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December 14, 2017
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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

By Faith Zerbe

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.