Metabolic adjustment of Pyrrhulina aff. brevis exposed to different climate change scenarios

Ammonia Increases the Stress of the Amazonian Giant Arapaima gigas in a Climate Change Scenario

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.

Interactive effects of ocean acidification, ocean warming, and diurnal temperature cycling on antioxidant responses and energy budgets in two sea urchins Strongylocentrotus intermedius and Tripneustes gratilla from different latitudes

To accurately predict the fitness of marine ectotherms under the climate change scenarios, interactive effects from multiple environmental stressors should be considered, such as ocean acidification (OA), ocean warming (OW) and diurnal temperature cycling (DTC). In this work, we evaluated and compared the antioxidant capacity and metabolism homeostasis of two sea urchins, viz. the temperate species Strongylocentrotus intermedius and the tropical species Tripneustes gratilla, in response to oceanic conditions under a climate change scenario. The two species were treated separately/jointly by acidic (pH 7.6), thermal (ambient temperature + 3 °C), and temperature fluctuating (5 °C fluctuations daily) seawater for 28 days. The activities of antioxidant enzymes (catalase and superoxide dismutase) and the cellular energy allocation in the urchins' gonads were assessed subsequently. Results showed that exposure to OA, OW, and DTC all induced antioxidant responses associated with metabolism imbalance in both S. intermedius and T. gratilla. The physiological adjustments and energy strategies towards exposure of OA, OW, and DTC are species specific, perhaps owing to the different thermal acclimation of species from two latitudes. Moreover, decrease of cellular energy allocation were detected in both species under combined OA, OW, and DTC conditions, indicating unsustainable bioenergetic states. The decrease of cellular energy allocation is weaker in T. gratilla than in S. intermedius, implying higher acclimation capacity to maintain the energy homeostasis in tropical urchins. These results suggest that climate change might affect the population replenishment of the two sea urchins species, especially for the temperate species.