Overseas coral reefs and seagrasses - Developing WFD bioassessment tools

International audience

English. In the year 2000, the European water framework directive (WFD) profoundly modified water-management policies by placing ecological considerations at the heart of the decision-making process. Since then, the development of bioassessment tools to inform on the ecological status of littoral and continental surface waters has been a major objective for the European scientific community. In continental France, an array of tools are already operational. In the overseas territories (OST, the Départements d’outremer in French), a number of tools have been validated and legally approved for rivers.For the coastal waters of the island OSTs (Guadeloupe, Martinique, Mayotte and Réunion Island), the idea was to develop similar methods for coral reefs and beds of phanerogams (seagrass) that often lie just off the coasts oftropical islands. Major issues are involved in the conservation and protection of these emblematic ecosystems that serve as the basis for many economic and social activities. But in terms of the specific WFD needs, can coralreefs and seagrasses serve as indicators suited to assessing the ecological status of water bodies? The development of such tools represents a scientific challenge given the paucity of available knowledge on the ecology and functioning of these tropical ecosystems, and the relative lack of experience in their assessment.The Seagrass and reef benthos national work group was set up in 2011 to collectively provide science advice on the topic. This document sums up the discussions and work of the group from 2011 to 2014, during threesymposia and two missions in the field. Following a presentation of the context (Chapter 1), the discussion turns to the main topics addressed, namely an evaluation of the relevance of seagrasses and reef benthos in terms of WFD monitoring and assessment of water bodies (Chapter 2), identification of the parameters best suited to informing on the ecological status of coastal water bodies (Chapter 3), the protocols required to acquire the data (Chapter 4) and, finally, the work required to define the quality criteria (Chapter 5).