Saturday, July 31, 2010
The Pine Grove covered bridge is immediately downstream from the Chester County water plant and sets the tone for this place where old and new seem to meet and blend. But even part of the old is a facade. The covered bridge was rebuilt atop steel beams. I slid into the water at the downstream end of a large pool just around the first bend downstream from the bridge.
Corixids, which are flying insects with the ability to swim, feed off the bacterial algal ooze that accumulates on the bottom of the slow moving backwater. I have never seen these animals in the wild, only in swimming pools, and their mottled tan wing covers are much more attractive here.
The rocks in the main flow are all covered in sponges infused with sand and sediment so they aren’t so obvious until they are touched. I was transfixed by the concept of freshwater sponges since I studied streams in high school. My teachers told me about a patch of them in a local stream, but I was never able to locate them. When I think of sponges I think of marine systems, and this was part of my amazement. Now, 30 years later, I finally find some freshwater sponges, but they are nothing like the animal I had pictured: upright typical sponge form. Instead, they are encrusting and dirty with silt and sand. Ancient organisms covered by the new problems of sedimentation and increased scouring flows.
A young eel hunted between rocks on the bottom unaware of my presence and a small northern water snake swam over my left shoulder and under my right arm as I tried to snap a picture of the eel.
A Chinese mystery snail lay upside down and was encrusted into the bottom by sponges. These invasive snails have the ability to filter feed, and I wonder if that is what this one was doing. It found a safe place in the stream bed, was protected by encrusting sponge and filter fed for food. New biology, in the form of a recent addition to our aquatic systems, the Chinese mystery snail, and old biology in the form of freshwater sponge meet and become intimately associated here, like the covered bridge and water treatment plant.
Friday, July 23, 2010
Three Mile Island scared the crap out of me when I was 12. It came close to melting down and I remember being very concerned for my aunt, who lived in a nearby town that would have been eliminated had the ultimate disaster happened. I went to see the movie the China Syndrome not long after and that cemented my hate for nuclear power that lasted through young adulthood. I have mellowed a bit with age, and now recognize that the culprits in all energy related calamities are us. We are the ones that create the demand, and demand cheap energy. Not the oil, coal or nuclear power companies. I have learned that when I’m wagging my finger at someone else, three are pointing back at me.
So today I slid into the water upstream of the Three Mile Island nuclear power plant at the canal lock recreation area. The lock haven dam is just down stream from that, and backs up the Susquehanna to supply cooling water to Three Mile Island, and potential energy to the York Haven dam and powerhouse. Just about anywhere I have snorkeled on this river is affected by energy production in some way, and the water from the lower river is used by hydro, nuclear and coal fired plants to give us the energy we need to maintain our lifestyles.
The river here is typical Susquehanna, big expansive shallow water, with numerous rock outcrops. An assortment of invasive shells, an invasive jambalaya of sorts; mystery snails, corbicula, and rusty crayfish carapaces, were piled in a dry eddy.
I slipped into the water and 5 crayfish rocketed in different directions. They are everywhere, and I can’t make any move without causing one to shoot off out of sight. I am fairly certain these are the invasive rusty crayfish, with large claws and rust colored patches on the sides of their carapaces. They are so abundant, they must surely have an affect on the ecology here, especially on the benthos, but benthic fish, like tessellated darters, don’t seem to be affected as they appear to be almost as abundant. Virginia river snails are also common and they leave grazed patches and trails where they have eaten the slick biofilm on the smoothed slabs of bedrock, but they may be affected. Maybe Virginia river snails are less abundant here than other places like the mouth of the Octoraro because of the crayfish. There are lots of dead shells of another invasive, Chinese mystery snail, but where are the live animals? Are they hunkered down in the substrate?
This is used water, used by power companies and industry, farmers, city dwellers and suburbanites. But then any river in North America is heavily used. Invasives, like many of these crayfish, Chinese mystery snails, and now for the Susquehanna, zebra mussels, are one of the leading causes of globally declining freshwater biodiversity. And I wonder what the biggest danger is, or will all these threats work in synergy to finally destroy whatever is left of our freshwater ecosystems? I’m sure that the system I observed in a few feet of water today little resembles the ecosystem that was here pre European settlement. So while it may not be pristine, it is still amazing.
Sunday, July 11, 2010
I used to avoid the larger eddies, those areas of sluggish water behind rocks and shoreline aberrations. The slower moving water created by the upstream obstruction allows the finest silt particles to settle to the bottom and expanses of barren mud-covered flats extend downstream. I always thought of muddy eddies as lifeless, and I usually created chocolate milk water conditions by accidentally stirring the fine bottom before I could really see who was living in these areas.
I skimmed over one of these eddies on my way to what I thought was the more interesting habitat of a cobbly riffle when I came upon a line in the mud that led 5 feet or so to a Virginia river snail slowly but surely making its way upstream. In the moment I paused to admire the snail, other life became apparent. Tiny squiggles of new fish schooled in a small hazy cloud. Black smudges of other kinds of fry swam towards me to investigate. Comma mark toad poles squiggled along the bottom. The importance of this perceived lifeless barren became apparent: this is a nursery for the stream, and suddenly, this barren wasn’t so barren.
Sedimentation results in the loss of habitat and is one of the leading causes of stream degradation. The inputs of soil we send to our streams through ground disturbing activities like farming and construction, and scouring runoff that comes from hard surfaces like driveways and roads needs to be controlled. But small amounts of erosion and resulting sedimentation are natural processes, and the fine muds that form the bottom of these eddies are important in the continuum of stream habitats, from quiet muddy eddies, to violent bouldery rapids. Life has evolved and developed to nestle in a particular spot on the spectrum, and all habitats are essential. Even the muddy ones.