When Does a Bloom Not Smell Sweet
I live on the beautiful shores of Lake Erie. We’ve long ago cleaned up problems like the burning Cuyahoga River, and we’re learning how to live with challenges like invasive zebra mussels, but now climate change is contributing to the return of a problem we thought we’d gotten under control—algal blooms. I worry what this will mean for our community. Any thoughts?
Worried on the Water (a.k.a. Tom Fuhrman)
Although photosynthesis fuels much of life on Earth, harmful algal blooms are a troubling event when they become primary production gone bad. The mavens have spent quite a bit of time in places like the Gulf Coast and Puget Sound where algal blooms have meant not only diminished water quality and beach closures, but bad air quality, inability by native peoples to engage in culturally important activities, and economic losses due to closed shellfish harvest too.
Under normal conditions algal growth is fostered by sunlight and warm water, and provides the base of aquatic (fresh or salty) food webs. Unfortunately when water warms up or there is an increase in the amount of available nutrients or light, algal growth can take off. Often this enhanced growth includes more harmful species of algae. These out of control and toxin-containing blooms are called “Harmful Algal Blooms” or HABs for short.
Having a HAB event is not a pretty thing. Water quality decreases not just because of the massive amount of algae in the water, but also because of toxins released by the algae or because of low oxygen levels caused by the accumulation and decomposition of dead algae and other organic matter. In some cases the algal toxins even end up in the air causing respiratory distress and neurological problems in people and other animals. All of this means more expensive municipal drinking water purification treatments, a cost we all share, and can result in fish kills—which makes it less fun to be in the water, and litters the beaches with tourist-unwelcoming fish carcasses. Shellfish harvest, an important cultural and economic driver in many areas, is commonly affected, and in some cases there can even be massive bird die-offs.
Figure 1. Signs like this don’t encourage tourist visits. Surface scum is never sexy. (Photo credit: Lake Erie Waterkeeper)
In short, an algal bloom in your town is not good for you, your community, or your local economy. Between the unsightly dead fish and the public health concerns, no one is going to want to rent a fishing boat, relax on the shore, or go for a swim.
Figure 2. Fishing anyone? (Photo credit: Ohio Department of Natural Resources)
But as we mentioned above, there are a combination of factors that lead to HABs and there are some things that you can do to reduce the likelihood of one occurring. Increasing water temperatures is a hard one to address, but there are some things you can do to try to decrease the temperature of river flow and effluent entering the lake. More importantly though is what you can do about nutrient loading in Lake Erie.
Yep, we know, there has been a big effort underway to decrease nutrients (particularly phosphorus) pollution in Lake Erie. In fact it started in the 1970s in response to algal blooms. Over the past 40 years phosphorus levels have been cut in half. As you said in your letter, for a long time that made algal blooms a mere occasional bother. Unfortunately as lake temperatures and in some areas water clarity increased it seemed like it took less nutrient pollution to stimulate a bloom. Plus changing patterns of rainfall and runoff can also increase nutrient delivery to lakes. This is a fascinating thing about climate change. It’s a stress that often makes other stresses worse. Here you have phosphorus (nutrients) and temperature interacting to make a bloom even though you thought you were doing enough to reduce pollution. This means that we have to be even more vigilant in our efforts to reduce phosphorus if we want to reduce or eliminate blooms, and this challenge will continue as lake temperatures continue to rise over time.
Figure 3. The algal problem can be seen from space! No wonder you can see it on the beach. (Photo Credit: NOAA)
Unfortunately this is not a problem that your community can address independently. Just like the Gulf of Mexico HAB problem stems from remote nutrient inputs stretching all the way up the Mississippi River drainage, your problem is lake-basin wide. Further controlling nutrients will require a concerted effect similar to what was started in the 1970s to reconsider existing water management and land use standards and realign them with the new reality we all face. The Lake Erie Lakewide Management Plan is tackling the need to improve water quality given this new set of environmental conditions, and has produced a great technical overview of Lake Erie Basin nutrient issues:
People concerned with algal blooms in Lake Erie can be part of The Lake Management Plan process.
Good luck! We look forward to our next swim in your Great Lake!
The Adaptation Mavens