Influence of the abiotic characteristics of sediments on the macrobenthic community structure of the

15 Pages·2014·1.17 MB·English

by  Picanco T

Limnetica,29(2):x-xx(2011)
Limnetica, 33 (1): 73-88 (2014). DOI: 10.23818/limn.33.07
(cid:13)c AsociaciónIbéricadeLimnología,Madrid.Spain.ISSN:0213-8409
Influence of the abiotic characteristics of sediments on the
macrobenthic community structure of the Minho estuary saltmarsh
(Portugal)
ThaisC. Picanço1, C. Marisa R.Almeida1, CarlosAntunes1,2,3 and Pedro A. Reis 1,∗
1 CIIMAR/CIMAR-Centro Interdisciplinar de Investigação Marinha e Ambiental, Universidade do Porto, Rua
dosBragas,289,4050-123Porto,Portugal.
2 AquamuseudoRioMinho-ParquedoCastelinho,4920-290VilaNovadeCerveira,Portugal.
3 EscolaSuperiorGallaecia-LargodasOliveiras,4920VilaNovadeCerveira,Portugal.
∗ Correspondingauthor:[email protected]
2
Received:23/10/2013 Accepted:05/02/2014
ABSTRACT
InfluenceofabioticcharacteristicsofsedimentsonthemacrobenthiccommunitystructureofMinhoestuarysaltmarsh
(Portugal)
ThisworkstudiedthespatialandseasonalvariationsofthemacrobenthiccommunitystructureoftheMinhoestuarysaltmarsh,
which involved examining the relationships between the macrobenthic community and the abiotic characteristics of the
surroundingsediments:texture,organicmattercontentandmetal(Cd,Cr,Cu,Fe,Ni,PbandZn)concentrations.Theseabiotic
characteristics showed significant (p < 0.05) spatial and seasonal variations that demonstrated the complex sedimentary
dynamicsofthissaltmarsh.Themacrobenthiccommunitystructureconsistedof37taxabelongingto5phyla:Annelida(10
taxa), Mollusca (4 taxa), Arthropoda (21 taxa), Chordata (1 taxon) and Sipuncula (1 taxon). The mean annual abundance
was1530ind/m2,andthemostabundantspecieswereCyathuracarinata,ScolelepissquamataandHedistediversicolor.The
macrobenthiccommunityshowednostandardspatialdistributionthroughoutthesaltmarsh,andspeciesabundancesshowed
highseasonalvariationsthatweredirectlydependentonthenaturalenvironmentalconditionsofeachseason.Althoughthe
Minhoestuarysaltmarshshowedevidenceofanthropogeniccontaminationbymetals,themacrobenthiccommunitywasnot
significantlyinfluencedbytheirpresence,andthemainstructuringfactorwasthetextureofthesediments.
Keywords: Macrobenthiccommunity,metal,saltmarsh,Minhoriver.
RESUMEN
Influenciadelascaracterísticasabióticasdelsedimentoenlaestructuradelacomunidadmacrobentónicadelestuariodel
RíoMinho(Portugal)
Este trabajo ha estudiado las variaciones espaciales y estacionales de la estructura de la comunidad macrobentónica del
estuario del río Miño, incluyendo el estudio de las relaciones entre la comunidad macrobentónica y las características
abióticasdelossedimentos:textura,contenidodemateriaorgánicayconcentracionesdemetales(Cd,Cr,Cu,Fe,Ni,PbyZn).
Estascaracterísticasabióticas hanmostradovariacionesespacialesyestacionalessignificativas(p < 0.05),demostrando
lascomplejasdinámicassedimentariasdeesteestuario.Laestructuradelacomunidadmacrobentónicafueconstituidapor
treintaysietetaxadecincophyla:Annelida(dieztaxa),Mollusca(cuatrotaxa),Arthropoda(veintiunataxa),Chordata(un
taxon)ySipuncula(untaxon).Lamediadelaabundanciaanualfuede1530ind/m2 ylasespeciesmásabundantesfueron
Cyathura carinata, Scolelepis squamata y Hediste diversicolor. La comunidad macrobentónica no mostró una distribución
espacial estándar a lo largo del estuario y sus abundancias mostraron elevadas variaciones estacionales directamente
dependientes de las condiciones ambientales de cada estación. A pesar de que el estuario del Miño mostró evidencias de
contaminacióndemetalesdeorigenantropogénico,lacomunidadmacrobentónicanoseviosignificativamenteafectadayel
mayorfactorestructuralfuelatexturadelossedimentos.
Palabrasclave: Comunidadmacrobentónica,metales,estuario,ríoMiño.
15293 Limnetica 33(1), pàgina 73, 15/05/2014
74 Picançoet al.
INTRODUCTION biological assessment methods and indices is
considered as a Quality Paradox (Dauvin, 2007;
Thestudyofmacrobenthiccommunitystructures Elliott&Quintino,2007).
and their dynamics hasbeenan ecological prior- The international section of the Minho River
ity,asbenthicfaunalactivitiesaffectandregulate (including its saltmarsh area) was classified as
the physicochemical and biological processes of a Natura 2000 location. The saltmarsh area is
estuarine systems (Day et al., 1989). The mac- particularly important to avifauna, about which
robenthiccommunitystructureisalsoconsidered some scientific knowledge is available (Far-
to be a useful instrument in the elaboration of inha & Trindade, 1994; Alves, 1996 and 2000;
ecological quality studies and environmental di- Gamboa, 1999). However, the composition and
agnostics,asitcanreflectwithhighprecisionthe distribution of the subtidal macrozoobenthic
previousenvironmentalconditionsoftheecosys- community present in the saltmarsh area of
tem (Warwick, 1986; Lana, 1994). This useful- the Minho Estuary remain unknown. Previous
ness canbe relatedto the presenceof macroben- work has shown the importance of sediments in
thic species near the bottom of ecosystems or in saltmarshareasassinksforcontaminantssuchas
sediments,aswellastheirlowmobility(Canfield heavy metals, and coupled with the potential of
etal.,1994;Weisbergetal.,1997;Clarke&Gor- the macrozoobenthic community to transfer this
ley, 2001). The characterizationofmacrobenthic pollution to higher trophic levels, the conditions
communitystructuresshouldincludethestudyof suggest that a biogeochemical study approach is
species abundances, diversity and evenness in- appropriate (Reis et al., 2009 and Mil-Homens
dices (Farinha & Trindade, 1994; Alves, 1996 et al., 2013a, b). Such biogeochemical studies
and 2000; Gamboa, 1999; Mucha et al., 2003). areveryscarceinPortugueseestuaries,andnone
Then, multivariate analyses canindicate the spa- have been reported in the particular case of the
tial and seasonal variations of the community singlesaltmarshexistingintheMinhoestuary.
and the influence of sediment abiotic character- Thus, the major aims of this work were
istics (e.g., texture, organic contents and pollu- to study the Minho estuary saltmarsh over a
tants such as metals) in its distribution throughout one-year period, determining the patterns of the
theecosystemduringdifferentseasons(Farinha& macrozoobenthic community composition in
Trindade, 1994; Alves, 1996 and 2000; Gamboa, relationto (i)the influence of the abiotic charac-
1999;Muchaetal.,2003;Reisetal.,2009). teristics of sediments (texture, organic contents
Estuarine saltmarsh areas are excellent nurs- and metal concentrations) and (ii) species abun-
ery and protection regions, but they can also dance,biomassanddiversity. Thesedatamaybe
accumulate high contaminant concentrations in usedtoevaluatetheimportanceofthisparticular
their sediments and plants (Teal, 1986; Vale et areaoftheestuaryforconservationpurposes.
al., 1990; Reis et al., 2009). Consequently, es-
tuarine community structures can be influenced
by geological and anthropogenic gradients of MATERIALSANDMETHODS
contamination, particularly of metals (Pearson
& Rosenberg, 1978; Rakocinski et al., 1997).
StudyArea
However, the geological contribution of met-
als complicates the identification of potential The Minho estuary is located in the northwest
sources of contamination and makes the inter- (NW) region of Portugal and includes a variety
pretation of their disturbing effects significantly of habitats with great environmental value, such
more difficult (Weisberg et al., 1997; Gaston asitssaltmarshareas(atthejunctionoftherivers
& Nasci, 1998; Mucha et al., 2003; Reis et al., Minho and Coura, near Caminha village) (Far-
2009). Furthermore, the challenge of detecting inha & Trindade, 1994; Alves, 1996 and 2000;
anthropogenic impacts in naturally stressed Gamboa, 1999). Indeed, the Minho estuary salt-
systems such as estuaries and saltmarshes using marshwasconsideredasametalpristineareaby
15293 Limnetica 33(1), pàgina 74, 15/05/2014
Changes onthe macrobioticcommunitystructureof theMinho estuarysaltmarsh 75
Reis et al. (2009), although the increase of local length and reaches the Minho estuary saltmarsh
industrial and tourism (fishing and cruising) ac- 2 km before the estuary mouth, with an annual
tivities has introduced anthropogenic sources of averageflowrateof10m3/s(Sousaetal.,2013).
metals into this ecosystem. The river Minho is We selected 10 sampling sites according to the
300kmlong,andthe70kmfurthestdownstream salinitygradientduringhightideandtheirspatial
are considered to be a natural boundary between locations (interior and exterior area) in the salt-
PortugalandSpain;theareaisusuallyreferredto marsh (Fig.1), from which sediments were col-
as the international section (Sousa et al., 2008). lectedforassessingthemacrobenthiccommunity
TheriverflowswestwardfromthenorthofSpain structures (abundances, diversity and evenness).
(Cantabrian Mountains) and discharges into the The mean distances between the sampling sites
Atlantic Ocean with an average annual flow rate were800malongtheriverCoura(sites1-4)and
of 300 m3/s (Sousa et al., 2013). The total area 230 m in the interior areas (sites 5-10), covering
of the Minho watershed is approx. 17100 km2, atotalsaltmarshareaof1.04km2.Sampleswere
but only 23 km2 are estuarine area (Sousa et al., also collected at these sites to assess the abiotic
2008). The Minho estuary is part of a Natura characteristicsoftheirwaters(nearbottom:tem-
2000site,whichincludestheentireinternational perature,dissolvedoxygenandsalinity)andsed-
section of the river (Sousa et al., 2008). Addi- iments (texture, organic contents and metal con-
tionally, the Coura River extends over 10 km in centrations).
Figure1. Locationsofthe10samplingsitesintheMinhoestuarysaltmarsh(Portugal),nearCaminhavillage(adaptedfromReiset
al.,2009).LocalizacióndelosdiezpuntosdemuestreoenelestuariodelríoMiño(Portugal),cercadelavilladeCamiña(adaptado
deReisetal.,2009).
15293 Limnetica 33(1), pàgina 75, 15/05/2014
76 Picançoet al.
Reagentsandmaterials tions were determined by Atomic Absorption
Spectrometry (SpectrAA 220 FS, Varian), cou-
The reagents and materials used in this study
pled with a deuterium lamp as a background
have been previously described by Reis et al.
corrector,usingflameatomization(Marck7,Var-
(2009): (i) the concentrated nitric acid (Fluka,
ian) and electrothermal atomization (GTA 110,
proanalysis,withoutfurtherpurification)andthe
Varian), depending on the metal concentrations
remaining reagents were of pro analysis level;
in the samples (Reis et al., 2009). An adequate
(ii)ultrapurewater(Milli-Qlevel,MilliporeSys-
approach to study the potential anthropogenic
tems)wasusedtoprepareallsolutions;(iii)Stan-
contamination of sediments by metals is the
dard Reference Material certified for “Inorgan-
normalization of these elements using a refer-
icsinMarineSediment”(SRM2702,NIST)was
ence element not associated with contamination,
usedtoverifythesuitabilityofthedigestionpro-
such as Al, Li or Fe (Schiff & Weisberg, 1999;
cedure and of the optimized analytical method
Muchaetal.,2003;Reisetal.,2009).Thestudy
for the metal analyses in the sediments; and (iv)
of Reis et al. (2009) used Fe as a conservative
thematerialusedinthesamplingcollectionsand
indicator for the following reasons: (i) Fe is the
treatments had been previously decontaminated
fourth-most-abundant metal on earth (with a
ina20%(v/v)nitricacidsolution.
mean concentration in superficial terrestrial sed-
iments of 3.5%); (ii) normally, anthropogenic
sources of Fe are scarce compared with natural
Samplingstrategyandanalyticalmethods
Fe concentrations; and (iii) the ratios between
Independent sediment replicates (n = 4) were other metals and Fe are nearly constant in ter-
collectedusingaVanVeengrab(areaof500cm2 restrial sediments (Velinsky et al., 1994). Reis
and a maximum capacity of 5000 cm3) at each et al. (2009) showed that some interior areas of
site in September 2005 (summer), December this saltmarsh had evidence of anthropogenic
2005 (autumn) and March 2006 (winter) for contaminationbymetals(Cr,Cu,NiandPb).
abioticandbioticcharacterization. Forbioticcharacterization,thesedimentsam-
Theanalyticalmethodsusedtostudytheabiotic pleswerefixedwithabufferedseawater-formalin
characteristics (texture, organic matter contents solution (10%, v/v) and sieved through a 1 mm
and metal concentrations) of the sediments have meshfortheseparationofmacrobenthicorganisms.
been previously described by Reis et al (2009). Then, the samples were preserved in an ethanol
Fortexturecharacterization, thesedimentsamples solution (70%, v/v) with Rose Bengal (as stain-
were dried in an oven at 60◦C for 48 hours, ing agent), and the organisms were counted and
and dimensional analyses were conducted using a identified to the lowest possible taxon, normally
Ro-Tap sieves system. The weight of each class thespecieslevel(Gaston&Nasci,1998).
(gravel:>2mm;verycoarsesand:1-2mm;coarse
sand:0.500-1mm;mediumsand:0.250-0.500mm;
Dataanalyses
fine sand: 0.125-0.250 mm; very fine sand:
<0.125 mm; and clay and silts: <0.063 mm) Individual species abundance and biomass were
was expressed as a percentage (%) of total expressed per square metre. Measures included
weight. The organic matter content was deter- abundance, biomass, number of species (S),
mined after combustion of the sediment samples Shannon-Wiener diversity index (H′) and Pie-
inafurnaceat550◦Cfor24hours,andthevalues lou’s evenness (J′) index. Principal Component
were expressed as percentages (%) relative to Analysis(PCA)wasusedtodetecthabitatdiffer-
theinitialsampleweight.Themetal(Cd,Cr,Cu, ences based on the abiotic data and to establish
Fe,Ni,PbandZn)analyseshavebeendescribed correlations between biological parameters and
by Reis et al. (2009): digestion in Teflon vessels abiotic characteristics; the indices of abiotic and
(model 4782, Parr) in a microwave system bioticsimilaritywerecomparedusingBIO-ENV
(model 440, Panasonic). The metal concentra- (usingtheSpearmancoefficient)(Clarke&War-
15293 Limnetica 33(1), pàgina 76, 15/05/2014
Changes onthe macrobioticcommunitystructureof theMinho estuarysaltmarsh 77
wick,1994). For statistical analyses of the biotic ganic matter contents and metal concentrations
values,clustermultivariableanalysesallowedfor in the sediments), the following sequence of
thestudyofthespatialandseasonalvariationsof stepswasconducted:(i)thenormalityofthedata
species distributions (using SPSS software). For was checked by the Shapiro-Wilk test, consider-
the statistical analyses of the abiotic values (or- ing one level of significance (p < 0.05), using
Table1. Thephysicochemicalparametersofthewaters,aswellasthetextureandorganicmattercontentsofthesediments,of
theMinhoestuarysaltmarshobtainedforthethreesamplingdates.Temperature(T,◦C),dissolvedoxygen(DO,mg·L–1),salinity
(S,psu),gravel(G,%),varycoarsesand(VCS,%),coarsesand(CS,%),mediumsand(MS,%),finesand(FS,%),veryfinesand
(VFS,%),silt+clay(S+C,%)andorganicmatter(OM,%).Parámetrosfísico-químicosdelagua,materiaorgánicaytexturade
lossedimentosenelestuariodelríoMiño,obtenidosalolargodelostresmuestreos.Temperatura(T,◦C),oxígenodisuelto(DO,
mg·L–1),salinidad(S,psu),grava(G,%),arenamuygruesa(VCS,%),arenagruesa(CS,%),arenamedia(MS,%),arenafina(FS,
%),arenamuyfina(VFS,%),limo+arcilla(S+C,%)ymateriaorgánica(OM,%).
Summer
SamplingSite 1 2 3 4 5 6 7 8 9 10
T 14.2 16.0 19.2 14.3 14.9 15.4 15.9 17.2 15.7 17.6
DO 9.0 10.0 9.5 8.3 8.2 8.4 8.0 8.2 8.2 7.5
S 34.4 29.4 16.9 33.5 33.4 32.0 31.0 29.0 31.0 24.7
G 2.4 38.6 60.9 21.9 4.1 51.9 8.7 4.1 0.1 5.0
VCS 7.8 35.5 22.2 29.4 9.9 16.7 10.3 8.2 0.5 8.0
CS 34.4 20.7 13.7 23.9 24.3 15.9 27.1 26.3 9.7 8.5
MS 20.6 4.1 2.5 21.5 19.6 12.9 39.7 35.8 27.1 29.9
FS 19.3 0.7 0.4 2.2 11.5 0.9 6.3 13.9 23.6 10.3
VFS 13.6 0.2 0.1 0.6 15.5 0.2 4.2 5.2 18.3 1.5
S+C 2.0 0.2 0.2 0.5 15.1 1.3 3.6 6.5 20.6 36.9
OM 3.0 1.2 1.2 1.2 10.0 4.4 2.1 4.0 8.0 2.8
Autumn
T 13.4 9.9 10.7 12.1 9.0 8.7 13.0 11.6 9.1 8.7
DO 7.0 11.0 9.9 11.1 10.8 9.8 9.5 7.0 7.6 7.4
S 33.5 0.5 0.0 26.0 5.0 7.5 31.8 25.0 4.4 1.9
G 8.1 77.0 3.6 38.7 11.6 5.9 16.6 4.6 0.8 0.9
VCS 24.9 9.0 11.8 25.0 14.0 15.0 26.0 15.4 1.0 4.5
CS 49.3 3.0 60.6 16.6 20.4 25.2 25.8 18.8 3.0 20.2
MS 10.5 0.0 19.9 10.5 36.2 30.9 18.2 23.0 8.8 44.0
FS 4.1 1.0 2.7 4.2 10.7 12.8 7.9 17.8 35.2 18.5
VFS 2.3 5.0 1.0 2.2 3.5 6.2 3.8 7.5 35.0 6.8
S+C 0.8 5.0 0.4 2.8 3.7 4.1 1.6 13.0 16.2 4.9
OM 1.7 1.4 1.3 2.7 3.3 6.9 1.9 5.2 11.2 8.2
Winter
T 13.2 12.3 12.0 11.7 12.8 12.9 13.1 12.5 11.7 12.4
DO 9.1 10.8 10.8 11.0 10.9 11.0 9.0 9.6 11.5 11.1
S 32.8 0.1 0.0 3.6 0.3 0.8 32.6 25.0 1.1 0.6
G 70.3 81.8 9.9 38.3 1.6 9.7 15.1 7.0 0.2 4.9
VCS 15.6 9.8 46.4 33.6 4.6 7.9 21.0 10.7 1.5 6.2
CS 10.8 6.0 39.4 18.1 7.9 17.7 22.3 21.8 19.6 10.7
MS 1.9 1.3 3.8 8.1 15.5 23.6 19.8 38.3 44.8 49.8
FS 0.5 0.4 0.2 1.3 22.9 16.9 15.5 12.4 16.9 20.0
VFS 0.5 0.3 0.2 0.3 29.6 13.0 4.6 4.7 9.4 4.8
S+C 0.4 0.4 0.2 0.3 18.0 11.3 1.6 5.1 7.5 3.6
OM 1.3 1.5 1.1 1.2 11.3 11.0 1.5 3.8 5.1 2.2
15293 Limnetica 33(1), pàgina 77, 15/05/2014
78 Picançoet al.
SPSS software; (ii) because some values failed (ii) very fine sand (<0.125 mm) and clay and
the normality tests, all data were logarithmically silts (<0.063 mm) fractions dominated at
(base 10) transformed to reduce deviations from site5(interiorsaltmarsh);
the normal distribution; (iii) the homogeneity (iii) fine sand fraction (0.125-0.250 mm) domi-
of variances was checked by the Cochran test, nated at sites 6, 8, 9 and 10 (medium salt-
consideringonelevelofsignificance(p < 0.05), marsh);
using WinGMAv 5 software (EICC, University (iv) site 7 (interior saltmarsh) showed high sea-
of Sydney); (iv) two-way analyses of variance sonalvariation,withtheveryfinesand,clay
(ANOVA) were used to identify significant spa- and silt fractions dominant during summer
tial and seasonal differences (p < 0.05) using and the gravel and coarse sand fractions
WinGMAv5software(EICC,UniversityofSyd- dominant during the autumn and winter.
ney); and (v) unplanned comparisons (post hoc This result may be due to the higher rivers
tests) were conducted to establish groups of flows during autumn and winter, which
sampling sites and seasons which differed signi- could transport the finer sediments from
ficantly (p < 0.05) using the Student-Newman- this site to adjacent protected areas (sites
Keuls (SNK) test for ANOVAs from WinGMAv 5-6and8-10).
5software(EICC,UniversityofSydney).
Thesesedimenttexturesweresimilartothose
ofotherEuropeanestuaries:coarsersedimentsin
RESULTSANDDISCUSSION the river areas (mainly in the Coura River: lo-
Environmentalanalyses cations 1-4) and finer sediments in the protected
interior areas (Diez, 1980; Mora, 1980; Asensio
Physicochemical parameters of waters and the
& Gómez, 1984). Normally, these interior areas
textureandorganicmattercontentsofsediments
(locations 5-10) can retain finer sediments and
havehigherfloralbiomasses,whichcontributeto
The physicochemical parameters of the waters
the formation of natural barriers that slow down
weredirectlyinfluencedbythetypicalcharacter-
water flows and accumulate high concentrations
istics of each season and tide period: (i) higher
of metals (Diez, 1980; Mora, 1980; Asensio &
temperatures and salinities during summer and
Gómez,1984).
at sampling sites more exposed to marine intru-
The saltmarsh areas with the finer sediments
sion during high tide and (ii) lower temperatures
corresponded to the areas with the highest or-
andsalinitiesduringwinterandatsitesmoreex-
ganic matter contents (Table 1). Normally, these
posed to fresh waters from the Coura River (Ta-
areasalsohaveahigherability toretaincontam-
ble1).Thedissolvedoxygenconcentrationswere
alwayshigherthan7.0mg·L−1 forthethreesam- inants in chemical forms that are more available
toorganisms,suchasmetals(Chapman&Wang,
plingdates,whichindicatedoptimumconcentra-
tions(DO≥6.0mg·L−1at15◦C)andwell-mixed 2001).Asexpected,organicmattercontentswere
highest in the sediments of site 5, lowest at sites
body waters (Reis et al., 2009). A number of
1-4 and intermediate at sites 6 and 8-10 during
sampling sites (i.e., sites 2-6 during winter) had
allseasons.Onlythesedimentsofsite7suffered
saturateddissolvedoxygenconcentrations(DO≥
10.0 mg·L−1 at 15◦C), suggesting excellent eco- a high reduction of organic matter contents from
summer to autumn and winter, which coincided
logicalqualities(Reisetal.,2009).
withthechangeoftexture.
The textures of the sediments were constant
acrossthesaltmarshduringallseasons(exceptat
site7): Heavymetalconcentrationsinsediments
(i) gravel (>2 mm) and very coarse sand (1-2 The metal (Cd, Cr, Cu, Fe, Ni, Pb and Zn) con-
mm) fractions dominated at sites 1, 2, 3 and centrations in the sediments of the Minho estu-
4(CouraRivermainstream); arysaltmarshshowedsignificantspatialandsea-
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Changes onthe macrobioticcommunitystructureof theMinho estuarysaltmarsh 79
sonal variations (Fig. 2 and Table 2). Detailed ples,digestionwithonlyconcentratednitricacid
measurements of metal concentrations obtained is indicative of metal levels that are more envi-
in September 2005 (summer) can be found in ronmentallybioavailableandhavehigherecotox-
Reisetal.(2009). icologicalpotential(EPA,1994).
The limits of detection were calculated ac- The ANOVAs of the metal concentrations re-
cording to the APHA recommendations (Sedi- sulted in three significantly (p < 0.05) different
ments(mg·kg−1,drywt):Cd:0.0041;Cr:5.0;Cu: clusters ofsampling sites: (i)GroupAwithhigh
0.046; Fe (%): 0.25; Mn: 4.1; Pb: 0.099 and Zn: metal concentrations, which included sites 5, 7
9.1) (APHA, 1998; Reis et al., 2009). The anal- and 9; Group B with intermediate metal concen-
yses of the SRM 2702 showed acceptable mean trations, which included sites 1, 6, 8 and 10; and
recoveriesforallofthemetals:Cd(117.6%),Cr Group C with low metal concentrations, which
(75.4%),Cu(89.3%),Fe(83.1%),Pb(94.2%) included sites 2, 3 and 4 (Fig.2). These spatial
and Zn (92.5%), except for Ni (70.5%). Al- distributions weredirectly influencedby the nat-
though the digestion procedure did not allow for uralcharacteristicsofthesedimentsofeachsam-
the complete dissolution of the sediment sam- pling site at eachseason, as the sites with higher
Table2. Two-wayanalysesofvariance(ANOVAs)ofmetal(Cd,Cr,Cu,Fe,Ni,PbandZn)concentrationsinthesedimentsof
Minhoestuarysaltmarshobtainedforthethreesamplingdates,whichallowedfortheidentificationofsignificantspatialandseasonal
differences(p < 0.05)usingWinGMAv5software(EICC,UniversityofSydney).Ineachseason,differentlettersshowssignificant
spatial differences (p < 0.05): increasing order of concentrations is A<B<C, etc. In each location, different numbers shows
significant temporal differences(p < 0.05): increasing order ofconcentrations is 1<2<3,etc. Análisis de varianza de dos vías
(ANOVA)delasconcentracionesdemetales(Cd,Cr,Cu,Fe,Ni,PbyZn)delossedimentosdelestuariodelríoMiño,obtenidosalo
largodelostresmuestreosrealizados,elcualhapermitidoidentificardiferenciasespacialesyestacionalessignificativas(p < 0.05):
elordendeconcentracionescrecientesesA<B<C,etc.Encadapuntodemuestreo,losdiferentesnúmerosmuestrandiferencias
temporalessignificativas(p < 0.05):elordendeconcentracionescrecienteses1<2<3,etc.
ANOVASofmetalconcentrationsinsedimentsofMinhoestuarysaltmarsh
Metal SamplingSeason 1 2 3 4 5 6 7 8 9 10
Summer D,E,2 A,1 B,1 B,C,2 F,1 E,1 F,2 D,E,2 F,2 C,D,1
Cd Autumn B,2 B,3 B,1 B,2 D,1 C,1 A,1 B,1 E,3 B,C,1
Winter A,B,1 A,B,2 B,1 A,1 D,1 C,1 B,1 C,1,2 C,D,1 C,1
Summer A,B,1 A,B,1 A,1 A,1 D,1 B,C,1 D,3 D,3 C,D,1 B,1
Cr Autumn A,B,1 A,B,1 A,1 A,B,1 C,1 A,B,1 A,B,1 A,B,1 C,1 B,C,1
Winter B,2 B,2 A,1 A,1 D,2 C,2 C,2 B,C,2 B,C,1 B,C,2
Summer B,2 B,1 B,1 A,1 D,1 C,1 D,2 C,1 D,2 B,1
Cu Autumn A,1 D,2 B,C,D,1 A,B,C,2 E,1 D,1 A,B,1 C,D,1 F,3 D,2
Winter B,C,D,2 B,C,1 B,1 A,1 F,2 C,D,E,1 D,1 E,1 E,1 D,E,2
Summer A,1 A,1 A,1 A,1 D,1 B,2 C,2 B,2 C,2 B,2
Pb Autumn A,1 A,1,2 A,3 B,2 D,1 C,2 A,1 A,1 E,3 A,1
Winter D,2 B,C,D,2 B,C,D,2 A,B,1 E,2 A,1 B,C,D,1 C,D,1,2 A,B,C,1 A,B,C,1
Summer B,2 A,1 A,1 A,2 E,1 D,1 F,3 D,1 E,2 B,C,1
Ni Autumn A,1 A,B,1 A,1 A,B,2 D,1 C,D,1 B,1 C,D,1 E,2 D,2
Winter B,2 B,2 A,1 A,1 E,2 C,D,1 C,2 C,D,1 D,1 C,D,2
Summer A,B,C,1 A,B,C,1 A,B,1 A,1 E,1 C,D,1 D,E,2 C,D,1 E,2 B,1
Zn Autumn A,1 A,B,1 A,B,1 A,1 C,D,1 A,B,1 A,B,1 A,B,1 D,2 B,C,2
Winter B,1 B,1 B,1 A,1 C,1 B,1 B,1 B,1 B,1 B,1
Summer A,B,1,2 B,C,1 A,1 A,1 E,1 D,1 E,2 B,C,D,1 F,2 C,D,1
Fe Autumn A,1 B,1 B,2 A,1 D,1 B,C,1 B,1 B,1 E,3 C,1
Winter B,C,2 B,C,1 B,1 A,1 E,2 D,1 B,C,1 B,C,1 E,1 C,1
15293 Limnetica 33(1), pàgina 79, 15/05/2014
80 Picançoet al.
metal concentrations had finer sediments and performed these normalizations in the sediments
higher organic matter contents. This observation oftheMinhoestuarysaltmarshandrevealedthat
was corroborated by the seasonal variations of sites 5 and 7 (interior saltmarsh areas) showed
metal concentrations (Fig. 2 and Table 2: differ- evidence of anthropogenic contamination by
ent numbers represent significant seasonal vari- Cr, Cu, Ni and Pb during summer (minimum
ations in each location), which also coincided flows and metal dilution factors), but only site
with the variations of texture and organic matter 5 continued to show that contamination during
contentsbetweenseasons.Forexample,thesedi- winter (maximum flows and metal dilution
ments of site 7 showed a great reduction of metal factors). These results suggest that the metal
concentrations from summer to winter, whichco- concentrations obtained in the sediments of the
incidedwiththereductionoftheirveryfinesand, Minho estuary saltmarsh were not exclusively
clayandsiltfractionsandorganicmatter contents. derived from natural sources, and these anthro-
The geological characteristics of the sedi- pogeniccontributionsmighthavealsoinfluenced
mentscomplicatethedistinctionbetweennatural the macrobenthic community structure of this
and anthropogenic sources of organic and in- saltmarsh. However, comparisons with other
organic contaminants. An adequate approach nationalwetlands have shown that the sediments
to distinguish organic from inorganic contami- of Minho estuary saltmarsh have much lower
nation and natural from anthropogenic sources metal concentrations, being similar only to Ria
is the normalization of vestigial metals using a Formosa(asummarytableofmetalconcentrations
macroelementsuchasAl,LiorFe(Muchaetal., inthesuperficialsedimentsofdifferentPortuguese
2003;Reisetal.,2009).Reisetal.(2009)already wetlandscanbefoundinReis etal.(2009).
Cd Ni
400 30,0
Conc (µg/kg) 123000000 Conc (mg/kg) 12527,,,055
0 0,0
1 2 3 4 5Cr 6 7 8 9 10 1 2 3 4 5Pb 6 7 8 9 10
40,0 30,0
Conc (mg/kg) 123000,,,000 Conc (mg/kg) 12527,,,055
0,0 0,0
40,0 1 2 3 4 5Cu 6 7 8 9 10 120,0 1 2 3 4 5Zn 6 7 8 9 10
Conc (mg/kg) 123000,,,000 Conc (mg/kg) 369000,,,000
0,0 0,0
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
6,0 Fe SamplingSite
Summer Autumn Winter
%) 4,5
Conc ( 3,0
1,5
0,0
1 2 3 4 5 6 7 8 9 10
SamplingSite
Summer Autumn Winter
Figure2. Metalconcentrations(Cd,Cr,Cu,Fe,Ni,PbandZn)ofthesedimentscollectedfromeachsamplingsiteduringeach
sampling trip. Concentración de metales (Cd, Cr, Cu, Fe, Ni, Pb y Zn) en los sedimentos recogidos en cada punto de muestreo,
durantecadamuestreo.
15293 Limnetica 33(1), pàgina 80, 15/05/2014
Changes onthe macrobioticcommunitystructureof theMinho estuarysaltmarsh 81
Biologicalanalyses (95.0ind/m2 of3differentspecies)wasobtained
at site 10 (intermediate saltmarsh) during win-
ter(severehydrodynamicconditions,withatotal
MacrozoobenthosAbundance,Diversity
meanabundanceof744.0ind/m2);thisresultcan
andEvenness
be directly related to the typical life cycle of the
In the Minho estuary saltmarsh, a total of 10 benthicspeciesintheMinhoestuary,whichhave
185 individuals were identified during the three their optimum recruitment periods during sum-
sampling dates, distributed across 5 phyla and mer (Sousa et al., 2008). The sediments of site
37 taxa: Annelida (10 taxa), Mollusca (4 taxa), 10 were dominated by the fine sand fraction and
Arthropoda(21taxa),Chordata(1taxon)andSi- had medium organic matter content, with no ev-
puncula (1 taxon) (Appendix 1, available: www. idence of anthropogenic contamination by met-
limnetica.net/internet). als. Indeed, two sampling sites (4 and 10) con-
The mean annual abundance (per area unit) sidered to be uncontaminated by metals showed
of the three sampling dates was 1530 ind/m2. completelydifferenttotalabundances.Thisresult
The highest total abundance (6330 ind/m2 of suggested that macrobenthic community struc-
nine different species) was observed at site 4 ture was more dependent on the texture and or-
(Coura River mainstream) during summer (the ganicmattercontentstypicalofeachseasonthan
peak of the macrobenthic recruitment season, onmetalconcentrations.
with a total mean abundance of 1977.5 ind/m2). Thespeciesdiversityofthissaltmarshshowed
Site 4 presented sediments dominated by gravel no consistent pattern among the different sam-
and very coarse sand, low organic matter con- plingsitesandseasons(Appendix1,www.limne-
tents and minimum metal concentrations, which tica.net/internetandTable3).However,thegreat-
might represent an ideal uncontaminated area est number of different species of macrobenthos
to macrobenthos. The lowest total abundance was observed in the Coura River mainstream
Table 3. Values of species number (S), Shannon-Wienerdiversity index (log H′) and evennessindex (J′) of the Minho estuary
saltmarshobtainedforthethreesamplingdates.Valoresdelnúmerodeespecies(S),índicedediversidaddeShannon-Weaver(logH′)
eíndicedehomogeneidad(J′)delestuariodelríoMiñoalolargodelostresmuestreos.
NumberofSpecies(S)
SamplingSite 1 2 3 4 5 6 7 8 9 10
Summer 13 10 14 9 13 11 9 8 6 10
Autumn 10 13 17 11 11 7 9 8 6 5
Winter 13 14 14 8 9 6 7 11 6 3
Shannon-WeaverDiversityIndex(logH′)
SamplingSite 1 2 3 4 5 6 7 8 9 10
Summer 1.40 1.50 1.71 1.61 1.37 1.27 1.50 1.71 1.01 1.51
Autumn 1.79 1.82 1.70 1.23 1.18 1.55 1.33 1.47 0.84 1.10
Winter 1.25 1.25 1.94 1.11 1.52 1.48 1.34 1.87 0.79 0.91
EvennessIndex(J′)
SamplingSite 1 2 3 4 5 6 7 8 9 10
Summer 0.55 0.65 0.65 0.73 0.53 0.53 0.68 0.82 0.56 0.66
Autumn 0.78 0.71 0.60 0.51 0.49 0.79 0.61 0.71 0.47 0.69
Winter 0.49 0.47 0.74 0.53 0.69 0.83 0.69 0.78 0.44 0.83
15293 Limnetica 33(1), pàgina 81, 21/05/2014
82 Picançoet al.
(sites 1-3) during all seasons, particularly at site the Shannon-Wiener diversity indices, the rel-
3,whichhad17differentspeciesduringautumn. ative species abundance should be assessed by
The remaining sites 5-10 showed only a few evenness indices (Table 3). These evenness in-
different species and had low Shannon-Wiener dices (0 ≤ J′ ≤ 1) were at their maximum and
diversity indices, especially site 10, which had minimum,respectively,insite10(J′ = 0.83)and
only 3 different species during winter. Once site9(J′ = 0.44)duringwinter.Highervaluesof
more, this result suggested that the texture and evenness indicate a more homogeneous commu-
organic matter contents of the sediments were nitystructureandlessdiversity. Thus,thehigher
themainstructuringfactorsofthismacrobenthic evenness values of the interior saltmarsh areas
community. (sites6,8and10)indicatedthattheseareaswere
Althoughthespeciesrichnessofthesaltmarsh lessadaptedtosevereecologicalchanges.There-
can be estimated by the number of species and maining sites (1-5 and 7) showed intermediate
Table4. ClusterMultivariableAnalysis:meansimilaritybetweengroups,totalabundanceanddominantspeciesperfaunalgroup.
The group G was established without a mean similarity or species dominance. Numbers represent the sampling sites (1-10),
1
andletters representthesampling seasons(S-Summer;A-Autumn;W-Winter). BIO-ENV analysisofthe abiotic factors(texture,
organicmattercontentsandmetalconcentrations)ofthesedimentsoftheMinhoestuarysaltmarshobtainedforthethreesampling
dates.Análisisdeagrupamientomultivariante:similaridadmediaentregrupos,abundanciatotalyespeciesdominantesporgrupo
faunístico.ElgrupoG fueestablecidoensimilitudmediaoespeciedominante.Losnúmerosrepresentanpuntosdemuestreo(1-10)
1
ylasletrasrepresentanépocasdemuestreo(S-verano;A-otoño;W-invierno).AnálisisBIOENVdelosfactoresabióticos(textura,
materiaorgánicayconcentracionesdemetales)delossedimentosdelestuariodelríoMiñoalolargodelostresmuestreos.
Faunistic CLUSTERANALYSIS
Group Site-Season MeanSimilarity TotalAbundance SpeciesDominance Contribution TotalContribution
(%) (%) (%) (%)
GroupG 10-W — 2.39 — — —
1
2-S/A/W Cyathuracarinata 44.68
3-S/A/W
GroupG 34.47 41.29 59.14
2
4-A Corophiumsp. 14.46
10-S
5-S/A Scolelepissquamata 32,37
6-S/A/W
GroupG 36.78 31.32 63.69
3
8-S/A/W Alkmariaromijni 31.32
10-A
1-S/A/W Hedistediversicolor 59.57
4-S/W
GroupG 39.86 25.00 82.60
4 5-W
Scolelepissquamata 23.03
7-S/A/W
9-S/A/W
Numberof
BIOENVANALYSIS-BESTVARIABLESCOMBINATION
Variables
0.311 0.261 0.249
1 FineSand OrganicMatter MedianSand
(0.125-0.250mm) (MO) (0.250-0.500mm)
0.350 0.346 0.331
2 FineSand+CoarseSand FineSand+OrganicMatter MedianSand+OrganicMatter
(0.125-0.250/0.500-1mm) (0.125-0.250mm+MO) (0.250-0.500mm+MO)
0.382 0.379
0.363
FineSand+CoarseSand+ MedianSand+CoarseSand+
3 FineSand+MedianSand+CoarseSand
OrganicMatter OrganicMatter
(0.125-1mm)
(0.125-0.250/0.500-1mm+MO) (0.250-1mm+MO)
15293 Limnetica 33(1), pàgina 82, 15/05/2014