2016 SoE Marine Chapter - State and Trends - Seabed, abyss (>700 m)

The Marine chapter of the 2016 State of the Environment (SoE) report incorporates multiple expert templates developed from streams of marine data. This metadata record describes the Expert Assessment "The state and trends of quality of habitats and communities – seabed, abyss (&gt;700 m)". The full Expert Assessment, including figures and tables (where provided), is attached to this record. Where available, the Data Stream(s) used to generate this Expert Assessment are accessible through the "On-line Resources" section of this record.

DESCRIPTION OF HABITAT/COMMUNITY FOR EXPERT ASSESSMENT
This specified depth range (&gt; 700 m) aggregates several habitats and communities that are clearly distinct in geological, environmental and biological characteristics: the mid-continental slope, lower slope, continental rise, and abyss.  Bottom fishing, the single biggest pressure on seabed habitats, is restricted to mid-slope depths (700-1500 m) (e.g. Pitcher et al. in review); oil and gas activity (or planned activity) extends across the continental slope and rise in restricted locations, e.g. the Great Australian Bight (GAB). 
Over 70% of Australia’s marine estate lies beyond 700 m depth; by region the percentage of planar area is &gt;70% for all regions except the GBR (19%), north-west (51%) and the north (0%). The mid-slope 700-1500 m is a steep, narrow band comprising only comprising only 10% of the planar area. Habitats of the mid-slope have been studied through imagery and sampling as part of extensive biodiversity surveys off Western Australia, southern Tasmania and off shore in the Lord Howe Rise (Williams et al. 2010, McEnnulty et al. 2011, Williams et al. 2011, Zintzen et al. 2011, Althaus et al. 2012; Harris et al 2012); habitats beyond 1500 m have been little studied so far, with the exception of the western Australian margin (Daniell et al 2010). Considering the zonation of impacts and knowledge, our assessment is structured into mid-slope and remaining depths.
The temperate mid-slope is used by fisheries targeting deep sea sharks, orange roughy and oreos. Although substrates are predominantly muddy and extensive, hard substrates in these depths support biogenic habitats formed by attached fauna such as cold-water corals and glass sponges (separate SER). Fauna was believed to be sparse in abyssal depths, however, recent sampling in depths to 4000 m in the Tasman Fracture zone in the south-east region discovered corals and a high biomass community of large barnacles and anemones on steep rockwalls (Thresher et al. 2014). In contrast seafloor images and limited sampling from Daniels et al 2009 found very little fauna along the western margin, even on expanses of basalt rock walls. Benthic communities of soft sediments below 700 m depth are dominated by small-bodied infauna (worms and crustaceans) sampled in sediment grabs or cores and evident through traces (Lebensspuren) in low-disturbance abyssal environment (Przeslawski et al 2012), and patchy distributions, including dense aggregations, of echinoderms (urchins, sea cucumbers or ophiuroids) (MNF 2015a &amp; b, unpublished data). 
DATA STREAM(S) USED IN EXPERT ASSESSMENT
This assessment is based on data derived from Marine National Facility Surveys described in MarLIN (http://www.marine.csiro.au/marlin/search.html) and accessible through the CSIRO Data trawler (http://www.cmar.csiro.au/data/trawler/). Links to specific data sets are provided in the "On-line resources" section of this record.
• Voyage of Discovery north-west (SS05/2007)
• Voyage of Discovery south-west (SS07/2005 &amp; SS10/2005)
• Great Australian Bight Deepwater Marine Program (GABDMP 2016) (IN2015_C01)
• Great Australian Bight Research Program (GABRP 2016) (SS2013_C02 &amp; IN2015_C02)
• Habitat Mapping (SS01/2000, SS04/2004)
• Habitat and population assessment of giant crabs (2003 - 2005) 
• Tasmanian seamounts surveys, including samples on the slope (SS02/2006 &amp; SS02/2007)
• NORFANZ survey of Lord Howe Rise and Norfolk Ridge (TAN0308 - NORFANZ)

2016 SOE ASSESSMENT SUMMARY [see attached Expert Assessment for full details]
• 2016 •
Assessment grade: Good
Assessment trend: Stable
Confidence grade: Limited evidence or limited consensus
Confidence trend: Limited evidence or limited consensus
Comparability: Grade and trend are comparable to the 2011 assessment
• 2011 •
Assessment grade: Very good
Assessment trend: Stable
Confidence grade: Limited evidence or limited consensus
Confidence trend: Limited evidence or limited consensus

CHANGES SINCE 2011 SOE ASSESSMENT
N/A

Tags: abyssal depth, benthic habitat, expert assessment, seafloor
Organization: Australian Ocean Data Network