The Department of Environmental Conservation released its latest Hudson River Estuary Action Agenda earlier this summer. It describes the organization’s five-year goals for the 153 miles of the river south of Troy, which feel the effect of the ocean’s tides twice a day.
The agenda describes several threats facing the river -- runoff and contamination caused by increasing rainfall, invasive species that could harm indigenous fish populations, harmful algal blooms, and bigger boats.
And many of these issues are interrelated. Increases in extreme weather, like heavy rainfalls, can push nutrients from farm fertilizers or contamination from city streets into the river and feed blue-green algae, or cyanobacteria, that make up harmful algal blooms.
And drought can also spur the growth of the blue-green algae, says Chris Solomon, aquatic ecosystem ecologist with the Cary Institute.
“If you imagine the Hudson like a bucket full of water. If you put a garden hose into that bucket and open the tap, and just leave the water running, the bucket's going to continually overflow as new water from the hose pushes out the old water that was in the bucket. But if you turn the garden hose down to just a trickle, then you're only very slowly replacing the water that's in the bucket. And that can give the algae time to really grow and reproduce there in the water. When you're flushing them out quickly, they can't really get a foothold,” Solomon said.
Solomon says the combination of heavy rainfall dumping nutrients into the river followed by drought makes the harmful algal blooms more likely. He said the biggest bloom they’ve seen in Hudson in the past 40 years happened in the fall of 2025.
Another source of contamination the report describes is the large family of forever chemicals known as PFAS. The report says not enough is known about the concentrations in the Hudson.
Dan Shapley, Senior Director of Advocacy Policy and Planning at Riverkeeper, says sources of PFAS could include superfund sites like the Stewart Air National Guard Base and everyday products that contain PFAS that make their way into the Hudson.
“Our sewage treatment plants are accepting waste from landfills and those sewage treatment plants do not treat those chemicals. They don't remove these PFAS chemicals. So, we are passing some of these chemicals through our sewage systems back into our waterways. That's a big problem,” Shapley said.
Shapley said Riverkeeper will work with the Hudson 7, seven communities that draw drinking water from the Hudson, including Poughkeepsie, Rhinebeck, and Hyde Park, to monitor PFAS levels.
Another threat is the presence of invasive species, like zebra mussels and round goby, that already live in the Hudson.
Round goby consume the eggs of some nest-building fish like smallmouth bass. They spread from the Great Lakes, and were first documented in the Mohawk River in 2014, and in the Hudson in 2021.
“Really what we’re going to have to do now and forever is monitoring for those invasive species, sharing what we know about them, and then think more strategically about how we’re going to treat them,” said Heather Gierloff, New York State Department of Environmental Conservation (DEC) Estuary Coordinator.
Gierloff said strategies could include installing barriers to prevent invasive species from getting into the Hudson. She said technologies like eDNA, which can detect what species are in the water, can help with monitoring.
Besides the threats of species living in the water, some threats are on the surface. The report describes an increasing number of larger river vessels.
“As shipping ships become bigger to move more material in a more efficient way, there is a concern with the river and making sure that’s done in a safe way. We don’t want boats to hit the bottom of the river. We don’t want boats to hit the bridges,” Gierloff said.
Gierloff said in the past five years, DEC has increased the number of tide stations, which monitor water elevation.
“So, as we have bigger vessels, we're gonna have a smaller space of error that we can make before there's an impact to something,” she said.
Overall, Gierloff said that the Hudson River, despite all the challenges, has benefited from increased regulation and monitoring.
“In the past it has been way worse. I think if we visited the Hudson back in the 1960s and 70s before the environmental movement, we’d all be in shock.”
