Dying Clams Are Telling Us a Story, But Are We Listening?

on May 25, 2016

Clams are to Rivers as Canaries were to Mines: Indicators of Environmental Stress

By Steven Apfelbaum

Last year, on a canoe outing with the Lower Sugar River Watershed Association (LSRWA), I was struck by the hundreds of dead clams found downstream of Brodhead in the tail waters of the mill race and further downstream in the river.

Floating with the Sugar River current, we counted large numbers of flashing white interiors of splayed open clam shells. The water wasn’t clear enough to see the dead clams deeper than perhaps a foot.  But, we could feel them with our hands and our paddles.

Preferred clam habitats of gravels and sands in shallow and deeper reaches had an omnipresent litter of dead clam shells. Also, dead clams littered the exposed gravel bars and mudflats along the margins of the river.

Counting growth rings, like on a tree, we found the smaller clams were eight to ten years, and the larger clams were older than twenty. The perfectly intact shells indicated they had recently perished.

Clams are filter feeders, eating what the river delivers, remaining mostly stationery, embedded in the substrates. The health of the water in the river is reflected by clams – the equivalent of “canaries in the coal mine”. Miners paid attention to the canaries. When they stopped singing, and died, methane gas  would also kill the coal miners.

The dead clams have stopped singing – indicating a polluted condition and stress they could not endure to survive in the river.

Clams are now rare elsewhere in the Sugar River based on LSRWA “Corps of Recovery” canoe trips from near Verona to Brodhead. Surveys in 2015 found few clams where they were common historically.

These dead clams – the river canary – have spoken, and we need to listen!

Dead clams indicate upstream conditions of nutrient enrichment, contaminants and low dissolved oxygen. We already know the Sugar River is threatened with contamination (nutrient enrichment, turbidity, sedimentation) which creates declining conditions for clams, fish, and perhaps our own health.

In 2014, 45 miles of the Sugar River were listed by WDNR and USEPA as nationally impaired waters. Also listed was Searle’s Creek that flows into Decatur Lake, and the lake itself. The open shells of perhaps thousands of dead clams provide substantive evidence that this impairment designation is right.

If shorelines littered with dead clams isn’t sad sight enough, perhaps threats to human health will focus attention on our collective mistreatment of priceless natural water resources. Some may only take notice when a region’s economy declines in recreational, historic and cultural values.  Or when local milk and cheese begin to devalue because of concerns over local water quality.

Unlike other economic development – whether it be a new industry, a new CAFO, a new hybrid corn variety producing  300 bushels per acre – the Sugar River  contributes  an ever increasing economic value for the region and will continue to be a high performing investment if we heed the warning of the clams and treat the river well.

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