Harsh Lotiya Jan/ 26/ 2026 | 0
The 7th Leibniz-ZMT Annual Conference (ZAC7), hosted by the Leibniz Centre for Tropical Marine Research (ZMT), took place on January 26–27, 2026 in Germany. This conference focuses on tropical marine ecosystem research, featuring sessions organized by world regions, including topics on climate change impacts, mangrove crabs, and seagrass.
Aaron Cordes, a German national who recently completed his master’s degree at the University of the Algarve, Portugal, presented the findings of his work (abstract below) with nama sea grapes in Fiji, at the ZAC7 conference. Aaron was hosted by Matanataki in Fiji in 2025, and his work provided insights to portfolio company Project Qari, a community and cooperatively owned mariculture company.
A summary of the findings, “Production of nama seaweed (Caulerpa spp.) in an experimental lagoon cultivation setting and land-based system – Influence of cultivation depth and nutrient load on growth and morphology” by Cordes et al. can be downloaded here.
Abstract:
With increasing impacts of climate change and declining fishery yields, interest in seaweed aquaculture is growing in Fiji. Species of the genus Caulerpa are particularly promising due to their high market value. In Fiji, these edible seaweeds, locally known as nama, are traditionally harvested from shallow lagoons and reef flats. Rising demand has increased pressure on natural stocks, highlighting the need for sustainable cultivation alternatives. This study evaluated two cultivation approaches for nama: a lagoon-based system using submerged trays deployed at four depths (D1-D4), and a land-based tank system with nutrient enriched trays (TN) and a control treatment (TC) using natural seawater. Because nama growth and morphology are highly sensitive to environmental conditions, the aim was to identify cultivation settings that maximize growth while maintaining desirable quality traits. In Fiji, key quality parameters are frond thickness, ramuli density, and frond coloration. Over four weeks, relative growth rate (RGR), frond thickness, ramuli density, and frond coloration were monitored. In the lagoon experiment, RGR was highest in shallow treatments, reaching 2.16±0.58% day⁻¹, but declined to negative values after week two across all depths, accompanied by biomass disintegration and bleaching. In the land-based experiment, RGR was similar between TN and TC during the first week. In week two, RGR in TC became negative and biomass disintegrated, while TN reached a maximum RGR of 2.03± 0.01% day⁻¹. Despite improved coloration, nutrient enrichment resulted in very thin fronds with low ramuli density and reduced frond production. These findings indicate that nutrient limitation is a major constraint for tray cultivation in lagoon waters and unenriched land-based systems, likely due to the lack of sediment-derived nutrients. Although nutrient enrichment enhanced growth, it also caused unfavorable morphological changes, reducing overall biomass quality. Future research should focus on the identification of the exact nama species and optimization of fertilizer requirements and composition, potentially targeting a co-cultivation approach of nama seaweeds with marine animals.