Michael Roleda
Forsker
(+47) 405 57 498
michael.roleda@nibio.no
Sted
Bodø
Besøksadresse
Torggården, Kudalsveien 6, NO-8027 Bodø
Forfattere
Hasriani Ayu Lestari Fahrurrozi Izzuddin Wahyu Purbiantoro Yanti Inneke Nababan Zaenal Arifin Siregar Hikmaturrohmi Hikmaturrohmi Eka Sunarwidhi Prasedya Michael RoledaSammendrag
The ice-ice disease (IID) impacting the commercially important eucheumatoid seaweed Kappaphycus striatus is characterized by thallus bleaching (whitening), softening, and subsequent disintegration of the affected tissue. The occurrence of IID is thought to be stress-related release of dissolve organic carbon exudates that are utilized as substrate for microbial growth. The presence of pathogenic bacteria can subsequently induce IID manifestations that can jeopardize crop health. In this study, we investigated the role of pathogenic bacteria isolated from diseased green cultivar of K. striatus in inducing IID symptoms in healthy non-axenic brown cultivar of the same species under controlled laboratory conditions. Healthy branches of K. striatus were exposed to four distinct bacterial strains: three isolated from the diseased K . striatus ( Vibrio brasiliensis strain A8, V . brasiliensis strain B2 and V . chemaguriensis strain V1) and a positive control Cytobacillus solani strain-V2. Over a period of ten days, routine administration of each bacterium was conducted during the daily renewal of the filtered seawater medium. The occurrence of symptoms, i.e., typical of IID infection, was observed in samples subjected to additional bacterium but not under the control condition with natural microbiome. Our findings suggest that the presence of pathogenic bacteria, even under non-stressful laboratory conditions, can induce IID disease syndrome with various manifestations, including the development of wounds, abrasions, thallus bleaching, and fragmentation. The samples infected with the positive control C. solani strain-V2 exhibited the most severe bleaching at 80%, followed by V. brasiliensis strain-A8 at 60%, while V. brasiliensis strain-B2 and V, chemaguriensis strain-V1 both induced 50% thallus bleaching.
Sammendrag
Eucheumatoid seaweed farmers face a confluence of challenges emanating from presumed nutrient deficiency due to over-cropping, leading to low yields and frequent ice-ice disease outbreaks. Despite limited data on systemic nutrient limitations, some farmers clandestinely apply commercial inorganic fertilizers to accelerate growth and harvest premature crops after half of the prescribed 45-day cultivation period, sparking controversy. Unlike terrestrial agriculture, the use of inorganic fertilizers in eucheumatoid seaweed farming (ESF) is contentious. This stems from the haphazard use of the term “organic” to classify sea-grown crops without using synthetic fertilizers. However, when anthropogenic inorganic nutrient pollution fertilizes coastal seas, this effectively disqualifies these crops from the “organic” produce classification. This paper critically explores the use of artificial nutrient enrichment in ESF, assessing its impact on the crop's growth, ice-ice disease mitigation, carrageenan quality, and the marine environment. While controlled fundamental studies have shown that nutrient enrichment can significantly increase growth and potentially reduce disease occurrence, its inconsistent positive and negative effects on carrageenan yield and quality require further investigation with emphasis on organismal nutrient physiology and metabolism. Inorganic nutrient enrichment could also potentially alter the microbiome of eucheumatoid seaweeds. Whether inorganic nutrient enrichment in ESF will be sanctioned by the local and global regulators and policy makers, or not, increased knowledge is crucial for establishing basic science in order to rationally discuss challenges contributing to the decreasing production of quality raw, dried, eucheumatoid seaweed biomass for carrageenan processing, without compromising environmental and social responsibilities. Currently, the routine use of inorganic fertilizers in ESF is not authorized and remains a very sensitive issue, especially among marginalized subsistence seaweed farmers. In conclusion, inorganic nutrient enrichment in ESF presents a double-edged sword: whilst it can boost growth and potentially combat disease, its practice raises concerns on carrageenan yield and quality, and environmental pollution, as well as regulatory organic codes, necessitating further research for responsible implementation, when sanctioned. The bottom line is that when prescribed by regulators, the raw dried seaweed (RDS) and the subsequent products (both semi-refined and refined carrageenans) cannot be certified as “organic” when the crop is cultivated using inorganic fertilizers.
Sammendrag
Carrageenophytes such as Eucheuma and Kappaphycus play a vital role in supporting coastal economies and supplying the global hydrocolloid industry, with Indonesia producing over 75% of the world’s supply. However, the unregulated use of chemical liquid fertilisers (CLF) in seaweed farming poses serious ecological and socio-economic threats. In Sikka Regency, Indonesia, CLF use contributed to a decade-long collapse in cultivation, worsened by destructive fishing practices. Although efforts to revive farming began in 2018, current monitoring data are limited and fragmented. Nutrient over-enrichment from fertilisers has been linked to harmful algal blooms, epiphyte overgrowth, and diseases like ice-ice. While countries like the Philippines have introduced standards such as the GAqP for seaweeds, Indonesia still lacks formal regulation on fertiliser use. Misleading scientific claims and social media endorsements further promote detrimental practices. This article highlights the urgent need for public awareness, science-based guidelines, and coordinated policy to safeguard sustainable seaweed aquaculture. Extension services, farmer cooperatives, and social media can raise awareness, but added resources are required for guidelines, stronger policies, and market incentives discouraging CLF use.