Giant kelp (Macrocystis pyrifera) is a vital primary producer in marine ecosystems due to its high net primary production (NPP) and carbon sequestration potential. This study investigated the NPP and carbon dynamics of farmed giant kelp at a farm site in Shearwater Bay, Lüderitz, Namibia, from May 2023 to April 2024. The study assessed giant kelp biomass, canopy area, seawater temperature, nitrate concentrations, dissolved organic carbon levels and carbon sources at the farm. The farmed kelp exhibited a total NPP of 7.570 kg C·m⁻²·year⁻¹, with a peak NPP of 0.855 kg C·m⁻² in June 2023 (winter), and reached a low of 0.342 kg C⋅m⁻² in August 2023 (winter), where it averaged 0.635 kg C·m⁻²·month⁻¹ with greater variability than in summer, where it averaged 0.627 kg C·m⁻²·month⁻¹. Correlation analyses showed no significant relationship between canopy area and NPP. Kelp biomass exhibited a weak positive correlation with NPP, but this association was not statistically significant. Temperature was also weakly positively correlated with NPP, while nitrate concentrations showed a moderate positive correlation with NPP at the farm. The DOC concentrations ranged from 2.94 to 5.12 ppm, with no significant depth variation. Isotopic analysis showed distinct carbon 13 isotopic signatures (δ¹³C) for seawater DOC (-26.63‰ to -14.61‰) and for the giant kelp (-13.69‰ to -12.32‰), indicating mixed sources like terrestrial inputs, in situ production, shifts and c. The study findings showed that nutrient availability was a key driver of NPP at the giant kelp farm, with implications for optimizing kelp farming management and assessing the impacts of kelp farming in coastal areas. The study supports the development of non-destructive monitoring indicators and calls for further research into nutrient cycling, carbon cycling, ecosystem productivity and blue carbon strategies associated with kelp farming to inform sustainable coastal ecosystem management.
Mateus et al. (Mon,) studied this question.