A Comparison of two Index of Biotic Integrity (IBI) Calculations for Benthic Macroinvertebrates and Fish at a Mitigation Site
Martha McCauley
EA Engineering, Science, and Technology, Inc.
PBC
Hunt Valley, MD
Authors:
Martha McCauley - EA Engineering, Science, and Technology, Inc., PBC
Sarah Koser - Chesapeake Bay Trust and EA Engineering, Science, and Technology, Inc., PBC
Julia Klassen - EA Engineering, Science, and Technology, Inc., PBC
Brian Cox - Maryland Department of Transportation State Highway Administration
Matt Harper - Maryland-National Capital Park and Planning Commission - Montgomery Parks
Index of Biotic Integrity (IBI) is a metric score used to provide insights to biological composition of stream biota that ultimately is used to evaluate stream quality. Methodology for calculating IBI metrics should be comparable across regions and times, rapid, and reflective of species of interest for a geographical region. There are Maryland state accepted methods for quantifying IBIs as well as regional guidance (Montgomery County). Our aim was to determine how these methods differ in effort, scoring, and application. The state (Maryland) and regional (Montgomery County) IBIs were calculated and compared in a pre-construction monitoring study tasked by the Maryland Department of Transportation State Highway Administration for a Bypass and Mitigation Site in Brookeville, Montgomery County, Maryland. Benthic macroinvertebrate and fish in-stream assessments were performed at two streams in 2016 and 2017 using the Maryland Biological Stream Survey (MBSS) methodology as required for use of the state-based IBI. The 2016 sampling event consisted of seven benthic and four fish sampling locations, and the 2017 event consisted of five benthic and two fish sampling locations. The state-wide MBSS IBI scores resulted in a mix of stations rated Fair and Good, and the regional IBI scores were predominantly Good with two stations classified as Excellent for fish. Both scoring methods required similar levels of field effort. The regional IBI requires knowledge of stream order and streambank soil composition to determine appropriate criteria for use, is more regionally-specific, and reflects status and changes in subwatershed biota. The MBSS IBI requires estimates of catchment area and the sample location area to calculate specific metrics, tends to score lower than regional IBI metrics, can be used in conjunction with historical MBSS IBI data, and provides comparative data for long-term studies over large regions. Both IBI scoring criteria should be considered for use based on the project goals, geographical region, and project timeline.
About Martha McCauley
Mrs. McCauley has worked at EA Engineering, Science, and Technology, Inc., PBC for 8 years and has 12 years of experience in the ecological studies of aquatic habitats, focusing primarily on the population, diversity, and ecological role of fish and benthic invertebrates. This includes benthic macroinvertebrate sampling in streams, bays, and harbors, environmental assessments using MBSS and the U.S. Environmental Protection Agency Rapid Bioassessment Protocol methodology, stream electrofishing surveys, and acoustic tracking of fish in a harbor. She has experience in multiple benthic sampling methods, including dipnet, kick net, surber, and Ponar grab sampling. Ms. McCauley has experience in fish collection methods including backpack electrofishing, boat electrofishing, beach seines, and gillnets. She also has experience with identifying freshwater and estuarine fish commonly found in the state of Maryland. Field experience also includes sediment sampling for contaminants and toxicity, benthic tissue extraction, water quality monitoring, and fish population surveys.