Benthic response to ammonium pulses in a tropical lagoon : implications for coastal environmental processes

In New Caledonia, the benthic communities living in the coral reef lagoon around Noumea city are subjected to regular shifts from oligotrophic conditions typical of lagoon waters to nutrient enrichment due to waste water inputs. The influence of ammonium pulses on microphytobenthos production was experimentally tested under varying light intensities in the vicinity of Noumea. Benthic oxygen, ammonium and silicon fluxes at the sediment-water interface were measured in situ using benthic enclosures. Three ammonium concentrations were tested. Gross primary production was doubled with a 13.8 mu mol 1(-1) ammonium concentration increase. Fitted PI curves showed that maximum production (F-max) was linearly related to ammonium concentration, but not the optimal irradiance (I-k). Silicon fluxes were characterized by dissolution in the absence of light, a process that declined with increasing illumination. These results were attributed to microphytobenthos activity, mainly diatoms that are nutrient-limited and strongly reactive to ammonium inputs. Production may result from a multiplication of cells, but migration up to the water sediment interface may also be involved. Oxygen consumption was also significantly influenced by ammonium concentration as a positive linear relationship with added ammonium concentration was established. Even during short-term experiments, ammonium enrichment stimulated photoautotrophic production, increasing the energy available to heterotrophs. Furthermore, microbenthic activities as well as nitrate production were increased by ammoniaoxidizing bacteria able to grow chemolithotrophically at the expense of oxygen. Therefore, in the study area, pulses of urban waste waters resulted in a decrease of plant-related autotrophy in benthic communities. (c) 2004 Elsevier B.V. All rights reserved

Origine, transport et devenir des apports naturels et anthropiques dans le lagon sud-ouest de Nouvelle-Calédonie

L’ird (Institut de recherche pour le développement) conduit depuis dix ans un programme pluridisciplinaire sur les effets des apports naturels et anthropiques sur le fonctionnement du lagon de Nouvelle-Calédonie. Celle-ci connaît actuellement une croissance de sa population et un développement de son industrie minière. Trois grands types d’apports sont pris en compte : les particules entraînées par l’érosion des sols et des sous-sols et dont l'accumulation brutale peut être responsable du dépôt de quantités considérables de sédiments, les métaux potentiellement toxiques pour les organismes vivant dans le lagon et les éléments nutritifs susceptibles de conduire les eaux jusqu'à l’eutrophisation (confinement chimique conduisant à l'élimination de nombreuses espèces vivantes et à la dominance d'un petit nombre d'autres). Le présent article offre trois exemples de problématiques environnementales qui n'ont pu être résolues qu’au moyen de la fédération de différentes approches de recherche complémentaires : l’influence des courants sur la dispersion des particules détritiques en provenance de l'île, le devenir des métaux dans le lagon et leur accumulation dans les organismes, les effets des apports en nutriments sur les communautés planctoniques et les risques d'eutrophisation. Les résultats de ces recherches sont présentés tout en conservant à l’esprit les objectifs nécessairement appliqués d’un programme de recherche pour le développement. Il s’agit principalement de définir les bases scientifiques permettant d’identifier certains outils de diagnostic environnemental et de développer des approches de simulation mathématique susceptibles d'offrir une vision synthétique et prévisionnelle de l’état et du devenir des environnements lagonaires sous influence anthropique.For the past ten years, the ird (Institut de recherche pour le développement) has developed a multidisciplinary programme dealing with the effects of natural and anthropogenic terrigenous inputs on the New Caledonia coral reef lagoon which is currently subjected to environmental pressure due to population increase and development of the mining industry. The ongoing study focused on three main categories of inputs: (i) particles generated by erosion processes and responsible for excessive sediment inputs in the lagoon, (ii) metals exhibiting a potentially lethal effect on the lagoon biota, (iii) nutrients responsible for eutrophication. This article presents three examples of environmental issues that could be addressed through complementary research approaches: (i) the dispersion of terrigenous inputs as commended by currents, (ii) the fate of metals in the lagoon and their accumulation in the biota, (iii) the effects of nutrient enrichment on pelagic communities. Results are presented while keeping in mind the necessary applied outcomes requested from a research programme devoted to development issues. Such outcomes are mainly related to the identification of suited environmental diagnostic tools and to the development of modelling approaches yielding synthetic and predictive information on the status and fate of coral reef lagoons subject to anthropogenic stress

Evolutionary history of the little fire ant Wasmannia auropunctata before global invasion: Inferring dispersal patterns, niche requirements and past and present distribution within its native range

The evolutionary history of invasive species within their native range may involve key processes that allow them to colonize new habitats. Therefore, phylogeographic studies of invasive species within their native ranges are useful to understand invasion biology in an evolutionary context. Here we integrated classical and Bayesian phylogeographic methods using mitochondrial and nuclear DNA markers with a palaeodistribution modelling approach, to infer the phylogeographic history of the invasive ant Wasmannia auropunctata across its native distribution in South America. We discuss our results in the context of the recent establishment of this mostly tropical species in the Mediterranean region. Our Bayesian phylogeographic analysis suggests that the common ancestor of the two main clades of W. auropunctata occurred in central Brazil during the Pliocene. Clade A would have differentiated northward and clade B southward, followed by a secondary contact beginning about 380 000 years ago in central South America. There were differences in the most suitable habitats among clades when considering three distinct climatic periods, suggesting that genetic differentiation was accompanied by changes in niche requirements, clade A being a tropical lineage and clade B a subtropical and temperate lineage. Only clade B reached more southern latitudes, with a colder climate than that of northern South America. This is concordant with the adaptation of this originally tropical ant species to temperate climates prior to its successful establishment in the Mediterranean region. This study highlights the usefulness of exploring the evolutionary history of invasive species within their native ranges to better understand biological invasions. © 2016 European Society for Evolutionary Biology

Corrigendum: Delivery of crop pollination services is an insufficient argument for wild pollinator conservation

There is compelling evidence that more diverse ecosystems deliver greater benefits to people, and these ecosystem services have become a key argument for biodiversity conservation. However, it is unclear how much biodiversity is needed to deliver ecosystem services in a cost-effective way. Here we show that, while the contribution of wild bees to crop production is significant, service delivery is restricted to a limited subset of all known bee species. Across crops, years and biogeographical regions, crop-visiting wild bee communities are dominated by a small number of common species, and threatened species are rarely observed on crops. Dominant crop pollinators persist under agricultural expansion and many are easily enhanced by simple conservation measures, suggesting that cost-effective management strategies to promote crop pollination should target a different set of species than management strategies to promote threatened bees. Conserving the biological diversity of bees therefore requires more than just ecosystem-service-based arguments

Delivery of crop pollination services is an insufficient argument for wild pollinator conservation

There is compelling evidence that more diverse ecosystems deliver greater benefits to people, and these ecosystem services have become a key argument for biodiversity conservation. However, it is unclear how much biodiversity is needed to deliver ecosystem services in a cost-effective way. Here we show that, while the contribution of wild bees to crop production is significant, service delivery is restricted to a limited subset of all known bee species. Across crops, years and biogeographical regions, crop-visiting wild bee communities are dominated by a small number of common species, and threatened species are rarely observed on crops. Dominant crop pollinators persist under agricultural expansion and many are easily enhanced by simple conservation measures, suggesting that cost-effective management strategies to promote crop pollination should target a different set of species than management strategies to promote threatened bees. Conserving the biological diversity of bees therefore requires more than just ecosystem-service-based arguments

A method for the determination of inorganic phosphate in the presence of labile organic phosphate and high concentrations of protein: application to lens ATPases.

International audienceWe present here an improvement in the classical molybdate method for inorganic phosphate determination. This method has high sensitivity, with 1 nmol of Pi giving an absorbance change of 0.060 A850 unit. It is highly reproducible and the color remains stable for at least 3.5 h. In addition the use of sodium dodecyl sulfate makes it possible to stop enzymatic reactions without organic phosphate hydrolysis. It also shows an extremely low interference by highly concentrated solutions of different origins. Of special interest is its high tolerance to protein, permitting as much as 50 mg/ml of human serum protein in the sample without precipitation or color interference. For these reasons, it proves to be very useful in the determination of ATPases in tissues such as the ocular lens with low specific activity