ALBERT

Description: Hydrothermal vents on mid-oceanic ridges are patchily distributed and host many taxa endemic to deep-sea chemosynthetic environments, whose dispersal may be constrained by geographical barriers. The aim of this study was to investigate the connectivity of three populations of the ‘scaly-foot gastropod’ (Chrysomallon squamiferum Chen et al., 2015), a species endemic to hydrothermal vents in the Indian Ocean, amongst two vent fields on the Central Indian Ridge (CIR) and Longqi field, the first sampled vent field on the Southwest Indian Ridge (SWIR). Connectivity and population structure across the two mid-oceanic ridges were investigated using a 489-bp fragment of the cytochrome oxidase c subunit I (COI) gene. Phylogeographical approaches used include measures of genetic differentiation (FST), reconstruction of parsimony haplotype network, mismatch analyses and neutrality tests. Relative migrants per generation were estimated between the fields. Significant differentiation (FST = 0.28–0.29, P 〈 0.001) was revealed between the vent field in SWIR and the two in CIR. Signatures were detected indicating recent bottleneck events followed by demographic expansion in all populations. Estimates of relative number of migrants were relatively low between the SWIR and CIR, compared with values between the CIR vent fields. The present study is the first to investigate connectivity between hydrothermal vents across two mid-ocean ridges in the Indian Ocean. The phylogeography revealed for C. squamiferum indicates low connectivity between SWIR and CIR vent populations, with implications for the future management of environmental impacts for seafloor mining at hydrothermal vents in the region, as proposed for Longqi.

Description: The ocean margins contain a great variety of habitats and biological communities. Recent discoveries, such as deep-water coral reefs, show that these communities are poorly described and understood. However, observations have already indicated that benthic communities on ocean margins show high levels of spatial and temporal variation at all scales. The European continental margin is increasingly exploited for both biological resources (fisheries) and non-biological resources (oil, gas, minerals). Environmental management of the exploitation of continental margins requires an understanding of natural levels of variation inherent in biological communities that are potentially impacted by such activities. This paper presents a synthesis of the present knowledge of the spatial and temporal variation of slope communities. Priorities for future research and its technological development are discussed. The aim of this research is to provide a scientific basis for the environmental management of the continental slopes of Europe.