Laboratory-induced development of the ice-ice disease of the farmed red algae Kappaphycus alvarezii and Eucheuma denticulatum (Solieriaceae, Gigartinales, Rhodophyta)

Abstract

The most common perception of unfavorable environmental factors causing the ice-ice disease in the farmed seaweeds, Kappaphycus and Eucheuma, was demonstrated in this study for the first time using stressful conditions of abiotic factors in a continuous culture system. Light intensity of less than 50 μmol photon m⁻² s⁻¹ and salinity of 20% or less induced ice-ice whitening characterized by short segments at midbranches which were similar to those observed in the Philippine seaweed farms, while temperatures of up to 33–35 °C resulted in wide-scale whitening leading to complete damage of the branches. These effects were preceded by slow growth rates from an optimum of 3.7% d⁻¹ to almost −2.0% d⁻¹. Mechanical stress by wound injury did not result to ice-ice whitening similar to the above. Environmental factors observed to trigger ice-ice in the laboratory, although may not necessarily parallel those in the field, may act synergestically to produce similar effects.