SEAWEED BIOFILTERS AS REGULATORS OF WATER-QUALITY IN INTEGRATED FISH-SEAWEED CULTURE UNITS

The water-quality characteristics of a new system for the integrated c ulture of fish (Sparus aurata L.) and seaweed (Ulva lactuca L.) were e xamined, Seawater was recirculated between intensive fishponds and sea weed ponds, The seaweed removed most of the ammonia excreted by the fi sh and oxygenated the water. A model consisting of several tanks and a pilot consisting of two 100-m(3), 100-m(2) ponds were studied, In bot h, the metabolically dependent water-quality parameters (dissolved oxy gen, NH4+-N, oxidized-N, pH and phosphate) remained stable and within safe limits for the fish during over 2 years of operation, The design allowed significant increases in overall water residence time (4.9 day s), compared with conventional intensive ponds, and produced a high yi eld of seaweed in addition to the fish, The design provides a practica l solution to major management and environmental problems of land-base d mariculture.