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:
The frequency that the Phytoplankton IBI scores exceeded the threshold level of 3, during the spring-summer sampling periods, was determined. In 2010, samples were collected approximately six times at each station. The overall reporting region scores were calculated by accounting for the surface area of the region represented by each sampling station.
This map shows the average spring-summer Phytoplankton Index of Biotic Integrity (Phytoplankton IBI) score for 2010. In 2010, all sampling stations except one within the Bay's tributaries had average Phytoplankton IBI scores between 1 and 2.9 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 (scoring between 3-4). Some regions improved (Mid Bay, Patuxent River, Rappahannock River), and others declined (Potomac River, Patapsco and Back Rivers, Choptank River).
In 2010, phytoplankton samples were collected at 31 stations during the spring (March-May) and summer (July-September). Samples were collected approximately six times at each station. Data from each sampling event were used to calculate a Phytoplankton IBI score. Phytoplankton IBI scores for each sampling station were then averaged and mapped.
Comparison of Bay Health Index scores for 2010 () compared to ()
|0 20 40 60 80 100|
|Upper Eastern Shore|
|Lower Western Shore (MD)|
|Patapsco and Back Rivers|
|Lower Eastern Shore (Tangier)|
|Upper Western Shore|
This figure ranks each region from best to worst for the Phytoplankton Index of Biotic Integrity (Phytoplankton IBI). The Mid Bay region has had the highest Phytoplankton IBI score for six years in a row and increased the margin to 32% in 2010. The next highest-ranked regions were the Lower Bay and Rappahannock River. Interestingly, the overall Bay score is high because the Mid Bay and Lower Bay scores are so good and these regions represent a large area of the Bay. Regions with the lowest Phytoplankton IBI scores were the Elizabeth (which scored a zero), the Patapsco and Back Rivers, and Potomac River. The Potomac River score declined sharply in 2010. No phytoplankton monitoring is conducted in the Lower Eastern Shore and Upper Western Shore regions.
This graph is dynamic, you can: a) show and hide items by clicking them in the legend, b) select year range (click and drag), and c) export as an image.