Ecological Profiles of Caddisfly Larvae in Mediterranean Streams
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Environmental Pollution 132 (2004) 509–521 www.elsevier.com/locate/envpol Ecological profiles of caddisfly larvae in Mediterranean streams: implications for bioassessment methods N. Bonadaa,*, C. Zamora-Mun˜ ozb, M. Rieradevalla, N. Prata aDepartment of Ecology, University of Barcelona, Diagonal 645, E-08028 Barcelona, Spain bDepartment of Animal Biology and Ecology, University of Granada, E-18071 Granada, Spain ‘‘Capsule’’: Ecological profiles of caddisfly larvae in Mediterranean streams using water quality variables. Abstract Caddisflies are a well represented group with high species diversity in Mediterranean climate rivers. Although they are widely used in water quality assessment, little is known of the ecological profiles of families or species. We present a simple score for ecological profiles which measures intolerance to water quality. The ecological profiles of caddisflies are diverse and the degree of tolerance at the family level is related to species diversity and the tolerance of individual species to water quality. Comparisons with the scores used in the biotic index IBMWP show general agreement between the degree of intolerance of a family and its score in the IBMWP, with few exceptions. Studies on tolerance are required to elucidate the autecology of taxa, and to develop biological indices, especially in areas with high species diversity. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Trichoptera; Stream ecology; Tolerance; Water quality; Biological index 1. Introduction environmental gradient follows a unimodal distribution (Whittaker, 1967), have been developed to estimate taxa To predict and determine species distributions and optima and tolerances in relation to environmental abundances, and to assess disturbance in ecosystems, variables (e.g. ter Braak and Looman, 1986; ter Braak freshwater ecologists need to study the relationships and Van Dam, 1989). These methods have been between organisms and environmental variables. Species extensively used in Paleolimnology to infer past are considered tolerant when found in a wide range of environmental conditions (e.g. ter Braak and Van environmental conditions and intolerant when they are Dam, 1989; Birks et al., 1990; Bigler and Hall, 2002). restricted to a small window of ecological conditions Although multivariate models designed to assess water (e.g. see Cairns and Pratt, 1993). Organisms are often quality (e.g. RIVPACS, AusRivAS) involve the quan- considered tolerant or sensitive to pollution without tification of the ecological requirements of macro- detailed studies on their ability to thrive in polluted invertebrate communities (Wright, 1995; Smith et al., waters, and reports on the tolerance of individual species 1999), few studies, however, report the specific toler- to environmental variables are scarce (Verdonschot and ances of macroinvertebrate taxa (but see Verdonschot Higler, 1992; Lenat and Resh, 2001). and Higler, 1992). Several statistical procedures, based on the hypo- Ecological profiles for macroinvertebrate taxa are thesis that the abundance of organisms along an required to test the effectiveness of biological indices, to determine indicator species and to obtain autecological * Corresponding author. Fax: C34 93 4111438. information from environmental conditions (Moretti E-mail address: [email protected] (N. Bonada). and Mearelli, 1981). Indicator species have specific 0269-7491/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2004.05.006 510 N. Bonada et al. / Environmental Pollution 132 (2004) 509–521 requirements for several variables (Johnson et al., 1993) human impact (Prat and Ward, 1994) which involves that can vary at a higher taxonomic resolution (Resh a variety of river reaches with distinct water quality that and Unzicker, 1975; Cranston, 1990) and so several can broaden the tolerance range of caddisflies. authors have suggested caution in the use of higher taxonomic levels, like families, in bioassessment meth- ods (e.g. Moog and Chovarec, 2000). Nowadays, the 2. Materials and methods taxonomic level to be used in applied studies raises controversy because the ecological patterns of species 2.1. Sampling sites and procedure and families can differ (Furse et al., 1984; Marchant, 1990; Rutt et al., 1993; Zamora-Mun˜ oz and Alba- One hundred and forty sampling sites were surveyed Tercedor, 1996; Hewlett, 2000). along the Spanish Mediterranean coast seasonally in At the family, species and individual levels, Trichop- 1999 and in 2000 (Fig. 1). Sites were more or less equally tera has been regarded as an appropriate group to assess distributed among 10 river basins, and they included water quality using larvae (e.g. see Resh, 1992) or adults reference and non-reference sites. Selected sampling sites (Malicky, 1981; Usseglio-Polatera and Bournaud, 1989). account for almost all river types present along the At the family and species levels, caddisflies have been Spanish Mediterranean coast in terms of flow, river size, related to several environmental variables and display riparian characteristics, geology and water quality some specific trends in ecological requirements (e.g. (Bonada et al., 2002; Robles et al., 2002). Macro- Basaguren and Orive, 1990; Dohet, 2002; Dohet et al., invertebrate samples were collected in riffles and pools 2002) but their tolerance ranges need to be qualified to with a kick-net of 250 mm mesh size. They were various environmental or chemical variables. Caddisfly preserved in alcohol 70% and sorted in the laboratory. ecological profiles can be obtained from studies analyz- Caddisfly taxa were sorted and identified at the maximal ing deformities and anomalies caused by pollution (e.g. possible level, and the rank of abundances was recorded Petersen and Petersen, 1983; Vuori and Kukkonen, for each taxon: 1 for 1–3 individuals, 2 for 4–10, 3 for 2002) and asymmetries (Bonada and Williams, 2002), or 11–100 and 4 for more than 100 individuals. Given the else from toxicity tests (Greve et al., 1998), which may large amount of undescribed larvae in the Iberian allow us to infer optima and tolerances for a single Peninsula (Vieira-Lanero, 2000), we could not identify species and one or a few variables. On the other hand, all taxa to the species level with certainty. When studies performed using large sets of field data including possible, pupae and adults were collected in the field several species are also useful (e.g. Gordon and Wallace, to corroborate larval identifications. In some cases 1975; Moretti and Mearelli, 1981; Basaguren and Orive, mature larvae were reared in the laboratory in some 1990; Verdonschot and Higler, 1992; Stuijfzand et al., cases using a system developed by Vieira-Lanero (1996). 1999). However, most of these studies are usually A database was assembled with records of caddisfly taxa performed in small areas, with insufficient data, or identified at the family and genus or species level without taking into account the abundance of organ- collected from all sites in all sampling seasons. From isms, and thereby caution should be taken when this database, only taxa collected in at least 10 samples extrapolating these results to other geographical areas (sites ! seasons) were used to check for tolerances to or for other taxonomic levels. various environmental variables, whereas the most The ecological profiles of caddisflies were obtained infrequent taxa were removed (Beraeidae, Calamocer- from studies in streams along the Iberian Mediterranean atidae, Ecnomidae and Goeridae). In total, we used 13 coast. The caddisflies in this area are an ideal group to families and 41 taxa at the genus or species level that study ecological profiles from the perspective of water were collected (Appendix). quality variables owing to four factors. First, the high The environmental variables considered in this study species diversity and endemicity of caddisflies in the were oxygen (mg/l), conductivity (mS/cm) (both directly Iberian Peninsula with a total of 390 species present (see measured in the field), ammonium (mg/l), P-phosphates updated checklist of Trichoptera from Iberian Peninsula (mg/l), suspended solids (mg/l), sulphates (mg/l) and in http://www.fauna-iberica.mncn.csic.es/), are the result chloride (mg/l) (which were analyzed in the laboratory). of the interactions between ecological and historical factors (Gonza´lez et al., 1987). Second, the harsh natural 2.2. Data analysis abiotic conditions in these Mediterranean ecosystems (see Gasith and Resh, 1999), which would influence the To calculate the tolerance levels for all caddisflies (13 high diversification of the ecological profiles of trichop- families and 41 genera/species) using the physico- terans. Third, the lack of information about autecology chemical data obtained at each sampling site and during studies of caddisflies in Mediterranean areas, except each season, a weighted average (WA) approach was those provided in taxonomic papers. Finally, the performed with the CALIBRATE vs 0.7 program significant river alteration in the Mediterranean area by (Juggins, 1997). The WA approach assumes that each N. Bonada et al. / Environmental Pollution 132 (2004) 509–521 511 Pyrenees FRANCE Besòs Basin SPAIN Llobregat Basin Mediterranean Sea Ranges Iberian Sampling site Mijares Basin Mountain ranges Turia Basin Júcar Basin Segura Basin Sierra Nevada Almanzora Basin Aguas Basin Adra Basin Guadalfeo Basin Fig. 1. River basins and sampling sites in Mediterranean Spanish areas where caddisflies were collected. taxon has a Gaussian response to an environmental