Harmful algal blooms, usually caused by nutrient pollution and subsequent excessive algal growth, have become increasingly common in Ohio and across the U.S.

Unfortunately, the resulting cyanotoxins produced by cyanobacteria (also called blue-green algae) in aquatic environments are disrupting aquatic systems and even causing human health problems.

The algal blooms are the result of excessive nutrients and warmer weather conditions, which stimulate algal growth, often covering the surface of the water. This can be a serious issue because the cyanobacteria frequently occur in drinking-water sources and recreational waters.

Any water containing excessive concentrations of cyanotoxins (e.g., microcystin) are unusable as the toxins can cause severe illness or even death, if enough of the contaminated water is consumed. In addition, aquatic organisms can accumulate the toxins – a way humans indirectly can be harmed if consumed – or be adversely affected due to cyanotoxin exposure, thereby causing an ecological imbalance to the aquatic environment.

Several harmful algal blooms have been reported across Ohio in recent years.

One of the first extensively publicized occurrences of toxic algae was in Grand Lake St. Marys during the summer of 2010.

Thousands of fish were killed and recreational use of the lake was limited due to health concerns. Toxic-algae warning signs were posted again during the summer of 2015 at four beaches on the lake after a woman was sickened by the water.

Lake Erie is another Ohio water body that frequently has had environmental issues due to algal blooms. The worst recent incident was in the summer of 2014 when Toledo had to issue a warning to residents not to use water because of excessive microcystin contamination caused by toxic algae in Lake Erie. The city since has added treatments to minimize future algal blooms.

A toxic algal bloom in the Ohio River also was reported in southeast Ohio during late August 2015. The bloom was caused by Microcystis sp., the same type of algae that has plagued Ohio lakes and is capable of producing liver and nerve toxins. Based on an alert issued by the Ohio Environmental Protection Agency, communities on the river were cautioned as to the safety of the water for human consumption.

So why so many recent occurrences of toxic algal blooms?

A number of causes are suspected, but some of the most commonly cited are increased nutrient loads (phosphorus and nitrogen) from upstream watershed land areas and higher average annual temperatures, along with a concurrent shorter winter and earlier onset of spring.

As noted by the Ohio EPA, "the primary sources of nutrient pollution are runoff of fertilizers, animal manure, sewage-treatment-plant discharges, stormwater runoff, car and power-plant emissions and failing septic tanks." In response to these concerns, Ohio leaders are working on a statewide monitoring network and nutrient-reduction strategy that will document ongoing nutrient-reduction activities and identify areas where more work is needed.

So how can we help prevent harmful algal blooms?

One way is to fertilize lawns with only the recommended amount and application frequency. This will help prevent nutrient runoff that eventually ends up in nearby surface waters.

In addition, maintain septic systems to prevent wastewater from leaking and seeping into nearby lakes and streams.

Greg Smith is a senior research scientist at Great Lakes Environmental Center in Columbus and a member of the Hilliard Environmental Sustainability Commission.