“Microalgal strains for algal biofuels production in outdoor ponds will need to have high net growth rates under diverse environmental conditions. A small,
variable salinity pond in the San Elijo Lagoon estuary in southern California was chosen to serve as a model pond due to its routinely high chlorophyll content. Profiles of microalgal assemblages from water samples collected from April 2011 to January 2012 were obtained by constructing 18S rDNA environmental clone libraries. Pond assemblages were found to be dominated by green algae Picochlorum sp. and Picocystis sp. throughout the year. Pigment analysis suggested that the two species contributed most of the chlorophyll a of the pond, which ranged from 21.9 to 664.3 μg · L−1 with the Picocystis contribution check details increasing at higher salinities. However, changes of temperature, Selleckchem CH5424802 salinity or irradiance may have enabled a bloom of the diatom Chaetoceros sp. in June 2011. Isolates of these microalgae were obtained and their growth rates characterized as a function of temperature and salinity. Chaetoceros
sp. had the highest growth rate over the temperature test range while it showed the most sensitivity to high salinity. All three strains showed the presence of lipid bodies during nitrogen starvation, suggesting they have potential as future biofuels strains. “
“Inorganic carbon uptake by Alexandrium catenella
estimated from incorporation of 13C labelled bicarbonate (an estimate of carbon gain by autotrophy) was compared to increases in particulate carbon (PC) that integrate all processes leading to carbon gain by cells (autotrophy, heterotrophy, mixotrophy). During blooms of A. catenella in the field, the 13C tracer technique could account for only 47% (range 29%–59%) of the increase in PC in conventional 24 h incubations. From dilution experiments, the ratio of PC increases Calpain to bicarbonate uptake was related significantly and positively to the grazing rate, indicating that dissolved organic carbon contributes to growth as a direct function of grazing activity. In addition, as grazing rate increases, the contribution of dissolved inorganic carbon uptake to carbon-based growth decreases in a linear way (from 56% to 33% of total C acquisition) and the contribution of non autotrophic processes increases (from 54% to 67%). Thus, grazing appears to closely control the balance between autotrophic and non autotrophic processes leading to carbon acquisition by natural populations of A. catenella. “
“Resource allocation and translocation are fundamental physiological functions for autotrophs. The mobilization and use of resources drive population dynamics by regulating growth and recovery of individuals, but also influences ecosystem-level processes such as primary productivity and carbon cycling.