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Big crowd gathers to learn about Wallkill’s harmful algae, and what we can do about it


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As many as 65 people, plus dozens more online, attended a Wallkill River Watershed Alliance forum on Harmful Algal Blooms in the Wallkill River, focused on what we know and don’t know about cyanobacteria, its presence in the Wallkill River, and what we can do to reduce the extent and duration of future blooms. The event was supported by the DEC’s Hudson River Estuary Program, Riverkeeper and the Benjamin Center at SUNY New Paltz.

In 2016, the Wallkill River experienced a Harmful Algal Bloom of cyanobacteria that was, as far as anyone knows, both far more severe than ever before on the river, and more severe than any other river in New York. It persisted, with shifting extent, for at least 60 days, and affected some 30 miles, with observations of isolated blooms outside these areas and times. For more background, see our press releases from August and September with the Alliance on the topic, and an op-ed in the Times Herald Record, It’s time to clean up the Wallkill River.

As of today, the Harmful Algal Bloom has ended. The last observed algal bloom was in late October. With the end of the bloom, the risk of exposure to toxins from the bloom has ended, too.

Here are some new insights from the talks:

Cyanobacteria are the potato chips of the food web
The diversity of algae in a river is an indicator of its health, as algae is the base of the aquatic foodweb. Harmful Algal Blooms occur when one or a small number of cyanobacteria (a.k.a. blue-green algae) species proliferate and grow in abnormally high densities. Even absent any risks to human health or wildlife, this shift in the base of the food web is like replacing a well-balanced meal with a diet made up exclusively of potato chips, to use the analogy of Jillian Decker, PhD, a SUNY Rockland scientist and Wallkill River Watershed Alliance board member.

Toxins are only part of the risk from cyanobacteria
Different types of toxins produced by different types of cyanobacteria carry different risks, with the most common type documented in New York State (and the Wallkill River) putting people at risk of diarrhea, vomitting or other gastro-intestinal distress, and liver damage. Other types of toxins can cause nerve damage, and are responsible for the deaths of dogs from exposure around the state and country. Whether or not a Harmful Algal Bloom is producing toxins, it produces other compounds that can cause skin rashes and other reactions, with those with other allergies generally more susceptible. For these and other reasons, authorities recommend avoiding contact with any water affected by visible scums.

Algae present at the community gardens in New Paltz in 2016 prompted a closure of irrigation lines. (Photo courtesy Emily Vail / NYS DEC Hudson River Estuary Program)

Algae present at the community gardens in New Paltz in 2016 prompted a closure of irrigation lines. (Photo courtesy Emily Vail / NYS DEC Hudson River Estuary Program)

Irrigation may spread toxins to food
While the risks of exposure from drinking water, or recreational activities are well documented, the Wallkill River harmful algal bloom this summer raised many questions among farmers, gardeners and others about the safety of irrigation with river water during the bloom. Toxins can accumulate at high levels on food, particularly lettuces, green onions or other foods that naturally have areas where irrigation water can accumulate, according to James Hyde, a Department of Health research scientist.

Nutrients, high temperatures and still water are key ingredients for blooms
While nitrogen and phosphorus are key nutrients, there can be too much of a good thing, leading to algal blooms when runoff of agricultural fertilizers and sediment, urban stormwater runoff, sewage or septic effluent, or other sources overwhelm a river or lake. Record high temperatures and low river flows due to persistent drought are believed likely to be key ingredients in the duration and extent of the Wallkill River bloom. Climate change is making both temperature and precipitation conditions more conducive to blooms such as we witnessed this year on the Wallkill, but even given the same basic weather conditions across our region, the Wallkill was unique among Hudson River tributaries for the presence, extent and duration of a Harmful Algal Bloom, indicating that specific conditions in its watershed can be addressed to make it more resilient to extreme weather conditions.

But there are exceptions, caveats and many ongoing questions
Cyanobacteria blooms are happening across the state and country, and apparently with increasing frequency and intensity (though increased monitoring and reporting may explain some of the increased documentation). Some of these happen under predictable conditions, others are confounding, with blooms occurring in the absence of high nutrients, or lakes with recurring blooms remaining clear this summer, when temperatures were up and flows were down. “Scientists don’t have good answers for this,” said Rebecca Gorney, PhD, a DEC research scientist. There are ecological mysteries to be investigated, particularly associated with blooms in rivers, which have been studied much less than lakes.

The Wallkill River Watershed Alliance and Riverkeeper will analyze data to help answer these questions
We have over 250 samples from 2016 that will be analyzed for nutrient content, and over 150 that can be analyzed for algae. Analyzing these datasets this winter should provide new insights, and no doubt new questions. Expect presentations of the results this Spring at a Wallkill River summit is planned by the Wallkill River Watershed Alliance.

The DEC is considering options for more in-depth Wallkill research
In 2017, the Department of Environmental Conservation will conduct water assessments throughout the lower Hudson River watershed region. This once-in-five-year event is an opportunity to channel additional expert attention to the Wallkill, and prioritize pollution reduction strategies. Riverkeeper and the Wallkill River Watershed Alliance will advocate for funding necessary for a thorough study.

The Wallkill was impaired for recreational use, but it may or may not be “impaired”
The Clean Water Act requires waters impaired by pollution to be listed on the state’s 303(d) list and prioritized for developing “pollution diets.” In Riverkeeper’s view, the Wallkill was clearly impaired for recreation for weeks on end, as public paddles were canceled, a kayaking business had to move tours elsewhere, signage at access points warned anglers and boaters of the risks of exposure, and a private beach was closed. However, the presence of Harmful Algal Blooms alone are not sufficient, under current state policy, for identifying impaired waters; they must be proved to be caused by excess nutrients or other pollutants. We’ll go where the data leads us.

There are many more facts and insights from the presentations, which were captured on video via a series of Facebook Live feeds by the Wallkill River Watershed Alliance. Watch them here:

Rebecca Gorney, DEC research scientist
James Hyde, DOH research scientist
Jillian Decker, SUNY Rockland and Wallkill River Watershed Alliance scientist
Dan Shapley, Riverkeeper Water Quality Program Director – plus Q&A with all speakers

Factsheet: Nitrogen and Phosphorus Pollution: What You Can Do

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