Virginia CZM Program: 2015 Coastal Grant Project Description and Final Summary

Project Task:

7

Grantee:

Virginia Institute of Marine Science

Project Title:

2015 Submerged Aquatic Vegetation Distribution and Abundance Survey

Project Description:

Submerged aquatic vegetation (SAV) is a critical living resource in Chesapeake Bay that has undergone rapid and dramatic baywide fluctuations in distribution and abundance over the last two decades, and is being subjected to declines in water quality and to ever increasing pressure from recreational, commercial, and industrial demands. Because SAV is dependent on good water quality to which it responds over short time scales, it can be an important indicator of water quality.

In 2015, VIMS will continue the annual SAV survey program, begun in 1984, by mapping SAV in the shoal areas of the entire Chesapeake Bay and its tributaries from aerial photography acquired during late spring to late summer.

Digital aerial photography will be acquired at a photographic scale of approximate 1:24,000, following guidelines that address tidal stage, plant growth, sun angle, turbidity, wind, atmospheric transparency, sensor operation and land features to allow for acquisition of photographs under near optimal conditions. 

Ground data on species distribution and abundance will be collected by participating agencies and citizen groups from as many of the Chesapeake Bay Program segments as possible and included in the final report.

The aerial photographs will be evaluated for SAV signatures using all available information.  Photographs containing SAV signatures will be orthographically corrected and mosaiced by USGS 7.5 minute topographic quadrangles using Orthobase and Imagine image processing software .

The perimeters of all SAV beds mapped from the 2015 aerial photography will be delineated on-screen using ArcInfo geographic information system (GIS) software and stored in an ArcInfo GIS database.  A final report will include maps of all SAV beds, and areas of these beds, as well as any ground truth information submitted to VIMS.  The report will be published on the VIMS web site, as in past years.  SAV polygons will also be available on the VIMS SAV interactive web site (http://vims.edu/bio/sav/maps.html?svr=www )

Federal Funding:

$60,000

Project Contact:

Robert J. Orth; 804.684.7392; jjorth@vims.edu

Project Status:

10/1/15 - 12/31/16; Project Completed

Final Product Received:

Final Project Summary serves as Final Product. 

Project Summary:

The 2015 distribution of submerged aquatic vegetation (SAV) in Chesapeake Bay and its tributaries was mapped primarily from multispectral digital imagery and supplemented with black and white aerial photographs for a small set of areas. These were acquired between May and November 2015, with a resolution of 24 cm, encompassing 186 flight lines. For 2015, 37,358 hectares (92,315 acres) of SAV were mapped in Chesapeake Bay and its tributaries.

Notable changes in SAV distribution were measured between 2015 and 2014. SAV increased 22% from 30,528 ha (75,438 ac) to 37,358 ha (92,315 ac). SAV increased in all four (Tidal Fresh, Oligohaline, Mesohaline, and Polyhaline) salinity zones in the Chesapeake Bay. In 2015, SAV increased in 54, decreased in 13, and remained unvegetated in 26 of the 93 CBP segments. The 6,830 ha increase in baywide SAV coverage in 2015 resulted in the most area of SAV reported for the Bay in the history of the Baywide annual areal survey (1984 - 2015). This represents a continued recovery from strong declines in 2011 and 2012 that reduced SAV abundance to a level last reported for the Bay in 1986. The 2015 increase was the result of a strong increase in the Mesohaline (4,457 ha), and Oligohaline (1,177 ha) salinity zones and smaller relative increases in the Tidal Fresh (802 ha) and Polyhaline (393 ha) salinity zones. In 2015, the increase in the Mesohaline salinity zone is due primarily to a continuing rapid expansion of widgeongrass, including in areas where SAV had not been mapped by previous surveys. However this species has had boom and bust cycles throughout the history of this survey. A similar rapid increase in widgeongrass in 2001 and 2002 was followed by an approximately 50% loss the following year. There has been a modest recovery of eelgrass in the polyhaline areas where the hot summers of 2005 and 2010 resulted in dramatic diebacks. The largest SAV bed in the bay, on the Susquehanna Flats in segment CB1TF1, persisted through 2012 and continues to increase in coverage, returning to areas impacted by Hurricane Irene and Tropical Storm Lee in 2011.

In the Tidal Fresh Bay Zone (19 CBP segments), SAV increased 13% from 6,270 ha (15,495 ac) in 2014 to 7,073 ha (17,477 ac) in 2015. In the Oligohaline Bay Zone (25 CBP segments), SAV increased 40% from 2,914 hectares (7,200 ac) in 2014 to 4,091 hectares (10,109 ac) in 2015. In the Mesohaline Bay Zone (41 CBP segments), SAV increased 30% from (14,992 hectares (37,048 ac) in 2014 to 19,450 hectares (37,048 ac) in 2015. In the Polyhaline Bay Zone (8 CBP segments), SAV increased 6% from 6,352 ha (15,696 ac) in 2014 to 6,745 ha (16,667 ac) in 2015.

For 2015, 6,039 hectares (14,924 ac) were mapped in the Delmarva Peninsula Coastal Bays Zone (Assawoman, Isle of Wight, Sinepuxent, Chincoteague, and Southern Virginia coastal bays).

The 2015 SAV report can now be viewed at:

http://web.vims.edu/bio/sav/sav15/index.html and also on VIMS’s interactive map: http://web.vims.edu/bio/sav/maps.html.

Disclaimer: This project summary provides the federal dollars initially awarded to the grantee. Due to underexpenditure or reprogramming of grant funds, this figure may change. For more information on the allocation of coastal grant funds, please contact Laura McKay, Virginia Coastal Program Manager, at 804.698.4323 or email:Laura.McKay@deq.virginia.gov

A more detailed Scope of Work for this project is available. Please direct your request for a copy to Virginia.Witmer@deq.virginia.gov

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Virginia Department of
Environmental Quality
P.O. Box 1105
Richmond, VA 23218
(804) 698-4000


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