| Nutrient salts and phytoplankton levels in 9 aquiculture ponds planted with 3 differentmangrove tree species (Sonneratia caseolaris, Kandelia candel and Ageiceras comiculatum)in 3 area-ratios (15%, 30% and 45% respectively) were monitored over a 2-month waterexchange cycle period in Shenzhen, Guangdong province in 2002~2003. A separatedaquiculture pond without trees was used as a control. Nutrient salts and phytoplankton in theexperimental ponds were also monitored over an aquiculture cycle in 2004.Results showed that phytoplankton community is very unstable. Phytoplankton densityand concentrations of Chl.a were large and fluctuated drastically in all ponds and no patterncould be discerned. Experimental ponds could effectively reduce nutrient concentrations.The concentrations of DIN in experimental ponds decreased distinctly in 2 weeks. And theconcentrations of PO4 -P in experimental ponds maintained while it increased drastically in 3-the control one. Results indicated that the purification efficiency varied according todifferent mangrove species and different development phases. The experimental ponds hadsimilar purification efficiency during mangrove trees'yound sprout period, but it wasdifferent during those trees'biennial period. Results showed that ponds planting withAgeiceras comiculatum were most efficient in reducing both N and P concentrations. Theresults also showed that ponds planted with a 15% area ratio of mangrove trees had similarlevels of purification as higher area ratios. With obvious benefits, therefore, the planting arearatio of 15% was recommended.The relations between nutrient salts and phytoplankton were also analyzed in this... |
