Benthic communities in the deep Mediterranean Sea: exploring microbial and meiofaunal patterns in slope and basin Earth ecosystems N. Lampadariou EastMed Symposium Regional Cooperation in Eastern Mediterranean Sea Research TheRoyal Apollonia Hotel, Limassol, Cyprus, 17-20 November 2014 Hellenic Centre for Marine Research
Slopes vs. basins Restricted size (roughly 10 %) Functioning of the oceans continent to ocean transfer of water, sediment and energy Sharp depth gradient equally sharp environmental gradients, (e.g. temperature and food availability) High habitat heterogeneity diverse communities.
Slopes vs. basins Restricted size (roughly 10 %) Functioning of the oceans continent to ocean transfer of water, sediment and energy Sharp depth gradient equally sharp environmental gradients, (e.g. temperature and food availability) High habitat heterogeneity diverse communities. Lack of environmental gradients Relatively uniform, (like deserts) Long considered constant and stable environments Evidence for regular and episodic disturbances (e.g. seasonal phytodetritus deposition, benthic storms).
Areas and stations 73 stations 5 areas depth range 115 4392 m major taxa (69 stations) nematodes (22 stations) microbes (16 stations)
Projects and surveys
Major aims of the study Expand knowledge on deep-sea community spatial patterns Investigate the potential role of food availability
Specific questions Does meiofauna differ between basins and slopes? Are there bathymetric patterns comparable to worldwide patterns of deep-sea fauna? Are the observed patterns similar between the two studied habitats and within different subregions? Are the patterns resulted from the current synthesis related to food availability?
Meiofauna Organisms < 0.5 (1.0 mm) Nematoda Copepoda Gatsrotricha Kynorhyncha...
Microbial communities Microbial diversity 16S rrna sequences assigned to OTUs (operational taxonomic units) Roche GSFLX 454 pyrosequencer
Diversity analysis Alpha diversity point or sample diversity Gamma diversity landscape or large area diversity Epsilon diversity richness of a broad geographic area that comprises different landscapes
Diversity analysis Differentiation diversity (beta and delta) based on Jaccard dissimilarity using multivariate dispersion (Anderson et al 2006) 1. variability among stations per habitat within specific depth ranges 2. variability among stations per depth range within each habitat 3. variability among stations for each habitat 4. variability among stations for specific depth ranges turnover between habitats and between depth ranges (pairwise comparisons)
Major taxa richness (27 taxa) N. Aegean (24) Cretan Sea (23) Central Med (13) Libyan (20) Eastern Lev. (21)
Nematoda genus diversity (155 genera) N. Aegean (108) Cretan Sea (88) Central Med (74) Libyan (83) Eastern Lev. (22)
Microbial diversity 55 213 16S rrna pyrotags and 9587 different OTUs 100% Other 80% 15 bacterial, 3 archaeal phyla and 5 candidate division 34 % of unidentified members of bacteria Dominance of Proteobacteria (32 %) and Acidobacteria (7%) Epsilonproteobacteria Betaproteobacteria Deltaproteobacteria 60% Other Proteobacteria Unclassified Archaea Thaumarchaeota 40% Alphaproteobacteria Acidobacteria 20% Gammaproteobacteria Unclassified Bacteria 0% Slope Basin Slope Cretan Sea Libyan Sea Basin Slope Levantine Gammaproteobacteria
Major taxa (a-diversity) Decreasing trend with depth The variation explained was higher for basin as compared to slope habitat
Nematodes (a-diversity) Similar decreasing trend with depth Not significant when only slopes are considered
Microbial (a-diversity) Opposite to the meiofaunal variables increase with depth
Nematodes richness estimator Estimated / observed overall: 160 / 155 basin: 128 / 123 Slope: 127 / 126 no differences among habitats
Microbial richness estimator Estimated / observed overall: 9067 / 9587 basin: 7673 / 7969 Slope: 3223 / 3329 Richness much higher at the basins
Delta diversity (major taxa)
Beta diversity (major taxa)
Delta diversity (nematode genera)
Major taxa community structure High variability within each habitat Differences among depth ranges PERMANOVA p for depth: 0.0001
Nematode genera No difference between basin and slope PERMANOVA p for habitat: 0.09
Nematode genera No difference between basin and slope Bathyal stations grouped together
Relationship with environmental parameters (overall)
Relationship with environmental parameters (slopes)
Conclusions High within-habitat variability of meiobenthic diversity neither strong nor consistent differences should be expected between basin and slope meiofauna Beta and delta diversity is high within and between the investigated habitats and appear to increase with depth
Conclusions Depth correlates with changes in deep-sea benthos, in particular within the basin habitat: richness diminish with depth community structure changes gradually Food availability relates also to meiofaunal patterns at different extents, depending on habitat type and taxonomic level of analysis This suggests that several other, perhaps depth-related, factors may drive the observed patterns
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