The snails' tale in deep-sea habitats in the Gulf of Cadiz (NE Atlantic)

[摘要] Bridging the Atlantic and Mediterranean continental margins, the SouthIberian region has recently been the focus for geological and biologicalinvestigations. In this region, the Gulf of Cadiz (GoC) encompasses a greatvariety of deep-sea habitats that harbour highly diverse biologicalcommunities. In this study, we describe the composition of gastropodassemblages obtained from in situ colonization experiments and benthicsampling of deep-sea habitats in the GoC. Gastropod distributional patterns,such as bathymetric ranges, bathymetric turnover, affinity to substrate typesand abundance-occupancy relationships, are analysed and interpreted inrelation to their inferred dispersal capabilities and substrate availability.Overall, the GoC comprises a high diversity of gastropods (65 species), anddistinct assemblages were found in typical sedimentary environments at mudvolcanoes and in association with carbonate and coral samples or organicsubstrata. The number of taxa peaked at the Carbonate Province in the middleslope (600–1200 m depth), a highly heterogeneous area with numerous mudvolcanoes, carbonate mounds and corals. Darwin (1100 m) and CaptainArutyunov (1300 m) mud volcanoes harboured the most species-rich andabundant gastropod assemblages, respectively. Colonization experiments withorganic substrata (wood and alfalfa grass) also yielded diverse and abundantgastropod assemblages. These organic inputs allowed the recruitment of localspecies but mainly of wood specialist taxa that were not previously knownfrom the GoC. Our results suggest that the distribution of gastropodassemblages may be primarily determined by the occurrence of suitablehabitats, probably due to the effect of the substrate type on the structuralcomplexity of the habitat and availability and diversity of adequate foodsources. The type of larval development is apparently not a limiting factorfor colonization of deep-sea habitats. However, the predominance ofnon-planktotrophy, and especially lecithotrophy, suggests that a trade-offbetween more limited dispersal capability and higher potential forself-recruitment may be a recurrent pattern in gastropod species inhabitingreducing environments and other patchily distributed deep-sea habitats. Anetwork of suitable habitats that ensures effective population connectivitywould explain the predominance and relatively wide distribution ofshort-distance dispersing non-planktotrophic species in the GoC deep-seahabitats and other geographical regions.

[学科分类] 地球化学与岩石