Benthic Communities in the Deep Mediterranean Sea: Exploring Microbial and Meiofaunal Patterns in Slopebasin and Ecosystems K

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Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , α 3 Discussions Biogeosciences -diversity was higher at δ -diversity) increases with δ , and A. Tselepides erent depth categories. Results 2 ff - and β 17540 17539 , P. N. Polymenakou 1 erentiation diversity ( ff erences were found among depth ranges, though turnover ff ect of productivity on benthic patterns. Non parametric analyses ff erences for meiobenthic standing stocks and major taxa diversity ( ff , N. Lampadariou 1 erences between habitats. On the other hand, components) between the two habitats (basin vs. slope) for the whole in- ff δ and γ , This discussion paper is/has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG if available. Hellenic Centre for Marine Research, Institute of Oceanography, P.O. Box 2214,Hellenic 710 Centre 03, for Marine Research, Institute of Marine BiologyUniversity and of Genetics, Piraeus, P.O. Box Department of Maritime Studies, G. Lambraki 21 and Distomou, – Published: 11 December 2012 community structure varies greatly among samples regardless of the type of habitat, no clear pattern was detectedmatode with genera regard suggests to higher habitat diversityfound type; in no the slopes, di observed whereas number richnessthe of estimator basin ne- Jack1 habitat, but novalues di were high in allof pairwise multivariate comparisons analysis of are thetat in di variability line of with meiofaunal the communitiestowards and above the a findings, gradual indicating abyssal change stations. high ofsignificantly within In meiofaunal habi- structure contrast higher to at meiobenthic the results, basin microbial richness ecosystem is and tends to increase with depth, while β vestigated area and withinabundance and each richness region, follow butcreasing the revealed well-known depth, gradient significant whereas of bathymetricdepth. di decreasing trends: In values spite with of in- a similar bathymetric trend observed for nematode genera richness, small-size components of deep-sea benthos,Mediterranean metazoan basins meiofauna and and slopes. bacteria,areas A from along grid the of central-eastern Mediterranean 73Aegean basin Sea, stations (central Cretan sampled Mediterranean, Sea, at northern Libyanrevealed Sea, five a eastern high geographical Levantine) diversity spanning in over termsties. 4 of km The both in higher metazoan depth meiofaunal meiofauna abundance andSea and microbial richness highlights communi- observed the in e thedetected northern no Aegean di The long held perceptionform of oceanic the basins deep hastem sea over with consisting wide the of habitat decades monotonous heterogeneity.a given Under slopes large the way and dataset prism to uni- of was the a used idea highly to diverse of describe environment, a and complex compare sys- spatial patterns of the dominant Abstract Biogeosciences Discuss., 9, 17539–17581, 2012 www.biogeosciences-discuss.net/9/17539/2012/ doi:10.5194/bgd-9-17539-2012 © Author(s) 2012. CC Attribution 3.0 License. 1 Heraklion, Crete, Greece 2 2214, 710 03,3 Greece 135 82, Piraeus, Greece Received: 16 November 2012 – Accepted: 24 November 2012 Correspondence to: K. Sevastou ([email protected]) Published by Copernicus Publications on behalf of the European Geosciences Union. Benthic communities in the deep Mediterranean Sea: exploring microbial and meiofaunal patterns in slopebasin and ecosystems K. Sevastou 5 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent habitats ff erences in meio- ff erences in benthic parame- ff 17542 17541 erences among depth ranges are more important. ers from the results reported by Vanreusel et al. (2010) ff ff orts of the past few decades. The recent breakthroughs in deep- ff erences between these two habitats and contradicts partly the results ff In the Mediterranean the continental shelf is very narrow and therefore the largest As most of the deep sea is heterotrophic, food supply to deep-sea benthos is derived The deep sea consists of slopes and basins. The slopes are the steep part of the con- sive bibliographic references reportedFollowing in major trends Danovaro in et ecology, recentgitudinal al., investigations and have 2010; sought bathymetric Gambi for patterns latitudinal, etDanovaro of lon- et al., meiofauna al., (Lampadariou 2010). 2009a, and 2010;faunal Tselepides, Gambi et patterns 2006; al., among 2010), deep-sea while2010; habitats few study Gambi (Danovaro di et et al., al.,Mediterranean 2010). 2009a,b; slopes Danovaro Vanreusel and et et basins al. al., foundthan (2009a) that in in meiofaunal deep-sea a plains. diversity This study in di that slopes including found was samples no higher from di part of this enclosed seaare is among classified as the deep most sea. studiedthose Though areas of Mediterranean of ecosystems other the areas world,out (Danovaro deep-sea over et fauna the al., research last 2010). lagsour three Nonetheless, behind knowledge decades considerable on on work the the smallest carried but deep most Mediterranean abundant meiofauna metazoans has of the advanced sediments (exten- the highest on Earth (Ramirez-Llodradiversity-depth et pattern al., 2010 with andbenthos, a references though therein). midslope this A diversity trend unimodal maximummay and vary the has depth among been where basins, recognisedRamirez-Llodra diversity regions, peaks et for benthic are al., components not 2010,and or universal and extending and taxa references research (Rex to therein). and includehelp Hence, Etter, elucidate more by 2010; this taxa increasing basic and sampling bathymetric more trend areas of of benthic the diversity. deep oceans will in turn lead to spatio-temporalmunities variability along in the the continental benthos. The marginsreflect variability is changes of mostly in benthic food related com- supply, tostanding sediment depth, characteristics stocks which or however decrease other may factors.tremely exponentially While low down levels benthic in the the abyssal plain continental (Rex et margin al., 2006), and deep-sea biodiversity reach is among ex- space and time and so does the organic matter arriving at the deep seafloor; this may ultimately from surface production. Primary productivity of the euphotic zone varies in such as temperature andmargins, food slopes availability. are As also an characterisedcommunities by important (Levin high and component habitat Sibuet, of heterogeneity 2011).gradients continental and In and host contrast, diverse are oceanic basins relativelyfor lack uniform, long environmental appearing considered constant similarthat and to basins stable deserts; are environments. However, for dynamic evidencedisturbances, that environments now such that they exists as sustain were seasonal considerable phytodetritusEtter, regular deposition 2010). and and benthic episodic storms (Rex and tinental margins that connect the continentalrestricted shelf size with (roughly the 10 deep-sea %, plains. Ramirez-Llodra Althoughtems et of for al., the 2010), functioning slopes of are the essentialthe oceans ecosys- and continent-to-ocean the transfer globe of as water, theydepth constitute sediment the gradient and region of energy where takes slopes place. is The sharp characterised by equally sharp environmental gradients, Covering more than 60 % ofsea the Earth’s is surface the and about largest 90 ecosystemfloor % of on remains the earth largely oceans, the unexplored (Ramirez-Llodra deep in etthe spite intense al., research of 2010). e the Yet the enormoussea deep-sea technological research advances and have neverthelessphysical revealed and biochemical a characteristics complex that lead systemand to benthic wide with communities. variability diverse of di geological, ters between the twohabitat habitats variability are is neither high strong and nor di consistent; it appears that within 1 Introduction depth or area. The results presented here suggest that di 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent ff erent geographical areas. ff erent depths in the central-eastern er between basins and slopes, (2) ff ff 17544 17543 erent benthic components, and (4) whether the patterns ff In the course of 10 multidisciplinary European collaborations, benthic samples were To expand knowledge of deep-sea community spatial patterns we examine the dom- Microbial benthic community studies are a recent addition to deep-sea research in sampling. All analyses were focusedfauna on metazoan the and sediment bacteria surface, where is the gathered. bulk Meiofaunal of samples meio- were first treated with Mediterranean is classified as deep sea. collected during 12 oceanographicbasin of surveys the at Mediterranean Sea di and (Table 1). basin Overall, a ecosystems grid were oftral 73 sampled Mediterranean, stations at the located 5 northern at slope regions Aegeaneastern Sea, along Levantine the (Fig. the Cretan 1, Mediterranean: Table Sea, S1).by the the At Libyan cen- each means Sea station, of and sediment the samples multiple-core were sampler, collected which allowed for undisturbed sediment surface ranean in two basins,by the many western complex and structural themud volcanoes, features, central-eastern and such basins. several steep as It environmentalincreasing is gradients, canyons, salinity among characterised cold and which an seeps, temperature eastward ing gradient seamounts and productivity and a gradient. southward Due and to eastward decreas- the narrow continental shelf the largest part of the parameters worldwide. 2 Methods 2.1 Study area and sampling The Mediterranean Sea, anlargest oligotrophic and marine deepest system enclosed with sea increased salinity, on is Earth. the The Strait of Sicily divides the Mediter- taxa, nematode generawhether and there bacteria are species majorthe shifts di in observed benthic patterns parameters alongsubregions are and depth similar among ranges, the between (3) di whether resulted the from the two current studied synthesis data habitats, are consistent within with di patterns of deep-sea fauna investigating: (1) whether benthic parameters based on meiofaunal metazoan major padariou, 2004; Lampadariou and Tselepides, 2006). More specifically, we aimed at recorded in the deep-seaand sediments anoxic ecosystems compared (Zinger to et open al., 2011). ocean surface waters,inant vents small fractions of benthos,from meiofauna the and bacteria. central-eastern A Mediterraneanbasin large and basin and detailed slope is dataset ecosystems usedWe over pay for special large describing attention scale and tobecause including the food comparing di potential availability role has ofMediterranean been productivity (Danovaro invoked for et as the al., a observed 1995; major patterns Tselepides factor of et benthic al., trends 2000; in Tselepides the and Lam- 9.6 million bacterial V6-rRNA ampliconssurface for to 509 the samples deep-sea thatsity. floor span Their in the analysis order global has to ocean’s shownin investigate remarkable microbial global horizontal patterns communities. and of Overall, verticalpelagic bacterial benthic large-scale communities, diver- patterns communities and a appeared substantially more higher diverse diversity than of bacterial populations was trary to what hasparameters been do found not for change the withet larger depth benthic al., but remain components, 2010). constant microbial Recent (Rexthat community studies et many al., dealing 2006; bacteria with Danovaro foundlow bacterial water in diversity (Li estimates the et have deep al.,Schauer revealed 1999a,b; et sea al., Polymenakou are et 2010; al., Zinger similarsupport 2005a, et ubiquitous to al., 2009; dispersal those 2011). Kouridaki and On a et livingmenakou biogeographical the al., pattern in et other 2010; of hand, al., soil sediment there 2005b). bacteria or is (Poly- Only little shal- recently, evidence to Zinger et al. (2011) performed an analysis of nematode genera diversity was considered. the Mediterranean. A high level ofranean bacterial Sea richness (Luna has et been al.,ble recorded 2004; to in Polymenakou other the et deep-sea Mediter- al., sediments (Li 2005a,b, et 2009), al., which 1999a,b; is Bowman compara- and McCuaig, 2003). Con- of Netto et al. (2005) that found higher diversity in basins southeast of Brazil only when 5 5 20 25 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 0 C. ◦ 20 − -CGACRRCCATGCANCACCT-3 0 erentiation diversity through a multivariate ff 17546 17545 ) and 1027r (5 0 erences in meiofauna abundance (overall and of nema- erences in di ff ff erent ways. Following the concept of Anderson et al. (2006), we measured to relax tissues and subsequently preserved by adding 10 % formalin. Sed- ff 2 -GATTAGATACCCBNGTA-3 0 erentiation diversity (the rate of change in species composition) can be measured ff Hypothesis testing for di Di Total microbial community DNA was extracted from approximately 1 g of sediment was done using permutational multivariate analysis of variance (PERMANOVA). Of delta diversity was consideredall as stations for the each variabilitymeasure habitat of in dissimilarity and taxa/species used, for the compositionadvantage each method among of proposed depth by testing range. Anderson for Besides ettest for al. di being homogeneity (2006) in flexible has dispersions on the (PERMDISP,ferentiation Anderson, the diversity, 2006). the Another turnover facet of of dif- ranges taxa/genera was between also habitats measured and and between for depth consistency was presented as Jaccardtodes dissimilarity. and copepods), richness (TR and NR) and meiofauna and nematode structure in many di beta and delta diversityBeta using diversity multivariate was dispersion measuredstations based (i) per on as habitat Jaccard for the eachcomposition dissimilarity. variability depth among in range/area stations taxa/genera and per (ii) composition depth as among range the within variability each in habitat. taxa/genera In a similar context, (i) for each station, identifiedof either alpha as diversity, (ii) basin for or eachate slope habitat measure habitat, within of each as gamma of a (landscape/largethat the univariate area) corresponds five measure diversity to studied and epsilon areas (iii) as diversityJacknife for (biogeographic a estimator the (Jack1) province univari- whole was diversity). also data The calculated set firstas using order an EstimateS v. estimator 8.2.0 of (Colwell, 2006) trueeach habitat. nematode richness for the whole meiobenthic data set and for In the present study,number meiofaunal of and nematode meiofaunal taxa) diversityrespectively. refer and Following to genus Whittaker’s taxon richness scheme richnessrately (NR, (1972), for (TR, number we three of levels calculated of nematode TR inventory genera), diversity and (the NR diversity of sepa- a defined geographic unit): 2.3 Data analyses SRA054862. gene libraries were successfullyples) constructed by for 16 targeting of802f the the (5 hypervariable sampled V5-V6 stationsClaesson (19 region sam- with et the al.,duced following 2010). by set using The of a sequencesSequences primers: Roche GS-FLX that of 454 were the pyrosequencerassigned shorter (Roche, partial Mannheim, than using 16S Germany). 200 rRNA thewere bp submitted genes in Ribosomal to were length Database NCBI pro- were Sequence Project removed. Read Taxonomy classifier. was Archive Pyrosequencing with the data study accession number using the pictorial keyswell of as relevant Platt literature dealing and with(e.g. Warwick new Schuurmans species (1983, and Stekhoven 1988), genera Jr, from WarwickVincx, 1950; the et 1987). Soetaert Mediterranean al. and (1998) Decraemer, as 1989; Soetaert and material per station (UltraClean Soil kit, MoBio, Carlsbad, CA, USA) and 16S rRNA and 30 µm mesh sieves. Thetriplicate fauna centrifugation retained or on triplicate the flotation, 30 µmica using sieve in solution was both of extracted cases by 1.18 Ludox either with TM specific colloidal Rose gravity. sil- After Bengal extraction, and meiofaunatode sorted samples community to analysis were was higher stained based taxon onmatode level identifications, samples under subsampling from was 22 a performed out stereomicroscope. sosediment of Nema- that core the at were 69 least selected. stations. 200 After For nematodes subsampling, ne- anhydrous per specimens glycerol, were evenly slowly evaporated spread in on microscope slides and identified to genus level iment samples for microbial analysis were kept frozen at 2.2 Laboratory treatment In the laboratory, meiofauna samples from 69 stations were sieved through 500/1000 6 % MgCl 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 in 2 in the 2 erentiation ff ects marine ff add-on software + 3500 m and six cat- > erences in di ff 500 m, < ). at northern Aegean) were found in slope sta- 2 17548 17547 3000 m). PERMANOVA analysis applied to data sets > erences in metazoan meiofaunal abundance between the ff at Cretan Sea to 93 ind/10 cm 2 erences were detected in relation to depth, more pronouncedly at the basin habi- Irrespective of the type of habitat, depth or area, meiofaunal abundance followed the For microbial diversity analysis, sequences were assigned to OTUs (operational tax- ff http://www2.biology.ualberta.ca/jbrzusto/rarefact.php based on benthic copepod abundance, which showed a sharper depth gradient clearly tions except from theresults central (Table Mediterranean 2) indicated and di thetwo northern habitats only Aegean. for PERMANOVA two depthdi ranges (1000–1500 m and 2500–3000 m), buttat significant where meiofaunal abundance changed1000 gradually m) from to the the shallower stationsfrom deeper (up each ones to of ( the fivebetween regions the separately two could habitats not distinguish either meiofaunal (statistics abundances not shown). Similar results were obtained pattern of nematode abundance. Theall lowest five values were areas recorded (Fig. atin 3), basin the stations while in central thewere Mediterranean highest also and values observed at were the basin observedat stations Libyan Central in at sea. Mediterranean the slope and five The Mediterranean northern stationsind/10 regions lowest Aegean cm only (0–6 basins), copepod ind/10 whereas cm abundances the highest values (5 northern Aegean basin (1271 mstations, depth). habitats As and expected,75 nematodes areas, % predominated with to in 88 an % all to in average 95 the percentage % basins in contribution of thetaxa ranging Levantine Levantine of and some and from importance Cretan Central were Sea, Mediterranean(0.2–4 copepods %) respectively, slopes (4–16 and %), and (Fig. from polychaetes the 2). (0.2–2 72 %), group % 4 Other tardigrades %) of meiofauna (Fig. soft 2). bodied animals (turbellarians, gnathostomulids) (0.5– 3.1 Meiofaunal standing stocks Average meiofaunal densities inthe deep the basin sediment of the surface central ranged Mediterranean (2837 from m depth) 2 to ind/10 1249 cm ind/10 cm 3 Results onomic units) using theaccording QIIME to software Schloss and ata Handelsman 3 % distance (2005). sequence Individual-based level divergence rarefactionsity of curves (species analysis 3 Chao1 at level) % richness estimator (species( were level) calculated using and the the rarefaction calculator commonly used for microbial diver- diversity (measured as multivariate(nMDS) dispersion). Non-metric ordinations multi-dimensional were scaling All used analyses to were illustrate performed(Clarke spatial and with Gorley, PRIMER patterns 2006; Anderson v6 of et with al., meiofauna PERMANOVA 2008). structure. tions of residuals under aanalysis, reduced was model. DISTLM performed routine, for aables exploring permutational and relationships regression depth. between These analyses multi-root were transformed or based abundances, univariate on except vari- from Bray-Curtisuntransformed richness, dissimilarities data for of are which considered square- more Euclidean appropriate. distancesbathymetric To explore on and whether habitat the observed heterogeneity patternspermutational analyses apply were to also applied the to wholeMDISP data Mediterranean, routine sets from the was each area applied separately. PER- for measuring and exploring di basin and slope. Nevertheless,sediment since communities, it it was is necessary to wellysis. consider known depth Thus, range that the as overall water a experimental factor depthtwo in design the a levels consisted anal- (basin, of slope) twoegories fixed and in factors: depth, habitat, between with with of eight 500 m levels resolution). ( p-values were obtained using 9999 permuta- central interest was the relationship of meiofaunal parameters with habitat type i.e. 5 5 25 15 20 10 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , - ε 10, ± Acan- Pselionema , SD: 160 ± Oxystomina , 500 m) and those down to 1500 m < Microlaimus , 17550 17549 erent depth ranges were not present in both ) and six more genera were found in all areas ff Metasphaerolaimus erences in TR among depth ranges and not habitat (Table 2) , ff Sphaerolaimus , 11, respectively) is very close to the one observed in the data set -diversity of nematodes peaked in the northern Aegean sea (108 ± γ ). 48 genera were restricted to one station of which 46 were found only -diversity, Fig. 4b). With the exception of eastern Levantine, values of TR Daptonema α Halalaimus , erences in the number of nematode genera between habitats (Table 2); this ff 12 and 127 ± The number of nematode genera predicted by the species richness estimator Jack1 Similar to TR, Gamma diversity of the five studied regions was high (Fig. 5a) reaching the highest DISTLM results complemented those of PERMANOVA, indicating that depth explains (155, 123 and 126). Thisfor the estimator slope showed habitat a (Fig. clear 6) sign despite of the fact approaching that an the asymptote number of samples for this habitat habitats, depth was not includedanalysis; in nevertheless, the PERMANOVA DISTLM design results fordepth nematode indicated for community a the whole significant nematodethan dependence data 60 of % set NR of and on its fordecreases the variability with basin (Table depth 3). habitat, (Fig. Similar which 4c). to explains the more rest offor the the univariate whole variables, investigated NR area,128 the basin and the slope habitat (mean genera, Fig. 5b), but it(22). was Likewise, lowest a-diversity at ranged thenorthern from most eastern 13 Aegean part in slope of the (Fig.cated the eastern basin, di 4c), Levantine the and basin Levantine as topattern opposed 77 could in to not the TR, howeverfrom be PERMANOVA verified results the for indi- Cretan each of Sea. the Because studied the areas di separately except A total of 155 genera wereanalysis encountered was in conducted. the 22 Among samples these,tholaimus where three nematode genera community were foundand in habitats ( all stations ( Syringolaimus in one sample. Mediterranean regions but onlyshown). within Similar the to Aegean meiofaunal andwas abundance the also trends, Libyan higher variability seas in in the (statistics TR basin not habitat explained (Table by 3). 3.2.2 depth Nematodes depth (Fig. 4b). However, this bathymetric pattern could not be observed in all the DISTLM results for TRthe (Table variation 3) in showed the that number depth of explains meiofaunal taxa, a which significant decrease amount with of increasing water value in the Aegean Searespectively) (24 whereas, and the 23 taxa lowest(13 at value the was taxa, northern found Fig. Aegean at andnorthern 5a). the the Aegean TR Cretan central basin, Sea, ranged Mediterranean respectively area Libyan from sea and two ( from to threewere 18 to higher in 16 at the at the basin deep-seastatistically habitat central significant slopes (Fig. Mediterranean di 5a). of Nevertheless, and the PERMANOVApointing results the showed to similar bathymetric patterns with that of meiofaunal abundance. Indeed, ples, which along with polychaetes, tardigradesand and halacaroids habitats. were Cnidarians found at were allcumaceans, areas echinoderms found and only scaphopods in werewere restricted slope found to stations, only basin at stations. whereas one The aplacophorans, latter station (northern Aegean, 1224 m depth). copepod abundances (Table 3) and inthe all central the part studied (statistics Mediterranean not areas shown). except from 3.2 Diversity 3.2.1 Meiofaunal taxa Overall, 27 meiofaunal taxadiversity). Of were these, only encountered nematodes in and copepods all were found studied at areas all stations and and sam- habitats ( as well as from the rest (Table 2). a significant amount of theto variation in decrease meiofaunal with abundance depth (Table 3), (Fig.pared which 4a). to appears The slope variation habitat explained was (Table 3). higher The for same basin as bathymetric com- pattern was also observed for distinguishing between the very shallow stations ( 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erences ff ered between ff of pairwise tests p 30 %) regardless of erence in nematode er either (PERMDISP ff > 2500 m), however, the ff > erences in delta diversity ff erences in meiofaunal taxa community ff 17552 17551 500 m, 13.27 %; PERMDISP < 0.01) due to the low variability in meiofauna composi- 55 %). The same bathymetric trend was also observed 38 %) than between habitats (22.22 %). At smaller scale ∼ > p < 0.05) and rather high, suggesting greater variability in meiofau- erent OTUs, respectively. Chao1 richness estimator predicted 19489 p > ff erent depth ranges were tested (Table 4), di ff erences in meiofaunal taxa towards greater depths. This pattern of bathy- ff 0.05 for all depth categories) but variability appears to increase with depth for both erentiation diversity analysis of nematode community was performed only at the erence in structure is gradual as successive depth ranges appear similar in terms erent microbial species, an extremely high microbial richness comparable to values Further non parametric multivariate analysis provides support to the above results When the di DISTLM analysis indicated a marginally significant dependence of microbial diversity ff 0.05 for all comparisons of the first depth range). Statistically significant di ff ff Di level of the whole data set (delta diversity), as at smaller scales (within each habitat di of meiofauna taxa down toanalysis 2000 indicated m that depth. depth Similarcommunity explains to (Table a 3). the significant This univariate holds variation variables,habitat also of DISTLM (Table when meiofaunal 3) the major analysis and taxa (statistics is within not applied shown). each separately for Mediterranean each region except from3.3.2 the central Nematodes part with nMDS plotwithin of each all habitat stations(Fig. (Fig. illustrating 7b). 7a) the PERMANOVA and high resultsamong variability a depth indicated ranges in gradient but di not meiofauna of habitatthe (Table structure meiofaunal 2). shallower Meiofauna (up communities composition to di with 1500 m depth depth) and the deeper stations ( were also found for beta diversityJaccard of dissimilarity depth between ranges depth for the rangesrelatively basin for habitat increasing the but whole for not data depth for set slope. positional categories (delta di deeper diversity) was than 1500metric m, increase indicating was higher stronger com- within(beta the diversity), slope where habitat values butthe were was depth rather not category. high observed (89 for % basins of values same area and of similar depth (data not shown). were detected (PERMDISP tion among the very shallow stations< ( when Jaccard dissimilarity was measured between the two habitats for stations of the bilize close to a high value ( Delta diversity basedtats on (PERMDISP meiofaunal majornal taxa taxa (Table composition 4) within ( was(within depth similar ranges), beta at diversity ofp both the > two habi- habitats did notbasin di and slope (Tabletwo 4). habitats On (Table the 4) other increases hand, down meiofaunal to taxa 1500 turnover m between depth the after which it appears to sta- of the benthic parameters,Nevertheless, microbial this trend richness could tends not to be verified increase separately with for3.3 depth each of (Fig. the 4d). Diversity two change habitats. and community structure 3.3.1 Meiofaunal taxa Pyrosequencing analysis produced 55213 16Sferent OTUs rRNA were pyrotags finally and identified a fromRichness the total was 19 of much samples 9587 analysed higher dif- for7969 at microbial and diversity. the 3329 basin di compareddi to the slope habitatfound accounting in for the highly diverse soil environments. on depth for the whole microbial data set (Table 3), suggesting that, opposite to the rest genera number between the twooverlap habitats (not as shown the in confidence Fig. intervals 6). of the two curves 3.2.3 Microbial diversity is comparably low (12). As opposed to NR, Jack1 predicts no di 5 5 25 15 20 10 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ). 2 ect on nematode ff 0.05) which ranged be- p > erences in delta diversity were 0.045) correlation of microbes ff = erences between the two habitats p ff 78 %) was very high, clearly indicating > 17554 17553 C, Coll et al., 2010) and therefore, the organic con- ◦ erent depth ranges (PERMDISP 77 %) and samples ( ff > erences in multivariate dispersions between the two habitats (PER- ff 0.05) with higher delta diversity recorded at the basin habitat (Table 5, p < One of the best known gradients in marine sediments is that of abundance with One-way PERMANOVA results did not indicate di type (Gambi et al., 2010;general Rex bathymetric and trend Etter, of 2010). abundance Our and results indicate are the in agreement existence with of this this pattern for Our data also confirms theSea, prediction as of the higher faunal higher densities meiofaunal in density the was northern measured Aegean in thiswater area. depth. Similar todepth all has benthic been groups, found thepattern to has relationship be been of mainly significant meiofaunal related and(Rex to density organic negative et and matter (Rex al., input, et food 2006;enced limitation al., Soltwedel, and by 2006). food 2000), a quality This number although general of it factors is such also as suggested the to hydrography of be the locally area influ- and the sediment sequence, higher faunal densitiesdances are reported anticipated in for the this presentin area. synthesis other are The oceans indeed meiofaunal (for lower an abun- from extensiveble reference those to report of those see similar recorded Gambi depths et from al., similarLampadariou, 2010) Mediterranean but 2004; deep-sea compara- sediments Lampadariou (Tselepides and Gambi and et Tselepides, al., 2006; 2010), Lampadariou yet et they fall al., within 2009; a wider range of values (2–1249 ind/10 cm particular low levels of productivitynutrient in input the is Eastern further Basinwater diminished (Psarra before temperatures et reaching (12.8–15.5 al., the 2000).tent deep-sea The of floor the low due Mediterranean to deepa the sediments result, high is extremely benthic low standing (DanovaroNevertheless, stocks et there in al., 1999). the are As Mediterranean areasSuch are in an expected area the to is Mediterranean the be northernof depressed. Sea nutrient-rich Aegean which Sea Black mainly Sea are due waters more to (Poulos riverine productive. et outflows al., and 1997; the Lykousis influx et al., 2002). As a con- 4.1 Standing stocks in the deepIn sea the energy-poor environmentlinked of to the food deep supply. The sea, Mediterranean many Sea community is parameters an unusually seem oligotrophic system with 4 Discussion among depth ranges ( high variability of microbial communities at all spatial scales. between nematode community and depth, which is stronger for3.3.3 the slope habitat. Microbial communities DISTLM analysis found no correlationdata of set microbial and community with the depthwith basin for depth habitat, the though whole when it thethese suggests slope results ( stations as areor the only gradient lack considered (plot of (Table not apparent 3). shown). grouping nMDS Jaccard could enhanced dissimilarity not between reveal the any two spatial habitats pattern (82 %), experimental design due to thevice lack versa. of However, all as depth illustrated rangesstations within in (slope each stations Fig. type down 7d, of togrouped nematode habitat 1000 m communities and separately depth of from and most basin thecommunity bathyal stations structure. rest down Indeed, to suggesting DISTLM 2000 that m) results are (Table depth 3) has indicated a an significant e relation detected between the di tween 17.72 % at the shallowest(Table depth 5). range However, and Jaccard 41.14 % dissimilarity at betweenvalues 2500–3000 depth m for depth categories range all ranged within pairwisetode high comparisons genera between (41–75.3 %) depth categories. suggesting high variability infor nema- nematode community either (Tableplot 2), which (Fig. is 7c). also Similar depicted in to the nematode relevant nMDS diversity analysis, depth was not included in this revealed strong di MDISP 46.54 %). A rathertwo high habitats (39.35 Jaccard %) indicating dissimilarityonly high within value variability but in was also nematode between also habitats. community In recorded structure contrast, not between no di the and within each depth range) not all levels of each factor were present. PERMDISP 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent sources ff erences. ff ort from this region. On the other ff erences between the two habitats in the deep 17556 17555 ff -diversity of the five studied areas was also high, re- γ 1306 OTUs in Polymenakou et al., 2005b). From these ∼ SE Brazil. Because slope stations are usually found in shallower areas higher ff erent classes of Mollusca), especially when the data set is from di In a recent study on global patterns of marine microbial communities Zinger At smaller scale, meiobenthic In a pan-Mediterranean deep-sea meiofauna study Gambi et al. (2010) reported ff productivity, geology, hydrology and evolutionary historyfor the of explanation the of area, the are observed hypothesised trends. On the other hand, bathymetric patterns of results, it is evident thatmicrobial the diversity. deep Mediterranean sediments harbour an incredibly high 4.2.1 Bathymetric patterns of alpha diversity Biodiversity research in the deepric sea patterns has of largely concentrated benthicpattern on communities. has revealing For been bathymet- many described taxa, (reviewed inmediate mainly Rex depths, macrobenthic, and i.e. a Etter, between 2010) parabolic 1500 with a and maximum 2500 at m, inter- while several factors, such as surface the traditional Sanger basedbacterial sequencing OTUs analysis. (9587) than Indeed, anywas a previously detected much reported in higher from the present the numberwhich study, Mediterranean of while is deep-sea Chao1 at richness least estimatorMediterranean one predicted a order sediments number of ( magnitude higher from any previous estimates from the et al. (2011) obtained morein than the 120 deep 000 sea. OTUs, In of thefound Mediterranean which to deep-sea almost range sediments, 41 bacterial from 000 richness 13 were hasPolymenakou to reported been 1306 et OTUs al., per gram 2005b,et of 2009), al., surface 2010). sediment but In (Luna estimations et ouranalyzed al., study, exceed for microbial 2004; the 4000 communities of first species the timemethod (Danovaro is deep by expected Mediterranean applying to Sea increase the were significantly(Danovaro powerful the et estimates tool of al., of microbial 2010) 454 species as richness pyroseqeuencing. it This can detect the rare taxa that cannot be analyzed through hand, the lower nematodeLevantine, genus may well richness depict in themay the well-known also west-eastward most decrease be eastern of an productivity part indicationtode and for diversity of a (Lampadariou the link and basin, between Tselepides, surface the 2006; productivity Lambshead and et al., deep-sea 2000, nema- 2002). however it may be related to the lowest sampling e lowest number of major meiofaunal taxasistent found at with the previous central bibliographic Mediterranean reports area is (Gambi con- et al., 2010 and references therein), the same research group.present Likewise, the study number (155) of isdeep-sea nematode among (extensive genera bibliographic the report identified highest in in reportedhighest, Miljutin the until et as al., now only 2010) from Soetaertwhich and the most however and Mediterranean was probably the based Heip onas (1995) deep-sea well found and as from a shelf-break the sites higher North from number Atlantic. the of Mediterranean generagardless of (163), the taxonomic level of the analysis, and peaked in the Aegean Sea. The other reported not only in thereferences Mediterranean therein). Sea This but finding worldwide could (Gambi be etin an al., artefact most 2010 of review and the or treatment synthesis ofdi the papers data ambiguous sets taxa as areor usually research grouped together groups. In (e.g. theretained case down of the to present the synthesis, meiofauna lowest classification was possible level as meiofaunal samples were treated by sea o meiofaunal abundances would be expected atwithin this each habitat. type However, the of high habitatscale variability may probably be related the to reason environmental that heterogeneity statistical at analysis smaller could4.2 not indicate di Small-size benthos diversity The number of meiobenthic metazoan taxa encountered in our study is higher than any central Mediterranean) irrespective of the type of habitat or investigatedthat taxon. meiobenthic abundances athabitats, slopes including were basins. higher Ourwith than findings Netto other contradict et investigated al. these (2005) types results who of but found are no di in agreement meiofauna in all the eastern Mediterranean basins (all investigated areas except from 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent ff erences for erences due ff ff erent areas or ff ectively. ff erences in the communi- er depending on the tax- ff ff erence was not statistically significant. ff erences in diversity between the two habitats ff 17558 17557 ected by depth (Li et al., 1999a; Danovaro et al., 2010; ff SE Brazil showed that the results di ff erence between the two habitats for nematode genera diversity as ects biodiversity levels and patterns (Levin et al., 2001; 2010; Van- cient for estimating nematode genera richness in the area (the curve ff ff ffi erences between these two habitats on a global scale; and Netto et al. (2005) in Our detailed study suggests that no di Although there is considerable gap in the study of spatial microbenthic patterns, ff samples are su should be expected innumber of the major central-eastern meiofaunal taxa basinonly was of exception on being average the higher eastern Mediterranean. at Levantine,Opposite the this Although basin to di the environment, this, the nonof nematode parametric genera statistical indicated analysis thatof slopes based true are richness on more estimator the diverse.suggesting Jack1 Nevertheless, observed no the are number di results consistentwell. with Despite the the results fact that based morefor on basin nematode than major richness slope estimation, taxa samples the were shape included in of the Jack1 analysis curves reveals that whilst slope di a deep-sea study o onomic level of analysisnematode families, (higher higher diversity diversity at at deep-sea slope basin for for nematode major genera). taxa, no di types of habitats will helpsea. understand Slopes the and complicated deep-sea patterns basinsto of are diversity their two in major wide the habitats variability deep ties with inherent in they di environmental host settings. andYet Thus, in results di biological based patterns onet could al. recent be (2009a) meiobenthic and found studies Gambi betweentaxa et and are these al. nematode rather two (2010) species found habitats. of contradicting.ranean, higher European Danovaro respectively; diversity margins Vanreusel in and et slopes on al. based major on (2010) taxa major from based the on Mediter- nematode genera reported no Although much of the variabilitygradient in and deep-sea depth-related diversity factors, has it been isof closely now greatly related the appreciated to that seafloor depth the a highreusel complexity et al., 2010). Therefore, documenting and comparing the diversity of di 4.2.2 Habitat-related diversity authors argue that highso microbial that diversity in a theorganic system Eastern matter under available. Mediterranean Clearly, more starvation has observationsgation stress evolved are of required is as plausible well able explanatory as factors tocautiously the before investi- though utilise reaching a speculate any conclusive that quantityMediterranean pattern. basin the We or might could food-limited have quality been environment of verse the of community stress in factor the order that central-eastern to led use to the the available evolution food of resources a more di- e it has beenbathymetry and found thus that it isPolymenakou microbial not personal a observation). diversity Contrary is tosults suggest those similar an previous increase observations, among of our microbialverified sediments richness re- independently with within of depth, each which could of variable not the however two be habitats. In Tselepides et al. (2007), the parametric regression analysis revealed aand highly NR significant with negative depth correlation withinMoreover, of the the TR high whole variability explained investigated by areathe depth decrease and for in the within diversity basin each with ecosystem depth typebathymetric suggests is pattern of that sharper was habitat. at not, the however, basin discernible environments. withinproviding The each strong observed of support the to investigated the areas, diversity suggestion patterns of depend Danovaro also et al. on (2009a) topographic that and meiobenthic ecological features. a decrease in richness2009b; Gambi with et increasing al., depthmatode 2010) for richness and patterns major copepod are species taxa eitherhabitat (Baguley (Danovaro absent et types et or al., (Lampadariou not al., 2006), consistent andOur 2008, whereas among Tselepides, results ne- di 2000; are in Danovaro agreement et with al., the 2009a,b, general 2010). trend of meiobenthic diversity, as non meiofaunal diversity have been generally found to be similar to that of abundance, with 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er- ff cult to be ffi ect benthic communities. ff erent types of ecosystems ff 1500 m) after which the varia- erences between the two habi- ∼ ff erentiation diversity in marine sediments ff 17560 17559 erences in sampling depths. Apart from sampling ff erences between habitats closer to the abyssal zone. ff ering higher availability and variability of food, which ultimately is shaped into ff ort, increased heterogeneity within the habitats may be another explanatory factor, At smaller scale (within depth range), beta diversity of the two habitats ranges at Rex and Etter (2010) in their synthesis book on deep-sea biodiversity conclude that So far, comparative microbial studies of the two studied habitats are not available. ff roughly proportional to the rate ofzone change and in lower depth, therefore in being the higher in abyssal the plain. bathyal In our study, the overall high values of nematode This is in agreement with thediversity findings correlate of with Ellingsen depth. (2002) In that athe several rather two measures similar habitats of way, meiofaunal beta increases taxa down turnovertion between to in mid-slope meiofaunal depths taxa ( to between constantly basin high and meiofaunal slope di appears to be equallythe high, rate pointing of changedients in in species the composition is deep especially sea, pronounced and along they depth further gra- state that the rate of faunal replacement is ences in meiofaunal communities. Indeed,has di been positively related toand environmental Gray, 2002; heterogeneity Anderson (Ellingsen, et 2002; al., Ellingsen 2006). low to moderate values (23–40ues %), with depth, yet suggesting it that shows meiofauna community a varies bathymetric more trend as we of move increasing deeper. val- Local diversity in deep-sea sedimentsEtter, is 2010). not Following the only discussion high onthe but observed diversity also results, richness quite turnover patterns. variable diversity The (Rex underlines els high and of delta diversity taxonomic of analysis the clearly twoin indicates habitats the basin for high both and variation levin slopethe meiofaunal ecosystems. composition variation When should focusing also exclusively beready on been expected stated, to nematode the be community, deep higherlocal sea within topographic is the and characterized other basin by a environmental habitat. wide features, As variation which has of may al- habitats also due account to for di are known to experience strongsediment instability perturbations factors (Canals due et to al., current 2009), which flow, may landslides, a or4.2.3 other Turnover: patterns of change in diversity and community structure biodiversity. On the other hand, slope environments, in particular the steeper slopes, fore o than other types offace ecosystems, waters. such Our as study vents,slope anoxic ecosystems is and habitats the clearly and indicates first openmicrobial that comparing the communities ocean deep-sea than sur- microbial basins the harbour slopes. communities morefor Similar from diverse microbial to the basin richness, bathymetric this and patternexplained. excess we Although of observed environmental data diversity are in nottion considered the on here deep-sea and microbial basins available informa- communities isbasin is di may still be very explained limited,et on the al. the higher (2005), basis microbial according of richness to the which, of deep-sea the source-sink basins hypothesis act proposed as by sinks Rex of food sources, there- habitat variability may be higher than between habitats. The first report onwas benthic provided microbial communities veryet from recently al. di (2006), by this study Zinger demonstrated that et the al. deep-sea sediments (2011). were more Similar diverse to the study of Sogin as a factor intherefore the preclude analysis. the Thereby, no possibility control thattats for the may depth observed be was di a possiblee and consequence we of cannot di as has been previously suggested (LevinSibuet, et 2012). al., Local 2001; variability Vanreusel in etincluding various al., environmental substrate 2010; conditions Levin structure, and within hydrology, eachhabitat food habitat, complexity input with and probably more disturbance, microhabitat-specific results species. As in a higher result, within expected as in deep-sea plainssparsely metazoan distributed pointing abundance to is the reducedmore need and rare of the species. a animals This more are becomesof intense meiobenthic even sampling more metazoan in (Giere, imperative order 2009). due toples It to collect is available the also for patchy worth the distribution noting nematode that community the analysis number did of sam- not allow incorporating depth reaching an asymptote), more basin samples are needed. This is rather a result to be 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er- ff ect on ff er among ff erences due to their wide ff erences within and between the two ff 3000 m) group together suggest a stable > ers from the other depth categories, whereas ff 17562 17561 erences in the low to moderate values of delta ff erences should be expected between basin and ff ected by depth. More specifically, its structure was ff ers more towards the abyss. This is further supported ff erences in either delta or beta diversity were indicated ff 1000 m) and di < er significantly between the bathyal and the abyssal stations; neverthe- -diversity components that are not only high within and between the inves- ff erences and gradients statistically supported by non parametric multivariate δ ff - and erent taxa in various environmental settings. β In their comprehensive study on global patterns of marine microbes, Zinger All the above results are summarised and depicted in the ordination plots with the ob- ff in tigated depth ranges but also appear to increase with depth. Depth has an e lead to higher “within” thanhere “between” indicate habitat high variability. Indeed, withinthat the neither habitat results strong presented variability nor ofslope consistent all ecosystems di meiobenthic in variables themore as and deep an suggest Mediterranean overriding correlate Sea.the with basin In changes habitat. in contrast, Meiofaunal deep-sea abundance depthcommunity benthos, and structure appears in richness changes particular once clearly gradually within diminish fromiments. with the This depth shallower and bathyal shift to in the meiobenthic abyssal sed- community along the depth gradient is also evident 5 Conclusions Deep-sea slopes and basins are twovariability habitats with in inherent environmental di settings.habitat Nonetheless, owing existing to local/regional heterogeneity features within and each variation in environmental conditions may the coastal environment and suggestednamics that of this the is nutrient-poor due deepmicrobial to sea. the community In lower contrast, in environmental our dy- theeven results between indicate Mediterranean a samples deep-sea highly of variable exceedingther the investigation 77 same % is habitat, needed in area tostudy dissimilarity unravel or patterns support similar of the bathymetry. microbial Although idea diversity,heterogeneity fur- the and of results regular a of or our dynamic episodic disturbances. deep-sea environment characterised by habitat three depth categories (1000, 3000, 4000limited m) number in the of Mediterranean stations Sea.study and Apparently, the could consequently not the have few allowed depth the categories detection involved of in the that bathymetricet gradient al. reported (2010) here. found less variable communities in the deep sea sediments compared to reported by Danovaro et al. (2008) that found nematode assemblages to di synthesis of major meiofaunal taxa in abyssal sediments. A similar pattern was also di served di analysis. Indeed, meiofaunal communitytigated varies habitats greatly and within isfound each greatly to of a di theless, two the inves- change ismore gradual, similar with assemblages than ofMoreover, distant the nearby ones, fact depth that in categories the deeper particular appearing stations with ( regard to major taxa composition. are increased also, and withstations the of exception the of the Portuguesegories very in margin, high Mediterranean they dissimilarity slopes. at The appearstudies the observed clearly similar shallow di indicates among that all theneeds beta three further diversity depth and component cate- substantial of meiofaunal investigation communities in order to clarify bathymetric patterns of among depth ranges deeperbased on than nematode 500 m. genera, with Adiversity no among roughly di all similar depth categories. resultranean In margins was a (Danovaro also study et on obtained al.,ences diversity 2009b), among from dissimilarity Atlantic habitats results and and used Mediter- areasis for appear exploring considered, di with similar lowest to values ourstions of when and beta higher major diversity and taxa within rather composition 2000 the similar m). group values When of of dissimilarity 500 nematode m for composition depth deeper stations changes sta- (1000 are and investigated, dissimilarity values with depth in theSea meiofaunal case composition of di majorby taxa PERMDISP composition results indicate asthe that the shallower stations in rate ( of theno change Mediterranean statistically in major significant taxa di composition is low within Jaccard dissimilarity between depth ranges, and the increase of Jaccard dissimilarity 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 2006. ´ e de la Cuadra, C. 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M., Ferrero, T., Gad, G., Tselepides, A., Lampadariou, N., and Polymenakou, P.: Benthic community structure and func- Tselepides, A., Papadopoulou, N., Podaras, D., Plaiti, W., and Koutsoubas, D.: Macrobenthic Tselepides, A. and Lampadariou, N.: Deep-sea meiofaunal community structure in the Eastern Soltwedel, T.: Metazoan meiobenthos along continental margins: a review, Prog. Oceanogr., Soetaert, K. and Vincx, M.: Six newSogin, Richtersia M. species L., (Nematoda, Selachinematidae) Morrison, from H. G., Huber, J. A., Welch, D. M., Huse, S. M., Neal, P. R., Arri- Soetaert, K. and Heip, C.: Nematode assemblages of deep-sea and shelf break sites in the Soetaert, K. and Decraemer, W.: Eight new Tricoma species (Nematoda, Desmoscolecidae) Schuurmans Stekhoven Jr, J. H.: The Freeliving Marine Nemas of the Mediterranean, I. The Rex, M., McClain, C., Johnson, N., Etter, R., Allen, J., Bouchet, P.,andRex, War M., Etter, R., Morris, J., Crouse, J., McClain, C., Johnson, N., Stuart, C., Deming, J., Schloss, P. D. and Handelsman, J.: Metagenomics for studying unculturable microorganisms: Ramirez-Llodra, E., Brandt, A., Danovaro, R., De Mol, B., Escobar, E.,Rex, German, M. C. and R., Etter, R.: Deep-sea Biodiversity: Pattern and Scale, Harvard University Press, Psarra, S., Tselepides, A., and Ignatiades, L.: Primary productvity in the oligotrophic Cretan Schauer, R., Bienhold, C., Ramette, A., and Harder, J.: Bacterial diversity and biogeography in Polymenakou, P. N., Lampadariou, N., Mandalakis, M., and Tselepides, A.:Poulos, Phylogenetic S., di- Drakopoulos, P., and Collins, M.: Seasonal variability in sea surface oceanographic Polymenakou, P. N., Bertilsson, S., Tselepides, A., and Stephanou, E. G.: Links between ge- Polymenakou, P. N., Bertilsson, S., Tselepides, A., and Stephanou, E. G.: Bacterial community Platt, H. M. and Warwick, R. M.: Freeliving Marine Nematodes. Part II: British Chromadorids, Platt, H. M. and Warwick, R. M.: Freeliving Marine Nematodes, Part I: British Enoplids, Cam- Netto, S. A., Gallucci, F., and Fonseca, G. F. C.: Meiofauna communities of continental slope 5 5 30 25 20 15 10 30 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 17570 17569 , 2011. Cretan Sea, Libyan Sea Eastern Levantine, Libyan Sea Eastern Levantine, Libyan Sea Libyan Sea Sep-1997 Cretan Sea Jan-2007 Libyan Sea Overview of projects, surveys and investigated areas involved in the present study. Project/Expedition SurveyMATER AreaMETEOR 40 Mar-1997TransMed Dec-1997 Northern Aegean, Northern Aegean,ADIOS Jun-1999BIODEEP No ofHERMES Stations Central Mediterranean, Depth range (m) METEOR Aug-2001 Oct-2001 71 13 May-2006 Central 8 Mediterranean Central MediterraneanBIOFUN Cretan Sea, Dec-2006 / 4HERMIONE 115–2273 & Eastern 1221–4261 Levantine,REDECO (jointcruises) 2950–3870 Jun-2009 Jan-2010 May-2010 5 3 Central Eastern Mediterranean, Levantine, Cretan Sea, 3080–3424 May-2011 2786–2837 4 10 Libyan Sea 5 2014–4392 21 508–3603 1204–3335 874–3607 Welch, D. B., Martiny,of J. bacterial B. beta-diversity H.,doi:10.1371/journal.pone.0024570 in Sogin, seafloor M., Boetius, and A., seawater and ecosystems, Ramette, PLoS A.: ONE Global 6, patterns e24570, hysterids, The Estuarine and Brackish-Water Sciences Association, Shrewsbury, 1998. Table 1. Zinger, L., Amaral-Zettler, L. A., Fuhrman, J. A., Horner-Devine, M. C., Huse, S. M., Mark Whittaker, R. H.: Evolution and measurement of species diversity, Taxon, 21, 213–251, 1972. Warwick, R. M., Platt, H. M., and Somerfield, P. J.: Freeliving marine nematodes, Part III: Mon- 5 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

1500-2000 >3500 >3500 3000-3500 >3500 3000-3500 3000-3500 >3500 3000-3500 2500-3000 2500-3000 2000-2500 2500-3000 2500-3000* 2000-2500 2000-2500 2500-3000 1500-2000 Variability 2000-2500 1500-2000 1500-2000 1500-2000 1000-1500 A posteriori pairwise posteriori A comparisons

F p 31 1000-1500 1000-1500* 1000-1500 1000-1500 2000-2500 erences were indicated pairwise comparisons ﬀ 17572 17571 500-1000 500-1000 500-1000 500-1000 500-1000 ects of habitat and depth for uni- and multivariate meio- Within habitat: basin Within habitat: slope ﬀ <500 <500 <500 <500 <500 0.0001 0.3813 0.0343 0.0582 0.2243 0.0001 0.0983 p 0.1984 0.2374 0.0768 0.0001 0.0001 0.0046 0.5592 1.583 1.401 3.185 7.936 F 7.8645 1.0318 5.1425 1.5549 1.3677 4.9251 1.6703 Overall Meiofauna abundanceCopepod abundance 43.261Major taxa richness 0.0001Nematode richness 49.597Microbial richness 0.0001Meiofaunal 44.478 community 0.392 35.299Nematode 0.0001 community 30.290 0.425 0.0002Microbial community 0.0001 4.851Basin 7.508 0.399 0.0439Meiofauna 0.638 0.0001 abundance 1.278 0.311 Copepod abundance 0.1850 31.111Major 0.222 taxa richness 0.273 0.0001Nematode richness 30.289Microbial 0.070 richness 0.0001Meiofaunal 48.147 community 0.420 19.624Nematode 0.0001 community 21.238 0.413 0.0016Microbial community 0.0001 0.072Slope 5.914 0.528 0.7876 0.69801Meiofauna 0.621 0.0006 abundance 0.6189 0.331 Copepod abundance 10.727Major 0.007 taxa richness 0.330 0.0015Nematode 0.065 richness 26.752Microbial richness 0.0001Meiofaunal 8.2169 community 0.328 5.6115Nematode 0.0079 community 9.7574 0.549 0.0682Microbial community 0.7223 0.0003 4.3778 0.4632 0.272 0.0055 0.483 1.7881 0.307 0.0448 0.126 0.422 0.263 Variable 6.287 2.931 0.582 Depth Depth Habitat x Depth Habitat Habitat x Depth Habitat Habitat Habitat x Depth Habitat Depth Habitat Source Habitat x Depth Habitat Depth Results of DISTLM analysis for exploring relationships of benthic parameters with PERMANOVA results of the e 1 PERMANOVA results PERMANOVA of the effects of habitat and depth for uni- and multivariate meiofaunal variables. Where statistical significant 1 One-way PERMANOVA (depth was not included in the experimental desing) * statistically significant differences between habitats the for 1 specific depth at range p < 0.05 Major taxa richness Nematode richness Meiofaunal community Nematode community Copepod abundance Table 2. differences were indicated pairwise comparisons were done. Variable Meiofaunal abundance

depth. Table 3. faunal variables. Where statistical signiﬁcant di Table 2. were done.

n/a n/a 40.83 40.83 >3500 >3500 >3500 n/a n/a 36.84 35.54 35.54 36.84 3000-3500 3000-3500 3000-3500 3000-3500 3000-3500 n/a 38.10 26.32 25.00 53.33 55.56 60.00 63.16 39.93 38.81 26.32 38.10 55.56 2500-3000 2500-3000 2500-3000 2500-3000 2500-3000 42.11 38.89 31.58 57.14 66.67 70.00 73.68 16.67 24.60 30.16 31.58 38.89 42.11 57.14 2000-2500 2000-2500 2000-2500 2000-2500 2000-2500 β-diversity δ-diversity 31.82 36.36 22.73 40.91 22.22 38.10 47.62 43.48 37.24 30.76 38.73 18.18 31.82 34.78 40.91

Slope 1500-2000 1500-2000 1500-2000 1500-2000 1500-2000 33 39.1 0.05. 39.13 36.36 44.00 54.17 38.46 19.05 36.36 46.15 22.22 36.92 25.96 30.77 42.31 38.46 50.00 17574 17573 -diversity 1000-1500 1000-1500 1000-1500 1000-1500 1000-1500 p < δ n/a 52.38 42.11 35.00 47.37 36.36 43.48 27.27 36.36 16.67 29.23 22.22 22.59 37.24 33.31 36.92 29.23 18.18 39.13 41.67 40.91

500-1000 500-1000 500-1000 500-1000 Slope 38.45 500-1000 Slope n/a 45.00 33.33 26.32 47.37 36.36 36.36 33.33 47.62 33.33 13.89 26.09 30.77 39.93 30.76 13.27 25.96 22.59 28.57 35.00 45.45 16.67

<500 <500 <500 <500 Basin 42.00 22.22 <500 Basin Basin erences among levels at 500 500–1000 1000–1500 1500–2000500 2000–2500 500–1000 2500–3000 1000–1500 1500–2000 3000–3500 2000–2500 2500–3000 3000–3500 ** ﬀ Differentiation diversity based on major meiofaunal taxa Jaccard dissimilarity. Values within each habitat 46.54 40.67 17.72 n/a 37.96 35.74 28.07 41.14 39.43 29.63 < < >3500 3000-3500 2500-3000 2000-2500 1500-2000 1000-1500 <500 500-1000 2500-3000 2000-2500 1500-2000 Slope 500-1000 1000-1500 2500-3000 Basin * 1500-2000 1000-1500 500-1000 3000-3500 >3500 * statistically significant differences among levels at p < 0.05 ** statistically significant differences among levels at p < 0.001 n/a: Few samples running PERMDISP for Between depth ranges Between habitats Between depth ranges Betweenhabitats Within depth ranges Table 4. and within each depth range were calculated using multivariate dispersion. Dissimilarity increases from 0 to 100. Within habitats Within depth ranges Within habitats

erentiation diversity based on major meiofaunal taxa Jaccard dissimilarity. Values

erentiation diversity based on nematode genera Jaccard dissimilarity. Values within ff 1 2 ff Di Di 3500 75.29 74.70 74.51 71.60 66.67 61.67 61.29 Statistically significant di 500–10001000–15001500–20002000–25002500–30003000–3500 44.00 > 47.46 47.06 56.84 46.55 65.00 50.49 59.18 63.27 65.66 59.79 47.86 56.36 61.06 55.86 60.42 56.99 59.79 53.25 41.10 50.65 Within habitats∗ Between habitats BasinWithin depth ranges 39.35 Slope Between depth ranges ∗ each habitat and withinsimilarity each increases depth from 0 range to were 100. calculated using multivariate dispersion. Dis- Table 5. n/a: few samples for running PERMDISP. within each habitat and withinDissimilarity each increases depth from range 0 were to calculated 100. using multivariate dispersion. Table 4. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

Copepoda Kinorhyncha Annelida Nematoda Others Halacaroidea Rotifera Ostracoda Tardigrada bodied Soft Slope Basin North Aegean North Slope Libyan Sea Libyan Basin

37 Slope 17576 17575

Levantine Basin Slope Cretan Sea Cretan Basin Slope Cent Med Cent Basin 0% 90% 80% 70% 60% 50% 40% 30% 20% 10% 100% Meiofauna composition per studied area and habitat. Study areas and sampling stations along the Mediterranean Sea.

Figure 2

n 5000

5000 5000 5000

microbial richness ( 2980 39

675 1898 2011 1499 4000 4000 4000 1910 4000 3424 1619 340

Cretan Sea (D) 1204 1465 3335 1049 153 1079 Eastern Levantine 3334 2273 942 1271 3000 3000 3000 3000 508 1840 3301 Slope slope Microbial richness D Nematode richness C 1250 Major richness taxa B 874 3281 1839 4260 Depth (m) Depth (m) 1224 Meiofaunal abundance A abundance Meiofaunal 1772 3200 3544 3607 Basin 2000 2000 2000 2000 1221 22) and basin 3080 1580 3589 17578 17577 2419 965 = 2837 1284 3315 805 2043 n 2799 1194 1000 1000 1000 1000 2845 115 Libyan Sea Libyan Central Mediterranean 914 Northern Aegean 2786 1966 2707 0 0 0 0 0

80 60 40 20 50 80 60 40 20 50

300 250 200 150 100 140 120 100 450 400 350 300 250 200 150 100 800 600 400 200 160 140 120 100

ind/10 cm2 ind/10 cm2 ind/10 cm2 ind/10 ind/10 cm2 ind/10 0 ind/10 cm2 ind/10 0 meiofaunal abundance ( 0 0 1600 1400 1200 1000 1 5 0 0 0

Figure 3 10 10 20 15 90 80 70 60 50 40 30 20 10

100 900 600 300

1000

1800 1500 1200 2100

Number of genera of Number OTUs of Number ind/10 cm ind/10 Number of taxa of Number 2

(A) 2 1

Figure 4

1 2 nematode genus richness ( (C) Bathymetric gradient of Nematode abundance per studied area and habitat in relation to depth. Note in x-axis 69), = n ( Fig. 4. logarithmic scale for meiofaunal abundance. Fig. 3. the arrangement of depth in increasing order for each habitat separately. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

Slope major meiofaunal taxa, Eastern Eastern Levantine Levantine (A) 30

Basin 41 Libyan Sea Libyan Libyan Sea Libyan Nematode richness B Major richness taxa A Overall

20 40 Overall

Cretan Sea Cretan Cretan Sea Cretan Slope 17580 17579 Jack1 Number of samples Aegean Aegean Basin Northern Northern Northern Northern 10 Central Central Mediterranean Mediterranean 0 5 0 40 20 80 60 15 10 30 25 20

120 100

Number of genera of Number Number of taxa of Number 0

Figure 5 60 40 20 80

180 160 140 120 100

2 1 Number of genera of Number Meiofaunal diversity per studied area and habitat based on Richness estimator Jack1 for nematode genera.

Figure 6 nematode genera.

Fig. 6. Fig. 5. (B) 1 2 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

Stress: 0.08 Stress: 0.11 nematode genera (C–D) depth. (B, D)

D B

17581 habitat and major meiofaunal taxa and Stress: 0.11 Stress: 0.08 (A, C) (A–B)

Figure 7

C A

nMDS ordination based on composition with symbols indicating Fig. 7.