Prof. Anna Metaxas1
1Dalhousie University, Halifax, Canada
The rocky subtidal ecosystems in several regions of Atlantic Canada have undergone a phase shift from being dominated by lush kelp beds to turf over the last few decades, because of two stressors, an invasive species and ocean warming. An invasive annual epiphytic bryozoan forms large colonies that cover the kelp blades, compromising their structural integrity and increasing their susceptibility to breakage by waves. Temperature is the most important predictor of bryozoan abundance on regional spatial scales, and over decadal time scales, bryozoan abundance is predicted to increase with warming temperatures, making the recovery of kelp beds unlikely. However, we recently discovered healthy kelp beds in a region with high wave exposure and slightly cooler temperatures. Because the population dynamics of the bryozoan are generally similar in the two regions, we suggest that the observed resilience of kelp beds is a combination of: (1) overwinter recovery of kelp from damage or loss facilitated by the bryozoan, possibly due to differences in the magnitude of damage and loss or high growth kelp growth rates; and (2) phenotypic adaptations of kelp to wave action that also promote resilience to damage or loss. We also predicted high population connectivity among kelp patches in the wave exposed region on scales of kilometres, which in turn can enhance resilience to stressors. Populations of these more resilient kelps should be prioritized for protection and considered for kelp seeding if limited connectivity compromises replenishment.
Biography:
Anna Metaxas studies marine benthic ecosystems and connectivity, in habitats from shallow rocky subtidal regions to the deep sea, including hydrothermal vents and deep-water corals, in temperate and tropical regions of the world. She was a theme leader in the NSERC Canadian Healthy Oceans Network, co-leads the Biodiversity Conservation Task Force of the Deep Ocean Stewardship Initiative, is a lead author on the Nexus Assessment of IPBES and advises the International Seabed Authority and the Convention on Biological Diversity. She leads a project on knowledge exchange in Nunatsiavut for a sustainable future under climate change.
