Optimization of Macroalgal Density and Salinity for Nutrient Removal by Caulerpa lentillifera from Aquaculture Effluent

Abstract

Determining the optimum levels of macroalgal density and salinity for removing aquaculture effluent has gained increasing research interest in recent years because of the growing concerns over environmental sustainability. Here, we determined the effects of macroalgal density and salinity on the uptake of NO2−, NO3−, NH3, and PO43− by Caulerpa lentillifera from the effluent of Poecilia latipinna using spectrophotometry. Laboratory experiments were conducted to measure nutrient uptake at five different macroalgal density levels (10, 20, 30, 40, and 50 g/L) and three salinity levels (20, 30, and 40 ppt) with and without aeration. Quadratic regression analysis revealed significant nonlinear and linear effects of macroalgal density on the uptake of NO2−, NO3−, NH3, and PO43−, where the maximum uptake was predicted to occur at the macroalgal densities of 31.6, 33.3, 50.0, and 20.0 g/L, respectively. Likewise, the effects of salinity on the uptake of NO2−, NO3−, NH3, and PO43− were significant and nonlinear where the maximum uptake was predicted to occur at the salinity levels of 29.1, 30.7, 29.5, and 29.5 ppt, respectively. The result of the effects of aeration was mixed but somewhat indicated a positive effect on the nutrient uptake within the 24 h period. Our results could help aquaculturists to minimize the excessive nutrients by C. lentillifera from aquaculture effluent while achieving long-term sustainable aquaculture production.

Capacity of Caulerpa lentillifera in the Removal of Fish Culture Effluent in a Recirculating Aquaculture System

“…The C:N ratio also helps determine whether the macroalgae are faced with a condition of deficiency in N. When it exceeds 15, it means that N is limited. In our study, both the initial and final C:N ratios indicate that there was no N limitation for seaweed growth [35,46].…”

“…These conditions were applied to the outdoor experiment in the current study to run the integrated circulation system. In addition, water motion or bubbling is crucial for the nutrient uptake and macroalgal growth [35], and aeration showed a positive effect on nutrient uptake by C. lentillifera in laboratory experiments [34]. Therefore, macroalgal culture units were aerated using fish culture units, and seaweed units were aerated using air stones.…”

“…There was sufficient illumination because transparent sheets were set at the roof. Maintenance of water quality (physical, chemical, and biological characteristics) in culture systems is crucial for the production and survival in aquaculture [15,20,35]. During the study period, biological, physical, and chemical parameters were monitored.…”

“…In general, nutrients are classified into three main groups: macronutrients, micronutrients or trace elements, and vitamins [35]. Therefore, future research is recommended to focus on the analysis of a complete set of available nutrients, their concentrations in the effluent, and other limiting factors affecting the macroalgal growth in the integrated system.…”

Utilization of the light density to reduce the development of <i>Lyngbya</i> sp. and their growth on <i>Caulerpa lentillifera</i> J. Agardh in a recirculating aquature system

“…Other studies showed that the seaweed might even be used in medicine as an anti-diabetic agent [7] and dye industries [8,9]. Besides those properties, C. lentillifera has shown the potential ability to remove nutrients from aquaculture effluent [10][11][12][13] and heavy metals from wastewater [9,14]. However, it has been documented that their culture in ponds might become a problem because they absorb heavy metals [3] and for this reason, it might be interesting to culture them in a controlled system.…”