Mussels in the Blue III – Water Quality and Threats
By Craig Thompson
Over the past two weeks I’ve told you about one of my favorite rivers (the Blue River) and favorite aquatic species (Mussels). Although the Blue River currently supports nearly 17 mussel species, habitat alteration, pollution, and the introduction and spread of non-native clams (Corbicula) have led to the extinction of some species from the river. More than half the surviving native mussel species at 159th exhibit declining populations. Mussels as a group are considered one of the most imperiled freshwater organisms in North America. Mussels are in serious danger and many of the declines in mussel populations at 159th and other sites on the river can be attributed to flood-control and urbanization projects.
Many of the lower reaches of the Blue River have been channelized. In fact, when we arrived last summer (2012) to sample the Byram’s Ford site, we found the river had been altered and straightened. Flood-control projects like the one at Byram’s Ford result in the loss of habitat for mussels and other aquatic life. The original habitat at this site was riffles, runs, and some backwaters with a medium bend in the river. Now, the river is deep and straightened, and it is hard to get in to sample. Riffles aerate the river and provide essential dissolved oxygen for many aquatic organisms. Bass, sunfish, madtoms, darters, and many minnow species use riffles for food, reproduction and shelter. Riffles are important for mussels as well. In 2009, this site had a productive mussel community including one SINC species, the Yellow sandshell (See the Table below).
The original riffles, gravel bars, and adjacent backwaters also were important feeding areas for waterfowl and herons. Ultimately, with the loss of riffle habitat and the increase in water depth, we may see a decline in the diversity and abundance of some mussel species at this site. The following picture of the Blue River at Coalmine Road (not far from the Stadiums) gives you an idea of what the river looks like lower in the watershed.
Since coming on board with EPA, I have observed a number of changes to the upper Blue River basin. When I was enrolled in classes in the 1970s at Johnson County Community College, Antioch Road was just two lanes and the land south of the college was mostly farmland and pastureland. Over the years, construction crews have widened many of these roads to accommodate the accelerated growth moving into south Johnson County. On my field trips to stream monitoring sites in the county, I have observed many water quality problems associated with all this new growth. I am usually disgusted by the way construction crews build silt fences and how these fences never do their intended job of preventing exposed dirt from running off into waterways. These types of activities contribute to the runoff of sediments into streams which can bury mussels. Also, mussels are very sensitive to many other types of pollution as a result of stormwater runoff from parking lots and residential lawns. Heavy metals, pesticides and herbicides are some of the constant water quality problems mussels must face in the Blue. In the future, the conservation of native mussels will depend upon how well we protect the land from soil erosion and stormwater runoff. Basically, we need to take care of our watersheds.
Over the years I have been collecting and observing freshwater mussels from streams throughout Kansas and Missouri. The Blue River at 159th (shown above during high water) is a gem of a site. At this time, I believe that the physical, chemical and biological attributes are very good at this site. Every time I have sampled this urban stream site, there is good flowing, permanent water, which most mussel species require. It will be interesting to discover in the coming years what aquatic species are able to live and tolerate the rapid environmental changes that are occurring in the Blue River basin. And, this is especially true for the mussels in the Blue at 159th.
Craig Thompson lives near the mussel-less (except for Asian clams) Brush Creek, a tributary of the Blue River. He is a Life Scientist with the Environmental Assessment and Monitoring Branch (EAMB). Craig joined EPA in 2009 after spending thirteen years with Kansas Department of Health and Environment. He assists EAMB staff with water quality and biological sampling surveys throughout the Region 7 area.
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