Applications of inorganic nutrient enrichment in eucheumatoid seaweed farming: A double-edged sword?

Abstract

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 semirefined and refined carrageenans) cannot be certified as "organic" when the crop is cultivated using inorganic fertilizers.