2021 State of the Environment Report Marine Chapter – Expert Assessment – State and Trend – Harmful algal blooms

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 Harmful Algal Blooms". 
<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 – Harmful Algal Blooms"</em></strong>



DESCRIPTION OF PROCESS FOR EXPERT ASSESSMENT
Harmful Algal Blooms (HABs) are multifaceted, comprising a wide range of phenomena caused by some 150 different marine organisms – most of which are phytoplankton – that can have negative socio-economic impacts on humans and the marine environment. These include: (i) water discolourations, scum or foam, e.g. Noctiluca scintillans red tides closing beaches; (ii) biotoxin accumulation in seafood above levels considered safe for human consumption, e.g. Paralytic Shellfish Toxins (PSTs) by Alexandrium pacificum in NSW in 2016, in the Swan-Canning Rivers in 2019-2020, and Alexandrium catenella in Tasmania in 2016 and 2017 (toxins in mussels 200 times above regulatory level); in both cases resulting in shellfish or other invertebrate (abalone, rock lobster) harvesting bans; and (iii) any other event where humans, animals or other organisms are negatively affected by algae, e.g. ciguatera poisoning from recreational fish caught in northern NSW (Fig.1). 

DATA STREAM(S) USED IN EXPERT ASSESSMENT
Data for the iconic HAB events in Australia are catalogued in the Harmful Algae Event Database,  HAEDAT, http://haedat.iode.org. To analyse the range increase, time series and seasonal cycle in Noctiluca scintillans we used the IMOS Australian Continuous Plankton Recorder survey data, see Richardson et al. (2006) for detailed methodology, the IMOS National Reference Station data and the data collated through the Australian Phytoplankton Database, see Davies et al. (2016). This last dataset also contains the HAB monitoring program, samples analysed by Steve Brett at Microalgal Services for the NSW food authority which have been used to look at the time series of potentially toxic microalgae.



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

• 2021 •
Assessment grade: Very good
Assessment trend: Stable
Confidence grade: Somewhat adequate
Confidence trend: Somewhat adequate
Comparability: Grade and trend comparable to the 2016 assessment.
• 2016 •
Assessment grade: Very good
Assessment trend: Stable
Confidence grade: Limited evidence or limited consensus
Confidence trend: Limited evidence or limited consensus
Comparability: Grade and trend 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 2016 SOE ASSESSMENT
The assessment has not changed since 2016 but this assessment has used longer time series information to provide a higher level of confidence.

Tags: expert assessment, harmful algal blooms
Organization: Australian Ocean Data Network