Current hypotheses suggest that cellular elemental stoichiometry of marine eukaryotic phytoplankton such as the ratios of cellular carbon:nitrogen:phosphorus (C:N:P) vary between phylogenetic groups. To investigate how phylogenetic structure, cell volume, growth rate, and temperature interact to affect the cellular elemental stoichiometry of marine eukaryotic phytoplankton, we examined the C:N:P composition in 30 isolates across 7 classes of marine phytoplankton that were grown with a sufficient supply of nutrients and nitrate as the nitrogen source. The isolates covered a wide range in cell volume (5 orders of magnitude), growth rate (<0.01–0.9 d−1), and habitat temperature (2–24°C). Our analysis indicates that C:N:P is highly variable, with statistical model residuals accounting for over half of the total variance and no relationship between phylogeny and elemental stoichiometry. Furthermore, our data indicated that variability in C:P, N:P, and C:N within Bacillariophyceae (diatoms) was as high as that among all of the isolates that we examined. In addition, a linear statistical model identified a positive relationship between diatom cell volume and C:P and N:P. Among all of the isolates that we examined, the statistical model identified temperature as a significant factor, consistent with the temperature-dependent translation efficiency model, but temperature only explained 5% of the total statistical model variance. While some of our results support data from previous field studies, the high variability of elemental ratios within Bacillariophyceae contradicts previous work that suggests that this cosmopolitan group of microalgae has consistently low C:P and N:P ratios in comparison with other groups.
The Nitrogen Control Feasibility Plan (NCFP) has identified step-feed biological nitrogen removal for meeting effluent total nitrogen concentrations < 9 mg-N/L and < 4 mg-N/L at several New York City Water Pollution Control Plants (NYC WPCPs). Under current non-BNR mode operating conditions, the NYC WPCPs rely on chlorination using sodium hypochlorite. Sodium hypochlorite doses are controlled based on the effluent total residual chlorine concentrations and the wastewater flow rate. Given the anticipated shift to BNR operation, we investigated the effect of BNR associated effluent nitrogen species concentrations on the efficacy of disinfection and chlorine dosage required to achieve a given effluent fecal coliform concentration and total chlorine residual concentration. Specifically, we examined the effect of low to intermediate NH 4 + -N concentrations; resulting from nitrification, NO 2 --N concentrations; resulting from incomplete nitrification or denitrification, the relative proportion of NH 4 + -N to unbiodegradable organic-N, suspended solids, all of which may be present in the reactor effluent on disinfection via chlorination. In addition, issues such as formation of toxic disinfection byproducts were addressed in light of the New York State Department of Environmental Conservation's (NYSDEC) promulgation of a total residual chlorine standard, which has identified chlorinated effluent as acutely toxic and an impending reduction in the existing total residual chlorine permit limits. Further, the effect of increased total suspended solids concentrations (poor settling characteristics of BNR sludge due to higher filament abundance on pathogen kill were also evaluated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.