DTD 5 Analysis of nutrient flows in integrated intensive aquaculture systems O. Schneider * , V. Sereti, E.H. Eding, J.A.J. Verreth Wageningen University, Department of Animal Sciences, Fish Culture and Fisheries, P.O. Box 338, 6700 AH Wageningen, The Netherlands Received 14 September 2004; accepted 14 September 2004 Abstract This paper analyses nutrient conversions, which are taking place in integrated intensive aqua- culture systems. In these systems fish is cultured next to other organisms, which are converting otherwise discharged nutrients into valuable products. These conversions are analyzed based on nitrogen and phosphorous balances using a mass balance approach. The analytical concept of this review comprises a hypothetical system design with five modules: (1) the conversion of feed nutrients into fish biomass, the ‘‘Fish-Biomass-Converter’’; (2) the separation of solid and dissolved fish waste/ nutrients; the ‘‘Fish-Waste-Processor’’; (3) the conversion of dissolved fish waste/nutrients, the ‘‘Phototrophic-herbivore-Converter’’; (4 and 5) the conversion of solid fish waste, the ‘‘Bacterial- Waste-Converter’’, or the ‘‘Detrivorous-Converter’’. In the reviewed examples, fish culture alone retains 20–50% feed nitrogen (N) and 15–65% feed phosphorous (P). The combination of fish culture with phototrophic conversion increases nutrient retention of feed N by 15–50% and feed P by up to 53%. If in addition herbivore consumption is included, nutrient retention decreases by 60–85% feed N and 50–90% feed P. This is according to the general observation of nutrient losses from one trophic level to the next. The conversion of nutrients into bacteria and detrivorous worm biomass contributes only in smaller margins (e.g. 7% feed N and 6% feed P and 0.06% feed N 0.03 Â 10 À3 % feed P, respectively). All integrated modules have their specific limitations, which are related to uptake kinetics, nutrient preference, unwanted conversion processes and abiotic factors. # 2004 Elsevier B.V. All rights reserved. Keywords: Recirculating aquaculture systems; Nutrient; Conversion; Retention; Algae; Bacteria; Abalone; Finfish; Integrated aquaculture www.elsevier.com/locate/aqua-online Aquacultural Engineering xxx (2004) xxx–xxx * Corresponding author. Tel.: +31 317 485147; fax: +31 317 483937. E-mail address: oliver.schneider@wur.nl, (O.Schneider)*. 0144-8609/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaeng.2004.09.001