Aerial and Field SAV Observations

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College Creek SAV and mussel update, 9-29-08

October 1st, 2008 by Peter Bergstrom · No Comments

Peter Bergstrom, NOAA Chesapeake Bay Office, 10/1/08 (Quads 30 & 31)

I visited College Creek on 9-29-08 to do water monitoring and check the redhead grass and dark false mussels that were both locally dense on my last visit on 7-24-08.  I found that the redhead grass was much less dense than it was 2 months ago, and that all of the branches that had dark false mussels in July were now covered with a dense carpet of bryozoans.

In July, redhead grass had some dense clumps at 2 sites near the middle of the creek: off the restored St. Johns College shoreline, where it had been planted by DNR Grasses in Classes students, and across the creek between two coves, just below the Rowe Boulevard bridge, where it was not planted.  Redhead grass was still growing in both places on 9-29 (see map) but it was much shorter, sparser, and muddier than it was in July.  I also found a fairly dense patch of Elodea (common waterweed or Ec-see photo) in Peters Cove, the first record for this creek, and the farthest south it has been reported on Maryland’s lower Western shore to my knowledge.  The presence of Ec here is puzzling for two reasons.  First, several people in kayaks looked in exactly the same spot more than once earlier this year and they did not find it, and second, the salinity has been climbing all summer, from 5.6 ppt on the surface nearby in April to 13.5 ppt on 9-29.  Even if this is E. nuttallii, as it probably is at that salinity, elsewhere it tends to expand when salinity is low and contract when it is high.

The mussels were particulary abundant in July in Peters Cove, just above the Rowe bridge, mainly on the undersides of rocks and branches.  On 9-29 all the branches I checked there were covered with dense bryozoans, both on small and large branches.  The only mussels I saw were dead shells on the bottom.  It may be that the recent unusually high salinity promoted the growth of the bryozoans.  This made me realize that mussels have to contend not only with grazers (mainly ducks, I think), but also competitors for hard surfaces (bryozoans, barnacles, etc.).

Tags: SAV Observations · SAV Restoration

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