Halophytes for the treatment of saline aquaculture effluent

We determined the feasibility of using salt-tolerant plants (halophytes) as biofilters to remove nutrients from saline aquaculture wastewater. Suaeda esteroa, Salicornia bigelovii and Atriplex barclayana (Chenopodiaceae), species with potential as forage and oil seed crops, were grown in sand in draining containers (lysimeters) in a greenhouse experiment. They were irrigated to meet evapotranspiration demand and to produce a 0.3 leaching fraction, using aquaculture effluent generated from an intensive tilapia culture system. The effluent salinity was increased with NaCl to make salinity treatments of 0.5, 10 and 35 ppt. The plant-soil system removed 98% and 94% of the applied total and inorganic nitrogen, respectively. It removed 99% and 97% of the applied total and soluble reactive phosphorus, respectively. High removal rates occurred despite the high leaching Fraction. Salt inhibited (P < 0.05) the growth rate, nutrient removal, and volume of water that all three plant species could process. Suaeda and Salicornia, which are succulent salt marsh species, performed better than the desert saltbush, Atriplex, at the higher salinities. (C) 1999 Elsevier Science B.V. All rights reserved.