Fred wades around & across river where the water is 30 cm deep and downstream into the current where it is deeper and the bottom the bottom becomes crunchy underfoot with little Zebra Mussels under the coating of algae. The flat rocks in the stream are covered by the algal coat on their tops, but their sides, especially the upstream side are densely packed with 15-20 mm Zebra Mussels, though there are fewer on the undersides, perhaps because there's not space for them between flat rocks and a coating of sediment in the flat bedrock. In places of moderate current in midsteam the density goes up to a 1 cm separation, or 10000/sq m. Three small Orconectes virilis (Northern Crayfish) skins are caught in algal fluff.
Wading back across the river Fred finds that the areas where not much current flows on both sides is dense with Tadpole Snails, like raisins in raisin bread. This is a different texture from both the fluffy instream algae and the flat bright green surface of the enclosed pools. There's a whole 'nother universe of algae where the cold water of a drain of some sort comes down along the access track - including tar-like wrinkled dark mats of Cyanobacteria - all of this making one wish one had phycological training - but the dominance of the algae all across the river may be a post-Zebra phenomenon.
For a few years after the Zebra Mussels showed up, we'd find fairly fresh native mussel shells of several species, drifted down to the cobbly patch across from where I stand to paint, but today we found only a few very old, eroded shells there. We will continue to keep this as one of our monitoring sites. Maybe someday we'll get somebody to work on the drift samples we have from back before the invasion of Zebra Mussels, and we'll be watching to see whether native mussels can possibly make a comeback. The river bottom ecology must be really changed for Mudpuppies, and there's another project for a low-water summer - to go back to all the spots along the South Nation River where we've found them in past years.