Community characterization of two Atlantic seamounts. First steps into addressing the influence of the Mediterranean Outflow Water (MOW)

Poster presentation at ATLAS 3rd General Assembly.

An important goal of the ATLAS project is to improve our understanding of the ocean transport pathways and connectivity of water masses at basin and regional scales relevant for benthic marine ecosystems. The MEDWAVES cruise (21^st September-26^th October, 2016) aimed to better understand the characteristics of the Mediterranean Outflow Water (MOW) and its potential influence in the occurrence, composition and distribution of deep-sea benthic communities from the Mediterranean to the Azores. Among the geomorphological features targeted in MEDWAVES, two Atlantic seamounts were included: Ormonde (Portuguese continental shelf) and Formigas Bank (close to the Azores Archipelago). During MEDWAVES, the geomorphology and oceanography of the areas was characterised. Further submarine video transects were conducted by means of a Remotely Operated Vehicle (ROV). The transects were performed in the different flanks of the seamounts aiming to characterise the benthic communities considering different geographical orientations and the influence of water masses. 

The characteristics of the video transects allowed to perform a methodology for video analysis based on still images. The images were taken directly from the video recordings at regular length intervals based on the positioning of the ROV, generating a set of images that allowed for comparisons between different areas. To make such comparisons robust, a thorough filtering was carried out based on the position of the parallel laser beams on screen. Only images that had a similar area observed were selected, in which all megabenthic organisms are currently being identified to the lowest possible taxon. It is expected that this protocol can be used for the video processing in all benthic communities surveyed during MEDWAVES. Some examples of coral garden habitats and sponge grounds identified in these areas are presented.

This proposed methodology and preliminary results represent the first steps in a larger study that aims to: (1) characterise the megabenthic communities, the species diversity and their distribution in Ormonde Seamount and Formigas Bank, (2) evaluate the influence of substrate type, flank orientation and the characteristics of the water masses in the patterns observed, and (3) do a comparison between both seamounts to determine differences in their biological composition.