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Browse History: Benthic Index of Biotic Integrity (2011)
Indicator Icon Benthic Index of Biotic Integrity

The Benthic Index of Biotic Integrity (BIBI) measures the condition of the benthic community (e.g. clams and others) living in or on the soft bottom areas of the Bay. These organisms are a key food source for many species including perch, spot, and croaker.

Chesapeake Bay - Indicator Details:





  Indicator Selection Diagram


Threshold Map


This map shows the overall Benthic Index of Biotic Integrity (Benthic IBI) scores for each of the 15 reporting regions in 2011. Benthic IBI evaluates the health of the benthic, or bottom-dwelling community (in soft-bottomed areas only).

Overall, benthic condition within Chesapeake Bay during 2011 was moderate, which was not a significant change from 2010. The highest scoring region in 2011 was the Lower Western Shore (MD) region, where benthic condition was classified as moderately good. The second and third best Benthic IBI scores were in the Lower and Upper Bay regions where conditions are classified as moderately good. Lowest scores occurred in the Elizabeth, James, and Potomac Rivers, and the Mid Bay regions, where the Benthic IBI condition was classified as very poor.

Creating this map
Samples for assessing benthic community (bottom habitat) were collected at approximately 250 sites in July, August, and September by the Chesapeake Bay Benthic Monitoring Program. Data from each sampling station is used to calculate a Benthic Index of Biotic Integrity (BIBI) score. The proportion of the reporting regions area meeting the Benthic Index of Biological Integrity score is calculated and mapped.

Data Map


This map shows the Benthic Index of Biotic Integrity (Benthic IBI) values for the summer of 2011. This Benthic IBI evaluates the health of the benthic community, or bottom-dwelling community (in soft-bottomed areas only). Values between 1 and 3 are considered to be degraded relative to reference communities, while values between 3 and 5 are considered to be close to reference community condition (i.e., moderate to good condition).

Stations with relatively good benthic community health were in the Upper Bay, Lower Bay, and Lower Western Shore (MD) regions. Areas with very poor Benthic IBI scores can be seen in many regions including the Elizabeth, Potomac, and James Rivers, and in the Mid Bay. The benthic diversity declined sharply in the James River where scores went down by ~40% for unknown reasons. These poor scores were balanced by considerable improvements to benthic diversity in the Choptank River, and Lower Western (MD), Upper Western, and Upper Eastern Shore regions. The Lower Western Shore (MD) impoved by 75% compared to 2010 (when it scored a 0%).  

Understanding this map
Samples for assessing the Benthic Index of Biotic Integrity (soft bottom community condition) were collected at approximately 250 sites in July, August, and September. Data from each sampling station is used to calculate a Benthic IBI score which ranges from 1 (poor benthic condition) to 5 (good benthic condition).

Ranking


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


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

This figure ranks each region from best to worst for the indicator Benthic Index of Biotic Integrity (Benthic IBI). The Benthic IBI evaluates the health of the benthic community, or bottom-dwelling community (soft-bottomed areas only).

The highest scoring region in 2011 was the Lower Western Shore (MD), where benthic condition was classified as moderately good. The next best Benthic IBI occurred in the Lower and Upper Bay regions where conditions are classified as moderately good. Four regions had very poor Benthic IBI scores in 2011, these being the Elizabeth, Potomac, Mid Bay, and James River regions. Overall, the declines in the benthic community diversity were balanced by the gains and the scores for the whole bay remain moderate compared to goals.


Excel Spreadsheet