An exceptional occurrence of deep-sea sponges in the region of former Larsen Ice Shelves, Antarctic Peninsula, with the description of two new species

Daniel Buskowiak,Dorte Janussen

doi:10.1007/s12526-020-01134-z

Daniel Buskowiak, Dorte Janussen

Open Access

https://doi.org/10.1007/s12526-020-01134-z

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Abstract

Two new species of deep-sea sponges from the Weddell Sea are described. Both are new to science: a carnivorous Demospongiae species Abyssocladia antarctica sp. nov. and a Hexactinellida species Caulophacus leonieae sp. nov., the latter characterized by a new type of microscleres. Both were sampled at the former Larsen Ice Shelf region, Antarctic Peninsula, that was covered by ice until recent breakup events started in 1995. Abyssocladia Lévi, 1964 and Caulophacus Schulze, 1886 are well-known genera in the deep sea but were discovered here at only 200–300 m depths. The findings support the hypothesis that deep-sea and sub-shelf environments provide similar life conditions. These discoveries should urge us to further investigate areas of disintegrated Antarctic shelf ice as soon as possible, since new trophic conditions may have a severe impact on biodiversity and faunal composition.

Highlights

A demosponge specimen of the genus Abyssocladia Lévi, 1964 was collected during the ANT-XXIII/8 expedition (23.11.2006–30.01-2007) by RV POLARSTERN in the Antarctic Weddell Sea. (Fig. 1a)
Representatives of the genus Abyssocladia are known from depths of ca. 1000 m (Goodwin et al 2017) down to 6127 m (Vacelet 2006)
The very similar species to Caulophacus leonieae sp. nov., C. (C.) brandtae, was discovered between 1153 and 1223 m depth (Janussen et al 2004). Compared to these abyssal depths, the occurrence at ca. 300 m (C. (C.) leonieae sp. nov.) and ca. 220 m (Abyssocladia antarctica sp. nov.) is truly exceptional and raises the question, why these deep-sea taxa appear in such shallow depths

Summary

Introduction

A demosponge specimen of the genus Abyssocladia Lévi, 1964 was collected during the ANT-XXIII/8 expedition (23.11.2006–30.01-2007) by RV POLARSTERN in the Antarctic Weddell Sea. (Fig. 1a). Due to the collapse of Larsen AB ice-shelves, it became possible to conduct research in this shelf region that has been covered by ice for at least hundreds of years (Scambos et al 2000) This expedition aimed to find answers to changes in biodiversity in the benthic life as well as other direct effects of the ice-. The main objective of the expedition was the investigation of potential effects of the climate change and ice shelf disintegration on ecosystems and biodiversity in the Antarctic region. It was part of the SCAR programme “Biodiversity and Evolution in the Antarctic: The response of life to environmental change” (Knust et al 2012)

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