Aquatic Biological Assessment of the Watersheds of Anne Arundel County, Maryland: 2009
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Anne Arundel County, Maryland Department of Public Works Watershed, Ecosystem, and Restoration Services Aquatic Biological Assessment of the Watersheds of Anne Arundel County, Maryland: 2009 Aquatic Biological Assessment of the Watersheds of Anne Arundel County, Maryland: 2009 Prepared by: Anne Arundel County Department of Public Works Watershed, Ecosystem, and Restoration Services 2662 Riva Road Annapolis, MD 21401 and Tetra Tech, Inc. Center for Ecological Sciences 400 Red Brook Blvd. Suite 200 Owings Mills, MD 21117-5159 August 2011 Abstract The Anne Arundel County Department of Public Works (DPW) assesses water resource quality as it relates to the intended uses of the waterbodies and State regulations. One intended use of all waterbodies is the support of aquatic life. Assessment of watershed support of aquatic life can be accomplished for the entire County through probability-based site selection (stratified random), sampling of the stream biota, and calculation of site-specific and watershed wide indicators. Further, observations of the physical habitat and water quality can help describe conditions that may be contributing to biological degradation. Sampling in five primary sampling units (PSUs) in 2009 partially fulfills the goal of County-wide stream assessment. The PSUs include Marley Creek, Lower North River, West River, Little Patuxent River, and Rock Branch. The indicators used to assess the support of aquatic life in streams include the Benthic Index of Biological Integrity (B-IBI), the Rapid Bioassessment Protocol (RBP) physical habitat assessment, the MBSS Physical Habitat Index (PHI), and in situ water quality measures (temperature, dissolved oxygen, and specific conductance). Geomorphic conditions were also evaluated using the Rosgen classification of natural rivers. Each of these indicators was compared to established thresholds, and the percentage of sites/samples meeting them is used to estimate the extent of biological degradation in the subwatershed, as well as the extent of physical habitat degradation. For the PSUs sampled in 2009, 2% of the of the B-IBI scores indicated “Good” biological conditions and 26% indicated “Fair” conditions, while 72% of the streams were rated as either “Poor” or “Very Poor”. Habitat measures using the RBP method indicated “Supporting,” “Partially Supporting,” and “Non Supporting” conditions in 18%, 52%, and 30% of sites, respectively. The PHI indicated “Minimally Degraded,” “Partially Degraded,” and “Degraded,” and “Severely Degraded” conditions in 8%, 46%, 34%, and 12% of sites, respectively. Water quality measurements did not reveal temperature or dissolved oxygen values in non-attainment with state standards, though the sampling period did not coincide with the most stressful summer months. Thresholds for specific conductivity have not been established; however, the majority of values fall within normally observed ranges. A mix of stable and unstable channel types were observed during this assessment. Twenty-six percent of reaches assessed were classified as E type channels, considered a stable form. Conversely, 32% were classified as G type channels, a highly unstable form. Lesser amounts of B type (8%), C type (12%) and F type (10%) channels also were observed. All channels had sand-dominated bottoms and nearly all had slopes of much less than 2%. For the E types observed, significant differences in ER, Sinuosity, and W/D ratio were observed when compared to reference reach values for E types in the Western Coastal Plain. Degradation of water quality, rather than physical habitat, is likely affecting biota at a minimum of 26% of sites. iii Acknowledgements The principal authors of this document are Christopher Victoria and Janis Markusic, of Anne Arundel County, and James Stribling and Benjamin Jessup , of Tetra Tech, Inc. and. They were assisted by Tetra Tech staff including Chris Millard, Erik Leppo, Carolina Gallardo, John Roberts, Chad Barbour, Brenda Decker, and Christopher Wharton. Aquatic Resources Center (ARC; Todd Askegaard, principal) completed the primary benthic macroinvertebrate sample sorting and identification; Freshwater Benthic Services (FBS; Michael Winnell, principal) did the QC taxonomic identifications. The appropriate citation for this report is: Victoria, C., J. Markusic, J. Stribling, and B. Jessup. 2011. Aquatic Biological Assessment of the Watersheds of Anne Arundel County, Maryland: 2009. Prepared by: Anne Arundel County Department of Public Works, Watershed and Ecosystem Services, Annapolis, MD, and Tetra Tech, Inc., Center for Ecological Sciences, Owings Mills, MD. For more information about this report, please contact: Christopher Victoria Department of Public Works Watershed, Ecosystem, and Restoration Services Anne Arundel County 2662 Riva Road / MS 7301 Annapolis, Maryland 21401 410.222.4240 [email protected] iv Table of Contents Introduction ..................................................................................................................................... 1 Purpose of Biological and Physical Habitat Assessment ............................................................ 1 Methods........................................................................................................................................... 2 Network Design ........................................................................................................................... 2 Summary of Sampling Design ................................................................................................ 2 Site Selection .......................................................................................................................... 2 Alternate Sites ......................................................................................................................... 4 Field Sampling and Laboratory Processing ................................................................................. 4 Benthic Sampling and Processing ........................................................................................... 4 Benthic Taxonomy .................................................................................................................. 5 Physical Habitat Rating (Methods for Calculation and Scoring)............................................ 5 Water Quality .......................................................................................................................... 5 Geomorphic Assessment ......................................................................................................... 6 Data Analysis ............................................................................................................................... 7 Data Structure ......................................................................................................................... 7 Land Use and Impervious Surface Evaluation........................................................................ 7 Physical Habitat ...................................................................................................................... 7 Biological Index Rating .......................................................................................................... 7 Water Quality .......................................................................................................................... 9 Geomorphic Assessment ......................................................................................................... 9 Rosgen Stream Classification ............................................................................................... 10 Results and Discussion ................................................................................................................. 11 Comparisons among Sampling Units ........................................................................................ 11 Biological Assessment Summary ......................................................................................... 11 Habitat Assessment Summary .............................................................................................. 12 Water Quality Assessment Summary ................................................................................... 12 Geomorphic Assessment Summary ...................................................................................... 13 Primary Sampling Unit Discussions .......................................................................................... 14 Marley Creek (05) ................................................................................................................. 14 Aquatic Habitat ................................................................................................................. 14 Benthic Macroinvertebrates .............................................................................................. 14 Water Quality .................................................................................................................... 14 Geomorphic Assessment ................................................................................................... 14 Lower North River (12) ........................................................................................................ 17 Aquatic Habitat ................................................................................................................. 17 Benthic Macroinvertebrates .............................................................................................