Ramapo River: What is Amiss With the Mussels?

By Karen Dougherty

In January 2008, a disturbing article appeared in the Northeastern Naturalist. Written by Dr. David L. Strayer, a freshwater ecologist, it portrayed an unsettling picture of New York’s Ramapo River ecosystem. Dr. Strayer studied the mussel population in several New York locations between 1992 and 2006 and found significant deformities in all three species of the Ramapo River’s freshwater unionid mussel population. Deformities of this magnitude are often indicative of pervasive water pollution.

The National Park Service says that mussels serve important functions in aquatic ecosystems. They are an important part of the food chain and help maintain water quality. The US Fish & Wildlife Service estimates that “70% of our freshwater mussels are extinct, endangered, or in need of special protection. Many of their problems stem from how they live and changes that have occurred to their habitat during the past 200 years. Pollution, especially non-point source pollution, causes the greatest threat to native mussels.”

Deformed mussels are easily recognized. According to Dr. Strayer, the mussels have “severely shortened posterior ends. The posterior margin of the shell is irregular or ragged, the periostracal layers often are thick and distorted, and the two valves often do not fit together well at the posterior end of the shell, resulting in a marked gape. The deformation of the shell may be so severe that it is difficult to identify the species. I have not observed the soft tissues of animals affected by this deformity, but they presumably are distorted as well.”
Dr. Strayer found this mussel deformity at four other New York sites but none seemed to be as pervasive as those found in the Ramapo River. The examination of area mussel specimens prior to 1990 did not reveal deformities of this nature. Therefore, Dr. Strayer concludes that this is a recent phenomenon, possibly caused by a chemical associated with agricultural or residential use.

Today, large amounts of chemicals such as fertilizers, herbicides and pesticides are finding their way into our waterways, where they are wreaking havoc among aquatic ecosystems. Mussels are an important food source for many fish, birds and mammals. Based on this information, it is easy to imagine that the demise of such an important species as the freshwater mussel may trigger a cascade of detrimental consequences which we will be unable to rectify.