MARINE ENVIRONMENTAL RESEARCH Marine Environmental Research 59 (2005) 1–18 www.elsevier.com/locate/marenvrev Effects of copper mine tailings disposal on littoral meiofaunal assemblages in the Atacama region of northern Chile Matthew R. Lee *, Juan A. Correa Departamento de Ecologıa and Center for Advanced Studies in Ecology and Biodiversity, Facultad de Ciencias Biologicas, Pontificia Universidad Catolica de Chile, Alameda 340, Santiago, Chile Received 10 October 2003; accepted 20 January 2004 Abstract The effects of the disposal of copper mine tailings on the littoral meiofaunal assemblages of the Cha~ naral area of northern Chile were studied. Of the metals data collected, only in the case of copper was there a clear association with the tailings distribution in both the seawater and porewater samples, and it is assumed that the tailings on the beaches was the source of copper in the adjacent seawater. When compared to the reference sites, the meiofaunal assemblages at the impacted sites had significantly lower densities and taxa diversities; at the northern sites only the densities were lower. Otoplanid turbellarians were identified as characteristic of those beaches impacted by tailings. The combination of porewater copper and the amount of tailings present were identified as mostly responsible for the observed structure of the meiofaunal assemblages. It was also established that the variation in natural sediment grain size from beach to beach was not a significant factor in the observed differences in the meiofaunal assemblages. The two groups of meiofauna that proved to be most sensitive to the effects of tailings dumping were the foraminiferans and the harpacticoid copepods. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Meiofauna; High-energy sandy beaches; Tailings; Metals; Copper; Chile * Corresponding author. Present address: 11 Briar Drive Heswall, Wirral, Merseyside CH60 5RW, UK. E-mail address: [email protected] (M.R. Lee). 0141-1136/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.marenvres.2004.01.002 2 M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 1. Introduction The effects of contaminating discharges on marine ecosystems are studied, in most industrialised countries, around estuarine or harbour environments and the chosen organisms are frequently the abundant sediment dwelling macrofauna (e.g. Boening, 1999; Gren, Destouni, & Scharin, 2000; Stark, 1998). The discharge of contaminants affecting high-energy sandy beaches is less common and consequently, studies of the effects on the resident biota of this environment are scarce (Barros, 2001; Castilla, 1983; Watling & Watling, 1983). The nature of the sediments in estuarine and highenergy sandy beaches are significantly different. In the estuarine environment the sediments are usually fine with high concentrations of organic material and low oxygen regimes, where as, in high-energy sandy beaches they are coarser, with low concentrations of organic material and high oxygen regimes (McLachlan, 1983; McLachlan & Turner, 1994). The importance of these features is considerable, as they have a significant effect in determining both, the resident biota and the availability of the contaminants to the biota (Chapman, Wang, Janssen, Persoone, & Allen, 1998). It is therefore highly questionable to take the information gained by studies of the effects of contaminants on the estuarine sedimentary environment and apply it to the high-energy sandy beach environment. To address this problem specific studies examining the effects of contaminants on high-energy sandy beaches are required. When compared to the low-energy sedimentary environment, the macrofaunal diversity of Chilean high-energy sandy beaches is low, typically between one and ten species (Jaramillo, 1994; Jaramillo, McLachlan, & Coetzee, 1993) depending on the physical nature of the beach. These macrofaunal species also have a pelagic dispersal phase in their life-cycles which means that larvae, usually the most sensitive stage, are not exposed to the contaminants in the sediment. This, combined with recruitment derived from populations outside the affected area, can serve to mask the impact that the contaminants have on the littoral environment. In this study we therefore chose to use the meiofauna which are highly diverse and do not, as a rule, have a pelagic dispersal phase. The diversity of meiofauna present provides a wide range of physiological responses and, therefore, a better understanding of the true impact of the contaminant. The many other advantages of meiofauna in these types of studies are reviewed by Coull and Chandler (1992). The situation in the Cha~ naral area (26°20:50 S, 070°37:40 W) of northern Chile provides an ideal situation for a natural experiment on the impact of tailings dumping in isolation. Due to the desert nature of this area other forms of contamination, such as industrial and agricultural effluents, are absent. The dumping of copper mine tailings into the coastal environment around Cha~ naral has taken place since 1938 (Castilla & Correa, 1997). Initially the untreated tailings were dumped into Cha~ naral Bay where a large beach composed entirely of tailings formed, the dotted line in Fig. 1 indicates the approximate position of the original coastline. In the mid 1970s the tailings were diverted to a new dumping point, approximately ten kilometres to the north of Cha~ naral, again a large tailings beach formed north of the dumping point. In 1990 a tailings settlement dam was constructed inland where the M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 3 Fig. 1. A map of Chile indicating Cha~ naral (a) and showing the locations of the sampling sites (b) the northern and central sites, (c) the reference sites. The dashed line in (b) indicates the approximate position of the original coastline. solid component of the tailings is allowed to settle out before the tailings water, ‘clear water’ tailings, continues on to the coast. The objective of this study was therefore to examine the effects of the copper mine tailings disposal on the littoral meiofaunal assemblages of the area and to identify those meiofaunal groups which could act as indicators of copper pollution. 2. Material and methods Samples were collected from sites in the Cha~ naral area of northern Chile on ten occasions between January 1997 and March 2000. Five replicate samples, each of 50 cm3 in volume (depth 75 mm), were collected from each site using a 60 cm3 plastic 4 M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 syringe modified to form a quantitative piston corer. Samples were collected from the surf zone on the lower portion of the beach, the zone of retention, at or around low tide. Collection was at random and parallel to the shore line. Each sample was placed in a 100 cm3 plastic bottle with approximately 50 cm3 of 10% formalin solution, shaken, sealed and then returned to the laboratory for processing. Samples were collected from twelve sites covering the range of sediment and morphodynamic types occurring in the area (See Table 1 for site descriptions, and Fig. 1 for locations). These sites were subdivided a priori into three groups. The first group were the reference sites Playa Zenteno, Torres del Inca and Las Piscinas (Fig. 1(c)), these sites were assumed to be sufficiently far south (100–150 km) as to be unaffected by the tailings dumping. The second group were the northern sites Puerto Pan de Azucar, Frente Isla Pan de Azucar and Playa Blanca, located within the Parque Nacional Pan de Azucar and showed no evidence of tailings deposition. Finally, the third group were the central sites Caleta La Lancha, Caleta Agua Hedionda, Palito 1000 m Norte, Playa Palito, Palito 2000 m Sur and Playa Cha~ naral, these sites are centred around the dumping point at Caleta Palito and had varying degrees of tailings deposition. The effective porewater (Zhang, Zhao, Sun, Davidson, & McGrath, 2001), and the seawater labile (Davidson & Zhang, 1994), metal concentrations were measured using the diffusion gel technique (DGT). The sampler consists of a plastic base and cap which are used to hold the gel ‘sandwich’ in place. The base layer of the gel ‘sandwich’ is a gel impregnated with Chelex beads, which bind the labile metals reaching them. The second layer is the diffusion gel, the pore size of which is designed to allow only labile metal ions to pass. The third layer is a 0.45 lm cellulose-nitrate filter which protects the diffusion gel from abrasion. The samplers were assembled in a laminar flow hood less than a week before they were due to be used, the plastic parts were acid washed (10% HNO3 for 48 h) and then rinsed in ultrapurTM water prior to assembly. Table 1 The detailed location of the beaches used in this study Beach Puerto Pan de Azucar Frente Isla Pan de Azucar Playa Blanca Caleta La Lancha Caleta Agua Hedionda Palito 100 m Norte Playa Palito Palito 2000 m Sur Playa Cha~ naral Las Piscinas Torres del Inca Playa Zenteno Code Md (u) Pue Fre Bla Lan Hed Mil Pal Dos Cha Pis Tor Zen )0.03 1.54 2.43 1.96 1.94 )0.78 )0.78 )0.14 2.30 1.72 )0.10 1.67 Lat. Long. 0 26°08:3 S 26°08:40 S 26°11:10 S 26°13:40 S 26°15:30 S 26°16:10 S 26°16:30 S 26°17:00 S 26°20:50 S 26°33:00 S 26°36:20 S 26°51:10 S The column Md refers to the graphic mean sediment grain size in units of phi (u). 070°39:30 W 070°40:00 W 070°39:20 W 070°39:20 W 070°38:50 W 070°39:20 W 070°39:30 W 070°29:60 W 070°37:40 W 070°41:10 W 070°44:50 W 070°48:30 W M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 5 Due to the dynamic nature of the littoral environment on this part of the Chilean coast it was not possible to leave the samplers in situ. Therefore, for the porewater samples three replicate cores were collected from each site. The cores were collected using PVC tubing 45 mm in diameter and 150 mm in length, which had been acid washed prior to use (10% HNO3 for 48 h). The core tubes were inserted into the sediment to a depth of approximately 75 mm, removed with the sample, and a cap placed on the top of the tube. The sample was then inverted and a DGT unit placed face down in the sediment. The cores were then placed in new ZiplocTM bags in a cooler. The exposure time of the DGT sampler to the porewater was at least 24 h for each sample. However, exposure times varied from site to site due to logistical constraints. At the end of the exposure the DGT units were removed from the samples, rinsed in ultrapurTM water, and placed in clean plastic bags for the return journey to the laboratory in a cooler. Water samples (three replicate samples for each site) were collected from the surf zone on each beach. Water was collected from the surf using a plastic bucket. One litre of seawater was placed into a new ZiplocTM bag along with a DGT unit. The bag was then placed in a second new ZiplocTM bag for added security/durability and the bags placed in a cooler. Again the minimum exposure time of the DGT unit to the seawater was 24 h for each sample. In the laboratory the Chelex gels were removed from the DGT units and placed into 1.5 ml micro-centrifuge tubes with 0.8 ml of 10% HNO3 (Merck suprapur) and then sent by courier to the University of Lancaster for analysis. Samples were analysed by inductively coupled plasma-mass spectrometry (ICP-MS, Varian Ultramass) using a direct injection nebulizer (CETAC). The detailed methodology has been published elsewhere (Zhang, Davidson, Knight, & McGrath, 1998; Zhang et al., 2001). Analysis of the sediment structure was conducted using sediment from the meiofauna samples. Three of the five samples, from each site were selected at random for sediment analysis. The samples were first washed with fresh water on a 63 lm screen to remove salt crystals, there was no silt component to the sediments at any of the sites. The sediment samples were then dried for 72 h at 80 °C in a drying oven. The dried sediment samples were then sieved through a stack of standard brass analytical sieves, shaken for 15 min. Each fraction was weighed to the nearest 0.1 g. The following measures were calculated using phi (u) values, the graphic mean (Md, Table 1), the inclusive graphic quartile deviation (QDI) and the inclusive graphic skewness (SkI). None of the measures was able to identify either the presence or proportion of tailings present at a given site. Therefore, a qualitative assessment of the amount of tailings present at each site was made based on visual observation (Table 6), the tailings have distinct yellow colour which allows them to be distinguished from the natural fine sediments which are grey. Sites with the least amount of tailings were given the lowest rank. In the laboratory the meiofauna were extracted from the sand using a simple decantation technique (Pfannkuche & Thiel, 1988). Samples were shaken for approximately 30 s and the supernatant poured through a 44 lm mesh. This process was repeated five times for each sample (95% extraction efficiency, Lee, 2001). The 6 M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 meiofauna were then washed into a girded petri dish and counted using a binocular microscope (Wild M5, 200). The meiofauna were analysed to a higher taxonomic resolution than species, typically orders, referred to herein as ‘taxa diversity’. The underlying hypothesis for analysing samples at higher taxonomic resolution is that species level analyses are more affected by natural variation in environmental variables, such as sediment grain size, than are analyses at the level of family, order or phylum (Warwick, 1988a). Furthermore, several studies have concluded that there is no substantial loss of information when considering the overall effects of a pollutant on the environment when the biota is analysed at higher levels of taxonomic resolution, particularly where the pollution gradient is marked (Somerfield & Clarke, 1995; Warwick, 1988b). The meiofauna data collected were analysed using multivariate statistical analyses (PRIMER, Plymsolve). The following multivariate analyses were conducted: analysis of similarities (ANOSIM), non-metric multidimensional scaling (MDS), similarities percentage analysis (SIMPER) and biotic/environmental variable analysis (BIOENV). 3. Results Of the metals analysed in this study only the copper concentrations appeared to be associated with the distribution of the tailings so only they will be considered here. The data and discussion for all the metals sampled in this study is presented elsewhere (Lee, Correa, & Zhang, 2002). The highest concentrations of copper were associated with those beaches that had solid tailings waste present. The pattern of effective porewater copper distribution in the sediment was mirrored by that of the labile seawater copper in the adjacent surf, though it was always lower (Fig. 2). The highest effective porewater copper concentration was found at Caleta Agua Hedionda (1449.59 lg Cu l1 , S.E. 842.80) which was also the location with the highest labile seawater copper concentration (41.42 lg Cu l1 , S.E. 3.36). The lowest effective porewater copper concentration was found at Las Piscinas (6.43 lg Cu l1 , S.E. 0.37), whilst the lowest labile seawater copper concentration was found at Frente Isla Pan de Azucar (1.93 lg Cu l1 , S.E. 0.24). The densities of the meiofaunal assemblages at the reference sites (Las Piscinas, Torres del Inca and Playa Zenteno) are clearly higher than at the other sites sampled (Fig. 3(a)). It is also apparent that the meiofaunal assemblage densities at the northern sites (Puerto Pan de Azucar, Frente Isla Pan de Azucar and Playa Blanca) are higher than those from the remaining six central sites which were clearly impacted by the tailings (Fig. 3(a)). There was a significant negative relationship between the meiofaunal assemblage densities and the effective porewater copper concentration (F ¼ 69:48, p < 0:0001) indicating clearly that meiofaunal assemblage densities decrease with increasing copper concentrations (Fig. 3(b)). The ANOSIM analysis for the meiofaunal assemblage densities resulted in a global R value of 0.547 (p < 0:0001) which was statistically significant, reflecting significant differences between sites. Post hoc pair wise comparisons were carried out M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 7 10000 -1 Copper concentration (µg Cu L ) Seawater Porewater 1000 100 10 1 Pue Fre Bla Lan Hed Mil Pal Dos Cha Pis Tor Zen Site Fig. 2. Effective porewater copper and the labile seawater copper concentrations (lg l1 ) recorded at each of the sites (bars represent 1SE). by recomputing R for specific pairs of sites (Table 2). Most comparisons indicate that the sites differ significantly from each other. The exceptions were Caleta La Lancha with Palito 1000 m Norte and Palito 2000 m Sur, Palito 1000 m Norte with Palito 2000 m Sur, and Playa Palito with Playa Cha~ naral. The MDS plot (Fig. 4) is the meiofaunal assemblage densities data pooled for all sampling occasions and root transformed. This plot has a stress value of 0.08 which indicates that it is a good representation of the similarities in the meiofaunal assemblages between the sites (see Clarke & Warwick, 1994). The degree of similarity between two sites is represented by how close or far they are from each other on the MDS plot. The sites on the MDS plot can be ordered as follows (from unimpacted to impacted): Torres del Inca, Las Piscinas, Playa Zenteno, Puerto Pan de Azucar, Frente Isla Pan de Azucar, Playa Blanca, Playa Palito, Playa Cha~ naral, Palito 2000 m Sur, Caleta La Lancha, Palito 1000 m Norte and Caleta Agua Hedionda. SIMPER analyses were carried out using the reference, northern and central site groupings and the within-group similarities are presented in Table 3. The four meiofaunal groups which contributed the most to the similarity are listed. For the northern sites, nematodes (0.197) accounted for most of the similarity of the sites within the group, followed by harpacticoid copepods, turbellarians and foraminiferans. The average similarity between the northern sites was 0.754, and the first four meiofaunal groups contributed 0.619 to the similarity between these sites. Turbellarians (0.329) accounted for most of the similarity between the central sites, 8 M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 Meiofaunal density 50 cm -3 1500 1000 500 0 (a) Pue Fre Bla Lan Hed Mil Pal Dos Cha Pis Tor Zen Site Meiofaunal density 50 cm -3 3.5 3 2.5 2 y = -0.889x + 2.980 1.5 2 R = 0.874 ANOVA, F = 69.48, p < 0.0001 1 0 (b) 0.5 1 2 3 1.5 2.5 3.5 -1 Effective copper concnetration (µg Cu L ) 4 Fig. 3. (a) Meiofaunal assemblage densities recorded at each of the sites using pooled data for each site from all sampling occasion (bars represent 1SE). (b) Regression analysis of the effective porewater copper concentration and the meiofaunal assemblage densities. followed closely by nematodes (0.328), harpacticoid copepods and foraminiferans. The average similarity between the central sites was 0.668, and the first four meiofaunal groups contributed 0.904 to the similarity of the central sites. For the reference sites the nematodes (0.274) accounted for most of the similarities between the sites of the group, followed by harpacticoid copepods, turbellarians and foraminiferans. The average similarity between the reference sites was 0.746, and the first four meiofaunal groups contributed 0.780 to the similarity between the reference sites. The dissimilarities between the northern, central and reference sites are presented in Table 4, where the four meiofaunal groups which contributed most to the M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 9 Table 2 Between-site differences of 12 sites from the Cha~ naral area, for all sampling occasions, resulting from post hoc pair wise comparisons using the analysis of similarities (ANOSIM) methodology (p-values in bold are not significant) Fre Bla Lan Hed Mil Pal Dos Cha Pis Tor Zen Pue Fre Bla Lan Hed Mil Pal Dos Cha Pis Tor 0.000 0.000 0.000 0.000 0.000 0.003 0.001 0.017 0.000 0.000 0.000 0.002 0.000 0.000 0.000 0.000 0.000 0.000 0.004 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.007 0.000 0.000 0.002 0.804 0.001 0.796 0.003 0.000 0.000 0.000 0.002 0.000 0.001 0.019 0.000 0.000 0.000 0.025 0.880 0.012 0.000 0.001 0.000 0.017 0.104 0.000 0.000 0.000 0.010 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.015 0.000 Impacted sites Lan Northern sites Reference sites Fre Zen Dos Mil Pis Bla Tor Pal Pue Hed Cha Fig. 4. A non-metric multidimensional scaling (MDS) analysis of the relationship between the sites sampled using root transformed data pooled for each site from all sampling occasions. (Stress ¼ 0.08) dissimilarity are listed. The average dissimilarity between the northern and central sites was 0.490. The foraminiferans contributed most to the dissimilarity (0.149) followed by harpacticoid copepods, gastrotrichs and nematodes. The first four meiofaunal groups contributed 0.467 of the dissimilarity between the northern and central sites. The turbellarians contributed only 0.057 to the dissimilarity between the northern and central sites. The average dissimilarity between the northern and reference sites was 0.287. The nematodes (0.113) contributed most to this dissimilarity followed by harpacticoid copepods, gastrotrichs and ostracods. The first four meiofaunal groups contributed 0.434 to the dissimilarity between the northern and reference sites. The foraminiferans and turbellarians contributed 0.087 and 0.070, 10 M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 Table 3 Similarities percentage (SIMPER) analysis of the contribution that the major meiofaunal groups made to within-site group similarities (%), based on data for all sampling occasions Sites Meiofaunal group % Cumulative % Northern Pue, Fre, Bla Nematoda Harpacticoida Turbellaria Foraminifera 0.197 0.147 0.141 0.131 0.197 0.347 0.488 0.619 Central Lan, Hed, Mil, Pal, Dos, Cha Turbellaria Nematoda Harpacticoida Foraminifera 0.329 0.328 0.132 0.115 0.329 0.657 0.790 0.904 Reference Pis, Tor, Zen Nematoda Harpacticoida Turbellaria Foraminifera 0.274 0.232 0.161 0.113 0.274 0.506 0.677 0.780 Table 4 Similarities percentage (SIMPER) analysis of the contribution that the major meiofaunal groups made to between-site group dissimilarities (%), based on data for all sampling occasions Sites Meiofaunal group % Cumulative % Northern and Central Foraminifera Harpacticoida Gastrotricha Nematoda 0.149 0.122 0.113 0.084 0.149 0.270 0.383 0.467 Northern and Reference Nematoda Harpacticoida Gastrotricha Ostracoda 0.113 0.108 0.106 0.106 0.113 0.222 0.328 0.434 Central and Reference Harpacticoida Nematoda Ostracoda Foraminifera 0.212 0.174 0.116 0.108 0.212 0.386 0.502 0.610 respectively to the dissimilarity between the northern and reference sites. The average dissimilarity between the central and reference sites was 0.488. The harpacticoid copepods (0.212) contributed most to this dissimilarity followed by nematodes, ostracods and foraminiferans. The first four groups contributed 0.610 to the dissimilarity between the central and reference sites. The turbellarians contributed only 0.074 to the dissimilarity between the central and reference sites. A BIOENV analysis was conducted using the following abiotic variables: Cupw , Cusw , Mnsw , Nisw , Znsw Md and tailings, it was not possible to use all the combinations of variables measured due to limitations of the software (the subscripts pw and sw refer to porewater and seawater, respectively). Only those metals which had been identified as varying from what would be considered natural background M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 11 Table 5 Biotic/environmental variable (BIOENV) analysis showing which environmental variable, or combination of variables, best described the biotic similarities between sites Best variable combination (qx ) k 1 2 3 4 Cupw (0.587) Cupw + Tailings (0.653) Cupw + Znsw + Tailings (0.677) Cupw + Cusw + Znsw + Tailings (0.666) Tailings (0.585) Cusw + Tailings (0.642) Cusw + Znsw + Tailings (0.662) Cusw (0.570) Cusw + Znsw (0.633) Cupw + Cusw + Tailings (0.643) k the number of variables in the combination (the best combination is in bold type). concentrations (Lee et al., 2002) were used in this analysis. The results of the BIOENV test are presented in Table 5. The combination of variables which best explained the changes in the meiofaunal assemblages between sites was Cupw , Znsw and tailings (0.667). The best single variable was Cupw (0.587), followed by tailings (0.585). The best two variable combination was Cupw and tailings (0.653). Note that the sediment grain size (Md) did not feature in any of the combinations presented in Table 5. The mean meiofaunal assemblage taxa diversities, expressed as the number of groups, for all sampling occasions from January 1997 to March 2000 are presented in Fig. 5(a). Even though the groups used are not necessarily taxonomically equivalent, the groupings are consistent throughout the study and therefore the comparison is valid. Fig. 5(a) indicates that the central sites generally had lower taxa diversities than all the other sites. There was no distinction between the reference sites and the northern sites in terms of taxa diversity. Regression analysis of the relationship between taxa diversity and the effective porewater copper concentration (Fig. 5(b)) was significant (F ¼ 33:66, p ¼ 0:0002) indicating that taxa diversity decreases with increasing effective porewater copper concentrations. The central sites had lower foraminiferan densities than the other sites (Fig. 6(b)). Regression analysis (Fig. 6(b)) indicates that there is a significant decrease in foraminiferan density with increasing effective porewater copper concentration (F ¼ 17:15, p ¼ 0:002). The density of turbellarians, on the other hand, did not differ between the northern, central and reference sites (Fig. 6(c)). The regression analysis of the relationship between turbellarian density and effective porewater copper concentration (Fig. 6(d)) was not significant (F ¼ 3:33, p ¼ 0:098). One important observation of the turbellarian data was that the family Otoplanidae (cf. Kata galapagoensis) often dominated the central sites, i.e. those heavily impacted by tailings. For example, 100% of the turbellarian fauna at Caleta La Lancha and Palito 2000 m Sur, and 99% at Palito 1000 m Norte, was represented by otoplanids. Nematode densities at the reference sites were higher than at the rest of the sites (Fig. 6(e)). Generally the northern sites had higher densities of nematodes than the central sites but it was not a clear distinction. Regression analysis (Fig. 6(f)) indicated that there was a significant decrease in nematode density with increasing effective porewater copper concentration (F ¼ 13:16, p ¼ 0:005). Finally, the harpacticoid copepod densities (Fig. 6(g)) clearly separated the northern, central and 12 M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 Meiofaunal taxa diversity 50 cm -3 10 8 6 4 2 (a) Pue Fre Bla Lan Hed Mil Pal Dos Cha Pis Tor Zen Site Meiofaunal taxa diversity 50 cm -3 1 0.8 0.6 0.4 y = -0.288x + 0.948 0.2 R = 0.771 ANOVA, F = 33.66, p = 0.0002 2 0 0 (b) 1 2 3 0.5 1.5 2.5 -1 Effective copper concentration (µg Cu L ) 3.5 Fig. 5. (a) Meiofaunal assemblage taxa diversities recorded at each of the sites using pooled data for each site from all sampling occasion (bars represent 1SE). (b) Regression analysis of the effective porewater copper concentration and the meiofaunal assemblage taxa diversities. reference sites. The highest harpacticoid copepod densities were found at the reference sites, and the lowest at the 100% tailings sites where they were usually absent. There was a clear, strong significant and negative relationship between harpacticoid copepod density and effective porewater copper concentration (F ¼ 34:90, p ¼ 0:0002), indicating that harpacticoid copepod density decreases with increasing copper concentration (Fig. 6(h)). Each of the meiofaunal assemblage measures was examined in relation to the level of tailings deposition at each site. The sites were ranked by the amount of tailings they had received (Table 6), and the relationship between each of the measures was M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 5 (a) Foraminifera (b) 0.6 13 y = -1.181 +0.490 4 2 R = 0.686 ANOVA, F = 17.15, p = 0.002 0.4 3 0.2 2 1 0 0 200 2.5 (c) Turbellaria (d) 2 150 1.5 100 Fauna density 50 cm -3 1 50 0.5 0 0 900 3 (e) Nematoda 750 2.5 600 2 450 1.5 300 1 150 0.5 0 0 400 y = -0.447x + 1.877 2 R = 0.250 ANOVA, F = 3.33, p = 0.098 (g) Harpacticoida (f) y = -0.902 + 2.510 2 R = 0.568 ANOVA, F = 13.16, p = 0.005 3 (h) 2.5 300 y = -1.429 + 2.228 2 200 2 R = 0.777 ANOVA, F = 34.90, p = 0.0002 1.5 1 100 0.5 0 Pu e Fr e Bl a La n He d M il Pa l Do Chs a Pis To Ze r n 0 Sites 0 1 2 3 4 -1 Effective copper conc. (µg Cu L ) Fig. 6. The (a) foraminiferan, (c) turbellarian, (e) nematode and (g) harpacticoid densities recorded at each of the sites using pooled data for each site from all sampling occasion (bars represent 1SE), and regression analyses (data Log10 ðx þ 1Þ transformed) of the effective porewater copper concentration and the (b) foraminiferan, (d) turbellarian, (f) nematode and (h) harpacticoid densities. 14 M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 Table 6 The study sites ranked by a qualitative assessment of the amount of tailings present at each site Site Ranking Pue Fre Bla Lan Hed Mil Pal Dos Cha Pis Tor Zen 6 5 4 11 11 8.5 7 8.5 11 2 2 2 Table 7 Spearmans rank order correlations between the meiofaunal assemblage data and the ranked tailings impact (See Table 6 for tailings impact ranks), data collected for all sampling occasions Measure Correlation Density Taxa Diversity Foraminifera Turbellaria Nematoda Harpacticoida )0.838 )0.810 )0.824 )0.316 )0.821 )0.952 determined using a Spearmans rank order correlation (Table 7). All the meiofaunal assemblage measures showed strong negative correlations (< 0:800) with the tailings with the exception of turbellarian density. 4. Discussion As only the distribution of copper appeared to be connected with the distribution of the tailings only this metal was considered in this paper (see Lee et al., 2002). The effective porewater copper concentration and the labile seawater copper concentrations were highly correlated with each other (Lee et al., 2002), though the seawater copper was always lower. This high degree of association suggests that the primary source of copper at each of the impacted sites was the tailings currently deposited on those beaches and not the ‘clear water’ tailings dumped at Caleta Palito. It is important to understand that the between-site variation in the meiofaunal assemblages is not as a result of the natural between-site variation in sediment grain size (BIOENV analysis, Table 6). The sediment structure is well known as a ‘super factor’ in determining the structure of meiofaunal assemblages (Coull, 1988). The results presented here indicate that any effect that the natural sediment grain size has on the meiofaunal assemblages is secondary to the effects of the copper mine tailings. M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 15 However, the blocking of the interstitial space of coarse sediment beaches by the fine tailings does have a significant impact on the meiofaunal assemblages and is discussed below (see also Lee & Correa, in press). The principal changes in the meiofaunal assemblages observed in this study are a reduction in both density and taxa diversity with increasing porewater copper concentrations. However, the presence of tailings at a site is highly correlated with the porewater copper concentration, as one is certainly the source of the other. It is difficult, therefore, to separate the effects that copper or the tailings deposition would have in isolation using field data alone. There is some evidence of the effects of porewater copper alone provided by the changes to the meiofaunal assemblages at Playa Palito, where the physical impact of the tailings is lowest amongst the impacted sites and from microcosm toxicity tests (Lee, 2001) which showed the trends outlined above. Further evidence of the effects of porewater copper alone were the lower meiofaunal assemblage densities, but not the taxa diversities, at the northern sites when compared with the reference sites. The effects of the tailings alone were not observable in the field as they were always associated with increased copper concentrations. However, microcosm tests (Lee, 2001) where varying amounts of a tailings substitute (fine sand) were added to coarse sand indicated that a reduction in the interstitial space led to an increase in surface utilizing groups, such as foraminiferans, but a decrease in true interstitial animals, such as the polychaete Saccocirrus sonomacus (Lee & Correa, in press). In terms of the specific meiofaunal groups the results presented here indicate that impacted sites are characterised by the absence of the harpacticoid copepods and the increased importance of turbellarians. The sensitivity of the harpacticoid copepods to pollutants in general (Lampadariou, Austin, Robertson, & Vlachonis, 1997; Sandulli & De Nicola-Giudici, 1990) and metals in particular, has been noted in other studies (Lee, Correa, & Castilla, 2001; Van Damme, Heip, & Willems, 1984). In most of these other studies, however, the effects of the metals on harpacticoid copepods have been confounded or masked by the presence of a mixture of pollutants. In the Cha~ naral case the absence of pollutants other than metals makes the relationship clear in the field. The increased importance of turbellarians belonging to the family Otoplanidae at the impacted sites is a new observation. This has not been reported previously in the literature, though this may be because the focus of previous meiofauna-pollution studies has been on the harpacticoid copepods and nematodes. Additionally, the turbellarians are also more important members of the meiobenthos in sandy sediments, like those studied here, than in fine sediments (Martens & Schockaert, 1986). The turbellarian species encountered here was found in particularly high densities on beaches with significant tailings deposition. At Caleta La Lancha, for example, it normally constituted >90% of the total meiofaunal assemblage density. The implication is that turbellarians are physiologically capable of tolerating the high levels of labile copper encountered at these sites (Caleta La Lancha: 287.5 lg l1 effective porewater copper concentration). A comparison of the results presented in this study with others is difficult as no other study has been conducted in a similar environment. Furthermore, other studies 16 M.R. Lee, J.A. Correa / Marine Environmental Research 59 (2005) 1–18 of the effects of pollutants in general, including metals, on meiofaunal assemblages have been conducted in estuarine or harbour environments predominantly in Europe (Lampadariou et al., 1997; Sandulli & De Nicola-Giudici, 1990; Somerfield, Gee, & Warwick, 1994; Van Damme et al., 1984). In these locations the physico-chemical conditions are entirely different to those prevailing in the high-energy sandy beaches of northern Chile. The bioavailable component of the metals is also unknown in the studies referred to above, as only total sediment metal concentrations were reported. The nature of the sites, characterised by fine sediments, anoxia and therefore high levels of acid volatile sulphides, and the presence of high concentrations of organic carbon mean that the bioavailable metals will be lower due to complexation and adsorption, and their effects possibly insignificant compared with other pollutants present (Chapman et al., 1998). One exception is the recent study by Millward (2001) where a detailed analysis of the porewater metal speciation was made. Their findings with regard to both nematodes and harpacticoids are in agreement with ours. The effective porewater copper concentration range for our sites was from 6.43 lg Cu l1 (101 nM) at Las Piscinas to 1449.59 lg Cu l1 (22831 nM) at Caleta Agua Hedionda, equivalent to the medium and high concentrations used in their experiments. Our study demonstrates that the meiofaunal groups with the highest potential for biomonitoring purposes in metal-enriched sandy beach ecosystems are the harpacticoid copepods and the foraminiferans. The use of harpacticoid copepods as biomonitors of metal pollution has previously been proposed by Van Damme et al. (1984) and Lee et al. (2001). The data presented here from the Cha~ naral region of northern Chile provides clear additional evidence that harpacticoid copepods can be used for biomonitoring purposes. Rainbow (1997) described in detail the physiology of metal uptake by crustaceans, indicating that for the smaller, physiologically less advanced groups of crustaceans, including the Copepoda, the mechanisms of metal uptake are essentially passive. It follows, therefore, that the higher the bioavailable metal concentration in the porewater, the greater the toxic response of the harpacticoid populations. The sensitivity of harpacticoid copepods relative to nematodes in polluted situations was proposed by Raffaelli and Mason (1981) in the form of the nematode-copepod ratio for pollution monitoring. However, Lee et al. (2001) demonstrated that the nematode-copepod ratio (when applied to high-energy sandy beach ecosystems) was not a good measure of pollution impact, but suggested that the mean harpacticoid density alone was a good indicator of the extent of metals impact on sandy beaches. In summary, we can expect that the dumping of copper mine tailings into the coastal environment, under similar conditions to those encountered on the northern coast of Chile, will result in a reduction in the meiofaunal assemblage density and then taxa diversities as the bioavailable concentration of copper increases in the porewater. Harpacticoid copepods, and possibly foraminiferans, have been highlighted as sensitive of the impact of the tailings disposal and thus have potential as biomonitors. 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