Short Presentation Australian Marine Sciences Association 2026 Conference

Spatial and temporal patterns of surface Trichodesmium occurrence in the Great Barrier Reef from Sentinel-3 OLCI observations: insights and implications (139303)

Yuanning Zheng 1 2 3 , David Blondeau-Patissier 4 , Mostafa Rahimi Azghadi 1 5 , Barbara Robson 2 3
  1. College of Science and Engineering, James Cook University, Townsville, QLD, Australia
  2. Australian Institute of Marine Science, Townsville, QLD, Australia
  3. AIMS@JCU, James Cook University, Townsville, QLD, Australia
  4. CSIRO Environment, Brisbane, QLD, Australia
  5. Centre for AI and Data Science Innovation, James Cook University, Townsville, QLD, Australia

Trichodesmium is a filamentous, nitrogen-fixing cyanobacterium that forms extensive surface blooms in tropical and subtropical oceans. Their occurrences in the Great Barrier Reef (GBR) are well known, but the environmental drivers associated with these blooms have not been comprehensively analysed.

This study uses Sentinel-3 OLCI observations to detect Trichodesmium surface expressions across the GBR over the period 2016 to 2026. A combination of the Maximum Chlorophyll Index (MCI) and Normalised Difference Turbidity Index (NDTI) is applied to reduce false positives, improving the detection reliability of these events.

The resulting dataset is used to quantify spatial patterns and temporal variability of blooms, including their frequency, extent, and seasonal distribution across the GBR over the past decade. These patterns are further examined in relation to environmental variables, including sea surface temperature, wind conditions, and nutrient-related proxies to explore potential drivers of bloom occurrence. Results are compared with earlier satellite-based assessments to evaluate consistency and identify potential changes in bloom patterns over time.

This work provides an updated baseline of Trichodesmium bloom dynamics in the GBR and offers initial insights into their environmental controls, aiming to support future development of predictive frameworks for bloom monitoring and the management of the marine park.