Aerial and Field SAV Observations

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2012 SAV survey results - general overview

November 1st, 2012 by Robert Orth · No Comments

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

Tags: Aerial Updates

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