Animal Biodiversity and Conservation 34.1 (2011) 141 Ecological features of Terebellida fauna (Annelida, Polychaeta) from Ensenada de San Simón (NW Spain) E. Cacabelos, J. Moreira, A. Lourido & J. S. Troncoso Cacabelos, E., Moreira, J., Lourido, A. & Troncoso, J. S., 2011. Ecological features of Terebellida fauna (Annelida, Polychaeta) from Ensenada de San Simón (NW Spain). Animal Biodiversity and Conservation, 34.1: 141–150. Abstract Ecological features of Terebellida fauna (Annelida, Polychaeta) from Ensenada de San Simón (NW Spain).— Ecological features of Terebellida (Annelida, Polychaeta) inhabiting the intertidal and subtidal soft–bottoms of Ensenada de San Simón (NW Spain) were analysed by means of quantitative sampling. A total of 4,814 specimens belonging to five families (Ampharetidae, Pectinariidae, Terebellidae, Trichobranchidae and Sabellariidae) and ten species were collected in a variety of substrata and depths. Ampharetidae was the numerically dominant family mostly due to the abundance of Ampharete finmarchica and Melinna palmata; these species accounted for up to 94% of the total Terebellida abundance. Intertidal areas colonised by the seagrasses Zostera marina L. and Z. noltii Hornem. One thousand eight hundred and thirty–two harboured low densities of Terebellida, whereas the deeper subtidal muddy bottoms showed high abundances of ampharetids. Multivariate analyses suggested that Terebellida assemblages are highly correlated with sediment composition. Key words: Terebellida, Polychaeta, Biodiversity, Soft bottoms, Ensenada de San Simón, Atlantic Ocean. Resumen Características ecológicas de los Terebellida (Annelida, Polychaeta) de la Ensenada de San Simón (NO de España).— Las características ecológicas de los Terebellida (Annelida, Polychaeta) presentes en los fondos blandos intermareales y sublitorales de la Ensenada de San Simón (NW España) son analizadas por medio de muestreos cuantitativos. Un total of 4.814 individuos pertenecientes a cinco familias (Ampharetidae, Pec- tinariidae, Terebellidae, Trichobranchidae y Sabellariidae) y diez especies fueron recolectados en distintos sustratos y profundidades. Los Ampharetidae fueron la familia dominante en términos numéricos debido a la abundancia de Ampharete finmarchica y Melinna palmata; estas especies constituyeron hasta el 94% del total de los Terebellida. Las áreas intermareales estaban colonizadas por las fanerógamas Zostera marina L. y Z. noltii Hornem. Mil ochocientos treinta y dos presentaron bajas densidades de Terebellida; por el con- trario, los fondos fangosos sublitorales más profundos mostraron una gran abundancia de anfarétidos. Los análisis multivariantes indicaron que las agrupaciones de Terebellida estaban altamente correlacionadas con la composición del sedimento. Palabras clave: Terebellida, Polychaeta, Biodiversidad, Fondos blandos, Ensenada de San Simón, Océano Atlántico. Eva Cacabelos, Antía Lourido & Jesús S. Troncoso, Área de Biología Animal, Fac. de Ciencias del Mar, Univ. de Vigo, 36310 Lagoas–Marcosende, Vigo, España (Spain).– Juan Moreira, Depto. de Biología (Zoología), Fac. de Ciencias, Univ. Autónoma de Madrid, Cantoblanco, 28049 Madrid, España (Spain). Corresponding author: Eva Cacabelos. E–mail: [email protected] ISSN: 1578–665X © 2011 Museu de Ciències Naturals 142 Cacabelos et al. Introduction Intertidal and shallow subtidal areas of this inlet are colonised by Zostera noltii Hornem. 1832 and Polychaetes play a major role in the functioning of Z. marina L. meadows, and their soft bottoms are benthic communities in terms of recycling and rewor- mainly muddy with high organic matter contents king of marine sediments (Hutchings, 1998). They are (Vilas et al., 1995). The inlet is subjected to large often the numerically dominant macrobenthic taxon in freshwater inputs, resulting in salinity fluctuations on marine sediments (Jumars & Fauchald, 1977). Due both a tidal and seasonal basis (Nombela & Vilas, to their high diversity of trophic behaviours and their 1991). In addition, culture of mussels on rafts is a great ability to adapt to different habitats (Fauchald common practice in the inlet. & Jumars 1979), they are considered good indica- Terebellida specimens were collected in Ensenada tors of community structure in benthic invertebrate de San Simón during XI and XII 99. Twenty–nine assemblages (Olsgard et al., 2003). Moreover, some sites were sampled (fig. 1) with a van Veen grab polychaetes are either sensitive or tolerant to a variety (0.056 m2; five replicates per site) and samples were of perturbations and therefore have been regarded as sieved through a 0.5 mm mesh. The retained material indicators of marine environmental conditions (Grall & was fixed in 10% buffered formalin, and fauna were Glémarec, 1997; Tomassetti & Porrello, 2005). sorted from the sediment and preserved in 70% In the search for strategies and management plans ethanol for later identification. Temperature and pH to achieve sustainable use of protected areas, quick were measured in situ both from the water and the measures of their biodiversity are needed. In this sediment. Additional samples were taken at each site sense, among the polychaetes, Terebellida species for later sediment analyses (calcium carbonate and frequently represent an important component of the total organic matter contents and grain–size analysis; benthic habitat assemblages in terms of abundance see Cacabelos et al., 2008b for further details). and biomass, and they have been found to be a We determined several cological indices (total good indicator of polychaete species richness and abundance, number of species, Shannon–Wiener’s main faunal patterns in biodiversity studies of marine diversity index, Pielou’s evenness index and Soyer’s benthic communities (Olsgard et al., 2003). The order frequency index) depending on the presence and Terebellida consists of large, long–lived and taxonomi- abundance of the species for each site. Assemblages cally well–defined polychaetes that occur at all depths were determined using non–parametric multivariate and in all sediment types (Olsgard et al., 2003). They techniques (Plymouth Routines of the Multivariate are usually tubicolous and surface deposit–feeders Ecological Research software package, PRIMER; (Fauchald & Jumars, 1979), irrigating the substrate Clarke & Warwick, 1994), and SIMPER analysis was and actively transporting oxygen into their burrows, used to identify which species contributed most to and therefore considerably affecting the sediments dissimilarity among the groups of sites determined by and their associated faunal communities (Fauchald classification and ordination analyses. Relationships & Jumars, 1979). between abundance of Terebellida and environmental Numerous faunistic and ecological works on the variables were studied using Spearman’s non–para- macrobenthic communities of the Galician coasts (NW metric correlation coef ficients and the BIOENV pro- Iberian peninsula), and specially their highly produc- cedure (PRIMER package). Environmental variables tive rias, have been carried out in recent years (Gar- expressed in percentages were previously transfor- mendia et al., 1998; Olabarria et al., 1998; Troncoso med by log (x + 1) and all of them were normalised. et al., 2005; Moreira et al., 2006). The soft–bottom polychaete faunas of the rias have been exhaustively studied (Parapar et al., 2000; Moreira et al., 2006; Results Cacabelos et al., 2008a; Lourido et al., 2008). Never- theless, the role of terebellids is less understood. We Physical characteristics of the water and sediments here describe the diversity and assemblage structure of Ensenada de San Simón are shown in table 1. of the order Terebellida inhabiting intertidal and sub- Subtidal soft bottoms were characterised by a pre- tidal soft substrata at Ensenada de San Simón (NW dominance of muddy sediments (silt/clay fraction: Iberian Peninsula), a Special Conservation Zone of the 67.1% ± 5.4, mean ± SE) with a high total organic Nature 2000 Network. Furthermore, we investigated matter (17.7% ± 1.8) and low calcium carbonate the main abiotic factors structuring the Terebellida content (6.8% ± 0.8). Sandy sediments were present populations at Ensenada de San Simón and tested in intertidal areas (silt/clay fraction: 37.7% ± 11.0), whether the Terebellida is a useful indicator group to where the lower organic matter contents were found predict the species’ richness in soft bottoms of the (12.9% ± 3.6). Polychaetes were the numerically Galician rias, as suggested by Olsgard et al. (2003) dominant macrobenthic taxon in Ensenada de San for the North Atlantic. Simón (Cacabelos et al., 2008b). A total of 4,814 specimens of Terebellida belon- ging to five families and ten species were identified Material and methods (table 2). The inner intertidal area of the inlet, co- lonised by the seagrasses Zostera marina and Z. Ensenada de San Simón is located in the inner noltii, showed very low abundance or total absence part of the Ría de Vigo, between 42º 17' and 42º (sites 1, 2, 4, 5, 6, 10, 15 and 29) of Terebellida. 21' N and between 8º 37' and 8º 39' W (fig. 1). Most of the Terebellida were found in muddy subtidal Animal Biodiversity and Conservation 34.1 (2011) 143 Río Xunqueira N Pontesampaio Ría Río Oitabén–Verdugo de Vigo Ensenada 1 2 3 de San Simón 5 4 Iberian 6 9 peninsula 7 8 10 Soutoxusto 14 15 11 12 13 Ría de Vigo 16 17 18 19 20 22 42º 10' N 23 24 25 5 211510 28 26 27 29 Redondela 1 km Río Alvedosa 8º 36' O Fig. 1. Location of Ensenada de San Simón