Horizontal transmission of ice-ice disease in seaweed Kappaphycus alvarezii (Doty) L. M. Liao (Gigartinales, Rhodophyta)

Background. Kappaphycus alvarezii seaweed is a major commodity of important economic value fishery cultivation that has been developed in many countries. The demand for K. alvarezii seaweed continues to increase because it produces carrageenan which is commonly used as the main raw material in many industrial activities. However, K. alvarezii’s seaweed farming is inseparable from several obstacles. In the seaweed culture system, ice-ice disease is a major obstacle because it can harm the cultivation business. Ice-ice disease causes a decrease in seaweed production. Bacteria play a role in the development of ice-ice disease in seaweed cultivation. Aquatic organisms infected with bacteria indirectly cause damage to tissue. The spread of bacterial diseases in aquatic organisms can occur vertically or horizontally. Goals. This research aims to study the horizontal transmission of ice-ice disease on growth, carrageenan content, and changes in the structure of the K. alvarezii seaweed tissue which were tested in-vivo. Methods. This study uses healthy seaweed thalus weighing 35g and seaweed thallus affected by ice-ice weighing 30g (A), 35g (B), 40g (C) and 45g (D).The parameters observed were morphological changes, carrageenan content and tissue changes with histological analysis. Result. The results of this research indicate that the transmission of ice-ice disease can occur horizontally from thallus affected by ice-ice to healthy thallus. This transmission causes discoloration that shows symptoms of ice-ice attack on healthy seaweed K. alvarezii. This discoloration is accompanied by a decrease in thallus weight. Transmission also causes changes in the structure of the tissue in the form of lysis in the tissue and reduce the content of carrageenan in K. alvarezii seaweed. Conclusions. Based on this research, it can be concluded that the spread of ice-ice disease in seaweed causes color change, weight loss, changes in tissue structure, and reduce the quality of carrageenan.