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Browse History: Aquatic Grasses (2007)
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 region towards meeting the aquatic grasses restoration goal. Progress towards the restoration goal was slightly improved in 2007 compared to 2006 due to substantial increases in the area of aquatic grasses in the Upper Bay and Upper Western Shore. Some large increases in aquatic grasses area were also recorded in the Lower Bay region compared to 2006, but these only represent a small increase relative to the restoration goal. At the other end of the spectrum, many regions were less than 20% towards the restoration goal, including the Choptank, Patuxent, York, and Patapsco and Back Rivers.

Creating this map
Estimates of aquatic grasses cover are derived each year 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 color representing progress towards the goal.

Data Map


This map shows the preliminary aquatic grasses (submerged aquatic vegetation) distribution in 2007. 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 cover in many other areas. During 2007, many areas of the Bay, such as the Upper Bay and Upper Western Shore regions, experienced a significant increase in aquatic grasses area compared to 2006. There were also many regions recording a decline in aquatic grasses area such as the Patapsco and Back Rivers, Patuxent River and Lower Western Shore (MD) regions.

Understanding this map
Estimates of aquatic grasses cover are derived each year using aerial surveys. Survey data was used to determine area of aquatic grass in each reporting region for 2006 and 2007. Percent (%) difference in area between 2006 and 2007 was calculated.

Ranking


Comparison of Bay Health Index scores for 2007 () compared to
()


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

This figure ranks each region from best to worst for aquatic grasses scores in 2007. 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. The Upper Western Shore and Upper Bay regions are closest to the restoration goal. Aquatic grasses in the Upper Bay region have been expanding in recent years. The Patapsco and Back Rivers region had the lowest score in 2007, mostly due to loss of aquatic grasses in the upper reaches. Overall, most regions are far from achieving their restoration goals.


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