Crassulacean acid metabolism in the context of other carbon-concentrating mechanisms in freshwater plants: a review

Inorganic carbon can be in short-supply in freshwater relative to that needed by freshwater plants for photosynthesis because of a large external transport limitation coupled with frequent depleted concentrations of CO2 and elevated concentrations of O2. Freshwater plants have evolved a host of avoidance, exploitation and amelioration strategies to cope with the low and variable supply of inorganic carbon in water. Avoidance strategies rely on the spatial variation in CO2 concentrations within and among lakes. Exploitation strategies involve anatomical and morphological features that take advantage of sources of CO2 outside of the water column such as the atmosphere or sediment. Amelioration strategies involve carbon concentrating mechanisms (CCM) based on uptake of bicarbonate, which is widespread, C4-fixation which is infrequent and Crassulacean Acid Metabolism (CAM) which is of intermediate frequency. CAM enables aquatic plants to take up inorganic carbon in the night. Furthermore, daytime inorganic carbon uptake is generally not inhibited and therefore CAM is considered to be a carbon conserving mechanism. CAM in aquatic plants is a plastic mechanism regulated by environmental variables and is generally down-regulated when inorganic carbon does not limit photosynthesis. CAM is regulated in the long term (acclimation during growth), but is also affected by environmental conditions in the short term (response on a daily basis). In aquatic plants CAM appears to be an ecologically important mechanism for increasing inorganic carbon uptake, since the in situ contribution from CAM to the C-budget generally is high (18-55%)

Surface activity, sex ratio and diversity of scorpions in two different habitats in an Arid Chaco reserve, Argentina

Scorpions are one of the most important taxa of predators in terms of density, biomass, and diversity in various areas of the world. In this study, we compared population- and community-level data between a mature and a secondary forest in the Chancaní Reserve (Córdoba, Argentina). Scorpions were collected using pitfall traps (54 nights per site), and their nocturnal activity was observed by means of UV light (26 nights per site) over 7 months. Seven species of scorpions (1964 individuals) were observed in the study area (Bothriuridae and Buthidae). Brachistosternus ferrugineus composed >74 % of all individuals and was numerically dominant in most months. It was the most common species sampled with UV light method in all months (85.73 % in mature and 81.80 % in secondary forest). Timogenes elegans was the most common species sampled with the pitfall traps method in secondary forest (48.58 %). General sex ratio (males:females) for B. ferrugineus was 1:1.24 and for T. elegans was 1:0.53. The Shannon index was not significantly different between sites. Species richness was similar, and the Jaccard index was Cs = 0.86, indicating that both sites share 86 % of the species. Tityus confluens was the only species not shared between sites. Our results indicate that species composition in regenerating forest resembles that of primary forest after c. 15 years, but the relative abundances of these species differ.Fil: Nime, Mónica Fernanda. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Instituto de Diversidad y Ecologia Animal; ArgentinaFil: Casanoves, Fernando. Consejo Nacional de Investigaciones Cienti­ficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; ArgentinaFil: Mattoni, Camilo Ivan. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Instituto de Diversidad y Ecologia Animal; Argentin