Crustacean Assemblages Along the Guadiana River Estuary (South-Western Iberian Peninsula) J

Journal of the Marine Biological Association of the United Kingdom, 2011, 91(1), 127–138. # Marine Biological Association of the United Kingdom, 2010 doi:10.1017/S0025315410001074 Crustacean assemblages along the Guadiana River estuary (south-western Iberian Peninsula) j. emilio sa’ nchez-moyano and isabel garci’a-asencio Departamento Fisiologıá y Zoologıá, Facultad de Biologıá, Universidad Sevilla, Avenida Reina Mercedes 6, 41012 Sevilla, Spain

The spatial distribution of the subtidal crustacean assemblages of the Guadiana River estuary was studied previous to the building of the Alqueva Dam (the biggest dam in Europe). The differences between an estuarine and marine environment seem to be the main reason responsible for the composition and distribution of the crustaceans along the study zone. The Guadiana estuary has shown high number of species in comparison with other nearby estuaries and this richness seems justified by the scarce influence of pollutants (most of them have shown low or moderate values) and their hydrodynamic and granulometric characteristics (76 species were found, 39 in the estuarine area). A gradient of enrichment and structuring of the assemblages was shown from the upstream to the marine zones and a spatial segregation of species was found along this estuarine environmental gradient, e.g. the amphipod Corophium multisetosum and the isopod Cyathura carinata in the upper estuary; the amphipod Bathyporeia cf. pilosa and the isopods Lekanesphera levii and Saduriella losadoi in the middle estuary; the amphipod Melita hergensis in the mouth; and a high number of species in the marine area. Since the Alqueva Dam will reduce the river discharges and may cause changes in the abiotic characteristics such as granulometry of sediments or salinity, this study establishes a baseline against which a monitoring programme or follow-up studies could measure any significant effects of the dam or related impacts.

Keywords: crustacean assemblages, environmental factors, baseline study, estuary, Iberian Peninsula

Submitted 4 November 2009; accepted 4 May 2010; ﬁrst published online 1 November 2010

INTRODUCTION and interannual scales and crosses a wide rural area along the Iberian Pyrite Belt, with intense mining extraction since Estuaries show both high biological activity and high pro- Phoenician and Roman times, although this activity has duction (Wolff, 1983; Valiela, 1995). In estuarine zones, the ceased in the last decade (Caetano et al., 2006). animal assemblages are established along a continuum from The Guadiana River basin is regulated by approximately internal areas to the mouth with more or less overlapping dis- 100 reservoirs, and since 2001 the Alqueva Dam, the biggest tributions of the species according to the ecocline model pro- dam in Europe, with a water storage capacity of 4150 hm3, posed by Attrill & Rundle (2002). Like a transition zone has regulated more than 80% of the freshwater flow (the between the marine and the freshwater domains, they are pre- damned area within the Guadiana River basin has increased ferential sites for the development of several human activities by 12% to a total of 89%) (Gonzalez et al., 2007). The altera- such as industry, transport, fisheries and tourism. These tion of flow regimes is recognized as one of the most serious systems are also areas with considerable pollution problems processes affecting community structure and function in (Dauvin et al., 2006). However, interpretation of the effects lagoons, estuaries and deltas of the world (Sklar & Browder, of pollution on the estuaries is often difficult since the geologi- 1998; Bunn & Arthingthon, 2002). The Alqueva Dam will cal, physical and chemical characteristics can be confounded reduce the abrupt river discharges to the estuary and may with the impacts of anthropogenic origin (Warwick, 1988; cause an important impact on the quantity and types of sedi- Weisberg et al., 1997; Gaston et al., 1998; Morrisey et al., ments and on the biogeochemical cycles of nutrients that 2003). might lead to a significant change in the food web structure The Guadiana River, located along the southern border of both the estuary and the coastal zone (Caetano et al., between Spain and Portugal, is recognized as one of the less 2006; Cravo et al., 2006; Gonzalez et al., 2007). The possible polluted European estuaries (Vasconcelos et al., 2007) and impact of this dam in the Guadiana estuary and the nearby as one of the rivers with greater contributions of sediments coastal area has been analysed for fish assemblages to the Spanish coasts (Consejerıá de Medio Ambiente, (Chıćharo et al., 2006a; Morais et al., 2009) and planktonic 1997). This river shows an irregular flow on both seasonal assemblages (Chıćharo et al., 2006b). Besides, Wolanski et al. (2006) proposed an ecohydrology model integrating physical, chemical and biological processes (the last item

Corresponding author: was determined by planktonic, bivalve and ﬁsh assemblages). J.E. Sa´nchez-Moyano The soft-bottom macrofauna is one of the more important Email: [email protected] structuring elements of the food web inside estuaries (Herman

127 128 j. emilio sa’ nchez-moyano and isabel garci’a-asencio

et al., 1999) and is considered a key element of many marine and estuarine monitoring programmes (Ysebaert & Herman, 2002). The crustacean assemblages are among the most diverse and abundant groups of soft-bottom macrofauna (Cuhna et al., 1999; Lourido et al., 2008) and have been recognized as one of the most sensitive to changes in environmental conditions (Desrosiers et al., 1990; Sańchez-Moyano & Garcıá-Go´mez, 1998; Guerra-Garcia & Garcıá-Go´mez, 2004). To date, however, there is no information on the impact on the composition and distribution of the subtidal macrofauna in the Guadiana estuary. Thus, the aim of this work was to characterize the composition and distribution of the crustacean assemblages of subtidal soft-bottom sediments along the estuarine gradient previous to the building of the Alqueva Dam. This work may contribute to assessing changes in the marine–estuarine system related to the impact of the dam since it can be used as a reference condition in a long term perspective.

MATERIALS AND METHODS

Study area The Guadiana River is one of the main rivers of the Iberian Peninsula with 820 km in length and a drainage basin area Fig. 1. Location of the sampling stations at the Guadiana River estuary. around 67.500 km2, which 12.000 km2 belong to Portugal. The estuary is a single-channel mesotidal estuary of about 80 km in length, 70 to 800 m wide and 5 to 15 m depth. used as a relative measure of metal pollution in the sediments There are two natural protected areas located near the for Cr, Cu and Zn according to the regional background estab- ¼ mouth: Natural Park of Isla Cristina Marshes and Natural lished by Ruiz (2001) for unpolluted sandy sediments. Igeo Reserve of Sapal de Castro Marim, in the Spanish and log2 (Cn/1.5 x Bn), where Cn is the value of the element n Portuguese margin, respectively. Both areas belonged to the and Bn is the background data of that element. According to ancient Guadiana delta and are formed by a complex web of Ruiz (2001), the index values were divided in five groups: unpol- channels. In recent years, some Spanish and Portuguese luted (Igeo , 1); very low polluted (1 , Igeo , 2); low polluted associations have proposed the creation of the International (2 , Igeo , 3); moderate polluted (3 , Igeo , 4); highly Natural Park of the Lower Guadiana. The Guadiana River polluted (4 , Igeo , 5); and very highly polluted (Igeo . 5). flows into a wide continental shelf with soft slope (20 m in For water analysis, a water sample per station was obtained depth is reached up 4–5 nautical miles out). close to the bottom by a vertical Alpha Van Dorn-style bottle. The following parameters were measured in situ: temperature, conductivity and salinity by conductivimeter WTW LF-323; Sampling and laboratory analysis pH by phmeter WTW 330i; and dissolved oxygen by oximeter Sampling was undertaken in the summer of 2000 at 14 subti- WTW OXI-196. dal stations: 8 along 38 km in Guadiana main course, 2 in Carreras River (Isla Cristina Marshes) and 4 in near coastal Data analysis area (Figure 1). At each station, six replicates samples (five for biological analysis and one for sediment analysis) were Univariate and multivariate analyses for environmental vari- taken with a 0.05 m2 van Veen grab. Each replicate was ables and crustacean assemblages were performed using the sieved in seawater through a mesh of 0.5 mm, fixed with 4% PRIMER v 5.2.8 software package. Previously, the replicate formalin and stained with Bengal rose. Crustaceans were data were pooled for the multivariate analysis. The crustacean sorted and, whenever possible, identified to species level. data were analysed to obtain the total number of taxa, abun- For sediment analysis, granulometry was assessed follow- dance, evenness and Shannon diversity index using neperian ing Buchanan & Kein (1984) methodology, and organic logarithms. Spatial differences for univariate variables were matter percentage was obtained as weight loss by ignition at analysed by a one-way analysis of variance (ANOVA), after 4508C for 24 hours (mean value of 3 replicates per station). verifying normality (Kolmogorov–Smirnov test) and hom- + The other sediment parameters were measured by laboratories ogeneity of variances (Barlett test). The data were log10 (x of the Environmental Agency of the government of Andalusia 1) transformed prior to analysis. Homogeneous groups were (South Spain): total organic carbon (TOC) was determined by separated by a Tukey test set at the 5% significance level. EPA 415.1; total nitrogen in the sediment was assessed via Affinities between stations were established using cluster Kjedahl digestion; phosphate was measured using UV visible and MDS (non-metric multidimensional scaling) analysis spectrophotometry; and the metal contents were measured with the species abundance (transformed by the fourth by SM 3111 A and B for Cd, Zn, Cu, Ni and Cr, and EPA root). Percentage of similarity analysis (SIMPER) (Clarke, 245.1 for Hg. The index of geoaccumulation (Igeo) has been 1993) was used to determine the taxa involved in grouping crustacean assemblages in the guadiana estuary 129 the different stations. This analysis, based on the matrix of similarity in taxa abundance obtained from the Bray–Curtis index, calculates the contribution of each taxa to either the dissimilarity between groups of stations (discriminatory taxa) or the similarity within a group (typical taxa). sand The relationship between the physical environment and Sediment type crustacean assemblages was analysed by BIOENV and canonical correspondence analysis (CCA). BIOENV analysis consists in the comparison, through the harmonic rank correlation coefficient of Spearman, the rank similarity matrix on Median grain size species abundance and the rank similarity matrix obtained through Euclidean distances with the abiotic variables (Clarke & Ainsworth, 1993). CCA is based on a unimodal response model that constrains the ordination axes to be linear combinations of the environmental variables that maxi- Dissolved oxygen mize the dispersion of sample or taxa scores (Ter Braak, 1986, 1990). In the ordinations, stations were represented as points and statistically significant environmental variables (after a Monte-Carlo permutation procedure) as arrows.

RESULTS

Environmental analysis Water and sediment characteristics are shown in Table 1. C mS % mg/l mm 8 8 8 8 Water parameters showed a natural trend of estuarine 8 systems, for example increases in salinity and pH from inner to outer points. Estuarine sediments were dominated by medium sand with the exception of the upstream stations (GU1, GU2 and GU3) with coarse or very coarse sand. In the coastal areas, there was a gradient from very ﬁne sand (shallower stations) to coarse sand with biogenic elements (deeper points). The organic matter in sediment showed scarce variations along the study area with moderate or low values. The same trend was shown by other parameters such as TOC, phosphates and total nitrogen. In relation to metal contents, the majority of the sites showed low or moderate concentrations with scarce spatial differences. In relation to Values of sediment and water parameters in each station. the geoaccumulation index, the stations were classiﬁed as having low or very low levels of pollution by Cr; and were unpolluted by Cu in most of the study area, except stations Table 1. GU2 and GU3 (very low levels of pollution) and Carreras River stations (low levels of pollution); meanwhile for Zn, the main channel stations were moderately polluted, the marine area had low or very low levels of pollution, and the Carreras River was highly polluted.

Crustacean community analysis mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg A total of 76 crustacean taxa belonging to six orders were found in the studied area: 38 amphipods, 11 cumaceans, 11 decapods, 10 isopods, 4 mysids, and 2 tanaids. Abundance data for each station are shown in Table 2. Organic matter % Total N Cd Zn Cu Cr Hg Ni Temp. pH Salinity Cond. The dendrogram obtained by cluster analysis for the crustacean community distinguished two major groups: estuarine and marine areas (Figure 2A). The estuarine area was further TOC mg/kg divided into four sub-groups: upper estuary (stations GU1 to GU4), middle estuary (GU5 to GU7), mouth area (station GU8) and the Carreras River system (although these stations Phosp. mg/kg have shown a low similarity with the other sites). The marine area was sub-divided into deep stations (H1B and H2B) and GU3GU4 0.5GU5 0.2GU6 0.3GU7 0.6 0.4GU8 0.5 0.3CR1 0.5 2.0 1.6CR2 0.5 0.0 1.9H1 0.5 0.0 1.2H1B 1.7 1.1 0.0 389.0H2 1.5 1.2 1.0 321.0H2B 1.6 0.7 228.0 0.0 10.1 2.2 0.2 5.1 286.0 1.7 4.5 0.4 224.0 149.1 7.0 0.4 201.0 1.2 1.3 8.0 130.4 5.8 17.5 4.7 116.2 0.3 1.1 5.8 14.8 118.7 3.3 0.6 50.6 15.3 105.0 481.0 0.1 0.5 16.7 22.4 81.3 0.5 10.5 0.1 35.1 321.0 0.1 7.9 197.0 39.8 0.5 0.0 9.7 216.0 23.3 0.0 25.3 59.0 6.3 0.5 0.1 104.0 28.3 58.0 28.9 18.2 0.0 25.1 17.5 68.0 22.0 105.0 19.8 9.9 19.9 74.0 0.0 25.5 11.6 7.8 24.6 23.0 0.4 29.0 7.9 39.5 24.7 0.4 7.9 14.4 9.0 22.8 7.9 33.0 0.1 31.0 31.7 0.0 9.3 7.9 47.0 21.4 19.6 7.9 13.7 0.1 18.5 22.7 0.0 10.0 19.8 29.8 14.2 22.0 8.1 25.7 84.0 13.0 8.0 19.7 26.8 36.0 15.9 16.2 74.0 5.8 8.0 41.5 68.0 37.5 18.6 6.6 70.0 8.1 36.7 16.4 6.3 0.7 8.0 49.1 84.0 6.3 36.2 50.7 0.4 8.1 36.1 7.1 0.4 8.1 93.0 49.9 0.4 36.2 66.0 36.2 Coarse 49.5 8.0 sand 0.4 49.7 90.0 5.5 Medium sand Medium 49.6 0.4 87.0 7.5 sand 49.4 82.0 Medium sand 0.4 7.8 Medium 8.0 76.0 sand 0.4 88.0 7.2 0.1 Medium sand 8.1 0.9 Medium sand 0.1 Medium sand 0.8 Very ﬁne sand Coarse sand Very ﬁne sand Coarse sand shallow stations (H1 and H2). MDS analysis showed results GU1GU2 0.3 0.3 0.7 0.5 1.4 1.0 292.0 411.0 7.2 4.9 55.4 125.4 9.0 19.9 35.9 24.4 0.0 0.0 17.9 20.3 25.7 25.8 8.0 8.0 0.6 0.7 1.5 1.7 80.0 79.0 6.4 6.4 0.8 1.4 Coarse sand Very coarse 3 .eii sa emilio j. 130

Table 2. Abundance (ind. m22 ) of the crustacean species identiﬁed in the Guadiana River estuary.

Species GU1 GU2 GU3 GU4 GU5 GU6 GU7 GU8 CR1 CR2 H1 H1B H2 H2B

Amphipoda Ampelisca cf. ruffoi 00 00000000012068 ’ Ampelisca diadema 00 00000088043600 garci isabel and nchez-moyano Ampelisca sarsi 00 00000016003600 Ampelisca sp.100 000000400000 Ampelisca sp.200 000000008000 Ampelisca spinipes 00 0000001200000 Amphilochus brunneus 00 0000001200000 Bathyporeia cf. pilosa 0 0 92 0 384 353 52 0 0 0 0 0 0 0 Cheirocratus sundevallii 00 000000004000 Corophium acherusicum 00 0000001200040 Corophium aculeatum 00 0000000042680308 Corophium multisetosum 352 248 2100 24 0000 000000 Corophium sextonae 0 0 0 0 0 40 12 4 1468 168 0 0 0 0 Dexamine spinosa 00 0000000160000 Elasmopus cf. rapax 00 040704400000 ’ Ericthonius punctatus 00 00027002400000a-asencio Gammaropsis palmata 00 0000000044020 Harpinia antennaria 00 0000000000016 Harpinia pectinata 00 0000000001200 Hippomedon oculatus 00 000000000004 Lembos sp. 0 0 0 0 0 27 0 0 0 0 0 0 0 0 Lembos websteri 00 000000000004 Leptocheirus pectinatus 002400000000000 Leucothoe lilljeborgi 00 0000000040160 Megaluropus agilis 00 000040000400 Melita hergensis 00 00000168000000 Melita palmata 00 000000080000 Metaphoxus fultoni 00 00000000012028 Microjassa cumbrensis 00 000700000000 Monoculodes carinatus 00 0000002400000 Pariambus typicus 00 000000000800 Parvipalpus onubensis 00 000000000400 Perioculodes longimanus 00 00000000480360 Photis longipes 00 0000000002000 Phtisica marina 00 0000004120004 Podocerus variegatus 00 0000007200000 Pontocrates arenarius 00 000044400000 Synchelidium longidigitatum 00 00000000032012 Cumacea Bodotria arenosa 00 000000800000 Cumella limicola 00 000000800000 Diastylis cornuta 00 000000000004 Diastylis laevis 00 0000000001200 Diastylis lucifera 00 000000000004 Eudorella truncatula 00 000000004800 Iphinoe acutirostris 00 000000000084 Iphinoe cf. serrata 00 0000000016804 Iphinoe trispinosa 00 000000404400 Leucon nasica 00 000000004000 Pseudocuma similis 00 000000000004 Decapoda Callianasa cf. tyrrhena 00 000000000004 Crangon crangon 00 040000000000 Diogenes pugilator 00 00000000280440 Ethusa mascarone 00 000000000400 Galathea cf. bolivari 00 000000000804 Liocarcinus depurator 00 000004840000 Liocarcinus maculatus 00 000000040404 Palaemon cf. adspersus 00 040000000000 Processa macrophthalma 00 0000000012000 Processa modica 00 000000000088 Upogebia deltaura 00 0000008004012 Isopoda Amakusanthura sp.00 000000000408

Cyathura carinata 46049616400002400000 131 estuary guadiana the in assemblages crustacean Dynamene sp. 00 000000400000 Eurydice sp 00 000000000040 Eurydice spinigera 00 000008000000 Gnathia oxyuraea 00 0000000001204 Lekanesphera levii 0 0 8 0 16 13 264 32 0 8 0 0 0 0 Natatolana neglecta 00 000000000404 Saduriella losadai 12 4 16 0 64 60 0 0 0 0 0 0 0 0 Synisoma sp. 001200000000000 Mysida Acanthomysis sp.083208000000000 Gastrosaccus sp.00 0000000040816 Paramysis sp. 00 000700000000 Petalophthalmidae 0 0 0 00000 400000 Tanaidacea Apseudes talpa 00 00000000040020 Leptochelia dubia 00 000700648024020 132 j. emilio sa’ nchez-moyano and isabel garci’a-asencio

Fig. 2. Dendrogram based on cluster analysis (A) and multidimensional scaling ordination (B) for all stations using Bray–Curtis similarities on species abundance. Stress coefﬁcient: 0.02.

similar to those of the cluster (Figure 2B), and furthermore, a areas, with the Carreras system functioning as a transitional spatial pattern can be observed from the upper estuary to the area. mouth area. The contribution in abundance of the crustacean orders in Values of univariate measures are shown in Table 3. The each area is plotted in Figure 3. The order Amphipoda was the number of species, diversity index, and evenness showed a best represented (ranging from 93% in the Carreras River to general pattern of increasing toward the mouth. These par- 48% in shallow marine stations) due to the contributions of ameters ranged over a wide interval (e.g. 3 and 25 species or different species in each area (e.g. Corophium multisetosum 0.20 and 2.23 on the diversity index at stations GU1 and in the upper estuary, Bathyporeia cf. pilosa in the middle H1B, respectively). However, total abundance did not show estuary, Corophium sextonae in the Carreras River, or a clear spatial trend, with the maximum values at stations Corophium aculeatum in deeper marine stations). Isopoda GU3 (high dominance of Corophium multisetosum and was the next most frequently represented order along the Cyathura carinata with 2100 and 496 ind./m2, respectively) Guadiana channel due to the abundance of Cyathura carinata, and CR1 (high dominance of Corophium sextonae with Lekanesphera levii and Saduriella losadoi; however they were 1468 ind./m2). scarcely represented in Carreras and marine areas. In According to the cluster and MDS groups, the spatial marine areas, the contribution of other orders was greater differences of these univariate parameters were tested by than in estuarine areas. For example, Decapoda was well rep- one-way ANOVAs with the station values as replicates resented in shallow marine stations with 33% due to the con- (Table 4). In all the parameters except abundance there tribution of Diogenes pugilator; meanwhile Tanaidacea were signiﬁcant differences between estuarine and marine showed the maximum percentage in the deeper marine crustacean assemblages in the guadiana estuary 133

Table 3. Number of species (S), total abundance (N: ind. m22), Pielou’s 83.4%) were mainly based on the exclusive presence and ′ evenness (J) and Shannon–Wiener diversity index (H ) for each station. high abundance of Corophium multisetosum and Cyathura Station S N J H′ carinata in the upper estuary and a higher abundance of Bathyporeia cf. pilosa and Lekanesphera levii in the middle GU1 3 368 0.19 0.20 estuary. Between the middle and the mouth estuary, the GU2 4 320 0.47 0.66 main differences were based on the presence of Bathyporeia GU3 8 2780 0.38 0.79 cf. pilosa and Saduriella losadoi in the upper areas of the GU4 5 200 0.41 0.65 estuary and the high abundance of the amphipod Melita her- GU5 4 472 0.45 0.62 gensis at the mouth. In spite of the middle estuary and the GU6 10 547 0.57 1.32 GU7 5 336 0.44 0.70 Carreras system seeming to be similar environmental zones, GU8 7 224 0.46 0.90 they showed 83.4% average dissimilarity. This was mainly CR1 22 1876 0.34 1.07 due to the high abundance of Corophium sextonae in the CR2 8 228 0.51 1.06 last area (average dissimilarity ¼ 77.7%). This species, H1 14 148 0.82 2.16 together with typical marine species such as Diogenes pugila- H1B 25 584 0.69 2.23 tor, was responsible for the separation of Carreras River and H2 8 128 0.83 1.72 the shallow marine area. An MDS analysis based on the abun- H2B 25 588 0.62 1.99 dance data of the dominant species (numerical dominance .4% at any station) to determine the species affinities showed six groups at similarity levels of about 40% Table 4. Results of the one-way analysis of variance for the spatial differ- (Figure 4). These groups matched the forward stations ences of univariate parameters. The homogeneous groups according to the groups and included the discriminating species shown in the Tukey test (P , 0.05) are indicated with a continuous line. F, statistic; ns, SIMPER analysis. not significant. Group key: UE (upper estuary); ME (middle estuary); MO Besides, MDS ordination of stations with superimposed (mouth); CA (Carreras River); M10 (marine 10 m); M20 (marine 20 m). values of abundance of the more characteristic species Parameter F P Homogeneous group showed that stations appeared distributed according to the presence of these species along the environmental gradient Number of species 6.9 ,0.01 UE ME MO CA M10 of the estuary (Figure 5). For example, there was a segregation CA M10 M20 of the three species of the amphipod genus Corophium along Abundance 0.4 ns — the study area; the isopod Cyathura carinata was located in Shannon diversity 12.9 ,0.001 UE ME MO CA the upper estuary; the amphipod Bathyporeia cf. pilosa CA M10 M10 M20 and the isopod Lekanesphera levii were located in the middle Evenness 7.8 ,0.01 UE ME MO CA M20 ME M10 M20 estuary; the isopod Saduriella losadoi was located along the main channel of Guadiana; and the decapod Diogenes pugilator was only found in the shallow marine stations. stations (9% due to the abundance of Apseudes talpa and Leptochelia dubia). Relationship between environmental and Using the SIMPER analysis, we obtained in each case the crustacean community best discriminating taxa between the groups of stations identified in the multivariate analyses (Table 5). Between the upper The results of the BIOENV analysis indicated that the best and middle estuary, the differences (average dissimilarity ¼ correlations always occurred with water characteristics and

Fig. 3. Relative abundance (%) of each crustacean order in the areas determined by multivariate analyses. 134 j. emilio sa’ nchez-moyano and isabel garci’a-asencio

Table 5. Average abundance (Av. Abun.) of the most relevant taxa of the conditions along the study zone. Especially, the main vari- stations located in each area identified in the multivariate analyses. Taxa ations in the composition of the crustacean community are listed in decreasing order according to their contribution to the were based on the differences between an estuarine and a average of the dissimilarity (Av. Diss.) between areas. Group key as marine environment. In each one, there were several crus- stated in Table 4. tacean assemblages related to the natural divisions of these Av. Av. Av. Ratio Contrib Cum. systems which we have defined as upper estuary, middle Abun Abun Diss % % estuary, mouth, Carreras River system, and shallow and deep marine areas. These areas agree with the results obtained UE ME for a study of the global soft-bottom macrofauna of the Average dissimilarity ¼ 83.4 Corophium 681 0 21.42 4.59 25.69 25.69 Guadiana River (Sanchez-Moyano et al., 2003, 2005) and for multisetosum other assemblages such as fish (Chıćharo et al., 2006a) or Bathyporeia cf. pilosa 23 263 17.71 1.88 21.24 46.94 plankton (Chıćharo et al., 2006b). Cyathura carinata 181 0 15.93 2.81 19.1 66.03 Most of the physicochemical parameters (e.g. heavy metals, Lekanesphera levii 2 98 12.92 1.49 15.49 81.53 nutrients and organic matter) have shown low or moderate values, even for estuaries. The sediment granulometry (predo- ME MO Average dissimilarity ¼ 64.5 minance of sands) and the hydrodynamic characteristics of Bathyporeia cf. pilosa 263 0 22.1 4.48 34.29 34.29 the river must facilitate the oxygenation of the substrate and Melita hergensis 0 168 21.06 11.49 32.67 66.96 the non-retention of organic elements (Savage et al., 2002). Saduriella losadai 41 0 10.56 1.15 16.39 83.35 This was highlighted by the low or moderate concentrations of these elements (e.g. total nitrogen, organic matter and ME CA TOC) found along the study zone. In relation to the heavy Average dissimilarity ¼ 77.7 Bathyporeia cf. pilosa 263 0 17.7 3.9 22.81 22.81 metals, our data agree with the results obtained in this zone Corophium sextonae 17 818 15.4 2.1 19.87 42.68 by Ruiz (2001), with a predominance of unpolluted or Saduriella losadai 41 0 8.51 1.25 10.95 53.64 lightly polluted conditions by most of the metals, except the Lekanesphera levii 98 4 8.13 1.3 10.47 64.1 Carreras River (highly polluted by Zn). In the Guadiana Phtisica marina 0 8 7.8 3.36 10.05 74.15 estuary, the intense pyrite extraction has ceased in the last decade, and consequently the potential sources of contami- CA M10 Average dissimilarity ¼ 97.7 nants may be the domestic sewages of the cities located near Corophium sextonae 818 0 18.54 4.92 18.9 18.9 to the mouth (Domingues et al., 2005) and some zones of Perioculodes 0 42 9.88 7.22 10.1 29.1 extensive agricultural production near the channel borders, longimanus although they do not seem to have significantly affected the Diogenes pugilator 0 36 9.55 4.89 9.8 38.9 geochemical levels of the river (Ruiz, 2001). Leucothoe lilljeborgi 0 10 6.75 3.15 6.9 45.8 Since external disturbed elements were absent or negligible, Phtisica marina 8 0 6.49 3.35 6.6 52.4 the typical characteristics of estuaries and areas of influence Gastrosaccus sp. 0 6 6.08 4.31 6.2 58.6 seem to be mainly responsible for the composition and distri- M10 M20 bution of the crustaceans along the study zone. In fact, the Average dissimilarity ¼ 79.5 natural gradients in salinity, granulometry, and organic Corophium aculeatum 2 288 10.75 3.24 13.5 13.5 content have been described as the most important factors Perioculodes 42 0 7.89 23.6 9.9 23.44 to explain the distribution and abundance of macrobenthic longimanus communities in numerous estuarine ecosystems (Wolff, Diogenes pugilator 36 0 7.62 7.12 9.5 33.02 1983; Rakocinski et al., 1997; Ysebaert et al., 2002; Mucha Ampelisca cf. ruffoi 0 40 7.33 4.33 9.2 42.23 et al., 2003; Sousa et al., 2006). According to BIOENV and Apseudes talpa 0 30 7.22 6.77 9.1 51.31 CCA analyses, the differences between crustacean commu- Synchelidium 0 22 6.62 5.42 8.3 59.63 longidigitatum nities were established by their locations along the estuary (indirectly by temperature, or directly by salinity and other sediment characteristics such as percentage sand, organic granulometry (maximum correlations of 0.69 with tempera- matter, TOC, or nitrogen). None of the pollutant parameters ture, and of 0.68 with temperature, salinity, percentage silt, (e.g. heavy metals) have shown a significant influence on the and TOC). community, which may demonstrate the scarce anthropo- The CCA (Figure 6) showed a clear division between genic influence in this estuary. estuarine and marine stations and a similar distribution The results of the univariate measures (number of species, of the six groups of stations identified by multivariate Shannon diversity or evenness) corroborate the typical pattern analyses. Again the environmental variables that best of the estuarine ecosystems: the existence of a gradient of explained the observed community distributions were enrichment and structuring of the communities from mainly water characteristics, and secondly granulometry and upstream points to marine sites (Rakocinski et al., 1997; organic matter. The Monte-Carlo test was significant for Ysebaert et al., 2003). From 76 species found, a total of 39 both axes (P ¼ 0.01). were found in the estuarine zone. Compared with other estuaries of near temperate zones, the Guadiana system is one of the richest in species. For example: 9 species were found in DISCUSSION Lima estuary (Sousa et al., 2006), 16 species were found in Mondego estuary (Marques et al., 1993), 5 in Douro estuary The crustaceans of the Guadiana River and area of influence (Mucha et al., 2003), and 15 in Minho estuary (Sousa et al., were distributed as a function of the different environmental 2008), all them located in Portugal but under various crustacean assemblages in the guadiana estuary 135

Fig. 4. Multidimensional scaling ordination based on the abundance data of the dominant species (numerical dominance .4% at any station). Stress coefﬁcient: 0.04.

Fig. 5. Multidimensional scaling ordination based on the species abundance with superimposed circles representing the relative abundance of some dominant species. Stress coefﬁcient: 0.02. 136 j. emilio sa’ nchez-moyano and isabel garci’a-asencio

Sousa et al., 2008). However, Baldo´ et al. (2000) reported a record of a unique specimen in the Guadalquivir estuary (the other great estuary from south-western Spain located 100 km eastward of Guadiana), which, according to these authors, could be a case of accidental introduction. The presence of this species in Guadiana demonstrates that there is a well-established population of Saduriella in this area. In the Guadiana mouth, the main dominant species was the amphipod Melita hergensis, widely distributed on the Atlantic coast of Europe and the Mediterranean and often located in localities with freshwater influences (Karaman, 1982). The spatial segregation of the three Corophium species is notice- able: C. multisetosum, in the upper estuary, is a typical species in fresh or weakly brackish habitats of the Atlantic coasts of Europe (Sousa et al., 2006, 2008); C. sextonae, located in the Carreras system and middle estuary, is a cosmo- politan species building tubes on algae, hydroids, or sponges; and C. aculeatum, located in the deeper marine zone, is so far considered as an endemic Mediterranean species from North Africa (Myers, 1982), so that our zone is now the westernmost limit of its known distribution. Finally, in the marine area we found a greater number of species and a lesser number of dominant species than in estuarine areas. In coastal areas, Fig. 6. CCA analysis plot for all stations from selected parameters of water and the environment fluctuates less and allows the establishment sediment: pH, temperature (Temp), salinity (Sal), % of sand, % of coarse sand, of more complex animal communities. organic matter content (OM) and % of dissolved oxygen (% Oxi). The The crustacean assemblages of the Guadiana estuary were percentage of variability explained by the axis is given. highly correlated with the salinity and the sediment characteristics. Salinity is a parameter that affects the physiological anthropogenic impacts (harbour activities, periodic dredging, functioning of all estuarine organisms and although most of nutrient and chemical sewages). The nearest two great estu- them are generally euryhaline, a few occur throughout the aries are Piedras River and the Tinto–Odiel system, both east- entire range of salinities (Sklar & Browder, 1998). ward of Guadiana on the south-west coast of Spain. Reductions of the freshwater flow directly affect saltwater Lo´pez-Serrano (1999) found up to 42 species in both subtidal intrusion and downstream sediment transport (Drake et al., and intertidal environments of Piedras estuary. Meanwhile, in 2002; Chıćharo et al., 2006b). Chıćharo et al. (2006a) argued the Tinto–Odiel system, one of the most polluted areas in the that the freshwater deficit caused by droughts and dams in world, with extremely high concentrations of heavy metals in the Guadiana estuary has resulted in increased salinities in the bottom sediments (Sainz & Ruiz, 2006), we have found the estuary which have affected the distribution, abundance, up to 20 species (unpublished data). The former is a small biomass and nursery sites of fish assemblages. Morais et al. bar-built estuary with very restricted fluvial supplies. Like (2009) have considered the river inflow as the most important Guadiana, the potential sources of contaminants are some factor in determining abiotic and biotic variability in the zones of extensive agricultural production and a small rec- Guadiana estuary. Changes in the spatial distribution of the reational harbour in the mouth. Therefore, the relatively macrofauna have also been observed in the Guadalquivir high biodiversity of Guadiana River seems justified by the estuary as a result of interannual changes in salinity (Drake scarce influence of pollutants together with their hydrodyn- et al., 2002). In this sense, it is expected that the crustacean amic characteristics. In contrast to most of the estuaries assemblages of the Guadiana estuary will also change their (Wolff, 1983), these conditions favour granulometry with a spatial distributions in response to the increased marine influ- predominance of medium sands and scarce fine elements. ence on upstream areas. Many species could elongate or Since granulometry is a determining factor in the distribution shorten their distributions within the estuary as a function of the soft-bottom macrofauna, this heterogeneous sediment of their abilities to tolerate different salinities (Drake et al., may provide many microhabitats able to shelter a greater 2002) and, in the last case this could indicate a significant diversity (Warwick et al., 1991; Sousa et al., 2006). change in the food web structure of this system. In relation to the identities of species, the crustacean Since the Alqueva Dam will reduce the river discharges and assemblages were similar to those of other temperate estuarine may cause changes in the abiotic characteristics such as gran- systems. In the upper estuary, with low salinity, there was a ulometry of sediments or salinity, this study provides baseline small number of species but high dominance of the amphipod information against which a monitoring programme or Corophium multisetosum and the isopod Cyathura carinata, follow-up studies could measure any significant effects of one of the most abundant crustacean species in European the dam or related impacts. The study of these assemblages estuaries (Cruz et al., 2003). In the middle estuary, the amphi- provides a number of advantages as a management tool for pod Bathyporeia cf. pilosa and the isopods Lekanesphera levii subsequent monitoring studies; for example, crustaceans are and Saduriella losadoi showed the major abundances. one of the groups of soft-bottom macrofauna that are most Saduriella losadoi is an estuarine species that has been sensitive to different environmental disturbances, so they restricted to the north-western Iberian Peninsula (e.g. offer important environmental information per se; the Holthuis, 1964; Marques et al., 1993; Cunha et al., 1999; degree of specialist intervention and the time required to crustacean assemblages in the guadiana estuary 137 analyse samples are reduced; it would be possible to extend the Consejerıá de Medio Ambiente (1997) Modelo de Gestioń del Estuario del study area, analysing higher numbers of samples per site and rıó Guadiana. Sevilla: Junta de Andalucıá. time period or completing the study within a much shorter Cravo A., Madureira M., Felıćia H., Rita F. and Bebianno M.J. (2006) time period; and the standard sampling methodology and Impact of outflow from the Guadiana River on the distribution of statistical tools allow cross-comparison with other sites or suspended particulate matter and nutrients in the adjacent coastal studies. Other possible ways of minimizing both costs and zone. Estuarine, Coastal and Shelf Science 70, 63–75. duration of study include focusing monitoring studies on Cruz S., Marques J.C., Gamito S. and Martins I. (2003) Autecology of the major structuring environmental parameters for these the isopod, Cyathura carinata (Krøyer, 1847) in the Ria Formosa communities, such as salinity and sediment characteristics. (Algarve, Portugal). Crustaceana 76, 781–802. Because the macrofauna estuarine community shows a natural spatial and temporal variability (especially in a Cunha M.R., Sorbe J.C. and Moreira M.H. (1999) Spatial and seasonal changes of brackish peracaridean assemblages and their relation to Mediterranean climatic area, where alternation between some environmental variables in two tidal channels of Ria de Aveiro severe droughts and rainy seasons is common), the establish- (NW Portugal). Marine Ecology Progress Series 190, 69–87. ment of a long term programme to evaluate the possible influence of the Alqueva Dam on the crustacean assemblages Dauvin J.C., Desroy N., Janson A.L., Vallet C. and Duhamel S. (2006) would be necessary. Since the Guadiana River is the main sedi- Recent changes in estuarine benthic and suprabenthic communities ment source for the entire northern Gulf of Cadiz (Gonza´lez resulting from the development of harbour infrastructure. Marine Pollution Bulletin 53, 80–90. et al., 2007), this monitoring programme should also be enlarged to the nearby marine area. Desrosiers G., Bellan-Santini D., Brethes J.C. and Willsie A. (1990) Variability in trophic dominance of crustaceans along a gradient of urban and industrial contamination. Marine Biology 105, 137–143. ˜ ACKNOWLEDGEMENTS Domingues R.B., Barbosa A. and GalvaoH.(2005) Nutrients, light and phytoplankton succession in a temperate estuary (the Guadiana, south-western Iberia). Estuarine, Coastal and Shelf Science 64, 249– We thank Dr Carlos Garcıá-Go´mez, Emilio Garcıá-Adiego, 260. David Ciudad and Javier Sańchez-Matamoros for their assist- ance in the field and in the laboratory; and the crew members Drake P., Arias A.M., Baldo F., Cuesta J.A., Rodrı´guez A., Silva-Garcia of the ship ‘AMA 6’ (Blas Brito and Jose´ MarıáA´ vila). A., Sobrino I., Garcia-Gonzalez D. and Fernandez C. (2002) Spatial and temporal variation of the nekton and hyperbenthos from a temperate European estuary with regulated freshwater inflow. Estuaries 25, 451–468. REFERENCES Gaston G.R., Rakocinski C.F., Brown S.S. and Cleveland C.M. (1998) Trophic function in estuaries: response of macrobenthos to natural Attrill M.J. and Rundle S.D. (2002) Ecotone or ecocline: ecological and contaminant gradients. Marine Freshwater Research 49, 833–846. boundaries in estuaries. Estuarine, Coastal and Shelf Science 55, ´ ˜ 929–936. Gonzalez R., Araujo M.F., Burdloff D., Cachao M., Cascalho J. and Corredeira C. (2007) Sediment and pollutant transport in the Baldo´ F., Megina C. and Cuesta J.A. (2000) Saduriella losadai Holthuis, Northern Gulf of Cadiz: a multi-proxy approach. Journal of Marine 1964 (Isopoda, Valvifera) in the Guadalquivir estuary (SW Spain). Systems 68, 1–23. Crustaceana 73, 1015–1017. Guerra-Garcia J.M. and Garcıá-Go´mez J.C. (2004) Crustacean assem- Buchanan J.D. and Kein J.M. (1984) Measurement of the physical and blages and sediment pollution in an exceptional case study: a chemical environment. In Holme N.L. and McIntyre A.D. (eds) harbour with two opposing entrances. Crustaceana 77, 353–370. Methods for the study of marine benthos. Oxford: Blackwell Scientific Publications, pp. 30–50. Herman P.M.J., Middelburg J.J., van de Koppel J. and Heip C.H.R. (1999) Ecology of estuarine macrobenthos. Advance in Ecology Bunn S.E. and Arthington A.H. (2002) Basic principles and ecological Research 29, 195–240. consequences of altered flow regimes for aquatic biodiversity. Environmental Management 30, 492–507. Holthuis L.B. (1964) Saduriella, a new genus of Isopoda Valvifera from north-western Spain. Zoologische Mededelingen 40, 29–35. Caetano M., Vale C. and Falcao M. (2006) Particulate metal distribution in Guadiana estuary punctuated by flood episodes. Estuarine, Coastal Karaman G.S. (1982) Family Gammaridae. In Ruffo S. (ed.) The and Shelf Science 70, 109–116. Amphipoda of the Mediterranean.Mońaco: Me´moires de L’Institut Oceánographique No. 13, pp. 245–364. Chıćharo M.A., Chıćharo L. and Morais P. (2006a) Inter-annual differences of ichthyofauna structure of the Guadiana estuary and adjacent Lo´pez-Serrano L. (1999) Estudio de la macrofauna bentońica de la desem- coastal area (SE Portugal/SW Spain): before and after Alqueva dam bocadura del rıó Piedras (Huelva). PhD thesis. Complutense University construction. Estuarine, Coastal and Shelf Science 70, 39–51. of Madrid, Spain. Chıćharo L., Chıćharo M.A. and Ben-Hamadou R. (2006b) Use of a Lourido A., Moreira J. and Troncoso J.S. (2008) Assemblages of hydrotechnical infrastructure (Alqueva Dam) to regulate planktonic peracarid crustaceans in subtidal sediments from the Rıá de Aldań assemblages in the Guadiana estuary: basis for sustainable water and (Galicia, NW Spain). Helgoland Marine Research 62, 289–301. ecosystem services management. Estuarine, Coastal and Shelf Science Marques J.C., Maranhao P. and Pardal M.A. (1993) Human impact 70, 3–18. assessment on the subtidal macrobenthic community structure in Clarke K.R. (1993) Non parametric multivariate analyses of changes in the Mondego Estuary (Western Portugal). Estuarine, Coastal and community structure. Australian Journal of Ecology 18, 117–143. Shelf Science 37, 403–419. Clarke K.R. and Ainsworth M. (1993) A method of linking multivariate Morais P., Chıćharo M.A. and Chıćharo L. (2009) Changes in a temper- community structure to environmental variables. Marine Ecology ate estuary during the filling of the biggest European dam. Science of Progress Series 92, 205–219. the Total Environment 407, 2245–2259. 138 j. emilio sa’ nchez-moyano and isabel garci’a-asencio

Morrisey D.J., Turner S.J., Mills G.N., Williamson R.B. and Wise B.E. Ter Braak C.J.F. (1990) Interpreting canonical correlation analysis (2003) Factors affecting the distribution of benthic macrofauna in through biplots of structure correlations and weights. Psychometrika estuaries contaminated by urban runoff. Marine Environmental 55, 519–531. Research 55, 113–136. Valiela I. (1995) Marine ecological processes. 2nd edition. New York: Mucha A.P., Vasconcelos M.T.S.D. and Bordalo A.A. (2003) Springer. Macrobenthic community in the Douro estuary: relations with trace metals and natural sediment characteristics. Environmental Pollution Vasconcelos R.P., Reis-Santos P., Fonseca V., Maia A., Ruano M., 121, 169–180. França S., Vinagre C., Costa M.J. and Cabral H.N. (2007) Assessing anthropogenic pressures on estuarine fish nurseries along Myers A.A. (1982) Family Corophiidae. In Ruffo S. (ed.) The Amphipoda of the Portuguese coast: a multi-metric index and conceptual approach. the Mediterranean.Mońaco: Me´moires de L’Institut Oceánographique Science of the Total Environmental 374, 199–215. No. 13, pp. 185–208. Rakocinski C.F., Brown S.S., Gaston G.R., Heard R.W., Walker W.W. Warwick R.M. (1988) The level of taxonomic discrimination required to and Summers J.K. (1997) Macrobenthic responses to natural and detect pollution effects on marine benthic communities. Marine contaminant-related gradients in Northern Gulf of Mexico estuaries. Pollution Bulletin 19, 259–268. Ecological Applications 7, 1278–1298. Warwick R.M., Goss-Custard J.D., Kirby R., George C.L., Pope N.D. Ruiz F. (2001) Trace metals in estuarine sediments from the and Rowden A.A. (1991) Static and dynamic environmental factors South-western Spanish Coast. Marine Pollution Bulletin 42, 482–490. determining the community structure of estuarine macrobenthos in SW Britain: why is the Severn estuary different? Journal of Applied Sainz A. and Ruiz F. (2006) Influence of the very polluted inputs of the Ecology 28, 329–345. Tinto–Odiel system on the adjacent littoral sediments of south- western Spain: a statistical approach. Chemosphere 62, 1612–1622. Weisberg S.B., Ranasinghe J.A., Dauer D.M., Schaffner L.C., Diaz R.J. Sańchez-Moyano J.E. and Garcıá-Go´mez J.C. (1998) The arthropod and Frithsen J.B. (1997) An estuarine benthic index of biotic integrity community, especially Crustacea, as a bioindicator in Algeciras Bay (B-IBI) for Chesapeake Bay. Estuaries 20, 146–158. (Southern Spain) based on a spatial distribution. Journal of Coastal ´ ´ Research 14, 1119–1133. Wolanski E., Chıcharo L., Chıcharo M. and Morais P. (2006) An ecohydrology model of the Guadiana Estuary (South Portugal). Estuarine, Sańchez-Moyano J.E., Garcıá-Adiego E.M., Garcıá-Asencio I. and Coastal and Shelf Science 70, 85–97. Garcıá-Go´mez J.C. (2003) Influencia del gradiente ambiental sobre la distribucioń de las comunidades macrobentońicas del estuario Wolf W.J. (1983) Estuarine benthos. In Ketchum B.H. (ed.) Estuaries del rıó Guadiana. Boletıń del Instituto Espanõl de Oceanografıá 19, and enclosed areas. Amsterdam: Elsevier, pp. 151–182. 123–133. Ysebaert T. and Herman P.M.J. (2002) Spatial and temporal variation in Sańchez Moyano J.E., Garcıá Asencio I., Garcıá Adiego E., Garcıá benthic macrofauna and relationships with environmental variables in Go´mez J.C., Leal Gallardo A., Ollero de Castro C. and Fraidıás J. an estuarine, intertidal soft-sediment environment. Marine Ecology (2005) Caracterizacioń ambiental de los fondos del estuario del rıó Progress Series 244, 105–124. Guadiana. Sevilla: Consejerıá de Medio Ambiente, Junta de Andalucıá. Ysebaert T., Meire P., Herman P.M.J. and Verbeek H. (2002) Savage C., Elmgren R. and Larsson U. (2002) Effects of sewage-derived Macrobenthic species response surfaces along estuarine gradients: nutrients on an estuarine macrobenthic community. Marine Ecology prediction by logistic regression. Marine Ecology Progress Series 225, Progress Series 243, 67–82. 79–95. Sklar F.H. and Browder J.A. (1998) Coastal environmental impacts brought about by alterations to freshwater flow in the Gulf of and Mexico. Environmental Management 22, 547–562. Ysebaert T., Herman P.M.J., Meire P., Craeymeersch J., Verbeek H. and Sousa R., Dias S. and Antunes J.C. (2006) Spatial subtidal macrobenthic Heip C.H.R. (2003) Large-scale spatial patterns in estuaries: estuarine distribution in relation to abiotic conditions in the Lima estuary, NW macrobenthic communities in the Schelde estuary, NW Europe. of Portugal. Hydrobiologia 559, 135–148. Estuarine, Coastal and Shelf Science 57, 335–355. Sousa R., Dias S., Freitas V. and Antunes C. (2008) Subtidal macrozoo- benthic assemblages along the River Minho estuarine gradient (north- Correspondence should be addressed to: west Iberian Peninsula). Aquatic Conservation: Marine and Freshwater J.E. Sańchez-Moyano Ecosystems 18, 1063–1077. Departamento Fisiologıá y Zoologıá Ter Braak C.J.F. (1986) Canonical correspondence analysis: a new eigen- Facultad de Biologıá, Universidad Sevilla vector technique for multivariate direct gradient analysis. Ecology 67, Avenida Reina Mercedes 6, 41012 Sevilla, Spain 1167–1179. email: [email protected]