Aerial and Field SAV Observations

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Magothy SAV, clarity, and DFM update, 7-26 and 7-29-08

July 29th, 2008 by Peter Bergstrom · No Comments

Peter Bergstrom, NOAA Chesapeake Bay Office, 7-29-08

It appears the mahogany tide that has been in the upper Magothy creeks (Cattail and/or Old Man) since 7/5/08 has spread downriver to areas near the SAV beds. My long term monitoring site at Ulmstead/Forked Creek did not have reddish water on 7/18 but it did this morning; the Secchi depth did not drop very much (from 1.0 m on 7/18 to 0.95 m today) but the reddish color probably interferes with seeing SAV. The salinity was 8.4/9.1 ppt using a meter (surface/bottom). The Ppf, Rm & Ppc beds that are usually next to the Ulmstead pier seemed sparser and shallower than usual, extending no more than 40 m from shore, and vert patchy on the upriver side of the pier. See map for locations mentioned.

I also stopped at Stonington, just downriver of Ulmstead Point on the Mainstem (not a long term monitoring site), and the mahogany tide was evident there as well. Secchi depth at the deep edge of the Stonington SAV bed today was only 0.7 m and near the end of the pier it was only 0.8 m. The Ppf, Rm & Ppc beds that are usually dense next to the pier also seemed sparser and shallower than usual (they started where the water was 0.6 m deep and stopped where it was 0.85 m deep, at 1.5 hrs before low tide; see photo). The bed started about 18 m from shore and stooped about 58 m from shore, but (as is also true at Ulmstead) the shallow water continues farther than that, and the bed used to be wider here. The transect I did about 80 m upriver of this pier on 7/22 also showed much less SAV volume than the same transect last year (see 7/22 blog entry).

Both Ulmstead and Stonington had a few small dark false mussels under rocks today, 1-2 per rock, and Ulmstead also had 2 hooked or bent mussels (Ischadium recurvum) on one rock (see photo). This is the farthest downriver I’ve found dark false mussels in the Magothy since 2004, and the first time I’ve found hooked mussels in shallow water there (they are found on most Magothy oyster bars, and I found one in shallow water in College Creek on 7/24, see that blog entry).

I also visited the mouth of Cockey Creek by kayak on 7-26-08. I found there were a few plants remaining from the Va we planted there in 2006 and 2007 (see map). Secchi depth was 0.65 m and salinity was 6 ppt by refractometer. I also found a brick in shallow water on the upriver side of the mouth of Cockey Creek (see the same map) which had more DFM on the bottom than I have seen yet in the Magothy in 2008. see photo.

Tags: SAV Observations · SAV Restoration · Water Quality

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