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Planktonic Primary Productivity of a Eutrophic Water Body of Dhaka Metropolis, Bangladesh

MD. SHAFIQUL ISLAM
Graduate School of Science, Kobe University, Japan

MD. ALMUJADDADE ALFASANE
Department of Botany, University of Dhaka, Dhaka

MONIRUZZAMAN KHONDKER
Department of Botany, University of Dhaka, Dhaka

Abstract/ Executive Summary:

Dynamics of phytoplankton primary productivity were determined in a eutrophic water body of Dhaka Metropolis fortnightly for one year. The mean value of daily rate of primary productivity was 10.05 gC/m2/d and annual sum of primary productivity was estimated 3669.5 gC/m2/y. The yearly mean value of conductivity, pH, alkalinity, SRP and SRS were 486.66 μS/cm, 7.21, 4.02 meq/l, 0.75 mg/l and 49.75 mg/l, respectively which indicated the intensity of contamination from the catchment. Significant correlations were obtained among the variables (day length, irradiance, water temperature and DO) relating to primary productivity. “Green soup” like algal bloom was found to occur on most occasions. The productivity was confined to the upper few centimeter depth of the water indicating a typical eutrophic nature of the water body.

Keywords: Phytoplankton, Primary productivity, Eutrophication, Assimilation numbers, Water quality

Location:

Start Date:

End Date:

Program Area: Resource Development and Management

Commodity: Plankton

Objectives:

The present paper deals with the dynamics and status of planktonic primary productivity of the same water body.

Methodology:

Present investigation was carried out in Mirpur Jheel which is subjected to a dense human settlement in its catchment. The location map and morphometirc feature of the Jheel have been presented by Khondker et al. (2011). Samples were collected at 15 days interval from August 19, 1993 to July 14, 1994 (except in August 1993 and July 1994, when a single sample was collected in each month). A Schindler sampler of 5 liter capacity was used to collect samples from 0.5 m depth. The samples were covered with black cloth to avoid light shock to the phytoplankton. Eight triplicate clear borosilicate BOD bottles (120 ml, Jena Schott, Germany) were filled and kept in a light proof wooden box. Duplicate bottles were vertically suspended along a rope at a desired depth of incubation. Two dark bottles were incubated at the bottom of the rope. Third bottle was used for the determination of initial oxygen concentration. Processing took ca. 40 minutes; incubation time was two hours, usually between 10:00 and 12:00 a.m. After incubation, samples were fixed immediately by adding 1 ml manganous sulfate and 1 ml Winklers reagent and kept immersed under water in a container until further analysis. Rest of the collected 5 litre sample was transported to the Hydrobiology and Limnology Laboratory, Department of Botany, University of Dhaka and was analyzed for eight other limnological parameters (Afroze and Khondker 1995). In situ measurement of Secchi depth, photosynthetically active radiation and water temperature were also carried out (Afroze and Khondker 1995, Khondker and Kabir 1995). All the other measurements related to the components of the productivity and day length were made following the methods described in Khondker and Parveen (1993) and Khondker and Kabir (1995). There are altogether 22 measurements during the period of investigation for all the variables.

Source of Information: Bangladesh J. Bot. 41(2): 135-142, 2012

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The present water body is strongly influenced by direct input of waste water and organic matter discharged from the nearby huts, sewerages and garbages from the residential colonies and markets. The yearly mean values of conductivity, pH, alkalinity, SRP and SRS were 486.66 μS/cm, 7.21, 4.02 meq/l, 0.75 mg/l and 49.75 mg/l, respectively. These values indicated the intensity of contamination from the catchment. As a whole, the present aquatic system having an average SRP > 600 μg/l, the algal zone becomes restricted only in the upper meter, productivity proliferates just at 10 cm depth, allows trophogenic zone to be confined only upper few centimeter, poor DO as well as anoxic bottom, swift light attenuation caused by high biomass deprived the possibility to improve underwater light climate reveals sufficient prove to label this aquatic ecosystem an eutrophic one. Day length, irradiance, water temperature and DO showed positive significant correlations with primary productivity. “Green soup” like algal bloom was found to occur most occasions. The productivity was confined to the upper few centimeter depth of the water indicating a typical eutrophic nature of the water body.

Knowledge Management: Journal