Coral reef fishes reveal strong divergence in the prevalence of traits along the global diversity gradient

Coral reefs are experiencing declines due to climate change and local human impacts. While at a local scale these impacts induce biodiversity loss and shifts in community structure, previous biogeographical analyses recorded consistent taxonomic structure of fish communities across global coral reefs. This suggests that regional communities represent a random subset of the global species and traits pool, whatever their species richness. Using distributional data on 3586 fish species and latest advances in species distribution models, we show marked gradients in the prevalence of size classes and diet categories across the biodiversity gradient. This divergence in trait structure is best explained by reef isolation during past unfavourable climatic conditions, with large and piscivore fishes better represented in isolated areas. These results suggest the risk of a global community re-organization if the ongoing climate-induced reef fragmentation is not halted.

Functional diversity of marine megafauna in the Anthropocene

Marine megafauna, the largest animals in the oceans, serve key roles in ecosystem functioning. Yet, one-third of these animals are at risk of extinction. To better understand the potential consequences of megafaunal loss, here we quantify their current functional diversity, predict future changes under different extinction scenarios, and introduce a new metric [functionally unique, specialized and endangered (FUSE)] that identifies threatened species of particular importance for functional diversity. Simulated extinction scenarios forecast marked declines in functional richness if current trajectories are maintained during the next century (11% globally; up to 24% regionally), with more marked reductions (48% globally; up to 70% at the poles) beyond random expectations if all threatened species eventually go extinct. Among the megafaunal groups, sharks will incur a disproportionate loss of functional richness. We identify top FUSE species and suggest a renewed focus on these species to preserve the ecosystem functions provided by marine megafauna.

Global marine protected areas do not secure the evolutionary history of tropical corals and fishes

Although coral reefs support the largest concentrations of marine biodiversity worldwide, the extent to which the global system of marine-protected areas (MPAs) represents individual species and the breadth of evolutionary history across the Tree of Life has never been quantified. Here we show that only 5.7% of scleractinian coral species and 21.7% of labrid fish species reach the minimum protection target of 10% of their geographic ranges within MPAs. We also estimate that the current global MPA system secures only 1.7% of the Tree of Life for corals, and 17.6% for fishes. Regionally, the Atlantic and Eastern Pacific show the greatest deficit of protection for corals while for fishes this deficit is located primarily in the Western Indian Ocean and in the Central Pacific. Our results call for a global coordinated expansion of current conservation efforts to fully secure the Tree of Life on coral reefs.

Marine protected areas (MPAs) are established to conserve species, but the extent to which they also conserve evolutionary history is not clear. Here, Mouillot et al. show that for tropical corals and fish, the current global MPA network secures only 1.7 and 17.6% of phylogenetic diversity, respectively.

Radiological consequences of the extreme flooding on the lower course of the Rhone valley (December 2003, south east France)

In early December 2003 unusual weather conditions led to major flooding of the lower Rhone valley. When it floods, the Rhone carries large masses of solid matter in suspension, which potentially includes associated artificial (anthropogenic) radioactive contaminants from soil drainage in the catchment area and from re-uptake of sedimentary matter that has been contaminated with low-level radioactive liquid effluents from almost twenty nuclear facilities situated along the Rhone valley. A sampling campaign was carried out to investigate the level and spread of both sediment mass and associated radioactive contamination across the flooded areas. An attempt was made to assess the radiological consequences of such an extreme event on contamination of the food chain. Our results show that almost 700,000 tons of sediment was transported onto the floodplain, of which 80% were coarse and fine sands. These materials transferred 6660 MBq of 137Cs, 93 MBq of (239+240)Pu, 13 MBq of 238Pu and 204 MBq of 60Co over a surface area of 60 km2. More than 90% of deposited sediments are concentrated in a 10 km2 area of agricultural soils, and we estimated that 18% were plowed into the soil. Nevertheless, the level of activity measured in the vegetable crops and milk was not significantly different from the level measured in similar samples from regions that were not affected by the December 2003 floods.