POSTER SESSION 1
15:30–17:30, Monday, September 14
Poster Session | 1 | 2 | 3 | 4 | Schedule at a Glance
ABSTRACT 1207 | POSTER 29
HIGH CHLOROPHYLL EVENTS ALONG THE PERTH COASTLINE
Advances in satellite ocean colour remote sensing have enabled systematic detection of episodic phytoplankton blooms — termed High Chlorophyll Events (HCEs) — revealing their growing threat to marine infrastructure and recreational amenity across urban coastal environments globally. Physical and biological drivers controlling sporadic HCEs in oligotrophic systems, where warm boundary currents typically suppress productivity, remain poorly understood, creating critical gaps in predictive capacity for water security management and recreational area closures. This study examines HCEs along Perth’s southwest coast, Western Australia, where diatom-dominated HCEs threaten seawater desalination operations at Cockburn Sound and Trichodesmium cyanobacteria HCEs disrupt recreational activities at Whitford Lagoon — both occurring despite persistently nutrient-poor conditions sustained by the oligotrophic Leeuwin Current. Daily chlorophyll-a (2018–2025) was derived from Sentinel-3 OLCI Level-2 EFR products at 300 m resolution across two morphologically distinct coastal sites. HCEs were classified using an established dual-threshold percentile-based framework grounded in extreme value theory, distinguishing extreme events (eHCEs) — exceeding both an absolute site-wide 90th percentile (P90) and a monthly climatological 90th percentile (mP90) — from anomalous events (aHCEs) exceeding only the seasonal mP90 baseline. Both sites exhibit bimodal seasonality with morphology-specific drivers: Cockburn Sound HCEs are governed by Swan River freshwater discharge and storm-regenerated bottom nutrients, while Whitford Lagoon HCEs are controlled by hydrodynamic retention near Lal Bank under low-energy conditions and rapidly dissipated by storm flushing. These site-specific mechanisms underpin morphology-resolved predictive models for operational coastal management, safeguarding critical water infrastructure and recreational resources under intensifying climate variability and shifting rainfall regimes.
Varshani Brabaharan*, University of Western Australia, [email protected], https://orcid.org/0000-0001-6841-0987
Charitha Pattiaratchi, University of Western Australia, [email protected], https://orcid.org/0000-0003-2229-6183
Yasha Hetzel, University of Western Australia, [email protected], https://orcid.org/0000-0003-3307-2011
Poster Session | 1 | 2 | 3 | 4 | Schedule at a Glance
