Spatiotemporal changes in microphytobenthos assemblages in a macrotidal flat (Bourgneuf Bay,France)1
Authors: Méléder Vona , Rincé Yves , Barillé Laurent , Gaudin Pierre , Rosa Philippe 
Published: February 2008

Spatiotemporal changes in microphytobenthos species composition were investigated in relation to structural variables—biomass; life‐forms; detritus ratio, pheopigmenta(pheoa):chl a; and sediment characteristics—at mesoscale in a shellfish macrotidal ecosystem. To characterize algae assemblages, multivariate analyses were performed (multidimensional scaling [MDS] ordination and clustering), supported by correlations between structural variables. Microphytobenthos, dominated by 97% diatoms belonging to 89 taxa, was constituted by two main assemblages: The first one, composed of common species (occurrence >50%), mainly nanobenthic (size <30 μm) and epipsammic (sand‐fixed cells), was associated with mixed sediments. The major species contributing to this assemblage wereNavicula perminuta,Achnanthes hauckiana, Fallacia tenera, A. lanceolatavar.elleptica, Amphoraspp., Plagiogrammopsis vanheurkii, andPlagiogramma tenuissimum(seeTable 2for taxonomic authors). Species diversity was high (N1∼ 11), often linked to high biomass values (>70 mg chl a · m−2) and low detritus ratio. Conversely, the second assemblage comprised occasional species (occurrence from 10% to 50%), mainly microbenthic (>30 μm) and epipelic (moving cells), occurring during summer at muddy sites. This assemblage, characterized by low diversity, high biomass variability, and high detritus ratio, was dominated byScolioneis tumidaorPlagiotropis vitreaandNavicula spartinetensis.Whereas hydrodynamics globally explained the gradual assemblage changes throughout the entire mudflat and the year, oyster beds and ridge and runnel features appeared to be local spatial structuring factors allowing the establishment of specific assemblages. This study suggests a significant role for epipsammon biomass, until now underestimated, in the functioning of this turbid coastal ecosystem.Microphytobenthic taxa identified from samples from the first 2 mm of sediment from Bourgneuf Bay (France) mudflat between May 2000 and July 2001.TaxaAbbreviationEcologyaSizeOccurrence (%)Common species Plagiogrammopsis vanheurkii(Grunow) Hasle, Stosch et SyvertsenPlagp vanhEpipsammicNanobenthic82.50 Amphoraspp.Amph spp.EpipsammicNanobenthic81.25 Achnanthes hauckianaGrunowAchn haucEpipsammicNanobenthic78.75 Navicula perminutaGrunowNavi permEpipelicNanobenthic76.25 Thalassiosira decipiens(Grunow) Jörg.Thal deciEpipsammicNanobenthic76.25 Fallacia tenera(Hust.) D. G. MannFall teneEpipelicNanobenthic73.75 Achnanthes lanceolatavar.ellepticaCleveAchn lancEpipsammicNanobenthic71.25 Cymatosira belgicaGrunowCyma belgEpipsammicNanobenthic68.75 Navicula spartinetensisM. J. Sullivan et ReimerNavi sparEpipelicNanobenthic68.75 Plagiogramma tenuissimumHust.Plagg tenuEpipsammicNanobenthic66.25 Cocconeis hoffmanniSimonsenCocc hoffEpipsammicNanobenthic65.00 Biremis ambiguaD. G. MannBire ambiEpipsammicNanobenthic58.75 Odontella aurita(Lyngb.) C. AgardhOdon auriEpiphyticMicrobenthic57.50 Navicula anglicaRalfsNavi anglEpipelicNanobenthic56.25 Cocconeis scutellumEhrenb.Cocc scutEpiphyticMicrobenthic55.00 Fragilaria pinnataEhrenb.Frag pinnEpipsammicNanobenthic53.75 Cocconeis peltaA. W. F. SchmidtCocc peltEpipsammicNanobenthic51.25Occasional Raphoneis amphicerosEhrenb.Raph amphEpipsammicMicrobenthic41.25 Actinoptychus undulatus(J. W. Bailey) RalfsActi unduEpipsammicNanobenthic38.75 Odontella rhombus(Ehrenb.) Kütz.Odon rhomBenthicMicrobenthic37.50 Navicula rostellataKütz.Navi rostEpipelicMicrobenthic37.50 Brockmaniella brockmanii(Grunow) Hasle, Stosch et SyvertsenBroc brocEpipsammicNanobenthic36.25 Plagiotropis vitrea(W. Smith) ClevePlagt vitrEpipelicMicrobenthic35.00 Paralia marina(W. Smith) Heib.Para marinaEpipsammicNanobenthic35.00 Delphineis minutissima(Hust.) SimonsenDelp minuEpipsammicNanobenthic32.50 Pleurosigma aestuari(Bréb.) W. SmithPleu aestEpipelicMicrobenthic31.25 Dimerogramma minor(W. Greg.) RalfsDime minorEpipsammicNanobenthic30.00 Podosira stelliger(J. W. Bailey) D. G. MannPodo stelEpipsammicMicrobenthic30.00 Staurophora amphioxys(W. Greg.) D. G. MannStau amphEpipelicMicrobenthic23.75 Nitzschiacf.frustulum(Kütz.) GrünowNitz frusEpiphyticNanobenthic23.75 Gyrosigma fasciola(Ehrenb.) J. W. Griff. et Henfr.Gyro fascEpipelicMicrobenthic22.50 Scolioneis tumida(Bréb.) D. G. MannScol tumiEpipelicMicrobenthic22.50 Gyrosigma distortum(W. Smith) CleveGyro distEpipelicMicrobenthic20.00 Craticula cuspidata(Kütz.) D. G. MannCrat cuspEpipelicNanobenthic20.00 Petroneis marina(Ralfs) D. G. MannPetr mariEpipelicMicrobenthic17.50 Actinoptychus splendens(Shabolt) Ralfs ex A. Pritch.Acti spleEpipsammicMicrobenthic17.50 Navicula phylleptaKütz.Navi phylEpipelicNanobenthic16.25 Navicula gregariaDonkinNavi gregEpipelicNanobenthic15.00 Cocconeis placentulaEhrenb.Cocc placEpipsammicNanobenthic13.75 EuglenophyceaeEuglBenthicMicrobenthic13.75 Pleurosigma angulatum(Quekett) W. SmithPleu anguEpipelicMicrobenthic12.50 Gyrosigma wansbeckii(Donkin) CleveGyro wansEpipelicMicrobenthic12.50 Nitzschia sigma(Kütz.) W. SmithNitz sigmaEpipelicMicrobenthic12.50 Nitzschiacf.panduriformisW. Greg.Nitz pandEpipelicNanobenthic11.25 Gyrosigma limosumSterrenburg et J. C. Underw.Gyro limoEpipelicMicrobenthic10.00 Auxospore (Melosiraspp.)AuxoIndNanobenthic10.00 Opephora pacifica(Grunow) P. PetitOpep paciEpipsammicNanobenthic10.00 Cerataulus smithiRalfs ex A. Pritch.Cera smitEpipsammicMicrobenthic10.00Rare Biddulphia biddulphiana(J. E. Smith) C. S. BoyerBidd biddEpipsammicMicrobenthic8.75 Plagiogrammopsis leve(W. Greg.) RalfsPlagp leveEpipsammicNanobenthic8.75 Fragilariaspp.Frag spp.EpipsammicNanobenthic8.75 Cyclotellasp.Cycl sp.IndMicrobenthic8.75 Nitzschia acicularis(Kütz.) W. SmithNitz acicEpipelicMicrobenthic7.50 Eunotogramma dubiumHust.Euno dubiEpipsammicNanobenthic7.50 Gyrosigma scalproides(Rabenh.) CleveGyro scalEpipelicMicrobenthic6.25 Plagiotropis elegans(W. Smith) ClevePlagt elegEpipelicMicrobenthic6.25 Surirellasp.Suri sp.EpipelicMicrobenthic6.25 Melosirasp. 2Melo sp.IndNanobenthic6.25 Thalassiosira punctigera(Castracane) HasleThal puncEpipsammicMicrobenthic6.25 Gyrosigma balticum(Ehrenb.) CleveGyro baltEpipelicMicrobenthic5.00 Melosiracf.jurgensiiC. AgardhMelo jurgEpiphyticNanobenthic5.00 Auliscus sculptus(Smith) Ralfs ex A. Pritch.Auli sculEpipsammicMicrobenthic5.00 Odontella regia(M. Schultze) SimonsenOdon regiaPlanktonicMicrobenthic3.75 Entomoneis paludosa(W. Smith) ReimerEnto paluEpipelicMicrobenthic3.75 Navicula ramosissima(C. Agardh) CleveNavi ramoEpipelicMicrobenthic3.75 Nitzschia closterium(Ehrenb.) W. SmithNitz closPlanktonicMicrobenthic3.75Very rare Cylindrotheca gracilisBréb.Cyli gracBenthicMicrobenthic2.50 Navicula cinctaEhrenb.Navi cincEpipelicNanobenthic2.50 Navicula cancellataDonkinNavi cancEpipelicMicrobenthic2.50 Navicula palpebralisBréb.Navi palpEpipelicMicrobenthic2.50 Diploneissp. 1Dipl sp. 1BenthicNanobenthic2.50 Diploneis didymaEhrenb.Dipl didyEpipelicMicrobenthic2.50 Nitzschiasp.Nitz sp.BenthicMicrobenthic2.50 Nitzschia palea(Kütz.) W. SmithNitz paleaEpipelicMicrobenthic2.50 Nitzschia bilobataW. SmithNitz biloEpipelicMicrobenthic2.50 Nitzschia constricta(Grunow) Hust.Nitz consEpipelicMicrobenthic2.50 Nitzschia fasciculataGrunowNitz fascPlanktonicMicrobenthic2.50 Triceratium antediluvianum(Ehrenb.) GrunowTric anteEpipsammicMicrobenthic2.50 Triceratium favusEhrenb.Tric favusEpipsammicMicrobenthic2.50 Grammatophora serpentina(Ralfs) Ehrenb.Gram serpPlanktonicMicrobenthic2.50 Campylodiscus echeneisEhrenb.Camp echeEpipelicMicrobenthic2.50 Cerataulus turgidusEhrenb.Cera turgEpipsammicMicrobenthic2.50 ChlorophyceaeChloBenthicMicrobenthic2.50 Scoliotropis latestriata(Bréb.) CleveScol lateEpipelicMicrobenthic1.25 Plagiogramma staurophorum(W. Greg.) Heib.Plagg stauEpipsammicNanobenthic1.25 Nitzschia spathulataBréb.Nitz spatEpipelicMicrobenthic1.25 Lithodesmium undulatumEhrenb.Lith unduPlanktonicMicrobenthic1.25 Melosira nummuloidesC. AgardhMelo nummEpiphyticNanobenthic1.25 OscillatoriaceaeOsciIndNanobenthic1.25aInd, ecology was undetermined.For definition of epipsammic, epipelic, epiphytic, nanobenthic, and microbenthic, see text (Materials and Methods).