Seasonal Dynamics Of Aquatic Plants And Physicochemical Factors In An Urban Pond Of Jatrabari, Dhaka

Abstract

Samad Nagar pond situated in Jatrabari, Dhaka showed mean air temperature 20 - 30 °C and water temperature 19 - 28°C. Secchi depth (Zs) varied from 28.67 - 44.5 cm and pH 6.6 - 8.8. The mean DO and alkalinity ranged 5.34 - 10.00 mg/1 and 0.58 - 1.08 meq/1, respectively. Free C02, SRP and SRS ranged 1.31 - 4.21 mg/1, 158.39 - 635.70 pg/1 and 13.32 - 28.65 mg/I, respectively. During the study period, seasonal mean values of transparency was higher in monsoon and lower in winter. pH, alkalinity remained higher in winter but lower in monsoon. From aquatic plant communities of the pond, phytoplankton represented by 33 species of which 54.55% belonged to Chlorophyceae (54.55%) followed by Bacillariophyceae (13.64%), Cyanophyceae (13.64%), Euglenophyceae (13.64%) and Dinophyceae (4.55%). The population density of phytoplankton community ranged 6.16 - 25.96><1 06 ind/1. Benthic diatom density varied from 2.64- 11 .00 x 1 06 ind/1. Benthic diatom population was the highest (I lxlO6 ind/1) in late October and lowest in early September (2.64 xio6 ind/1). Chi a and phaeophytin concentration varied 5.10 - 228.51 pg/1 and 2.05 - 1513.36 pg/1, respectively. Aquatic macrophyte communities were represented by 23 species where Eichhornia crassipes (Mart.) Solms. , Ipomoea aquatica Forsk, Ipomoea fistulosa Mart., Telanthera philoxeroides Moq., Rumex maritimus L., Eclipta prostata (L.) L. and Salvinia natans L. were observed all over the study period.
 Asiat. Soc. Bangladesh, Sci. 41(2): 253-262, December 2015

Dynamics Of Environmental Factors In Relation To Phytoplankton Species In A Pond Of Old Dhaka, Bangladesh

“…The biomass of phytoplankton as chl a concentration ranged from196.08 to 362.76 µg/l. The recorded higher chl a concentration than the previous studies in urban ponds (Begum 2008, Akter et al 2015and Pramanik et al 2016 indicates an eutrophic nature of the studied pond. In the present investigation the highest phytoplankton abundance coincided with the highest concentration of chl a.…”

“…the water transparency varied from 21-54 cm in the pond. Other investigations on different ponds of Dhaka showed a wide variation in secchi depth such as 28.67 -44.5 cm in Samad Nagar pond (Akter et al 2015), 17.05-26.58 cm in Wapda pond (Naher et al 2015) and 50 to 81 cm in Bangshal pond (Pramanik et al 2016). Transparency of water (Zs) is affected mainly due to the increase in the seston load.…”

“…The highest (9.2 meq/l) and lowest (3.9 meq/l) fortnightly mean alkalinity were recorded in early April and early September, respectively. In some ponds of Dhaka city alkalinity was recorded to range between 0.48 meq/l and 7.95 meq/l (Naher et al 2015, Akter et al 2015and Pramanik et al 2016). The present observation of fortnightly mean pH value of 7.39 -8.30 is more or less similar with the results of Nahar et al (2010) in Joysagor and Pramanik et al (2016).…”

“…1). Recent studies on different urban ponds in Dhaka city showed different abundance of phytoplankton such as Samad Nagar Pond: 6.16×10 6 -26.84×10 6 ind /l; Bangshal Pond: 5.11×10 5 -34.9×10 5 and Wapda Pond: 35.20 × 10 6 -104.72×10 6 ind/l (Naher et al 2015, Akter et al 2015and Pramanik et al 2016.…”