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Berry: Battling harmful algal blooms requires knowledge, vigilance

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Harmful algal blooms

A harmful algal bloom in Cayuga County.

Harmful algal blooms, or HABs, are well-known among Finger Lakes locals as an impediment to fishing and swimming. Recurring HABs in Owasco Lake and other Finger Lakes have prompted demands for improved public safety measures, including a reporting system for HABs observations used to direct public beach closures and recommendations from public health officials, as well as advancements in water filtration for drinking water consumers. Fortunately, the recent cooler weather has temporarily reduced the reporting of HABs. However, the increasing frequency and intensity of HABs during the summer months threaten water quality, recreational opportunities, tourism and agriculture. Through collaborative observation and informed awareness, the identification, avoidance and reporting of HABs have improved significantly to safeguard watershed communities from the existential threat.

Aquatic ecosystems provide for an abundance of algae species, most of which are harmless and critical members of food web systems. But certain species of algae in overabundance can produce toxins. The circumstances that lead to the occurrences of HABs are not fully understood, but analytical research has identified the primary drivers, or causes, of HABs. The conditions that are most favorable for a HAB to occur include a combination of environmental conditions, namely increased temperatures, low wind, ample sunlight and available nutrients.

HABs in the Finger Lakes are commonly caused by an excess growth of cyanobacteria. Cyanobacteria, or blue-green algae, are ancient photosynthetic bacteria that are predominantly responsible for the production of oxygen in the earth’s atmosphere, having inhabited aquatic ecosystems for billions of years. When in abundance, blue-green algae can resemble a thick, green, paint-like material that tends to accumulate near shorelines and coves. The associated toxins of these blooms are ordinarily released into the surrounding water upon cell death. Microcystins are the most widespread cyanobacterial toxins and accumulate in the tissues of fish, mussels and zooplankton — a process known as bioaccumulation. Microcystins are primarily liver toxins and can affect other animals, such as humans, that may inadvertently consume or come in contact with contaminated water.

As photosynthetic organisms in freshwater systems, the development of a harmful algal bloom requires the presence of a limiting nutrient, the nutrient in lowest quantity relative to the organisms’ needs, phosphorus. In other words, phosphorus is a driver that controls algal growth due to scarcity. Moreover, an excess input of phosphorus can significantly increase algal productivity. Stormwater runoff can carry nutrients from the Owasco Lake watershed to the lake, thereby "feeding" toxic cyanobacteria. For Owasco Lake, nutrient loading is dominated by watershed-born sources, nonpoint sources that can be significant during heavy storms. This salient point portends the importance of watershed-based initiatives that stabilize soils, target the reduction of excessive fertilizers, and reduce nonpoint source pollution.

This video from the state Department of Environmental Conservation provides guidance for identifying harmful algal blooms, which are beginning to surface in state waterways for the summer season. Visit for more information about HABs in New York state.

Recognizing and differentiating HABs from non-harmful algal blooms can be difficult. Improving the public’s ability to identify blooms prior to aquatic recreation guides the avoidance of associated toxins. Cyanobacteria are non-filamentous, meaning that they do not grow as strands, and although observed at the surface with the naked eye, blooms can occur throughout the water column, rather than on top of or below the surface. When in doubt about an observed algae, it is best to avoid the area and report a potential HAB to the New York State Department of Environmental Conservation and/or the Owasco Lake Watershed Inspection and Protection Division for confirmation.

The state DEC maintains a HABs notification page and map of blooms that are present, or have been present. These resources, including a Suspicious Algal Bloom Report Form, can be found online at The online platform allows the public to report a potential bloom to the DEC for review. If the bloom is identified as harmful, it is uploaded to the public HABs map, thus protecting members of the watershed community from exposure through awareness. Swimming, boating or otherwise recreating when a potential bloom is present is not advised. If contact with a HAB occurs, it is recommended that the impacted individual thoroughly rinse off any algae, and seek medical attention if symptoms or reactions develop. Furthermore, discolored water should always be avoided and never used for consumption or food preparation, especially when not made available through a public water supply.

The increasing manifestations of climate change, including the prevalence of weather blockages, heat domes, increasing temperatures and intense storms, will likely cause HABs to occur more frequently in the future. Therefore, it behooves the watershed community to become educated on HABs identification and reporting, and to support watershed protection via regulations and recommended practices. Ongoing research, education and the adoption practices that limit or intercept nutrient-rich runoff are vital to protecting the local economy, aquatic ecosystems, water quality, and the health and safety of the public. 

Ally Berry is a watershed inspector with the Owasco Lake Watershed Inspection and Protection Division. For more information, visit


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