EFFECTS OF CLAY AND PHYTOPLANKTON TURBIDITY ON THERMAL STRATIFICATION IN SHALLOW AQUACULTURE PONDS

Hisham A. Abdelrahman* and Claude E. Boyd
 The School of Fisheries, Aquaculture and Aquatic Sciences
 Auburn University
 Auburn, Alabama 36849-5419 USA
 hisham@auburn.edu

Water temperature is a vital factor controlling the growth rate of all cultured aquatic species. Shallow water aquaculture ponds typically stratify thermally in the day and destratify at night. The severity of thermal stratification in the pond is controlled by the degree of light penetration. The depth of penetration of solar radiation into a small pond is greatly controlled by water turbidity which either caused by suspended clay particles or phytoplankton abundance. This study was conducted to determine the effect of different causes and levels of water turbidity on water temperature profiles in shallow aquaculture ponds.

The experiment was performed at the Auburn University E. W. Shell Fisheries Center Auburn, AL. The study was conducted in two phases. Three, 0.04-ha research earthen ponds with the same dimensions were selected and dedicated for each phase. During the first phase, one pond had clear water, while the second one was treated with fertilizer to maintain phytoplankton turbidity. Kaolin clay added to a third pond to develop turbidity. During the second phase, each pond had a different level of clay turbidity.

In each pond, light intensity and water temperature at the surface, and at 20-cm depth intervals within the water column were monitored at 0.5-h intervals with a Model 64K HOBO Pendant® Temperature/Light Data Logger. Air temperature under shade and in full sunlight also were monitored at 0.5-h intervals. Water turbidity and Secchi disk visibility were measured daily in each pond. Results showed that turbid ponds thermally stratified more strongly than did the clear pond.