expect or depend on someone to warn you. There is no way that any program could have a sign anywhere and everywhere these blooms might pop up. Keep in mind that blue-green algae blooms have been occurring for much longer than any of us have been alive. Are the blooms more widespread? Are they more toxic than they used to be? These are difficult questions to answer definitively. What is true is that the reporting of them is becoming more frequent and the damage they cause is better understood.
In closing, eliminating blue-green algae blooms from waterbodies larger than an acre or so is extremely costly and uncertain, and requires continued maintenance to sustain success, if success is achieved. Based on substantial scientific monitoring and research, it has been widely accepted that a main driver of blue-green algae blooms is excessive quantity of plant nutrients, mainly phosphorus, reaching susceptible waterbodies from human-related land use and direct effluent discharges. The problem isn’t likely to go away any time in the foreseeable future in waters that already have blue-green blooms. The most effective defense against being harmed by these blooms is awareness of the potential toxicity issue, recognition of the blooms and not ingesting the water.
Meantime, there is one fundamental thing that individuals and society can do to aid the quality of all our waters, streams, lakes/ponds, rivers and estuaries or at least not contribute further to their degradation. That is to make watersheds function more like filters and less like funnels.
Any activity qualifies as filtration that improves the uptake and storage of nutrients in desirable plant and animal forms on land, in wetlands and in the water because it keeps those nutrients from being dissolved free in the water, where they can feed undesirable blooms of blue-greens and other nuisance or harmful algae. Whether an environmental response to a filtration effort is observable or even measurable in a waterbody, it is nonetheless movement in the direction of stewarding a better environment.
Fixing the environment when it’s broken on a large scale and exhibiting whatever kind of problem is an enormous task. Knowing that what you’re doing at any scale, place or time is movement in the right direction is often the best outcome achievable. In that spirit, it seems beneficial for one’s own health to have faith that we will see a day when the cumulative effect of small acts of good environmental stewardship yields observable improvements in large-scale problems, such as blue-green algae blooms.
Dr. Robin Tyler monitored and studied Delaware’s lakes, ponds, streams and coastal waters for more than 27 years as an ecologist with the Department of Natural Resources and Environmental Control. He is retired and lives in the Dover area.
