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Browse History: Aquatic Grasses (2011)
Indicator Icon Aquatic Grasses

Aquatic grasses, or submerged aquatic vegetation, are one of the most important habitats in Chesapeake Bay. Bay grasses provide critical habitat to key species such as blue crab and striped bass, and can improve water clarity.

Chesapeake Bay - Indicator Details:





  Indicator Selection Diagram


Threshold Map


This map shows progress of each reporting region towards meeting the aquatic grasses restoration goal. Overall progress towards the restoration goal decreased slightly for the third year in a row, due to decreases in the area of aquatic grasses in the Upper Western Shore, the Upper and Lower Bay, the Rappahannock River, and several other reporting regions. Aquatic grasses in the Potomac, Patuxent, Patapsco and Back, and James Rivers remained steady this year. Aquatic grasses in the Choptank River were the highest since 2005, a strong rebound after a number of years with failing grades. However, this growth is still considered poor when compared to goals based on historic levels. This assessment is based on aquatic grass survey data provided by VIMS. See http://www.vims.edu/bio/sav for more information.

Creating this map
Estimates of aquatic grasses cover are derived each year by VIMS using aerial surveys. The aquatic grasses score is determined as the area of aquatic grasses present in each of the 15 reporting regions as a percentage of the restoration goal. Each reporting region is assigned a score representing progress towards the goal.

Data Map


This map shows the preliminary aquatic grass (submerged aquatic vegetation) distribution in 2011. While aquatic grasses fringe long sections of the shoreline, there are many areas of the Bay in which they no longer occur or have experienced a significant reduction in area. For example, aquatic grasses are absent in the Back, West, and Nanticoke Rivers and have very low coverage in many other areas. During 2011, aquatic grasses decreased considerably in many regions such as the Rappahannock, York, Lower Bay, Upper Western Shore and across the Susquehanna Flats of the Upper Bay. Only one region showed an increase between 2010 and 2011, the Choptank River, which improved by ~20%. This assessment is based on aquatic grass survey data provided by VIMS. See http://www.vims.edu/bio/sav for more information.

Understanding this map
Estimates of aquatic grasses cover are derived each year by VIMS using aerial surveys. Survey data was used to determine area of aquatic grass in each reporting region. Due to Hurricane Irene, aerial surveys were unable to be conducted of the Potomac, and Patapsco and Back regions. Estimates of aquatic grass extent was based on the observations from 2010. See the methods for aquatic grasses for more details.

Ranking


Comparison of Bay Health Index scores for 2011 () compared to
()


Score Legend
 Score (%)
 0               20               40               60               80              100
  
Upper Bay  
Upper Western Shore  
James River  
Potomac River  
Rappahannock River  
Lower Bay  
Overall Bay  
Lower Eastern Shore (Tangier)  
Choptank River  
Upper Eastern Shore  
York River  
Patuxent River  
Mid Bay  
Lower Western Shore (MD)  
Patapsco and Back Rivers  
Elizabeth River  
 No Growth Zone

This figure ranks each region from best to worst for aquatic grasses scores in 2011. The aquatic grasses score is determined as the area of aquatic grasses present as a percentage of the restoration goal. The Upper Bay and Upper Western Shore regions are closest to the restoration goal; though both took a considerable turn for the worse in 2011. The Rappahannock was also much lower in 2011 and has returned to 2008 levels of growth. The York, Patuxent,  Mid Bay, Lower Western Shore (MD), Patapsco and Back, and the Elizabeth River regions all received failing grades for aquatic grass growth in 2011. Overall, most regions are far from achieving their restoration goals. This assessment is based on aquatic grass survey data provided by VIMS. See http://www.vims.edu/bio/sav for more information.


Excel Spreadsheet

Threshold Levels

Reporting Region SAV restoration goal by reporting region (acres)
Upper Bay14,978
Mid Bay18,436
Lower Bay35,872
Patuxent River1,954
Potomac River21,203
Rappahannock River2,534
York River

3,304

James River2,629
Elizabeth RiverNo Grow Zone
Upper Eastern Shore12,866
Choptank River13,953
Lower Eastern Shore (Tangier)57,651
Patapsco-Back Rivers389
Upper Western Shore3,661
Lower Western Shore (MD)1,811
Total191,241