Bianchelli S et al. (2016), Biodiversity loss and turnover in alternative s...

ECB-ART-44954

Sci Rep 2016 Oct 06;6:34544. doi: 10.1038/srep34544.

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Biodiversity loss and turnover in alternative states in the Mediterranean Sea: a case study on meiofauna.

Bianchelli S , Buschi E , Danovaro R , Pusceddu A .

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In the Mediterranean Sea hard-bottom macroalgal meadows may switch to alternative and less-productive barrens grounds, as a result of sea urchins overgrazing. Meiofauna (and especially nematodes) represent key components of benthic ecosystems, are highly-diversified, sensitive to environmental change and anthropogenic impacts, but, so-far, have been neglected in studies on regime shifts. We report here that sedimentary organic matter contents, meiofaunal taxa richness and community composition, nematode α- and β-biodiversity vary significantly between alternative macroalgal and barren states. The observed differences are consistent in six areas spread across the Mediterranean Sea, irrespective of barren extent. Our results suggest also that the low biodiversity levels in barren states are the result of habitat loss/fragmentation, which is associated also with a lower availability of trophic resources. Furthermore, differences in meiofaunal and nematode abundance, biomass and diversity between macroalgal meadow and barren states persist when the latter is not fully formed, or consists of patches interspersed in macroalgal meadows. Since barren grounds are expanding rapidly along the Mediterranean Sea and meiofauna are a key trophic component in marine ecosystems, we suggest that the extension and persistence of barrens at the expenses of macroalgal meadows could also affect resilience of higher trophic level.

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Genes referenced: LOC100887844 ncaph

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	Figure 1. Forest plots showing the negative effect (red dots) determined by barrens on meiofaunal total abundance, total and individual biomass at all investigated areas (round symbol) and cumulatively for all areas (square symbol).Bars represent the standard error.
	Figure 2. Forest plots showing the negative effect (red dots) determined by barrens on meiofaunal and nematode diversity at all investigated areas (round symbol) and cumulatively for all areas (square symbol).Bars represent the standard error.
	Figure 3. Output of CAP conducted on the meiofaunal community taxonomic composition (a) and on nematode species composition (b)In (a) vectors are proportional to the percentage of variance in the community composition explained by each meiofaunal taxon.
	Figure 4. Relationships between % of barren coverage and β-diversity measures.(a) Jaccard β-diversity (βjac) and (b) turnover (βjtu) and loss of species (βjne) β-diversity components.
	Figure 5. Sampling areas (a) and alternative states: meadows in Tuscany (b), full barren in Croatia, sampling Site 2 (c) and patchy barren in Sardinia (d). In (a) the map was generated using Matlab R2015b (8.6.0), Unix version 64-bit (glnxa64), www.mathworks.com, and modified using Microsoft Power Point (version 14.0.7166.5000, 32 bit). In (b) collection of samples is illustrated. The coordinates of sites in (b–d) are reported in Table 1.