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Abstract: This paper describes the epifaunal macro-invertebrate assemblages of the continental shelf in the eastern Great Australian Bight (GAB) in relation to environmental factors, including water depth and sediment type. Patterns of species composition are used to assess the effectiveness of the Benthic Protection Zone (BPZ) of the GAB Marine Park in representing regional biodiversity. A total of 753kg of benthos belonging to 797 species and 10 phyla were collected in 65 5-min tows using a 1.8m wide and 0.6m high epibenthic sled, fitted with a 50mm mesh bag. Results suggest that the eastern GAB supports one of the world''s most diverse soft-sediment ecosystems. Sessile, suspension-feeding organisms (primarily poriferans, ascidians and bryozoans) dominated samples, and collectively comprised over 96% of the biomass and 74% of the species collected. Correlation analyses revealed a significant positive relationship between species richness and biomass and highlighted a general decline in both parameters with increasing depth and percentage mud in sediments. Six epifaunal assemblages identified in this study were correlated with depth and sediment type. Large total biomasses and high numbers of species were recorded in inner shelf waters of the western Eyre Peninsula, which support high levels of plankton production, and at the Head of the Bight, where sediments are fine grained. All six of the assemblages and 54% of the species collected were found in the BPZ, suggesting that the zone may effectively represent the epifaunal assemblages of the continental shelf in the eastern GAB. [Copyright &y& Elsevier]

Abstract The Great Australian Bight (GAB) is important ecologically due to a diverse benthic fauna with high endemicity, and productivity that supports marine mammals and apex predators. The region is also economically important, supporting valuable fisheries, aquaculture and ecotourism industries. Deep-sea (>200 m depth) exploration leases for oil and gas have also recently been activated. Characterising the environment of the GAB is a priority in light of these activities, but although areas of the GAB continental shelf have been well-studied, there is a paucity of data on benthos from depths > 200 m and a virtual absence of collated benthic ecological information. Predictive ecological modelling is increasingly being used for deep-sea benthic characterisation given the large areas involved and logistic challenges of sampling these environments. For example, species distribution models can be used to predict environmental suitability in unsampled areas, and to inform spatial management for data-poor regions. We explored options and selected the maximum likelihood implementation of the popular MaxEnt method to predict environmental suitability for 96 deep-water benthic species across temperate Australia. Occurrence records were obtained from a collation of historical museum records, online databases and recent sampling in the GAB at 200–3000 m. Aggregated predictions were used to identify patterns of suitability across species. The GAB continental slope had high relative suitability across all modelled species, particularly in the phyla Chordata and Cnidaria, while predicted suitability for species in the phyla Mollusca and Arthropoda was generally higher on the east than south coast of Australia. These patterns were influenced by the suite of species used; we found predicted suitability within the GAB to be negatively influenced by the proportion of east coast records per species. Average bottom temperature, which correlated with depth and a range of water quality variables, was the most important environmental predictor of suitability. The currently poorly-sampled upper mid-slope depths (500–800 m) of the GAB had the greatest predicted suitability across the suite of modelled species; hence recent sampling of the GAB benthos may have underestimated benthic faunal abundance and diversity in this region. [ABSTRACT FROM AUTHOR]

Abstract The first systematic benthic survey in the deep sea (200–3000 m) of Australia's Great Australian Bight (GAB) was undertaken in 2015 to characterise the invertebrate megafauna, and to inform the selection of indicators and metrics for ecological monitoring ahead of oil and gas exploration. The survey yielded more than 629 species of invertebrate megafauna; of the 376 species with distributional data, 92 (25%) were undescribed and 77 were new records for Australian waters. The families and genera present were all known to occur in the deep sea and many species had been previously recorded in Australia and worldwide; faunal composition was broadly typical for temperate deep-sea regions. The highest diversities (>80 putative species, or Operational Taxonomic Units, OTUs) were recorded within the higher taxa Demospongiae, Decapoda, Gastropoda and Echinodermata. Multispecies analyses showed clear changes in the assemblage structure with depth; sponges and echinoderms dominated the overall biomass and density, with the former being more prominent in shallower depths. The assemblage structure is consistent with the GAB being a single provincial-scale bioregion, with no longitudinal pattern in assemblage, biomass or density distribution. Approximately 70% of species that could be assigned biogeographic data were previously recorded from Australia, with less than half (146 species, 39%) previously known from the GAB. Only two described species, the crab Choniognathus granulosus and barnacle Arcoscalpellum inum, appear restricted to the GAB; it would be premature to assign any undescribed species as having endemic status. The clear eastwards biogeographic affinity of the GAB fauna is influenced by the relatively high deep-sea sampling effort to the east off southeastern Australia and New Zealand. Our survey of invertebrate megafauna at baseline (unperturbed) sites provides the basis to evaluate indicators and metrics using a reference-site monitoring approach. A robust (consistent species-level) taxonomic foundation will enable a variety of assemblage-level (composite) metrics (e.g. richness, diversity, distinctness) to be derived, and this is possible across several major taxa including Porifera, Cnidaria, Mollusca, Echinodermata and Crustacea. Species-level data also permit structural and functional changes (including recovery) to be assessed in response to disturbance. Where reference sites should be established can only be determined once the exploration phase of industry development is further advanced because the spatial scales of potential impact are highly activity-specific. However, our data show the high importance of depth to selecting monitoring sites because invertebrate megafaunal assemblage composition (turnover), diversity, and abundance are all highly correlated with depth. Conversely, latitude is not important because the central GAB is a single biogeographic province. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we describe the composition and distribution of benthic macro-biota in Spencer Gulf, South Australia, and evaluate the contributions of prawn trawling effort and local environmental factors to observed spatial patterns. Quantitative samples of benthos were obtained from 120 sites using commercial prawn trawling gear, and 4.2tonnes of benthos belonging to 395 species and 12 phyla collected. Fish, prawns and crabs dominated the catch and together comprised 96% of the total abundance and 82% of the total biomass. These motile taxa also represented 38% of the total species richness. Overall catch weights were strongly correlated with abundance, and both parameters were highest on the western side of the Gulf where nutrient-rich water from the shelf flows inwards. In contrast, species richness was highest in the east where nutrient-depleted water flows out of the Gulf. A combination of univariate (ANOVA) and multivariate (MDS, ANOSIM) statistical techniques were used to evaluate possible trawl-related impacts on individual species, species groupings and communities. ANOVA tests showed no significant (p <0.05) trawl-related differences in overall species richness, abundance or biomass. Individual species did, however, show significant but contradictory patterns in relation to historical trawling effort. The abundances and biomasses of 6 of the 20 most common species were significantly (p <0.05) higher on the most intensively trawled grounds, while 5 of the 20 most common species were significantly (p <0.05) lower. ANOVA tests were also applied to species grouped by phyla to evaluate their susceptibility to past trawling effort. These tests confirmed that sponges, bryozoans and fish were significantly (p <0.05) less prevalent on the heavily trawled areas. Despite such differences, MDS showed that benthic communities were similar at sites with different trawling histories. These same multivariate techniques also confirmed that putative trawl-related differences in community structure were small when compared to those associated with latitude. A strong environmental gradient was identified between the north and south of the Gulf, and effectively overwhelmed any trawl-related differences in benthos. This gradient was classified into four geographical regions supporting different biotic assemblages. Latitude and depth accounted for most () of this spatial variation in community structure, but it is likely that other unmeasured factors play an important role in structuring the benthic biota of the Gulf. [Copyright &y& Elsevier]