Aerial and Field SAV Observations

Ken Schultz (Quad 108)
I spent some time exploring Island Bay. It was turbid, and I could not see the grass, even in 2 feet of water, but I could definitley read large areas of it on my sonar throughout the area. My GPS/sonar has a good map of that bay so I was able to get close to -75.774480, 37.797755 and -75.772933, 37.794640 Decimal Degrees. Both were 4 to 4.5 feet deep (that was midway through the incoming tide, though there was little water movement as the wind was pushing the water out of the bay) and loaded with grass. I dropped the anchor and came up only with widgeon grass in both places. Not sure if there’s any eelgrass, but all I saw was widgeon; it had many seed pods in it.

Widgeon grass, Island Bay

Nancy Rybicki, USGS (Quad 039)
I was just in the Potomac River at Belmont Bay, near Kanes Creek, observing SAV at a very low tide (4/21/13). I walked from near the Mason Neck visitor center to Kane’s creek. I was walking in the shallow water and identified 7 species of SAV that were growing at a density of ~ 10% cover maybe 60 m from shore. I identified a Potamogeton, maybe P. pusillus, Zannichellia, Vallisneria, Hydrilla, Myriophyllum, Ceratophyllum, and a floating Heteranthera. The warm spell April 9th must have triggered the Val and hydrilla tubers to germinate, and all species of the plants were all tiny (~5cm long) , it was a very sandy bottom and the tubers were still attached via shallow rhizomes extending 3 to 7 cm into the sand. The floating Heteranthera dubia was just greening up and still attached to last years dead, black stems. There were a dozen Canadian Geese resting nearby and I found a goose egg on the beach. The huge exotic snails and freshwater mussels are plentiful here.

I also walked from the Mason Neck visitor center to Sandy Pt. I passed the Chesapeake Bay Foundation’s Vallisneria restoration site in Belmont Bay, not far from Sandy Pt. The recent winds had destroyed the exclosure they had placed around the recently planted seedlings, and no seedlings were visible.
There must be a Myriophyllum bed nearby. I don’t know where the Myriophyllum bed was, I didn’t observe it. Many ~1 ft length fragments of healthy, bright green, Myriophyllum were wrapped up in the Chesapeake Bay Foundation’s exclosure (plastic mesh, mesh now detached from the ring of pvc poles). Myriophyllum fragments were all along the shoreline in Belmont Bay.

Terry Willis (Quad 026)

We had a good SAV year in the lower Chester last year (2012), with growth in some places where it had only been sparse in recent years.  The waterfowl are liking it.  Biggest thing was resurgence of elodea.  Note that despite local dry conditions salinity remained on the moderate side even into August (I have seen 16+ppt in really dry years).  I would guess much water from elsewhere must have been coming over Conowingo.  Secchi depths in the summer still mostly .5-.6m except in the midst of the beds, where it is common to see 1m or more.  It is amazing how much growth can occur under the proper conditions in a very short time, must be many fold more than what planting efforts can accomplish in the same interval.

Maryland Environmental Service (MES) Environmental Staff conducted SAV surveys along the western side of Hart-Miller Island (HMI) on June 21 and September 25, 2012.  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 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 2012 survey results were similar to previous years.  Five SAV species were identified and are listed in order of abundance: wild celery, redhead grass, curly pondweed, Eurasian watermilfoil, 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. Eurasian watermilfoil and horned pondweed were noted in very sparse beds between the jetties.   Coontail was also noted in this area. 

The average Secchi depth during the June survey was 1.7 ft. The majority of SAV was observed between the beach jetties.  Water depth ranged from 2.4 ft. to 5.8 ft.  Overall estimated coverage of SAV in the area surveyed was 40 to 45 %.               

September 2012 survey observations showed less SAV abundance than the June survey, and overall percent coverage was lower than previous years.  Four species were identified and are listed in order of abundance:  wild celery, redhead grass, Eurasian watermilfoil, and curly pondweed.  Most of the SAV beds were noted in between the jetties and the beach and from the jetties to Drum point.   

Average Secchi depth during the September SAV survey was 1.5 ft.  Water depth ranged from 2.1 ft. to 6.3 ft.  Overall estimated coverage of SAV in the area surveyed was 15 to 20%, noting the highest percentage between the beach jetties at 30% abundance.

Nov. 1, 2012

Greetings SAV friends and colleagues!  It looks like we dodged a bullet with Sandy down here at VIMS.  We got a bunch of rain but most of us kept power throughout the storm.  I hope you made out okay.  Thankfully we completed the aerial photography of the entire Bay for the 2012 SAV survey before this storm hit.  We will be able to produce a baywide SAV coverage number for 2012.

Without going into a lot of detail river by river (that will come later when we finish the baywide mapping), here are a number of highlights for the 2012 survey (both good and bad):

The large SAV bed on the Susquehanna Flats made a good comeback in 2012 and appears quite robust in the photos, although the total area will definitely be less than what we noted a couple years ago.  On the downside, SAV was pretty much absent in the nearby Elk, Bohemia and Sassafras rivers.

SAV in the western MD tribs was highly variable, with abundant beds in the Severn River but pretty much gone in the Magothy River.

Widgeongrass populations once again exhibited some wild and enigmatic fluctuations baywide.  It was abundant in the Mobjack Bay area in the lower bay.  It re-appeared in the mid-Potomac in St. Clements Bay where we had not seen it since 2005.  It was present but down quite a bit in the Choptank, but just north in Eastern Bay, MD, we did not see any. Nor did we see much in the Fleets Bay and Dameron Marsh area in Virginia waters.  And in other areas it seemed to hold its own, e.g. the Honga River.

Eelgrass, in general, seems to be making a very slow recovery from the 2010 dieback, but in a few places where VIMS conducts some transects, eelgrass was either absent or very low in abundance. We are closely studying the long-term decline in this species that has been punctuated by dieback events in 2005 and 2010, coupled with moderate recovery.

An interesting story continues to develop in the mainstem tidal fresh areas of the James River where we have once again seen more fringing beds than the year before.  Most of what was noted this year is N. minor.

Hurricane Irene and Tropical Storm Lee prevented our efforts to map the upper Potomac in 2011. The 2012 imagery reveals a significant decline in that area that is probably at least partly due to the turbidity caused by those storm events

SAV in the MD Coastal Bays is continuing its downward trend over the last decade; however, just south in the VA coastal bays, eelgrass continues to do very well and is increasing in coverage.

So, in summary, 2012 had some good news and not so good news.  The hot spots for SAV growth in 2012 are the Susquehanna Flats, mid-bay islands from Tangier to Bloodsworth, the Mobjack Bay and Poquoson Flats.

We are still processing all the 2012 imagery and will be publishing the imagery for each area on the SAV interactive map (http://wwww.vims.edu/bio/sav/maps.html) as soon as it is available. We also publish SAV maps for each USGS quadrangle area as they are photo-interpreted. These are available at http://www.vims.edu/bio/sav/sav12/quadindex.html.  We remain on target to have baywide and segment SAV numbers by March 1.

Finally, with regard to any possible effects of Hurricane Sandy on SAV, we will not know anything definitely until the 2013 survey.  However, our gut feeling is that the storm effects on SAV will be minimal.  The storm occurred pretty late, well after most species have completed their growth cycle, and wind effects may only be in those areas that were exposed to the strong winds out of the NE and NW. The Conowingo flows right now, while high, may not be too much of an issue for SAV in that region. These high flows are also two months later, and less, than what we saw for Irene and Lee.  The last good satellite photo on Oct. 22 still showed some SAV there.  So now we wait.

Cheers
JJ

Tom Harten, CHESPAX (Quad 041)
We’ve only taken a few student groups out this Fall for our SAV survey program, but we have been struck by the lack of SAV in much of the creek. Many areas that typically supported fairly dense beds in years past are literally devoid of any growth at all. The amounts that we’re finding now would be more typical for our late October or early November surveys. Most of the plants are dead or totally covered in epiphytes.

Also interesting are the complete lack of Hydrilla “rafts” that we’d typically see floating down the Patuxent River in the late summer and early fall. We wondered whether the extreme heat of the summer or a salinity spike might have caused an early die out of the SAV.

The upper sections of the creek are the few spots that are seeing at least a little SAV, but the plants look pretty worn out for this point in the season. The turbidity in the creek is extremely poor, maybe the worst we’ve seen in our Fall counts in 18 years of observations.

Lee Karrh (Quad 010)
Our long-term vegetated site on the Elk (just upstream of the confluence of the C&D, on the east side of the river) was totally unvegetated. The sediment surface was a few centimeters thick of a fine silt, hinting at storm effects. Clarity was terrible, maybe 30cm. On previous trips out to the Elk, we did see ok densities of Val in Rogues Harbor and it appears to still be there. Another bonus, the pound net that was first installed last year is now gone.

We also sampled Veasy Cove on the Bohemia and there were dense, mixed beds (mostly Val and Milfoil, but also 7 other species). The Val had the most dense flowers and seed pods I ever recall seeing. I wonder if that is a stress response. Clarity was slightly better ~75cm.

Terry Willis (Quad 026)
I have been to many of the usual places, and SAV acreage appears way up this year. Hail Creek, Durding Creek, Shipyard Creek, Bogles Cove, Church Creek and Frying Pan Cove all have good coverage, some in places (right bank of Hail Creek going up) not usually seen to have SAV. Shipyard Creek is almost covered from just inside the mouth to the head of the creek, bank to bank in some places. Shipyard also has had sketchy growth in the past. Right side of Church Creek has growth out to 75-100 feet in most places. Most of the growth in all these spots is a mixture of primarily two species-wigeon grass and elodea, with lessor amounts of redhead grass. There are also some patches of millfoil and some scattered sago pondweed. Also remnants of horned pondweed in the shallows at the creek heads. In spite of the early drought, salinities were mostly below 10 ppt until July. Secchi depths as usual .5 m or less except for in the vicinity of the beds, where in some places it is better than 1 m.

My report on the results of the transect surveys is attached as a PDF. Comments welcome.

Here are the Conclusions from it:

Conclusions:

• There was more total SAV volume in the Severn than in the Magothy in all six years, as expected from visual observation of the beds and the VIMS SAV survey, but the differences were small in 2010-2011, when both rivers had fairly low volumes.
• Volume in both rivers declined from 2008 to 2009, and stayed near that low level through 2011 in the Severn, with a small increase in the Magothy in 2010 followed by declines in 2011-2012. Severn volume had a huge increase in 2012 to its highest volume ever, due to moving the Asquith transect, but is 2012 volume would have more than doubled from 2011 even if we had not moved it.
• In both rivers, redhead grass predominated by volume at almost all sites through 2010, and then declined. Widgeongrass (Severn) and sago pondweed (Magothy) dominated in 2011. Sago pondweed predominated in the Severn in 2012 (with 74% of total volume) but that was mainly because we moved the Asquith transect to sample a dense sago pondweed bed. The Magothy had roughly equal amounts of widgeongrass and sago pondweed in 2012, and only one piece of redhead grass found.
• The decline in redhead grass over time may be related to its leaf structure, which makes it more susceptible to sediment accumulation on its leaves, reducing light availability.
• 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.
• The percent of grabs that had any SAV declined in 2009 in both rivers, and then leveled off, suggesting that patchiness increased over time.

Cassie Gurbisz, UMCES
The plants have grown a lot since the last time we were there (early/mid July) . Not only were they abundant in the shallow northeast portion of the bed, but also near the DNR CONMON sensor and in dense patches on the eastern side (Heteranthera was growing to the surface and starting to flower; val was also abundant; hydrilla was abundant towards the northeastern area). The southern portion of the flats, where I believe there had been grass in previous years, is mostly devoid of plants. Turbidity was still relatively high in western and southern portions of the flats but very low in the northeast area.