A comparison of the bioremediation potential of five seaweed species in an integrated fish‐seaweed aquaculture system: implication for a multi‐species seaweed culture

Abstract

Abstract We investigated the growth and bioremediation potential of five local seaweed species ( Codium fragile , Ulva pertusa , Ecklonia stolonifera , Saccharina japonica and Gracilariopsis chorda ), using an integrated fish‐seaweed culture system as a biofilter for effluents from black rockfish ( Sebastes schlegelii ) tanks. The specific growth rate, biomass and net yield values of green algae were higher than those of brown algae. The tissue N and P levels of all species increased at the end of the experiment, but N:P ratios varied among seaweed species. The uptake rate and efficiency of total ammonia nitrogen uptake were the highest in U . pertusa and lowest in S . japonica . The phosphate uptake efficiency among all species ranged from 43% for S . japonica to 30% for G. chorda . These results suggest that all species can efficiently remove enriched nitrogen and phosphorus from fish tank effluents and are suitable for integrated aquaculture and bioremediation. However, inter‐specific differences were observed among seaweeds with regard to the biofiltration performance for different forms of nitrogen. The highest total oxidized nitrogen (ToxN) uptake efficiency was observed in E . stolonifera and S . japonica , while the lowest was observed in U . pertusa . ToxN uptake rates of E . stolonifera and S . japonica was 1.8 times higher than that of U . pertusa . Thus, a seaweed polyculture that included species with varying nitrogen source‐specific biofiltration activities might allow us to remove nutrients from effluents more effectively. These results provide valuable information regarding the selection of optimal seaweed species in fish‐seaweed integrated systems.