Diversity and community structure of Cheilostomata (Bryozoa) from the Hayes Fracture Zone, Mid-Atlantic ridge

• Published in: Deep-sea research. Part I, Oceanographic research papers Oceanographic research papers, 2019-05, Vol.147, p.32-53
• Main Authors: Souto, Javier, Albuquerque, Mónica
• Format: Article
• Language: English
• Subjects: Biodiversity; Biogeography; Deep sea distribution; Deep waters; Detritic habitats; Rocky bottoms
• ISSN: 0967-0637; 1879-0119
• DOI: 10.1016/j.dsr.2019.03.006

Previous work on deep-water bryozoans in the North Atlantic have focused mainly on the northeast Atlantic, and only a few, earlier papers examined the bryozoans from deep water close to the Azores Islands. This is the first report on cheilostome bryozoans from the Mid-Atlantic ridge. The remotely operated vehicle (ROV) LUSO was used to collect samples during the campaign EMEPC/PEPC/LUSO2016. Bryozoan specimens were collected from nine sampling points distributed on two localities along the Hayes Fracture zone of the Mid-Atlantic ridge. These localities are between 1072 m and 1474 m deep and represent two habitats types: rocky bottoms and detritic bottoms. Abiotic data (depth, temperature, salinity, O2 saturation, mg/l of O2 compensated by salinity and pressure, turbidity and fluorescence) were collected to characterize the sampling points. Fifteen species of bryozoans were identified, of which seven are described for the first time and three remain in open nomenclature but probably also involve unknown species. This represents more than 50% of the unknown species, which is similar to data from other deep-water areas such as seamounts. Biogeographically, closer affinities were determined with species from the North Atlantic, but genera from the South Atlantic or with stronger Pacific affinities were also found. Two different communities were detected but they were not dependent on the habitat type. We attribute this to the stability of and low sedimentation at these deep-water detritic bottoms. Positive correlations between these species assemblages and abiotic variables were found only for depth, temperature, O2 saturation and mg/l of O2. Nonetheless, only temperature and depth apparently influence community type, although, as in previous studies on other faunas from the Mid-Atlantic ridge, other variables not considered here could have influenced bryozoan distribution. •Cheilostomata diversity is studied for first time in the Hayes Fracture, in the Mid-Atlantic ridges.•Fifteen species of Cheilostomata (Bryozoa) are recorded from Hayes Fracture, with the description of seven new species.•More than the 50% of the found diversity was unknown until now, similar data to other deep waters habitats as seamounts.•Communities were found not dependent of the habitat type, but with positive correlation with the temperature and depth.