Affiliations: Department of Earth and Atmospheric Sciences, 1-26
Earth Sciences Building, University of Alberta, Edmonton, Alberta T6G 2E3,
Canada | Institute of Marine Sciences, University of
Chittagong, Chittagong 4331, Bangladesh
Abstract: Nutrient loadings were measured for surface seawater and bottom
sediments of semi-intensive and improved extensive shrimp culture pond,
adjacent estuary, and fallow land in the south-east coastal region of
Bangladesh during August, 2000 – January, 2001 to evaluate the impact of
shrimp culture. The mean levels of nutrients found in the pond surface water
were 108.780 mg/L for CaCO_3, 0.526 mg/L for
NH<FORMULA>_4^+-N, 3.075 wt% for organic carbon, 7.00 mg/L for
PO_4-P, 5.57 mg/L for NO_3-N, and 7.33
mg/L for chlorophyll-a. The maximum mean value of H_2S
(0.232 mg/L) was found in estuarine water. Nutrients loading were found to be
decreased with distance from the shrimp farm discharge unit in estuarine water.
The mean level of organic matter, total nitrogen, and organic carbon were found
in higher concentrations in sediments of cultured pond compared to bottom soil
of adjacent fallow land at the same elevation. Extractable Ca values were found
in higher concentration (550.33 ppt) in adjacent fallow land, as; the shrimps
for molting in shrimp ponds use extractable Ca. The relation between seawater
H_2S value and sediment pH (r = -0.94); sediment organic
carbon and sediment pH values (r = -0.76), sediment total nitrogen and sediment
pH (r = -0.74) were found to be highly negatively correlated. Whereas the
relation between seawater H_2S value and sediment total
nitrogen (r = 0.92), water NH_4^+-N and sediment pH (r =
0.66) were found to be positively correlated. The results revealed that load of
nutrients at eutrophic level in estuarine water, and decrease of soil pH;
leading to acid sulphate soil formation indicates a negative impact of shrimp
culture.
