2016 SoE Marine Chapter - State and Trends - Seamounts

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 – Seamounts". 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
Seamounts (undersea mountains, often with volcanic origin) provide ‘oasis’ habitats of hard substratum and are widely considered to represent sites of elevated biomass and productivity in the deep ocean. Their habitats can support dense aggregations of corals and associated high biodiversity; these represent vulnerable marine ecosystems (VME) (e.g. UNGA 2006; Clark et al 2011). The geological definition of a seamount (elevation of &gt;1000 m) has no relevance to biodiversity valuation because smaller features are frequently found to support high, if not the highest, biodiversity. An ecological definition (e.g. Pitcher et al. 2007) is recommended.
Australia’s marine realm encompasses many seamounts; the best known are the Tasmanian seamounts and the Tasmantid seamount chain. Additional seamounts have been discovered and mapped on the Lord Howe Rise and the Norfolk Ridge, as well as on Australia’s southern margin in the GAB.
Seamount communities to ~1500 m depth in the south-east and south-west regions are associated with biogenic habitats formed mostly by the stony coral Solenosmilia variabilis (Koslow et al 2000; Thresher et al. 2014). Its matrix of dead and life coral, built up to a layer of at least 1.6 m thickness in places, forms a habitat for other corals, urchins, brittle- and snakestars and crustaceans (Thresher et al. 2014). Communities and habitats on deeper reaches of seamounts (&gt;1500 m) are less well studied; they are usually less diverse and sparser, although areas of extraordinary high biomass have been observed in the south-east region (Thresher et al. 2014). The seamounts in the Tasmantid chain are mapped and well used by various commercial fisheries, but their epifaunal communities remain poorly documented (Williams et al. 2012).
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)
• Tasmanian seamounts surveys (SS01/2000, SS04/2006 &amp; SS02/2007, SS01/2008 &amp; TT01/2008)
• Habitat Mapping (SS01/2000, SS04/2004)
• Habitat and population assessment of giant crabs (2003 - 2005) 
• 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: Very good-Poor
Assessment trend: Stable- Improving
Confidence grade: Adequate high quality evidence and high level of consensus
Confidence trend: Adequate high quality evidence and high level of consensus
Comparability: Grade and trend are somewhat 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
There is substantial information on the impact of trawling on seamounts in the South-East Marine Region available.

Tags: biogenic habitat, epifaunal community, expert assessment, seamounts
Organization: Australian Ocean Data Network