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Browse History: Biotic Index (2009) | Chlorophyll a (2009) | Dissolved Oxygen (2009) | Phytoplankton Index of Biotic Integrity (2009)
Indicator Icon Phytoplankton Index of Biotic Integrity

Phytoplankton (microalgae) is an important component of the Bay's food web. The Phytoplankton Index of Biotic Integrity (PIBI) is a measure of the microscopic algal community condition.

Chesapeake Bay - Indicator Details:





  Indicator Selection Diagram


Threshold Map


This map illustrates the overall Phytoplankton Index of Biotic Integrity (Phytoplankton IBI) scores for each of the 15 reporting regions. The Mid and Lower Bay regions had the highest (best) phytoplankton community scores in 2009, with moderate-good ratings. Five regions of the Bay had very poor scores in 2009, compared to six in 2008. Very poor scores were recorded in the Choptank River, Upper Eastern Shore, Patuxent River, Patapsco and Back Rivers, and the York River. No phytoplankton monitoring is conducted in the Lower Eastern Shore and Upper Western Shore regions.


Creating this map
The frequency that the Phytoplankton IBI scores exceeded the threshold level of 3, during the 12-13 spring-summer sampling times, was determined. The overall reporting regions score was calculated by accounting for the surface area of the region represented by the sampling station.

Data Map


This map shows the average spring-summer Phytoplankton Index of Biotic Integrity (Phytoplankton IBI) score for 2009. In 2009, all sampling stations within the Bay's tributaries had average Phytoplankton IBI scores between 1 and 3 out of a possible 5, indicating that the phytoplankton communities were in degraded conditions relative to reference communities. In 2008, most monitoring stations within the Bay's mainstem had moderately good phytoplankton communities (3-4). For the most part, this pattern held true in 2009 as well, with the exception of the Upper Bay – the stations there were also considered degraded in condition relative to reference communities. 


Understanding this map
Phytoplankton samples were collected at 31 stations, up to 13 times, during the spring and summer. Data from each sampling station and time was used to calculate a Phytoplankton IBI score. Phytoplankton IBI scores for each sampling station were then averaged and mapped.

Ranking


Comparison of Bay Health Index scores for 2009 () compared to
()


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

The Mid Bay region had the highest Phytoplankton IBI score in 2009 by a large margin—almost 20%. The next highest-ranked region was the Lower Bay, also a mainstem region. Regions with the lowest Phytoplankton IBI scores were the Elizabeth (which scored a zero), York, Patuxent, the Patapsco and Back Rivers, Upper Eastern Shore, and Lower Western Shore (MD). Phytoplankton IBI scores increased in 5 regions in 2009 compared to 2008 and decreased in 7. No phytoplankton monitoring is conducted in the Lower Eastern Shore and Upper Western Shore regions.



Excel Spreadsheet