2016 SoE Marine Chapter - State and Trends - Water column, outer shelf (25 m - 250 m)

Brief description

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 habitats and communities - water column, outer shelf (25 m - 250 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.

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DESCRIPTION OF HABITAT/COMMUNITY FOR EXPERT ASSESSMENT
The water column is the primary habitat for pelagic communities that are mainly phytoplankton, bacteria, zooplankton and higher predators (in the ratios of ~300:75:10:1, respectively: Marchant 2002) and their biomass declines exponentially with depth (Rex et al., 2006). The major determinants of habitat quality for most pelagic organisms can be considered to be temperature (T), salinity (S), light, nutrients, dissolved oxygen (DO), pH, and food availability. The continental shelf waters around Australia are generally warm, saline, well illuminated, low in nutrients, and abundances of phytoplankton (Fig. 1), zooplankton (Fig. 2) and fish. Relative to the seasonal variability for the majority of the water column on the outer shelf there have been modest long term changes to these components of the habitat and its communities. Overall its current status should be considered good. The major potential threats that could reduce the existing flora and fauna can be considered to be: inputs from the terrestrial environment (sediments, nutrients, carbon), development, warming, declining [DO], decreasing pH and fishing. While there are areas of local habitat degradation (e.g. near ports and harbours) the overall impacts of local pressures tend to be low as Australia is a large area with a relatively sparse human population. There is increasing evidence our shelf waters are experiencing change due to the global pressures; some of which are deleterious. Shelf waters from Port Hedland to Cape Howe have risen ~ 1°C from 1993 to 2013 (Foster et al., 2014), and portions of the SW region were 3°C warmer during February 2011 than normal (Pearce and Feng 2013). There is evidence that dissolved oxygen has declined (Thompson et al. 2009) and continues to decline due to warming (Talley et al., 2016) plus concerns over acidification continue to grow (Mongin et al., 2016). Already there is clear evidence of community responses by phytoplankton, zooplankton and fish to these climatic pressures (e.g. Johnson et al. 2011).

DATA STREAM(S) USED IN EXPERT ASSESSMENT
Data are computed from the level 3 (L3) daily global products using one merging method following Maritorena and Siegel, (2005). Details can be found at http://www.globcolour.info/products_description.html
Zooplankton data are from Australia’s National Reference Stations operated by the Integrated Marine Observing System.

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2016 SOE ASSESSMENT SUMMARY [see attached Expert Assessment for full details]

• 2016 •
Assessment grade: Good
Assessment trend: Unclear
Confidence grade: Limited evidence or limited consensus
Confidence trend: Limited evidence or limited consensus
Comparability: Grade and trend are somewhat 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

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CHANGES SINCE 2011 SOE ASSESSMENT
This assessment uses observations from a greater range of spatial and temporal scales allowing a much better assessment of current state and trends to be made. There is also a statistical analysis of temporal change in zooplankton biomass.

Lineage

Statement: QUALITY OF DATA USED IN THE ASSESSMENT
Quality of data used in the assessment
Spatial and temporal coverage are excellent. Conversion of ocean colour to chlorophyll a introduces a source of potential error that decreases with depth. Data could be extracted for each region to allow improved regional assessments of state and trend.

Notes

Purpose
To describe the state and trends in the quality of the water column community, outer shelf (25 m - 250 m) for use in the Marine chapter of the 2016 State of the Environment report.