Can simple be useful and reliable? Using ecological indicators to represent and compare the states of marine ecosystems

15 pages, 7 figures, 2 tablesWithin the IndiSeas WG, the evaluation of exploited marine ecosystems has several steps, from simple binary categorization of ecosystems to a more-complex attempt to rank them and to evaluate their status using decision-tree analyses. With the intention of communicating scientific knowledge to the public and stakeholders, focus is on evaluating and comparing the status of exploited marine ecosystems using a set of six ecological indicators and a simple and transparent graphic representation of ecosystem state (pie charts). A question that arose was whether it was acceptable to compare different types of marine ecosystems using a generic set of indicators. To this end, an attempt is made to provide reference levels to which ecosystems can be objectively compared. Unacceptable thresholds for each indicator are determined based on ecological expertise derived from a questionnaire distributed to a group of scientific experts. Analysis of the questionnaires revealed no significant difference in the thresholds provided for different ecosystem types, suggesting that it was reasonable to compare states directly across different types of ecosystem using the set of indicators selected.The IndiSeas WG was funded by the European Network of Excellence EUR-OCEANS (FP6, contract 511106), the European collaborative project MEECE, Marine Ecosystem Evolution in a Changing Environment (FP7, contract 212085), and the IRD (Institut de Recherche pour le Développement). MC was supported financially by postdoctoral fellowships from the Spanish Ministry of Science and Technology, and by a European Commission Marie Curie Post-doctoral Fellowship through the International Outgoing Fellowships (Call FP7-PEOPLE-2007-4-1-IOF) for the ECOFUN project. LJS was supported financially by the MEECE project and Astrid Jarre's South African Research Chair in Marine Ecology and Fisheries.Peer reviewe