Michael Roleda
Research Scientist
(+47) 405 57 498
michael.roleda@nibio.no
Place
Bodø
Visiting address
Torggården, Kudalsveien 6, NO-8027 Bodø
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 semi-refined and refined carrageenans) cannot be certified as “organic” when the crop is cultivated using inorganic fertilizers.
Authors
João Neiva Jorge Manuel Ferreira de Assis Eliza Fragkopoulou Gareth A. Pearson Peter T. Raimondi Laura Anderson Dorte Krause-Jensen Núria Marbà Andrew Want Olga Selivanova Masahiro Nakaoka W. Stewart Grant Brenda Konar Michael Roleda Mikael K. Sejr Cristina Paulino Ester A. SerrãoAbstract
Amphiboreal taxa are often composed of vicariant phylogroups and species complexes whose divergence and phylogeographic affinities reflect a shared history of chronic isolation and episodic trans-Arctic dispersal. Ecological filters and shifting selective pressures may also promote selective sweeps, niche shifts and ecological speciation during colonization, but these are seldom considered at biogeographical scales. Here we integrate genetic data and Ecologic Niche Models (ENMs) to investigate the historical biogeography and cohesion of the polymorphic rockweed Fucus distichus throughout its immense amphiboreal range, focusing on trans-Arctic asymmetries, glacial/interglacial dynamics, and integrity of sympatric eco-morphotypes. Populations were sampled throughout the Pacific and the Atlantic, from southern rear-edges to the high-Arctic. They were genotyped for seven microsatellites and an mtDNA spacer, and genetic diversity and structure were assessed from global to local scales. ENMs were used to compare niche divergence and magnitude of post-glacial range shifts in Pacific versus Atlantic sub-ranges. Haplotypic and genotypic data revealed distinct and seemingly isolated Pacific vs Arctic/Atlantic gene-pools, with finer-scale regional sub-structuring pervasive in the Pacific. MtDNA diversity was highly structured and overwhelmingly concentrated in the Pacific. Regionally, Alaska showed the highest intra-population diversity but the lowest levels of endemism. Some sympatric/parapatric ecotypes exhibited distinct genotypic/haplotypic compositions. Strikingly, niche models revealed higher Pacific tolerance to maximum temperatures and predicted a much more consolidated presence in the NE Atlantic. Glacial and modern ranges overlapped extensively in the Pacific, whereas the modern Atlantic range was largely glaciated or emerged during the Last Glacial Maximum. Higher genetic and ecogeographic diversity supports a primary Pacific diversification and secondary Atlantic colonization, also likely reflecting the much larger and more stable climatic refugia in the Pacific. The relic distribution and reduced ecological/morphological plasticity in the NE Atlantic are hypothesized to reflect functional trans-Arctic bottlenecks, recent colonization or competition with congeners. Within the Pacific, Alaska showed signatures of a post-glacial melting pot of eastern and southern populations. Genetic/ecotypic variation was generally not sufficiently discontinuous or consistent to justify recognizing multiple taxonomic entities, but support a separate species in the eastern Pacific, at the southern rear-edge. We predict that layered patterns of phylogeographic structure, incipient speciation and niche differences might be common among widespread low-dispersal amphiboreal taxa.
Abstract
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