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Effets des métaux et des changements climatiques sur les coraux

Abstract : Coral reefs have largely degraded in recent decades under the influence of human activities. Among those disturbances, the increase in metal concentrations affects many reefs worldwide (e.g. Australian Great Barrier Reef, Costa Rica, Red Sea, New Caledonia). Furthermore, reefs have now to face climate change, and more particularly temperature increase and ocean acidification. In this context, the aims of my thesis were to (1) determine the effects of the main metals present in lateritic sediments (iron, manganese, nickel and cobalt) on coral physiology using concentrations representative of those measured along the New Caledonian coastline, and to (2) define their potential roles in this context of climate change. My results showed that metals affect coral metabolism in different ways. While at ambient temperature, a nickel or manganese enrichment stimulates host metabolism and symbiont photosynthesis, conversely a cobalt enrichment inhibits calcification and becomes even toxic for the host and symbionts, from 1 μg L-1. Despite its importance in photosynthetic processes, an iron enrichment induces a decrease in Symbiodinium densities and an inhibition of calcification rates. Under thermal stress, manganese enhances coral tolerance to temperature increase, likely by stimulating their antioxidant defenses, while nickel worsens its effects by decreasing even more their growth. These works represent an important step towards a better understanding of coral responses to metal enrichment and would explain, to some extent, species susceptibility to climate change.
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Submitted on : Friday, June 12, 2020 - 11:27:11 AM
Last modification on : Tuesday, October 27, 2020 - 3:31:20 AM


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  • HAL Id : tel-02866069, version 1


Tom Biscéré. Effets des métaux et des changements climatiques sur les coraux. Ecotoxicologie. Sorbonne Université, 2018. Français. ⟨NNT : 2018SORUS382⟩. ⟨tel-02866069⟩



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