1 Tropical Marginal Seas: Priority Regions For Managing 1 Marine Biodiversity And Ecosystem Function 2 3 4 A.David McKinnon 1 , Alan Williams 2 , Jock Young 2 Daniela Ceccarelli 3 , Piers Dunstan 2 Robert J. 5 W.Brewin 4 , Reg Watson 5 , Richard Brinkman 1 , Mike Cappo 1 , Samantha Duggan 1 , Russell Kelley 6 , 6 Ken Ridgway 2 , Dhugal Lindsay 7 , Daniel Gledhill 2 , Trevor Hutton 8 and Anthony J. Richardson 9,10 . 7 8 1 Australian Institute of Marine Science, PMB No. 3, TMC, Townsville, QLD 4810, Australia 9 2 Wealth from Oceans Flagship, CSIRO Marine and Atmospheric Research, GPO Box 1538, Hobart, 10 TAS 7000, Australia 11 3 P.O. Box 215, Magnetic Island, QLD 4819, Australia 12 4 Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH, UK 13 5 Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, 14 TAS 7000, Australia 15 6 Coral Identification Capacity Building Program 16 7 Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, 17 Yokosuka City, Kanagawa Prefecture, Japan. 237-0021 18 8 Wealth from Oceans Flagship, CSIRO Marine and Atmospheric Research, Ecosciences Precinct, 19 GPO Box 2583, Brisbane, QLD 4102, Australia 20 9 Centre for Applications in Natural Resource Mathematics, School of Mathematics and Physics, 21 The University of Queensland, St Lucia, QLD 4072, Australia 22 10 Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, Ecosciences Precinct, 23 GPO Box 2583, Brisbane, Queensland 4102, Australia 24 25 Corresponding author: A.D. McKinnon d.mckinnon@aims.gov.au 26 Abstract 27 Tropical marginal seas (TMS) are tropical ocean basins connected with the open ocean and 28 bounded by an island arc. TMS occur in regions where human populations are rapidly 29 expanding, where there is high dependence on seafood as a protein source, and where shared 30 geopolitical boundaries and jurisdictions present challenges for effective trans-boundary 31 management of marine ecosystems. Here we contrast and synthesise ecosystem information 32 from 11 TMS that vary in their extent of human influence from the near-pristine Coral Sea to the 33 heavily-exploited South China and Caribbean Seas. Three key ecosystems characterize all TMS: 34 coral reefs and archipelagos, deep-water ecosystems and the pelagic realm. For each, we 35 consider biodiversity, ecosystem function, interaction with adjacent habitats and the influence 36 of human impacts in light of the trans-boundary management of TMS. The identification of 37 ecologically and biologically significant areas (EBSA) is recommended as a first step toward 38 effective ecosystem management of TMS. 39 Keywords 40 Coral reef, fisheries, pelagic, deep sea, trans-boundary, management 41