The Multihabitat Approach of USEPA's Rapid Bioassessment Protocols: Benthic MacroinvertebratesThe multihabitat approach to sampling for bioassessment is not a new concept, but has been described in detail in the USEPA Rapid Bioassessment Protocols (Barbour et al., 1999) and the AQEM project of the European Union (Hering et al., 2004). Although there are variations on this technique, the basic approach is to sample the major aquatic habitats in proportion to each representation in the stream reach. Both fish and benthic macroinvertebrates are sampled in this manner. The primary advantage of the multihabitat approach is to sample representative stream habitats that will address habitat altered systems and provide an indication of impairment from both chemical and non-chemical stressors. This technique has been shown to collect representative samples of the stream reach and to be highly precise among and within sampling crews. Four questions are addressed in this paper: (1) What are the strengths and limitations of the method for low-gradient streams; (2) What are the performance characteristics (i.e., accuracy, precision, sensitivity) of the method; (3) What is the relative ability of the method to distinguish natural variability (i.e., temporal, spatial) from human disturbance; (4) How would the method be implemented for low-gradient streams.

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There is increasing international interest by water resource management agencies worldwide in developing the capacity for quantitative bioassessments of boatable rivers. This interest stems from legal mandates requiring assessments, plus growing recognition of the threats to such systems from multiple and co-varying stressors (e.g. chemical pollutants, physical habitat alterations, altered flow regimes, channel modifications and alien species). The elevated cost and inefficiencies of jurisdictionally-and taxonomicallysegregated assessments is widely recognized, as is the desire to obtain comparable data that can be easily shared among political jurisdictions and ecological regions. The objectives, sampling methods, indicators, site-scale sampling designs and geographic extent of the resources being sampled differ among programmes, thereby limiting such data exchanges. Our objective in this paper is to review major biological assessment design alternatives for boatable rivers, with special attention given to the sample site length from which data are collected. We suggest that sufficient site length determinations should be based on the survey objectives, the relative heterogeneity of the habitat template, and the quality of data necessary for meeting programmatic data quality objectives. Future sampling effort studies should be designed to allow separate samples of several short sub-sites at many diverse sites to generate multiple data points for each site. Data from those multiple sub-sites should be analysed using randomization-based data evaluation methods. We hope that our recommendations will be useful to the maximum number of institutions, including those with limited funds and a purely local focus, as well as those responsible for sampling at continental geographic extents.

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BRIDGES BRIDGES is a recurring feature of J-NABS intended to provide a forum for the interchange of ideas and information between basic and applied researchers in benthic science. Articles in this series will focus on topical research areas and linkages between basic and applied aspects of research, monitoring, policy, and education.Readers with ideas for topics should contact Associate Editors, Nick Aumen and Marty Gurtz.In this article, Stribling et al. discuss data quality issues to be considered when conducting taxonomic analyses for biological assessments. They differentiate between 2 broad areas of taxonomy-research and production taxonomic investigations-and consider how approaches to organism identification can vary between these 2 areas. The authors stress the importance of evaluating and communicating data quality, and that knowledge of quality assurance/quality control elements is essential before drawing conclusions from biological assessment results.Nick Aumen, nickaumen@nps.gov Marty Gurtz, megurtz@usgs.gov