Lakes around the world are turning green. While going green is usually a good thing for the environment, in this case, it's not. Lakes "turning green" due to algae blooms are causing a range of environmental problems, including increased greenhouse gas emissions.
What Causes Green Lakes?
An algal bloom is a rapid increase in the amount of algae in a body of water. Excess nutrients, such as phosphorous and nitrogen, in the water are often the cause of algal blooms. These blooms tend to turn water green but may also turn them red or yellowish-brown. If a bright green bloom occurs, it's likely because of blue-green algae, which is actually a type of bacteria.
Human activities are often the reason excess nutrients enter the water. Agriculture is a leading source of these nutrients, as fertilizers applied to crops and animal manure can introduce excess nutrients into waterways. Fertilizers applied to lawns and gardens also contribute, and stormwater and wastewater may carry excess nutrients into the water. When a body of water is overloaded with nutrients, the phenomenon is called "eutrophication."
Problems Associated With Green Lakes
Algal blooms lead to a number of problems. They can release toxins that cause illness and death in people and animals. Microcystis cyanobacteria, or blue-green algae, can create 80 different types of a toxin called microcystin. This toxin can cause vomiting, diarrhea, abdominal pain and liver pain in humans, and removing these toxins requires the use of chemicals and carbon filters.
Algae blooms can also lead to depleted oxygen levels in water, creating what are called "dead zones." As the algae that make up a bloom start to die off, the bacteria that decompose them increase in number. These bacteria use the dissolved oxygen in the water, potentially depleting it to the point that fish and other animals can't survive.
Additionally, algal blooms increase emissions of methane, a greenhouse gas that is as much as 34 times more potent than carbon dioxide. Water with depleted oxygen favors microbes that produce methane.
Eutrophication Expected to Increase
The occurrence of algal blooms is expected to increase over the coming years. According to a study published recently in the journal Nature Communications, eutrophication in lakes may increase by 25 to 200 percent by 2050 and potentially quadruple by 2100 at the current rates of population growth and climate change. This increased eutrophication may increase methane emissions by between 30 and 90 percent over the next 100 years.
The authors cited three mechanisms that are expected to have the largest impact on increasing eutrophication. Human population growth is one, as it will result in more sewage and fertilizer use. Another is increased storms and runoff of stormwater. The third is the warming climate, as warmer water tends to lead to more algae growth.
Other impacts of climate change are also expected to increase the likelihood of lake greening. Because algae require carbon dioxide to survive, increased levels of it encourage the growth of algae. Sea level rise may create coastal water that's more shallow and stable, which are the perfect conditions for algae growth. Climate change could also lead to more droughts, which increase the salinity of freshwater. In turn, the increase in salinity may lead to the growth of marine algae in freshwater.
In shorter terms, green lakes are worsening climate change, and climate change is making lake greening more likely.
What Can We Do?
What can be done to stop lakes from turning green and contributing to climate change? The key change we can make is improving nutrient management.
Agriculture is a leading source of nutrient pollution, so changes to agricultural practices could have the biggest impact. Reducing fertilizer use as well as ensuring that fertilizer is applied during the right time of the year using the right methods is crucial. Precision agriculture techniques can help farmers apply fertilizer more efficiently. Additionally, keeping animals away from streams can help prevent nutrient pollution from manure.
Other ways that farmers can help is by planting buffers of deep-rooted plants that can absorb or filter excess nutrients along bodies of water. They can also plant cover crops to reduce erosion.
Homeowners and businesses should also reduce their use of fertilizer. People who have ponds or other bodies of water on their property can take steps to prevent and remove excess algae. For instance, dredging a pond can remove sediment that may contain excess nutrients, and adding an aerator can help encourage oxygen diffusion and control algae growth long-term. It can also be helpful to plant a buffer zone around the pond.
Taking the Right Steps Today
Green lakes can release harmful toxins and marine life. They also increase greenhouse gas emissions, making climate change worse. Climate change, in turn, worsens algal blooms, creating a feedback loop.
It's extremely critical that we address both of these problems for the health of the environment and the people and animals depending on it.
All MOTHER EARTH NEWS community bloggers have agreed to follow our Blogging Guidelines, and they are responsible for the accuracy of their posts. To learn more about the author of this post, click on their byline link at the top of the page.