A harmful algal bloom (CyanoHAB) results from an excessive growth of cyanobacteria, a photosynthetic bacteria also known as blue-green algae. Cyanobacteria are naturally found in water bodies, but warm, nutrient-rich water can trigger massive blooms that produce toxins harmful to humans, pets, and wildlife. Depending on toxin levels, ingestion of or contact with a CyanoHAB can result in skin irritation, nausea, vomiting, and in more severe cases can lead to organ failure or death. Toxins may also become airborne and can cause difficulty breathing. Children and pets are more vulnerable to adverse symptoms.
Most freshwater blooms occur during late summer or early fall and resemble spilled green or blue paint, thick, pea-soup-like foam, or form floating surface mats. Because extensive cyanobacterial growth can occur in a matter of days, consistent monitoring is necessary to track CyanoHAB development. Volunteers with The Watershed Institute’s StreamWatch Bacterial Action Team help us track new and developing blooms in Central New Jersey [2026 Bacterial Action Team Dashboard].
Suspected CyanoHABs are reported to the NJ Department of Environmental Protection for confirmation and to issue waterbody advisories or closures, and the location is added to a public dashboard of active blooms. [NJDEP HAB Dashboard]
Wargo Pond, a manmade reservoir on the Watershed Reserve, has experienced occasional CyanoHABs following a dam reconstruction in 2023. To identify the key drivers of these blooms, Watershed staff and interns launched a study to monitor seven sites around the pond and its tributaries. We measure temperature, conductivity, total dissolved solids, dissolved oxygen, and pH using a handheld Hanna meter; turbidity with a Hach benchtop turbidimeter; chloride, total organic nitrogen, nitrate, nitrite, and phosphate using a Gallery photometric analyzer; phycocyanin and chlorophyll-a with FluoroSense and AquaFluor meters; and microcystin using an Abraxis toxin kit. With more than 730 samples over three seasons, we have observed a strong correlation between nitrogen and phosphorus levels and CyanoHAB development in the pond, most likely from the Honey Brook tributary or Wargo Pond sediments. The study is ongoing, with the goal of pinpointing nutrient sources and identifying and testing mitigation strategies.
Alongside water chemistry monitoring, a parallel effort is underway to identify which types of cyanobacteria are driving the blooms at Wargo Pond. Water samples are brought back to the Watershed lab, where they are examined under the ioLight, a portable field microscope, to observe cell and colony morphology. This matters because not all cyanobacteria are equally dangerous – different genera produce different toxins, so identifying which type is present changes how a bloom should be treated and reported. So far, Microcystis is the only genus confirmed at Wargo Pond, recognizable under the microscope by its loose, cloud-like colonies of round cells suspended in mucilage.
Microcystis is significant because it is the most common producer of microcystin, the same toxin responsible for most swimming and drinking-water advisories nationwide. Monitoring which cyanobacteria genera appear in Wargo Pond will help clarify not just that a bloom is happening, but how risky it is to the community, and whether the toxin profile is shifting as nutrient conditions change.
As of now, the Watershed Institute is working towards incorporating ioLight technology into our volunteer program to help identify and quantify CyanoHABs in our area. The Watershed Institute is always looking for ways to better our research process and help improve water quality. Volunteers are encouraged to reach out for opportunities to help with the Watershed on our website [All Volunteering Opportunities]!
