Alessandra Augusto

Understanding how coastal organisms respond to extreme environmental conditions is essential for assessing ecosystem vulnerability under climate change. This study evaluated how mangrove degradation and seasonal extremes interact to influence lethal and sublethal responses in a mangrove fiddler crab, a sentinel species widely distributed in subtropical mangroves. In situ mesocosms were established in preserved and disturbed (dead vegetation) mangroves of the Yucatán Peninsula, Mexico, to quantify how habitat condition modulates physiological performance under multiple concurrent stressors. Experiments encompassed contrasting seasonal extremes characteristic of the region: dry-season heatwaves and prolonged rainy-season flooding. In degraded mangroves during the dry season, synergistic effects of elevated temperature and hypersalinity induced oxidative imbalance, increased antioxidant demand, and elevated mortality. In contrast, rainy season mesocosms showed that extended flooding compromised osmoregulatory capacity and suppressed metabolic oxygen consumption. Biomarker analyses revealed that the hepatopancreas and gills were the main organs mediating stress responses, as indicated by heightened antioxidant and cholinesterase activities under combined climatic and habitat stress. Overall, the interaction between climatic extremes and habitat degradation reduced the physiological buffering capacity of a mangrove crab, highlighting diminished resilience to compound environmental disturbances. These findings demonstrate the effectiveness of in situ mesocosm approaches for capturing vulnerabilities at the organismal and ecosystem levels and emphasize that conserving mangrove habitats is critical to mitigating the adverse effects of climate change on coastal biodiversity and ecological function.

Bycatch refers to all the animals caught with species of economic interest. These economically unattractive animals are later discarded at sea. Protein hydrolysate with antioxidant potential was extracted by our research group from two main fish species (Paralonchurus brasiliensis and Micropogonias furnieri) of the shrimp fishing bycatch fauna of the São Paulo coast, Brazil. This study tested the inclusion of different concentrations of hydrolysate (0.0, 2.5, 5.0, and 10.0%) in the diet of Macrobrachium rosenbergii. Survival, growth, and physiological processes (ingestion, defecation, hepatosomatic index, O:N ratio, metabolism, and ammonia excretion) were assessed. The inclusion of hydrolysate did not affect crucial parameters for aquaculture, such as survival, growth (about 2% in relation to initial biomass), intake, and mechanisms related to obtaining and using energy (hepatosomatic index and protein as main type of energy substrate oxidized). Metabolism and nitrogen excretion were reduced (~70%) in all treatments with hydrolysate, suggesting lower energy requirements for digestion and absorption of nutrients, as well as the optimization of animal protein use. We recommend the inclusion of 2.5% hydrolysate for future work to test the antioxidant capacity of hydrolysate in M. rosenbergii. This concentration level does not alter important physiological parameters and is cost-effective.

Environmental stressors in aquatic organisms can be assessed using a bioenergetic approach based on the evaluation of changes in their physiological parameters. We evaluated the chronic effects of cadmium (Cd²⁺) on the energy balance as well as the survival, growth, metabolism, nitrogen excretion, hepatosomatic index, oxidized energy substrate, and osmoregulation of the shrimp Penaeus vannamei with the hypothesis that the high energy demand related to the homeostatic regulation of Cd²⁺could disrupt the energy balance and as a consequence, their physiological functions. The shrimp exposed to Cd²⁺ had higher mortality (30%), directed more energy into growth (33% of energy intake), ingested 10% more energy, and defecated less than control animals. Cd²⁺ exposure caused a tendency to decrease metabolism and ammonia excretion but did not alter the hepatosomatic index, type of energy substrate oxidized, and the hyperosmorregulatory pattern of the species. The Cd⁺² exposure may have induced a trade-off response because there was a growth rate increase accompanied by increased mortality.

Increasing ocean acidification combined with other impacts may cause changes in homeostatic mechanisms of intertidal invertebrates. Stressors do not act in isolation, and experimental work is needed to assess their synergistic potential. We evaluated the effect of exposure to multiple stressors on the survival, osmoregulation, metabolism, Q10, excretion, hepatosomatic index, and energy substrate oxidation on of the fiddler crab Leptuca thayeri ( Rathbun, 1900). Crabs were exposed to two pH values (7.0, 6.3) combined with temperatures (20, 25, 30, 35, 40 °C) and these pH values combined with salinities (10, 20, 30, 40, and 50 psu) during acute exposure. All individuals died at 40 °C. Crabs osmoregulated, suggesting that the factors evaluated did not affect salt absorption or secretion. Individuals were weak hyperosmorregulators at lower salinities in the pH 7 control, but they became strong hyperosmoregulators at acidified pH 6.3. Alterations in oxygen consumption and hepatosomatic index were observed in individuals exposed to the acidified pH combined with temperatures or salinities, compared to those kept in the control pH. Q10 was elevated under an acidified pH, with crabs using proteins and lipids as energy substrates. The interaction between reduced pH and temperature or salinity thus affected physiological mechanisms related to the energetic metabolism, but elevated temperatures are more limiting because they affected survival. These physiological effects of acute exposure offer clues about extreme climatic events, which have a short duration but can affect the related energy demands.

Os espaços não-formais de educação ganham a cada dia mais representatividade na sociedade, como locais de difusão das ciências. Neste trabalho avaliamos o processo de mediação, verificando como a formação reflexiva interferiu naquele processo e na organização da exposição. As visitas foram categorizadas pela metodologia de “Conversas de Aprendizagem” proposta por Sue Allen. Verificamos que a ocorrência de diferentes categorias de conversas variou nos diferentes momentos da exposição, com maior engajamento intelectual e afetivo do visitante, reflexo da atuação dos mediadores e estruturação da exposição. Formação, mediação afetiva e organização formam uma tríade inseparável, e este deve ser foco das instituições que trabalham com a difusão científica.