Algal bioremediation of eutrophic effluents in small scale integrated aquaculture systems

Non-point source eutrophication of coastal waters is a significant problem that may be exacerbated locally by effluent from aquaculture operations. Porphyra spp. grow and assimilate nutrients rapidly, making them good candidates for eutrophication abatement via systems of integrated aquaculture. I summarize our work examining the bioremediatory performance (growth rate, nutrient assimilation, tissue N and pigment content) of four U.S. and three Asian Porphyra species as functions of N concentration and source (nitrate vs. ammonium). The Northeast U.S. species P. amplissima is the best performing local bioremediator (maximum growth rate and tissue N=24% d-1, 5.2% DW, respectively), comparing well with P. yezoensis, an economically important species in Asia. When tissue remained non-reproductive, P. amplissima growing in 300 mu M ammonium removed 99-100% of N but only about 50% of P (fed 10:1 molar N:P ratio). We have begun investigating the relationship between stocking density and yield, and will begin demonstration scale tests of the mesoscale system.