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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

Water temperatures are warming throughout the world including the Pacific Northwest, USA. Benthic macroinvertebrates are one of the most important and widely used indicators of freshwater impairment; however, their response to increased water temperatures and their use for monitoring water temperature impairment has been hindered by lack of knowledge of temperature occurrences, threshold change points, or indicator taxa. We present new analysis of a large macroinvertebrate database provided by Idaho Department of Environmental Quality from wadeable streams in Idaho that is to be used in conjunction with our previous analyses. This new analysis provides threshold change points for over 400 taxa along an increasing temperature gradient and provides a list of statistically important indicator taxa. The macroinvertebrate assemblage temperature change point for the taxa that decreased with increased temperatures was determined to be about 20.5 °C and for the taxa assemblage that increased with increased temperatures was about 11.5 °C. Results of this new analysis combined with our previous analysis will also be useful for others in neighboring regions where these taxa occur.

Nonmetric multidimensional scaling (NMDS) is an ordination technique which is often used for information visualization and exploring similarities or dissimilarities in ecological data. In principle, NMDS maximizes rank-order correlation between distance measures and distance in the ordination space. Ordination points are adjusted in a manner that minimizes stress, where stress is defined as a measure of the discordance between the two kinds of distances. Before and After Control Impact (BACI) is a classical analysis of variance method for measuring the potential influence of an environmental disturbance. Such effects can be assessed by comparing conditions before and after a planned activity. In certain ecological applications, the extent of the impact is also expressed relative to conditions in a control area, after a particular anthropogenic activity has occurred. In this paper, two statistical techniques are employed to investigate the effects of stream nutrient addition on a riverine benthic macroinvertebrate community. The clustering of sampling units, based on multiple macroinvertebrate metrics across pre-determined river zones, is explored using NMDS. BACI is subsequently used to test for the potential impact of nutrient addition on the specified macroinvertebrate response metrics. The combination of the two approaches provides a powerful and sensitive tool for detecting complex second-order effects in river food chains. Statistical techniques are demonstrated using eight years of benthic macroinvertebrate survey data collected on an ultra-oligotrophic reach of the Kootenai River in Northern Idaho and Western Montana downstream from a hydro-electric dam.