Maryland Biological Stream Survey

electrofishing
Collection of fish using electrofishing techniques.

AL personnel have been working with the Maryland Department of Natural Resources since 1994 to provide analytical and sampling support for the Maryland Biological Stream Survey (MBSS). The MBSS uses random sampling to determine the status of wadeable streams and rivers in Maryland. The primary objective of the MBSS is to assess with known confidence the current status of biological resources in non-tidal streams and rivers in Maryland. The 12,600 miles of streams and rivers in Maryland represent a vital natural resource to all Marylanders because of the direct influence of tributaries on Chesapeake Bay water quality, and their critical importance of freshwater habitat for fishes and other living resources.

MBSS Sampling Scheme

Benthic macroinvertebrates and water quality samples are collected during the spring index period from March through early May, while fish, herpetofauna, in situ stream chemistry and physical habitat sampling are conducted during the low flow period in the summer, from June through September.

pie chart MBSS sites sampled since 1995 are represented by black dots.

Spring water quality parameters include acid neutralizing capacity (ANC), closed pH, sulfate, total nitrogen, total phosphorus, inorganic nutrients, and dissolved organic carbon. These variables help to characterize the sensitivity of the streams to acid deposition and to other anthropogenic stressors.

A variety of environmental issues affect Maryland streams, including acidification, nutrients, and land use change as a result of urbanization. The MBSS collects high quality stream data, which will help to better understand and address these issues affecting Maryland streams.

Areas in Maryland that are particularly prone to negative effects from stream acidification include western Maryland and the Coastal Plain regions. In this figure, distribution of ANC values for streams sampled from 2000 through 2002 are depicted. Sites with warmer colors indicate more sensitive streams.

Acidification

Acid rain is the largest and most widespread source of acidity in Maryland, affecting nearly one in five streams (18%). Other sources of acidity in Maryland include natural acidification, acid mine drainage and fertilizer runoff.

ANC is a measure of the capacity of dissolved constituents in the water to neutralize acids and is used as an index of the sensitivity of surface water to acidification. The higher the ANC, the more acid a stream can neutralize before experiencing a decrease in pH.

In Maryland, total nitrogen loadings tended to be highest on the Eastern Shore and in rural areas north of Baltimore. The figure above depicts the distribution of total nitrogen values for sites sampled from 2000 through 2002. Sites with darker colors indicate higher concentrations.

Nutrients

Nutrients, such as nitrogen and phosphorus, are important for life in all aquatic systems. In the absence of human influence, streams contain background levels of nutrients that are essential to the survival of the aquatic plants and animals in that system. However, during the last several hundred years, the amount of nutrients transported to many stream systems has increased greatly as a result of anthropogenic influences such as agricultural runoff, wastewater discharge, urban/suburban nonpoint sources, and atmospheric deposition. The MBSS provides a large dataset that can be used to assess nutrient concentrations under spring baseflow conditions. Although a full understanding of nutrient loadings also requires data collected during storm runoff events and over time (i.e., data collected over multiple years and seasons), the MBSS water chemistry results provide extensive spatial coverage and a useful picture of where nutrient levels are high and help pinpoint problem areas for further investigation.

For all non-tidal stream miles in Maryland, the provisional Combined Biotic Index (CBI) summarized in the figure above rates almost one-half (46%) of all stream miles poor, 42% fair, and 12% good. Using this Combined Index, the Potomac Washington Metro basin has the smallest percentage of stream miles rated good (<1%) while the Bush has the highest percentage in this category (25%).
What is an IBI?

An index of biotic integrity, or IBI, combines several measures of stream community health into one overall value, or index. By using an index, complex ecological information can be summarized and stream health can be rated as either good, fair, or poor.

Good streams are comparable to the highest quality reference streams and fair streams are comparable to the remainder of the reference streams. Poor streams are considered unhealthy compared to reference streams.

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Project PI: Dr. Raymond P. Morgan II

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