On Wednesday, researchers at Cary Institute of Ecosystem Studies observed a massive algal bloom in the Hudson River Estuary in a large stretch from Kingston to Norrie Point in Staatsburg. The bloom has been confirmed as Microcystis, a cyanobacteria that can produce toxins that are harmful to people, pets, and wildlife.
This is the largest cyanobacteria bloom that Cary researchers have seen in almost 40 years of monitoring the Hudson River. They encountered it while collecting samples for an ongoing survey of the river’s lower food web, funded by the Hudson River Foundation. The survey has sites that span from the mouth of the river in Lower Manhattan to the Federal Dam in Troy, NY.
At the Kingston site, the bloom complicated routine plankton collection. Cary research technician Sophia Atkinson described conditions. “In slower-moving parts of the river, green paint-like swirls coated the water’s surface, and along the shoreline you could see green clumps. When we pulled out the net we’d been towing in the river’s channel, it was so clogged with Microcystis that it wouldn’t drain properly.”
The New York State Department of Conservation (NYS DEC) has confirmed additional harmful algal blooms (HABs) in the Hudson River near Beacon, Hyde Park, Tivoli, and Hudson, as well as in the Wallkill River and Rondout Creek, which feed into the Hudson near Kingston.
“The magnitude and extent of this cyanobacteria bloom is unprecedented, and concerning. While Microcystis is often observed in the Hudson, and sometimes produces blooms, this is by far the largest bloom we have observed,” says Dr. Chris Solomon, a senior scientist and aquatic ecologist at Cary Institute.
Cary’s Hudson River research group is reviewing decades of data from the Kingston site to put the bloom in historical context. The team’s sampling record in Kingston dates back to 1987.
There are several possible causes of these harmful algal blooms in the Hudson and its tributaries. Warmer temperatures favor cyanobacteria in several ways, and monitoring has shown that water temperatures in the Hudson have been increasing. Wastewater, agricultural runoff, and atmospheric deposition all contribute nutrients to the river that promote high algal abundance. Relatively dry conditions in August may also have altered nutrient availability in ways that favor cyanobacteria (and Microcystis in particular).
Cary researchers are working to understand these possible causes. Riverkeeper, the Department of Health, NYS DEC, and other partners are also engaged in monitoring the current bloom.
Dan Shapley, Riverkeeper’s Senior Director, Advocacy Policy & Planning, comments, "Cary Institute's historic and ongoing monitoring of the Hudson provides one of the most important sources of foundational information about the river, its health, and its response to changing conditions. Riverkeeper greatly values our ability to work with Cary and other partners on the river to understand the conditions that led to this harmful algal bloom, how we can mitigate its impacts, and avoid recurrence."
People and pets should avoid waters affected by harmful algal blooms, as their toxins can be inhaled, ingested, or cause skin irritation. Dogs are particularly at risk, as they’re more likely to drink contaminated water.
If you notice algal blooms on the Hudson or other waterways, please report them using NYS DEC’s Suspicious Algal Bloom Report Form, or email HABsInfo@dec.ny.gov. Close-up and landscape photos aid in identification and help document the extent of impacts. To view an interactive map of confirmed HABs in New York State, visit the NY HABs System.
