Aerial and Field SAV Observations

The Maryland Environmental Service (MES) Environmental Staff conducted a vegetation survey, including submerged aquatic vegetation (SAV) of the SCMW on September 21, 2011. The SCMW is located adjacent to the south cell of the CC DMCF, which is located on Kembo Rd., in northern Anne Arundel County on the Patapsco River. Observations were made visually by wading through the wetland due to the shallow water depths. Monitoring of the SAV took place within four quadrants that divide up the wetland evenly, via fixed transects with 1X1 meter square random plots off each transect within each quadrant. The plots were measured out using a tape measure and observations were recorded in a logbook. Due to the difficulty in making actual stem counts as a result of underwater root systems, an estimate of the amount of each SAV was determined as a percent.

The September 2011 survey results showed an increase in diversity and abundance when compared to previous years. SAV species were observed in three out of four quadrants that divide the wetland. Five species were identified and are listed in order of abundance: Eurasian Water Milfoil (invasive species), Curly Pond Weed, Slender Pond Weed, Wild Celery and Duckweed. Eurasian Water Milfoil was observed in all three quadrants, Curly Pond Weed and Wild Celery were observed in quadrants one and three. Slender Pond Weed was observed in quadrants one and two, and Duckweed was only observed in quadrant one.

The average estimated abundance per quadrant for the Eurasian Water Milfoil was 25%, Curly Pond Weed was 4%, Slender Pond Weed was 2%, and Water Celery and Duckweed averaged 1%. The majority of the SAV in the SCMW was observed in quadrant one. The average SAV coverage of the SCMW based on the September 2011 survey results is about 32%.

I worked with local volunteers and agency staff to conduct Severn & Magothy SAV transects once per summer in 2007-2011, with 4 transects per river. The results are summarized in this PDF file. Here are the conclusions from that report; please send me any comments on it, to peter.bergstrom@noaa.gov.

· In both rivers, redhead grass predominated by volume at almost all sites through 2010, and then widgeongrass (Severn) and sago pondweed (Magothy) dominated in 2011.

· Spatial patterns in total volume along the river (based on previous SAV patterns and depth gradients) generally fit with what we expected in the Severn, with more SAV in the middle transects, but usually not in the Magothy.

· There was more total volume in the Severn, as expected from visual observation of the beds, but the differences were small in 2010-2011.

· Changes in total volume from 2007 to 2008 were not consistent; volume declined in the Severn but went up in the Magothy. Volume in both rivers declined in 2009, and stayed near that low level through 2011 in the Severn, with a small increase in the Magothy in 2010.

· The percent of grabs that had any SAV declined in 2008 (Severn) and 2009 (Magothy), then leveled off, suggesting that patchiness increased over time.

Hurricane Irene and Tropical Storm Lee dumped a large amount of water in the Susquehanna watershed, creating a muddy plume that extended down the Chesapeake Bay to the mid-bay islands and persisted for several months.

We were finally able to acquire clear aerial imagery of the flats on 11/08/11. Surprisingly, SAV on the Susquehanna Flats survived pretty well. It does appear that some grass was lost, particularly on the east side of the bed. Here is a look at the upper flats in 2010 and 2011. Slide the central bar left or right to compare the two dates.

Multiple species of SAV growing on the flats form the dark and light features in the middle of the image. Submerged grasses create a dark signature while grasses on the surface shine brightly in the sun. The thin white lines of turbid water coming from the bed appear to be caused by foraging waterfowl.

Left - Susquehanna Flats on 8/30/10, Right - Susquehanna Flats on 11/08/11

Maryland Environmental Service (MES) Environmental Staff conducted SAV surveys along the western side of Hart-Miller Island (HMI) on June 28, 2011 and September 16, 2011.  HMI is located at the mouth of Back River near Hawk Cove in Baltimore County.  Observations were made along two 3 mile transects 20 ft. and 50 ft. off of the western shoreline where water depths are shallow enough to support SAV growth, specifically from the most southern tip of the Hart Island remnant to the southern end of the Miller Island remnant.  The SAV beds were mainly observed by using a modified thatch rake, attached to approximately 15 yards of nylon rope, off of a boat.  Transects are split from southern tip of Hart Island to MES pier, MES pier to Drum Point, Drum Point to just south of the HMI DNR Start Park beach jetty, beach Jetty 1 through 15, and just north of the beach jetties to the southern end of Miller island. 

June 2011 survey results were similar to previous years.  Four species were identified and are listed in order of abundance: wild celery, redhead grass, curly pondweed, and horned pondweed.  Wild celery on average was found in sparse to moderate beds.  Redhead grass and curly pondweed were noted in very sparse beds between Drum Point and the beach jetties.  Horned pondweed was only observed once between Drum Point and the beach jetties.

The average Secchi depth during the June survey was 1.6 ft.  The majority of SAV was observed between Drum Point and just south of the first beach jetty.  Water depth ranged from 2.6 ft. to 6.1 ft.  Overall estimated coverage of SAV in the area surveyed was 20 to 25 %.

September 2011 survey observations showed more SAV abundance than the June survey, and overall percent coverage was higher than previous years.  Eight species were identified and are listed in order of abundance: wild celery, Eurasian watermilfoil, redhead grass, horned pondweed, hydrilla, Elodea, slender pondweed, and coontail.  Wild celery was noted in every transect, however, it was most abundant in moderate to dense beds on the interior and exterior sides of the beach jetties.  Sparse beds of redhead grass, Elodea, slender pondweed, and horned pondweed were observed throughout the survey.  Coontail was only noted once on the exterior side of beach jetty 12.  Eurasian watermilfoil and hydrilla were also recorded in sparse beds throughout the survey. 

Average Secchi depth was 0.63 ft., which is much lower than usual for this area.  It was obvious the water was very turbid throughout the entire survey, which was most likely the result of Hurricane Irene and the tropical depression that followed. Water depth ranged from 1.9 ft. to 6.3 ft.  Overall estimated coverage of SAV in the area surveyed was 45 to 50%, noting the highest percentage on the outer edge of the beach jetties at 70% abundance.

N. Rybicki, Observation from shore August 11, 2011 at Olde Town;  Alexandria, VA just north of Woodrow Wilson Bridge by Ford’s Landing Park.  Canopy cover 100%, 99% Hydrilla, trace Najas minor. walking south it gets deeper and is patchy SAV, 20% Vallisneria, 80% Hydrilla.  [After Irene and much rain, in October, this area was devoid of vegetation according to Justin Reel who kayaked here to make observations of SAV]

Hunting Creek, cove at picnic area north of Belle Haven marina is Canopy cover 100%, 99% Hydrilla, trace Najas minor.

Dyke Marsh on bike path bridge over creek appears to be hydrilla in creek.

Observations from boat October 14, 2011 in Gunston Cove upstream of boat ramp; N 38 degrees 25.637′  and W 77 degrees 10.001′ is Canopy cover 100%, ,  Hydrilla, Najas guadalupensis, and <5% Cerataphyllum demersum.  Hydrilla in flower, and has tubers. Secchi is 81 cm.

Observations from boat October 22, 2011 mouth of Powells Creek, south of Leesylvania Park boat ramp; Canopy cover 100%, ,  Vallisneria, Myriophyllum, Cerataphyllum demersum and trace Hydrilla.  Vallisneria is starting to scenesce, and uproot but has many seed pods.  Secchi is only 40cm today!!

On 10/7/11, Mark Lewandowski (Maryland DNR) and I kayaked in Longs Creek, on the north side of the mouth of Back River (MD), where Mark supervised SAV planting for a number of years through Bay Grasses in Classes. For more details on the site and the planting see my report from our visit last year.

Secchi depths were only 0.35-0.45 m. The upper section was red-brown and looked like tannins and the lower section was green-brown. Some of the plants were on the surface at low tide but some were just below the surface, and thus might not show up in the aerial photos for the SAV survey due to the poor clarity.

We found less SAV in the upper creek than we did last year, although much of what we found last year was milfoil (Ms). This year the beds we found had quite a bit of native species: wild celery (Va), redhead grass (Ppf), and curly pondweed (Pcr). The first two species were planted here and were not found here before planting. We had never found Pcr here before, and it probably got established in the tidal portion from nontidal propagules after the high flow and low salinity this year. We only found Pcr in the upper tidal reaches near the bridge, areas we could not reach last year because the milfoil was so dense. We only found Ppf downstream from the boat ramp, starting past the big rock and extending beyond the mouth of the creek. This is where it was planted and also where we found it last year; we generally found more Ppf than last year, although we also paddled farther.

The 30 photos I took are online in this Picasa web album; first we went upstream and then downstream. As you go through the album note the map on the right, in which the marker that shows about where the photo was taken in the creek moves as you change images. Also notice in the photos that plants in the upper creek had heavier epiphytes & more sediment on them compared to ones in the lower creek.

The map of what we found on 10/7 shows these spatial patterns: Pcr in upper creek only, Va at all of the spots we checked, and Ppf in the lower creek only. Last year we only found Va at 70% of the spots we checked, but with very dense Ms there can be other species hidden underneath. This year we found Ms at 80% of the spots checked vs. all of them last year, showing it declined in area covered. This year we only found coontail (Cd) at one spot vs. 7 spots last year; I would have expected to find more of it this year since it seemed to increase at other low salinity places I checked this year. We noticed duckweed in the shallows in a few spots for the first time this year, shown in some of the photos.

Brooke Landry (MD DNR) and I checked Mill Creek planted SAV (planted in June 2011) on 10/5/11, and there was a little bit left in all 4 exclosures, but only covering 2-5% of each exclosure. All of the plants were short with no sign of flowering, and all were at the deeper edge of the exclosure. All of the the exclosures ended up being a bit shallower than I expected, either due to silting in since June (which definitely happened in exclosure B, the farthest upstream), and/or the tides returning to near normal (as they had on 10/5) after being extra high in June, running 1-2 feet above normal then.

I updated the graph of percent cover I showed in June with the latest data. While not encouraging, there have been many similar small-scale planting projects where we could find no plants within a few weeks or months of planting, so having some plants left in October is a good sign. As you might imagine, a percent cover of 2-5% does not look like much in photos, but here are photos from 10/5 of Area A (3% cover), Area B (2.5% cover, clump of plants hidden by reflection of fence; note silting), Area C (5% cover), and Area D (2% cover). The adjacent wetland planting was doing much better in the upstream section, adjacent to areas B & C, than in the downstream area adjacent to areas A & D, where the only surviving plants were adjacent to the pier, and thus in the left foreground of this photo taken from the pier. We could not tell why survival was different in the two areas.

We last visited the site in late August when there was more SAV, with 5-20% cover–see our report from then. We will return in 2012 to see what comes up, and possibly do more SAV and/or wetland planting. Thanks to all who helped with the project, especially Alexanna Page, a Girl Scout who lives nearby and organized the volunteers who did the planting, staff from MD DNR and the Anne Arundel Community College Environmental Center who helped with setup and planting, and Anne Arundel County Dept. of Public Works for funding it.

Erin Shields, VIMS (Quad 126)

On 9-29 Ken Moore and I surveyed the James, beginning at the mouth of the Chickahominy and moving upriver. We did not find the large bed that was seen from the aerial photos on the mainstem.  We did see some floating coontail, hydrilla and Najas minor, but nothing rooted in that area.  The secchi was 0.4 m along the mainstem, and the salinity was 0 along the entire stretch.  We visited Queens Creek and Herring Creek, both very thick with hydrilla, with some coontail and N. minor mixed in.  The secchi was 0.5 m in the creeks.

I got down to Belmont Bay today at low tide (about 1 hr before lowest tide) and took a couple of pictures from a hill overlooking the tidal Occoquan (picture 1, picture 2). This was quite near the monitor location on this map . SAV beds are quite visible in both pictures and on both sides of the river. I’d estimate the Secchi depth at 1 m or slightly greater. Seems like a good time for the flyover.

R. Christian Jones

Professor, Environmental Science and Policy Director, Potomac Environmental Research and Education Center Deputy Director, Mason Center for Conservation Studies

I surveyed about 2.5 miles of tidal Mattawoman Creek by kayak on 9-17-11, starting at the kayak launch at the end of Mattingly Road and paddling upstream, not quite reaching the bridge across the creek. The trip included high tide so it was only near the end of the trip that SAV was visible at the surface, but I found some almost everywhere I raked in the shallows.

Almost all of the SAV I found was hydrilla (Hv), with milfoil (Ms) and coontail (Cd) mixed with it in a few locations, and spiny naiad (Nm) mixed with it once. In the shallows, almost all of the SAV was mixed with either emergent or floating aquatic vegetation (EAV and FAV), although at the few places where I checked, Hv extended deeper than the EAV/FAV. See the map of the survey with species found labeled.

An interesting thing about the hydrilla beds on this creek is that they have a light signature in aerial photos, as opposed to the more usual dark signature that I’ve seen in photos of other areas. I found some of the densest beds next to a string of dredge islands, from waypoints 432 to 433 on my survey map. Dave Wilcox sent me the section of the 2011 SAV survey photo that shows those islands with the approximate bed outline drawn, which agrees well with what I saw. I saw additional Hv at waypoints 416 & 417 on the other side of the islands, but where SAV is mixed with a lot of EAV/FAV it is hard to identify it in aerial photos, so the aerial survey underestimates the amount of SAV where it is mixed with EAV/FAV.

The SAV I found here was almost exactly the same species that I found on the tidal fresh Patuxent on 6-25-11; see my report here. The main difference was that the SAV was much more abundant and widely distributed on Mattawoman Creek than on the Patuxent. Also, the Hv on Mattawoman Creek (see photo) had smaller leaves and more closely spaced whorls than what I saw on the Patuxent in June.

Another difference was that we saw a lot more birds on Mattawoman Creek than on the Patuxent, probably because it had more fish. On Mattawoman we had one or more great egrets and/or great blue herons in view most of the time, and saw many gulls, terns, and kingfishers, as well as four bald eagles being mobbed by crows and several osprey, all piscivorous birds. The greater number of people fishing that we saw on Mattawoman Creek was also a clue to the fish populations. Most were catching catfish but you can also catch snakeheads there (see link to USDA page about them).