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| Titel |
Macrofaunal assemblages from mud volcanoes in the Gulf of Cadiz: abundance, biodiversity and diversity partitioning across spatial scales |
| VerfasserIn |
M. R. Cunha, C. F. Rodrigues, L. Génio, A. Hilário, A. Ravara, O. Pfannkuche |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 4 ; Nr. 10, no. 4 (2013-04-17), S.2553-2568 |
| Datensatznummer |
250018203
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| Publikation (Nr.) |
 copernicus.org/bg-10-2553-2013.pdf |
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| Zusammenfassung |
| The Gulf of Cadiz is an extensive seepage area in the south Iberian margin
(NE Atlantic) encompassing over 40 mud volcanoes (MVs) at depths ranging
from 200 to 4000 m. The area has a long geologic history and a central
biogeographic location with a complex circulation ensuring oceanographic
connectivity with the Mediterranean Sea, equatorial and North Atlantic
regions. The geodynamics of the region promotes a notorious diversity in the
seep regime despite the relatively low fluxes of hydrocarbon-rich gases. We
analyse quantitative samples taken during the cruises TTR14, TTR15 and
MSM01-03 in seven mud volcanoes grouped into Shallow MVs (Mercator: 350 m,
Kidd: 500 m, Meknès: 700 m) and Deep MVs (Captain Arutyunov: 1300 m,
Carlos Ribeiro: 2200 m, Bonjardim: 3000 m, Porto: 3900 m) and two additional
Reference sites (ca. 550 m). Macrofauna (retained by a 500 μm sieve) was
identified to species level whenever possible. The samples yielded modest
abundances (70–1567 individuals per 0.25 m2), but the local and regional number
of species is among the highest ever reported for cold seeps. Among the 366
recorded species, 22 were symbiont-hosting bivalves (Thyasiridae,
Vesicomyidae, Solemyidae) and tubeworms (Siboglinidae). The multivariate
analyses supported the significant differences between Shallow and Deep MVs:
The environmental conditions at the Shallow MVs make them highly permeable
to the penetration of background fauna leading to high diversity of the
attendant assemblages (H′: 2.92–3.94; ES(100): 28.3–45.0; J′: 0.685–0.881). The Deep MV assemblages showed, in general, contrasting
features but were more heterogeneous (H′: 1.41–3.06; ES(100):
10.5–30.5; J′: 0.340–0.852) and often dominated by one or more siboglinid
species. The rarefaction curves confirmed the differences in biodiversity of
Deep and Shallow MVs as well as the convergence of the latter to the
Reference sites. The Bray–Curtis dissimilarity demonstrated the high β-diversity of the assemblages, especially in pairwise comparisons involving
samples from the Deep MVs. Diversity partitioning assessed for species
richness, Hurlbert's expected number of species and Shannon–Wiener index
confirmed the high β-diversity across different spatial scales
(within MVs, between MVs, between Deep and Shallow MVs). We suggest that
historical and contemporary factors with differential synergies at different
depths contribute to the high α-, β- and γ-diversity
of the mud volcano faunal assemblages in the Gulf of Cadiz. |
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