Establishment and performance of sea purslane (Sesuvium portulacastrum) in marine aquaponics with hybrid grouper

Abstract

Aquaponic systems are sustainable and environmentally friendly, primarily through the recycling of nutrients. However, identifying feasible combinations that achieve favorable economic and environmental performance in a winwin mariculture system can be challenging. A novel aquaponic mariculture system was established by combining sea purslane (Sesuvium portulacastrum) with hybrid grouper (Epinephelus sp.), and its performance was assessed. Triplicate experimental fish ponds assembled with floating plant beds of sea purslane (SP group) were compared with the control (without phytotreatment, CK group) over a 56-day experimental period. The changes in major pollutants in the system and the growth performance of the plants and groupers were analyzed. The results showed that the removal rates of pollutants in the sea purslane aquaponic system were 98.1 %, 97.5 %, 89.9 % and 50.6 % for total ammonia nitrogen (TAN), nitrite nitrogen, total suspended solids (TSS) and chemical oxygen demand (COD), respectively. Furthermore, the removal rates of total nitrogen (TN), total phosphorus (TP), dissolved inorganic nitrogen (DIN), and dissolved inorganic phosphorus (DIP) were 19.6 %, 12.0 %, 18.4 % and 16.2 %, respectively, in the SP group. With respect to growth performance, the specific growth rate (SGR) of groupers in the SP group increased by 43 % compared with that in the CK group. Grouper growth in the SP group showed strong negative allometric growth, whereas isometric growth was observed in the CK group. The net growth of sea purslane increased by 4.32 ± 1.64 kg/m², with a relative growth rate of 0.90 ± 0.28 %/d, showing considerable incorporation of carbon via photosynthesis. Moreover, the sea purslane–grouper aquaponics system can be maintained at a low cost and is easily managed. In conclusion, the potential of this innovative marine aquaponic system was demonstrated, and the findings will contribute to enhancing the performance of environmentally friendly mariculture techniques in the future.