Summer is the peak season for water-based recreation and relaxation. Unfortunately, it is also the peak season for Harmful Algal Blooms (HABs). Understanding and being able to recognize this natural phenomena is important to keeping you, your pets, and your local watersheds safe.

HABs occur when excess amounts of phosphorus enter a water body, usually by stormwater runoff carrying fertilizers and animal waste, or by faulty septic and sewer systems. Cyanobacteria, also known as blue-green algae, take advantage of the extra nutrients and their populations explode in number.

In 2023, the New Jersey Department of Environmental Protection (NJDEP) recorded HABs at 49 water bodies. Five of the six counties within the Raritan River Basin experienced HABs: Hunterdon, Mercer, Middlesex, Morris, and Somerset Counties.

HABs are associated with fish kills, massive die-offs of aquatic life due to low oxygen levels in the water or due to cyanotoxins released by cyanobacteria. Cyanotoxins can harm humans and pets, and are especially dangerous to children. Health effects in humans include abdominal pain, vomiting, fever, and muscle weakness. If you experience any of these or symptoms resembling an allergic reaction or the flu and believe you may have been exposed to a HAB, seek medical care. Depending on the length and severity of exposure, more serious health complications may include liver and kidney damage, respiratory paralysis, and death.

Protect yourself by staying up to date with advisories issued by the NJDEP. Monitoring occurs via daily flight reports and by local health authorities sampling suspected sites of HABs for laboratory analysis. This data can be interpreted in conjunction with reports from the Lower Raritan Watershed Partnership’s Pathogen Monitoring Program, conducted in partnership with Rutgers Cooperative Extension of Middlesex County and the Interstate Environmental Commission.

Each week, LRWP’s volunteers sample non-bathing beaches along the Raritan River to test for presence of fecal matter and disease causing bacterium, and report findings within 24 hours on the LRWP website, via the Rutgers Raritan River Hydrologic Observatory, and via the regional Community Water Quality Testing program coordinated by the Billion Oyster Project. This data is also uploaded to the US Environmental Protection Agency’s STORET (STOrage and RETrieval) and WQX (Water Quality Exchange) systems used for managing and sharing water quality monitoring data.

There are four Recreational Guidance Advisory Levels depending on the amount of cytotoxins identified in the lab reports. If in doubt about what activities are safe, refrain from drinking, swimming, boating, fishing, or consuming fish products sourced from the water body in question.

Volunteer reporting saves lives! To identify HABs, the NJDEP recommends looking for “a layer of bright bluish‐green or white paint on the water surface. Other evidence of a potential cyanobacterial HAB could be discolored or pea‐green colored water, parallel streaks, or green dots/globs in the water.” If you believe you have spotted one, help keep others safe by reporting it to the NJDEP using their online form.

You can reduce HABs through choices made away from the water, as well. The Lower Raritan Watershed Partnership has tips for reducing fertilizer usage and advocating for proper stormwater management. The NJDEP recommends growing native plants to create a riparian buffer can decrease the amount of rain that flows off your property, picking up pollutants before it enters your waterfront. Minimizing opportunities for stormwater runoff to carry pet waste and fertilizers into waterways minimizes the chance of a HAB occurring.

Summer is the season for swimming, not sickness. Be observant, educate others, and stay safe as you recreate!