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July 22, 2014
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Healthy waters, healthy fish; Biodiversity is the key

Caddisflies are amazing builders. Seen here on a rock in Equinunk Creek, they have formed a kind of caddisfly “condominium complex.”
Photo by DNR staff


Freshwater makes up about 2.5% of the water on the Earth. This water is recycled through the hydrologic cycle and is the same water that our ancestors used when the dinosaurs roamed the earth. Our bodies are 98% water. All life is intricately connected and dependent on this finite amount of freshwater.

Biodiversity is the variability among living organisms and the ecological complexes of which they are part; this includes diversity within and between species and of ecosystems.

I spent the first 18 years of life surrounded by streams that flowed orange and were (and still are) polluted by anthracite mining that hit its heyday long before my birth. Today, despite community efforts to clean up the legacy left by fossil fuel extraction, many of these streams remain ailing freshwater bodies where there is a dearth of aquatic life. Unlike the anthracite mining region, the waters of the Upper Delaware River Basin abound with abundant freshwater diversity. Residents do not need to travel far to witness this amazing diversity. You can start by exploring a stream riffle. There is such wonder to lift up a few cobble-sized rocks in a cool flowing stream to get a glimpse of the quiet, amazing and active life that flourishes there.

On a visit to a stream, you might see caddisfly houses, where each caddisfly has made her home by meticulously weaving silk with tiny pebbles or leaves—often lined up in tidy rows. These “caddis condos” trap floating food that flows by, and in turn these caddisflies are an important transformer, consuming organic materials and algae, turning them into energy that fish need to survive. This nutrient cycling by caddisflies and other macroinvertebrates helps keep clean waters clean both nearby and downstream. Mayflies (Ephemeroptera); stoneflies (Plecoptera); and caddisflies (Trichoptera)—known as EPT species—make up much of this clean water diversity. These families of macroinvertebrates survive only in clean water and scientists count these insects to determine stream health.

Healthy streams and fish are possible only with healthy land. Many a fisherman says, “Trout grow on trees.” The green buffers and native trees, vegetation and forests that line the banks of our streams, shade and cool the waters and hold the stream banks in place with strong roots. The native plant life drops into the stream to become part of the biomass, feeding the microorganisms that feed the insects that in turn feed the fish.

Because of this diversity, the main stem of the Delaware River has the longest stretch of “Special Protection Waters” in the nation—spanning 197 miles. The Delaware River’s main stem also still flows free—making the Delaware River the largest undammed river east of the Mississippi River. This free-flowing river has sustained ancient freshwater mussels when in other parts of the country these mussels are only distant memories. One in 10 of North America’s freshwater mussel species has gone extinct and 75% of the remaining mussel species are either rare or imperiled. The Delaware River with its minimal silty bottom is home to over 14 endangered or imperiled species like the ancient dwarf wedge mussel and the eastern pearl shell mussel.

An undammed main-stem river supports spawning runs of shad and striped bass. Mussels rely on specific host fishes to support their growing young, called glochidia, as they hitch a ride and develop with help of the American eel, native brook trout, and some of the other 45 species of fish that live in the Upper Delaware River. Freshwater mussels are filter feeders that cleanse a tremendous amount of water for the benefit of us all.

If streams heat up and turn acidic from our burning of fossil fuels and clearing forests for development, which creates impermeable surfaces, increased runoff, and sediment pollution, then freshwater diversity will decline as thresholds are reached and young fish, spawning habitat and insects are smothered by sediment. If we respect the river by protecting its natural floodplain, keep and plant native landscapes, forests and meadows, we will protect ourselves and the river’s diversity at the same time. Take it from someone who was born and raised in the coal region—we want the legacy of good stewardship of our incredible natural biodiversity for the children who will come after us.

[Faith Zerbe, biologist and monitoring director for Delaware Riverkeeper Network, lives in the Lower Delaware River Valley and travels upstream to enjoy the Upper Delaware—to paddle, hike, bird watch, stream watch, snorkel, and swim whenever she has the opportunity. Follow her on Twitter @plecoptera11.]