Maryland Western Tributaries

Stratum Summary

Benthic community impairment in the upper western tributaries of the Bay was high in 2003, with 60% of the area exhibiting degraded condition. The severity of degradation was particularly high in 1996 and 2002 (high percentage of severely degraded condition; no sites classified by the B-IBI as "marginal"). The western tributaries suffer from various types of pollution, including toxic contamination, low dissolved oxygen, excess phytoplankton growth, lack of water clarity, and nutrient runoff. These factors vary greatly among systems and the stress to the benthic community varies accordingly. No clear trend in the estimates of areal degradation were observed during the 1995-2003 time series (chart below).

The sampling areas in the Maryland Western Tributaries stratum fall into three basins, referred to as the Upper Western Shore Basin (yellow shading on map above), the Patapsco/Back Basin (raspberry shading), and the Lower Western Shore Basin (green shading). There are further details at the basin level which the Benthic Program provides to summarize benthic community condition for the basin Tributary Teams. Tributary Teams consider basin summaries that synthesize monitoring information from several sources, including watershed, ambient water quality, habitat, and living resources components. This information is linked to nutrient and sediment pollution sources and is intended to provide the Tributary Teams with resources to consult in setting Tributary Strategy Goals.