River Grasses on the Potomac

We went canoeing along the Potomac last week. After putting in to the re-watered C&O Canal at the Pennyfield Lock a few miles west of tony town of Potomac Maryland, we paddled for a couple of miles up the shady canal to Violettes Lock. It was a beautiful day in the low 80's and we spotted blue herons, turtle, and a bold little green heron. Once at Violettes, we ported the canoe up and over to the Potomac river itself to complete one of the few places you can do a canoe loop trail.

The water was on the low side of runnable, and perhaps we should have crossed over to the Virginia side and taken the channel of the old Pawtowmack Canal, but we went down the main channel of the river over the rocky slope of the old dam that was built here to divert water into the C&O. Below this we zig-zagged through the myriad of channels and chutes between the boulders that mark this part of the river.

The most memorable part of the trip were the river grasses, both in the canal and on the river. I'm used to canoeing on the Patuxent which today is a turbid and choked with sediment. The water on this stretch of the Potomac was clear and the river grasses had recovered magnificently. Near Violettes Lock there were a few patches heavy in hydrilla but mostly we saw vast underwater meadows of water stargrass. These dense clusters of meter-long braids of grass were topped with delightful little yellow flowers floating just on top of the water. Amongst the grasses, we spied all varieties of fish including bass, catfish, and blue gills. The water clarity was excellent; it made me think of bringing my snorkel gear.

Reading a report summary after our trip, I found a study that showed how the river grasses in the Potomac have been recovering since efforts to reduce the nitrogen and phosphorus pollution levels have progressed. This study gave me hope. A few weeks ago on the Patuxent, in the North Marsh just above the Rt 4 Hills Bridge, I came across channels clogged with hydrilla. In my years of canoeing this area I had never seen this before.

Since hydrilla is not native to the Chesapeake I was alarmed and upset that the mass of vegetation was blocking my navigation to the inner reaches of the marsh. However my reading now indicate that this may not be such a bad thing. It seems that hydrilla on the Potomac was a pathfinder plant for the river's recovery. This hardy weed was the first plant to establish itself as the water quality began to improve. Once in place, this fast growing plant helped to further filter the river, both physically and chemically. The hyrdrilla has also proved a useful food source for wintering waterfowl. Other native sub-aquatic vegetation, like the fields of stargrass we observed, soon followed the hydrilla.

We can hope, and by continuing our efforts to reduce the nitrogen and phosphorus run-off into the river, we can enable the Patuxent to finally start to see improved water clarity and quality too. Perhaps we can soon see meadows of stargrasses in the Patuxent.