Can Algal Blooms Affect Small Lakes and Ponds?

Algal blooms, such as the blue-green cyanobacteria which has plagued much of the United States, has stolen the headlines in recent years for the damaging effect it has on environmental and human health. The majority of the news stories have focused on larger bodies of water, including the ongoing fight to clean up Lake Erie in northern Ohio.

However, a new study from The Ohio State University has demonstrated that harmful algal blooms (HABs) can be just as damaging to smaller lakes and ponds, as well. The team behind the paper assessed toxin levels in 24 sites across the state over a three-month period in 2015 and found that almost half of the samples contained dangerously high levels of microcystin (MC), a toxin produced by cyanobacteria which can compromise drinking and irrigation water supplies.

Alarming results

The report, which was published in the journal Environmental Science and Technology in June of this year, tested samples from 24 public and private lakes and ponds in central Ohio in the summer of 2015. Specifically, the researchers were looking to quantify levels of MC, as well as assessing the structure of microbial communities and the chemistry of the water in the lakes.

They found that 10 of the sites showed notable levels of MC, while one in particular showed repeated concentrations which were cause for immediate concern. “Samples from this lake in early July were particularly concerning, as they contained four times the recommended amount of microcystin for recreational use and more than 800 times the recommended level for drinking,” explained Seungjun Lee, co-author of the report.

Agricultural run-off to blame

The toxic algal blooms are thought to be caused primarily by agricultural run-off. When farmers do not follow sustainable methods of sludge destruction, a cocktail of fertilisers, herbicides and animal waste can find its way into these bodies of water, thus interrupting the natural harmony of the water’s composition. The rich nutrients they bring with them can allow algae to flourish to the detriment of other organisms living in the water.

According to the study, tile drainage is the chief culprit when it comes to improper disposal of agricultural waste. The term refers to a widely used technique of removing excess sub-surface water beneath the soil, which is often deposited straight into the nearest pond or lake and then feeds the algal bloom.

Better care imperative

The presence of toxic algal blooms in small lakes and ponds is not only damaging to the marine life which lives in and around the water, but also humans as well. If the water comes into contact with human skin it can causes blemishes and rashes, while if ingested, it can lead to intestinal discomfort or even damage to the liver and nervous system.

Of course, in larger sites like Lake Erie, which is the source of drinking water for almost 11 million Americans, the dangers are more obvious and immediate. But even in smaller sites like the ones surveyed in this study, there is cause for concern. Better management of land and agricultural waste would go a long way to ensuring that blooms like this are kept under control.