Performance of Full-Scale Thermophilic Membrane Bioreactor and Assessment of the Effect of the Aqueous Residue on Mesophilic Biological Activity

To date, the management of high-strength wastewater represents a serious problem. This work aims to evaluate the performance on chemical pollutants and on sludge production of one of the two full-scale thermophilic membrane bioreactors (ThMBRs) currently operational in Italy, based on monitoring data of the last two and a half years. Removal yields on COD, N-NOx, non-ionic and anionic surfactants (TAS and MBAS), increased with the input load up to 81.9%, 97.6%, 94.7%, and 98.4%, respectively. In the period of stability, a very low value of sludge production (0.052 kgVS kgCOD−1) was observed. Oxygen uptake rate (OUR) tests allowed us to exclude the possibility that mesophilic biomass generally exhibited any acute inhibition following contact with the aqueous residues (ARs), except for substrates that presented high concentrations of perfluoro alkyl substances (PFAS), cyanides and chlorides. In one case, nitrifying activity was partially inhibited by high chlorides and PFAS concentration, while in another the substrate determined a positive effect, stimulating the phenomenon of nitrification. Nitrogen uptake rate (NUR) tests highlighted the feasibility of reusing the organic carbon contained in the substrate as a source in denitrification, obtaining a value comparable with that obtained using the reference solution with methanol. Therefore, respirometric tests proved to be a valid tool to assess the acute effect of AR of ThMBR on the activity of mesophilic biomass in the case of recirculation.

Elevated Carbon Dioxide and Chronic Warming Together Decrease Nitrogen Uptake Rate, Net Translocation, and Assimilation in Tomato

The response of plant N relations to the combination of elevated CO2 (eCO2) and warming are poorly understood. To study this, tomato (Solanum lycopersicum) plants were grown at 400 or 700 ppm CO2 and 33/28 or 38/33 °C (day/night), and their soil was labeled with 15NO3− or 15NH4+. Plant dry mass, root N-uptake rate, root-to-shoot net N translocation, whole-plant N assimilation, and root resource availability (%C, %N, total nonstructural carbohydrates) were measured. Relative to eCO2 or warming alone, eCO2 + warming decreased growth, NO3− and NH4+-uptake rates, root-to-shoot net N translocation, and whole-plant N assimilation. Decreased N assimilation with eCO2 + warming was driven mostly by inhibition of NO3− assimilation, and was not associated with root resource limitations or damage to N-assimilatory proteins. Previously, we showed in tomato that eCO2 + warming decreases the concentration of N-uptake and -assimilatory proteins in roots, and dramatically increases leaf angle, which decreases whole-plant light capture and, hence, photosynthesis and growth. Thus, decreases in N uptake and assimilation with eCO2 + warming in tomato are likely due to reduced plant N demand.

Inter- and intra-specific responses of coccolithophores to CO₂-induced ocean acidification

Oceanic uptake of anthropogenic carbon dioxide (CO2) is altering the seawater chemistry of the world's oceans with consequences for marine bioregions, especially calcareous organisms such as corals, foraminifera and coccolithophores. The coccolithophores, one of the most abundant and widespread groups of calcifying plankton, are responsible for a large proportion of modern oceanic carbonate production. However, culture experiments examining the response of coccolithophores to elevated CO2 partial pressure (pCO2) have mostly been based on investigations of a single strain and have yielded contradictory results from different experiments between and even within species. Here, four strains of the coccolithophores Emiliania huxleyi (E. huxleyi) and Gephyrocapsa oceanica (G. oceanica), which contained separately naked and calcifying strains, were investigated simultaneously for the first time in a bubbling batch culture at four CO2 grades ranging from approximately 380 to 2000 μatm. We synchronously determined multiple physiological parameters of four coccolithophore strains involving growth, photosynthesis, nitrogen uptake, elemental compositions and calcification efficiency in the process of cultivation. The results did not show a uniform response from different strains to elevated pCO2 up to 2000 μatm, and the naked strain E. huxleyi (N-E) was seriously suppressed, in sharp contrast to the positive response of the different levels of the other three algae. In addition, we fitted nitrogen uptake rate response curves relative to changing pCO2 for the four strains and applied kinetic constants from the response curves to further analyze the hypostatic difference among different strains, which reflected the same variational trend of the four stains above vs. increasing CO2. We determined that the responses of coccolithophores to ocean acidification are inter- and intra-specific, and this variation may cause changes to biodiversity and other ecosystem processes in the future ocean.

Exploitation of Nutrient-Rich Soil Patches by Invasive Annual and Native Perennial Grasses

Invasion of nutrient-poor habitats might be related to the ability of a species to exploit nutrient-rich microsites. Recent research suggests fast-growing species might have a greater ability to allocate root biomass to nutrient-rich microsites (root foraging precision) than slow-growing species. We examined if differences in relative growth rate (RGR) between invasive and native species were related to differences in foraging precision. We hypothesized that invasive species would: (1) have greater foraging precision than native species but (2) greater foraging precision would come at a cost in terms of root nutrient uptake rate. Foraging precision was evaluated on plants growing in soils with uniform or patchy nutrient distribution. Plants were harvested at a common time and a common developmental stage to separate indirect effects of RGR on foraging. Nutrient uptake rate was examined by exposing plants to a low or high nitrogen pulse. Invasives foraged more precisely than natives but had lower nitrogen uptake rate. Although these results support the idea of a positive relationship between RGR and foraging precision, biomass production in heterogeneous soils showed no relationship to foraging precision. Instead, species with greater RGR produced more biomass and root length across all treatments, allowing greater nutrient capture in heterogeneous soils. Although these results do not exclude a role for proliferation in influencing invasion of nutrient-poor systems or the potential for heterogeneity to influence population processes, these results suggest other traits may have an overriding importance in determining invader success in these systems.

Effect of hyperinsulinemia on amino acid utilization in the ovine fetus

We studied the effect of an acute 4-h period of hyperinsulinemia (H) on net utilization rates (AAURnet) of 21 amino acids (AA) in 17 studies performed in 13 late-gestation fetal sheep by use of a novel fetal hyperinsulinemic-euglycemic-euaminoacidemic clamp. During H [84 ± 12 (SE) μU/ml H, 15 ± 2 μU/ml control (C), P < 0.00001], euglycemia was maintained by glucose clamp (19 ± 0.05 μmol/ml H, 1.19 ± 0.04 μmol/ml C), and euaminoacidemia (mean 4.1 ± 3.3% increase for all amino acid concentrations [AA], nonsignificantly different from zero) was maintained with a mixed amino acid solution adjusted to keep lysine concentration constant and other [AA] near C values. H produced a 63.7% increase in AAURnet (3.29 ± 0.66 μmol · min−1 · kg−1 H, 2.01 ± 0.55 μmol · min−1 · kg−1 C, P < 0.001), accounting for a 60.1% increase in fetal nitrogen uptake rate (2,064 ± 108 mg · day−1 · kg−1 H, 1,289 ± 73 mg · day−1 · kg−1 C, P < 0.001). Mean AA clearance rate (AAURnet/[AA]) increased by 64.5 ± 18.9% ( P < 0.001). Thus acute physiological H increases net amino acid and nitrogen utilization rates in the ovine fetus independent of plasma glucose and [AA].