Algae. 2011; 26(1): 97-108.

Biofiltration efficiency and biochemical composition of three seaweed species cultivated in a fish-seaweed integrated culture

Yun Hee Kang¹, Sang Rul Park² and Ik Kyo Chung^3,*

¹Marine Research Institute, Pusan National University, Busan 609-735, Korea
²University of Texas at Austin Marine Science Institute, Port Aransas, TX 78373, USA ³Division of Earth Environmental System, Pusan National University, Busan 609-735, Korea

We evaluated the potential of three seaweed species (Ulva pertusa, Saccharina japonica, Gracilariopsis chorda) as biofilters for effluents from black rockfish (Sebastes schlegeli) tanks. The experiments consisted of a fish monoculture system and a fish-seaweed integrated system under identical physical conditions. All species efficiently removed NH4+, NO3? + NO2?, and PO43? from the fish tank effluents. Of the three species evaluated, U. pertusa showed the highest biofiltering efficiency for NH4+ (>80%). In contrast to U. pertusa and G. chorda, S. japonica showed a relatively higher preference for NO3? + NO2? than for NH4+. These results suggest that seaweeds may select nitrogen sources fitting their storage capacity. Therefore, standard fish farm effluents should establish a total nitrogen concentration that includes both NO3? and NH4+, and the selection of a biofilter seaweed species should be made with consideration of the N forms expelled in effluent. The biofiltering efficiency for PO43? was highest in G. chorda (38.1%) and lowest in S. japonica (20.2%). In all species, tissue N and P contents rapidly increased over the initial values. The data for tissue N and P contents, and C : N and N : P ratios, indicate that neither N nor P was limiting. This suggests that the three species serve as biofilters by storing large amounts of nutrients. These results provide valuable information for selecting optimal seaweed species in fishseaweed integrated systems and allow land-based integrated aquaculture system operators to understand the behavior of integrated cultures sufficiently for the results herein to be extrapolated to larger-scale cultures.

Keywords : biofiltration; land-based aquaculture system; nitrogen; seaweed; tissue nutrient