Aerial and Field SAV Observations

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07/19/10 An SAV Update

July 19th, 2010 by Robert Orth · No Comments

Greetings SAV friends and colleagues!  I hope you are all having a good and productive summer.  However, unlike last year when we were all talking about how wonderfully cool June was, we just experienced the complete opposite this year – it was one heck of a June and I can’t remember one when it was so hot and dry!  The big news is out that the first six months of this year were the warmest on record!

We got off to a great start with the aerial monitoring and were able to acquire excellent photography between May 20 and 27 of the western side of the lower bay up to the south shore of the lower Potomac River and the eastern shore all the way to the lower Honga.  We were also able to successfully obtain photography of the coastal bays in Maryland and Virginia including the lower lagoons where the eelgrass is coming back rapidly as a result of the restoration efforts there. This photography is complimented by SAV observations along a series of transects established in the lower bay following the 2005 eelgrass dieback as well as biomonitoring station transects adjacent to the Goodwin Islands NERRS site.  MD DNR folks have also just established transects in a number of locations throughout the bay complimenting the VIMS work and ongoing work by UMD people in Chincoteague Bay.  The transect data provides detailed species information that is exceedingly helpful for the SAV aerial monitoring project.

Our staff is processing the imagery and will be adding it to the interactive map (http://www.vims.edu/bio/sav/maps) as it becomes available.

The overall picture for SAV looks good in the regions we have acquired imagery so far. The imagery and transect data show that the SAV beds are similar to what we saw in 2009 and perhaps larger in some areas. The ‘hot’ spots for SAV along the western shore remain the Back River, Poquoson Flats, mouth of the York River, Mobjack Bay, and the area below Reedville. Our transect off Dameron Marsh recorded eelgrass in slightly over 2 m of water (at MLW). Pretty impressive given the overall eelgrass picture in the bay!  In the Rappahannock River, widgeongrass appears to be having another good year (so far). SAV is present in the same areas that we noted widgeongrass in 2009 for the first time in a few years.

Along the eastern shore bayside, SAV beds were looking pretty decent at the mouths of most of the creeks up to Pocomoke Sound, Crisfield and the Big Annemessex Rivers, Tangier and Smith Islands, and Southmarsh and Bloodsworth Islands.

SAV in the coastal bays also looks pretty decent this year from what the photos show from the May flyover. All the areas behind Assateague Island noted in 2009 look good. The SAV beds at our restoration sites along the southern coastal lagoons are continuing to expand at a very rapid rate.

We should begin to have a better idea of how the 2010 numbers compare to 2009 as we have started the mapping process. We will be posting completed quads with numbers on our web site (http://web.vims.edu/bio/sav/sav10/quadindex.html) and I’ll provide a general update on the bigger picture for the lower bay toward the end of the summer.

Please remember that the SAV abundance still remains below what we had measured in the 1990s and early 2000 timeframe. Many sections of the major tributaries like the James, York and Rappahannock rivers remain devoid of any grass.  In addition, areas where the beds are recovering from the eelgrass dieback, as well as earlier losses, are still below their recent historic highs.

We will be watching what happens to SAV during this extreme summer heat.  We may have already seen some dieback of eelgrass in one area. Lethal temps for eelgrass are around 35C (95F) and we have already measured these temps in some shallow water areas. We have a sensor at our South Bay eelgrass restoration site that is telemetering data to VIMS so if you want to see what one SAV bed experiences on a minute to minute basis check this site out: http://www.ysieconet.com/public/WebUI/?hidCustomerID=154 .

Our SAV blog (http://thumper-web.vims.edu/bio/sav/wordpress/) is up and running and we are slowly adding observations from around the bay. We already have a number of interesting observations. Please let us know what you are seeing out there!  Various Riverkeepers have really been a big help in recent weeks.

We begin the acquisition phase of the low salinity and freshwater areas of the Bay and tributaries later this month so stay tuned for more SAV updates.

Cheers

JJ

Tags: Aerial Updates

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