The Great Southern Reef is a system of interconnected kelp reefs that runs along the southern half of Australia. On the west coast, the reef runs from north to south, extending over 800 km in latitude. The northern range edge was highly fragmented and partially lost during the 2011 marine heatwave, with little to no recovery. The poleward flowing Leeuwin Current is the main driver for kelp dispersal and connectivity between the reef systems in this region and can typically transport drifting material over 200 km within 30 days. Kelp can disperse in two main ways: through dispersal of zoospores and detached fertile material. Detached fertile drift material can disperse over longer distances and provides the greatest potential connectivity between reef systems. However, detached kelp material decomposes over time, and laboratory experiments show that decomposition rates vary significantly with temperature, from the order of several days in warm conditions to hundreds of days in cool conditions. This potentially has considerable implications for the connectivity of kelp reef systems under anthropogenic warming conditions. Here we combine Lagrangian particle tracking simulations with known kelp decomposition rates to show how the connectivity between kelp reefs along the west coast of Australia will change under future climate change scenarios. We show that connectivity may decrease with warming, which has implications for the resilience of kelp forests, potentially limiting processes such as genetic rescue and the recovery of lost kelp forests following extreme events.

Primary Presenter: Mirjam van der Mheen, University of Western Australia (mirjam.vandermheen@uwa.edu.au)

Authors:

Mirjam van der Mheen, University of Western Australia  (mirjam.vandermheen@uwa.edu.au)

Karen Filbee-Dexter, University of Western Australia  (karen.dexter@uwa.edu.au)

Georgina Wood, University of Western Australia  (george.wood@uwa.edu.au)

Albert Pessarrodona, University of Western Australia  (albert.pessarrodona@uwa.edu.au)

Samuel Starko, University of Western Australia  (samuel.starko@uwa.edu.au)

Melinda Coleman, New South Wales Department of Primary Industries  (melinda.coleman@dpi.nsw.gov.au)

Charitha Pattiaratchi, University of Western Australia  (chari.pattiaratchi@uwa.edu.au)

Thomas Wernberg, University of Western Australia  (thomas.wernberg@uwa.edu.au)