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The Role of Phosphorus on the Primary Productivity in Ponds

S. Pavel
Department of Zoology, Jahangirnagar University, Savar, Dhaka

M. R. Nabi
Department of Zoology, Jahangirnagar University, Savar, Dhaka

Abstract/ Executive Summary:

Role of phosphorus on primary productivity in four ponds was studied for a period of one year, from January, 1996 to December, 1996. The concentrations of available phosphorus were found to vary from 0.0105 to 0.1838 ppm and 0.40 to 20.20 ppm in water and bottom soil samples, respectively. The net primary productivity varied from -0.45 to 16.38 gO₂m-²d^-1 and gross primary productivity varied from 1.48 to 26.2 gO₂m-²d^-1. Available prosphorus levels in soil showed a direct relationship with available phosphorus levels in water and differed significantly among the four ponds. Strong negative correlation observed between phosphorus concentrations and productivity of the ponds. On the basis of primary productivity status, the ponds may be characterized as mesotrophic ponds.

Keywords: Phosphorus, Pond, Primary productivity

Location: Jahangirnagar University, Savar, Dhaka

Start Date: 00-01-1996

End Date: 00-12-1996

Program Area: Crop-Soil-Water Management

Commodity: Fertilizer

Objectives:

To determine the primary productivity of four ponds and its relation with phosphorus levels in water and soil.

Methodology:

Four ponds were selected for this research work, two of them situated in the campus of Jahanginagar University, Savar, Dhaka. The third one situated at Ghior, Manikgonj and the fourth one in Dhaka Metropolis adjacent to Dhaka Old Airport Runway (National Square). For the convenience of the study the first three ponds were selected as treatment pond, and the last one as control pond. The ponds were designated as Site-I-A, Site-I-B, Site-II and Site-III, respectively. The general characteristics of these ponds are given in this study. The present investigation was conducted for a period of one year i.e., from January '96 to December '96. For the determination of phosphorus, water and bottom soil samples of all selected ponds were collected by "Kemmerer water sampler" and "Ekman dredge" respectively. Available phosphorus levels of both in water and bottom soil samples were determined by "Ascorbic acid blue colorimetric method" and the measurement of the absorbance was done by "Chimeta visible spectrophotometer" at a wave length of 882nm. The value of available phosphorus (H₂PO₄, HPO₄= and PO₄) ions was converted to orthophosphate (P₂O₅) by multiplying the conversion factor 2.2915. That is, avail-Px2.2915= P₂O₅_.Both the values were expressed. Primary productivity measurements were done at a monthly interval by the classical "light and dark bottle" method. Concentration of dissolved oxygen in bottle's water was determined by modified Azide-Winkler method. The light index was calculated by combining the effects of the ratio of euphotic depth to mixing depth with the effect of daylength (Ll= 2Z_sD/24 Z^m) {Iwhere, Z_s is the Secchi depth (m), 2Z_s is a rough estimate of the euphotic depth, Zm is mixing depth (m), and D is daylength (h)}. Again, the daily productivity values were extrapolated by multiplying the value obtained for the 6 hour incubation period (i.e., P_T= L_T/L₁X P₁ (where, P_T is total photosynthesis, L_T is total light intensity, L_l is the light intensity during the incubation period). Oxygen data were convened to carbon by multiplying with 0.375 (PQ= 1.00; Mol Q₂ released/mol CO₂ assimilated; APHA, 1985. The equivalent organic matter and plankton biomass were estimated.

Source of Information: Bangladesh Journal of Life Science, June 1997, Vol.9(2), pp:47-58, ISSN:1023-0858.

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Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Available prosphorus levels in soil showed a direct relationship with available phosphorus levels in water and differed significantly among the four ponds in the study. Strong negative correlation observed between phosphorus concentrations and productivity of the ponds. On the basis of primary productivity status, the ponds may be characterized as mesotrophic ponds. It can be said that the phosphorus itself and with other myriad factors influence the primary productivity of a pond.

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