Mirjam van der Mheen1, Karen Filbee-Dexter1,2, Chari Pattiaratchi1, Taylor Simpkins1, Albert Pessarrodona1, Thomas Wernberg1,2
1University of Western Australia, Australia - 2Institute for Marine Research, Norway
The Great Southern Reef is a vast network of interconnected kelp-dominated reefs spanning the southern half of Australia. Along the west coast, this reef system stretches over 800 km in latitude from north to south. However, kelp forests on the northern range edge were severely fragmented and partially lost during a severe marine heatwave in 2011, with little to no subsequent recovery. The poleward-flowing Leeuwin Current plays a critical role in kelp dispersal and connectivity between reef systems in the region, typically transporting drifting material over 200 km within 30 days. Kelp disperses primarily through two mechanisms: zoospore dispersal and the drift of detached fertile material. Detached kelp can disperse over longer distances and offers the highest potential for connectivity between reef systems. However, detached kelp decomposes over time, with rates varying significantly depending on water temperature. Laboratory studies indicate decomposition can take just days in warm conditions but extend to hundreds of days in cooler waters. This variation has considerable implications for the connectivity of kelp reefs under anthropogenic warming. Using Lagrangian particle tracking simulations and temperature-dependent kelp decomposition rates, we investigate how connectivity along the west coast of Australia will change under future climate scenarios. Our findings suggest that warming may reduce connectivity among kelp forests, potentially diminishing the resilience of kelp forests by limiting processes such as genetic rescue and recruitment of lost kelp forests after extreme events.
Biography
Mirjam is a physical oceanographer with specific expertise in how objects are transported in the ocean. In her current postdoc, she is determining which physical mechanisms lead to the export of kelp carbon from the coastal ocean into the deep sea, where it may become sequestered. She has also done many other connectivity studies, including connectivity between fish populations, kelp reefs under warming ocean temperatures, and plastic waste between countries along the Indian Ocean rim.