Assessing The Feasibility and Impacts of Introducing Seaweed Cultivation in Shrimp Farming Ghers/Ponds in Coastal Regions of Bangladesh

Abstract

To assess the feasibility and ecological impacts of introducing seaweed cultivation into shrimp farming systems, a comparative cultivation trial of Gracilaria sp. was conducted from October 2023 to March 2024 across pond and nearshore environments in Cox’s Bazar, Bangladesh. The study employed a total of 18 experimental plots—9 in shrimp ponds (ghers) and 9 in nearshore waters—spanning both surface and bottom layers. In the nearshore environment, cultivation was conducted using floating long-line systems at the surface and off-bottom long-line and off-bottom net systems at the bottom, whereas in pond conditions, floating long-line and floating net methods were applied at the surface, with a broadcast technique used for bottom-layer cultivation. A two-way ANOVA revealed that the biomass production was significantly influenced by both cultivation environment and layer, with nearshore environments yielding substantially higher values (1.47 ± 0.68 kg m⁻²) than ponds (0.19 ± 0.09 kg m⁻²), and greater productivity at the surface (1.04 ± 0.98 kg m⁻²) compared to the bottom layer (0.62 ± 0.52 kg m⁻²). The proximate composition of Gracilaria sp. was also significantly affected by environment and layer, with nearshore and surface-grown seaweeds exhibiting notably higher protein, lipid, ash, and fiber contents compared to pond-cultivated seaweeds, which consistently showed lower nutritional values across all parameters. The amino acid concentrations of Gracilaria sp. were also substantially higher in nearshore grown seaweeds, whereas the effect of cultivation layer remained relatively minor across most amino acids. A total of 50 distinct phytochemical compounds were identified through GC-MS analysis in both pond and nearshore cultivated Gracilaria, with their concentrations showing clear variations based on cultivation environment and layer, reflecting different accumulation patterns under different culture conditions. Among the 13 essential minerals detected, Na, K, Fe, Co, and Cu were more abundant in nearshore-cultivated Gracilaria, whereas Ca, Mn, Se, and Rb were predominantly enriched in pond-grown seaweeds. Among the four identified heavy metals, Cr and Pb showed significantly higher accumulation in nearshore- and pond-grown Gracilaria, respectively, while Cd and Hg levels remained relatively stable across all cultivation conditions. The study also revealed that although the antioxidant levels in Gracilaria remained consistent across cultivation environments, flavonoid content was markedly elevated in nearshore-cultivated seaweeds (192.13 ± 35.50) compared to those grown in ponds (44.07 ± 15.50). The x findings of the study demonstrated that surface based floating net systems could be a promising culture technology for the production of Gracilaria sp. in shrimp farming ghers/ponds in coastal regions of Bangladesh.