The potential for large-scale kelp aquaculture to counteract marine eutrophication by nutrient removal

Large-scale kelp aquaculture offers several opportunities to counteract eutrophication. Here, six sites from Ailian Bay to its offshore waters in Rongcheng, northern China, were selected to investigate the spatiotemporal variations of kelp (Saccharina japonica) and seawater concentrations of C, N, and P in 2017 and 2019 in order to assess nutrient removal by kelp farming. Variations in biological parameters and elemental nutrient concentrations of whole thalli were also quantified in 2015 and 2016. We found that kelp farming in Ailian Bay can remove 1309 tons of C, 104 tons of N, and 12 tons of P. The increase of total suspended matter and nutrient concentrations from the coast to offshore waters supports the hypothesis of nutrient removal by farmed kelp. This study provides evidence of the bioremediation potential of farmed kelp. [Display omitted] •The potential of large-scale kelp farming to counteract eutrophication were evaluated.•The spatially decreasing of nutrient concentrations proves nutrient removal by kelp.•The carbon uptake by the farmed kelp does not vary between year or site in Alian Bay.•N limitation at the farmed site closest to the shore, with low exchange of seawater.•Large-scale kelp farming has a great potential for C, N and P removal.