New species for the biomitigation of a super-intensive marine fish farm effluent: Combined use of polychaete-assisted sand filters and halophyte aquaponics

The main objective of this study was to test an innovative biomitigation approach, where polychaete-assisted (Hediste diversicolor) sand filters were combined with the production of Halimione portulacoides in aquaponics, to remediate an organic-rich effluent generated by a super intensive fish farm operating a land-based RAS (Recirculating aquaculture system). The set up included four different experimental combinations that were periodically monitored for 5 months. After this period, polychaete-assisted sand filters reduced in 70% the percentage of OM and the average densities increased from approximate to 400 ind.m(-2) to 7000 ind.m(-2). H. portulacoides in aquaponics contributed to an average DIN (Dissolved inorganic Nitrogen) decrease of 65%, which increased to 67% when preceded by filter tanks stocked with polychaetes. From May until October (5 months) halophytes biomass increased from 1.4 kg m(-2) +/- 0.7 (initial wet weight) to 18.6 kg m(-2) +/- 4.0. Bearing in mind that the uptake of carbon is mostly via photosynthesis and not though the uptake of dissolved inorganic carbon, this represents an approximate incorporation of approximate to 1.3 kg m(-2) carbon (C), approximate to 15 g m(-2) nitrogen (N) and approximate to 8 g m(-2) phosphorus (P) in the aerial part (76% of total biomass), and an approximate incorporation of approximate to 0.5 kg m(-2) carbon (C), approximate to 3 g m(-2) nitrogen (N) and approximate to 2 g m(-2) phosphorus (P) in the roots (24% of total biomass). In the present study, the potential of the two extractive species for biomitigation of a super-intensive marine fish farm effluent could be clearly demonstrated, contributing in this way to potentiate the implementation of more sustainable practices. (C) 2017 Elsevier B.V. All rights reserved.