Gustavo Gonzaga Henry-Silva

Este estudo avaliou a capacidade de suporte para produção de tilápia-do-Nilo (Oreochromis niloticus) em tanquesrede em reservatórios do semiárido brasileiro durante uma seca suprassazonal. O mesmo Utilizou modelos de balanço de massa de fósforo para estimar a assimilação de nutrientes, com limites de concentração de fósforo na coluna d’água foram estabelecidos em 30 μg.L⁻¹, segundo a legislação brasileira, e 60 μg.L⁻¹ para ambientes eutrofizados. No reservatório de Santa Cruz, a capacidade de assimilação foi de 5.848 kg.ano⁻¹ a 60 μg.L⁻¹, enquanto em Umari foi de 572,7 kg.ano⁻¹ a 30 μg.L⁻¹ e 4.620 kg.ano⁻¹ a 60 μg.L⁻¹. As capacidades de suporte para produção foram 680 toneladas em Santa Cruz a 60 μg.L⁻¹ e em Umari, 63 toneladas a 30 μg.L⁻¹ e 508 toneladas a 60 μg.L⁻¹. Apesar das maiores emissões de fósforo em Umari, Santa Cruz apresentou maior capacidade a 60 μg.L⁻¹ devido ao maior volume de água. O estudo ressalta a importância da morfometria e dos parâmetros hidrológicos para a aquicultura em secas extremas, propondo, por meio de modelos de balanço de massa, práticas que equilibram produção e conservação ambiental.

Water scarcity is a critical global issue, especially in semiarid regions where limited water resources are increasingly pressured by socioeconomic vulnerabilities and agricultural demands. In this study, we evaluated the quality of water and sediment from intermittent streams in a watershed located in Brazil’s semiarid northeastern region, assessing their suitability for irrigation while considering the influence of different land uses. Based on the Brazilian Environmental Council classification, we found that 82% of the sampled sites were categorized as freshwater, indicating general suitability for irrigation. However, the hydrochemical and sediment analyses revealed significant anthropogenic impacts, particularly at agricultural and urban sites, where higher levels of salinity, nutrients, heavy metals, and other pollutants were observed. Moderate salinization risks were noted at 70% of the sites, primarily linked to anthropogenic land-use practices, with total dissolved solids, chlorides, and bicarbonates emerging as key indicators of degradation. Riparian forests demonstrated a notable buffering effect, reducing salinity and nutrient levels, although elevated concentrations of manganese and iron were also detected, likely due to natural geochemical mobilization and upstream contamination. These results highlight the critical role of riparian vegetation in mitigating environmental impacts and emphasize the need for targeted soil and water management strategies, such as crop selection, irrigation practices, and land-use planning. By addressing the combined effects of land use and natural pressures on water quality, we provide essential insights for sustainable irrigation and resource management in semiarid regions, supporting both agricultural productivity and ecological preservation. Graphical abstract

The use of autochthonous zooplankton species, along with standardized protocols, ensures the reliability and reproducibility of ecotoxicological assays, enabling the anticipation and more efficient diagnosis of the harmful effects of toxic agentes in aquatic environments. The objective of this study was to evaluate the viability of laboratory cultivation of Ceriodaphnia cornuta under physical and chemical conditions similar to those of freshwater environments in a semiarid region, aiming to minimize uncertainties regarding the adaptability of test organisms in ecotoxicological assays with environmental samples. To this end, individuals of the species C. cornuta were collected from reservoirs in a semiarid region of Brazil. Subsequently, experiments were conducted with acute and chronic exposures, using different values of pH, hardness, temperature, and luminosity, based on the averages found in aquatic environments of semiarid regions and those suggested by standardized norms. Ceriodaphnia cornuta showed the highest survival and reproduction rates in water with a pH between 7.5 and 7.9, hardness of 66mg CaCO3.L-1, temperature of 25 °C ±2, and luminosity between 3000 to 3500 lux, these values are above those standardized by the Brazilian standard, demonstrating a potential viability of its cultivation under conditions similar to those of neotropical semiarid regions for use as a test organism in quality analyses of these environments.

The present study evaluated economic, environmental and social sustainability of three production strategies of Pacific white shrimp (Litopenaeus vannamei) during a regional outbreak of white spot syndrome virus. The strategies mainly differed by stocking densities (92, 14, 8 larvae.m-2; D92, D14, and D8, respectively), fertilizer inputs, and other general management. Each dimension of sustainability was evaluated using sets of indicators. The D14 and D8 strategies showed greater economic feasibility than D92 because of the reduced operational costs and investments to buy post-larvae and feed. All strategies showed moderate environmental sustainability but had weakened economic and social sustainability due to the virus. The D14 and D8 strategies received the highest overall sustainability index. The D92 was the most environmentally favorable management strategy and had a social tendency. In general, shrimp mariculture performed with a high initial stocking density cannot guarantee the return of invested capital. The lower density strategies were economically feasible due to the high prices paid per kilogram of shrimp as a function of the higher individual average weight. However, economic feasibility of these two strategies coincided with low creation of employment opportunities and income, decreased social sustainability, and increased environmental impact.

Aim i) is there a difference in the level of contamination in the different parts of the basin in the water, sediment and aquatic macrophytes compartments? and ii) do the three compartments respond similarly to metal contamination? Methods Samples of water, sediment and aquatic macrophytes (Salvinia auriculata Aubl., Pistia stratiotes L., Ludwigia helminthorrhiza (Mart.) H. Hara and Eichhornia crassipes (Mart.) Solms) were collected at 10 sampling sites in different stretches of a tropical hydrographic basin. We determined the metal concentrations of Fe, Pb, Ni, Zn, Mn, Cr, Cu and Cd, and to the results we applied Principal Component Analysis (PCA), separately for each compartment, to order the sampling sites. Results Fe and Mn had higher concentrations than other metals in plants and sediment. With the exception of Mn, the order of metals was similar between water and sediment. However, the PCAs ordered the sampling sites differently. Our results demonstrated that the ordering of sampling sites by metal concentrations differs among water, sediment and macrophytes. Conclusions We conclude that to evaluate the contamination of aquatic environments by metals and the effects of contamination on the food chain, it is not enough to evaluate them only in water or sediment, but also in an aquatic community.

O objetivo do presente estudo foi avaliar a sustentabilidade ambiental, social e econômica da bacia hidrográfica do rio Apodi/Mossoró (RN), semiárido brasileiro. A bacia foi dividida em quatro trechos: alto curso, médio curso superior, médio curso inferior e baixo curso. Os locais de amostragens foram distribuídos ao longo da bacia hidrográfica para obtenção dos valores das seguintes variáveis limnológicas: oxigênio dissolvido, nitrogênio total, fósforo total e coliformes termotolerantes. As informações relacionadas aos indicadores econômicos e sociais foram adquiridas junto ao Instituto Brasileiro de Geografia e Estatística – IBGE. A sustentabilidade foi avaliada por meio do modelo conceitual implementado com o auxílio do software Multisectorial, Integrated and Operational Decision Support System for Sustainable Use of Water Resources at the Catchment Scale (MULINO mDSS). Na bacia hidrográfica do rio Apodi/Mossoró o trecho mais sustentável foi o baixo curso, com menor amplitude de variação entre os escores das dimensões econômica, ambiental e social. Este trecho foi considerado como potencialmente sustentável, apresentando melhor desempenho nas dimensões social e econômica, no entanto, comparativamente, exibiu menor escore para a dimensão ambiental do que os demais trechos da bacia hidrográfica. Isto evidencia que o trecho de baixo curso possui maior desenvolvimento econômico e social, entretanto, apresenta mais problemas ambientais. O trecho de alto curso foi classificado como de baixa sustentabilidade. Já o trecho de médio curso superior se destacou na dimensão ambiental, mas por não apresentar escores proporcionais nas dimensões social e econômica, o seu índice geral foi de baixa sustentabilidade. O trecho de médio curso inferior apresentou média sustentabilidade. Assim, foi evidenciado que ambientes que são mais desenvolvidos economicamente tendem a apresentar mais problemas ambientais, entretanto, ainda podem ser considerados mais sustentáveis devido ao maior desenvolvimento econômico e social.

The present study evaluated a polyculture system with Pacific white shrimp (Litopenaeus vannamei) and the macroalga Gracilaria birdiae and its potential to remove nutrients. The experimental design consisted of a shrimp monoculture of 100 animals/m² (T0) and three multitrophic cultures with L. vannamei (100 animals/m²) and with G. birdiae at densities of 500 (T500), 1000 (T1000), and 2000 (T2000) g/m². Nitrogen and phosphorus concentrations decreased at the beginning of the experiment in the treatments with macroalgae, but this reduction was not maintained throughout the cultivation period. The stable values of G. birdiae biomass were perhaps related to the high turbidity of the water. There was an increase in shrimp biomass during cultivation, which reached the final individual averages of 7.5 g (T0), 7.6 g (T500), 5.9 g (T1000), and 7.5 g (T2000), with no significant differences between treatments. Nevertheless, the absence of macroalgae growth provides no added profit for the producer. Thus, there is no economic advantage in using G. birdiae in an integrated multitrophic system with L. vannamei at a high density and conditions of high water turbidity.

Water reservoirs have been constructed in hot semi-arid regions, which may be used to produce fish. The present study described major features of the economic, social, and environmental characteristics of a net-cage Nile tilapia production system, stocked with 100 and 120 fish/m³, implemented in a reservoir in the hot semi-arid region of Brazil during an extended drought event. The production cycle was reduced from 6-8 to 4 months because of the lack of water in the reservoir. This resulted in the harvest of small fish weighting ~300–350 g that reached a low value in the market. As a consequence, indicators of financial feasibility showed low values, which were not attractive for entrepreneurs. Nevertheless, for both stocking densities, the monthly income was about US$ 1,500.00, which is 5-fold the minimum wage in the region. In general, the activity has a positive social impact, despite the low contribution to development of the local economy and food security because most supply came from outside and fish were sold to distant regions. Various age and ethnic groups were represented among the employees, but the enterprise was operated only by men. Phosphorus accumulations in the reservoir were 2.1 and 2.0 kg/t of fish produced and particulate material accumulations of 110 and 100 kg/t of fish production for 125 fish/m³ and 100 fish/m³, respectively. The study indicated that the Nile tilapia culture in hot semi-arid region is strongly affected by long drought events and adaptations in the planning and management should be done when implementing the systems. However, it seems that the activity has some resilience to still provide food, generate wealth, and promote social development for local population with low environmental impact.

Stakeholders in the aquaculture industry are currently seeking the development of sustainable production systems and methodologies to measure sustainability. The present study evaluated the environmental, social and economic dimensions of sustainability of a net-cage tilapia production system with two stocking densities implemented in a reservoir in the semi-arid northeast region of Brazil during an extended drought event. The three dimensions of sustainability were evaluated through a set of 33 indicators. The Internal Rates of Return were below the Minimum Attractive Rates of Return and the Net Present Value indicator was negative for both stocking densities, showing no attractive financial benefits and no capital return capable of generating sufficient annual profits and revenues to keep the system in operation over time. The activity improved the local food supply and quality of animal protein in the state where the enterprise is carried out. Compensation of labor represented 22 and 24% of the production costs with 125 and 100 fish/m³, respectively. Various age groups and ethnic groups were represented among the employees, but the enterprise was operated only by men. Phosphorus accumulations were 2.1 and 2.0 kg/tonne and particulate material accumulations of 110 and 100 kg/tonne for 125 fish/m³ and 100 fish/m³, respectively. The prolonged drought conditions that occur in the Brazilian semiarid region can compromise the environmental, economic and social sustainability of fish farming in reservoirs in the region.