Assessment of water quality of intensive ponds in the Pearl River Delta region

Pond-farming is the main form of fisheries production in the Pearl River Delta region. We monitored the water quality in intensive ponds of Ctenopharyngodon idellus, Oxyeleotris marmoratus, Micropterus salmoides and Channa argus in the Pearl River Delta region during May, to December of 2012. Ten parameters including pH, dissolved oxygen(DO), non-ionic ammonia(NH3), ammonia nitrogen(NH4+-N), nitrate nitrogen(NO3--N), nitrite nitrogen(NO2--N), total nitrogen(TN), total phosphorus(TP), potassium permanganate index(CODMn) and transparency were assessed by single pollution index and duty ratio. The water quality was assessed by comprehensive pollution index. The resultsreveal that high nutrient loadings were the prominent problems, and NH3,NO3--N,NO2--N, TN and TP were the main pollutants in intensive ponds. The main pollutants in C.idellus pond were NH3 and TN (pollution load: 37.58%). The main pollutants in O.marmoratus pond were NH3, TN andNO3--N (pollution load: 59.37%). The main pollutants in M.salmoides pond were NH3, TN andNO3--N andNO2--N (pollution load: 66.80%). The main pollutants in C.argus pond were TN,NO3--N, TP and NH3 (pollution load: 59.43%). The research on CODMn reveal that there was a large amount of reducible organic matters in these ponds. The pond water was heavily polluted, and the degree of contamination exceeded the alert level based on comprehensive pollution index.