Deep-sea ROV video analysis used to characterize Vulnerable Marine Ecosystems at Gazul Mud Volcano (NE Atlantic)

Master Thesis. Submitted in partial fulfillment of the requirements for the Master degree of Coastal Marine Biology and Ecology.

Abstratc: 

In today’s marine research, a knowledge gap still remains in understanding deep-sea habitats and those animals that live in them. The occurrence and distribution of benthic organisms were investigated by assessing the Gazul Mud Volcano (GMV) ecosystems at ~ 400 - 500 m depth, in the Gulf of Cadiz (NE Atlantic, Spain). Scientific research still remains limited at this specific mud volcano, with regards to understanding the various types of it’s deep-sea communities and quantifying the structuring species.
Our study aims to fill these gaps and better understand the Vulnerable Marine Ecosystems (VMEs) located at Gazul. A total of 745 colonies / individuals were counted including 7 phyla and 46 Operational Taxonomic Units (OTUs) along a video transect recorded by a Remote Operated Vehicle (ROV). Important VME indicator organisms such as scleractinian CWCs Madrepora oculata, Lophelia
pertusa (0.033 ind · m-2 combining both species), the alcyonacean Acanthogorgia spp. (0.096 ind · m- 2) and hexactinellid sponge Asconema setubalense (0.020 ind · m-2 were observed at considerable densities. Certain commercially important species showed to be frequent (e.g. E. cirrhosa and Scyliorhinus canicular) and three different locations of fishing impacts were observed (e.g. trawling nets, fishing lines, debris). The distribution of CWCs and deep-sea sponges formed dense aggregations into four main clusters along the transect, which were dominated by different substrate and community composition. This study identifies different VMEs and/or VME indicator organisms at the GMV and provides detailed information that might help to implement future protection and conservation plans in the overlooked area.