1、Spatial and seasonal variations in copepod communities related to turbidity maximum along the Chikugo estuarine gradient in the upper Ariake Bay,Japan日本有明海上部的沿筑後川海口梯度的最大濁度在空間和季節橈足類群落變日本有明海上部的沿筑後川海口梯度的最大濁度在空間和季節橈足類群落變異異Md.Shahidul IslamHiroshi UedaMasaru Tanaka報告者：闕禎儀報告者：闕禎儀I N T R O D U C T I O Nmar
2、ine food chainsThe estuarine turbidity maximum(ETM)is a ubiquitous feature in dynamic estuarine ecosystems with substantial impacts on copepod abundance and distribution.Rothschild and Osborn,1988Gasparini et al.,1999Roman et al.,2001Winkler et al.,2003Turbidity Planktonic predators encounter more p
3、rey Hydrodynamic conditions also result in high abundance and biomass of copepods in ETM.MacKenzie et al.,1994MacKenzie and Kirboe,2000Visser et al.,2001David et al.,2005ETM zones are resided by copepods with low salinity tolerance.Roman et al.,2001;Winkler et al.,2003ETM zones are characterized by
4、low copepod diversity that is generally unique and different from that of upstream freshwater and downstream communities.Laprise and Dodson,1994;Roman et al.,2001;Winkler et al.,2003Estuarine copepod communities are believed to be annually stable but show strong seasonal and spatial dynamics.Tempera
5、ture,salinity,and food supply are among the most important factors that influence the observed spatial and seasonal patterns in demographic variations of copepods.Winkler et al.,2003Roddie et al.,1984;Hassel,1986JapanKyushuRoman et al.,2001Laprise and Dodson,1994;Winkler et al.,2003Kimmerer et al.,1
6、998Irigoien and Castel,1997;David et al.,2005 Chesapeake Bay St.Lawrence estuary San Francisco Bay Gironde estuaryM a t e r I a l sA n dM e t h o d sDATE:2004.4 2005.3Fig.1 Map of the Ariake Bay and the hikugo River estuary showing the sampling stations.Environmental Monitoring System(YSI 650 MDS,YS
7、I Incorporated,USA)Temperature(C)Turbidity(nephelometric turbidity unit,NTU)Salinity(practical salinity unit,PSU)chlorophyll-a(chl-a,g l-1)Phaeopigment(PhP,g l-1)Hydrographic data collectionZooplankton collectionOblique towsPlankton net(45 cm mouth diameter and 0.1 mm mesh size)equipped with a flow
8、meter10%seawater formalinShannone Wiener index(H)Two-way analysis of variance(ANOVA)copepod speciesdiversityspatial and temporaldifferencesR e s u l t s Hydrographic environmentFig.2 Spatial and temporal variations in the hydrographical variables along the hikugo estuary;values are mean(SD)and P val
9、ues indicate the results of ANOVA.TemperatureSalinityTurbidityChl-aPhPDensityBiomassSalinity 0.12Turbidity-0.22*-0.42*Chl-a 0.50*-0.08 0.25*PhP-0.07-0.49*0.68*0.43*Density 0.43*0.08 0.13 0.60*0.22*Biomass 0.26*-0.19 0.39*0.69*0.45*0.82*H 0.45*0.27*-0.20 0.04-0.20-0.14-0.16Table 1Pearsons correlation
10、 coefficient between different hydrographical variables,pigments and copepod density,diversity and biomass collected over the spatiotemporal scales from the Chikugo estuary(*P 0.05;*P 0.01)Fig.3 Spatial variations in PhP:TP ratio along the Chikugo estuary(values are mean SD);TP is total pigment(chlo
11、rophyll-a+phaeopigment);P value indicates the results of ANOVA.31.28415.33Oithona davisae25.52338.96Sinocalanus sinensis12.81170.06Paracalanus parvus6.6187.78Cyclopoida spp.5.9979.61Acartia omorii5.9078.35Pseudodiapomus inopinus2.6635.27Pseudodiaptomus marinus2.4332.34Copepodite1.8724.88Acartia eryt
12、hraea1.5120.08Acartia pacifica0.75 9.92Nauplii0.74 9.79Euterpina acutifrons0.38 5.11Centropages abdominalis0.34 4.54Hemicyclops japonicus0.34 4.50Unidentified0.31 4.14Paraclanus crassirostris0.27 3.64Sinocalanus tenellus0.07 0.91Centropages tenuiremis0.06 0.78Calanus sinicus0.05 0.69Trotanus derjugi
13、ni0.04 0.54Microsetella sp.0.03 0.44Labidocera rotunda0.02 0.21Temora turbinata0.01 0.17Eurytemora pacifica0.00 0.04Centropages gracilisDensity (number 103 m-3)%TatalSpeciesTable 2-1Contribution of each species to the overall density and biomass of copepods collected over a period of twelve months a
14、long the Chikugo estuary;species are arranged in order of abundanceCopepod community structure,density,biomass and diversity44.601825.98Sinocalanus sinensis12.12 496.23Pseudodiapomus inopinus10.66 436.30Paracalanus parvus 8.62 353.03Oithona davisae 7.26 297.18Acartia omorii 5.03 205.81Cyclopoida spp
15、.3.09 126.42Pseudodiaptomus marinus 2.43 99.54Acartia erythraea 1.77 72.29Acartia pacifica 1.70 69.63Centropages abdominalis 1.34 54.72Copepodite 0.49 20.05Sinocalanus tenellus 0.25 10.06Hemicyclops japonicus 0.15 6.31Nauplii 0.12 4.89Euterpina acutifrons 0.11 4.34Unidentified 0.09 3.75Calanus sinic
16、us 0.07 2.73Trotanus derjugini 0.04 1.69Microsetella sp.0.04 1.43Centropages tenuiremis 0.03 1.11Labidocera rotunda 0.01 0.21Temora turbinata 0.00 0.17Eurytemora pacificaBiomass (mg m-3)%TatalSpeciesTable 2-2Contribution of each species to the overall density and biomass of copepods collected over a
17、 period of twelve months along the Chikugo estuary;species are arranged in order of abundanceFig.4 Spatial and temporal variations in the numerical composition of copepod from April(A)2004 to March(M)2005 along the spatial gradient in Chikugo estuary.Note that the scale of the x-axis which shows the
18、 salinities are different.Copepod speciesSources of variationdfFPCyclopoida sp.TemporalSpatial11 6 5.21 7.020.0000.000Sinocalanus sinensisTemporalSpatial11 6 1.9021.760.0550.000NaupliiTemporalSpatial11 6 2.42 0.820.0130.556Acartia omoriiTemporalSpatial11 6 5.0817.490.0000.000Hemicyclops japonicusTem
19、poralSpatial11 6 2.61 2.300.0080.045Oithona davisaeTemporalSpatial11 6 5.6123.610.0000.000Pseudodiapomus inopinusTemporalSpatial11 6 3.3410.000.0010.000Pseudodiaptomus marinusTemporalSpatial11 6 4.89 8.870.0000.000Paracalanus parvusTemporalSpatial11 6 5.9720.300.0000.000CopepoditeTemporalSpatial11 6
20、 3.98 0.730.0000.626Acartia erythraeaTemporalSpatial11 6 8.51 2.980.0000.012Acartia pacificaTemporalSpatial11 6 9.00 6.670.0000.000Table 3Two-way analysis of variance(ANOVA)summary results of the spatial(seven sampling stations)and temporal(12 months)variations in the density of the dominant copepod
21、 species along the Chikugo estuaryFig.5 Spatial variation in the density of each of the dominant copepod species.Mean(SD)values are natural log transformed density(number m-3)data generated from 12 months samples collected from April 2004 to March 2005 along the spatial gradient in the Chikugo River
22、 estuary.Fig.6 Temporal variation in the density of each of the dominant copepods.Values are natural log transformed density(number m-3)collected from April 2004 to March 2005 along the spatial gradient in the Chikugo River estuary.SpeciesTemperatureChl-aSinocalanus sinensis-0.010.39Oithona davisae
23、0.440.28Acartia omorii 0.38 0.68*Cyclopoida spp.0.460.48Nauplii 0.410.16Centropages abdominalis 0.170.01Paracalanus parvus 0.470.41Pseudodiapomus inopinus 0.62*0.60*Pseudodiaptomus marinus 0.64*0.72*Acartia erythraea 0.69*0.66*Acartia pacifica 0.74*0.66*Hemicyclops japonicus 0.76*0.68*Copepodite 0.7
24、4*0.54Table 4Relationships(Pearsons correlation coefficient)between the monthly patterns of temperature and chl-a and the monthly abundance of dominant species of copepods(*P 0.01;*P 0.05)SpeciesTemperatureChl-aSinocalanus sinensis-0.010.39Oithona davisae 0.440.28Acartia omorii 0.38 0.68*Cyclopoida
25、spp.0.460.48Nauplii 0.410.16Centropages abdominalis 0.170.01Paracalanus parvus 0.470.41Pseudodiapomus inopinus 0.62*0.60*Pseudodiaptomus marinus 0.64*0.72*Acartia erythraea 0.69*0.66*Acartia pacifica 0.74*0.66*Hemicyclops japonicus 0.76*0.68*Copepodite 0.74*0.54Fig.7 Variations in the density of dom
26、inant copepods with salinity;the oligohaline copepods S.sinensis and P.inopinus showed a seaward decrease in abundance while the euryhaline copepods P.inopinus,O.davisae,P.parvus and A.omorii showed seaward increase in abundance.Values are natural log transformed density(number m-3).Sinocalanus sine
27、nsisPseudodiaptomus marinusPseudodiapomus inopinusOithona davisaeParacalanus parvusAcartia omoriiFig.8 Spatial and temporal variations in the total copepod density,biomass and diversity;values are mean(SD)and P values indicate the results of ANOVA.DependentvariableDesign summary(ANOVA)Independentvar
28、iableBetaValuePDensityF=8.72;R2=0.38;P0.0001Chl-a 0.3250.030BiomassF=13.08;R2=0.51;P0.0001Chl-aNTU 0.549 0.4270.0000.046DiversityF=4.64;R2=0.24;P0.0001Chl-aSalinity 0.331 0.2930.0460.026Sinocalanus sinensisF=4.95;R2=0.74;P0.050Chl-aPhP 3.48-6.360.0210.025Oithona davisaeF=6.54;R2=0.80;P0.050Chl-a-2.5
29、30.035Table 5 Summary results for multiple regression on the effects of environmental variables on density,biomass and diversity of all copepods and on the density of the two most dominant species(S.sinensis and O.davisae);the R2 values are adjusted R2Role of hydrographic variables in copepod abunda
30、nce and diversityFig.9 Patterns of interrelationships among temperature(C),chl-a(g l-1)and copepod density(number m-3)during four main seasons.Values are mean and error bars are standard deviations of three samples during each season.Pearsons correlation coefficient showed that seasonal patterns in
31、temperature,chl-a and density were significantly related to each other(values or r were 0.917(P 0.05),0.921(P 0.05)and 0.997(P 0.01)for temperature vs chl-a,temperature vs density and chl-a vs density respectively.D I s c u s s I o nTemperatureSalinityNTUNTUnegativecorrelationnegativecorrelationChl-
32、apositivelycorrelationpositivelycorrelationPhPnegativecorrelationpositivelycorrelationAreaSalinityDominant SpeciesSeasonthe ETM in the upper estuaryoligohaline(0.5-2.5)S.sinensisduring autumn to spring(summer is low density and was replaced byP.inopinus and Cyclopoida spp.)the ETM in the lower estua
33、ryeuryhaline(9.0-25.0)O.davisaeP.parvusA.omoriithe four seasons S.sinensis P.inopinusCyclopoida sppO.davisaeP.parvusA.omoriithe three most dominant speciesin this communityPlourde et al.,2002Satapoomin et al.,2004David et al.,2005High abundant(not show significant relation with temperature and seaso
34、n)Medium abundant(highly significant correlation with temperature,season and Chl-a)S.sinensis(in the upper)O.davisaeP.parvusA.omoriiP.inopinus(in the upper)A.erythraeaA.pacificaP.inopinusH.japonicusBousfield et al.(1975)The copepods that are transported from their original habitats are mostly moribu
35、nd,non-reproductive animals,suggesting that the transported habitats may constitute an extreme environment for these species.The edge effects,caused by mixing individuals from the two assemblages,result in increasing the species richness.Therefore,species richness may give erroneous impressions on t
36、he evolution of copepod species diversity along the spatial gradient in an estuary.Laprise and Dodson,1994AreaImportantIn the estuary as a wholeChl-a(ex.O.davisae)In upper estuaryPhP(ex.S.sinensis)Chl-a and salinity were the most important predictor variables.In the higher salinity regions had higher diversity.T H A N K Y O U
