The lower bathyal and abyssal seafloor fauna of eastern Australia

Abstract

Background Our knowledge of the benthic fauna at lower bathyal to abyssal (LBA, > 2000 m) depths off Eastern Australia was very limited with only a few samples having been collected from these habitats over the last 150 years. In May–June 2017, the IN2017_V03 expedition of the RV Investigator sampled LBA benthic communities along the lower slope and abyss of Australia’s eastern margin from off mid-Tasmania (42°S) to the Coral Sea (23°S), with particular emphasis on describing and analysing patterns of biodiversity that occur within a newly declared network of offshore marine parks. Methods The study design was to deploy a 4 m (metal) beam trawl and Brenke sled to collect samples on soft sediment substrata at the target seafloor depths of 2500 and 4000 m at every 1.5 degrees of latitude along the western boundary of the Tasman Sea from 42° to 23°S, traversing seven Australian Marine Parks. Results The biological sampling included 35 beam trawls, 28 Brenke sleds, 8 box cores, 20 surface meso-zooplankton tows, and 7 Deep Towed Camera transects. In total, 25,710 specimens were identified to 1084 taxonomic entities, including 847 species-level, 144 genus-level and 69 family-level and 24 higher-level taxa. Of the species-level taxa, only 457 were assigned species-level taxonomic names, which implies that up to 58% of the collected fauna is undescribed. In addition, the ranges of numerous species have been extended to include the western Tasman Sea. Conclusions The lower bathyal and abyssal fauna of soft sediment seafloors off eastern Australia has been systematically surveyed for the first time. The resultant collections will provide the foundation for much future ecological, biogeographical, phylogenetic and taxonomic research.

Annelids of the eastern Australian abyss collected by the 2017 RV ‘Investigator’ voyage

“…Prior to 2017, only two annelid species were described from the region below 2000 m, consequently this work vastly increases our knowledge of deep-water annelids and provides critical baseline data on an important group of benthic invertebrates from a virtually unknown region of the world’s ocean. This is important as comprehensive taxonomically-consistent deep-water datasets that cover large areas in Australia are rare ( O’Hara 2008 ; Alderslade et al 2014 ; Althaus et al 2017 ; MacIntosh et al 2018 ; Williams et al 2018 ; Farrelly and Ahyong 2019 ; Ekins et al 2020 ; O’Hara et al 2020a , b , c ), in particular for smaller benthic invertebrates ( Poore et al 2015 ), which highlights the uniqueness of this dataset.…”

Deep Downunder: Integrative taxonomy of Austrobela , Spergo , Theta and Austrotheta (Gastropoda: Conoidea: Raphitomidae) from the deep sea of Australia

“…Theta microcostellata , T . polita , Au strotheta crassidentata and Au strotheta wanbiri may therefore represent additional relatively rare species, as the regions in which they have been collected are comparatively well‐sampled (MacIntosh et al, 2018; O’Hara et al, 2020), with a diverse raphitomid fauna (Criscione et al, 2021). Conversely, most Austrobela species studied here, notably A .…”

“…While any inference of rarity will inevitably, to some extent, be an artifact of sampling, there is evidence that many turriform conoidean species are comparatively rare based on their scarcity in reasonably wellsampled areas (Castelin et al, 2011). Bouchet et al (2009) O'Hara et al, 2020), with a diverse raphitomid fauna . Conversely, most Austrobela species studied here, notably A. rufa, A. levis and A. obliquicostata, can be considered relatively common, as is the case for T. lyronuclea.…”

“…In the deep sea, notably in the Australasian region, recent research suggests that the family Raphitomidae is the most diversified conoidean family (Criscione et al, 2021; MacIntosh et al, 2018; O'Hara et al, 2020). Criscione et al (2021) showed that widespread shell homoplasy among this fauna had led taxonomists to incorrectly attribute a considerable number of unrelated species to very few raphitomid genera (such as Pleurotomella Verril, 1872 and Gymnobela Verrill, 1884), some of which were shown to be polyphyletic.…”

Editorial: Recent and emerging innovations in deep-sea taxonomy to enhance biodiversity assessment and conservation

“…Australia has a very extensive continental slope, but sampling at this depth in the region has been remarkably limited (McCallum et al, 2015;Poore et al, 2015;O'Hara et al, 2020). Very few samples have been taken especially the Australian Exclusive Economic Zone (EEZ), which has been shown to have a highly diverse fauna (Poore et al, 2015;O'Hara et al, 2020). The focus of the study by Błazėwicz et al were tanaidacean crustaceans of the genus Pseudotanais collected from the southern Australian slope.…”