First, the population of oysters hanging on lines may induce changes in the planktonic communities but this remains unproven to date. Second, lines hanging above the lagoon floors can modify the flux of material at the sediment interface. Gaertner-Mazouni et al. (2012) quantified benthic nutrient fluxes and sedimentation rates for two stations located under pearl oyster frames, and two control stations away from the pearl culture facility. They concluded that aquaculture increased sedimentation rates but probably by modification of http://www.selleckchem.com/erk.html local currents and not by the release of additional organic material. No organic enrichment in sediments was demonstrated. Conversely, they showed

that maximum values of benthic nitrogen fluxes were recorded in stations directly under the influence of pearl oyster culture. These benthic nitrogen fluxes could contribute up to 28% of the nitrogen demand in the water column. Third, human populations around farms could directly impact the lagoon. Bouvy et al.

(2012a) concluded from faecal indicator bacteria that there was no evidence that human sewage had click here any impact on picoplankton throughout the atoll. They concluded that Ahe atoll belongs to the type of unproductive aquatic system, without high external inputs of inorganic nutrients issuing from human activities, as defined by Duarte and Agusti (1998). Three papers in this issue refine knowledge of planktonic communities of atoll lagoons. First, Bouvy et al. (2012b) investigate with one survey per atoll the virioplankton and bacterioplankton in Ahe and Takaroa atolls, in comparison with the surrounding oligotrophic ocean. The role of virioplankton in lagoons was unknown while viruses are the numerically dominant biological entities in the ocean and viral infection is a major structuring process in the dynamics of marine microbial communities. For instance, viral lysis of autotrophic and heterotrophic microorganisms influences the rate

of nutrient cycling through microbial food webs. Most virioplankton in the environment infect bacterioplankton and, in general, the distributions of viral populations often mirror the bacterial distributions. However, Bouvy et al. (2012b) suggest that the distribution patterns of virioplankton Nintedanib (BIBF 1120) are apparently not coupled in Ahe and Takaroa. Fractions of infected bacterial cells were all extremely low, among the lowest recorded in both marine and freshwater systems. Differences between atolls occurred, with a mean virus-to-bacteria ratio significantly lower in Ahe than in Takaroa. This is consistent with the hypothesis that this ratio is likely to increase in environments that favor fast bacterial growth given the estimated longer residence times in Takaroa compared to Ahe. Michotey et al. (2012) investigated the prokaryotes communities of Ahe lagoon using molecular techniques.