2021 State of the Environment Report Marine Chapter – Expert Assessment – State and Trend – Primary production

Researchers: Emma Flukes (Point of contact) ,  Matear, Richard (Author) ,  van Ruth, Paul (Author) ,  van Ruth, Paul (Author)

Brief description 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 primary production". ***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 - Primary Production"*** ---------------------------------------- DESCRIPTION OF TAXONOMIC GROUP FOR EXPERT ASSESSMENT Primary productivity is the process by which phytoplankton convert dissolved inorganic carbon into the organic compounds that underpin the marine food web through photosynthesis. Rates of primary productivity (PP) and concentrations of phytoplankton biomass (PB, or “primary product”) are dependent upon the available irradiance, and the magnitude and timing of nutrient supply. The magnitude of primary productivity in the ocean is reduced by the uncoupling of nutrients and irradiance. Globally, warming has increased oceanic stratification, generally reducing PP and PB (Chavez et al., 2011). The more tropical oceans of northern Australia tend to be strongly stratified restricting nutrient resupply from depth (Chavez et al. 2011). In contrast, in certain temperate regions, seasonal coastal upwelling can enrich surface waters and increase primary production. These areas include the eastern Great Australian Bight (van Ruth et al., 2010; 2018), the Bonney Coast off south eastern South Australia and western Victoria (Nieblas et al., 2009), south western Western Australia (Hanson et al., 2005a, b), and the mid and south coasts of New South Wales (Oke and Middleton, 2001; Suthers et al., 2011). Climate projections suggest marine heatwaves in Australian waters will increase in frequency and intensity (Hayashida et al., 2020b; Oliver et al., 2017). Marine heatwaves can significantly impact primary producers by changing phytoplankton biomass and community composition (Hayashida et al., 2020a; Roberts et al., 2019), which can have both beneficial and detrimental effects on the ecosystem (Chiswell and Sutton, 2020). Longer-term, these effects may alter food web dynamics and impact higher trophic levels of the ecosystem. DATA STREAM(S) USED IN EXPERT ASSESSMENT Data are computed from the level 3 (L3) daily global products using one merging method. PP was computed from merged monthly L3 products using the algorithms developed by Antoine and Morel (1996). Details can be found at http://www.globcolour.info/products_description.html ---------------------------------------- 2021 SOE ASSESSMENT SUMMARY [see attached Expert Assessment for full details] • 2021 • Assessment grade: Good Assessment trend: Improving Confidence grade: Adequate Confidence trend: Adequate Comparability: Grade and trend are comparable to the 2016 assessment • 2016 • Assessment grade: Good Assessment trend: 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 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 2016 SOE ASSESSMENT This assessment uses observations same observations but just extended to 2020.

Lineage Statement: QUALITY OF DATA USED IN THE ASSESSMENT Spatial and temporal coverage are excellent. Conversion of ocean colour to primary production by a model introduces a source of potential error. The magnitude of this error has been assessed (e.g. Carr et al. 2006) but further refinement is possible for Australian waters. The assessment of trends should be quite robust to any model error.

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Notes Credit
Peer reviews of this assessment was provided by: Peter Strutton (IMAS)

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