A total of 153 sites from R1 and 252 sites from R2 for 405 core repeat sites will be sampled in Round Four.
The sample design for the repeat sites from R1 will follow the R1 design of random selection of stream reaches from strata defined by basin and stream order, specifically equal probability of selection in 1st, 2nd, and 3rd order streams within each of 17 basins statewide. Three repeat sites will be randomly selected from the R1 sites in each stratum, where possible (some strata have low numbers of R1 sites to select from).
The sample design for the repeat sites from R2 will follow the R2 design of random selection of stream reaches from Primary Sampling Units (PSUs) that generally equate to Maryland 8-digit watersheds (which are combined when they are small to make 84 PSUs statewide). Three repeat sites will be randomly selected from the R2 sites in each PSU.
Given that R1 and R2 used different sample designs and stream network map scales (R1 sites were selected from a 1:250,000-scale map and R2 sites were selected from a 1:100,000-scale map), the inter-round comparison of repeated samples will be conducted separately for each round. The R1 comparison will be a 20-year comparison; the R2 comparison will be a 14-year comparison. Each of these inter-round comparisons will have the ability to detect a stream ecological condition change of 0.20-0.25 BIBI units with 80% probability.
Mattawoman Creek Watershed Intensification
To increase the density of samples in Mattawoman Creek, a watershed of special interest, all sites sampled in this watershed in R1 and R2 will be repeat sampled in Round Four. Specifically, the 7 sites sampled for R1 in 1995 will be repeat sampled in 2015, while all 10 sites sampled for R2 in 2000 will be repeat sampled in 2014.
To obtain site access permissions, landowners for the first 10 sites per strata randomly selected for Round Four from R1 and R2 will be identified and letters requesting permission will be mailed. The goal will be to obtain permissions for twice the number of sites to be sampled per stratum (i.e., 2x3=6) and to provide them to DNR.
Additions and Modification to Sampling and Assessment Protocols
The Round Four MBSS will sample the same parameters sampled during R3, with one addition and one modification. Geomorphological assessments will be added. This addition will consist of a rapid assessment of geomorphology at randomly-selected Round Four sampling sites (exact protocols to be determined) and detailed geomorphological assessments (consisting of cross-sections, longitudinal profiles, and pebble counts) at all MBSS Sentinel Sites. By increasing the time and area searched, the stream salamander sampling protocol has been modified from R3 to provide a greater likelihood of collecting stream salamanders. The goal is to support the development of a salamander index of biotic integrity, a biological indicator that will be especially useful in small headwater streams with naturally depauperate fish assemblages. More detailed descriptions of these Round Four sampling protocols will be included in an updated version of the MBSS sampling manual, scheduled for completion by February 2014.