Differential response of varying temperature and salinity regimes on nutrient uptake of drifting fragments of Kappaphycus alvarezii: implication on survival and growth

Commercial cultivation of seaweeds has improved the livelihood of coastal fishermen in several developing countries. Along with success story of the commercial cultivation of popular carragenophyte Kappaphycus alvarezii (Rhodophyta), there have been concerns about its invasive tendencies. Substantial quantities of algal fragments disperse during farm maintenance, specifically during harvesting. It is believed that the drifting fragments eventually die on the sea bottom. In the present investigation, drifting fragments (live, semi-bleached, and bleached) were incubated under different salinity (20, 25, 30, 35, and 40%) and temperature (15, 20, 25, 30, and 35 degrees C) regimes to record daily growth rate (DGR). NO3-N, PO4-P, and SiO3-Si uptake was evaluated for live fragments under similar culture conditions at 72 h interval in case of live fragments. The highest uptake (99 %) was recorded for NO3-N at 30 degrees C in 30 degrees, while the lowest (62 %) was recorded for SiO3-Si at 35 degrees C in 20 parts per thousand. After 30 days of laboratory incubation, culture fragments were outplanted into the open sea to evaluate their survival efficacy and growth. The highest DGR (7.116%) was observed in fragments which were priorly incubated at 20 degrees C in 20 parts per thousand salinity followed by a DGR of 4.85 % at 30 degrees C in 30 parts per thousand. The overall findings reveal that conducive temperature and salinity, along with survival efficiency due to bioavailability of required nutrients and regeneration capacity of drifting fragments, play crucial role in determining the establishment of K. alvarezii population in the wild.