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Bottom Habitat

According to provisional data, 59 percent of the Chesapeake Bay scored at least a three on the one-to-five scale that measures the health of benthic organisms and bottom habitat in 2014. This is the largest percentage of goal-achieving bottom habitat since tracking began in 1996.




Benthic Habitat (Index of Biological Integrity) (2014) Percent of Goal Achieved

Map: Benthic Habitat (Index of Biological Integrity) (2014) Percent of Goal Achieved

Date created: Jul 02 2015 / Download

This map shows the percent of the Index of Biological Integrity indicator goal achieved by segment.


Benthic Habitat (Index of Biological Integrity) (2014) Annual Average Score by Sampling Station

Map: Benthic Habitat (Index of Biological Integrity) (2014) Annual Average Score by Sampling Station

Date created: Jul 02 2015 / Download

This map shows the 2014 indicator status of the Benthic Index of Biological Integrity by station.


Importance

The benthic community is made up of plants and animals that live on or in the sediment at the bottom of the Chesapeake Bay. Known as benthos, this community includes microscopic plants and small invertebrates like clams, oysters, shrimp-like crustaceans and worms. Because benthos are often unable to move to avoid chemical contaminants, low dissolved oxygen or other environmental stressors, their health is an important indicator of the health of the Bay.

Goal

The health of benthic organisms and bottom habitat is measured on a scale of one (very degraded) to five (least impaired). The goal is for the entire Chesapeake Bay to earn at least a three on this scale.

Long-term trend (1996-2014)

On average, 47 percent of the Chesapeake Bay scored at least a three on the Benthic Index of Biotic Integrity (B-IBI) scale between 1996 and 2014. The health of the Bay’s benthos reached its lowest point in 2006 (with 41 percent of the Bay scoring at least a three on the B-IBI scale) and its highest point in 2014 (with 59 percent scoring at least a three on the scale).

Change from previous year (2013-2014) 

Provisional data show that as a whole, the health of the Chesapeake Bay’s benthos improved between 2013—when 47 percent of the Bay scored at least a three on the Benthic Index of Biotic Integrity (B-IBI) scale—and 2014—when 59 percent of the Bay scored at least a three on the B-IBI scale. While the health of the bottom habitat in both Maryland and Virginia tributaries saw improvements during this time, the biggest contributor to improving Bay-wide conditions was the Virginia and Maryland mainstem. Scientists note that the offshore passing of Hurricane Arthur last July and sustained winds last August led to improvements in dissolved oxygen in this portion of the Bay, which would have benefited benthos.

Additional Information

Collecting data

Scientists use the Benthic Index of Biotic Integrity (B-IBI) to score the health of benthic organisms and bottom habitat in the Chesapeake Bay. A sampling site’s B-IBI score can be ranked from one (very degraded) to five (least impaired). To determine a site’s score, scientists sample the benthic community and compare biodiversity, species abundance, biomass and other attributes to “reference values,” or the conditions that would be expected in a healthy environment. Each year, the Chesapeake Bay Benthic Monitoring Program samples 48 sites in areas targeted for pollution abatement and other management actions to assess changes in these benthic communities. The program also samples 250 randomly chosen sites to assess the overall health of Bay benthos.

Source of Data

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