Banca de DEFESA: ANA PAULA DALBEM BARBOSA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ANA PAULA DALBEM BARBOSA
DATA : 28/01/2026
HORA: 08:00
LOCAL: Nijmegen, Holanda - Radboud University
TÍTULO:

Nutrient fluxes in aquaculture systems: From feed to fish and the environment

PALAVRAS-CHAVES:

fish farming, nutrients, carbon, nitrogen, phosphorus

PÁGINAS: 138
GRANDE ÁREA: Ciências Biológicas
ÁREA: Ecologia
RESUMO:

Aquaculture is a strategic activity for the sustainable production of aquatic-origin food, playing na essential role in global food security. As the demand for fish continues to grow, the intensification of aquaculture practices requires careful attention to nutrient management, encompassing fish feeding, nutrient assimilation into fish biomass, waste production, and environmental discharge. Beyond productivity, sustainable aquaculture must address its ecological footprint and its role in circular resource use. This thesis explored the flow and transformation of nitrogen, carbon, and phosphorus in aquaculture systems, emphasizing both the ecological implications and opportunities for more sustainable nutrient use. The first article presented a systematic review of studies published over the past 40 years on nutrient balance in freshwater aquaculture, with a focus on earthen ponds – a dominant production system in many regions. The review identified inlet water, feed, and fertilizers as the primary nutrient inputs. While fish assimilate a significant fraction of these inputs, a substantial portion accumulates in pond sediments. These findings highlight the dual role of sediments as both nutrient sinks and potential sources of pollution. The study pointed out the importance of integrated nutrient management strategies that increase efficiency while mitigating long term ecological risks. Building on this foundation, the second article evaluated nutrient budgets, and the efficiency of carbon, nitrogen, and phosphorus use in monoculture systems of grass carp (Ctenopharyngodon idella) and Nile tilapia (Oreochromis niloticus), as well as in polyculture systems. Over a complete production cycle in nine experimental ponds, we monitored water quality, fish growth, and sediment characteristics. The results showed that Nile tilapia exhibited higher productivity and nutrient use efficiency, reflecting more effective feed conversion. Sedimentation emerged as a key mechanism for phosphorus retention, while fish biomass contributed significantly to nitrogen and phosphorus outputs. Moreover, gas fluxes – primarily carbon dioxide (CO2) diffusion – accounted for important carbon losses, reinforcing the need to consider atmospheric pathways in carbon budgeting. The third article extended this investigation by quantifying greenhouse gas (GHG) emissions from aquaculture ponds over a complete production cycle. We compared CO2 and methane (CH4) emissions across monoculture and polyculture systems and estimated the carbon footprint of each production model, including both direct and indirect emissions. Regarding direct emissions, polyculture ponds showed lower cumulative CO2eq emissions than monocultures (Nile tilapia and grass carp). The carbon footprint per kilogram of fish was approximately 17 kg CO2eq for Nile tilapia monoculture and polyculture systems, compared to 23 kg CO₂-eq for grass carp monoculture, with the higher value primarily driven by indirect emissions, especially land use change associated with soybean production. The final article investigated a potential solution for one of aquaculture’s most persistent by-products: nutrient rich pond sediments. We tested the reuse of these sediments as fertilizers in arugula (Eruca vesicaria) cultivation, comparing materials from extensively and semi-intensively managed ponds with commercial fertilizers. While sediment treatments produced lower plant biomass, they improved soil nutrient content and fertility. Na economic analysis indicated that sediment reuse could significantly lower input costs, offering a low-cost, environmentally friendly fertilization strategy, especially relevant for smallholder farmers. This study highlights sediment reuse as a pathway toward integrated aquaculture-agriculture systems and circular economy models, where waste is transformed into a resource. Taken together, the findings of this thesis demonstrate that strategies such as polyculture, nutrient budgeting, GHG mitigation, and sediment reuse are key tools for enhancing the environmental and economic sustainability of aquaculture. These approaches foster a more circular and ecologically balanced production model, aligning food production with the goals of environmental conservation and climate responsibility.

MEMBROS DA BANCA:
Presidente - 65536013 - CLAUMIR CESAR MUNIZ
Interno - 118188003 - ERNANDES SOBREIRA OLIVEIRA JUNIOR
Externa à Instituição - 544.259.641-87 - LUCIA APARECIDA DE FATIMA MATEUS - UFMT
Externa à Instituição - SARIAN KOSTEN - RU
Externa à Instituição - SIMONE CARDOSO - UFJF
Interno - 118181001 - WILKINSON LOPES LAZARO