Nitrogen and phosphorus dynamics in the biofloc production of the pacific white shrimp, Litopenaeus vannamei

Abstract

A study evaluating nitrogen and phosphorus dynamics was carried out using biofloc technology (BFT) systems employed to raise Litopenaeus vannamei juveniles. The study was carried out for 42 d in three fiberglass tanks with 210 L useful volume with no water exchange. Salinity, temperature, dissolved oxygen, pH, nutrients, suspended solids, and chlorophyll-a were monitored every 3 d. At the completion of the experiment, the shrimp had absorbed 39.1 and 35.0% of the total nitrogen (N) and phosphorus (P) inputs, respectively, while 39.0% of the N and 34.1% of the P remained in the system in dissolved forms. The dominant process of ammonium immobilization in the system was oxidation by nitrifying bacteria. On Day 42, the nitrate concentration represented more than 80% of the total dissolved inorganic nitrogen in all tanks. However, most of the dissolved nitrogen present in the tanks (80%) was organic. Phosphate and organic nitrogen and phosphorus continuously accumulated in the system throughout the experiment. The removal of these nutrients should be the focus of future studies because they may enhance the growth of harmful algae in tanks and in the water bodies that collect the post-crop wastewater.