A new record of the bryozoan Melicerita blancoae near the Mar del Plata Submarine Canyon reveals a latitudinal and bathymetric range extension of the species

The deep ocean remains one of the least explored environments on Earth, and knowledge of the benthic fauna inhabiting Argentine waters is still scarce. Characterizing deep-sea biodiversity is essential to support both the sustainable use of marine resources and the conservation of deep-sea ecosystems. Bryozoans are colonial invertebrates widely distributed in marine benthic environments. They play an important ecological role creating complex biogenic structures characterized by high productivity, diversity and numerous ecosystem services. However, knowledge of deep bryozoan species remains, in proportion, exceedingly sparse. Species of the genus Melicerita are restricted to temperate-cold and cold waters of the Southern Hemisphere. Previously, Melicerita blancoae was known mostly from the Patagonian shelf to the bathyal waters south of 50ºS, at depths ranging from 74 to 780 m. Samples obtained during the expedition Talud Continental I, conducted in 2012 aboard the R/V Puerto Deseado, allowed the analysis of bryozoan material, detecting the occurrence of M. blancoae at 852 m depth in waters adjacent to the Mar del Plata Submarine Canyon (37° 59,706’ S - 54° 41,854’ W), placed off Buenos Aires Province. This new record contributes to the knowledge of the diversity around the Mar del Plata Submarine Canyon, expanding the geographic distribution of M. blancoae northward by ~13 degrees of latitude (ca. 1443 km) and its bathymetric range by 72 m. The geographic distribution of this species appears to be related to the Malvinas Current, whose northward flow converges with the Brazil Current at the Mar del Plata Submarine Canyon, forming the Brazil-Malvinas Confluence. This finding highlights the importance of sampling the deep waters along South America to fill significant gaps in the knowledge of bryozoan diversity and distribution patterns.