New unknown Bryozoa genera and species below thousand meters deep in the Southwestern Atlantic

Bryozoa are aquatic and colonial invertebrates that can produce mineralized skeletons. This is the study with the largest identification of new bryozoan species below a thousand meters deep -- that is, in the continental slope -- in the Argentine Patagonia, an area where most of the identified species had been found above five hundred meters. The new species were collected during five oceanographic campaigns -from 2008 to 2010- of IEO's ATLANTIS Project, on board the research vessel Miguel Oliver (Spanish Secretary-General for Fisheries), and obtained from 25 sampling sites, between 138 and 1650 meters deep, in the Southwestern Atlantic.

In big ocean currents

This area is one of the most productive marine ecosystems in the Southern Hemisphere due the confluence of two of the most powerful wind-driven currents: the Falkland Current -very rich in nutrients- and the subtropical Brazil Current. In particular, the current of the Malvines is a branch of the Antarctic Circumpolar Current, which flows northward along the continental shelf of Argentina -under 800 or 1000 meters- to about latitude from 30º to 40º S, where it is deflected eastward after meeting the warm southward-flowing Brazil Current," says Blanca Figuerola (UB-IRBio), who is now collaborating with the team led by Aaron O'Dea in the Smithsonian Tropical Research Institute (STRI) in Panama.

When these powerful marine currents converge, there is a high biological production, promoting the growth of benthic invertebrates. "Therefore, this area is dwelled by particular species with a wide range of distributions and adaptations to fluctuating conditions, resulting from the influence of these subtropical and subantarctic waters," adds Figuerola.

The findings of two genera (Amynaskolia and Biconcavus) and twenty new species add new chapters to the inventory of the regional biodiversity of Bryozoa in the Southwestern Atlantic. "In these areas, studies on the biodiversity of marine invertebrates are needed, mainly at slope and abyssal depths. For now, some of the best-known benthic invertebrates in this region are molluscs, echinoderms and cnidarians," says the researcher.

Biconcavus batmani: remembering the superhero

Some discovered species belong to genera from which only two species were known: in particular, the Ipsibuffonella umbonata, Membranicellaria balanyai -named after Professor Joan Balanyà, from the Faculty of Biology and IRBio- and Mawatarius avilae, which pays tribute to the lecturer Conxita Ávila (UB-IRBio), head of the projects Distantcom, Ecoquim and Actiquim -on the chemical ecology of marine invertebrate communities in the Antarctica in which the researchers Blanca Figuerola and Javier Cristobo also took part.

Curiously, the species Biconcavus batmani, which appears among the scientific findings, possesses lateral formations that resemble the mask of the fictional superhero of the comic books and movies, Batman. In the case of Malakosaria cecilioi -known species from the Malakosaria genus- each zooid or individual from this colony presents two oval excavations and one ascopore -which looks like a smiling face. All these new specimens that were found by the scientific team were deposited at the Animal Biodiversity Resource Center (CRBA) of the UB, with its headquarters at the Faculty of Biology of the UB.

The unknown biodiversity in the continental slope and abyssal plain

Studying the biodiversity in the continental slope and the abyssal plain of the Patagonian and Antarctic regions is essential to complete the taxonomy and biogeography of some lineages that inhabit these unique ecosystems. The new findings will also provide new views on the study of comparative diversity among invertebrate communities from the last separated fragments of Gondwana, the ancient supercontinent. This is, for example, the case of Spigaleos genus and the species Arachnopusia tubula, which were previously reported only from Antarctica; the genera Ipsibufonella, previously known to be only in tropical and subtropical areas, and Mucropetraliella, which was identified in areas outside the Patagonia.

According to Blanca Figuerola, "the findings of Arachnopusia tubula in the Patagonia -a species that shows a wide bathymetric range- supports our hypothesis on the polar front which was stated in previous studies. This oceanographic barrier -the limit between the Austral Ocean and its surrounding waters- is not as impermeable as originally thought. Therefore, bryozoan colonies can be attached to drifting natural substrates or marine debris of anthropogenic origin (algae, plastics, etc.), and can spread fast through rafting (moving on floating objects) at a regional or global level."

The discovery of new marine invertebrate species in South America has rapidly increased since mid-18th century. The new species of the research study were found in the area of eastern Patagonia. In other studies that were published in journals such as Journal of Sea Research (2014) and Marine Environmental Research (2017), the UB-IRBio researcher and other experts contributed to enlarge the catalogue of the benthic fauna in the South Atlantic with the identification of more than 180 bryozoan species.

"Many studies on the biodiversity in the area of the continental slope and abyssal plains are to be done yet. We know some bryozoan genera can incorporate significant amounts of magnesium to their skeletons; therefore they are more soluble and more susceptible to the oceanic acidification than skeletons containing lower magnesium levels. It will be necessary to carry out studies on the distribution, abundance and mineralogy to assess whether these species are suitable as model organisms to study the effects of climate change in oceans," concludes Blanca Figuerola.