STREAM LIFE

Ahh, stream life in my home mountains, the Sierra Nevada - carnivorous plants, underwater photos, teamwork and sustained attention. I’ve been surveying streams and their tributaries with invertebrate biologists David Herbst, Bruce Medhurst and Ian Bell. We took an astonishing array of measurements from hundred-and-fifty meter sections at each stream, so that insect populations - the bugs who recycle fallen leaves and wood and a primary indicator of ecosystem resilience - can be correlated to changes in water and air temperature, shape of channel, flow velocity, water chemistry and other things. I joined them for four of twenty-four sites they've been monitoring every year, now six years in to a ten year project: a reference curve for environmental change. For the next ten days I have a desk in their lab; they’ll sort out the sampled algae and invertebrates and log numbers into databases while I draw and write, considering how to bring aspects of their work to the average urban citizen.

Ian Bell sorting aquatic insects from stream debris .

Sundew (Drosera species) in the fen alongside upper Nelson Creek. (Fen: a bog on a slope, so the water and nutrients are in motion.)

Ian, Dave and Bruce record channel depth, substrate particle size and note any leaves, algae, etc on the rocks.

Underwater, the darker lumps are Glossoma species, 'tortoiseshell' insects that add rocks to their exoskeletons for disguise and protection. They graze on algae and fungus. Photographed in Nelson Creek at Zumwalt Flat.

One of the bigger predators on the stream bottom (about an inch) - a Stonefly (genus Droneuria) - also prey for fish and other insects. These guys take a year or two to mature so can be vulnerable to annual changes in stream levels and temperatures.

Shadows and constant motion; how do they do it? what is it like to be at home in a stream?