Aerial and Field SAV Observations

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Survey of underwater grasses shows both decline and resilience in 2011

March 26th, 2012 by admin · 1 Comment

by Staff | March 28, 2012
Grasses decrease 21% Baywide due to extreme environmental conditions; Susquehanna Flats grass beds survive

An annual aerial survey led by researchers at the Virginia Institute of Marine Science shows that the abundance of underwater grasses in Chesapeake Bay and its tidal rivers declined by 16,590 acres between 2010 and 2011.

The survey results, announced today by the Chesapeake Bay Program (CBP), show that grass beds declined from 79,664 acres in 2010 to an estimated 63,074 acres in 2011. This is the lowest Bay-wide acreage since 2006 and is much more typical of what was observed prior to 1991 when grass acreages were at the lowest levels recorded by the aerial survey. Only 57,956 acres were mapped Bay-wide in 2011 and an estimated 5,119 additional acres may have been present (for an estimated Bay-wide total of 63,074).
Read More about the 2011 Survey results…

A Comparison in Photographs: 2010 vs 2011

Aerial photo of the north central portion of Susquehanna Flats in 2010 (left) and in 2011 (right). 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

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after



Aerial photography of Broad Creek, a tributary on the north shore of the lower Choptank River. Outlined polygons reflect the density in 2011 (right) compared to 2010 (left) when SAV was less abundant here. SAV in this creek has been dominated by widgeongrass. (Yellow: <10% cover, blue: 10=40% cover, light green: 40-70% cover, dark green: 70-100% cover)

Left - Broad Creek on 8/31/10, Right - Broad Creek on 8/23/11

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after


Aerial photo of an SAV bed off Eastern Neck Island at the mouth of the Chester River. The bed is much larger in 2011 (right) than it was in 2010 (left). Red lines indicate the area of SAV presence.

Left - Eastern Neck Island on 8/30/10, Right - Eastern Neck Island on 8/23/11

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after


Aerial photo of the north shore of the James River upriver of Kennon Creek and across from north end of Kennon Marsh. The dark shape in the river on the right image taken in 2011 is an SAV bed that was not present in 2010 (left image). This is one of the first freshwater beds mapped in the mainstem James River since the area was first surveyed in 1998.

Left - James River on 9/11/10, Right - James River on 8/16/11

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after

Tags: SAV News

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