Browse History: Overall Bay (2007) | Upper Western Shore (2007) | Elizabeth River (2006) | Phytoplankton Index of Biotic Integrity (2006)
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:





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Threshold Map

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Station Data
This map illustrates the overall Phytoplankton Index of Biotic Integrity (Phyoplankton IBI) scores for each of the 15 reporting regions. The Lower Bay and Elizabeth River regions had the highest phytoplankton community scores in 2006, with moderate ratings. Five regions of Bay had poor ratings in 2006, these being the Choptank, Potomac, York, James, and Patapsco and Back Rivers. The 2006 Phytoplankton IBI scores for most systems were similar to scores assigned in 2003, an above average river flow year. This suggests that although the annual flow rates for the Bay in 2006 were average, the dry spring conditions followed by the early summer rain event may have led to lower overall Phytoplankton IBI scores.

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

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Station Data

This map shows the average spring-summer Phytoplankton Index of Biotic Integrity (Phytoplankton IBI) score for 2006. In 2006, the majority of sampling stations had average Phytoplankton IBI scores between 1and 3 out of a possible 5, indicating that on average, phytoplankton communities were in degraded conditions relative to reference communities. Average Phytoplankton IBI scores above 3 only occurred at 5 monitoring stations. Three of these stations were located in the Lower Bay where water exchange with the Atlantic Ocean is likely having a significant effect on the community condition. The other two locations were the Upper Bay region and the upper reaches of the York River.

Understanding this map
Phytoplankton samples were collected at 27 stations, 12-13 times during the spring and summer of 2006. 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 2006 () compared to
()


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

This figure ranks each region from best to worst for the indicator Phytoplankton Index of Biotic Integrity (Phytoplankton IBI). The Elizabeth River region had the highest Phytoplankton IBI score, followed by the Lower Bay and the Mid Bay. Regions with the lowest Phytoplankton IBI scores were the Choptank and the Patapsco and Back Rivers. The number of sampling stations in all regions for this indicator is relatively few, with insufficient data, and therefore no assessment, for four regions in 2006.


Excel Spreadsheet