Reduction of sampling effort assessing macroinvertebrate assemblages for biomonitoring of rivers

Knowledge and Management of Aquatic Ecosystems (2015) 416, 08 c ONEMA, 2015  DOI: 10.1051/kmae/2015004 http://www.kmae-journal.org Reduction of sampling effort assessing macroinvertebrate assemblages for biomonitoring of rivers B. Gartzia De Bikuña(1) , E. López(1) , J.M. Leonardo(1) , J. Arrate(1) , A. Martínez(1) ,(2), , A. Agirre(1) , A. Manzanos(3) Received October 2, 2014 Revised January 13, 2015 Accepted January 28, 2015 ABSTRACT Key-words: stream invertebrates, effort reduction, biomonitoring Biomonitoring methods based on macroinvertebrate assemblages are widely developed in streams and rivers. However, the use of invertebrates has been criticized due to the long time and expense of processing samples. Therefore, we evaluated the effectiveness of reducing the sampling effort from 20 to 5 samples to assess the stream macroinvertebrate community. In six streams in the Basque Country (North of Spain) 20 kick nets were collected following a multihabitat stratified sampling design. The macroinvertebrates were identified to family level and a smoothed family accumulation curve fitting the Clench function to the data was calculated for each stream. Richness was lower in 5 than in 20 samples. However, in general, the percentage of richness estimated with the subsampling may be considered representative of the existing taxa richness. Therefore, the study of five samples may be adequate for biomonitoring Basque streams, greatly minimizing time, effort and costs. RÉSUMÉ Réduction de l’effort d’échantillonnage pour l’évaluation des assemblages de macroinvertébrés pour la biosurveillance des rivières Mots-clés : invertébrés, cours d’eau, réduction de l’effort, biosurveillance Les méthodes de biosurveillance basées sur les assemblages de macroinvertébrés sont largement développées dans les ruisseaux et rivières. Cependant, l’utilisation d’invertébrés a été critiquée en raison du long temps de collecte et du coût de traitement des échantillons. Par conséquent, nous avons évalué l’efficacité de la réduction de l’effort d’échantillonnage de 20 à 5 échantillons pour évaluer la communauté des macroinvertébrés d’une rivière. En six rivières du Pays Basque (nord de l’Espagne) 20 filets à main Kicker ont été recueillis suivant un plan d’échantillonnage stratifié multihabitat. Les macroinvertébrés ont été identifiés au niveau de la famille et une courbe de cumul de famille lissée de la fonction de Clench ajustée aux données a été calculée pour chaque rivière. La richesse était plus faible dans 5 échantillons que dans 20. Cependant, en général, le pourcentage de la richesse estimée avec le sous-échantillonnage peut être considéré comme représentatif de la richesse des taxons existants. Par conséquent, l’étude de cinq échantillons peut être adéquate pour la biosurveillance des rivières basques, minimisant considérablement les efforts de temps et les coûts. (1) Anbiotek S.L. Axpe Industrialdea, Ribera de Axpe 11 B-201, 48950 Erandio, Spain (2) Laboratory of Stream Ecology, Department of Plant Biology and Ecology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain (3) URA. Agencia Vasca del Agua. C/ Orio, 1-3, 01010 Vitoria-Gasteiz, Spain  Corresponding author: Article published by EDP Sciences B. Gartzia De Bikuña et al.: Knowl. Manag. Aquat. Ecosyst. (2015) 416, 08 INTRODUCTION Streams and rivers are among the most threatened habitats in the world (Malmqvist and Rundle, 2002). Since they provide important ecosystem services (Thorp et al., 2010), it is crucial to understand the consequences of human perturbations on these ecosystems to preserve or restore their integrity (Meybeck, 2003). Therefore, assessment and biomonitoring programs are carried out widely by public authorities. In river biomonitoring, the aquatic macroinvertebrates are the most commonly studied group (Bonada et al., 2006) since they are sensitive to multiple ecological alterations (Johnson and Ringler, 2014). In particular, taxa richness has been widely used because it is a key measurement to assess the structure of biological assemblages (Gotelli and Cowell, 2001). However, the use of invertebrates has been criticized due to the long time and expensive costs of sampling, sorting, counting and identifying them (Ciborowski, 1991). Therefore, since the effectiveness of biomonitoring protocols depends mainly on the time required and on the overall costs, techniques that optimize the cost-benefit have been developed (Marini et al., 2013; Pinna et al., 2013, 2014). Nevertheless, caution is needed since the technique and the way in which samples are collected and processed may influence the description of the studied community (Boonsoong et al., 2009; Di Sabatino et al., 2014). In fact, reducing effort and costs is not the only aim of subsampling methods, but also of paramount concern is the need to gain information not substantially biased by the procedure and capable of answering research questions (Barbour and Gerritsen 1996). In Spain, as in other states in Europe, the methodology focused on benthic macroinvertebrates established by the Water Framework Directive, WFD (EU, 2000), for river biomonitoring is multihabitat stratified sampling (Barbour et al., 1999; AQEM, 2002). However, the large number of kick samples required in each stream increases the time, effort and costs, making the application of this approach in programs with a great number of monitored systems nearly impossible. Therefore, the goal of this work is to test if a significant reduction in the sampling effort from 20 to 5 samples, that would minimize time, effort and costs, allows for the collection of representative information about the richness of macroinvertebrate communities for biomonitoring. MATERIALS AND METHODS > STUDY SITE The study was conducted in six streams in the Basque Country (North of Spain) flowing into the Atlantic Ocean. The study sites differ in the basin area, but not in the water physicochemical characteristics. The main land uses of the catchments are native vegetation, conifer plantations and farming, percentages varying among sites (Table I). The climate in this region is oceanic, with cool winters (mean winter temperature around 9 ◦ C) and warm summers (mean summer temperature around 21 ◦ C), and with a mean annual rainfall of 1000−1200 mm, evenly distributed throughout the year. > FIELD PROCEDURES Benthic macroinvertebrates were sampled in late spring 2012 in three of the six streams (S1, S2, S3) and in late spring 2013 in the other three (S4, S5, S6). At each site, multihabitat, stratified and semiquantitative sampling was carried out, collecting 20 kick nets (25 × 20.5 cm; 500 µm) within a 100-m-long reach (Barbour et al., 1999; AQEM, 2002). With each kick an estimated stream bottom area of 0.05 m2 (semiquantitative) was sampled. The habitats that represented 5% of the total surface were sampled (multihabitat). The number of samples taken in each habitat depended on the percentage th (...truncated)