2021 State of the Environment Report Marine Chapter – Expert Assessment – State and Trend – Deepwater corals and sponges (mesophotic, 30-150 m)

The Marine chapter of the 2021 State of the Environment (SoE) report incorporates multiple expert templates developed from streams of marine data. This metadata record describes the Expert Assessment "State and Trend of Deepwater corals and sponges (mesophotic, 30-150 m)". 
<strong><em>A PDF of the full Expert Assessment, including figures and tables (where provided) is downloadable in the "On-line Resources" section of this record as "EXPERT ASSESSMENT 2021 - State and Trend – Deepwater corals and sponges (mesophotic, 30-150 m)"</em></strong>



DESCRIPTION OF SPECIES/HABITAT/COMMUNITY FOR EXPERT ASSESSMENT
Corals and sponges are habitat-forming biota that often enhance benthic biodiversity in deep shelf waters by providing complex structural living spaces for a large number of other species from a variety of taxa (Pitcher et al. 2007a, Buhl-Mortensen et al. 2010, Fromont et al. 2012). Most species of corals and sponges need stable substrata for larva to settle and attachment of adult colonies, thus they are usually not associated with mobile or soft-sediment habitats. However, there are exceptions, with many deeper sediments supporting some sponge structure and sediment specialists such as seapens. While corals are often thought of as being associated with tropical waters, coral species are found throughout Australia’s shelf waters and can make up a significant component of the cold-water assemblage. Coldwater corals include stony corals (Scleractinia), black corals (Antipatharia), and octocorals (Alcyonacea).  

Our knowledge of these taxa in Australian waters below typical diving depths stems mainly from a few broad-scale biodiversity surveys covering the Gulf of Carpentaria (Long et al. 1995; Harris et al. 2007; Bustamante et al. 2011), Great Barrier Reef shelf (Pitcher et al. 2007a), Torres Strait (Pitcher et al. 2007b), Pilbara (Pitcher et al. 2016b, Keesing 2019), southern south-east, north-west, and western south –west regions, and the Lord Howe/ Norfolk ridge area (McEnnulty et al. 2011, Williams et al. 2011, Dunstan et al. 2012) (Table 1). Both corals and sponges were found to be highly diverse with many undescribed species, as well as many ‘unknown’ (sensu Hooper et al. 2013) species (McEnnulty et al. 2011, Fromont et al. 2012, Alderslade et al. 2014). For example, sponges in the GBR were the most diverse group with the highest levels of rarity (Pitcher et al. 2007a) and some of the most abundant sponges discovered were new species (Sutcliffe et al. 2010). In addition, species turn-over between samples was extremely high for both taxa (Schlacher et al. 2007, Fromont et al. 2012, Alderslade et al. 2014). The sponge fauna of NSW shelf waters was reviewed in order to improve our understanding in east coast subtropical and temperate waters (Davis et al. 2010).  

Recently (2008 onwards), IMOS has funded an AUV program that allows repeat photographic surveys to document the cross-shelf distribution of reef associated benthic invertebrate assemblages at a broad set of latitudinally spaced nodes along Australia’s eastern and western coastlines. This program, is allowing long-term monitoring of the state and trend of deep shelf reef sponges and corals at a fixed set of sites and feeds into the SoE assessment. This program is being enhanced in offshore waters by surveys undertaken in the new AMP network, providing a greater spatial framework for assessments. While species identifications are not always possible from such imagery, a national identification framework has been established for consistently annotating this imagery to the finest scale possible (CATAMI Althaus et al. 2015), and initial analyses (e.g. Perkins et al. 2015) demonstrates patterns similar to the biodiversity surveys above, with high diversity and high species turnover between locations samples (e.g. Monk et al., 2016). Both sponges and corals are frequently used as indicators of benthic ‘vulnerable marine ecosystems’ (VME) in conservation planning (FAO 2008, Tracey et al. 2008, Williams et al. 2015).  

The ability of sponges to filter large volumes of water makes them a critical link between the benthos and the overlaying water column (WAMSI 2016), and recent studies of productivity on shallow coral reefs suggest that filter feeding by sponges may account for up to 90% of the trophic coupling between pelagic and benthic ecosystems (DeGoeij et al 2013). Such coupling is equally likely on deeper reefs and temperate latitudes as well. The species-level identification of deepwater sponges has not been standardised across Australian collections at this stage; however, this may be possible in the future through SpongeMaps, an online collaboration tool for sponge taxonomists (Hooper et al. 2013; Hall &amp; Hooper 2014). 

DATA STREAM(S) USED IN EXPERT ASSESSMENT
Data used is outlined in the reports and publications listed in reference section.



2021 SOE ASSESSMENT SUMMARY [see attached Expert Assessment for full details]

• 2021 •
Assessment grade: Good
Assessment trend:  Improving from fishing. Declining due to ocean warming and heatwaves.
Confidence grade: Limited evidence, some consensus
Confidence trend: Limited evidence, some consensus
Comparability: Grade and trend are comparable to the 2016 assessment, but more concern around longer-term warming effects 
• 2016 •
Assessment grade: Good
Assessment trend:  Improving
Confidence grade: Limited evidence, some consensus
Confidence trend: Limited or barely adequate evidence, some consensus
Comparability: Grade and trend are comparable to the 2011 assessment
• 2011 •
Assessment grade: Good
Assessment trend: Stable
Confidence grade: Limited evidence or limited consensus
Confidence trend: Limited evidence or limited consensus 



CHANGES SINCE 2016 SOE ASSESSMENT
No change other than acknowledgement of increasing concern around ocean warming and associated marine heat waves.

Tags: corals, deepwater reefs, expert assessment, sponges, state and trend
Organization: Australian Ocean Data Network