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Browse History: Biotic Index (2008) | Chlorophyll a (2008) | Dissolved Oxygen (2008) | Phytoplankton Index of Biotic Integrity (2008)
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 Bay region had the highest (best) phytoplankton community scores in 2008, with moderate-good ratings. Six regions of the Bay had very poor scores in 2008, compared to only 4 in 2007. Poor scores were recorded in the Upper Eastern Shore, Choptank, Patuxent, Elizabeth, York, and Patapsco and Back Rivers regions in 2008. 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 2008. In 2008, 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 contrast, most monitoring stations within the Bay's mainstem had moderately good phytoplankton communities (3-4). While there were some differences between the 2008 and 2007, in most cases phytoplankton conditions were very similar.

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 2008 () compared to
()


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

This figure ranks each region from best to worst for the Phytoplankton Index of Biotic Integrity (Phytoplankton IBI). The Mid Bay region had the highest Phytoplankton IBI score in 2008 by a large margin—over 25%. The next highest-ranked regions were also mainstem bay regions—Upper Bay and Lower Bay. Regions with the lowest Phytoplankton IBI scores were the Elizabeth (which scored a zero), York, Patuxent, and the Patapsco and Back Rivers. Phytoplankton IBI scores increased in 7 regions in 2008 compared to 2007 and decreased in 4. No phytoplankton monitoring is conducted in the Lower Eastern Shore and Upper Western Shore regions.


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