Browse History: Choptank River (2006) | Patuxent River (2007) | Get Involved (2007) | Phytoplankton Index of Biotic Integrity (2007)
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.

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Threshold Map

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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 phytoplankton community scores in 2007, with moderate-good ratings. Four regions of the Bay had very poor scores in 2007, these being the Choptank, Patuxent, Elizabeth, and Patapsco and Back Rivers. Phytoplankton IBI scores increased in 8 regions in 2007 compared to 2006 and decreased in 3 (no monitoring in 4 regions in 2006).

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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This map shows the average spring-summer Phytoplankton Index of Biotic Integrity (Phytoplankton IBI) score for 2007. In 2007, the majority of sampling stations had average Phytoplankton IBI scores between 1and 3 out of a possible 5, indicating that the phytoplankton communities were in degraded conditions relative to reference communities. All three sampling stations in the Patuxent River recorded a poor average phytoplankton score. Average phytoplankton IBI scores above 3 only occurred at 6 monitoring stations, all located in the Mid and Lower Bay regions. The predominance of high scoring Phytoplankton IBI stations in the Lower Bay region may partially be attributed oceanic water exchange. In 2007, four additional Phytoplankton IBI monitoring stations were included in the survey to help provide a more comprehensive geographic coverage.

Understanding this map
Phytoplankton samples were collected at 31 stations, up to 13 times, during the spring and summer of 2007. 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 2007 () compared to
()


Score Legend
 Score (%)
 0               20               40               60               80              100
  
Mid Bay  
Lower Bay  
Overall Bay  
Rappahannock River  
Upper Bay  
James River  
Upper Eastern Shore  
 ND
York River  
Potomac River  
Lower Western Shore (MD)  
 ND
Choptank River  
Patapsco and Back Rivers  
Patuxent River  
Elizabeth River  
 0
Lower Eastern Shore (Tangier)  
 ND
 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 Mid Bay region had the highest Phytoplankton IBI score, followed by the Lower Bay region. Regions with the lowest Phytoplankton IBI scores were the Elizabeth, Patuxent, 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 two regions in 2007. Phytoplankton IBI scores increased in 8 regions in 2007 compared to 2006 and decreased in 3, (no monitoring in 4 regions in 2006).


Excel Spreadsheet