Nitrogen and phosphorus dynamics in Nile tilapia farming in excavated rearing ponds

Abstract

The purpose of this study was to determine the total nitrogen (TN) and total phosphorus (TP) balance during intensive tilapia farming in excavated ponds. To quantify TN and TP released into the environment, the supply water, effluents at the harvest time, fish composition, feed, and sediment were analysed. The mass balance between the amount of nutrients that is inserted through the feed, which is transformed into biomass by the fish and is retained in the sediment was calculated based on dry matter. The nutrient load arriving from the supply water was calculated as a function of the concentration of TN and TP. The TN and TP dynamics during the harvesting process in three different pond sizes identified that, on average, 2.37% of TN and 2.05% of TP inserted into the system during rearing is eliminated with 10.64% TN and 37.01% TP are retained in the sediment. The TN and TP input into the system occurs through the water supply, young fish, and the feed, the latter being responsible for about 92.87% TN and 96.05% TP. The feed composition indicates that the P level of the food is above the nutritional recommendations for the species. The amount of TP accumulated in the sediments indicates that there is a need for good management practices for water quality during the rearing and sediment management period before the beginning of a new production cycle.

Geographic information system as a tool for assessing ponds and the potential for environmental impact caused by fish farming

“…Bernardi et al (2012) highlighted the importance of the hydrographic basin as an environmental management unit, and it is necessary to analyze agricultural activities with modern technological tools such as geotechnologies, as these help obtain technical information that can serve as a decision-making tool for monitoring impacts caused by intensified production. Macedo and Sipaúba-Tavares (2010) affirmed that aquaculture activity causes a nutrients increase in the aquatic environment, increasing the phytoplankton production, leading to changes in the aquatic system, which was confirmed by Coldebella et al (2020). Analyzing the fishery in several fish farms in the western region of Paraná, the results indicated that the concentrations of total solids, chemical oxygen demand (COD), and total phosphorus (TP) increased significantly in the harvest, causing a deterioration of the effluent released into the environment.…”

“…The potential environmental impact of fish activity in the basin was based on a study by Coldebella et al (2020), in which the values of total nitrogen (TN) and TP that remain in the environment and what is discharged into the crop effluent, considering the area of the ponds mapped.…”

“…As shown in Table 2, it is possible to verify that the nitrogen supply retained in the ponds is less than that released in the receiving body by the effluents, and this causes the eutrophication of the aquatic environments. As demonstrated by Coldebella et al (2020), when analyzing the dynamics of nitrogen (N) and phosphorous (F), their low retention in the pond sediment causes the effluents to receive most of the inputs from the entry of these nutrients into the system, causing the eutrophication of the water bodies. According to Correl (1998), this occurs due to the use of feed and fertilizers, and in all the Arroio Marreco basin, most rural properties have ponds in conjunction with other agricultural activities (e.g., poultry, swine, and dairy cattle).…”

“…Thus, it is possible to calculate the eutrophic loads of nutrients released by the fish farm effluent per hectare and to estimate values for a small or large area. Based on the study by Coldebella et al (2020), the quantification of nitrogen (N) and phosphorus (F) in ponds for fish farming is important to evaluate the management of the quality of water and effluents released into water bodies.…”

Bivalve mollusk shell powder: a sustainable alternative for alkalinity and pH correction in aquaculture.

“…Among the most important limnological aspects of aquatic life, most notable is the acid-base balance of water, which is directly related to pH and alkalinity (Coldebella et al 2020). Water acidity problems are not the direct result of the effects of low pH, but rather the result of the effects of low total alkalinity and the presence of acidic sediments at the bottom of the ponds (Quispesivana et al 2016).…”