The green seaweed, Enteromorpha intestinalis: An efficient inorganic extractive species for environmental remediation and improved performances of fed species in brackishwater integrated multi-trophic aquaculture (BIMTA) system

Abstract

Seaweed has vast utilization benefits, in terms of food, cosmetics, fertilizers, and extraction of industrial gums and chemicals. Moreover, in integrated multi-trophic aquaculture (IMTA), seaweed can be utilized as an inorganic extractive species, but a very few studies were conducted so far involving the green seaweed, Enteromorpha sp. An experimental trial of 60 days was executed to ascertain the effect of varied stocking densities of Enteromorpha intestinalis on growth parameters, survival and physiological status of milkfish, Chanos chanos and the Pacific white-leg shrimp, Penaeus vannamei, and bioremediation effect in brackishwater IMTA (BIMTA) systems. There were three BIMTA systems with different biomass densities of seaweed, 0.5 (T1), 1.0 (T2), and 1.5 (T3) kg m−3 placed in 1000 L FRP tanks stocked with C. chanos (3.50 ± 0.01 g) at 25 number m−3 and P. vannamei (4.25 ± 0.04 g) at 50 number m−3 as fed species. The control (polyculture) had same number of milkfish and shrimp with no seaweed. Three treatments and control were maintained in triplicate. The fed species were provided with a polyculture feed containing 30% crude protein at 5% of the biomass daily. The results displayed that nitrogenous and phosphorus compounds were significantly lower (P < 0.05) in all three BIMTA treatments compared to the control. A better growth (P < 0.05) of C. chanos (12.52 ± 0.24 g) and P. vannamei (14.77 ± 0.35 g) was obtained in T3 and T2 BIMTA systems, respectively when compared with the control (milkfish: 11.01 ± 0.08 g, shrimp: 11.79 ± 0.58 g). Survival in shrimp was the highest in T3 treatment, but in milkfish, survival did not vary between different systems (P > 0.05). The blood (red blood cells, white blood cells and haemoglobin) and haemolymph (haemocyanin and total haemocyte count) parameters were better in fish and shrimp, respectively under BIMTA at harvest. Presence of seaweed provided a significant positive effect on the welfare parameter (glucose), whereas stress parameters (catalase, superoxide dismutase and cortisol) were comparatively low in fed species of BIMTA treatments than that of polyculture system. This trial suggested that T2 and T3 performed better among all and E. intestinalis can be an efficient inorganic extractive species for BIMTA at the optimum stocking density of 1.0–1.5 kg m−3.