Browse History: Patapsco and Back Rivers (2007) | Biotic Index (2007) | Rappahannock River (2006) | Aquatic Grasses (2006)
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

You need to upgrade your Flash Player


Editable Vector Version (SVG)
High Resolution Raster Version (JPG)
Station Data
This map shows progress of each region towards meeting the aquatic grasses restoration goal. Progress towards the restoration goal was significantly less in 2006 compared to 2005 due to a widespread decline in aquatic grasses cover. Factors causing the decline are thought to include above average water temperatures in the fall of 2005, a dry spring, and the early summer rain event. In 2006, the Upper Bay region had the highest score (65%), largely due to recent expansion of aquatic grasses on the Susquehanna Flats. At the other end of the spectrum, many regions were less than 20% towards the restoration goal.

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

You need to upgrade your Flash Player


Editable Vector Version (SVG)
High Resolution Raster Version (JPG)
Station Data

This map shows the distribution of aquatic grasses (submerged aquatic vegetation) in 2006 and the % change in area between the 2005 and 2006 surveys for each of the 15 reporting regions. While aquatic grasses fringe long sections of the shoreline, there are many areas of the Bay they have been completely lost or significantly reduced in cover. For example, aquatic grasses are absent in the Back, Choptank, and Nanticoke Rivers and have very low cover in most other areas. During 2006, many regions of the Bay experienced a significant reduction in aquatic grasses cover, although some regions (York, James, and Rappahannock Rivers) had an increase in cover. The reduction in aquatic grasses cover was likely due to factors such as above average water temperatures in fall 2005, the dry spring conditions, and the early summer rain event.

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 2005 and 2006. Percent (%) difference in area between 2005 and 2006 was calculated.

Ranking


Comparison of Bay Health Index scores for 2006 () compared to
()


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

This figure ranks each region from best to worst for the indicator aquatic grasses. 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 Bay region was the closest to the restoration goal. The aquatic grasses in this region have expanded in recent years, but there was some decline in 2006. The Choptank River score was the lowest, perhaps due to a significant reduction in area (-54%) between the 2005 and 2006 surveys. Overall, most regions are far from achieving their restoration goals.


Excel Spreadsheet

Threshold Levels

Reporting Region SAV restoration goal by reporting region (acres)
Upper Bay 14,978
Mid Bay 18,436
Lower Bay 35,872
Patuxent River 1,954
Potomac River 21,203
Rappahannock River 2,534
York River

3,304
James River 2,629
Elizabeth River No Grow Zone
Upper Eastern Shore 12,866
Choptank River 13,953
Lower Eastern Shore (Tangier) 57,651
Patapsco-Back Rivers 389
Upper Western Shore 3,661
Lower Western Shore (MD) 1,811
Total 191,241