… I’m visiting in early January, after a series of storms in November and December lit up the Petaluma River watershed from top to bottom. Yet the line is still clear – just above the seep, the earth is solid and relatively dry. Then, suddenly, clean water flows, trickling through a broad marshy area of rushes and watercress indicating perennial moisture, and then down, down, down the hill toward Petaluma and possibly all the way to its river, seven-and-a-half miles away. … How else is this upper section of Adobe Creek special? It supports a stable population of steelhead, or perhaps rainbow trout. They’re the same species, Oncorhynchus mykiss, but called steelhead if they swim to the ocean for part of their life before returning to spawn, or rainbow trout if they never leave home. One species, two lifestyles.                 —Written by Nate Seltenrich, freelance science journalist who covers plants and animals, human health, climate change, and more for local and national publications.