Development of a bio-indicator for extreme benthic ecosystem: the use of benthic foraminifera

Abstract

Here, we present data focusing on the diversity and ecology of benthic foraminifera from different hydrothermal vent fields on the Mid-Atlantic Ridge at low and high latitudes and mud volcanoes leaking methane. This study aims to understand the controlling factors ruling the communities’ structure, including environmental parameters (sediment nature, geochemical dynamic associated with seafloor massive sulfide areas) and food source (primary production and chemosynthetic microbial communities). This study aims to i) fulfil a lack of knowledge of hydrothermal vent biodiversity, ii) determine interactions between foraminifera and their ecosystem, and iii) establish a bio-indicator of extreme environments, environmentally dynamic. We collected samples from two active vent sites, TAG and Snake Pit, in their periphery at low latitude and on the under-ice Aurora vent in the Arctic, showing contrasted mineralogy, pore water chemistry and organic matter compounds. The response of benthic foraminifera shows quite a stable community in the large periphery, while particular communities are observed in sediment with clear evidence of hydrothermal influence. For the mud volcano and active vents, a specific community of soft-body foraminifera and/or agglutinated species seems to be adapted to extreme environments, including species poorly known. Environmental data highlight a stronger impact of the habitat connected to microbial mats than organic matter availability. These preliminary results support the powerful use of benthic foraminifera in extreme environments to evaluate biodiversity and environmental changes but also highlight the need to improve the taxonomy of deep-sea soft-shelled foraminifera.