Multivariate statistical analysis of chlorophyll-a and water quality parameters in ponds of Litopenaeus vannamei culturing

Water quality parameters in 22 ponds of a Litopenaeus vannamei culture farm in Fengxian District of Shanghai were investigated from April to September in 2009.Fifteen parameters including chlorophyll-a(Chl.a) ,temperature,pH,dissolved oxygen (DO) ,transparency,suspended substance (SS) ,total organic carbon (TOC) ,biological oxygen demand(BOD5) ,chemical oxygen demand(CODMn) ,nitrite nitrogen(NO2-N) ,nitrate nitrogen(NO 3-N) ,ammonia nitrogen(NH3-N) ,total nitrogen(TN) ,active phosphorus(PO43--P) and total phosphorus(TP) were determined.Descriptive statistics was conducted and the correlation between Chl.a and other parameters was analyzed.The statistical analysis results showed that Chl.a had extremely significantly linear positive correlation with SS,TOC,BOD5,CODMn,TN and TP.Significantly linear positive correlation existed between Chl.a and DO.Extremely significantly linear negative correlation was confirmed between Chl.a and transparency while Chl.a had significantly linear negative correlation with PO34--P.Chl.a had no significant correlation with water temperature,pH,NO 2-N,NO 3-N and NH3-N.According to the principles of selecting independent variables in the multiple linear regression analysis,four water quality parameters including TOC,TN,PO34--P and TP were used for establishing the stepwise regression model which was Chl.a =-0.054 5 + 0.003 49 TOC + 0.015 3 TN-0.418 PO43--P + 0.276 TP(r = 0.715 5) .The effects of these four factors on Chl.a were tested using the partial regression coefficient.The most influential water quality parameter on Chl.a were TP and then TOC,PO34--P,TN in turn.The results would help further study on ecological rules and water environmental protection in aquaculture ponds.