Sustainable Marine Aquaponics: Effects of Shrimp to Plant Ratios and C/N Ratios

Abstract

Integrated aquaponic food production systems are capable of producing more food on less land using less water than conventional food systems, and marine systems offer the potential of conserving freshwater resources. However, there have been few evaluations of species combinations or operational parameters in marine aquaponics. The goal of this experiment was evaluation of stocking density ratio of Pacific whiteleg shrimp (Litopenaeus vannamei) to three edible halophytes (Atriplex hortensis, Salsola komarovii, and Plantago coronopus) with two C/N ratios in a 3 × 2 factorial design. There were three stocking density ratios (shrimp: plant), 2:1, 3:1, and 5:1; and two C/N ratios, 12 and 15. The results indicated that stocking density ratio exerted a significant impact on shrimp growth. Shrimp reared in 2:1 and 3:1 treatments had better growth performance. In contrast, plants were affected by both stocking density ratio and C/N ratio. Halophytes grown in stocking density ratios of 3:1 and 5:1 with a C/N ratio of 15 had better growth performance and nutrient content. The concentrations of TAN and NO2– were below 0.2 mg/L throughout the experiment, including the higher stocking density ratio treatments. In conclusion, the stocking density ratio of 3:1 with a C/N ratio of 15 was suggested as the optimal condition for the operation of marine aquaponics in which whiteleg shrimp and the three halophytes are target crops.

Optimal Dietary Crude Protein in Commercial Feeds for Shrimp and Halophytes in Marine Aquaponic Biofloc Systems

“…In the interim between experiments, evaporative losses were replaced with well water, constant aeration was provided to all subsystems and probiotics (EZ-Bio, Bacillus spp., Zeigler Brothers, Gardners, PA, United States) were added weekly at a dose of 10 ppm EZ-bio once a week. Once shrimp moved into experimental units, additional doses of probiotics were added every other day in the 1st week, twice per week in the 2nd week, and once per week beginning in the 3rd week continuing until the end of the experiment (Crab et al, 2010;Chu, 2014;Chu and Brown, 2021b). Molasses (Hawthorne Gardening Co., Vancouver, WA, United States) was provided as an organic carbon source for the adjustment of C/N ratio.…”

“…This result aligned with the findings reported by other researchers (Otoshi et al, 2011;Cerozi and Fitzsimmons, 2016;Chu and Brown, 2021a,b). TAN can be stabilized and remain below 0.1 mg/L within 3 weeks in new systems via inoculating probiotics on a regular basis (Cerozi and Fitzsimmons, 2016;Chu and Brown, 2021b). demonstrated that the concentrations of TAN and NO 2 − remained under 0.51ppm and 1.25 mg/L, respectively, by introducing biofloc from an established system prior to the experiment.…”

“…The objective of this study was evaluation of varying concentrations of dietary crude protein in practical diets fed to shrimp raised in biofloc aquaponic saltwater systems. (Chu and Brown, 2021b). Briefly, each aquaponic system had 113.6 L aquaculture tank, a 102.2 L hydroponic tank, and an 18.9 L biofilter tank.…”

Environmental pH and Supplemental C Exert Little Impact on Shrimp, but Profound Impacts on Plants in Marine Aquaponics

“…Nutrient flows in aquaponics varies as a function of feeding frequency and regime, feed amounts, animal to plant ratio, hydraulic loading rate, subsystem ratio, and pH [9][10][11][12][13][14][15][16]. Environmental pH plays a critical role in nearly all chemical reactions in water, and influences physiological functioning of aquatic animals, plants, and microorganisms [4,13,[17][18][19][20].…”

“…the probability of a pH conundrum in marine or brackish water aquaponic systems may be less than in freshwater systems. Nevertheless, Chu and Brown [9,21] mentioned that pH was a possible factor influencing growth of the halophytes they evaluated. The ideal range of pH for an integrated system that includes aquatic animals, plants and bacteria in marine aquaponics remains largely unknown and may significantly influence compatibility of biotic subsystems and significantly influence outputs.…”