Background: The Great Australian Bight (GAB) comprises the majority of Australia's southern coastline, but to date its deep water fauna has remained almost unknown. Recent issuing of oil and gas leases in the region has highlighted this lack of baseline biological data and established a pressing need to characterise benthic abyssal fauna. Methods: From 2013 to 2017, six large-scale systematic surveys of the GAB were conducted from 200 to 5000 m depth, constituting the deepest systematic biological sampling in Australia. Sampling was conducted on soft sediment and hard substrates, both at predetermined depth intervals along north-south transect lines and at sites of interest identified by multibeam sonar. Results: A total of 66,721 invertebrate specimens were collected, comprising 1267 species, with 401 species (32%) new to science. In addition to the novelty of the fauna, there was a high degree of rarity, with 31% of species known only from single specimens. Conclusions: In this paper, we provide an annotated checklist of the benthic invertebrate fauna of the deep GAB, supplemented with colour photos of live specimens and commentary on taxonomy, diversity and distributions. This work represents an important addition to knowledge of Australia's deep sea fauna, and will provide the foundation for further ecological, biogeographical and systematic research.

Four new species of the families Hemioniscidae and Crinoniscidae are described from New Zealand waters: Crinoniscus politosummus sp. nov., C. cephalatus sp. nov., Scalpelloniscus vomicus sp. nov. and S. nieli sp. nov. Mature males and females are described for all species, and the epicaridium larva is described for S. vomicus sp. nov. Males of the two species of Scalpelloniscus can be distinguished from S. penicillatus and S. binoculis by coxal plate dentition, relative sizes of propodus and dactylus. Crinoniscus politosummus sp. nov. and C. cephalatus sp. nov. can be separated from the only other congener Crinoniscus equitans by the body shape of the mature females, and shape of antennule article 1 of the males. A single specimen tentatively identified as S. cf. penicillatus is also recorded from New Zealand waters. These species are the first records of cryptoniscoid isopods infecting thoracic barnacles from the South West Pacific.

A growing body of evidence indicates that temperate marine ecosystems are being tropicalised due to the poleward extension of tropical species. Such climate mediated changes in species distribution patterns have the potential to profoundly alter temperate communities, as this advance can serve to push temperate taxa, many of which are southern Australian endemics, southward. These changes can lead to cascading effects for the biodiversity and function of coastal ecosystems, including contraction of ranges/habitats of sensitive cool water species. Hence there is growing concern for the future of Australia's temperate marine biodiversity. Here we examine the diversity and abundance of marine flora and fauna at two reefs near Perth's metropolitan area-Minden Reef and Roe Reef. We report the presence of 427 species of marine flora and fauna from eight taxon groups occurring in the Perth metropolitan area; at least three species of which appear to be new to science. Our data also extends the known range of 15 species, and in numerous instances, thousands of kilometres south from the Kimberley or Pilbara and verifies that tropicalisation of reef communities in the Perth metropolitan area is occurring. We report the presence of 24 species endemic to southwest Australia that may be at risk of range contractions with continued ocean warming. The results of these surveys add to our knowledge of local nearshore marine environments in the Perth metropolitan area and support the growing body of evidence that indicates a diverse and regionally significant marine fauna occurs in temperate Western Australia. Regular, repeated survey work across seasons is important in order to thoroughly document the status of marine biodiversity in this significant transition zone.

This study represents the first ROV-based exploration of the Perth Canyon, a prominent submarine valley system in the southeast Indian Ocean offshore Fremantle (Perth), Western Australia. This multi-disciplinary study characterizes the canyon topography, hydrography, anthropogenic impacts, and provides a general overview of the fauna and habitats encountered during the cruise. ROV surveys and sample collections, with a specific focus on deep-sea corals, were conducted at six sites extending from the head to the mouth of the canyon. Multi-beam maps of the canyon topography show near vertical cliff walls, scarps, and broad terraces. Biostratigraphic analyses of the canyon lithologies indicate Late Paleocene to Late Oligocene depositional ages within upper bathyal depths (200-700 m). The video footage has revealed a quiescent 'fossil canyon' system with sporadic, localized concentrations of mega-and macrobenthos (∼680-1,800 m), which include corals, sponges, molluscs, echinoderms, crustaceans, brachiopods, and worms, as well as plankton and nekton (fish species). Solitary (Desmophyllum dianthus, Caryophyllia sp., Vaughanella sp., and Polymyces sp.) and colonial (Solenosmilia variabilis) scleractinians were sporadically distributed along the walls and under overhangs within the canyon valleys and along its rim. Gorgonian, bamboo, and proteinaceous corals were present, with live Corallium often hosting a diverse community of organisms. Extensive coral graveyards, discovered at two disparate sites between ∼690-720 m and 1,560-1,790 m, comprise colonial (S. variabilis) and solitary (D. dianthus) scleractinians that flourished during the last ice age (∼18 ka to 33 ka BP). ROV sampling (674-1,815 m) spanned intermediate (Antarctic Intermediate Water) and deep waters (Upper Circumpolar Deep Water) with temperatures from ∼2.5 to 6 • C. Seawater CTD profiles of these waters show consistent physical and chemical conditions at equivalent depths between dive sites. Frontiers in Marine Science | www.frontiersin.org 1 April 2019 | Volume 6 | Article 173 Trotter et al. Perth Canyon Deep-Water Coral FaunaTheir carbonate chemistry indicate supersaturation ( calcite ∼ 1.3-2.2) with respect to calcite, but mild saturation to undersaturation ( aragonite ∼ 0.8-1.4) of aragonite; notably some scleractinians were found living below the aragonite saturation horizon (∼1,000 m). Seawater δ 13 C and nuclear bomb produced 14 C compositions decrease in the upper canyon waters by up to ∼0.8 (<800 m) and 95 (<500 m), respectively, relative to measurements taken nearby in 1978, reflecting the ingress of anthropogenic carbon into upper intermediate waters.