Assessing the influence of depth and location on growth performance, carrageenan yield, carrageenan properties, and biochemical profile of Kappaphycus alvarezii in Gujarat's Coastal Waters during the pre-monsoon season

Abstract

This study investigated the effects of depth and location on the growth performance, carrageenan yield, carrageenan properties, and biochemical composition of Kappaphycus alvarezii cultivated along the Gujarat coast during the pre-monsoon season (May-June 2022). Experiments were conducted at Okha, Simar, and Mithapur using a randomized block design with cultivation depths of 0, 5, and 10 m, and data were analyzed using ANOVA. Results indicated that conditions at Okha were generally favourable, while optimal growth was consistently recorded at 5 m depth across all sites. The highest biomass was observed at Okha (22.56±0.45 kg), whereas the lowest was recorded at Mithapur at 10 m (10.45±0.05 kg). Daily Growth Rate was greatest at 5 m, with Okha showing the highest rate (5.38±1.97% day⁻¹), followed by Simar and Mithapur. Carrageenan yield declined with increasing depth, with Okha showing the highest yield at all depths and Mithapur the lowest. Carrageenan gel strength increased with depth, while biochemical analysis showed increasing protein and lipid contents and decreasing carbohydrate and ash contents with depth. Environmental parameters such as temperature, salinity, pH, nitrate, nitrite, and phosphate positively influenced growth, while dissolved oxygen showed a negative correlation.