Trefor B. Reynoldson

The reference condition: a comparison of multimetric and multivariate approaches to assess water-quality impairment using benthic macroinvertebrates

Traditional methods of establishing control sites in field-oriented biomonitoring studies of water quality are limited. The reference-condition approach offers a powerful alternative because sites serve as replicates rather than the multiple collections within sites that are the replicates in traditional designs using inferential statistics. With the reference-condition approach, an array of reference sites characterises the biological condition of a region; a test site is then compared to an appropriate subset of the reference sites, or to all the reference sites with probability weightings. This paper compares the procedures for establishing reference conditions, and assesses the strengths and deficiencies of multimetric (as used in the USA) and multivariate methods (as used in the UK, Canada, and Australia) for establishing water-quality status. A data set of environmental measurements and macroinvertebrate collections from the Fraser River, British Columbia, was used in the comparison. Precision and accuracy of the 2 multivariate methods tested (AUStralian RIVer Assessment Scheme: AusRivAS, BEnthic Assessment of SedimenT: BEAST) were consistently higher than for the multimetric assessment. Classification by ecoregion, stream order, and biotic group yielded precisions of 100% for the AusRivAS, 80-100% for the BEAST, and 40-80% for multimetrics; and accuracies of 100%, 100%, and 38-88%, respectively. Multimetrics are attractive because they produce a single score that is comparable to a target value and they include ecological information. However, not all information collected is used, metrics are often redundant in a combination index, errors can be compounded, and it is difficult to acquire current procedures. Multivariate methods are attractive because they require no prior assumptions either in creating groups out of reference sites or in comparing test sites with reference groups. However, potential users may be discouraged by the complexity of initial model construction. The complementary emphases in the multivariate methods examined (presence / absence in AusRivAS cf. abundance in BEAST) lead us to recommend that they be used together, and in conjunction with, multimetric studies.

Taxonomic resolution of benthic macroinvertebrate communities in bioassessments

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 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. The issue of taxonomic resolution has been a topic of interest in benthological studies for a long time, but the increasing use of aquatic insects—and more recently algae—in assessing water quality has heightened the importance of understanding the tradeoffs associated with different levels of taxonomy. Bailey and co-authors lead off this set of papers with a review of the types of studies and questions for which species identifications are essential, but then examine whether there are circumstances—e.g., in some bioassessments—in which taxonomic information at a higher (e.g., family) level is sufficient, or may even be better. They propose a 2-tiered approach for taxonomy used in bioassessment studies: family-level identifications for multivariate analyses or index calculation, and species identification for a short list of indicator taxa that are appropriate for a particular study. Lenat and Resh review a variety of uses of taxonomic information for aquatic insects and recommend levels of taxonomy that are appropriate for different situations. They conclude that biological monitoring studies yield the greatest benefits using genus- or species-level taxonomy. Hill et al. examine issues of taxonomic resolution for diatom studies, using results from a large set of diatom assemblage data collected from 199 streams over a 3-y period. They found that genus-level taxonomy appears to adequately describe the response of some diatom assemblage attributes to environmental gradients, especially for those gradients that involve morphological (motility) or physiological (pH tolerance) adaptations that are related to evolved genus-level characteristics. Nick Aumen, nick_aumen@nps.gov Marty Gurtz, megurtz@usgs.gov Co-editors

A comparison of reproduction, growth and acute toxicity in two populations of Tubifex tubifex (Müller, 1774) from the North American Great Lakes and Northern Spain

Reproduction in Tubifex tubifex is being used as part of a suite of indicators of sediment toxicity in Canada and Spain, and reproduction of T. tubifex is being considered as a component of sediment objectives for environmental regulation and clean-up in the Canadian Great Lakes. The data being used to set these reproductive targets have been developed from a single culture of T. tubifex from Lake Erie. The plasticity of this particular species is well known and before it can be adopted widely as a test organism it is necessary to determine whether a single culture source should be used or if cultures derived from different populations respond similarly. A series of experiments with two cultures, one from Lake Erie the second from a small mountain stream in Northern Spain have shown that the Spanish worms appear to produce fewer cocoons per adult (mean 8.6 S.D. 1.0) than those from Lake Erie (mean 10.4 S.D. 0.3) at 22.5 °C, a standard test temperature. The number of young produced per adult by the Spanish culture is also lower (mean 19.0 S.D. 4.6) than the L. Erie population (mean 30.6 S.D. 2.3), however, the Spanish population has higher reproductions rates at a lower temperature. The Spanish worms also have lower and more variable growth rates than the Canadian population. There also appear to be slight differences in the sensitivities to toxicants, with the Canadian worms having higher LC50s for copper, chromium and cadmium. While there are differences in the responses in the two cultures these are not considered to be sufficient to invalidate the use of either population in a standard bioassay protocol as long as appropriate calibration and validation are undertaken.

The Pollution Biology of Aquatic Oligochaetes

The pollution biology of aquatic oligochaetes / , The pollution biology of aquatic oligochaetes / , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

A predictive model for freshwater bioassessment (Mondego River, Portugal)

We sampled macroinvertebrates at 75 locations in the Mondego river catchment, Central Portugal, and developed a predictive model for water quality assessment of this basin, based on the Reference Condition Approach. Sampling was done from June to September 2001. Fifty-five sites were identified as “Reference sites” and 20 sites were used as “Test sites” to test the model. At each site we also measured 40 habitat variables to characterize water physics and chemistry, habitat type, land use, stream hydrology and geographic location. Macroinvertebrates were generally identified to species or genus level; a total of 207 taxa were found. By Unweighted Pair Group Method with Arithmetic mean (UPGMA) clustering and analysis of species contribution to similarities percentage (SIMPER), two groups of reference sites were established. Using Discriminant Analysis (stepwise forward), four variables correctly predicted 78% of the reference sites to the appropriate group: stream order, pool quality, substrate quality and current velocity. Test sites’ environmental quality was established from their relative distance to reference sites, in MDS ordination space, using a series of bands (BEAST methodology). The model performed well at upstream sites, but at downstream sites it was compromised by the lack of reference sites. As with the English RIVPACS predictive model, the Mondego model should be continually improved with the addition of new reference sites. The adaptation of the Mondego model methodology to the Water Framework Directive is possible and would consist mainly of the integration of the WFD typology and increasing the number of ellipses that define quality bands.

Bioassessment of Freshwater Ecosystems

Freshwater ecosystems have a primary role in the biosphere as conduits of water and nutrients from the continents to the sea. They also support unique and complex ecological communities and often define the structure and functioning of the surrounding terrestrial ecosystem. Because of this, and the critical role of fresh water as a human resource, ecologists are often asked to assess or monitor the “health”, “status” or “condition” of freshwater ecosystems.

The biological assessment of contaminated sediments — the Detroit River example

Contaminated sediments have been found in almost all water bodies which have at some time received, or are presently receiving, waste inputs from urban and industrial sources. In the Laurentian Great Lakes, sediments are classified as contaminated from bulk chemical analysis. The chemical criteria used to evaluate these results are somewhat arbitrary and only partially consider biological impacts. The absence of adequate linkage among sediment contamination, bioavailability, effects on organisms, populations, and ultimately ecosystem health, represents a major barrier to the restoration and protection of aquatic ecosystems.

Toxicity of Santander Bay sediments to the euryhaline freshwater oligochaete Limnodrilus hoffmeisteri

The freshwater euryhaline oligochaete Limnodrilus hoffmeisteri was selected for use in bioassays with polluted sediment from Santander Bay. It is easy to culture; is tolerant of low to moderate, up to 15‰, salinity; and is common in oligohaline conditions in European and North American estuaries. Worms were collected from an estuarine population and kept in unpolluted sediment for between 2 and 4 weeks, under laboratory conditions, at 7–8.5‰ salinity and 22.5 °C. Sediment from different sites in Santander Bay were sieved through 250 μm mesh and adjusted to a salinity of approx. 7‰ prior to the bioassays, either by adding sea water or dechlorinated tap water to the overlying water. High levels of ammonia in some sediment, which may confound results in ecotoxicity bioassays, were reduced by oxidation of the sediments in shallow trays. Sediment bioassays were performed with sexually mature Limnodrilus hoffmeisteri worms in 250-ml beakers, with a 1:3 ratio of sediment:water and 4 worms per baker. Endpoints in the 14-day bioassay were % mortality, adult final biomass, % adults that have shown resorption of the clitellum, number of cocoons, and burrowing behaviour. It was possible to rank the sites according to their toxicity using both mortality rates and sublethal effects. The control site had the following values for the endpoints: 5% mortality, ( \(\overline{x}\pm {\rm sd}\)) 2.40 ± 1.52 cocoons per beaker and 1.271 ± 0.470 mg dw adult final biomass. The most toxic sediment resulted in 65% mortality, resorption of the clitellum in 67% of the adults, no production of cocoons and a low final biomass (\(\overline{x}\pm {\rm sd}\)=0.681 ± 0.489 mg dw per adult). A second site had high mortality (60%) and no reproduction, although resorption of the clitellum did not occur in surviving animals. The remaining sites showed similar mortality (35–42%), and at only one of them was low reproduction observed (0.8 ± 0.447 cocoons per beaker). Behavioural effects, measured as length of galleries in a fixed area of the test-vessel at the end of the bioassay, were significant compared with control at only one site. Multivariate analysis showed the mortality gradient to be the strongest, with a second unassociated gradient representing clitellum resorption. The mortality gradient was associated with Cu and Zn concentration, and PAH and Pb possibly with resorption.

Performance of the standard CABIN method: comparison of BEAST models and error rates to detect simulated degradation from multiple data sets

Abstract: The objective of this study was to evaluate the performance of 3 bioassessment models for reference data sets collected from the Australia Capital Territory (ACT), the Yukon River Basin (YT), and the Laurentian Great Lakes (GL) built following the standard Canadian Aquatic Biomonitoring Network (CABIN) method. To evaluate the models, we used validation reference-site data, which were artificially impaired to simulate 3 levels of eutrophication by varying the proportions of sensitive, intermediate, and tolerant taxa. Models correctly classified 56 to 62% of reference sites. Type 1 errors (assessing reference sites as degraded) were high for all data sets and ranged from 30 to 75%, in part because the biological communities of the validation sites extended to or beyond the range of the reference-site data used to build the models. Capturing the full range of ecological variation with adequate sample size is critical for reference-condition approach (RCA)-type models. Type 2 errors (assessing degraded sites as in reference condition) varied greatly among data sets and for each reference group within each data set. Resource managers must carefully consider the risks associated with making errors. Thus, standard methods for quality assurance of assessment models should include simulated data so that error rates and adjusted assessment thresholds can be reported to ensure that degradation can be detected and that undisturbed sites are not mistakenly subjected to unnecessary management action.

A tiered method for discriminant function analysis models for the Reference Condition Approach: model performance and assessment

Abstract: Reference Condition Approach (RCA) predictive models are used to assess a test site against reference sites probabilistically matched based on habitat. These models are the basis of several major national stream bioassessment programs in the UK, Australia, and Canada. In the usual approach to developing predictive models, discriminant function analysis (DFA) is used to assign a test site to a group of matched reference sites. These groups typically are established by classification of a macroinvertebrate assemblage and matched to the habitat attributes in a single-step DFA model. We examined an alternative to standard DFA in which a series of tiered models are used. This tiered method constructs a model for the 1st division in a hierarchical classification, and then develops models for each further step in the hierarchical classification. We examined the method with 3 training and validation data sets. Validation data consisted of data from reference sites and those same sites after they underwent simulated impairment. We compared the tiered approach to the standard approach based on prediction accuracy and Type 1 and Type 2 error rates for each data set. The tiered DFA models were similar to or slightly better than the standard single-step DFA models in correctly matching validation sites to reference groups, but this improvement in accuracy did not necessarily translate into improved bioassessment error rates.