Mr Mario Minguito Frutos1, Dr. Rohan Arthur2, Dr. Candela Marco-Méndez1, Dr. Jordi Boada3, Dr. Xavier Buñuel1, Dr. Albert Pessarrodona4, Dr. Jordi F. Pagès1, Dr. Emma Cebrian1, Dr. Xavier Turon1, Dr. Enric Ballesteros1, Dr. Eugenia Apostolaki5, Dr. Demetris Kletou6, Mr. Grigorios Skouradakis7, Dr. Matthew P. Adams8,9,10, Dr. Jorge Santamaría1, Dr. Jana Verdura11, Dr. Teresa Alcoverro1
1Blanes Centre for Advanced Studies (CEAB-CSIC), Blanes, Spain, 2Nature Conservation Foundation, Amritha , India, 3Laboratoire d’océanographie de Villefranche, Sorbonne Université, Villefranche-sur-Mer, France, 4Oceans Institute and School of Biological Sciences, UWA Oceans, University of Western Australia, Perth, Australia, 5Institute of Oceanography, Hellenic Centre for Marine Research, Heraklion, Greece, 6Marine and Environmental Research (MER) Lab, Limassol, Cyprus, 7Institute of Marine Biology, Biotechnology and Aquaculture, Hellenic Centre for Marine Research, Heraklion, Greece, 8School of Mathematical Sciences, Queensland University of Technology, Brisbane, Australia, 9Centre for Data Science, Queensland University of Technology, Brisbane, Australia, 10School of Chemical Engineering, The University of Queensland, St Lucia, Australia, 11Université Côte d’Azur, CNRS, Nice, France
Across temperate seas, marine forests on rocky reefs are being converted to overgrazed urchin barrens. The Mediterranean Sea is particularly vulnerable, with two species of sea urchins, Paracentrotus lividus and Arbacia lixula, implicated in the spread of barrens. Understanding the relative vulnerability of locations to overgrazing may help stem this loss. Overgrazing results when rates of herbivory surpass macroalgal production; the size of grazing halos around sedentary herbivores reflects this balance and serve as a handy index of susceptibility. We used grazing halos created by the two sea urchins to explore how the relationship between production and herbivory varied with species, size, environmental context, plant defenses and predation risk across the Mediterranean Sea. We measured halo dimensions of both urchin species found in several rocky reef habitats, in locations with and without predators, and along gradients of depth, nutrients and temperatures. These measures were made across the size spectrum of urchins found at each region. Our results show that A. lixula forms much larger halos than P. lividus, and that halos vary with urchin size and depth. The presence of predators also significantly mitigated the size of halos in P. lividus, likely as a result of fear. Our results indicate that overfished reefs potentially with lower nutrients and higher abundances of A. lixula are at the highest risk of overgrazing. Given that A. lixula does better in warmer waters, this places the reefs of the Eastern Mediterranean at particular risk, a risk that is spreading fast across the Mediterranean as temperatures rise.
Presentation Slides – Mario Minguito Frutos
Biography:
My research aims understanding critical transitions in marine benthic ecosystems. Particularly, I am interested in consumer – resource interactions between herbivores, mainly sea urchins and marine forests. My recent research focuses on determining the mechanisms that help induce these regime shifts. Together with my research group, we are developing both mechanistic and statistical models, to better understand the non-linear dynamics that are common in these ecosystems and which can help us predict these abrupt shifts.
