The rangia clam is a quarter-sized bivalve that most of us have never heard of. Not consumed by humans, it is a vital element in the marine life of Galveston Bay, the first link in the food chain for the bay’s shrimp, crab, oysters and many varieties of fish.

But now, this tiny creature that usually thrives in the bay’s mixture of fresh and saline waters is dying in one northeast inlet of the bay near Baytown, causing alarm among scientists (“Clams’ deaths may reveal future of bay’s viability,” Page A1, Oct. 25). The scientists, conducting a two-year study for the National Wildlife Federation, are advising state regulators on the required amount of water flowing in from the Trinity River to protect the ecological viability of the bay’s ecosystem.

They are not yet sure why they are finding nothing but empty shells in this area, but they do know that the rangia clam cannot grow or reproduce if the water is too salty. So this is an important finding, because rangia clams are only found near sources of freshwater, and they cannot leave in search of better conditions if that estuary water becomes too salty. They consider the clam a bellwether for marine wildlife of the area, the equivalent of the canary in the coal mine.

The Trinity River, which supplies water to Houston and Dallas, is already overburdened, with all of its water serving industries, farmlands and growing city populations. In 2011, the state’s driest-ever, one-year period, all of the Trinity water flowing below the Dallas-Fort Worth area was treated wastewater.

While drought is always a factor in the state’s ecological wellbeing, environmentalists and other observers worry that with our economy and population on an upward track, even less fresh water will find its way to our bays and estuaries. And just how much fresh water is necessary for these areas to survive is difficult to assess. Tests are being run on shells and live samples of the rangia, with the hope that results will provide more insight into water flows and help frame future water policies.

So here’s to the rangia. Let’s wish it well in its new role as a scientific asset.