PRELIMINARY STUDY ON LIMITING NUTRIENTS IN SEAWATER PONDS

A method for monitoring biological production of oxygen was used in the July 10-September 15, 1995 study on the limiting nutrients in eight land-based 5 m×5 m enclosures equipped with water stirrers in a seawater pond in the study region (Yellow Sea). Chicken manure only, chicken manure combined with chemical fertilizers, and chemical fertilizers only, were put into the enclosures, respectively. The results showed that phosphorus was the limiting nutrient; and that the optimal N:P ratio of the fertilizers was 7.25-7.54 (mean of 7.37), which was significantly lower than the ratio measured in the water, as phosphorus deposited is easily absorbed by sediments and is excessively uptaken by phytoplankton. The above optimal N:P ratio is suitable for daily fertilization with combination fertilizer in the seawater ponds.[PUBLICATION ABSTRACT]