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Innovative tools and a mixed status report for aquatic biodiversity

Scientists, managers, companies, associations, etc., over 200 people in all responded to the invitation by Onema for a national symposium on aquatic biodiversity, held on 14 and 15 November in Paris. Some 30 partnership-research projects were presented, each providing new data on the life in our rivers and lakes.

In continental France, 15 out of 69 fish species and a quarter of crustaceans may be found on the IUCN (International union for the conservation of nature) red lists. That is alarming, but trends have improved since 1990. The Onema study on continental France revealed an increase in distribution ranges and in the abundance of a majority of fish species, despite major differences between species and sites. On the local level, long-term data series are available for more in-depth analysis, e.g. on migratory salmonids in the Bresle river (Onema) and on food chains in Lake Geneva over the past 40 years.

Environmental DNA and functional indicators
Going beyond a status report, the symposium also presented innovative evaluation tools for biodiversity. Environmental DNA techniques, i.e. the identification of DNA fragments in water, were tested in a river (Onema / Grenoble university). This technique holds great promise for fish inventories, but also for inventories of all aquatic fauna. New, integrative indicators on ecosystem operation, capable of informing on the status of ecological processes at a given measurement station and of assessing the success of environmental restoration projects, are now being developed, e.g. an indicator on the speed of decomposition of organic matter (Onema / Metz university).

From pressures to restoration
The links between pressures and biodiversity, essential factors for research and management, were the topics of three, very full sessions. The first dealt with the impact of climate change, the second with damage to habitats and the third with invasive species. Among the presented results, a comparison of fish distribution ranges (Toulouse university III) between two different periods, one "cold" period (1980 to 1992) and a "hot" period (2003 to 2009), revealed divergent changes, i.e. the Mediterranean barbel tended to reappear at the edges of its initial zone, whereas trout disappeared from the edges of its zone. Analysis of the links between hydrology and biodiversity (Onema / HEPIA) addresses the need to ensure not a minimum flow rate, but rather an annual flow regime for the correct operation of ecosystems, ranging from seasonal highwaters required for the reproduction of certain species to low-flow rates that modify the structure of populations. Finally, a number of restoration projects were presented. For example, efforts to remove obstacles, a part of the Life Nature programme, resulted in the Rhone apron recolonising sections of the basin (see article opposite) and moving a water-treatment plant on the Vistre river (Gard department) led to a rapid improvement in the composition of invertebrate communities (Onema / Irstea). It is now clear that projects to restore biodiversity, if correctly implemented, can produce good results.


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