RELATIONS OF THE N:P RATIOS TO PHYTOPLANKTON ABUNDANCES ON THE SHRIMP CULTURES (Panaeus vannamei) IN INTENSIVE PONDS

Ellis Mursitorini*
 
*Center of Fish Diseases and Enviromental Investigation
 Serang, Indonesia

In the water, the availability of nutrients is main factor to phytoplankton growth. The use of artificial feed on the intensive pond of shrimp cultures contributes to the high nutrient content so that the enrichment of waters tends to be very fast. The amount of N and P content can be determined by the type of phytoplankton in waters. The aim of this observation is to understand the relation of NP ratios to the phytoplankton abundances on the shrimp cultures lin intensive ponds. Therefore the growth of harmful phytoplankton for the shrimp culture can be prevented and avoided.

The observation was conducted in the pond area of Pontang (Serang District) and Mauk (Tangerang District) on September 2013 and in the pond area of Panimbang (Pandeglang District) on February 2015. The examination of samples were focused on chemical analysis to analyze nitrite, nitrate, ammonia, and phosphate by spectrophotometric method, while biological analysis to identify phytoplankton was performed by Sedgwick Rafter than observed with microscope (100x magnification).

The result of this observation showed that the NP ratios and phytoplankton abundance obtained were 37.28:1 and 31.90:1 and it was dominated by phytoplankton groups of Cyanophyta 96 % and 92 %, in the Panimbang pond, C2 and C4, respectively. Mauk ponds A5 had the NP ratios of 17.54:1, which was dominated by Chlorophyta group (almost 100 %) As for Pontang pond, A2 and A3 , had the NP ratios of 22.96:1 and 10.25:1, which was dominated by phytoplankton groups Chlorophyta and Dinoflagellata, respectively.

The conclusion from the observation described that the NP ratios at over 30:1 was dominated by Cyanophyta groups. Then the ratio 15-25:1 was dominated by Chlorophyta groups and the ratio which approached 10:1 was dominated by Dinoflagellata groups. By this observation for shrimp cultures (Panaeus vannamei) were recommended to maintenance of NP ratios in the pond waters in range between 15:1 to 25:1 because in this ratio phytoplankton from groups of Chlorophyta may growth good and stable.