Lower Eastern Shore Basin Tributaries
During the period 1999-2003, lower eastern shore basin tributaries exhibited
good overall benthic community condition. Condition was best in
Fishing Bay, the mesohaline portion of the Nanticoke River, the Manokin River,
and the Big Annemessex River. Probabilities of observing good benthos
in these systems were greater than 50%, with the lower bound of the confidence
interval above 25% (Table 1). Benthic community
condition was worse in
the Pocomoke River. In Tangier Sound and Pocomoke Sound condition was
of intermediate quality. Forty-four percent of all sites in these two
systems failed the restoration goals (B-IBI < 3), but many of the failing
sites were only marginally degraded. This is reflected in the relatively
high probabilities of observing benthos of intermediate quality in these two
systems (Table 1).
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Benthic community condition for Lower Eastern Shore Basin sites.
Red = Severely Degraded; Black = Degraded;
Violet = Marginal; Green = Meets Goals
All sites sampled to date (1994-2003) shown.
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Low biomass relative to reference conditions is a problem affecting lower
eastern shore basin tributaries. Fifty percent or more of the sites in the
Wicomico River, Manokin River, Big Annemessex River, Tangier Sound, and
Pocomoke Sound exhibited low biomass during the period 1999-2003. A
fixed long-term monitoring station in the Nanticoke River exhibited a degrading
trend in the B-IBI, and significant degrading trends in biomass and species
diversity (station 062 on map). The major problem affecting water
quality in the Lower Eastern Shore Basin is high sediment loads, which may
reduce the amount
of food that is available from the water column to the benthos. High
river flows in 2003 may have exacerbated the high sediment load problem.
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Water Quality Map
Segment Analysis
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Table 1.
Total number of sites, degraded sites, and probabilities* (90% confidence
limits) of observing degraded benthos, non-degraded benthos, or benthos of
intermediate condition (indeterminate for low salinity habitats) for Maryland
Lower Eastern Shore Basin tributaries, 1999-2003.
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*
Probabilities adjusted according to Agresti and Caffo (2000). Confidence
limits adjusted for segments with ≥ 5 sites. Exact confidence
limits used for segments with < 5 sites.
Note: This latest assessment for the Tributary Teams uses only 5 years
of data (1999-2003); methods are described in Llansσ et al. 2003. Segments
are Chesapeake Bay Program subunits having similar salinity and hydrographic
characteristics.
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