RESUMEN
Ammonia is toxic to fish, and when associated with global warming, it can cause losses in aquaculture. In this study, we investigated the physiological and zootechnical responses of Arapaima gigas to the current scenarios and to RCP8.5, a scenario predicted by the IPCC for the year 2100 which is associated with high concentrations of environmental ammonia (HEA). Forty-eight chipped juvenile A. gigas were distributed in two experimental rooms (current scenario and RCP8.5) in aquariums with and without the addition of ammonia (0.0 mM and 2.44 mM) for a period of 30 days. The HEA, the RCP8.5 scenario, and the association of these factors affects the zootechnical performance, the ionic regulation pattern, and the levels of ammonia, glucose, triglycerides, sodium, and potassium in pirarucu plasma. The branchial activity of H+-ATPase was reduced and AChE activity increased, indicating that the species uses available biological resources to prevent ammonia intoxication. Thus, measures such as monitoring water quality in regard to production, densities, and the feed supplied need to be more rigorous and frequent in daily management in order to avoid the accumulation of ammonia in water, which, in itself, proved harmful and more stressful to the animals subjected to a climate change scenario.
RESUMEN
To promote the rational application of nitrogen fertilizer in winter wheat after rice stubble, the effects of nitrogen application rate (0, 150, 225, 300 kg·hm-2, expressed as N0, N150, N225, N300) on nitrogen recovery, residue, loss and grain yield were examined using field 15N tracer technology. The results showed that with the increases of application rate, nitrogen accumulation from different sources significantly increased while nitrogen recovery significantly decreased. The accumulation of basal nitrogen in plants reached the peak during overwintering stage to jointing stage, while the accumulation of topdressing nitrogen peaked between jointing to flowering stage. At maturity, nitrogen accumulation of the top fertilizer was higher than that of the base fertilizer. Plant nitrogen accumulation from soil under N150 was higher than that from nitrogen fertilizer, but with an opposite tendency under N225 and N300. With the increases of nitrogen application rate, the residual nitrogen in the 0-100 cm soil layer in the maturing stage significantly increased, while the residual nitrogen ratio in the 60-100 cm soil layer gradually increased. In the whole growth period of wheat, both nitrogen loss and loss ratio were positively correlated with nitrogen application rate. The nitrogen loss of base fertilizer reached the highest during sowing to overwintering stage, while the nitrogen loss of top fertilizer was at the peak from jointing to flowering period. Taking grain yield into consideration, N225 treatment was the proper application rate for winter wheat after rice stubble, with grain yield being 6735 kg·hm-2, and the nitrogen fertilizer recovery rate, soil residue rate and loss rate being 42.6%, 34.0% and 23.3%, respectively.