Dr Ben Harvey1, Prof Sean Connell2, Dr Sylvain Agostini1, Prof Fabio Badalamenti3, Prof Marco Milazzo4, Prof Jason Hall-Spencer1,5, Prof Ivan Nagelkerken2, Dr Shigeki Wada1, Dr Bayden Russell6,7
1Shimoda Marine Research Center, University Of Tsukuba, Shimoda, Japan, 2Southern Seas Ecology Laboratories, School of Biological Sciences and Environment Institute, University of Adelaide, Adelaide, Australia, 3Institute of Anthropic Impacts and Sustainability in Marine Environment (CNR-IAS), Palermo, Italy, 4Dipartimento di Scienze della Terra a del Mare, Università Di Palermo, Palermo, Italy, 5School of Biological and Marine Sciences, University of Plymouth, Plymouth, United Kingdom, 6Swire Institute of Marine Science and Area of Ecology and Biodiversity, School of Biological Sciences, The University of Hong Kong, Hong Kong, Hong Kong SAR, China, 7The Dove Marine Laboratory, School of Natural and Environmental Sciences, Newcastle University, Newcastle-upon-Tyne, United Kingdom
The role of sea urchins in controlling community composition and structural complexity is well supported across a range of ecosystems. Ocean acidification is projected to cause changes in dominance of habitat-formers that transition systems away from complex habitat-forming species (e.g., corals and kelps) towards subordinate species (e.g., turf algae), reducing them into simplified systems that possess low complexity and biodiversity. Contemporary levels of top-down control by sea urchins typically prevent such simple subordinate species from dominating, and yet it remains unclear whether sea urchins can maintain their compensatory role in future ecosystems. Here, we investigated how ocean acidification affects the density, size structure, and grazing rates of five species of sea urchin across three natural CO₂ seep sites in Japan (Shikine Island, 2 species: Diadema setosum and Echinometra sp. A), Italy (Vulcano Island, 2 species: Arbacia lixula and Paracentrotus lividus), and New Zealand (White Island, 1 species: Evechinus chloroticus). We found that under projected ocean acidification conditions, sea urchins displayed reduced density, mean test size, and individual feeding rates. Together, these declines in biological traits mean that the ability of sea urchins to perform their functional role, top-down control of ecosystem structure, is suppressed at the population-level. The functional loss of key benthic macroherbivores will clearly mediate changes in biogenic habitat, and we suggest that the observed habitat simplification due to ocean acidification is greatly enhanced by the functional loss of sea urchins.
Biography:
Ben Harvey is a tenure-track Assistant Professor at the Shimoda Marine Research Center, University of Tsukuba in Japan. After receiving his doctoral degree in marine climate change ecology from Aberystwyth University in the UK, he took up his position in Japan where he seeks to understand how ongoing and future environmental changes will impact our oceans.
