Changes in the microbial community based on seawater pH variations

Ocean acidification is an effect of the rise in atmospheric CO2, which causes a reduction in the pH of the ocean and generates a number of changes in seawater chemistry and consequently potentially impacts seawater life. The effect of ocean acidification on metabolic processes (such as net community production and community respiration and on particulate organic carbon (POC) concentrations was investigated in summer 2012 at Cap de la Revellata in Corsica (Calvi, France). Coastal surface water was enclosed in 9 mesocosms and subjected to 6 pCO2 levels (3 replicated controls and 6 perturbations) for approximately one month. No trend was found in response to increasing pCO2 in any of the biological and particulate analyses. Community respiration was relatively stable throughout the experiment in all mesocosms, and net community production was most of the time close to zero. Similarly, POC concentrations were not affected by acidification during the whole experimental period. Such as the global ocean, the Mediterranean Sea has an oligotrophic nature. Based on present results, it seems likely that seawater acidification will not have significant effects on photosynthetic rates, microbial metabolism and carbon transport.

Stratigraphic study and analysis of the barchan dunefield of the Laguna coastal zone in Santa Catarina, Brazil

The association of several favorable factors has resulted in the development of a wide barchan dune field that stands out as a fundamental element in the coastal landscape of southern Santa Catarina state in Brazil. This original ecosystem is being destroyed and highly modified, due to urbanization. This work identifies and discusses its basic characteristics and analyzes the favorable factors for its preservation, in the foreseen of both a sustainable future and potential incomes from ecotourism. The knowledge of the geologic evolution allows to associate this transgressive Holocene dunes formation to more dissipative beach conditions. Spatial differences on morphodynamics are related to local and regional contrasts in the sediment budget, with an influence on gradients of wave attenuation in the inner shelf and consequently with influence in the level of coastal erosion. The link between relative sea level changes and coastal eolian sedimentation can be used to integrate coastal eolian systems to the sequence stratigraphy model. The main accumulation phase of eolian sediments would occur during the final transgressive and highstand systems tracts. Considering the global character of Quaternary relative sea level changes, the Laguna transgressive dune field should be correlated with similar eolian deposits developed along other parts of the Brazilian coast compatibles with the model of dunefield initiation during rising and highstand sea level phases.