Tales of Stream Monitoring Fun
Lake Accotink Park
Friends of Lake Accotink Park
Friends of Accotink Creek

Friends of Accotink Creek and Friends of Lake Accotink Park hold biological stream monitoring workdays four times per year.
Thanks to all the volunteers who have joined us for this important data-collecting activity!

Our December 14, 2013 Stream monitoring:

Foul weather threatened our endeavor, with a forecast of mixed snow and rain, but our five volunteers stayed dry under a cloudy sky. The day was a chilly 33 degrees. A scum of ice covered the lake and snow still lay upon the ground, but Accotink Creek was ice-free.

We always come to our monitoring sessions with low expectations for the health and biodiversity of Accotink Creek, and again we achieved those low expectations. Fully eighty-seven percent of our catch was aquatic worms, a species tolerant of poor habitat quality. Small quantities of a few other tolerant species brought our total up to 226 invertebrates, caught in three nets.

As usual, the stream health scoring formula gave Accotink Creek an "unacceptable" rating of 4 on a scale of 12.

October 15, 2013 Mussel Rescue:

Flooding caused by days of steady rains had washed mussels up onto the bank, leaving them exposed to dehydration and predators. A streamside rescue mission below the dam, the only part of Accotink Creek where mussels are now found, located twelve living mussels, ten of them stranded above the waterline or in shrinking shallow pools. Returning them to deeper water gave them the chance to complete their long life spans of up to 80 years.

Sadly, the live mussels rescued were far outnumbered by by the empty shells of those recently deceased after becoming stranded and devoured by hungry scavengers. The Eastern Elliptio Eliptio complanata is the only mussel remaining in Accotink Creek, in a restricted range and much diminished numbers.

See the rest of the mussel portraits here.    Learn more about freshwater mussels.

Our September 14, 2013 Stream monitoring:

We had another clear and sunny day, with mild temperatures, ideal for monitoring. The water had receded to near average levels after heavy rains two days before. Thirteen volunteers were on hand to administer the biological health checkup of Accotink Creek.

The hellgrammites were out in force, and we caught a total of seven of them. These fierce predators need to be kept separate from all other species and from each other in the counting trays, lest they commit mayhem.

With our good turnout of volunteers, the human monitors nearly outnumbered the invertebrates. Even with the maximum of four nets we caught only another disappointing catch of 189 invertebrates, well below the quota of 200. A surprizingly high catch of 75 Asiatic clams saved us from an even lower total. Asiatic clams are an invasive alien species, but none of the monitors acted on the suggestion that they should be taken home and made into chowder.

We did have two unusual species among our catch - a never-before-seen damselfly larva and one mystery bug later dertermined to be a crwaling water beetle of the Halipidae family. Also unusual was the large amount of "gunk" caught in our nets, which we took to be algae of some kind and surely not a good thing for the creek.

As usual, the stream health scoring formula gave Accotink Creek an "unacceptable" rating of 4 on a scale of 12.

Our June 12, 2013 stream Monitoring:

We had scheduled monitoring for June 8th, but the last remnants of tropical storm Andrea had passed through a few days before, leaving Accotink Creek just a bit too high for monitoring. We rescheduled for June 12th, taking advantage of the late daylight for an after work evening session.

The water was still running a bit high and muddy, but conditions were otherwise good for monitoring with clear skies and mild warm weather. The crew was thin, though, with only four of us on hand.

Our catch was disappointing, with only six species found, 100% of them being species tolerant of poor water quality. We required four nets to catch the target number of 200 invertebrates. Urban runoff, with its feast-or-famine regime of high and low water, fluctuating temperatures, and excess sediment, continues to impair the Accotink Creek habitat.

Our March 9, 2013 stream monitoring:

We had a clear and sunny day, with mild temperatures, ideal for monitoring. The water was a bit high due to melting from a snowfall the previous Wednesday, but not so high as to interfere with monitoring. Ten persons joined together to check in on Accotink invertebrates.

Two vertebrates tried to join the act in the form of two small fish caught in one of our nets. After their photo opportunity, we quickly got them back in the water. Tessellated Darter Etheostoma olmstedi and Blacknose Dace Rhinichthys atratulus are our inexpert species identifications.

Despite the good conditons for the monitors, it seems things were not going so well for the invertebrates. We set the maximum number of nets - four - but caught only 121 invertebrates, well below the quota of 200. The variety was also quite low, with 86% of the total comprised of aquatic worms. Aquatic worms are a species tolerant of stream impairment, and Accotink Creek is certainly in the category of impaired streams.

As usual, the stream health scoring formula gave Accotink Creek an "unacceptable" rating of 4 on a scale of 12. Sediment from streambank erosion is the main stressor on aquatic life here and excess runoff from stormdrains is the cause.

A mussel search, January 11, 2013:

Having not spotted any freshwater mussels as we usually do during our last few stream monitoring sessions, I took an opportunity to walk the part of the stream where mussels are found to see if any were still there. Mussels must once have been much more common along Accotink Creek, but now are found only in limited numbers and only in the area downstream from the dam as far as the first trail bridge.

The water was running clear, but the overcast weather made spotting the mussels among the stones of the bottom rather difficult. It was good to see, though, that mussels are still present. I located ten living individuals, including one juvenile. As usual, the empty shells of deceased mussels, sadly, far outnumbered the living. The sole species typically found in Accotink Creek is the Eastern Elliptio Eliptio complanata.

Sediment in streams tends to smother mussels and is certainly the major cause of their decline in Accotink Creek. Recent major construction projects, including the I-495 Express Lanes and repairs to the dam, have released large quantities of sediment that do not help.    P. Latasa

See the rest of the mussel portraits here.    Learn more about freshwater mussels.

Our December 8, 2012 stream monitoring:

On December 8th, 2012, the baton was passed to a new team of stream monitors at the Lake Accotink Park monitoring site. Friends of Lake Accotink Park and Friends of Accotink Creek joined forces to maintain the continuity of data collection at this long-established monitoring location.

The weather was fine for the purpose, cool and overcast. The recent draining of Lake Accotink left a fresh coating of sediment on the stream bottom. Sediment is the main stressor impairing the populations of benthic invertebrates, so this latest assault surely did no good. The fresh fine sediment was evident as a coating on our nets.

We captured two scuds, a type of tiny shrimp-like crustacean, and a rather unusual find at this location. Also somewhat unusual were the three flatworms collected. They glide along the bottom seemingly without effort, while their two white eyes stare straight up at the observer.

The bulk of the catch this time was many aquatic worms, a species tolerant of poor habitat conditions. After all the invertebrates were counted and cataloged, the stream health scoring formula gave Accotink Creek a rating of 4 on a scale of 12. This is a typical score here, and puts Accotink Creek in its usual unacceptable score range. Sedimentation needs to be brought under control before we can hope for much improvement.

Mussel Rescue, September 10, 2011:

It seems we forgot to record the information about this mussel rescue at the time it happened, but here is a link to the pictures of the mussels, and several good-sized fish we rescued.

See the rest of the mussel portraits here.

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