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Tales of Stream Monitoring Fun
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Friends of Accotink Creek and Friends of Lake Accotink Park hold biological stream monitoring workdays four times per year. |
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 Waiting by the examination table as the invertebrates are collected. / Don't put your finger here! |
December 21, 2019 Stream Monitoring: We had a crew of 5 volunteers today, and weather that was light overcast & a chilly 37 degrees. Monitoring today was postponed from the previous Saturday due to high water. Among our group were two young scholars working on AP/IB science projects. We caught a small fish with our first net. Not being an invertebrate, we released it back into the creek. Our net also caught a few submerged beechnuts which a couple volunteers were adventurous enough to eat - tasty! One rare find today was a gilled snail, or rather its empty shell. We caught none of the more common lung snails, so tolerant of low water quality their presence pulls the stream health score down. Our catch included three hellgrammites. One demonstrated the power of jaws of this insect order and their willingness to use them by biting the collection forceps with enough force to tenaciously hang in midair. Accotink Creek achieved its usual numeric stream health score of 4, down in the unacceptable range. Sediment caused by excessive runoff from paved surfaces is the major factor reducing invertebrate populations and impairing the health of streams in our region. See the tabulated results here. Paved surfaces are the nemesis of Accotink Creek's benthic invertebrate population. Take advantage of financial incentives to become part of the solution with Conservation Assistance. |
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September 14, 2019, Stream Monitoring: It was another good day for monitoring, with clear skies and temperatures in the mid-70's. We had a crew of 6 volunteers. The water was clear and the flow level was optimal. Our usual riffles, having shifted somewhat over the past year, had resettled back in the accustomed spot on the creek. We were pleased to see 3 Helgrammites among our catch. These are the largest of the invertebrates we typically catch, but lately have not been caught as frequently as before. We were also pleased and surprised to catch 51 caddisflies, an invertebrate less tolerant of impaired water, and one we have only occasionally seen in the past. Invertebrate abundance was good, too. We only required one net to collect 338 invertebrates. Nonetheless, our catch was dominated by species tolerant of impaired waters. The numeric stream health score for Accotink Creek was in the unacceptable range - 5 on a scale of 0 to 12.
See the tabulated results here.
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 Helgrammite, a bug that bites!. |
 A look at the underside of this leech shows the clutch of orange eggs she is protecting. Probably the Smooth Turtle Leech (Placobdella parasitica), according to iNaturalist, member of a family "remarkable for its parental care" according to Wikipedia |
July 10, 2019 Mussel Rescue: On July 7th the USGS stream gauge on Accotink Creek in Wakefield Park topped out at nearly 6000 cubic feet per second. Anytime the gauge goes over 2000 cfs, freshwater mussels will be pushed out of the streambed and stranded on the gravel bars. After the creek had dropped back to a normal flow level, the mussel rescuers set out to scour the exposed gravel bars downstream from the Lake Accotink dam. This is the only stretch of Accotink Creek in which mussels are able to survive at all, the high volume of shifting sediment having gradually smothered the populations elsewhere. Great Blue Herons and Kingfishers were about as we made our way along the creek. We were also delighted by the sight of small groups of Tiger Swallowtail butterflies gathering to sip essential minerals from the damp sand. We managed to find thirtyeight mussels and return them to safety. They included representatives of all three mussel species found in Accotink Creek, the Eastern Elliptio (Elliptio complanata), Eastern Floater (Pygandon cataracta), and Paper Pondshell (Utterbackia imbecillus. The most unusual sight today was a large leech clinging tightly to the shell of a rescued mussel. Gently peeling back the leech for a better look revealed a natural history lesson, for it proved to be a mother leech, tenaciously protecting the clutch of orange eggs on her underside. We returned the mother-to-be to her position on the mussel as we placed it in safer deep water. See the rest of the mussel rescue photos here. Read about our 2015 freshwater mussel biological survey. Learn more about freshwater mussels.
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June 8, 2019 Stream Monitoring: We enjoyed good conditions for monitoring, with lightly overcast skies and temperatures in the mid-70's. The creek water had a muddy aspect today. This was puzzling, given the dry weather the past few days. Perhaps we may hope this was the result of a localized rain event somewhere upstream, rather than yet another man-made calamity befalling the creek. The abundance of invertebrates was reasonably good, with 219 being collected with two settings of the net. As usual, quality of the catch was another matter, with the most abundant species by far being midges and netspinner caddisflies, two species quite tolerant of impaired waters. It was somewhat encouraging to catch three mayflies and two riffle beetles, species with a preference for more pristine waters.
Accotink Creek achieved its usual stream health score in the mediocre range, a 5 on the scale of 0 to 12, far from the acceptable range. See the tabulated results here.
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 Volunteers explore the creek after monitoring. |
 Volunteers work in Accotink Creek against a snowy background. |
March 9, 2019 Stream Monitoring: We had a crew of 7 volunteers today, and weather that was a bit chilly, overcast, and in the low 40's. There was a dusting of snow left from the previous day. The water was running a bit high from snowmelt, but we were able to carry on. We are still adjusting to the new method of collecting stream invertebrates by scratching the streambed with a rake, rather than by using our feet. We got adequate results with the new method, collecting 213 invertebrates with two nets. Despite the adequate number of invertebrates collected, the quality of the sample was poor. The vast majority were tiny midges and aquatic worms, so small that they wriggled through the net. Too small to be practical to pick up, we had to count them where they lay on the table surface. Accotink Creek received a poor numeric stream health score of 4 on a scale of 0 to twelve. See the tabulated results here. Paved surfaces are the nemesis of Accotink Creek's benthic invertebrate population. All the runoff during rainstorms pours down stormdrains and shoots into the creek, scouring away the banks and smothering stream life in fine sediment. The next big insults to Accotink Creek from the I-66 and Braddock Road widenings will only make things worse. Tell your elected officials "Enough!". Take advantage of financial incentives to become part of the solution with Conservation Assistance.. |
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Accotink Creek Creatures
A lament for aquatic invertebrates penned
GET YOUR BRAIN WET!
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