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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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June 8, 2024 Stream Monitoring: It was a splendid day for monitoring, with sunny skies and temperatures in the low 70's. Perhaps people were diverted to other activities by the fine weather, for only three volunteers showed up. We were fortunate to catch the full quota of over 200 invertebrates with just one net today, making this the third June in a row we've had that bit of luck. Our catch today was 82% Netspinner caddisflies, a species tolerant of impaired water, and the one we catch most often (though usually no quite so many). We caught a single caddisfly which was not a Netspinner, and a single Riffle beetle larva, just as we did last June. These are species which require better quality water than Accotin Creek can generally offer. One unusual catch was a Mayfly, probably of the genus Caenis. Bulky, squat, and slow moving, unlike the more diminutive and gracile mayfly larvae we have occasionally encountered before, we had to seek more expert guidance to make a positive identification. Accotink Creek achieved a stream health score of 5, outside the acceptable range on the scale of 0 to 12. See the tabulated results here. |
 This invertebrate was first thought to be a mayfly, then a damselfly, then a mayfly again. |
 The ones that got away - mayfly and damselfly larvae were found after the session. |
We had a crew of 20 volunteers today. The weather was favorable, sunny and calm, with temperatures rising to 48 degrees. Accotink Creek was a bit after rain two days before, but otherwise. We set the maximum of 4 nets, but didn't manage to collect the minimum of 200 invertebrates for a valid score. Sometimes the quantity of invertebrates just seems to be a matter of luck. Our catch today was overwhelmingly dominated by aquatic worms, the creature most tolerant of water quality impairment. Accotink Creek received a poor numeric stream health score of 4 on a scale of 0 to twelve, typical of the scores over the years at this site. (The score was unofficial due to the count of invertebrates being under 200.) See the tabulated results here. After we had packed up, one volunteer looking around in the creek made two lucky finds - a mayfly, which we seldom see at this site, and a damselfly, which we have never caught in our nets here.
Paved surfaces are the nemesis of Accotink Creek's benthic invertebrate population. All the runoff during rainstorms pours down storm drains and shoots into the creek, scouring away the banks and smothering stream life in fine sediment. At least we can say the sediment-generating activities of the I-66 project have finally come to a halt. Take advantage of financial incentives to become part of the solution with Conservation Assistance.
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 A row of rescued mussels |
January 13 & 14, 2024 Mussel Rescue: On the evening of January 9th the USGS stream gauge on Accotink Creek in Wakefield Park briefly went over 2000 cubic feet per second, crossing the threshold at which freshwater mussels are pushed out of the streambed and stranded on the gravel bars. Once the water receded, four volunteers set out to search. We located 92 mussels and returned them to safety in deeper water. It was gratifying to see how many were juveniles, indicating the population is healthy enough to continue reproducing. The smallest was 1.5 inches long vs. the largest about 6 inches. We found individuals of each of the three mussel species living in Accotink Creek, the Eastern Elliptio (Elliptio complanata), the Eastern Floater (Pygandon cataracta), and the Paper Pondshell (Utterbackia imbecillus. 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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Accotink Creek Creatures
A lament for aquatic invertebrates penned
GET YOUR BRAIN WET!
Plan now to volunteer again with others to preserve our oceans and waterways Back to our main Monitoring Page
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