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Browse History: Biotic Index (2011)
Indicator Icon Biotic Index

The Biotic Index combines the aquatic grasses, Benthic Index of Biotic Integrity, and Phytoplankton Index of Biotic Integrity into a single overarching score.

Chesapeake Bay - Indicator Details:





  Indicator Selection Diagram


Index Map

This map shows the 2011 Biotic Index scores for each of the 15 reporting regions. Highest Biotic Index scores occurred in the Upper Bay and Lower Bay regions. The Upper Bay scored high for all three biotic indicators. The lowest Biotic Index scores occurred in the Elizabeth and Patuxent River regions. Biotic Index scores increased in six regions in 2011, decreased in seven, and remained steady in two. This was the first year a Biotic Index grade has been assigned for the Elizabeth River because Benthic IBI data was available for 2011.

Creating this map
This map shows Biotic Index values for each of the regions. Biotic Index for each reporting region is the average of the aquatic grasses, Benthic Index of Biotic Integrity, and Phytoplankton Index of Biotic Integrity scores.

Ranking


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


Score Legend
 Score (%)
 0               20               40               60               80              100
  
Lower Bay  
Upper Bay  
Upper Western Shore  
Overall Bay  
Lower Western Shore (MD)  
Rappahannock River  
Lower Eastern Shore (Tangier)  
Upper Eastern Shore  
Mid Bay  
Patapsco and Back Rivers  
James River  
Choptank River  
York River  
Potomac River  
Patuxent River  
Elizabeth River  
 0

This figure ranks each region from best to worst for the Biotic Index. Highest ranked region in 2011 was the Lower Bay, with a score of 65% (moderately good). Second highest ranked region was the Upper Bay, at 61%. High Biotic Index Scores in these two regions are generally due to good benthic community scores. The Elizabeth and Patuxent River regions had the lowest Biotic Index scores in 2011, both scoring less than 20% (very poor). Biotic index scores increased in six regions in 2011 compared to 2010 and decreased in seven.


Excel Spreadsheet