Climate change impacts all forms of life – including seaweeds! For farmed Eucheuma/Kappaphycus the direct and indirect impacts have caused not only physical damage to the crops but has also affected the eco-physiological, reproductive and metabolic processes of the seaweed. As a result of their importance as sources of different types of carrageenan, Eucheuma (iota)/Kappaphycus (kappa) have spread, through facilitated transfer, from its original tropical farming sites in the Philippines, across several localities in the Pacific, Atlantic and Indian Oceans. Ocean warming has caused the ‘tropicalization’ of sub-tropical waters of northeast Asia and South America, and more areas are becoming increasingly conducive to Eucheuma/Kappaphycus farming. Increases in surface seawater temperatures could have deleterious effects on reproductive capacity, including spore production, germination, recruitment and growth which, coupled with the long-practiced clonal propagation, have resulted in the declining productivity and quality of extracted colloids. Global climate change and anomalous climatic events such as El Niño and La Niña have increased the susceptibility of the selected cultivars of farmed eucheumatoids to bacterial pathogens as a result of stressful abiotic conditions which are conducive to ‘ice-ice’ disease and damaging impacts of epiphytism which have combined and literally wiped out activity in some farms. Typhoons and storms, as well as heavy rainfall during the wet season, increased in intensity by climate change, have also destroyed farms resulting in the loss of investments and income for those workers dependent on seaweed cultivation as a cash generating activity.
In addition, increased CO2 dissolution in the oceans has resulted in its acidification, coupled with exposure of the surface-cultivated seaweeds to increased UV radiation (due to ozone depletion), which could decrease the concentration of the seaweeds’ own protective pigments, thereby resulting in photo-inhibition and abiotic stresses. All of the foregoing, individually and collectively, integrate to reduce daily growth rates. Reduced pH could also lessen the spore germination capacity of cultivated eucheumatoids.
The combination of the above factors has produced an overall decline in cultivated Eucheuma/Kappaphycus production. However, the efforts of many countries to increase their total area of farming and improvement in farming techniques, ensures the world’s overall production trend for these seaweeds of industrial value to be on the rise, in general.
Largo D. B., Chung I. K., Phang S.-M., Gerung G. S. & Sondak C. F. A., 2017. Impacts of climate change on Eucheuma-Kappaphycus farming. In: Hurtado A., Critchley A. & Neish I. (Eds), Tropical Seaweed Farming Trends, Problems and Opportunities. Developments in Applied Phycology, pp. 121-129. Springer, Cham. Chapter (subscription required).
