Harmful Algae Blooms (HABs)
Nutrients and algae are a natural component of the Ohio River and are present throughout the year. Some species, under certain conditions can produce toxins that affect human health and the environment. During optimal conditions, when nutrients like phosphorus and nitrogen are in excess, some algae may rapidly proliferate causing a “bloom.” During a bloom, the algal concentration may go from a few thousand cells per millimeter (cells/ml) of water to hundreds of thousands or even millions of cells/ml. Algae blooms are most common in the summer, although they may occur at any time of the year. On the Ohio River, the conditions that allow these blooms to occur are typically low and slow flow, clear water, and warm water. Some algae blooms can lead to harmful impacts on the environment including low/no oxygen conditions, acidification, or unsightly conditions or odor that affect recreation. Cyanobacteria can produce toxins that lead to negative impacts on human and animal health and are referred to as Harmful Algae Blooms (HABs).
The first HAB identified on the Ohio River in 2008 impacted 30 miles of the river and lasted 10 days. In 2015, a HAB occurred which ended up covering over 600 miles of river and lasted over two months. This was unprecedented for a large river in the United States. Another HAB occurred in 2019 which covered 300 miles and lasted over a month. ORSANCO’s research has identified specific flow patterns which have set the conditions that allow these blooms to occur. Climate change has likely allowed this alteration of the flow patterns which suggests that future large HAB events are likely and will be a challenge for users of the river, whether for recreation or drinking water use.
In order to address increasing likelihood of potential HABs, in partnership with the US Environmental Protection Agency and Indiana Department of Environmental Management, ORSANCO has developed a HAB app, an online GIS-based tool, to predict the occurrence of future blooms on the Ohio River. The tool uses flow data from the US Army Corps of Engineers gauges to compare the current flow to that experienced in 2015 and 2019 when HABs occurred. The tool displays the probability of a bloom occurring and persisting and shows relevant water quality data from 8 locations on the river.
ORSANCO operates 4 datasondes with telemetry systems that collect data annually from May-September every 30 minutes. Data collected includes pH, conductivity, turbidity, dissolved oxygen, temperature, and chlorophyll a. These systems are located at Pike Island Locks and Dam, Meldahl Locks and Dam, Markland Locks and Dam, and Newburgh Locks and Dam.