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Vertical Distribution of Phytoplankton in a Hypertrophic Jheel, Mirpur, Dhaka

Moniruzzaman Khondker
Department of Botany, University of Dhaka, Dhaka?1000, Bangladesh

Md Shafiqul Islam
Ansar Academy, Shafipur, Gazipur, Bangladesh

Humayra Afroze
Scott & White Memorial Hospital, 702 SW HK Dodgen Loop, Medical Research Building, West Loading Dock, Temple, TX, 76508, USA

Abstract/ Executive Summary:

Four species of phytoplankton namely, Arthrospira platensis, Phacus ranula, Oscillatoria chalybea, and Euglena variabilis showed vertical depth distribution in different seasons. A. platensis and O. chalybea were found to co-exist and showed almost identical seasonal depth distribution pattern. P. ranula preferred to grow in the illuminated upper zone of the water body while E. variabilis showed moderate growth also at the bottom where the concentration of soluble reactive phosphorus was very high (506 - 1554 μg/l). A. platensis and O. chalybea grew luxuriantly in summer and monsoon seasons while P. ranula and E. variabilis were abundant in winter.

Keywords: Vertical distribution; Phytoplankton; Hypertrophic Jheel

Location: The water body is located at the Section 7, Mirpur, Dhaka

Start Date:

End Date:

Program Area: Resource Development and Management

Non-commodity: Plankton

Objectives:

To find the vertical periodicity of some dominant phytoplankton in a Jheel (large pond).

Methodology:

The water body is located at the Section 7, Mirpur, Dhaka having an area of 3 ha and a maximum water depth of 4.69 m. It is perennial and L-shaped. Water samples for the determination of limnological water quality and plankton analyses were collected from 0.5, 2.0 m and from the bottom (varied between 3.2 and 4.69 m) with the help of a Schindler’s Sampler (5 L cap.). Details of the methodology regarding the other limnological factors were furnished in Afroze and Khondker. For the qualitative and quantitative analysis of phytoplankton, a concentrated sample from each of the above mentioned depths were obtained via sedimentation process with Lugol’s iodine. A definite volume of sub-sample was counted under a Nikon compound microscope with a magnification of ×200 using a Sedgeweck Rafter Counting Cell (Graticules Ltd., U.K.). However, to identify the species higher magnifications (400 - 1000 ×) were used.

Source of Information: Dhaka Univ. J. Biol. Sci. 20(1): 7-13, 2011 (January)

Article Link (Online Journal): DOI: http://dx.doi.org/10.3329/dujbs.v20i1.8832

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Dissolved oxygen (DO) was detectable only in the top most water column (50 cm). In other depths, it did not fall within the detection limit. Even, the concentration of DO showed different values in different seasons. In winter, it was 1.4 mg/l which improved in monsoon (4.1 mg/l) via summer (3.9 mg/l). In autumn, it fell again (3.3 mg/l). In all the seasons bottom water contained a very high concentration of soluble reactive phosphorus (SRP). Highest value 1554 μg/l was obtained in the bottom water of summer. This increasing trend followed from winter to summer and then a fall from monsoon to autumn. The species Arthrospira platensis (Nordst.) Gom., Phacus ranula Pochm., Euglena variabilis Klebs and Oscillatoria chalybea (Mertens) Gom. showed vertical distribution in different seasons. A. platensis dominated the community in summer and monsoon seasons. In summer, the species showed its highest density in 50 cm water depth and then gradually depleted through 200 cm to bottom and regain its uniform distribution, throughout the depth. In a mesotrophic pond of Dhaka Khondker and Chowdhury(6), showed a continuous presence of Cryptomonas ovata Ehrenberg and Scenedesmus armatus Chod. at 50 cm, 250 cm and in the bottom all through the year. Light penetration in that pond was satisfactory, i.e., PAR was detectable up till bottom. However, in the present study PAR was always detectable up to 50 cm depth of water but, only in the monsoon and autumn it can reach up to 200 cm. However, throughout the study, no record obtained about the penetration of PAR up to bottom. So, A. platensis, O. chalybea, E. variabilis and P. ranula favour to grow in low light but nutrient enriched habitats.

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