TY - JOUR AU - De Silva, H. C. C. AU - Maithreepala, R. A. AU - Asanthi, H. B. AU - Priyadarshana, T. PY - 2016/08/15 Y2 - 2024/03/29 TI - Spatial and Temporal Variation of Physico-chemical Parameters and Primary Productivity in Muruthawela Reservoir, Sri Lanka JF - Asian Journal of Agriculture and Food Sciences JA - AJAFS VL - 4 IS - 4 SE - Articles DO - UR - https://ajouronline.com/index.php/AJAFS/article/view/4001 SP - AB - <p>Variation of primary productivity in Muruthawela reservoir, a tropical deeper reservoir in lowland of Southern Sri Lanka was determined along the water column in three representative locations throughout one year period. The obtained results were interpreted in relation to the selected environmental conditions including, water depth, secchi depth, water temperature, pH, conductivity, salinity, dissolved oxygen, chlorophyll-a, nitrate and phosphate concentrations. Although, mean water depthwas ranged from 7.16-23.58m during the study period, the secchi depth and euphotic depth were determined as 2m and 4m respectively.The average value of primary productivity were in the ascending order of bottom&lt;surface&lt;middle with 65% of themaximum surface photo-inhibition in December 2012.There were no significant differences (p &gt; 0.05) of physico-chemical parametersof each position (surface, middle, aphotic zone) among the three sites.However, significant Pearson correlations were observed between chlorophyll-a, nitrate and phosphate concentrations and conductivity in the reservoir. The maximum mean Gross primary productivity (1.512±0.004mgCL<sup>-1</sup>h<sup>-1</sup>) was recorded in December, 2012 along with the maximum nitrate (0.161mg/L) and phosphate(0.145mg/L) concentrations. The mean Gross Primary Production (GPP) values showed a significant positive correlations between nitrate concentration (R = 0.84; p &lt;0.01), phosphate concentration (R= 0.87; p&lt; 0.01), chlorophyll-a concentration (R= 0.93; p&lt; 0.01) and Secchi depth (R= 0.75; p&lt; 0.01) and it was negativelycorrelated (R=-0.80; p &lt;0.01) with conductivity. The year round variation of primary productivity coincided with the general rainfall pattern which can be caused nutrient runoff from the cultivated catchment in to the reservoir.  Further, the progression of trophic state in Muruthawela reservoir has been occurred from Mesotrophic to Eutrophic state as a gradual process. This conversion from one stage to another has been mainly based on the degree of nutrient inflow which triggers by the seasonal variation of rainfall in the study area and ultimately primary productivity of the reservoir.</p><p> </p> ER -