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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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 Monitors set their net in Accotink Creek |
December 11, 2021 Stream Monitoring: Our spell of unseasonably warm weather continued today, with temperatures in the mid-sixties. The gloomy overcast gray skies that prevailed throughout the morning foretold a dismal outcome for our monitoring efforts. Even with the maximum allowed four nets, our total catch of invertebrates was by far the lowest we have ever recorded, a mere 46 individual invertebrates. This is far from the total of 200 required for a valid score. One thing we had no trouble collecting was sediment. Each net was coated with fine particles. It is likely this sediment that is contributing to the low count of invertebrates by suffocating them on the stream bottom that is their home. The was a slightly encouraging positive glimmer in that a large proportion of the catch was caddisflies, an invertebrate less tolerant of impaired water. Accotink Creek achieved a numeric stream health score of 5, 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. |
 HELP! This ever-increasing fine sediment coating the bottom emperils mussels and other creatures in Accotink Creek. |
October 28, 2021 Mussel Rescue: Just past midnight on October 26th the USGS stream gauge on Accotink Creek in Wakefield Park again 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. Three volunteer rescuers answered the "HELP" message scrawled on a rock and searched for stranded mussel once the water receded. We located twelve mussels and returned them to safety in deeper water. This lower than usual number was expected, since the gauge had just briefly touched 2000 cubic feet per second. We found two of the three mussel species living in Accotink Creek, the Eastern Elliptio (Elliptio complanata) and the Eastern Floater (Pygandon cataracta), but not 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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 Three Eastern Elliptios and one not-so-sure. |
September 19, 2021 Mussel Rescue: In the early hours of September 17th the USGS stream gauge on Accotink Creek in Wakefield Park topped out at just over 2000 cubic feet per second, just over the threshold at which freshwater mussels will be pushed out of the streambed and stranded on the gravel bars. A group of four volunteer rescuers assembled by the dam and spent about three hours searching the gravel bars after the creek returned to its usual level. Along the way we found time to forage for ripe Pawpaw fruits, berries of the invasive Autumn Olive, and one single nut of the native American Beech tree. The one-mile stretch downstream from the dam is the only part of Accotink Creek in which mussels are able to survive at all, the high volume of shifting sediment having gradually smothered the populations elsewhere. We located twentytwo mussels and returned them to safety in the deeper parts of the creek. This is not a large number, but each female mussel has the potential to produce hundreds or thousands of progeny over time. We located all of the three mussel species found in Accotink Creek, the Eastern Elliptio (Elliptio complanata), Paper Pondshell (Utterbackia imbecillus, and Eastern Floater (Pygandon cataracta). One mussel was different-looking, of a species that was hard to identify, probably a different-looking Eastern Floater. 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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 Tabulating the results. |
The sky was clear today, as temperatures rose into the low 70's, giving us an ideal day for monitoring. With covid still stubbornly hanging on, all of our 13 volunteers used masks and gloves. We've not seen fish for some time recently during our monitoring outings, whereas we used to spot them with some frequency and even catch them inadvertently in our nets. This phenomenon may not be unrelated to big sediment generating construction projects upstream, such as the I-66 widening project. It may also be a sign of changing climate at larger storms that also produce more rapid streambed erosion. The quantity of invertebrates was not bad. We required two nets to collect the minimum of 200 to attain a valid monitoring score. Quality of the invertebrates was another matter, as our our catch today was dominated by the usual netspinners and worms, yielding a numeric stream health score of 3, well down in the unacceptable range.
See the tabulated results here.
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June 12, 2021 Stream Monitoring: Two days of rain left Accotink Creek running high and muddy. The water level was just low enough, though, to permit us to proceed with monitoring. The day began rather cool and overcast, but later the sun came out and the periodical cicadas began to sing. We were using our new 500 micron nets today. This required some adjustment to the handing differences from our previous coarser nets. A startling and inspiring sight today was a mature bald eagle passing us by as it flew low along the creek. Sadly, no one had a camera at the ready. The species we caught today were overwhelmingly dominated by aquatic worms, the species more tolerant than any other of impaired water. We did catch one solitary mayfly, one of the less tolerant species.
Accotink Creek achieved its usual stream health score in the mediocre range, a 4 on the scale of 0 to 12, far from the acceptable range. See the tabulated results here.
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 Periodical cicada alights upon our net |
 Our catch today included three Hellgammites, a fierce predator. |
March 6, 2021 Stream Monitoring: We had a crew of 6 volunteers today. The weather was favorable, sunny and calm with temperatures rising into the low 40's. The abundance of invertebrates was mediocre today. We required three nets to collect the minimum of 200 invertebrates for a valid score. Two-thirds of our catch today was aquatic worms, a species tolerant of impaired water conditions. One intersting invertebrate in our catch was an adult riffle beetle, an intolerant species we seldom see. Accotink Creek received a poor numeric stream health score of 3 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 sediment-generating activities of the I-66 project are exacerbating the situation. 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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September 11, 2021, Stream Monitoring:
