Every male smallmouth bass caught in the Wallkill River as part of a federal survey of national wildlife refuges in the Northeastern U.S. had “intersex” characteristics, such as immature eggs that formed in their testes. The likely cause is the presence of endocrine disrupting chemical contamination in the river.

The study was conducted by Luke Iwanowicz of the U.S. Geological Survey, and colleagues, with funding from the U.S. Fish and Wildlife Service. It was published in December 2015 in the peer-reviewed scientific journal Ecotoxicology and Environmental Safety.

“As for causes of intersex other than endocrine disruptors: As an objective scientist I am open to the possibility of other explanations or even environmental factors that increase 'risk', but at the present there is no experimental evidence that supports another cause in smallmouth bass,” Iwanowicz told Riverkeeper.

The Wallkill River National Wildlife Refuge straddles the New York-New Jersey border. The Wallkill is one of the largest tributaries to the tidal Hudson River, coursing out of Sussex County, N.J., and through Orange and Ulster counties in New York before joining the Rondout Creek and meeting the Hudson at Kingston.

Smallmouth bass are considered particularly sensitive to exposure to endocrine disrupting chemicals that mimic estrogen or other hormones, but it isn’t know if that is due to inherent biological susceptibility or due to the influence of their particular habitats within rivers. Some level of intersex has been found in smallmouth bass wherever they have been surveyed.

The endocrine system includes organs and tissues that produce hormones that regulate the activity of cells and organs, communicating the essential physical and chemical functions of the body, including growth and sexual development and reproduction. Effects of exposure in ambient water to these compounds on other living things, including humans and the wider river ecosystem, are largely unknown, but studies have correlated intersex fish with weakened immune systems, poor reproductive success and decreased populations.

Sewage treatment plant effluent and farm runoff have been identified by other studies as relevant sources of endocrine disrupting compounds in waterways where intersex smallmouth bass are found. A decade of studies in the Potomac River watershed has found both to be relevant, but a closer association of intersex smallmouth bass with agricultural land use than with wastewater treatment plant effluents.

Manure itself contains hormones, so runoff from dairies, concentrated animal feeding operations (CAFOs) or even vegetable farms where manure is spread as fertilizer can contaminate water with endocrine disrupting compounds if manure isn’t effectively managed. It’s common on some farms to spread manure that can’t be stored, including in winter, when frozen ground prevents it from being an effective fertilizer and instead results in large pollution events when rain or snowmelt causes large volumes of manure to discharge into waterways. The timing of these pollution events may be particularly poor for fish, since the influx of hormones from the manure can coincide with the time when sex determination is occurring in young fish, in early spring.

Many pharmaceuticals and other compounds pass through wastewater treatment plants, which are designed to reduce pathogens, not remove traces of personal care products, medications or other sources of endocrine disrupting compounds.

The specific compounds affecting the Wallkill, and their sources, have not been studied. The National Wildlife Refuge study was meant to show where additional biological and chemical sampling is needed. It’s possible that relevant sources are either upstream or downstream of the site sampled, because these fish migrate within the river.

A watershed management plan for several subwatersheds of the Wallkill in Sussex County upstream of the refuge (Papakating Creek, Clove Acres Lake and Clove Brook) identified implementing agricultural best management practices to reduce stream impacts as a top priority, and developed a program to assist farmers implement projects. The Black Dirt farming region in Orange County, NY, is downstream of the wildlife refuge. Farm runoff there could also be relevant since bass may migrate up and downstream throughout the year. Sediment, nutrients and pesticides emanating from this region are known causes of stress downstream. There is at least one major sewage treatment plant upstream of the Wallkill River National Wildlife Refuge, the Sussex County, NJ, Upper Wallkill Valley Water Pollution Control Facility, which has been in significant non-compliance with the Clean Water Act for at least three years, apparently for failing to submit discharge monitoring reports as required, according to an Environmental Protection Agency database. (Because no data have been submitted, it’s impossible to say what if any effluent violations have occurred, based on available information.)

Riverkeeper’s community scientist partners have sampled the Wallkill River for fecal indicator bacteria since 2012. All sample sites, including in the refuge, have shown evidence of fecal contamination, and results indicate that the Wallkill and many other tributaries of the Hudson fail to meet federal recreational water quality criteria.

“The bottom line is the more you keep out of the water, the better, whether you’re targeting nitrogen, pathogens or hormones,” Iwanowicz said. “The same strategies achieve multiple goals.”

The Wallkill, where five fish were sampled in 2008, was not alone in its high rate of intersex fish. Intersex smallmouth bass were found at all 12 wildlife refuges sampled, with rates of intersex smallmouth sampled at each refuge ranging from 60-100%. (These rates exceed the lowest reported rate of 10-14% intersex smallmouth bass surveyed in the Northeastern U.S.) Across all refuge sites surveyed, 85% of male smallmouth bass showed intersex characteristics. (Intersex largemouth bass were found at a rate of 0-100% at 13 wildlife refuges. No largemouth bass were caught in the Wallkill survey.)

The study suggests that sources and mixes of endocrine disrupting compounds may be unique to the Northeastern U.S., compared to surveys in other regions, resulting in higher intersex rates in these fish. The authors of the study call for landscape analysis and comprehensive chemical analysis of the water to test this hypothesis.

We echo that call. This study is further evidence that the work of Riverkeeper’s community scientist partners, the Wallkill River Watershed Alliance and others is critically needed to restore the Wallkill River to health, and that more work needs to be done to understand and address the major causes of degradation in the watershed.