Spatial distribution patterns of demersal and epibenthic communities on the Galician continental shelf (NW Spain)

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s 72 (2008) 87–100www.elsevier.com/locate/jmarsys

Journal of Marine System

Spatial distribution patterns of demersal and epibenthic communitieson the Galician continental shelf (NW Spain)

Alberto Serrano a,⁎, Izaskun Preciado a, Esther Abad a, Francisco Sánchez a,Santiago Parra b, Inmaculada Frutos b

a Instituto Español de Oceanografía, Centro Oceanográfico de Santander, Promontorio de San Martín s/n, 39004, Santander, Spainb Instituto Español de Oceanografía, Centro Oceanográfico de A Coruña, Muelle de las Ánimas, s/n, 15001, A Coruña, Spain

Received 17 September 2006; received in revised form 30 May 2007; accepted 31 May 2007Available online 4 December 2007

Abstract

Spatial distribution patterns of epibenthic communities on the Galician continental shelf were studied using multivariatemethods. Data came from 5 surveys carried out in 2002, 2003 and 2004. Beam trawls and otter trawls were used to study epibenthiccommunities along 8 transects perpendicular to the coastline. The role of depth, season, latitude and sediment characteristics wasexamined. Seven habitats were described according to bathymetry and sediment characteristics. There were weak linearrelationships between environmental variables and species richness, biomass and species diversity. However, the canonical analysisshowed that depth and sediment characteristics greatly influence smaller epibenthic communities sampled by beam trawl. Sixassemblages were obtained for beam trawls: inner shelf mud, very fine sands, and fine sands, middle shelf sands, and outer shelfvery fine sands, and fine sands. Five assemblages were identified for larger-sized and swimming epibenthos sampled with ottertrawls. These assemblages were also determined according to depth and sediment type but sediment characteristics were lessimportant. Otter trawl assemblages were the same as the beam trawl ones, except for on the outer shelf where no differencesbetween sediment type were detected. For both gears, inner and outer shelf assemblages displayed a higher biotic variability thanthe middle shelf, as a consequence of a higher environmental heterogeneity. Typifying species were mainly eurytopic in the middleshelf, whereas eurytopic and stenotopic species characterised the inner and outer shelves.© 2007 Elsevier B.V. All rights reserved.

Keywords: Epibenthic communities; Faunal assemblages; Depth; Sediment type; Organic matter; NW Atlantic; Galician shelf

1. Introduction

The megaepibenthic fauna of the Galician continen-tal shelf is well documented by the surveys carried outby the Instituto Español de Oceanografía (IEO) every

⁎ Corresponding author. Centro Oceanográfico de Santander,Promontorio de San Martín s/n, 39004, Santander, Spain. Tel.: +34942 291060; fax: +34 942 275072.

E-mail address: [email protected] (A. Serrano).URL: http://www.ieo-santander.net (A. Serrano).

0924-7963/$ - see front matter © 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.jmarsys.2007.05.012

autumn since 1983 (Olaso, 1990; Sánchez, 1993; Fariñaand Pereiro, 1995; Sánchez et al., 2002). A few otherstudies have also focused on macroendobenthic faunaand its relationships with sediments and upwelling–outwelling processes (Tenore et al., 1984; López-Jamarand González, 1987; López-Jamar et al., 1992). How-ever, little is known regarding small-sized epibenthiccommunities and there is a lack of information aboutthe role of environmental factors in spatial distributionpatterns.

mailto:[email protected]

http://www.ieo-santander.net

http://dx.doi.org/10.1016/j.jmarsys.2007.05.012

88 A. Serrano et al. / Journal of Marine Systems 72 (2008) 87–100

Following the Prestige oil spill (POS) in November2002, five surveys were carried out in winter 2002,spring 2003, autumn 2003, spring 2004 and autumn2004. Using data obtained in these surveys, effects ofthe POS on Galician shelf benthic communities hasalready been described in several papers (Serrano et al.,2006b; Sánchez et al., 2006). In these papers no effectson community structure were detected, only decreaseand rebound shifts in the biomass of some indicatorspecies. Here, faunal and environmental informationobtained in these surveys was used with the aim ofdescribing the structure of epibenthic communities in aless known area.

Benthic communities development and structure isclosely linked to sediment characteristics and to the inputof organic matter to the sediment (Van Weering andMcCave, 2002). Regarding sediment characteristics,there are two large provinces in the study area: North andWest of Cape Finisterre, dominated by a shelf sandblanket, and South Cape Finisterre (which coastline ischaracterised by sea drowned valleys known as RíasBaixas) with mud andmuddy sands in the inner shelf andsands in the middle and outer shelf (Rey and Medialdea,1989; López-Jamar et al., 1992). Rocky outcrops in thearea are mainly located on the inner shelf.

Attending food availability, pelagic productivity isclearly the main source of organic matter in the sed-iments, together with lateral advection (López-Jamaret al., 1992; Van Weering and McCave, 2002). Nutrientenrichment associated with upwelled water results inhigh pelagic productivity on the northwestern Iberianshelf (Tenore et al., 1995; Guisande et al., 2001; Jointet al., 2002). Intense, wind-driven upwelling is commonin summer and more persistent off and north of CapeFinisterre (Álvarez-Salgado et al., 2002; Arístegui et al.,2006). On the other hand, the estuarine systems of theRías Baixas supply a large amount of organic enrich-ment to the shelf regime by means of outwelling (coastalrivers and embayments with intense mussel aquacul-ture). These two sources of organic matter, vertical andlateral respectively, determine differences between thetwo sedimentary provinces: the northern and westernshelf is characterised by episodic enrichment (upwel-ling), hence covered with a lower organic content sands,whereas southern shelf sediments are also enrichedby the organic matter advected from the Rías Baixas(López-Jamar et al., 1992). Therefore, organic-enrichedmud is located in front of the Rías Baixas mainly on theinner shelf (Tenore et al., 1984), unlike the nearbyCantabrian sea continental shelf where muddy bottomsare located on the outer shelf (Rey and Medialdea, 1989;Sánchez et al., 2002; Serrano et al., 2006a).

The aim of the present work was to describe thespatial structure of the epibenthic communities of theGalician Atlantic shelf and to elucidate the influence ofdepth, season, latitude and sediment characteristics.

2. Materials and methods

The study area includes the Galician continental shelf(NW Spain, NE Atlantic Ocean) between 70 m and300 m depth. Following the POS, five surveys werecarried out in winter 2002, spring 2003, autumn 2003,spring 2004 and autumn 2004. A total of 8 transectsperpendicular to the coastline, with stations located atthree different depth strata (A: 70–120, B: 121–200,C: 201–300m), were established (Fig. 1). At each stationseveral samplers were used in order to study the differentcompartments of benthic and demersal fauna (Serranoet al., 2006b). To study demersal and megabenthic fauna,a baca 44/60 otter trawl gear was used. The sampling unitwas made up of 30-minute hauls during daytime at aspeed of 3 knots. The number of individuals and weightof each species were obtained from each haul. A beamtrawl with a horizontal opening of 3.5 m and a verticalopening of 0.6 m (mesh size of 10mm)was used to studythe macro- and megabenthic epifauna. Hauls lasted15 min at a mean speed of 2.5 knots. Both trawl gearswere monitored using a Scanmar net control system. Themean area swept was 54728±1532m2 in otter trawls and3307±192 m2 in beam trawls. Sediment samples werecollected using a modified Bouma box corer (0.0175 m2

surface area and 15 to 20 cm sediment depth) in the depthstrata A and B. In the deepest stratum (stratum C), a largebox corer of 0.25 m2 sampling surface area was used.Particle size analysis was performed by a combination ofdry sieving and sedimentation techniques (Buchanan,1984). Organic matter content of the sediment, re-ported as % OM was estimated as weight loss of dried(100 °C, 24 h) samples after combustion (500 °C,24 h). The main sedimentary characteristics were de-termined: percentage of organic matter, mean particlediameter (Q50, in mm), sorting coefficient (S0), percen-tage of coarse sands (N500 μm), fine sands (62–500 μm)and mud (b62 μm). Samples were classified into threesedimentary types according to relative abundance ofparticle size classes: mud, very fine sands and fine sands.

An inventory of 277 species in beam trawls and175 in otter trawls were obtained in the five surveys(complete lists in www.ecomarg.net). Species appearingin less than 5% of hauls were removed aiming to reducethe percentage of zeros in the matrix. The matrix usedin the analysis contains 134 species (113 present inbeam trawl samples and 85 in otter trawl samples). The

http://www.ecomarg.net

Fig. 1. Study area showing the location of sampling stations. Numbers indicate sediment type: 1—mud, 2—very fine sands, 3—fine sands.

89A. Serrano et al. / Journal of Marine Systems 72 (2008) 87–100

species abundance indices for both gears were pooledin a single table (Appendix), choosing the maximumabundance of both gears in each assemblage described.

For each haul, richness index (number of speciesby haul), biomass index (weight in g by haul) andShannon–Wiener diversity index were obtained. ASpearman rank order correlation was used to assessthe level of association of the three indices with theset of environmental variables (i.e. depth, latitude, or-ganic matter, mean particle diameter, sorting coefficient,coarse sand, fine sand and mud).

Spatial distribution of richness and diversity was ob-tained from the yearly autumn survey data in the period2003 to 2005 (mean N=60), with the aim of obtaining ahigher sampling coverage. Maps were obtained usinggeostatistic procedures (Sánchez et al., 2002).

A Redundancy Analysis (RDA) was used to assessthe amount of variation in species biomass per haul inrelation to a set of environmental variables assumedto be important in community structure (i.e. season,latitude, depth, percentage of organic matter, meanparticle diameter, sorting coefficient and percentage ofcoarse sands, fine sands and mud). RDA calculationswere based on log-transformed abundances of the 134

selected species. The statistical significance of the firstand all canonical axes together was tested with MonteCarlo tests using 999 permutations under the reducedmodel. RDA results were presented graphically in a bi-dimensional ordination diagram generated by biplotscaling focusing on inter-species distances, in whichsamples are represented by points and environmentalvariables by vectors.

Species typifying each RDA group were determinedusing a SIMPER analysis (similarity percentages)obtained from a Bray–Curtis similarity matrix (Clarkeand Warwick, 1994).

A Kruskal–Wallis 1-way ANOVA on ranks was usedto assess differences in species richness, biomass andspecies diversity between assemblages resulting fromthe RDA analysis. When significant differences weredetected, a pairwise “a posteriori”Dunn's test was run toidentify the groups responsible for these differences.

3. Results

Seven habitats were defined taking into accountdepth and sedimentary variables together (without fau-nal information): I) inner shelf mud with high organic


matter content, located in front of Rías Baixas; II) innershelf very fine sands, located in the north of FinisterreCape; III) inner shelf fine sands, located in the north ofFinisterre Cape in front of the mouth of the main rías;IV) middle shelf very fine sands; V) middle shelf finesands; VI) outer shelf very fine sands; VII) outer shelffine sands. These seven habitats are distributed follow-ing a patchy pattern (Fig. 1), which is mainly controlledby the transport and sedimentation mechanisms de-scribed in the Introduction.

Significant correlations between environmental vari-ables and ecological indices were detected, althoughmost of them with extremely weak values (Table 1).Depth shows a negative correlation with biomass andspecies richness for otter trawls and only with biomassfor beam trawls. Latitude also displays a positive cor-relation with species richness for beam trawls. Amongthe sediment characteristics, significant correlationswere found for beam trawls, but not for otter trawl.

Spatial distribution of species richness and diversityon the Galician shelf (Fig. 2), obtained from the widersurvey database, is different if we consider all species oronly fish. Species richness seems to be depth-dependentin fish species, with higher values in the inner shelfstations. When we consider invertebrate and fish speciestogether (total species richness), we see that distributionis controlled by factors others than depth (e.g. nutrients,substrate type). The diversity pattern is the opposite: the

Table 1Spearman rank order correlation (r) between environmental variablesand species richness (S), biomass (W) and species diversity (H′) forbeam trawls and otter trawls

S W H′

Beam trawl (n=114)Depth −0.100 −0.460⁎⁎ 0.152Latitude 0.205 ⁎ 0.010 0.171Organic matter (%) 0.049 −0.005 −0.047Mean particle diameter 0.060 −0.236 ⁎ 0.204 ⁎

Sorting coefficient (S0) 0.104 0.105 −0.028Coarse sand (%) 0.157 0.110 0.061Fine sand (%) −0.059 −0.205 ⁎ 0.184 ⁎

Mud (%) 0.026 0.196 ⁎ −0.193 ⁎

Otter trawl (n=126)Depth −0.288 ⁎⁎ −0.300⁎⁎ −0.161Latitude 0.156 0.108 0.167Organic matter (%) 0.094 0.080 −0.026Mean particle diameter 0.006 −0.116 0.114Sorting coefficient (S0) 0.093 0.120 −0.090Coarse sand (%) 0.137 0.117 0.096Fine sand (%) −0.060 −0.079 0.086Mud (%) 0.026 0.065 −0.108⁎: pb0.05; ⁎⁎: pb0.001.

distribution of total species indices is depth-dependentbut the distribution of fish species is controlled by otherfactors (e.g. dominance of plankton-feeders, juveniles).Fig. 2 shows that there are hotspots where richness and/or diversity reach their highest values: some areas in theouter shelf (in front of Rías Baixas, and the deepest andnorthernmost part of the shelf, known as “El Fondón”fishing ground) and the shelf in front of Estaca cape(northernmost cape).

The first three axes of beam trawl RDA explained21.7% of species variation in the species per haulmatrix, and 66.4% of variation in the “species-environ-ment” matrix. The variance explained in the otter trawlanalysis was 25.2% and 73.4% respectively. The MonteCarlo tests indicated that both the first axis (pb0.001)and all canonical axes together (pb0.001) weresignificant. Both beam trawl (Fig. 3a) and otter trawl(Fig. 3b) ordinations showed that depth is stronglycorrelated with Axis 1. Sediment typology was shown tobe the second factor structuring epibenthos. In the beamtrawl RDA, the second axis was correlated with asediment gradient. Positive quadrants were related toheterogeneous and organic-enriched muddy sediments,whereas fine sands (poorer in organic matter) wereassociated with negative sectors. Axis 2 in the otter trawlanalysis (Fig. 3b) also displayed a strong relationshipwith sediment typology, but was affected more by par-ticle diameter than by organic matter content. Latitudeshowed a positive correlation with fine sands with lowerorganic matter content in both analyses, and was morerelevant in the otter trawl analysis. This correlationreflects the sedimentary distribution in the area, withmuddier sediments in the southern shelf in relation tothe “Rías Baixas” estuarine system. Likewise, seasonalvariables also made a low contribution to axis building,showing low discriminatory power.

Discrimination of samples followed a primary depthand secondary sediment pattern in both analyses. Beamtrawl analysis (Fig. 4a) shows three well-defined groupson the inner shelf: mud (I-M), very fine sands (I-VFS)and fine sands (I-FS). Middle shelf samples make up asingle group, without sedimentary discrimination (all ofthem are very fine and fine sand stations, M-S). In theouter shelf beam trawl hauls, there is a discriminationbetween very fine sands (O-VFS) and fine sands (O-FS),which is less clear than in inner shelf samples (Fig. 4a).

Otter trawl samples (Fig. 4b) show less discriminatedgroups than beam trawl ones, due to the lower weightof sedimentary factors in the analysis. Inner shelf group-ing is also clear, showing the same three well-definedgroups: mud (I-M), very fine sands (I-VFS) and finesands (I-FS). However, middle and outer shelf samples

Fig. 2. Spatial distribution of fish (left) and total (right) species richness and diversity (from the 2003–2005 otter trawl demersal surveys, meann=60).


make up two bathymetric groups without sedimentarydiscrimination: a middle shelf sand group (M-S), and anouter shelf sand group (O-S).

Percentage of organic matter is a more discriminatingfactor in beam trawls than in otter trawls. In both cases itis positively correlated with mud. Inner shelf mud is therichest habitat in organic matter and is located in frontof the “Rías Baixas” estuarine system, which explainsthe negative correlation in RDA between % OM andLatitude.

Fig. 5 shows the ordination of species, superposed onenvironmental variables and sample plots. These resultsare consistent with the SIMPER analysis obtained from

the similarity matrix between samples (Tables 2 and 3),and with the species abundance indices (Appendix).

Several species are ubiquitous, with similar abun-dance in all the assemblages: e.g. monkfish Lophiuspiscatorius, white octopus Eledone cirrhosa, and thesea star Astropecten irregularis (Appendix). Otherspecies inhabit all depths and sediment type environ-ments, but are more abundant in particular depth strata(Appendix). Hake (Merluccius merluccius), and theflatfishes Arnoglossus laterna and Microchirus varie-gatus typify the inner and middle shelf (Tables 2 and 3),and catshark (Scyliorhinus canicula) is a key species inthe three inner shelf assemblages (although with lower

Fig. 3. RDA ordination plots of environmental variables for the beam trawl (a) and the otter trawl sampling (b). % OM = weight percentage of organicmatter, Q50 = mean particle diameter, S0 = sorting coefficient.


biomass in mud than in sands). Lepidorhombus bosciiand bluemouth (Helicolenus dactylopterus) typify themiddle and outer shelf (Table 3).

Besides these eurytopic species, assemblages de-scribed by RDA are typified by more stenotopic species:Inner shelf mud (I-M) is characterised by the poly-

Fig. 4. RDA ordination plots of samples for the beam trawl (a) and the otter tramiddle shelf—pale grey; outer shelf—dark grey; and sediment type: mud—ciabbreviations see Results.

chaete Sternaspis scutata (almost exclusive to the hab-itat known as Sternaspis mud), accompanied by thecrustacean Alpheus glaber (Table 3). Inner shelf veryfine sands (I-VFS) are typified by Turritella communis(Table 2), with huge abundance in some hauls (meanbiomass of 8.7 kg/km2, Appendix), and in otter trawls

wl sampling (b). Symbols show bathymetric strata: Inner shelf—white;rcles; very fine sands—triangles; fine sands—squares. For assemblages

Fig. 5. RDA ordination plots of species for the beam trawl (a) and the otter trawl sampling (b). Dashed lines represent sample groups. Speciesabbreviations appear in Appendix.


by red bandfish (Cepola macrophthalma) (Table 3). Interms of biomass, seabream (Pagellus acarne), thornyray (Raja clavata), John Dory (Zeus faber), hermit crabs(Anapagurus laevis, Anapagurus petiti, Pagurus pri-

Table 2SIMPER results of beam trawl samples: species typifying groups (5 more di

I-M group AvSim(%)=52.2

Species Av.W Sim(%)

A. laterna 1.12 11.7S. scutata 0.51 7.7A. glaber 0.17 7.0M. variegatus 0.13 6.7E. cirrhosa 0.66 5.8

I-FS group AvSim(%)=54.0

Species Av.W Sim(%)

C. lyra 0.76 14.2A. laterna 0.64 13.6A. irregularis 0.37 11.4C. gurnardus 0.30 9.0P. bernhardus 0.03 3.8

O-VFS group AvSim(%)=50.6

Species Av.W Sim(%)

G. argenteus 0.63 11.1L. boscii 0.38 11.0G. macrophthalmus 0.14 9.4P. heterocarpus 0.67 6.8A. irregularis 0.05 5.6

AvSim(%): mean intergroup similarity; Av.W: mean biomass in the group (k

deaux, Pagurus excavatus), molluscs (Aporrhais pespe-licani, Aporrhais serresianus, Sepia elegans and Venusstriatula), and the sea cucumber Stichopus regalis, areI-VFS representative species (Appendix).

scriminant)

I-VFS group AvSim(%)=54.0

Species Av.W Sim(%)

T. communis 28.71 14.9A. laterna 1.21 10.7M. variegates 0.31 8.2A. irregularis 0.29 5.6V. striatula 0.12 5.5

M-S group AvSim(%)=53.5

Species Av.W Sim(%)

A. laterna 0.81 9.7E. cirrhosa 0.80 9.0M. variegates 0.34 7.2L. boscii 0.32 7.0A. irregularis 0.15 5.8

O-FS group AvSim(%)=53.3

Species Av.W Sim(%)

G. argenteus 0.60 10.6L. boscii 0.63 10.6A. irregularis 0.09 7.0P. heterocarpus 0.67 5.9G. macrophthalmus 0.09 5.6

g/haul); Sim(%): percentage of similarity explained.

Table 3SIMPER results of otter trawl samples: species typifying groups (5 more discriminant)

I-M group AvSim(%)=51.4 I-VFS group AvSim(%)=58.8

Species Av.W Sim(%) Species Av.W Sim(%)

M. merluccius 3.67 10.2 M. merluccius 6.20 8.5E. cirrhosa 2.12 8.6 S. canicula 16.17 7.3A. laterna 1.18 8.4 M. variegates 1.03 5.9A. sphyraena 1.25 5.7 C. macropthalma 2.44 5.8I. coindetti 0.31 5.2 C. lucerna 1.66 5.6

I-FS group AvSim(%)=67.2 M-S group AvSim(%)=58.9

Species Av.W Sim(%) Species Av.W Sim(%)

P. acarne 11.43 6.02 M. merluccius 4.89 8.8C. lucerna 6.14 5.8 L. boscii 2.13 8.5M. merluccius 2.40 5.2 E. cirrhosa 2.57 7.7M. variegatus 1.66 5.2 M. variegatus 0.92 6.4C. lyra 3.53 5.1 H. dactylopterus 1.09 6.2

O-S group AvSim(%)=54.2

Species Av.W Sim(%)

L. boscii 3.03 11.1G. argenteus 5.30 9.6H. dactylopterus 2.07 8.2T. eblanae 0.54 7.1I. coindetti 1.13 6.9

AvSim(%): mean intergroup similarity; Av.W: mean biomass in the group (kg/haul); Sim(%): percentage of similarity explained.


Inner shelf fine sands (I-FS) are typified by drag-onet (Callyonimus lyra) and the hermit crab Pagurusbernhardus, in beam trawls (Table 2), and by P. acarne,gurnard (Chelidonichthys lucernus) and C. lyra in ottertrawls (Table 3). Several fish prefer this sandy hab-itat assemblage, such as boarfish (Capros aper), gur-nards (Aspitrigla cuculus, Chelidonichthys gurnardusand Chelidonichthys obscurus), sole (Solea solea), andpoutings (Trisopterus luscus and T. minutus). I-FS alsoseems to be a favourable habitat for large-sized gas-tropods (highest abundance of Argobuccinum olearium,Charonia lampax, Neptunea contraria, Appendix).

Middle shelf sand (M-S, grouping very fine and finesands) is typified by ubiquitous species in both samplingmethods (Tables 2 and 3). In addition, only a fewspecies present higher abundance in the M-S assem-blage (M. variegatus, Chlorotocus crassicornis, Ophiuraophiura, Hyalinoecia tubicola, Pennatula phosphorea).

Outer shelf very fine sands and fine sands werenot discriminated in otter trawl RDA, whereas in beamtrawl analysis slight differences were detected. For ottertrawls, O-S are characterised by L. boscii, silvery pout(Gadiculus argenteus), H. dactylopterus and the squidsTodaropsis eblanae and Ilex coindetti (Table 3). Speciesexplaining intragroup similarity in beam trawls are thesame in O-VFS and O-FS, these were: G. argenteus,

L. boscii, rockling (Gaidropsarus macrophthalmus),the shrimp Plesionika heterocarpus, and A. irregularis.Differences are due to intergroup dissimilarities (notshown), specifically to the higher abundance of thesquat lobster Munida sarsi in O-VFS and of Munidaintermedia in O-FS. In terms of biomass, some speciesare representative of the outer shelf sands: softheadgrenadier (Malacocephalus laevis), the three Munidaspecies (M. sarsi, M. intermedia, M. iris), the shrimpsP. heterocarpus and Philocheras echinulatus, and thecephalopods Octopus salutii, Rossia macrosoma andSepietta oweniana.

The faunal differentiation between assemblages is notso clear with respect to ecological indices (Fig. 6). Onlyin a few cases significant differences were detected:beam trawl M-S species richness was higher than inI-VFS and O-VFS (H=28.1, pb0.01; Fig. 6a), beamtrawl I-VFS diversity was lower than the rest of the groups(H=36.9; pb0.01; Fig. 6c), and otter trawl I-FS diversitywas higher than M-S (H=15.0; pb0.01; Fig. 6f). But themost outstanding differences occurred in beam trawlbiomass where I-VFS showed a higher value than theother assemblages (H=39.1, pb0.01), and I-M was alsohigher than the rest of assemblages (Fig. 6b).

The lower mean diversity value in I-VFS in the beamtrawl samples was not reflected in the otter trawls, which

Fig. 6. Species richness, biomass (tones/km2), and diversity in number of beam trawl (a, b, c) and otter trawl samples (e, f, g) in the assemblages. Bars:mean; whiskers: standard deviation. For assemblages abbreviations see Results.


is a consequence of the extremely high biomass sampledin I-VFS beam trawls. Higher abundance in I-VFS andI-M were due to the huge abundance of the gastropodT. communis (Appendix).

4. Discussion

The results strongly suggest that the spatial distribu-tion patterns of epibenthic communities are determinedby the combined effect of depth and sediment type.Linear relationships between each variable and the ecol-ogical indices are very weak, which shows that nosingle variable explains a high percentage of faunalvariability. As a consequence of the patchy distributionof epibenthic communities (López-Jamar et al., 1992;Serrano et al., 2006a) no linear relationships betweenenvironmental factors and indices were found and meth-ods which study the combined effects of all environ-mental variables must be used. Following this canonicalmethodology, 6 smaller epibenthic assemblages and 5bigger epibenthic and demersal assemblages were ob-tained in the 7 habitats described. Therefore, a com-bination of depth and sediment type may be consideredas a key factor in structuring communities, which isin agreement with the results published by other re-searchers (Poore andMobley, 1980; Basford et al., 1989;Olaso, 1990; Zendrera, 1990; Serrano et al., 2006a).

Between-habitat differences are clearer in the in-ner shelf of both samplers, and there are different epi-benthic assemblages in mud, very fine sand and finesand. However, the middle shelf is inhabited by a singleassemblage, independently of sediment type. Outer shelfvery fine sands and fine sands presented differentsmaller epibenthos assemblages, but a homogeneouscommunity of bigger and swimming fauna. These re-sults agree which those from Sánchez and Serrano(2003) in demersal communities and Serrano et al.(2006a) in epibenthic communities. These two studiesfocused on the Cantabrian shelf, described higher var-iability in the inner and outer shelf, while middle shelfhabitats were more homogeneous.

Inner and outer shelf assemblages are characterisedby eurytopic species together with stenotopic species(coastal or deep water species). However, the middleshelf is typified only by eurytopic species, which alsocharacterise other depth strata. In other words, the mid-dle shelf is inhabited by the characteristic continentalshelf community, typified by widely distributed specieswhich also inhabit inner and outer shelf (Sánchez andSerrano, 2003; Serrano et al., 2006a). Ecotonal effectoccurs in the extremes of the bathymetric gradientwhere, together with the shelf species, coastal and es-tuarine species (inner) and shelf break and slope species(outer) also dwell. The main sources of variability occur


mainly in the inner shelf (estuarine influence, seasonalupwelling, coastal rocky outcrops: López-Jamar et al.,1992) and in the outer shelf (shelf break, Polewardcurrent: Frouin et al., 1990; Álvarez-Salgado et al.,2003).

The ecology of these typifying species shows thatmost of them are species with a broad tolerance toground conditions (Sánchez and Serrano, 2003; Serranoet al., 2006a). These ubiquitous species are mainlymegafaunal, sampled more efficiently with otter trawl,and most of them are top predators in the benthic en-vironment (hake, monkfish, white octopus, etc). Smallersized epibenthos are mainly stenotopic species, relatedmore to one particular assemblage. This is a conse-quence of differential food requirements, since demersalcommunities are controlled by prey distribution andsmaller sized epibenthos, mainly deposit-feeders, byorganic contents in the sediments. This fact explains themore important role of sediment characteristic in beamtrawls with respect to otter trawls.

Habitats covered by low-size particle sediments withhigh organic content are mainly characterised by smallepibenthic deposit-feeders and suspension-feeders:inner shelf mud assemblage is known as the Sternas-pis community, as this polychaete is the typifying spe-cies (López-Jamar et al., 1992), accompanied by otherorganic-enriched mud characteristic species, such as thecrustacean A. glaber (Lagardère, 1973; Olaso, 1990),whereas inner shelf very fine sands are inhabited bythe suspension-feeder Turritella communis (Fretterand Graham, 1981). Those environments are also pre-ferred habitats of scavenger hermit crabs, (Serrano et al.,2006a), which use Turritella shells as shelter. In con-trast, fine sand habitats show a lower presence of small-sized epibenthos, as a consequence of the low organiccontent compared to mud or very fine sands (Serranoet al., 2006a). López-Jamar et al. (1992) described ahigher proportion of deposit-feeders and a highersuccessional stage in the endobenthic communitiesdwelling the enriched mud and very fine sands depositsoff Rías Baixas than those inhabiting sandy sediments ofthe northern and western shelf.

Differences between assemblages are due to speciescomposition and abundance, since no differences havebeen detected with respect to ecological indices. Strongfishing pressure acting over the entire Galician shelfhas probably caused a progressive decrease in indicesin the last decades (Rice, 2000), which probably masksthe former optimal natural conditions. Nevertheless,using yearly IEO autumn demersal surveys, with ahigher number of samples, some spatial patterns couldbe extracted. The highest richness of fish in the inner

shelf is probably related to the higher environmentalheterogeneity (Kaiser et al., 1999) and the lower fisheryimpact (trawling is forbidden on less of 100 m depth).In addition, the high pelagic productivity linked withcoastal outwelling and upwelling (Tenore et al., 1984;López-Jamar et al., 1992) produce higher food avail-ability for juveniles of several species (Sánchez, 1993;Sánchez et al., 2002). However, fish diversity on theinner and middle shelf is lower than on the outer shelf.This fact is a consequence of the massive abundance oflarge schools of plankton feeder fishes and juveniles(mainly horse mackerel, sparids and hake) on the shelf;whereas the outer shelf and shelf break is inhabited byk-strategist with low reproduction and growth rates(deep water sharks, macrourids, etc). When invertebrateand fish species are considered together their distri-bution seems to be controlled by factors other thandepth (e.g. nutrients, substrate type). In this case, spe-cies richness is higher on the northern coast (Estaca deBares cape), which is described as a biogeographic limit(boundary effect) and a retention area of hydrographicanomalies (Sánchez and Gil, 2000). These anomalies(eddies) have been related to processes of water columnproduction and enrichment of the shelf sedimentaryregime (López-Jamar et al., 1992), and in the northernGalician area, to hake recruitment (Sánchez and Gil,2000).

In conclusion, the main environmental factorexplaining the spatial distribution patterns of Galicianshelf benthic communities, both epibenthic and demer-sal, is the combination of depth and sediment type overseasonal or spatial variables. Depth-sedimentary deter-mination of spatial distribution ordination shows thatthere are six assemblages with differential speciescomposition. Knowledge about these habitats will bevery useful for monitoring anthropogenic perturbationsin the Galician area, such as oil spills or fishing impacts.

Acknowledgements

This study was made possible thanks to the in-valuable work of all the participants in the Prestigesurveys and the crews of the two research vessels Cor-nide de Saavedra and Vizconde de Eza. Sedimentarystudies were carried out by the Benthos Team of theI.E.O (Coruña), specifically by Joaquin Valencia andElena Rey. We are grateful to Drs Joan Cartes andEmanuella Fanelli from the I.C.M. (CSIC, Barcelona) fortheir fruitful collaboration. This study was partiallysupported by the Urgent and Strategic Actions of theSpanish Science and Technology Ministry, and includedin the ECOPREST Project (VEM2003-20081-CO2).


Appendix

Annex 1— Mean biomass of species used in the multivariate analysis by assemblage. Abbreviations used in Fig. 5appear in brackets after the species name

I-M
I-VFS I-FS M-S
(

O-FS

continued on nex

O-VFS

Fish
Argentina sphyraena (Asph) 22.85 32.96 65.16 17.81 2.39 4.20 Arnoglossus laterna (Alat) 339.50 367.46 195.20 239.63 11.30 7.56 Aspitrigla cuculus (Acuc) 3.86 16.66 49.74 1.80 0.15 Blennius ocellaris (Boce) 1.32 0.87 2.72 5.12 0.87 0.47 Buglossidium luteum (Blut) 6.20 21.29 Callionymus lyra (Clyr) 2.36 30.33 230.90 4.02 Callionymus maculatus (Cmac) 25.18 17.65 1.82 22.08 2.52 2.94 Capros aper (Cape) 5.79 23.60 47.06 11.71 0.90 1.78 Cepola macrophthalma (Cema) 4.93 44.54 0.61 1.36 Chelidonichthys lucernus (Cluc) 5.82 30.29 112.18 2.30 Chelidonichthys obscurus (Cobs) 2.87 5.35 47.37 1.92 Conger conger (Ccon) 21.50 7.93 8.14 5.21 35.25 Eutrigla gurnardus (Egur) 14.39 58.47 89.56 67.24 16.51 15.26 Gadiculus argenteus (Garg) 66.46 6.03 0.90 138.41 191.62 181.76 Gaidropsarus macrophthalmus (Gmac) 15.48 4.53 0.42 28.70 44.06 26.24 Helicolenus dactylopterus (Hdac) 1.44 1.48 2.83 19.97 36.78 39.01 Lepidorhombus boscii (Lbos) 6.00 6.16 70.24 97.89 114.15 190.10 Lepidorhombus whiffiagonis (Lwhi) 1.17 0.84 2.44 Lepidotrigla cavillone (Lcav) 7.65 2.62 0.16 0.02 Lesueurigobius friesii (Lfri) 1.54 0.09 2.04 0.00 Lophius budegassa (Lbud) 4.08 12.24 1.27 39.37 54.41 104.45 Lophius piscatorius (Lpis) 8.24 19.35 89.64 33.03 131.80 34.41 Macroramphosus scolopax (Msco) 0.01 0.19 0.25 Malacocephalus laevis (Mlae) 2.03 5.44 Maurolicus muelleri (Mmue) 0.09 0.04 0.04 Merluccius merluccius (Mmer) 67.04 113.30 43.81 89.38 18.19 16.22 Microchirus variegatus (Mvar) 39.47 93.64 30.33 106.22 5.71 18.55 Molva macrophthalma (Mmac) 0.01 3.13 2.08 Mullus surmuletus (Msur) 0.23 0.95 2.62 1.21 1.96 1.70 Pagellus acarne (Paca) 376.20 208.81 1.19 Pagellus bogaraveo (Pbog) 1.55 0.97 0.06 0.70 Petromyzon marinus (Pmar) 0.11 0.31 0.20 Phycis blennoides (Pble) 0.68 1.01 6.62 4.76 Pomatoschistus microps (Pmic) 0.21 1.56 0.15 0.40 Pomatoschistus sp. (Psp1) 2.75 5.42 0.89 7.33 0.24 0.43 Pomatoschistus sp2 (Psp2) 1.33 0.08 0.40 0.04 Raja clavata (Rcla) 6.14 135.36 69.46 3.42 Raja montagui (Rmon) 0.14 35.28 2.02 Scyliorhinus canicula (Scan) 116.05 295.44 566.99 17.19 2.53 3.79 Solea solea (Ssol) 4.65 55.25 91.64 0.30 Spondyliosoma cantharus (Spca) 38.02 31.17 Trigla lyra (Tlyr) 0.22 0.06 0.23 Trisopterus luscus (Tlus) 23.84 121.97 200.68 29.79 6.03 9.56 Trisopterus minutus (Tmin) 15.95 32.22 70.15 0.08 Zeus faber (Zfab) 22.90 51.26 37.73 5.01 0.13
Crustaceans
Alpheus glaber (Agla) 52.10 3.00 3.05 3.90 1.68 Anapagurus laevis (Alae) 1.15 30.95 5.72 0.11 0.04 0.39 Anapagurus petiti (Apet) 0.07 8.53 0.06 0.00 Chlorotocus crassicornis (Ccra) 7.41 0.74 0.02 14.58 5.13 5.67 Dichelopandalus bonnieri (Dbon) 0.64 1.65 Ebalia cranchii (Ecra) 0.08 1.40 0.02 0.17 0.01 0.03
t page)


Appendix (continued )

I-M
I-VFS I-FS M-S O-FS O-VFS
CrustaceansEbalia granulosa (Egra)
0.29 0.06 0.02 0.02 Eurynome aspera (Easp) 0.03 0.28 0.05 Galathea dispersa (Gdis) 0.14 0.07 0.32 0.07 0.03 Galathea strigosa (Gstr) 0.20 0.86 0.20 0.00 Goneplax rhomboides (Grho) 20.31 5.00 0.05 1.19 4.60 1.61 Liocarcinus depurator (Ldep) 105.73 9.96 0.71 2.22 0.68 16.87 Lophogaster typicus (Ltyp) 0.09 0.11 0.29 0.61 0.67 Macropipus tuberculatus (Mtub) 0.07 0.07 1.96 13.76 Macropodia longipes (Mlon) 0.24 0.50 0.20 1.11 0.67 4.60 Munida intermedia (Mint) 0.10 0.04 1.45 0.14 78.45 2.87 Munida iris (Miri) 0.03 0.83 1.03 Munida sarsi (Msar) 0.15 0.02 2.70 50.55 309.10 Nephrops norvegicus (Nnor) 3.33 2.34 0.43 2.53 0.97 Pagurus alatus (Pala) 0.20 0.13 0.05 0.24 0.27 0.07 Pagurus bernhardus (Pber) 1.79 1.24 9.14 0.04 Pagurus excavatus (Pexc) 2.07 13.75 1.26 5.78 0.88 0.46 Pagurus prideaux (Ppri) 11.08 53.56 10.13 4.64 0.07 0.00 Pasiphaea sivado (Psiv) 0.16 0.97 Philocheras echinulatus (Pech) 0.10 0.01 0.11 2.96 5.54 Plesionika heterocarpus (Phet) 15.69 0.02 16.89 204.31 202.69 Pontophilus norvegicus (Pnor) 0.27 0.28 0.20 0.05 Pontophilus spinosus (Pspi) 11.56 5.96 0.05 6.85 11.57 17.24 Processa sp. (Prsp) 7.21 1.46 0.15 3.72 6.06 6.09 Rissoides desmaresti (Rdes) 0.21 0.14 0.56 0.55 Scalpellum scalpellum (Ssca) 0.48 1.36 8.02 0.04 0.07 Solenocera membranacea (Smem) 8.95 3.41 0.09 9.70 7.90 10.90
Molluscs
Aporrhais pespelicani (Apes) 0.08 240.57 3.99 4.37 3.27 6.29 Aporrhais serresianus (Aser) 76.60 4.77 16.98 19.69 Argobuccinum olearium (Aole) 4.15 16.25 4.94 2.41 1.94 Buccinum humphreysianum (Bhum) 1.81 0.14 1.12 0.70 Calliostoma granulatum (Cgra) 0.04 7.08 4.08 7.62 0.09 1.66 Charonia lampax (Clam) 0.58 10.12 0.05 Colus gracilis (Cgrc) 0.56 1.97 0.02 1.20 Comarmondia gracilis (Cgrl) 0.05 0.01 0.04 0.03 Cuspidaria cuspidata (Ccus) 0.01 0.15 0.03 1.25 0.22 0.20 Cuspidaria rostrata (Cros) 0.04 0.04 0.01 Eledone cirrhosa (Ecir) 200.93 123.04 48.00 247.27 218.67 105.43 Epitonium clathrus (Ecla) 2.62 5.22 0.03 0.01 Galeodea rugosa (Grug) 0.26 1.96 4.08 8.16 8.85 Gasteropteron meckeli (Gmec) 0.03 1.81 0.80 0.03 1.34 Hinia reticulata (Hret) 28.86 0.03 15.96 0.00 0.17 Illex coindetii (Icoi) 5.76 5.37 5.87 11.39 13.18 28.74 Lunatia fusca (Lfus) 1.12 0.07 0.78 2.19 6.92 4.96 Nassarius ovoideus (Novo) 41.29 25.03 0.01 5.68 5.24 2.13 Neptunea contraria (Ncon) 44.02 9.36 204.43 48.03 33.80 6.90 Nucula sulcata (Nsul) 0.90 0.10 0.14 0.49 0.07 Octopus salutii (Osal) 0.56 0.73 5.93 0.91 Octopus vulgaris (Ovul) 13.38 28.71 38.20 2.42 0.18 1.92 Rondeletiola minor (Rmin) 3.36 1.91 0.47 3.37 5.97 4.67 Rossia macrosoma (Rmac) 0.03 5.04 16.90 12.98 Roxania utricolis (Rutr) 0.14 0.00 Scaphander lignarius (Slig) 0.01 9.39 13.98 0.20 6.20 Sepia elegans (Sele) 1.24 5.72 1.47 2.28 0.05 0.04 Sepia orbignyana (Sorb) 1.03 3.68 9.37 4.46 0.32 0.20 Sepietta oweniana (Sowe) 0.32 0.12 0.06 0.76 8.62 7.54 Sepiola sp. (Sesp) 3.72 1.73 0.23 2.82 0.63 0.92 Tellina fabula (Tfab) 0.47 0.19 0.02


Appendix (continued )

I-M
I-VFS I-FS M-S O-FS O-VFS
MolluscsTimoclea ovata (Tova)
1.54 0.05 0.04 Todarodes sagittatus (Tsag) 2.88 3.31 2.93 Todaropsis eblanae (Tebl) 4.68 7.28 7.82 8.14 8.51 11.23 Turritela communis (Tcom) 2157.44 8682.33 2.27 2.81 0.36 Venus striatula (Vstri) 10.93 36.08 0.20 0.00
Echinoderms
Astropecten irregularis (Airr) 15.49 86.94 113.23 44.04 15.69 26.85 Brissopsis lyrifera (Blyr) 2.67 0.59 0.04 Echinocardium cordatum (Ecor) 1.35 1.64 0.14 Leptometra celtica (Lcel) 0.04 0.04 0.11 Marthasterias glacialis (Mgla) 15.36 7.80 8.35 12.50 Ophiothrix fragilis (Ofra) 0.02 0.08 0.14 0.01 Ophiura affinis (Oaff) 0.34 0.04 0.41 1.08 5.20 Ophiura albida (Oalb) 0.26 0.00 2.67 Ophiura ophiura (Ooph) 0.14 6.15 5.04 54.90 9.33 24.25 Stichopus regalis (Sreg) 120.72 221.55 31.99 32.94 0.28 0.14 Trachythyone tergestina (Tter) 0.02 0.25 3.50
Annelids
Aphrodita aculeata (Aacu) 0.12 1.12 2.03 1.17 0.07 Chloeia venusta (Cven) 0.41 0.34 Hyalinoecia tubicola (Htub) 0.12 0.01 0.21 4.51 0.01 Laetmonice filicornis (Lfil) 0.01 0.05 0.16 Sternaspsis scutata (Sscu) 153.22 9.20 5.10
Cnidarians
Actinauge richardi (Aric) 4.59 3.35 4.30 Cerianthus lloydi (Cllo) 0.09 0.29 0.50 Lytocarpia myriophyllum (Lmyr) 0.02 3.07 2.63 0.05 0.02 Pennatula phosphorea (Ppho) 0.11 0.11 3.05 47.58 0.11 0.10
Tunicates
Corella paralelograma (Cpar) 0.06 1.88
References

Álvarez-Salgado, X.A., Beloso, S., Joint, I., Nogueira, E., Chou, L.,Pérez, F.F., Groom, S., Cabanas, J.M., Rees, A.P., Elskens, M.,2002. New production of the NW Iberian shelf during theupwelling season over the period 1982–1999. Deep-Sea Res., I 49,1725–1739.

Álvarez-Salgado, X.A., Figueiras, F.G., Pérez, F.F., Groom, S.,Nogueira, E., Borges, A.V., Chou, L., Castro, C.G., Moncoiffé,G., Ríos, A.F., Miller, A.E.J., Frankignoulle, M., Savidge, G.,Wollast, R., 2003. The Portugal coastal counter current off NWSpain: new insights on its biogeochemical variability. Prog.Oceanogr. 56, 281–321.

Arístegui, J., Álvarez-Salgado, X.A., Barton, E.D., Figueiras, F.G.,Hernández-León, S., Roy, C., Santos, A.M.P., 2006. Oceano-graphy and fisheries of the Canary Current/Iberian region of theeastern North Atlantic. In: Robinson, A.R., Brink, K.H. (Eds.),The Sea, vol. 14b. Harvard University Press, Cambridge, MA,pp. 877–931.

Basford, D.J., Eleftheriou, A., Rafaelli, D., 1989. The epifauna of theNorthern North Sea (56°–61°N). J. Mar. Biol. Assoc. U.K. 69,387–407.

Buchanan, J.B., 1984. Sediment analysis. In: Holme, A.D., McIntyre(Eds.), Methods for the Study of Marine Benthos. BlackwellScientific Publications, Oxford, pp. 41–65.

Clarke, K.R., Warwick, R.M., 1994. Change in marine communities:an approach to statistical analysis and interpretation. PlymouthMarine Laboratory, 144 pp.

Fariña, A.C., Pereiro, F.J., 1995. Distribution and abundance ofmolluscs and decapod crustaceans in trawl samples from theGalician shelf. ICES Mar. Sci. Symp. 199, 189–199.

Fretter, V., Graham, A., 1981. The Prosobranch molluscs of Britainand Denmark. Part 6—Neogastropoda. J. Molluscan Stud. Suppl.15, 435–556.

Frouin, R., Fiúza, A.F.G., Ámbar, I., Boyd, T.J., 1990. Observations ofa poleward current off the coasts of Portugal and Spain duringwinter. J. Geophys. Res. 95, 679–691.

Guisande, C., Cabanas, J.M., Vergara, A.R., Riveiro, I., 2001. Effect ofclimate on recruitment success of Atlantic Iberian sardine Sardinapilchardus. Mar. Ecol., Prog. Ser. 223, 243–250.

Joint, I., Groom, S.B., Wollast, R., Chou, L., Tilstone, G.H.,Figueiras, F.G., Loijens, M., Smyth, T.J., 2002. The responseof phytoplankton production to periodic upwelling andrelaxation events at the Iberian shelf break: estimates by the14C method and by satellite remote sensing. J. Mar. Syst. 32,219–238.

Kaiser, M.J., Rogers, S., Ellis, J.R., 1999. Importance of benthichabitat complexity for demersal fish assemblages. Am. Fish. Soc.Symp. 22, 212–223.

Lagardère, J.P., 1973. Distribution des décapodes dans le sud du Golfede Gascogne. Rev. Trav. Inst. Pêches Marit. 37, 77–95.


López-Jamar, E., González, G., 1987. Infaunal macrobenthos of theGalician continental shelf off La Coruña bay, Northwest Spain.Biol. Oceanogr. 4, 165–192.

López-Jamar, E., Cal, R.M., González, G., Hanson, R.B., Rey, J.,Santiago, G., Tenore, K.R., 1992. Upwelling and outwellingeffects on the benthic regime of the continental shelf off Galicia,NW Spain. J. Mar. Res. 50, 465–488.

Olaso, I., 1990. Distribución y abundancia del megabentos inverteb-rado en fondos de la plataforma cantábrica. Publ. Espec. Inst. Esp.Oceanogr. 5 128 pp.

Poore, G.C.B., Mobley, M.C., 1980. Canonical correlation of marinemacrobenthos survey data. J. Exp. Mar. Biol. Ecol. 45, 37–50.

Rey, J.J., Medialdea, T., 1989. Los sedimentos cuaternarios superficialesdel margen continental español. Publ. Esp. Ins. Esp. Oceanogr. 3,1–29.

Rice, J.C., 2000. Evaluating fishery impacts using metrics ofcommunity structure. ICES J. Mar. Sci. 57, 682–688.

Sánchez, F., 1993. Las comunidades de peces de la plataforma delCantábrico. Publ. Espec. Inst. Esp. Oceanogr. 13, 137 pp.

Sánchez, F., Gil, J., 2000. Hydrographic mesoscale structures andPoleward Current as a determinant of hake (Merluccius merluc-cius) recruitment in southern Bay of Biscay. ICES J. Mar. Sci. 57,152–170.

Sánchez, F., Serrano, A., 2003. Variability of groundfish communitiesof the Cantabrian Sea during the 1990s. ICESMar. Sci. Symp. 219,249–260.

Sánchez, F., Blanco, M., Gancedo, R., 2002. Atlas de los pecesdemersales y de los invertebrados de interés comercial de Galicia yel Cantábrico. Otoño 1997–1999. Ed. CYAN (Inst. Esp. Ocea-nogr.), 159 pp.

Sánchez, F., Velasco, F., Cartes, J.E., Olaso, I., Preciado, I., Fanelli, E.,Serrano, A., Zabala, J.L., 2006. Monitoring the Prestige oil spillimpacts on some key species of the Northern Iberian Shelf. Mar.Pollut. Bull. 53, 332–349.

Serrano, A., Sánchez, F., García-Castrillo, G., 2006a. Epibenthiccommunities of trawlable grounds of the Cantabrian Sea. Sci. Mar.70, 149–159.

Serrano, A., Sánchez, F., Preciado, I., Parra, S., Frutos, I., 2006b.Spatial and temporal changes in benthic communities of theGalician continental shelf after the Prestige oil spill. Mar. Pollut.Bull. 53, 315–331.

Tenore, K.R., Cal, R.M., Hanson, R.B., López-Jamar, E., Santiago, G.,Tietjen, J.H., 1984. Coastal upwelling off the Rías Bajas, Galicia,Northwest Spain. II. Benthic studies. Rapp. P.-v. Réun. Cons. Int.Explor. Mer. 183, 91–100.

Tenore, K.R., Alonso-Noval, M., Álvarez-Ossorio, M.T., Atkinson, L.P.,Cabanas, J.M., Cal, R.M., Campos,M.J., Castillejo, F., Chesney, E.J.,González, N., Hanson, R.B., McClain, C.R., Miranda, A., Román,M.R., Sánchez, J., Santiago, G., Valdés, L., Varela, M., Yoder, J.,1995. Fisheries and oceanography off Galicia, NW Spain:mesoscale spatial and temporal changes in physical processes andresultant patterns of biological productivity. J. Geophys. Res. 100,10943–10966.

Van Weering, T.C.E., McCave, I.N., 2002. Benthic processes anddynamics at theNWIberianmargin: an introduction. Prog.Oceanogr.52, 123–128.

Zendrera, N., 1990. Typologie du golfe de Gascogne á partir del'analyse des associations faunistiques. PhD. Océanologie Biolo-gique: Ecosystems marins. Option paramétrisation et modélisation.Univ. Pierre et Marie Curie (Paris VI).

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Spatial distribution patterns of demersal and epibenthic communities on the Galician continental shelf (NW Spain)