Aerial and Field SAV Observations

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Mill Creek, Magothy River, SAV planted in dredged “shelves”

August 23rd, 2011 by Peter Bergstrom · No Comments

Mill Creek on Magothy River had a 3 million gallon sewage spill in its lower nontidal reaches in December 2005, that added a large amount of sediment to its upper tidal reaches. Its uppermost tidal reaches were dredged last winter (2010-2011) to remove some of that sediment and restore the previous boat access. There were “SAV shelves” dredged to -0.5 ft MLLW next to the channel that were designed for SAV planting, with even shallower shelves next to those for wetland planting. The wetland planting was done by contractors, and I worked with Mark Lewandowski and Brooke Landry , MD DNR, local girl scouts, and the Magothy River Association (MRA) to organize the volunteers who grew and planted wild celery in the shelves. Photos from the 2nd planting in late June are in this Picasa web album.

We had tried wild celery planting in the Magothy before without success, but those attempts were on the mainstem; we had never tried it this far up a creek. Project costs were covered by the MRA and MD DNR (which already had SAV growing gear) and the Anne Arundel County Dept. of Public Works. Steve Ailstock, Mike Norman, and other staff from Anne Arundel Community College’s Environmental Center provided field support and will do additional planting later.

We set up 4 exclosures on SAV shelves on the sunny side of the creek, next to a pier where we had permission for overland access (see map; letters were assigned in the order we planted them, A-D). This allowed us to plant there and check the plants by boat or by land. The other shore also had SAV shelves but they are in the shade of overhanging trees most of the day.

Mark and Brooke brought the plants grown in schools through Bay Grasses in Classes on June 8 and they, AACC staff, and Alex Page planted them. The students who grew them were not allowed to plant them since we could not work out overland access for them. The plants grown by Girl Scouts and MRA volunteers were planted on 6/24-25 by community volunteers, supervised by a Girl Scout, Alexanna Page, as her Gold project, with assistance from me, Brooke & Mark. The mucky sediments made planting challenging; in some areas the planters had to kneel to keep from sinking in too far, and then it was hard to move once they finished planting a row. Three of the exclosures got about 80 cat litter pans of wild celery each, while the fourth and last one (D) only got 27 since that was all we had left that day (6/25).

Mark and I checked the plants yesterday (on 8/22), about 2 months after the second planting, and found the lowest tide we had ever seen, so it was easy to check survival of the SAV. All 4 exclosures (A-D, in the order we planted them) had some wild celery left, with between 5-20% cover. The Secchi depths (measured weekly at the same pier we used for access) have all been low since we planted (maximum 0.45 m, several weeks had only 0.2 m, plants need about 1 m to survive) so I expected to find a lot less growth than we did in July, and was pleasantly surprised to find some increases. The water was very murky and the tide was higher during our July visit, making it harder to see the plants then, even with a view scope.

All of the exclosures had 60% cover when planted except D, the last one planted on 6/25, had only 40% since we did not have enough plants to fill it up.  This graph shows the percent cover over time for each of the 4 areas. Mark & I plant to visit once more this year, probably in Sept.

The photos of the plants I took on 8/22 are online at this link. Note that one of the exclosures (B, the farthest upstream) had sediment deposition after we planted there so that only the deep edge remained deep enough to support SAV. This is one of the risks of using very shallow shelves for SAV planting, especially where they are close to the freshwater inflow. The photos also show the adjacent wetland plants, about half of which appeared to be gone, presumably from grazing: the remaining ones appear to be grazed, and the bare areas had grazed plants when we visited in mid-July.

Tags: SAV Observations · SAV Restoration · Water Quality

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