Maryland Biological Stream Survey

Collection of benthic macroinvertebrate sample for MBSS project.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 sites sampled since 1995 are represented by black dots. 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.

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, 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.

To Learn More:

  • Morgan II, R. P., K. Kline, and S. F. Cushman. 2007. Relationships Among Nutrients, Chloride and Biological Indices in Urban Maryland Streams. Urban Ecosystems. 10:153-166. (abstract link)
  • Southerland, M. T., Rogers, G. M., Kline, M. J., Morgan, R. P., Boward, D. M., Kazyak, R., et al. 2007. Improving biological indicators to better assess the condition of streams. Ecol. Indic., 7(4), 751–767 (abstract link).
  • Maryland DNR's MBSS Home Page
  • Technical Report: Survey of Acidic and Episodically Acidic Streams in Western Maryland (download pdf)
  • Technical Report: Current Distribution, Abundance, and Habitat Preferences of the Stonecat (Noturus flavus) in Maryland (download pdf)
  • MBSS Sampling Manual (download pdf)

Project PI:

Dr. Raymond P. Morgan II