StreamWaders Since its formation, MWS has coordinated volunteers who participate in the StreamWaders program sponsored by Maryland's Department of Natural Resources. Each spring, we head out to wadeable streams to collect invertebrates, such as insect larvae, that live on the stream bottom. The mix of families tell a good deal about the health of our streams.
Ichthyoplankton samplingIchthyplankton (from the Greek for fish wanderer) is a tongue twister referring to the tiny eggs and larvae that wander our streams after fish spawn. Each spring from March through May, MWS nets the eggs for the Maryland Department of Natural Resources, who identify the eggs and compile the results. Our research has found that, over time, usage of the nontidal Mattawoman by spawning River Herring has plummeted, a loss linked to watershed urbanization. Yet the most downstream collection site is holding its own, with egg densities only somewhat below historical levels.
Aythya valisneria, an acknowledgments its fondness for Wild Celery (Vallisneria americana).
SAV also produces oxygen through photosynthesis, so fisheries scientists with Maryland's Department of Natural Resources were concerned when a submerged-sensor reported low levels of dissolved oxygen (DO) after being overgrown by SAV. The Fisheries Service enlisted MWS to explore further. In 2011 and 2014, volunteers paddled the estuary around Smallwood State Park during summer months and measured water quality parameters along transects. The results showed that especially dense beds of SAV could harbor lethally low levels of DO. A possible contributing factor was large amounts of decaying filamentous macro-algae that had been growing on the SAV. The 2011 results were reported in a poster at an annual conference of the Maryland Water Monitoring Council.
Yellow Perch larval survey
During the spring of 2015, MWS assisted the Maryland Department of Natural
Resources by conducting trawl surveys in the estuary to detect the presence or absence of Yellow Perch larvae. Volunteers
deployed a plankton net (left photo) and trawled it for a timed period
at ten sites along the estuary. They washed the contents of the net into
a mason jar (middle photo) and examined the jar for yellow perch larvae
(right-hand photo). Water quality parameters were also recorded, and
selected samples preserved for later analysis. Yellow perch larvae were present in all samples, suggesting a good spawning run and egg viability. But it's not over yet in the gauntlet of survival, for the larvae must find enough tiny zooplankton to eat, and that requires a healthy upstream watershed.
Salts across the watershed: electrical conductivity of streams
The ability of water to conduct electricity is measured through a quantity called the conductance or conductivity. The conductance depends mostly on the amount of various mineral salts in the water. A familiar and relevant example is table salt, or sodium chloride. When salt dissolves in water, sodium and chlorine atoms separate, with the sodium carrying a positive electrical charge and chlorine a negative charge. In these charged states, the atoms are now called "ions." When ions move, they carry current.Preliminary results of the conductance study were reported in a poster at the 2015 annual conference of the Maryland Water Monitoring Council.
Road salt is also usually sodium chloride. In urban areas, road salt washes into streams that can be detected as an elevated conductance. In fact, our studies show that elevated conductance in Mattawoman Creek and its tributaries streams is correlated with road density upstream.