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Marine Environmental Research 71 (2011) 97e110

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Marine Environmental Research

journal homepage: www.elsevier .com/locate/marenvrev

Factors structuring temporal and spatial dynamics of macrobenthic communitiesin a eutrophic coastal lagoon (Óbidos lagoon, Portugal)

Susana Carvalho a,*, Patrícia Pereira b, Fábio Pereira a, Hilda de Pablo b, Carlos Vale b, Miguel B. Gaspar a

a Instituto Nacional de Recursos Biológicos (INRB/IPIMAR), Av. 5 de Outubro, 8700-305 Olhão, Portugalb Instituto Nacional de Recursos Biológicos (INRB/IPIMAR), Av. Brasília, 1449-006 Lisboa, Portugal

a r t i c l e i n f o

Article history:Received 30 July 2010Received in revised form17 November 2010Accepted 18 November 2010

Keywords:Coastal lagoonsSpatial and temporal variabilityMacrobenthosSediment and water propertiesEutrophicationFeeding guilds

* Corresponding author. Tel.: þ351 289 700500; faxE-mail address: scarvalho@ipimar.pt (S. Carvalho).

0141-1136/$ e see front matter � 2010 Elsevier Ltd. Adoi:10.1016/j.marenvres.2010.11.005

a b s t r a c t

The present work aimed to identify the main environmental drivers shaping temporal and spatialdynamics of macrobenthic communities within a eutrophic coastal lagoon. Sediments in the Óbidoslagoon showed a gradient of increasing metal contamination from the inlet area to inner branches. Themid-lower lagoon area exhibited an intermediate contaminated condition between the inlet andupstream areas, suggesting that the effects of the organic loadings into the lagoon may be reflected untilthis area. This transitional feature was corroborated by biological data, with macrobenthic assemblagesdisplaying characteristics of down- and upstream areas. Macrobenthic abundance peaked in winter,which was associated with a higher nutrient availability (mainly ammonium) and the proliferation ofgreen macroalgae in mid-lower and inner lagoon areas. However, massive macroalgae growth resulted ina sharp decrease of macrobenthic diversity and abundance in spring, particularly where the higheramounts of decaying algae were detected. Higher dissimilarities between assemblages were detectedduring winter (and spring, for trophic composition), while in summer, differences were highly attenu-ated. The least contaminated area (close to the sea inlet) experienced smaller temporal variations forenvironmental variables, as well as the lowest temporal biological variability. This area was dominated bycarnivores, which were related with increased salinity. Deposit-feeders were numerically dominant inthe lagoon, being generally spread within organically enriched sandy and muddy areas. The highconcentration of chlorophyll a and suspended particulate matter in water was reflected in the abundanceof deposit-feeders/suspension-feeders, taking benefit of the high primary productivity. On the otherhand, deposit-feeders/herbivores responded to the decay of macroalgae mats in the sediment. Biologicalassociations varied with the biological data used (taxonomic versus trophic group composition; abun-dance versus biomass), highlighting the relevance of the combination of different data analysis’approaches. In general, BIOENV analysis indicated total phosphorus, biomass of Ulva, metals and organiccarbon and nitrogen as being significantly influencing benthic patterns. On the other hand, discrepanciesin ecological behaviours of some taxa were also detected in the present study stressing the need foradditional studies on the relationships between macrobenthic communities and environmental vari-ables. Implications of the present results for monitoring studies are discussed.

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1. Introduction

Coastal lagoons are often characterized by generally restrictedwater exchange with the open sea and shallow depths (UNESCO,1981), reducing dilution processes and enhancing sedimentretention of contaminants (Pérez-Ruzafa et al., 2005). Their asso-ciation with the adjacent draining basin makes such systemsvulnerable to eutrophication, leading to lowwater oxygenation andthe production of toxic hydrogen sulphide (UNESCO,1981). In some

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cases, anoxic conditions can even occur in the sediment during thenight favouring the release of metals and nutrients from the sedi-ment to the overlying water (Point et al., 2007; Pereira et al.,2009a). Thus, coastal lagoons may experience an additionalproblem of metal contamination, with potential repercussions inthe biota.

Macrobenthos is a key component of coastal ecosystems(including lagoons), playing a vital role in detritus decomposition,nutrient cycling and energy flow to higher trophic levels (Maseroet al., 1999; Heilskov and Holmer, 2001; Mermillod-Blondin et al.,2005; Carvalho et al., 2007). This faunal component has beenfrequently used in environmental quality assessment of coastal

Fig. 1. Location of sampling sites in the Óbidos lagoon.

S. Carvalho et al. / Marine Environmental Research 71 (2011) 97e11098

systems (e.g. Ponti and Abbiati, 2004; Carvalho et al., 2006b, 2010;Munari and Mistri, 2008). Nevertheless, it is often difficult todiscriminate between natural and human-induced changes basedon macrobenthic communities (Elliott and Quintino, 2007). Theheterogeneous distribution of benthic organisms in marine softsediments and sediment-related variables (e.g. contaminants,sediment particle-size, organic matter content) has been frequentlyreported (Luoma and Phillips, 1988; Koutsoubas et al., 2000;Ysebaert and Herman, 2002; Blanchet et al., 2005). The spatialand temporal distributions have been related either to physical (e.g.water depth, water temperature, hydrodynamics, sediment grainsize) or biological factors (life cycle, larval settlement dynamics,microbial activity, bioturbation, competition, predation) or inter-actions between them (Snelgrove and Butman, 1994; Mancinelliet al., 1998; Ysebaert and Herman, 2002; Blanchet et al., 2005;Como and Magni, 2009).

Some of the characteristics of coastal lagoons (e.g. shallow depthand limited water exchange) result in considerable daily andseasonal changes in environmental variables (e.g. temperature)with consequences for the benthic assemblages (Como and Magni,2009). These fluctuations can have repercussions on physico-chemical processes in sediments (e.g. Lillebø et al., 2004; Muchaet al., 2004; Point et al., 2007) and act as a driving force in thedynamics of the marine benthic environment, affecting species’ lifecycles (Marques et al., 1994). Therefore, besides spatial variability,knowledge on the temporal changes in macrobenthic communitiesfrom coastal lagoons can be highly relevant namely for the estab-lishment of monitoring programmes.

The Óbidos lagoon (western Portugal) is moderately contami-nated by metals and has experienced high nutrient loads ofanthropogenic origin (particularly nitrogen and phosphorus)leading to signs of eutrophication (Pereira et al., 2009a,b). In coastallagoons, this is a common environmental problem that can result incommunity dominance changes, as well as alterations in speciescomposition (Dolbeth et al., 2003; Pranovi et al., 2008). This systemhas been studied in terms of the relationship between macro-benthic communities and several sediment parameters during thewinter season (Carvalho et al., 2005, 2006b), and more recentlyregarding water quality (Pereira et al., 2009a,b). Concerning mac-robenthic communities it was observed that some taxa such asCapitella spp., usually associated with organic enrichment (Pearsonand Rosenberg, 1978), increased their abundance seawards, whereno major allochtonous sources of organic enrichment are present(unpublished data). This change appeared to occur simultaneouslywith a generalised increase of Ulva spp., particularly within themiddle area.

The present study testswhether benthic communities, sedimentproperties, water quality, and their relationships change along oneyear, in five sites located at upper (2 sites), middle (2 sites) andlower (1 site) parts of the Óbidos coastal lagoon, an ecosystemwithpronounced spatial variation of macrobenthic communities, waterquality and sediment properties. In order to better clarify thecomplex link between abiotic and biotic interactions, multivariateanalysis approaches were used both for taxon and for the trophicgroups’ composition, using abundance and biomass data.

2. Material and methods

2.1. Study area

The Óbidos lagoon is a shallow coastal ecosystem, located onthe west coast of Portugal with a wet area of 7 km2, permanentlyconnected to the sea through a narrow inlet (Fig. 1). The lagoonis characterized by semi-diurnal tides (tidal range 0.5e4.0 mdepending upon location and tidal phase) (Malhadas et al., 2009).

It comprises areas of different morphological and sedimentarycharacteristics: sandbanks andnarrowchannels in the lower/middlelagoon; muddy sediments in the two inner branches (Barrosa andBom-Sucesso). The Barrosa branch is a shallow area (mean depth0.5e1 m) and water circulation is mostly driven by tides and bya small tributary (Cal River) that drains agriculture fields. Urbaneffluents from a nearby town (Caldas da Rainha, 50,000 inhabitants)had been discharged to the Barrosa branch by the Cal River. Conse-quently, this area presents the highest nutrient availability of thelagoon, beingpreviously classifiedas eutrophic (Pereira et al., 2009b).Highnutrient concentrationswere in linewith abundantmacroalgae(Ulva spp.) and a broad daily variation of dissolved oxygen concen-tration during the summer months (Pereira et al., 2009a). The Bom-Sucesso branch (mean depth 2e3 m) is also a confined area butreceives a smaller freshwaterflow (Vala do Ameal) with betterwaterquality than theCal River, according to the Portuguese categorizationof freshwater systems. Lower and middle lagoon areas show a highwater renewal leading to the improvement of water quality incomparison with the other areas (Pereira et al., 2009a).

2.2. Sampling

Sampling was performed in January (winter), May (spring), July(summer) and October (fall) 2006 in five sites (Fig. 1): site 1, locatedin the inlet; sites 2 and 3 located in the central area of the lagoon(site 2 in the mid-lower area; site 3 in the mid-upper area); sites 4and 5 in the two inner branches, Barrosa and Bom-Sucesso,respectively. In order to facilitate the reading of this work, sampleswill be designated by the combination of the site and the season, ina way that the first character is related to the season (winter, W;spring, Sp; summer, S; fall, F) and the latterwith the site (1, 2, 3, 4, 5).The selection of these sites was based on previous works under-taken in this lagoon both considering benthic communities andenvironmental parameters (Carvalho et al., 2005, 2006b; Pereiraet al., 2009b). Those studies pointed at the existence of 3 biologi-cally and environmentally distinct areas in the lagoon. Surfacewater (0.2 m depth) was sampled for measurements of nutrientsand chlorophyll a. Sediment samples were collected with a Van-Veen grab (0.05 m2) for the study of benthic communities. At eachsampling period and site, three replicates were randomly collected.Sub-samples were also separated for chemical analyses.

S. Carvalho et al. / Marine Environmental Research 71 (2011) 97e110 99

2.3. Analytical procedures

2.3.1. Water and sediment physico-chemical parametersWater temperature, salinity and dissolved oxygen were

measured in situ using an YSI, 650 m. Suspended particulate matter(SPM) was obtained by filtering 250 mL of water through celluloseacetate membranes (0.45 mm) and determined gravimetrically(drying at 70 �C) in triplicates. Water samples for determinations ofammonium ðNHþ

4 Þ, nitrate ðNO�3 Þ, nitrite ðNO�

2 Þ and phosphateðPO3�

4 Þ were filtered through MSI Acetate Plus filters, and analyses(performed in triplicates) carried out using an autoanalyser TRAACS2000 (Bran þ Luebbe). The precision was found to be �1.0% fornitrite þ nitrate, �2.0% for ammonium and �1.9% for phosphate.For chlorophyll a determinations, water was filtered througha Whatman GF/F filter (0.7 mm) that was immediately frozen at�20 �C and later extracted in 90% acetone, for analysis in a PerkinElmer Fluorometer using the protocol modified by Lorenzen (1966).Organic carbon (Corg) and organic nitrogen contents (Norg) insediments were determined in oven-dried (to constant weight at40 �C) and homogenised sediment sub-samples, according toVerardo et al. (1990) in a CHN Fisons NA1500 Analyser. Totalphosphorus in sediments (P) was determined by Andersen (1976)method using a spectrophotometer Spectronic Genesys 5.

2.3.2. Metal determinations in sedimentSediment samples (100 mg) were completely mineralized with

HF (40%) and Aqua Regia (HCl-36%: HNO3-60%; 3:1) in closed Teflonbombs (100 �C for 1 h), evaporated to near dryness (DigiPrepHotBlocke SCP Science), redissolvedwith 1mL of doubled-distilledHNO3 and 5 mL of ultra-pure water, heated for 20 min at 75 �C, anddiluted to 50 mL with ultra-pure water (Caetano et al., 2007). Theconcentrations of Cr, Cu, Ni, Pb and Cd were determined byinductively coupled plasmamass spectrometery, whereas Al and Fewere determined by atomic absorption spectrometry. In order toexamine for any possible contamination during the analyticalprocedure blanks were analysed. Metal levels obtained in thereference materials were consistently within the ranges of certifiedvalues. In order to avoid contamination, all labware for metaldeterminations was soaked for two days with HNO3 (20%), then fortwo days with HCl (20%) and rinsed with ultra-pure water.

2.3.3. Macrobenthic communitiesMacrofaunal samples were washed through a 0.5 mm square

mesh sieve, and the retained material was preserved in 4% bufferedformalin stained with Rose Bengal. In the laboratory, animals werehand sorted into major taxonomic groups, identified to the lowestpractical taxonomic level and counted. Biomass, expressed as ashfree dry weight (AFDW; �0.0001 g) was determined per taxon, siteand sampling period.

Macrobenthic taxa were assigned to a feeding guild based ontheir feeding habits: carnivores (including scavengers) (C), herbi-vores (H), deposit-feeders (DF), suspension feeders (SF) andomnivores (O). As some taxa are able to alternate their feedinghabits, we also considered deposit-feeders/suspension-feeders(DF/SF), deposit-feeders/herbivores (DF/H), deposit-feeders/carni-vores (DF/C), carnivores/suspension feeders (C/SF), and carnivores/herbivores (C/H). These feeding guilds were established based onthe following literature: Wägele et al., 1981; Gaston et al., 1998;Mancinelli et al., 1998; Roth and Wilson, 1998; Bachelet et al.,2000; Mistri et al., 2000; Antoniadou and Chintiroglou, 2006;Gaudêncio and Cabral, 2007; Afli et al., 2008; Dolbeth et al., 2009.An extremely low percentage of taxa (0.19% of total abundance;0.26% of total biomass) could not be accurately assigned to any ofthe previously indicated groups. Therefore, they were classified asunknown and not considered for the data analysis.

2.4. Data analysis

Differences on environmental parameters between sites andsampling periods were assessed by the KruskaleWallis (KeW) test(ANOVA on ranks), while post-hoc comparisons were performedthrough the Tukey test, using STATISTICA v6 software. Faunal datawas analysed for abundance, number of taxa, Shannon-Wiener(loge) diversity and biomass. Shannon-Wiener index was alsoapplied to estimate the feeding diversity in the Óbidos lagoon,following Gamito and Furtado (2009). Macrobenthic structure wasanalysed both considering feeding guilds' abundance matrix andthe taxa � sites matrix. The square-root transformed data wasanalysed by cluster techniques using the PRIMER v5 software.Similarity between samples was determined with the BrayeCurtiscoefficient and the classification diagram applied the group averagealgorithm. Two-wayANOVAs for factors TIME and SITEwere used toexamine patterns of variation in the univariate measures. Whena significant difference was detected, pairwise comparisons wereperformed through the Student-Newman-Keuls test using STATIS-TICA v6. The SIMPER procedure was carried out to identify the taxahaving the greatest contribution to the dissimilarity between sites.Two-way crossed PERMANOVAs, employing the PERMANOVAþadd-on in PRIMER v6 (Anderson et al., 2008), was performed on theBrayeCurtis similarity matrix after square-root transformation ofabundance and biomass data for both taxonomic and trophicmatrices, in order to test the null hypothesis of no significanttemporal and spatial differences on the multivariate structure andcomposition of macrobenthic assemblages. The factors in test wereTime (four levels; fixed) and Site (five levels; fixed). Significantterms were investigated using a posteriori pairwise comparisonsbetween sampling periods and sites with the PERMANOVAt-statistic and permutations under a reduced model (Andersonet al., 2008). Whenever there were not enough possible permuta-tions to get a reasonable test, the Monte Carlo p-values were usedinstead. Although PERMANOVA is specifically designed to detectlocation differences, it is also sensitive to differences in dispersionamong groups. Hence, a significant effect detected by the PERMA-NOVA may be due to location effects, dispersion effects or both. Inorder to assess the differences in the relative dispersions of theindividual cells used to test the significance of the interaction termin the PERMANOVA, a test of homogeneity of dispersions (PERM-DISP) was performed (Anderson et al., 2008).

To evaluate the tolerance behaviour of benthic taxa to contam-inants (metals and organic carbon, organic nitrogen and phos-phorus), a correlation analysis was performed using STATISTICA v6software. Al and Fe are major constituents of sediments and theirlevels are mainly associated with the sediment grain size, thus bothelements are regarded usually as proxy of fine particles (Windomet al., 1989) rather than contaminants. Therefore, those elementswere not considered in the correlation analysis. Only taxa withmore than 20 individuals were used. On the other hand, associa-tions between macrobenthic abundance and biomass and envi-ronmental parameters were analysed by a redundancy analysis(RDA), using the CANOCO v.4.5 program. This analysis was alsoperformed with the feeding guild data, both in terms of abundanceand biomass. The RDA analysis was chosen because the DetrendedCorrespondence Analysis identified that biological data were line-arly responding to environmental gradients. The matrixes ofexplanatory variables were constructed to evaluate correlationsbetween environmental parameters, species and variance in sites’patterns. The percent variability explained by the canonical corre-spondence analysis was determined by dividing the sum of allcanonical eigenvalues by the overall sum of eigenvalues from thecorrespondence analysis (ter Braak and Verdonschot,1995). All taxawere included in the analysis but only those contributing to 75% of

S. Carvalho et al. / Marine Environmental Research 71 (2011) 97e110100

the total abundance or biomass per sampling period were repre-sented in the diagrams. The BIOENV routine was used to identifythe suite of environmental variables best explaining variation inmacrofaunal communities. Prior to the analysis environmentalvariables were normalised and transformed. The similarity matrixobtained through Euclidean distances (environmental data) wasmatched with biotic BrayeCurtis similarity matrices.

3. Results

3.1. Water and sediment characteristics

In spring and summer, water temperature reached high valuesat the branches (sites 4 and 5) (Table 1). Salinity was generallylower at site 4 than in the other sites due to freshwater inputs.Dissolved oxygen at sites 1, 2 and 3 was around 100%, while itrangedwithin broader intervals at sites 4 and 5. In summer and fall,undersaturated levels were registered at site 4. The suspendedparticulate matter, phosphate, chlorophyll a, concentrations ofammonium and nitrate þ nitrite were in general higher at this site(Table 1). In summer, the five sites exhibited identical levels ofammonium and nitrate þ nitrite, while the maximum values wereregistered in winter at site 4. Despite these differences betweensites and sampling time, KeW ANOVA performed separately forfactors TIME and SITE showed that for most of these variablessignificant differences were found between sampling times but notbetween sites (Material, Table S1). Only phosphate and suspendedparticulate matter showed a SITE effect: the former was found to besignificantly higher at site 4 than in the remaining sites (H¼ 10.511,p ¼ 0.033), while the latter was significantly higher at site 4 than atsites 1 and 2 (H ¼ 11.414, p ¼ 0.022). For the other variables,temperature was significantly higher in summer than in winter(H ¼ 11.160, p ¼ 0.011), while salinity was also significantly higherin summer than in fall (H ¼ 11.411, p ¼ 0.010). Ammonium wassignificantly lower in summer than in fall and winter (H ¼ 15.526,p ¼ 0.001), whereas nitrate þ nitrite were significantly higher inwinter than in spring and summer (H ¼ 14.480, p ¼ 0.002). Foroxygen, values registered during spring were significantly higherthan those from fall (H ¼ 9.234, p ¼ 0.026).

Metal levels were higher in sediments of the branches (sites 4and 5) and mid-upper lagoon (site 3) probably due to their affinityto organic matter (Windom et al., 1989) (Table 2). In general, Cr, Cu

Table 1Water temperature (T), salinity (S), dissolved oxygen (DO), suspended particulate matterðPO3�

4 Þ and chlorophyll a (Chl a) determined seasonally in five stations of the Óbidos lag

Season Site T (�C) S DO (%) SPM (mg L�1)

Winter 1 11 34 102 232 11 34 114 213 11 34 106 334 10 29 114 595 10 32 105 31

Spring 1 17 35 110 252 18 35 106 353 20 33 122 554 22 28 127 1535 21 31 156 96

Summer 1 19 36 105 222 19 36 108 303 21 36 105 524 24 37 85 1175 29 37 115 105

Fall 1 20 34 107 642 20 33 98 523 19 34 93 584 21 27 81 1055 20 30 89 122

and Ni exhibited maximum levels in spring, while Pb peaked inwinter and Cd in summer. Biomass of Ulva spp. in the sediment wasalways lower at sites 1 and 2 (Table 2). The highest biomass valuewas registered in site 5 during spring. Site 3 also registered itsmaximum in spring, while for site 4 the peak was found during fall(Table 2). Despite these temporal trends, KeW ANOVA performedfor factors TIME and SITE separately showed that differencesbetween sampling times were not significant (SM, Table S1). Thisanalysis confirmed the higher contaminated or organicallyenriched status of mid-upper and inner branches when comparedwith the lower lagoon areas (sites 1 and 2). Cd (H ¼ 13.357,p ¼ 0.010), Fe (H ¼ 13.286, p ¼ 0.010) and organic nitrogen(H ¼ 13.735, p ¼ 0.008) were significantly higher at sites 3, 4 and 5than at sites 1 and 2. For other parameters differences were onlydetected in relation to site 1, such as for Cr (values significantlyhigher at site 3 than 1; H ¼ 11.129, p ¼ 0.025), Cu (values signifi-cantly higher at sites 4 and 5 than 1; H ¼ 12.243, p ¼ 0.016), Pb(values significantly higher at sites 3 and 4 than 1; H ¼ 13.657,p ¼ 0.008), Al (values significantly higher at site 5 than 1; H ¼13.357, p ¼ 0.004), Ni and organic carbon (significantly highervalues at sites 3, 4 and 5 than 1; H ¼ 10.686, p ¼ 0.030; H ¼ 12.143,p ¼ 0.016, respectively. For total phosphorus, concentrations werefound to be significantly higher at sites 4 and 5 when comparedwith sites 1 and 2, while values found at site 3 were also signifi-cantly higher than those of site 1 (H ¼ 15.329, p ¼ 0.004).

3.2. Macrobenthic communities

In the present study 178 taxa were identified in a total of 11284individuals. Rare taxa (those presenting 1 or 2 individuals) werewell represented in the taxonomic matrix (72 taxa). The maintaxonomic groups identified were Polychaeta (79 taxa), Bivalvia(38 taxa), Amphipoda (21 taxa), Gastropoda (20 taxa) and Oli-gochaeta (3 taxa).

The gastropod Hydrobia ulvae was the most abundant species(1836 individuals) accounting for 16% of the total abundance, fol-lowed by Capitella spp. (14%), Tubificoides benedii (12%), Hetero-mastus filiformis (9%) and Streblospio shrubsolii (7%). Together, these5 taxa accounted for 58% of the total abundance. In terms of occur-rence, the most frequent species were H. ulvae, observed in 75%of samples, Nemertea (72%), Capitella spp. (53%), Monocorophiumascherusicum (53%), H. filiformis (45%), T. benedii (38%), Notomastus

concentration (SPM), ammonium ðNHþ4 Þ, nitrate þ nitrite ðNO�

3 þ NO�2 Þ, phosphate

oon.

ðNHþ4 Þ (mM) ðNO�

3 þ NO�2 Þ (mM) ðPO3�

4 Þ (mM) Chl a (mg L�1)

22 26 1.2 0.617 25 1.0 0.737 50 2.1 2.651 76 3.4 1035 48 2.1 1.013 2.3 0.3 1.96.8 0.7 0.5 1.94.3 0.8 0.4 2.25.9 13 3.5 6.02.8 0.9 0.8 3.21.5 0.5 0.4 0.50.6 0.3 0.4 0.50.7 0.2 1.2 0.61.2 0.5 5.9 1.01.2 0.3 2.9 0.85.5 17 1.0 1.0

13 36 2.2 0.87.8 20 1.1 1.0

58 40 6.9 1.017 34 2.4 0.5

Table 2Metals (Al, Fe, Cr, Cu, Ni, Pb, Cd), organic carbon (Corg), organic nitrogen (Norg), total phosphorus (P) and biomass of Ulva spp. in sediments collected seasonally in five sites ofthe Óbidos lagoon.

Season Site Corg Norg Al Fe Cr Cu Ni Pb Cd P Ulva

(%) (%) (%) (%) mg g�1 mg g�1 mg g�1 mg g�1 mg g�1 mg g�1 g m�2

Winter 1 0.29 0.014 0.41 0.11 1.7 1.2 1.3 4.6 0.063 35 0.152 0.35 0.017 0.47 0.12 2.5 2.4 1.9 5.2 0.04 52 0.063 1.9 0.19 9.5 4.4 88 48 36 49 0.20 584 9.34 1.5 0.17 11 4.7 87 76 35 52 0.27 855 0.845 1.4 0.097 11 4.9 88 58 37 49 0.19 666 4.2

Spring 1 0.22 0.007 0.21 1.2 1.1 1.4 0.84 2.4 0.019 14 0.002 1.8 0.099 9.4 2.0 93 48 42 36 0.15 390 0.173 2.4 0.13 11 1.3 101 72 45 40 0.16 304 904 2.6 0.16 9.1 3.4 86 41 39 35 0.15 597 3.65 2.9 0.19 12 1.3 111 68 49 38 0.13 434 120

Summer 1 0.30 0.017 0.27 0.076 0.78 0.16 0.39 2.9 0.029 108 0.002 0.41 0.012 0.69 0.14 2.2 0.58 1.6 4.8 0.026 311 1.13 1.8 0.17 10 4.8 69 43 29 39 0.22 498 0.424 1.2 0.12 9.4 5.2 72 58 30 48 0.29 603 6.65 1.3 0.13 11 4.7 56 46 24 33 0.23 598 45

Fall 1 0.02 0.002 0.42 0.03 0.85 0.63 0.71 3.5 0.021 62 0.002 0.99 0.005 0.39 0.22 3.3 1.5 1.3 3.4 0.021 123 0.003 1.4 0.14 11 4.7 72 43 30 37 0.17 428 0.814 2.1 0.078 11 4.4 71 57 29 44 0.23 505 145 1.4 0.12 11 4.2 69 54 28 38 0.21 564 2.8

S. Carvalho et al. / Marine Environmental Research 71 (2011) 97e110 101

sp. (37%), Microdeutopus gryllotalpa (33%) and undetermined Tubi-ficidae (32%). The remaining species occurred in less than 30% of thesamples.

3.2.1. Taxonomic compositionThe lowest number of taxa and abundancewere observed in site

5 during spring (2.7 � 0.6 taxa � 0.05 m�2; 4.3 � 2.1 ind. �0.05 m�2). The CLUSTER analysis showed that Sp5 samples wereclearly separated from the remaining (Fig. 2). Abundance at site 5 inspring was significantly lower than at sites 2, 3 and 4, whereasShannon diversity was also found to be significantly lower than atsite 3 (SM, Table S2). All samples collected at site 1 were alsoseparated from the remaining, due to generally low number of taxaand abundance. The preferential distribution of nemerteans,Ophryotrocha dubia, Pisione remota, and Lekanesphaera levii at site 1was indicated by SIMPER analysis as relevant to the separation ofthis site from sites 3, 4 and 5. Samples from site 4 also clusteredapart and SIMPER analysis indicated the preferential abundance ofpolychaetes Hediste diversicolor, Polydora ligni and S. shrubsolii inthis site was relevant for this separation (SM, Table S3). For thebiological variables number of species, abundance and Shannon

Fig. 2. Cluster analysis of macrobenthic abundance data using BrayeCurtis similarity index.Shannon Winner diversity index (H0), as well as mean abundance of the main taxonomic gro4, 5 e sampling sites.

diversity, post-hoc comparisons did not detect any differencesbetween sites inwinter (SM, Table S2). Biological associations usingbiomass data were slightly different (Fig. 3). For biomass, two-wayANOVA did not detect any significant difference between sites andsampling periods (SM, Table S2).

PERMANOVA analyses showed a highly significant interactionbetween factors TIME and SITE on the composition and structure ofmacrobenthic communities either considering abundance orbiomass data (SM, Tables S4 and S5), indicating that the effects didnot vary consistently. Post-hoc comparisons showed that for bothabundance and biomass, the highest differences between siteswere found in winter, followed by spring and fall. On the otherhand, in summer, differences between sites were considerablyattenuated (for abundance: 1s3; for biomass: 1s3; 3s4, 5).Concerning temporal changes in each site, macrobenthic assem-blages from site 1 were very similar during the year both inabundance and biomass (SM, Tables S4 and S5). Significant differ-ences were only detected between winter and spring but at a lowsignificant level (p < 0.05). Macrobenthic communities fromthe remaining sites presented higher differences for abundancethan for biomass data. PERMDISP analysis revealed significant

Mean number of taxa (S, taxa � 0.05 m�2), mean abundance (N, ind. � 0.05 m�2), meanups per site and sampling period. W e winter; Sp espring; S e summer; F e fall. 1, 2, 3,

Fig. 3. Cluster analysis of macrobenthic biomass data using BrayeCurtis similarity index. Mean total biomass (B, g � 0.05 m�2), mean Shannon Winner diversity index (H0), andmean biomass of the main taxonomic groups (B, g � 0.05 m�2) per site and sampling period. W e winter; Sp espring; S e summer; F e fall. 1, 2, 3, 4, 5 e sampling site.

S. Carvalho et al. / Marine Environmental Research 71 (2011) 97e110102

differences in dispersion for factor TIME (F ¼ 5.0023, p¼ 0.012) butnot for factor SITE (F ¼ 0.65107, p ¼ 0.7191). Post-hoc comparisonsshowed that significant differences were found between winterand the remaining sampling periods and, when a posterior analysiswas carried out excluding this sampling period (not shown), resultswere no longer significant.

3.2.2. Trophic compositionThe temporal and spatial patterns of macrobenthic communities

from the Óbidos lagoon were also analysed using feeding guilddata, both in terms of abundance (Fig. 4) and biomass (Fig. 5).Samples from the inlet site (except W1) were clearly separated inthe analysis and more related with Sp5 (Fig. 4). All these samplesshare low abundance of all feeding guilds, resulting in intermediateto high diversity levels (Fig. 4). A two-way ANOVA performed forfactors TIME and SITE showed a significant SITE effect for DF/SF andC/DF, while for the latter a TIME effect was also detected. DF/SF taxawere significantly higher at sites 4 and 5 than at the remainingsampling sites. On the other hand, C/DF were significantly moreabundant inwinter and in sites 2 and 3 than in site 5 (SM, Table S6).Omnivores (H. diversicolor) were numerically dominant at site 4;the abundance peak observed in spring resulted in significantlyhigher values in this sampling period than in the remaining(SM, Table S6). As interaction termwas generally significant, resultsof the main test cannot be properly interpreted.

Concerning biomass data, it was observed a clear increase of SF(mostly bivalves) particularly inwinter (sites 2, 3 and 5), F5 and Sp3(Fig. 5). A higher contribution of DF/C (Nassarius pfeifferi, Nassariuscf. cuvieri, Nassarius incrassatus, Nassarius reticulatus) especially inmost of these samples and of omnivores (H. diversicolor) duringspring in the Barrosa branch (site 4) was also observed (Fig. 5). Onthe other hand, DF/SF contribution in this branch (especially due toS. shrubsolii, M. ascherusicum, Monocorophium insidiosum andMonocorophium sextonae) was considerably reduced whenassessed using biomass. For biomass data, the two-way ANOVAshowed that sites were more similar when the composition basedon trophic groups was considered. Half of the trophic groupsconsidered (C, SF, C/H, DF/C and C/SF) did not show any significantdifference (SM, Table S6).

As for taxonomic composition, PERMANOVA analyses showeda highly significant interaction between factors TIME and SITE onthe composition and structure of trophic groups either consideringabundance or biomass data (SM, Tables S7 and S8), indicating thatthe effects did not vary consistently. Post-hoc comparisons showedthat for both abundance and biomass, the highest differencesbetween sites were found in spring and winter. In summer, nosignificant difference was detected between sites. Concerningtemporal changes in each site, macrobenthic assemblages from site

1were very similar during the year both in abundance and biomass.Only winter period was found to be significantly different fromspring period (SM, Tables S7 and S8). Macrobenthic assemblagesfrom site 2 were not significantly different during the year forbiomass data. Except for site 1, higher differences were found forabundance than for biomass data. As for taxonomic composition,PERMDISP analysis revealed significant differences in dispersion forfactor TIME (F ¼ 4.0855, p ¼ 0.0226). Post-hoc comparisons evi-denced the contribution of winter sampling period for this result.

3.3. Relationship between biological and environmental parameters

The correlation analysis performed between metals, organiccarbon and nitrogen and total phosphorus in sediment and benthictaxa, showed that only 25 out of 43 taxa analysed were significantlycorrelated to at least one of the environmental parametersconsidered. Most of these taxa showed a positive correlation, whileonly five taxa showed the opposite trend (Nemertea, Opheliidae,Ophryotrocha dubia, P. and Lekanesphaera levii) (Table 3). Among thetaxa showing a tolerant behaviour, deposit-feeders are the domi-nant trophic group, while taxa showing sensitive behaviour aremainly carnivores. Concerning their ecological behaviour, somediscrepancies were found. Among the taxa showing positivecorrelations with the environmental variables, 4 (Rissoa spp.,Parvicardium exiguum, Iphinoe serrata and Amphipholis squamata)were considered sensitive to organic enrichment (www.azti.es). Onthe other hand, among those negatively correlated, only onespecies (P. remota) is considered sensitive; the remaining taxa wereconsidered either tolerant (Nemertea, L. levii) or second-orderopportunist (O. dubia) (www.azti.es) (Table 3).

As several environmental parameters were highly correlated,the final environmental matrix used in the RDA analysis comprisedthe following environmental variables: temperature, salinity, sus-pended particulate matter, ammonium and chlorophyll a in surfacewater; and concentration of total phosphorus and biomass of Ulvaspp. in sediments. All metals, organic carbon and organic nitrogenwere highly correlated (r > 0.9) with total phosphorus, whilephosphate and nitrate þ nitrite were highly correlated (r > 0.9)with ammonium. The variables retained for the analysis showednone or low correlation levels.

3.3.1. Taxonomic compositionConcerning macrobenthic abundance data, RDA analysis indi-

cated that total variance explained by biotic and environmentaldata was 85% (for the first three ordination axes). During fall andsummer, samples from the Bom-Sucesso branch (site 5) tend to becloser to samples from the other lagoon branch (site 4), whilesamples collected in site 2 during fall were very similar to those of

Fig. 4. Cluster analysis of feeding-guilds’ abundance data using BrayeCurtis similarity index and its respective distribution per site and sampling period (see material and methodssection for abbreviations). W e winter; Sp espring; S e summer; F e fall. 1, 2, 3, 4, 5 e sampling site. H0 e feeding diversity estimated using the Shannon-Wiener index.

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site 1 (Fig. 6A). The RDA analysis pointed out P. remota, Micro-phthalmus pseudoaberrans and Opheliidae as characteristic of theselatter samples, where low values of total phosphorus, suspendedparticulate matter and chlorophyll a were evident (Fig. 6A). Only

Fig. 5. Cluster analysis of feeding-guilds’ biomass data using BrayeCurtis similarity index asection for abbreviations). W e winter; Sp espring; S e summer; F e fall. 1, 2, 3, 4, 5 e sa

during winter, the inlet area presented macrobenthic assemblagesmore similar to those found in the mid lagoon area (Fig. 6A).This result was related to the presence of characteristic speciesfrom this lagoon area towards the sea, which was concomitant with

nd its respective distribution per site and sampling period (see material and methodsmpling site; H0 e feeding diversity estimated using the Shannon-Wiener index.

Table 3Correlations between metals (Cr, Ni, Cu, Cd, Pb), organic carbon (Corg), organic nitrogen (Norg) and total phosphorus (P) in sediment and most abundant taxa. Feeding guilds(FG) and Ecological groups (EG) are also indicated for each taxa. Significant correlations (p < 0.05) are indicated in bold. NA e not assigned.

Group Taxa Cr Ni Cu Cd Pb Corg Norg P FG EG

Tolerant behaviourOligochaetaTubificidae 0.21 0.19 0.19 0.13 0.27 0.04 0.06 0.28 DF VTubificoides benedii 0.27 0.26 0.24 0.16 0.32 0.14 0.14 0.26 DF V

PolychaetaDesdemona ornata 0.16 0.14 0.28 0.27 0.25 0.05 0.21 0.37 DF IIHediste diversicolor 0.19 0.21 0.14 0.13 0.15 0.27 0.24 0.28 O IIIHeteromastus filiformis 0.23 0.21 0.20 0.25 0.32 0.10 0.23 0.33 DF IVNotomastus sp. 0.26 0.27 0.24 0.09 0.19 0.27 0.22 0.01 DF IIIPolydora ligni 0.22 0.20 0.33 0.31 0.30 0.13 0.29 0.46 DF/SF IVStreblospio shrubsolii 0.23 0.22 0.28 0.32 0.28 0.17 0.27 0.40 DF/SF III

GastropodaHydrobia ulvae 0.19 0.18 0.09 0.14 0.22 0.15 0.29 0.15 DF/H IIIRissoa spp. 0.17 0.15 0.07 0.14 0.22 0.13 0.31 0.14 H I

BivalviaAbra alba 0.28 0.26 0.31 0.24 0.34 0.11 0.16 0.34 DF/SF IIIAbra segmentum 0.20 0.19 0.26 0.26 0.25 0.25 0.12 0.17 DF/SF IIIParvicardium exiguum 0.18 0.16 0.21 0.24 0.25 0.09 0.10 0.29 SF I

InsectaChironomidae 0.16 0.14 0.29 0.34 0.27 0.01 0.16 0.39 DF III

IsopodaCyathura carinata 0.19 0.19 0.17 0.23 0.21 0.29 0.17 0.23 DF/C III

CumaceaIphinoe serrata 0.19 0.18 0.11 0.16 0.25 0.14 0.29 0.18 DF I

AmphipodaMonocorophium insidiosum 0.16 0.15 0.21 0.32 0.24 0.02 0.11 0.24 DF/SF IIIMonocorophium ascherusicum 0.18 0.16 0.26 0.36 0.27 0.03 0.15 0.34 DF/SF IIIMonocorophium sextonae 0.13 0.11 0.24 0.25 0.2 0.03 0.16 0.3 DF/SF III

PhoronidaPhoronida 0.31 0.28 0.29 0.22 0.36 0.15 0.16 0.28 SF II

EchinodermataAmphipholis squamata 0.19 0.17 0.15 0.17 0.26 0.14 0.17 0.21 DF I

Sensitive behaviourNemerteaNemertea �0.26 �0.26 �0.25 �0.21 �0.22 �0.31 �0.32 0.25 C III

PolychaetaOpheliidae �0.38 �0.37 �0.38 �0.35 �0.39 �0.20 �0.37 �0.36 NA NAOphryotrocha dubia �0.26 �0.26 �0.26 �0.19 �0.26 �0.26 �0.23 �0.31 C IVPisione remota �0.34 �0.34 �0.34 �0.34 �0.35 �0.15 �0.34 �0.31 C I

IsopodaLekanesphaera levii �0.47 �0.46 �0.47 �0.44 �0.47 �0.34 �0.44 �0.44 DF/H III

Note: only taxa with significant correlations are present.

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the presence of Ulva spp. in the sediments. Indeed, a significantlyhigher number of taxa (19.3� 7.4 inwinter; 7.0� 2.6, 5.6� 4.0, and3.0 � 2.1, for spring, summer and fall respectively) and individuals(116.3� 47.9 inwinter; 18.7�4.7, 7.7�4.5, and 7.0� 5.6, for spring,summer and fall respectively) were registered in site 1 duringwinter. Most samples from the middle lagoon area (W2, Sp2, S2,Sp3, S3, F3), as well as W1 and Sp5 were associated with low valuesof total phosphorus, suspended particulate matter, chlorophylla and biologically characterized by Notomastus spp. and nemer-teans (Fig. 6A). These samples were also related with increasingbiomass values of Ulva spp. (Fig. 6A). During winter, samples fromsites 3 and 5were separated from the remaining due to the increasein abundance of the annelids Capitella spp., T. benedii, TubificidaeandH. filiformis and the gastropodH. ulvae and to a lesser extent thebivalve Abra alba and Cnidaria (Fig. 6A). Samples from site 4 werecharacterized by H. diversicolor, S. shrubsolii, M. ascherusicum,M. insidiosum, M. sextonae and Cyathura carinata. These speciesshowed a higher affinity with areas with high chlorophyll a, sus-pended particulate matter (H. diversicolor, C. carinata), total phos-phorus and ammonium (corophiids) (Fig. 6A).

RDA analysis based on biomass data displayed some differenceson spatial and temporal patterns of macrobenthic communities.The total variance explained by biotic and environmental data was83.5% (first three ordination axes). Samples from the inlet (site 1)

and fall and winter samples from mid-upper lagoon (site 2) weremore closely related whereas the dissimilarities observed betweenBarrosa branch (site 4) and the lower-inner lagoon area (site 3 and5) were less evident (Fig. 6B). The biomass distribution patterns ofthe bivalves Venerupis senegalensis and Cerastoderma edule as wellas the decapod Carcinus maenas were associated with salinity(Fig. 6B). On the other hand, C. carinata, Labidoplax digitata andAscidiacea, displayed a high affinity with total phosphorus andammonium gradients (Fig. 6B). As expected, the contribution ofbivalves and gastropods is more evident, replacing the observeddominance of polychaetes in terms of abundance.

For both data sets, the BIOENV procedure using the sameenvironmental variables as the RDA analysis, indicated total phos-phorus and biomass of Ulva spp. in the sediment as the variablessignificantly influencing biological data (abundance: R ¼ 0.458,p ¼ 0.04; biomass: R ¼ 0.394, p ¼ 0.03). Due to the high correlation(r > 0.9) between all metals, organic carbon and organic nitrogen,although not considered in the analysis these parameters are alsorelated with biological data.

3.3.2. Trophic compositionConcerning trophic composition, the RDA analysis showed

that the total variance explained by the biotic and environmentaldata approximately 97% both abundance and biomass datasets

Fig. 6. Redundancy analysis (RDA) ordination triplot for macrobenthic species square-root abundance (A) and biomass (B) data. Circles represent the site position within theordination space. The vector lines reflect the relationship of significant environmentalvariables to the ordination axes, and their length is proportional to their relativesignificance. Only taxa contributing with 75% of total abundance per sampling periodwere included in the diagram. Chl a, chlorophyll a concentration in the surface water;P, total phosphorus; NH4

þ, ammonium; SPM, suspended particulate matter; T, watertemperature; S, salinity; Ulva spp., biomass (AFDW) of Ulva spp. in the sediment.Abraalb e Abra alba; Carcmae e Carcinus maenas; Ceraedu eCerastoderma edule;Monoach e Monocorophium ascherusicum; Monoins - Monocorophium insidiosum;Monosex - Monocorophium sextonae; Cyatcar e Cyathura carinata; Hedidiv e Hedistediversicolor; Hetefil e Heteromastus filiformis; Hydrulv e Hydrobia ulvae; Labidig e

Labidoplax digitata; Micrpse e Microphthalmus pseudoaberrans; Muscmar e Musculusmarmoratus; Nassinc e Nassarius incrassatus; Notosp. e Notomastus sp.; Pisirem e

Pisione remota; Streshr e Streblospio shrubsolii; Tubiben e Tubificoides benedii; Rudidece Ruditapes decussatus; Venesen e Venerupis senegalensis.

Fig. 7. Redundancy analysis (RDA) ordination triplot for feeding-guilds’ square-rootabundance (A) and biomass (B) data. Circles represent the site position within theordination space. The vector lines reflect the relationship of significant environmentalvariables to the ordination axes, and their length is proportional to their relativesignificance. Chl a, chlorophyll a concentration in the surface water; P, total phos-phorus; NH4

þ, ammonium; SPM, suspended particulate matter; T, water temperature;S, salinity; Ulva spp., biomass (AFDW) of Ulva spp. in the sediment.

S. Carvalho et al. / Marine Environmental Research 71 (2011) 97e110 105

(3 first axes). Deposit-feeders/suspension-feeders were mainlyassociated with total phosphorus and chlorophyll a but also withsuspended particulatematter and ammonium (Fig. 7A). Omnivores’abundance was also related with these variables, particularly

suspended particulate matter and chlorophyll a (Fig. 7A). Carni-vores showed a high affinity with salinity (Fig. 7A). The otherfeeding guilds were less abundant, resulting in low discriminationlevels in the analysis. Concerning biomass data, suspension feederswere found to be associated with higher salinity, while deposit-feeders/carnivores were associated with Ulva spp. (Fig. 7B).

For the abundance data set, the BIOENV procedure indicatedtotal phosphorus and biomass of Ulva spp. in the sediment as thevariables significantly influencing biological data (R ¼ 0.394,p ¼ 0.05), although correlation was weak. For the biomass data set,none of these variables were indicated as being significantly relatedwith biological data.

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4. Discussion

4.1. Spatial and temporal dynamics

In the Óbidos lagoon, the main temporal pattern was a peak ofmacrofauna abundance during winter, and a general reduction inabundance and number of species during summer/fall, which is inaccordancewith the reported for other European lagoons (e.g. Ariasand Drake, 1994; Tagliapietra et al., 1998; Magni et al., 2006; Comoand Magni, 2009). This macrotidal Atlantic coastal lagoon wasfound to be more similar to the mesotidal Atlantic lagoon located inArcachon Bay (Bachelet et al., 2000, 2005) than to the microtidalMediterranean lagoons (Mistri et al., 2000, 2001) and the one fromthe Ionian Sea (Koutsoubas et al., 2000). The Atlantic lagoons aremore diverse than those from Mediterranean and Ionian Sea,which may result from the greatest seasonal variation on envi-ronmental parameters observed in the latter systems (Koutsoubaset al., 2000; Mistri et al., 2001; Munari et al., 2005). The existenceof smaller seasonal variations concerning environmental variablesin Atlantic lagoons when compared to the others previouslymentioned, probably allows the colonization of a higher number ofspecies. This is supported by a good proportion of rare speciesobserved in these systems (present study; Blanchet et al., 2005).Comparing the faunal composition of lagoons from the Atlantic,Mediterranean and Ionian Sea, some benthic taxa are consistentlypresent (Oligochaeta, Chironomidae, Hydrobia spp., Abra segmen-tum (¼ovata), Cerastoderma spp., Capitella spp., H. filiformis, H.diversicolor, S. shrubsolii, M. insidiosum and M. gryllotalpa) (presentstudy; Bachelet et al., 2000; Koutsoubas et al., 2000; Mistri et al.,2000, 2001). This highlights the resilience of these taxa, as theyare generally able to maintain stable populations in systems withvery distinct characteristics.

In the present study, the comparative analysis of two differentdata sets (macrobenthic taxonomic composition and macrobenthictrophic composition) resulted in different spatial and temporalpatterns. Moreover, for each data set, the patterns were generallynot coincident for abundance and biomass data. This resultconfirms that, within these systems, both biological variables mayprovide complementary information on the relationships betweenenvironmental and biological data. Concerning the temporal andspatial patterns, PERMANOVA analyses indicated that, regardlessthe data set considered, patterns were not consistent along theyear. Furthermore, dispersion was found to be significant for factorTIME but not for factor SITE, indicating that differences foundbetween sampling periods may result from changes in the spatialheterogeneity of assemblages and not only to changes in theassemblage structure and composition.

Macrobenthic communities close to the sea inlet (site 1) gener-ally clustered apart from the remaining and were the ones showingthemost consistent biological patterns along the year. The biologicalzonation between innermost parts of the lagoon and the areas closeto the sea inlet had been already recognised for the Gialova lagoonin the Ionean Sea (Koutsoubas et al., 2000). This separation may bedue to the marine influence dictated by the proximity with thelagoon inlet andwith the higher hydrodynamic conditions observedthere. This area supports a naturally impoverished assemblage,typical of clean coarse sand and hydrodynamic subtidal areas(Snelgrove and Butman, 1994) and had already been recognised inprevious surveys (Carvalho et al., 2005). Moreover, this is the leastcontaminated area and also the one experiencing smaller temporalvariations for environmental variables, which can support the lowtemporal variability observed inmacrobenthic communities. On theother hand, the low organic content observed and/or the almostabsence of vegetal debris limit the colonization of species withdeposit feeding and herbivory behaviours, supporting the

dominance of carnivores. The main difference in the structure andcomposition of macrobenthic fauna detected within this site wasfound betweenwinter and spring. The presence of Ulva debris in thewinter samples could enhance the occurrence of less typical taxa byproviding additional feeding niches to macrobenthic communitiesallowing for the colonization of a significantly higher number of taxaand individuals. Duringwinter, abundance, numberof taxa, diversityand biomass increased considerably in the lagoon, presenting nosignificant differences between sites.

In opposition to the observed for univariate variables, macro-benthic community structure along the lagoon was found to differgreatly between sites in winter (taxonomic composition) or spring(trophic composition). On the other hand, in summer, differenceswere highly attenuated. In what concerns the taxonomic compo-sition, this pattern generally coincides with the peak of abundanceand number of taxa inwinter and theminimum of both variables insummer (except for sites 1 and 2). The constraints imposed by theenvironmental stressors observed during summer, particularlywithin the inner areas, seem to flatten the differences betweenbenthic assemblages. This probably results from the decline of rarespecies, unable to cope with the harsh conditions observed. Theseresults support the dynamic nature of these coastal systems.Experiencing frequent and extensive disturbance events, macro-benthic communities are constantly re-establishing and successionis continuous (Munari et al., 2005).

4.2. Relationship between biological and environmental parameters

The establishment and survival of marine benthic animalswithin a certain area relies on their capacity to cope with the localenvironmental conditions, which is mostly determined by theirphysiological requirements, such as food intake (Roth and Wilson,1998). Feeding modes and consequently the trophic compositionof macrobenthic communities are, on the other hand, influenced byenvironmental factors (see review by Snelgrove and Butman,1994).Therefore, it is expected that several feeding groups would be ableto be found in the same areas, but in different proportions,depending on the hydrodynamic conditions, which are also deter-minant for sediment characteristics (Gamito and Furtado, 2009).

Despite some inaccuracy thatmight be associatedwith the lack ofexperimental information on feeding modes of several species(Garcia-Arberas and Rallo, 2002) and the ability of other species toswitch between feeding modes (Ysebaert et al., 2003) it is generallypossible to infer on the biotic and environmental relationships basedon the community trophic structure (Garcia-Arberas andRallo, 2002;Wieking and Kröncke, 2003; Ysebaert et al., 2003; Gaudêncio andCabral, 2007; Gamito, 2008; Gamito and Furtado, 2009).

In the present study, carnivores (especially, the polychaetesPisione remota and Microphthalmus pseudoaberrans) were charac-teristic of coarser sands from the inlet area and mid-upper lagoon(see Carvalho et al., 2005, for sediment characterization). Theassociation of carnivory feeding mode with coarse and clean sandybottoms has been previously reported for estuarine (Garcia-Arberasand Rallo, 2002) and coastal waters (Gaston, 1987; Dolbeth et al.,2009). This was attributed to higher oxygen penetration in thesediment and to the enhancedmobility of the interstitial organismsthat the polychaetes feed on, promoted by coarse sediments(Gaston,1987). Although not restricted to the inlet area, nemerteanswere determinant for the dominance of carnivores in this area. Asthey have a predator behaviour (feeding mainly on polychaetes andamphipods) (Thiel and Kruse, 2001 and references therein), theirgenerally widespread distribution could be related with the domi-nance of polychaetes and amphipods along the lagoon.

Biological patterns in the Barrosa area (site 4) reflected theharshness of the environment. Dominant species in this area were

S. Carvalho et al. / Marine Environmental Research 71 (2011) 97e110 107

S. shrubsolii, H. diversicolor and, to a lesser extent, C. carinata. Bothpolychaetes have been shown to resist to severe environmentalconditions (Tagliapietra et al., 1998; Carvalho et al., 2007).H. diversicolorwas even found to be able to copewith hypoxia (Grayet al., 2002 for a review), which is known to occur within theBarrosa area particularly in summer (Pereira et al., 2009a, 2010),and to be metal resistant, namely to copper and zinc (Pook et al.,2009). The main prey item of C. carinata is the polychaeteH. diversicolor (Wägele et al., 1981). While the polychaete wasexclusive of the Barrosa branch site, the isopod was more wide-spread. However, redundancy analysis indicated that both specieswere highly correlated; we may speculate that the distribution ofthe isopod could be conditioned, among other, by predator/preyinteractions, as previously suggested for the Ria de Aveiro lagoon(Nunes et al., 2008). The Barrosa branch is a low energy area withhigh levels of nutrients and chlorophyll a, which was associatedwith eutrophication (Pereira et al., 2009b). During summer, dis-solved oxygen in the water column may decrease to less than 50%saturation during the night (Pereira et al., 2009a, 2010). Underthese conditions, sediment acts as an internal source of nutrients(ammonium and phosphate) and metals (Fe, Mn, Pb) (Pereira et al.,2009a, 2010), which are known to strongly influence the temporalpatterns of macrobenthic communities, namely by reducing thenumber of species (Ponti and Abbiati, 2004). This is reflected in thefew species that were able to survive during summer in the Barrosabranch (particularly, M. ascherusicum, M. insidiosum and S. shrub-solii). However, the moderate contamination by metals and highavailability of nutrients are not completely impairing the estab-lishment and development of typical communities from organicenriched bottoms found elsewhere (Tagliapietra et al., 1998; Garcia-Arberas and Rallo, 2002; Como and Magni, 2009).

Even facing a moderate contamination scenario, the mid-upperlagoon area (site 3) and Bom-Sucesso branch (site 5) generallysupported the richest macrobenthic assemblages. On the otherhand, mid-lower area (site 2) exhibited an intermediate contami-nation condition between the inlet and the other areas. Only Cd andFe concentrations were significantly lower than the observedwithin the innermost parts of the lagoon. For this reason it can beassumed that the effects of the organic loadings into the lagoonmay be spread seawards until this area (site 2). SIMPER analysisshowed that macrobenthic assemblages from this site were moreclosely related to those from adjacent areas (sea inlet e 85.08%similarity; mid-upper lagoon e 79.87% similarity), indicating theyshare characteristics of down- and upstream areas. Moreover, thisalso highlights the inexistence of abrupt and static transitions fromone assemblage to another (Ysebaert et al., 2003).

Despite the numerical dominance of deposit-feeders, the mac-robenthic richest area, located within the upper-mid lagoon andBom-Sucesso branch (sites 3 and 5), wasmore trophicallymixed. Thedominance of deposit-feeders has already been previously reportedfor the Óbidos lagoon (Carvalho et al., 2006b) and several otherestuaries and lagoon systemsworldwide (Bachelet et al., 2000;Mistriet al., 2000; Garcia-Arberas and Rallo, 2002; Ysebaert et al., 2003;Gaudêncio and Cabral, 2007; Marchini et al., 2008). The algal cover,which was higher in these areas, could also contribute to this result.The presence of macroalgae in the sediment increases habitatcomplexityand/or refuge frompredators (Valiela et al.,1997;Raffaelliet al., 1998) and represent an alternative food resource, enhancingthe establishment of herbivores and other organisms with relatedfeedingmodes (e.g. deposit-feeding/herbivory, carnivory/herbivory).Actually, it is well documented the generally higher benthic diversityand abundance within vegetated than unvegetated bottoms (e.g.Edgar et al., 1994; Mistri et al., 2000; Carvalho et al., 2006c). Mistriet al. (2001) in the Sacca di Goro brackish lagoon (Italy) founda similar pattern. The area showing highest algae biomass also

exhibited higher values of richness, diversity and evenness. Anotherstudy undertaken in the Baltic Sea showed that drifting algae canharbour extremely high densities of invertebrates that can evenexceed those recorded in seagrass meadows (Norkko et al., 2000).The preferential occurrence of bivalves and gastropods within mid-upper lagoon and Bom-Sucesso branch was also reflected in theincreasing contribution of suspension feeders and deposit-feeders/carnivores in terms of biomass, which was almost negligible usingabundance data.

The biomass of Ulva spp. in the sediment was found to be one ofthe structuring forces shaping macrobenthic communities from theÓbidos lagoon. It is known that the occurrence ofmacroalgae bloomscan be a sign of eutrophication. If nutrients are continuously addedinto a system, massive growth of macroalgae can occur and itsaccumulation and subsequent decomposition can ultimately resultin dystrophic crises with more or less negative impacts for benthicfauna (Tagliapietra et al., 1998; Norkko et al., 2000; Cardoso et al.,2004). During spring, the Bom-Sucesso area (site 5) may haveexperienced the harmful effects of huge amounts of algal cover in thesediment. This is the area with the highest water residence time(24e26 days) (Malhadas et al., 2009), enhancing the sedimentationof drifting green algae and their permanence in the sediments. Themaximum biomass of macroalgae found in this occasion concur-rently occurred with the most depressed abundance and number ofspecies. It is known that the growthof greenmacroalgae can enhancenamelymacrofaunal total biomass (Magni et al., 2006) and estuarineproduction (Dolbeth et al., 2003). However, when algal mats lay onthe substratum, it can also reduce the oxygen exchange with thewater column (Rossi, 2006) with potential occurrence of anoxia andsulphide production (Como et al., 2007). In our study, assemblagesseemed to be seriously affected by the huge amount of algae in thesediment. Only a few of the winter dominant species showed somesigns of recovery in the summer period (M. ascherusicum,H. filiformisand Hydrobia ulvae). The recovery of the gastropod is in agreementwith the findings of Norkko et al. (2000), who found that specimensof genusHydrobia showedhigh survival rates andmobility in driftingalgal mats, with most of the animals being able to reach the secondand third algal layers (higher oxygen concentration). On the otherhand,M. ascherusicum andH. filiformis are known to tolerate organicenrichment conditions (Carvalho et al., 2006a; Callier et al., 2007).Nevertheless, other taxa also known to be able to tolerate extremelyharsh environmental conditions, such as Capitella spp., did notpresent potential to recover from this disturbance event. Therefore,other factors besides the tolerance to organic enrichment must beinvolved in the recovery patterns associated with the presence ofhuge amounts of algal mats in the sediment. The disappearance ofCapitella spp. until the third sampling period (fall) cannot be relatedto its life cycle as this species was recorded in other lagoon areas.

The distribution of trophic groups along the lagoon seems toreflect the main abiotic patterns. While abundance of carnivoreswas associated with increasing salinity and therefore with the inletarea, dominated by clean sandy sediments, strictly deposit-feederswere generally spread within organically enriched sandy andmuddy areas from mid lagoon and Bom-Sucesso branch. On theother hand, deposit-feeders/suspension-feeders were positivelycorrelated to the increasing chlorophyll a and suspended particu-late matter characteristic from the Barrosa branch, therefore takingbenefit of the high primary productivity observed in this area.Deposit-feeders/herbivores responded to the decay of macroalgaemats in the sediment increasing their abundance with the higheravailability of this food resource. In a long term study undertaken inthe Venice lagoon by Pranovi et al. (2008), a shift towards thedominance of detritus feeders and herbivores linked with the over-dominance of Ulva rigida was detected and associated with eutro-phication. Omnivores (in the present case, only H. diversicolor) were

S. Carvalho et al. / Marine Environmental Research 71 (2011) 97e110108

also highly related with these two environmental parameters.H. diversicolor was only recorded within the Barrosa branch and itsdistribution cannot be related to the existence of particular feedingrequirements, as it has been reported as omnivorous, deposit-feeder and also suspension-feeder (Riisgård, 1991).

4.3. Implications for monitoring studies

Within transitional waters, where disturbance events arecommon (e.g. dredging, commercial fishing, sewage discharges,summer dystrophic crisis, hypoxia, macroalgae blooms), changes inthe ecological quality status can result from differences in thedominance of a single taxon (Munari and Mistri, 2010). Althoughnot presented, the biotic index M-AMBI (Muxika et al., 2007)showed a considerable variation of ecological status during the year.Only site 1 maintained a slightly disturbed condition, while site 2varied from undisturbed to moderately disturbed conditions.Therefore, temporal trends are fundamental to be taken intoaccount in monitoring programmes to provide accurate ecologicalstatus classifications, as it had been previously recommended forthe Italian waters (Munari and Mistri, 2010). On the other hand,resulting from the history of stress or disturbance experienced bya population or a community, physiological adaptations to newenvironmental conditions, as well as the selection of geneticallyinherited tolerance are possible to occur (Medina et al., 2007). Thismay confer resilience to the biological communities, increasingvagueness when inferring patterns on the benthic-environmentalrelationships. It is also known that benthic communities fromnaturally stressed areas may show very similar features to thosefrom anthropogenically stressed areas (Elliott and Quintino, 2007).Moreover, several species from a wide range of taxonomic groupshave been found to change their ecological behaviour in the adap-tation to brackish water conditions (Cognetti and Maltagliati, 2000and references therein). In the present study, although most of thetaxa showing positive correlations with metals and organic mattercontent in the sediment aremainly classified as indifferent, tolerant,second- and first-order opportunist species, four taxa (Rissoa spp.,Parvicardium exiguum, Iphinoe serrata, Amphipholis squamata) areclassified according to AMBI data set as sensitive (www.azti.es). It isworth noting that a positive correlation between the abundance ofa species and the concentration of a metal in the sediment per secannot be seen as a tolerant behaviour. Indeed, metals in sedimentsmay be more or less bioavailable to organisms depending on theirchemical form and environmental modifying factors (such asorganic matter) (Hansen et al., 2007). However, for most taxasignificant correlations were also observed for variables associatedwith organic enrichment. Taxa with a tolerant behaviour weremainly deposit-feeders (although not strictly), which agrees withthe summarized by Grall and Glémarec (1997). According to theseauthors, this trophic functional group mainly comprises speciesfrom ecological groups III (tolerant), IV (second-order opportunists)and V (first-order opportunists). On the other hand, species knownas tolerant (Nemertea, Lekanesphaera levii) or second-orderopportunists (Ophryotrocha dubia) were negatively correlated withmetals and/or organic carbon and nitrogen and total phosphorus insediment, suggesting a sensitive behaviour. The discrepanciesobserved for the ecological behaviours of some species support thecontroversy within the scientific community concerning thesensitivity/tolerance approach required by the Water FrameworkDirective (Munari and Mistri, 2010). Indeed, discrepancies in theecological behaviour of species were already shown to haveconsequences in the environmental status classification based,for example in the biotic index AMBI (e.g. Carvalho et al., 2006a).Thus, there is a need to repeatedly assess the nature of the species-environment relationships in dynamic systems, as they can change

when amajor physical forcing changes at a large scale (Ysebaert andHerman, 2002).

Acknowledgments

Susana Carvalho (SFRH/BPD/26986/2006) and Patrícia Pereira(SFRH/BD/17616/2004) benefit from post-doctoral and PhD grants,respectively, from the “Fundaçãopara a Ciência e a Tecnologia” (FCT).Authors would like to thank to Leandro Sampaio and Dulce Subidafor help with PERMANOVA analysis. The manuscript was greatlyimproved by the comments of two anonymous reviewers. Thisworkwas financially supported by the company “Águas do Oeste”withinthe project “Monitoring and modelling the Óbidos lagoon and theFoz do Arelho submarine outlet”. The authors also appreciate thecollaboration of MARETEC researchers in the field work.

Appendix. Supplementary material

The supplementary data associated with this article can befound in the on-line version at doi:10.1016/j.marenvres.2010.11.005

As supplementary material, the authors provide results ofANOVAs, PERMANOVAs and SIMPER analysis.

References

Afli, A., Ayari, R., Zaabi, S., 2008. Ecological quality of some Tunisian coast andlagoon locations, by using benthic community parameters and biotic indices.Estuarine, Coastal and Shelf Science 80, 269e280.

Andersen, J.M., 1976. An ignition method for determination of total phosphorus inlake sediments. Water Research 10, 329e331.

Anderson, M.J., Gorley, R.N., Clarke, K.R., 2008. PERMANOVAþ for PRIMER: Guide toStatistical Methods. PRIMER-E, Plymouth, p. 214.

Antoniadou, C., Chintiroglou, C., 2006. Trophic relationships of polychaetes asso-ciated with different algal growth forms. Helgoland Marine Research 60, 39e49.

Arias, A.M., Drake, P., 1994. Structure and production of the benthic macro-invertebrate community in a shallow lagoon in the Bay of Cádiz. Marine EcologyProgress Series 115, 151e167.

Bachelet, G., de Montaudouin, X., Auby, I., Labourg, P.-J., 2000. Seasonal changes inmacrophyte and macrozoobenthos assemblages in three coastal lagoons undervarying degrees of eutrophication. ICES Journal ofMarine Science 57,1495e1506.

Blanchet, H., de Montaudouin, X., Chardy, P., Bachelet, G., 2005. Structuring factorsand recent changes in subtidal macrozoobenthic communities of a coastallagoon, Arcachon Bay (France). Estuarine, Coastal and Shelf Science 64, 561e576.

Caetano, M., Fonseca, N., Cesário, R., Vale, C., 2007. Mobility of Pb in salt marshesrecorded by total content and stable isotopic signature. Science of the TotalEnvironment 380, 84e92.

Callier, M.D., McKindsey, C.W., Desrosiers, G., 2007. Multi-scale spatial variations inbenthic sediment geochemistry and macrofaunal communities under a sus-pended mussel culture. Marine Ecology Progress Series 348, 103e115.

Cardoso, P.G., Pardal, M.A., Raffaelli, D., Baeta, A., Marques, J.C., 2004. Macro-invertebrate response to different species of macroalgal mats and the role ofdisturbance history. Journal of Experimental Marine Biology and Ecology 308,207e220.

Carvalho, S., Barata, M., Gaspar, M.B., Pousão-Ferreira, P., Cancela da Fonseca, L.,2007. Enrichment of aquaculture earthen ponds with Hediste diversicolor:consequences for benthic dynamics and natural productivity. Aquaculture 262,227e236.

Carvalho, S., Barata, M., Pereira, F., Pousão-Ferreira, P., Cancela da Fonseca, L.,Gaspar, M.B., 2010. Can macrobenthic communities be used in the assessmentof environmental quality of fish earthen ponds? Journal of the Marine BiologicalAssociation of the U.K. 90, 135e144.

Carvalho, S., Barata, M., Gaspar, M.B., Cancela da Fonseca, L., Pousão-Ferreira, P.,2006a. Distribution patterns of macrobenthic species in relation to organicenrichment within aquaculture earthen ponds. Marine Pollution Bulletin 52,1573e1584.

Carvalho, S., Gaspar, M.B., Moura, A., Vale, C., Antunes, P., Gil, O., Cancela daFonseca, L., Falcão, M., 2006b. The use of the marine biotic index AMBI in theassessment of the ecological status of the Óbidos lagoon (Portugal). MarinePollution Bulletin 52, 1414e1424.

Carvalho, S., Moura, A., Sprung, M., 2006c. Ecological implications of removingseagrass beds (Zostera noltii) for bivalve aquaculture in southern Portugal.Cahiers de Biologie Marine 47, 321e329.

Carvalho, S., Moura, A., Gaspar, M.B., Pereira, P., Cancela da Fonseca, L., Falcão, M.,Drago, T., Leitão, F., Regala, J., 2005. Spatial and inter-annual variability of themacrobenthic communities within a coastal lagoon (Óbidos lagoon) and itsrelationship with environmental parameters. Acta Oecologica 27, 143e159.

S. Carvalho et al. / Marine Environmental Research 71 (2011) 97e110 109

Cognetti, G., Maltagliati, F., 2000. Biodiversity and adaptative mechanisms inbrackish water fauna. Marine Pollution Bulletin 40, 7e14.

Como, S., Magni, P., 2009. Temporal changes of a macrobenthic assemblage in harshlagoon sediments. Estuarine, Coastal and Shelf Science 83, 638e646.

Como, S., Magni, P., Casu, D., Floris, A., Giordani, G., Natale, S., Fenzi, G.A., Signa, G.,De Falco, G., 2007. Sediment characteristics and macrofauna distribution alonga human-modified inlet in the Gulf of Oristano (Sardinia, Italy). Marine Pollu-tion Bulletin 54, 733e744.

Dolbeth, M., Pardal, M.A., Lillebø, A.I., Azeiteiro, U., Marques, J.C., 2003. Short- andlong-term effects of eutrophication on the secondary production of an intertidalmacrobenthic community. Marine Biology 143, 1229e1238.

Dolbeth, M., Teixeira, H., Marques, J.C., Pardal, M.A., 2009. Feeding guild composi-tion of a macrobenthic subtidal community along a depth gradient. ScientiaMarina 73, 225e237.

Edgar, G.J., Shaw, C., Watson, G.F., Hammond, L.S., 1994. Comparisons of speciesrichness, size-structure and production of benthos in vegetated and unvege-tated habitats in Western Port, Victoria. Journal of Experimental Marine Biologyand Ecology 176, 201e226.

Elliott, M., Quintino, V., 2007. The Estuarine Quality Paradox, EnvironmentalHomeostasis and the difficulty of detecting anthropogenic stress in naturallystressed areas. Marine Pollution Bulletin 54, 640e645.

Gamito, 2008. Three main stressors acting on the Ria Formosa lagoonal system(Southern Portugal): physical stress, organic matter pollution and the land-ocean gradient. Estuarine, Coastal and Shelf Science 77, 710e720.

Gamito, S., Furtado, R., 2009. Feeding diversity in macroinvertebrate communities:a contribution to estimate the ecological status in shallow waters. EcologicalIndicators 9, 1009e1019.

García-Arberas, L., Rallo, A., 2002. The intertidal soft-bottom infaunal macrobenthosin three Basque estuaries (Gulf of Biscay): a feeding Guild approach. Hydro-biologia 475/476, 457e468.

Gaston, G.R., 1987. Benthic Polychaeta of the middle Atlantic Bight: feeding anddistribution. Marine Ecology Progress Series 36, 251e262.

Gaston, G.R., Rakocinski, C.F., Brown, S.S., Cleveland, L.M., 1998. Trophic function inestuaries: response of macrobenthos to natural and contaminant gradients.Marine and Freshwater Research 49, 833e846.

Gaudêncio, M.J., Cabral, H.N., 2007. Trophic structure of macrobenthos in the Tagusestuary and adjacent coastal shelf. Hydrobiologia 587, 241e251.

Grall, J., Glémarec, M., 1997. Using biotic indices to estimate macrobenthiccommunity perturbations in the Bay of Brest. Estuarine, Coastal and ShelfScience 44, 43e53.

Gray, J.S., Wu, R.S., Or, Y.Y., 2002. Effects of hypoxia and organic enrichment on thecoastal marine environment. Marine Ecology Progress Series 238, 249e279.

Hansen, P.D., Blasco, J., DelValls, T.A., Poulsen, V., van den Heuvel-Greve, M., 2007.Biological Analysis (Bioassays, Biomarkers, Biosensors). In: Barceló, D.,Petrovic, M. (Eds.), Susteinable Management of Sediment Resources e SedimentQuality and Impact Assessment of Pollutants. Elsevier, Netherlands, p. 333.

Heilskov, A.C., Holmer, M., 2001. Effects of benthic fauna on organic mattermineralization in fish-farm sediments: importance of size and abundance. ICESJournal of Marine Science 58, 427e434.

Koutsoubas, D., Dounas, C., Arvanitidis, C., Kornilios, S., Petihakis, G., Triantafyllou, G.,Eleftheriou, A., 2000. Macrobenthic community structure and disturbanceassessment in Gialova Lagoon, Ionian Sea. ICES Journal of Marine Science 57,1472e1480.

Lillebø, A.I., Neto, J.M., Flindt, M.R., Marques, J.C., Pardal, M.A., 2004. Phosphorousdynamics in a temperate intertidal estuary. Estuarine, Coastal and Shelf Science61, 101e109.

Lorenzen, C.J.,1966. Amethod for the continuousmeasurement of in vivo chlorophyllconcentration. Deep Sea Research and Oceanographic Abstracts 13, 223e227.

Luoma, S.N., Phillips, D.J.H., 1988. Distribution, variability, and impacts of traceelements in San Francisco Bay. Marine Pollution Bulletin 19, 413e425.

Magni, M., Como, S., Montani, S., Tsutsumi, H., 2006. Interlinked temporal changesin environmental conditions, chemical characteristics of sediments and mac-rofaunal assemblages in an estuarine intertidal sandflat (Seto Inland Sea, Japan).Marine Biology 149, 1185e1197.

Malhadas, M.S., Leitão, P.C., Silva, A., Neves, R., 2009. Effect of coastal waves on sealevel in Óbidos lagoon, Portugal. Continental Shelf Research 29, 1240e1250.

Mancinelli, G., Fazi, S., Rossi, L., 1998. Sediment structural properties mediatingdominant feeding types patterns in soft-bottom macrobenthos of the NorthernAdriatic Sea. Hydrobiologia 367, 211e222.

Marchini, A., Munari, C., Mistri, M., 2008. Functions and ecological status of eightItalian lagoons examined using biological traits analysis (BTA). Marine PollutionBulletin 56, 1076e1085.

Marques, J.C., Martins, I., Teles-Ferreira, C., Cruz, S., 1994. Population dynamics, lifehistory, and production of Cyathura carinata (Krøyer) (Isopoda: anthuridae) inthe Mondego estuary, Portugal. Journal of Crustacean Biology 14, 258e272.

Masero, J.A., Perez-Gonzalez, M., Basadre, M., Otero-Saavedra, M., 1999. Food supplyfor waders (Aves: Charadrii) in an estuarine area in the Bay of Cadiz (SW IberianPeninsula). Acta Oecologica 20, 429e434.

Medina, M.H., Correa, J.A., Barata, C., 2007. Micro-evolution due to pollution:possible consequences for ecosystem responses to toxic stress. Chemosphere67, 2105e2114.

Mermillod-Blondin, F., François-Carcaillet, F., Rosenberg, R., 2005. Biodiversity ofbenthic invertebrates and organic matter processing in shallow marine sedi-ments: an experimental study. Journal of Experimental Marine Biology andEcology 315, 187e209.

Mistri, M., Fano, E.A., Rossi, G., Caselli, K., Rossi, R., 2000. Variability in macro-benthos communities in the Valli di Comacchio, northern Italy, a hyper-eutrophized lagoonal ecosystem. Estuarine, Coastal and Shelf Science 51,599e611.

Mistri, M., Rossi, R., Fano, E.A., 2001. Structure and secondary production of a softbottom macrobenthic community in a brackish lagoon (Sacca di Goro, north-eastern Italy). Estuarine, Coastal and Shelf Science 52, 605e616.

Mucha, A.P., Vasconcelos, M.T.S.D., Bordalo, A.A., 2004. Vertical distribution of themacrobenthic community and its relationships to trace metals and naturalsediment characteristics in the lower Douro estuary, Portugal. Estuarine,Coastal and Shelf Science 59, 663e673.

Munari, C., Mistri, M., 2008. The performance of benthic indicators of ecologicalchange in Adriatic coastal lagoons: Throwing the baby with the water? MarinePollution Bulletin 56, 95e105.

Munari, C., Mistri, M., 2010. Towards the application of the Water FrameworkDirective in Italy: assessing the potential of benthic tools in Adriatic coastaltransitional ecosystems. Marine Pollution Bulletin 60, 1040e1050.

Munari, C., Rossi, R., Mistri, M., 2005. Temporal trends in macrobenthos communitystructure and redundancy in a shallow coastal lagoon (Valli di Comacchio,Northen Adriatic Sea). Hydrobiologia 550, 95e104.

Muxika, I., Borja, A., Bald, J., 2007. Using historical data, expert judgment andmultivariate analysis in assessing reference conditions and benthic ecologicalstatus, according to the European Water Framework Directive. Marine PollutionBulletin 55, 16e29.

Norkko, J., Bonsdorff, E., Norkko, A., 2000. Drifting algal mats as an alternativehabitat for benthic invertebrates: species specific responses to a transientresource. Journal of Experimental Marine Biology and Ecology 248, 79e104.

Nunes, M., Coelho, J.P., Cardoso, P.G., Pereira, M.E., Duarte, A.C., Pardal, M.A., 2008.The macrobenthic community along a mercury contamination in a temperateestuarine system (Ria de Aveiro, Portugal). Science of the Total Environment405, 186e194.

Pearson, T.H., Rosenberg, R., 1978. Macrobenthic succession in relation to organicenrichment and pollution of the marine environment. Oceanography andMarine Biology Annual Review 16, 229e311.

Pereira, P., de Pablo, H., Vale, C., Rosa-Santos, F., Cesário, R., 2009a. Metal andnutrient dynamics in a eutrophic coastal lagoon (Óbidos, Portugal): theimportance of observations at different time scales. Environmental Monitoringand Assessment 158, 405e418.

Pereira, P., de Pablo, H., Vale, C., Franco, V., Nogueira, M., 2009b. Spatial and seasonalvariation of water quality in an impacted coastal lagoon (Óbidos Lagoon,Portugal). Environmental Monitoring and Assessment 153, 281e292.

Pereira, P., de Pablo, H., Carvalho, S., Vale, C., Pacheco, M., 2010. Daily availability ofnutrients and metals in a eutrophic meso-tidal coastal lagoon (Óbidos lagoon,Portugal). Marine Pollution Bulletin 60, 1868e1872.

Pérez-Ruzafa, A., Fernández, A.I., Marcos, C., Gilabert, J., Quispe, J.I., García-Charton, J.A., 2005. Spatial and temporal variations of hydrological conditions,nutrients and chlorophyll a in a Mediterranean coastal lagoon (Mar Menor,Spain). Hydrobiologia 550, 11e27.

Point, D., Monperrus, M., Tessier, E., Amouroux, D., Chauvaud, L., Thouzeau, G.,Jean, F., Amice, E., Grall, J., Leynaert, A., Clavier, J., Donard, O.F.X., 2007. Biologicalcontrol of trace metal and organometal benthic fluxes in a eutrophic lagoon(Thau Lagoon, Mediterranean Sea, France). Estuarine, Coastal and Shelf Science72, 457e471.

Ponti, M., Abbiati, M., 2004. Quality assessment of transitional waters usinga benthic biotic index: the case study of the Pialassa Baiona (northern AdriaticSea). Aquatic Conservation: Marine and Freshwater Ecosystems 14, S31eS41.

Pook, C., Lewis, C., Galloway, T., 2009. The metabolic and fitness costs associatedwith metal resistance in Nereis diversicolor. Marine Pollution Bulletin 58,1063e1071.

Pranovi, F., da Ponte, F., Torricelli, P., 2008. Historical changes in the structure andfunctioning of the benthic community in the lagoon of Venice. Estuarine,Coastal and Shelf Science 76, 753e764.

Raffaelli, D.G., Raven, J.A., Poole, L.J., 1998. Ecological impact of green macroalgalblooms. Oceanography and Marine Biology: an Annual Review 36, 97e125.

Riisgård, H.U., 1991. Suspension feeding in the polychaete Nereis diversicolor. MarineEcology Progress Series 70, 29e37.

Rossi, F., 2006. Small-scale burial of macroalgal detritus in marine sediments:effects of Ulva spp. on the spatial distribution of macrofauna assemblages.Journal of Experimental Marine Biology and Ecology 332, 84e95.

Roth, S., Wilson, J.G., 1998. Functional analysis by trophic guilds of macrobenthiccommunity structure in Dublin Bay, Ireland. Journal of Experimental MarineBiology and Ecology 222, 195e217.

Snelgrove, P.V.R., Butman, C.A., 1994. Animal-sediment relationships revisited:cause versus impact effect. Oceanography and Marine Biology: an AnnualReview 32, 111e177.

Tagliapietra, D., Pavan, M., Wagner, C., 1998. Macrobenthic community changesrelated to eutrophication in Palude della Rosa (Venetian Lagoon, Italy). Estua-rine, Coastal and Shelf Science 47, 217e226.

ter Braak, C.J.F., Verdonschot, P.F.M., 1995. Canonical correspondence analysisand related multivariate methods in aquatic ecology. Aquatic Sciences 57,255e289.

Thiel, M., Kruse, I., 2001. Status of the Nemertea as predators in marine ecosystems.Hydrobiologia 456, 21e32.

UNESCO, 1981. Coastal lagoons research, present and future. UNESCO TechnicalPapers in Marine Science 32, 95.

S. Carvalho et al. / Marine Environmental Research 71 (2011) 97e110110

Valiela, I., McClelland, J., Hauxwell, J., Behr, P.J., Hersh, D., Foreman, K., 1997. Mac-roalgal blooms in shallow estuaries, controls and ecophysiological andecosystem consequences. Limnology and Oceanography 42, 1105e1118.

Verardo, D.J., Froelich, P.N., McIntyre, A., 1990. Determination of organic carbon andnitrogen in marine sediments using the Carlo Erba NA-1500 Analyzer. Deep-SeaResearch 37, 157e165.

Wägele, J.-W., Welsch, U., Müller, W., 1981. Fine structure and function of the digestivetractofCyathura carinata (Krøyer) (Crustacea, Isopoda). Zoomorphology98, 69e88.

Wieking, G., Kröncke, I., 2003. Macrofauna communities of the Dogger Bank(central North Sea) in the late 1990s: spatial distribution, species compositionand trophic structure. Helgoland Marine Research 57, 34e46.

Windom, H.L., Schropp, S.J., Calder, F.D., Ryan, J.D., Smith, R.G., Burney, L.C.,Lewis, F.G., Rawlinson, C.H., 1989. Natural trace metals concentration in estu-arine and coastal marine sediments of southeastern United States. Environ-mental Science and Technology 23, 314e320.

Ysebaert, T., Herman, P.M.J., 2002. Spatial and temporal variation in benthic mac-rofauna and relationships with environmental variables in an estuarine, inter-tidal soft-sediment environment. Marine Ecology Progress Series 244, 105e124.

Ysebaert, T., Herman, P.M.J., Meire, P., Craeymeersch, J., Verbeek, H., Heip, C.H.R.,2003. Large-scale spatial patterns in estuaries: estuarine macrobenthiccommunities in the Schelde estuary, NW Europe. Estuarine, Coastal and ShelfScience 57, 335e355.