Bahasa Inggris Jurusan

EMPIRICAL MODELING OF APHYTOPLANKTON GROWTH AND OXYGEN PRODUCTION IN AQUACULTURE

Claude E. Boyd

·      Phytoplankton growth in aquaculture ponds is regulated in freshwater primarily by phosphorus concentration, but in brakishwater both nitrogen and phosphorus concentrations often limit abundance of phytoplankton. Abudance of phytoplankton and production of aquacultural species can be enhanced by fertilization or manuring. Even greater production of aquacultural species can be achieved through feed applications.  Phytoplankton abundance in ponds with feeding increases as feeding rates are raised. Dissolved oxygen (DO) dynamics in ponds are regulated primarily by phytoplankton abundance. As phytoplankton density increases, a pronounced vertical stratification of DO concentration develops and DO exhibits a strong daily cycle with the highest concentration in the afternoon and the lowest concentration around dawn.

·      Problem with low DO during the night increase in frequency and severity as feeding rates are elevated. Cloudy weather and phytoplankton die-offs also may cause DO depletion in ponds. Computer simulation techniques for predicting DO concentrations in ponds are available, but these methods require data that often are not easily available to pond managers. A simple projection technique for extrapolating DO concentrations measured early in the night to provide a forecast of DO concentration later in the night is popular with pond managers. Aeration is the only reliable means of combating DO depletion.