Growth rates and survival of newly cultivated wild Kappaphycus and Eucheuma strains in a test farm site during the 2023/24 extreme El Niño event

The deteriorating quality of existing eucheumatoid cultivars used for carrageenan production, coupled with non-optimal environmental conditions intensified by climate change, are among the common factors attributed to the prevalence of pests and diseases and declines in production by the eucheumatoid industry globally. To address these challenges, new strains were developed for the seaweed industry from indigenous wild eucheumatoid populations that were resilient to pests, diseases and environmental change. Three species of eucheumatoids, Eucheuma denticulatum, Kappaphycus malesianus and K. striatus, were collected from the wild in Semporna, East Malaysia and on-grown in a farm setting, using basket nets attached to cultivation lines, from May until November 2023. The timing of the study coincided with the onset of the 2023/24 El Niño, in which increased temperature and reduced ocean current velocity were correlated in this study with a greater incidence of pests and ice-ice disease, and a reduction in seaweed biomass. Eucheuma denticulatum recorded the highest survival (79.8%) over the six month study period, followed by K. malesianus (11.1%) and K. striatus (8%). Growth rates and survival varied within and between haplotypes. For the individuals that survived to the end of the study, E. denticulatum was represented by a single haplotype (EDA), K. malesianus comprised of three haplotypes (KMNEW3, KMNEW8, MY216), two of which were novel, and K. striatus was comprised of two haplotypes (KSB, KSNEW7), one of which was novel. The survived individuals were identified as potential climate-resilient strains and retained, subject to further tests on their carrageenan yield and quality.