Seasonal variation of aquatic macrophytes, phytoplankton association and soil and water qualities at some selected sites of Savar–Dhaka regions of Bangladesh
Md Mahabub Alam, M Mahfuzur Rahman, Gazi Musharof Hosain
Seasonal variation of aquatic macrophyte and phytoplankton and analysis of soil and water at some selected sites of Savar – Dhaka regions of Bangladesh namely Hazaribagh Site-A), Hemayetpur Site-B), Banktown Site-C) and Jahangirnagar University Site-D, control site) of Dhaka district were investigated from April-2011 to January-2012. Data on the number of species and their individuals per 2m2 randomly selected quadrats were recorded properly. Site- A, B and C water bodies were located in the industrial areas of Hazaribagh tanneries areas under Hajaribagh thana and teenage modern fashion and maxcom garments area, Hemayetpur and, Doel complex, Bank Town area under Savar Thana. The site-D water body was located in Jahangirnagar University besides the new arts building. Seasonal variation was recorded in all 03 three) different seasons namely summer, rainy and winter seasons. A total of 47 species of aquatic macrophytes under 30 different families were recorded from the research sites. The highest number of species was 24 in the summer season with a total of 314 individuals in site –B followed by 20 with 333 individuals in site –D, 17 with 518 individuals in site-C and 8 with 142 individuals in site – A. The highest number of species was 18 in the rainy season with a total of 458 individuals in site –D and 18 with a total of 378 individuals in site – B followed by 14 with 420 individuals in site –C, 5 with 153individuals in site-A. In the winter season, the highest number of species 13 were recorded in site – C with 370 individuals, 13 with 325 individuals in site – B followed by 12 with 97 individuals in site – D and 6 with 68 individuals in site – A. Seasonal variation is continuously occurring among them and also species vary for site variation. The most commonly occurring species in all four sites was Eichhornia crassipes. The total species number of macrophytes and their individual numbers were enriched with site-D water body in Jahangirnagar University than that of other water bodies. The average highest density resulted in 2.47 in site – C, the highest relative density 12.22 in site - A, The highest frequency 19 in site – D, the highest relative frequency 12.44 and the highest abundance value 7.35 were found in site – C. A total of 57 genera under 04 phytoplanktonic classes were recorded. From the total occurrence, it is clear that the highest dominant phytoplanktonic class was Bacillariophyceae total occurrence 5076 under 16 genera) followed by Chlorophyceae total occurrence 4053 under 28 genera), Cyanophyceae total occurrence 3022 under 10 genera) and Euglenophyceae Total occurrence 660 under 03 genera) respectively. The highest number of phytoplanktonic occurrences was observed in site – A in the rainy season 1202) and the lowest occurrence was observed in site - C in the same season 923). Soil moisture content was the highest 21.56 % at the rainy season in site D and lowest 1.46 at winter season in site – A. Maximum water holding capacity of the soil was the highest 46 % at the summer season in site D and lowest 31 % at the rainy season in site – C. Soil PH value was highest 6.8 at the summer season in site D and lowest 5 in site C in summer and site D in the rainy season. The highest water temperature was recorded in site – C in the summer season 380C) and that of lowest was recorded in site – D in the winter season 22.30C). The highest PH value recorded was 7.8 in site – A and that of the lowest value recorded in site – B in the rainy season 5.5). The highest TDS value was 3400 mg/L at winter season in site – A and lowest 400 mg/L at the rainy season in site A and winter in site – D. The highest TSS value 400 mg/L at winter season in site – A and lowest 100 mg/L at summer in site – A and at rainy in site –D. The highest amount of Dissolved Oxygen DO) was calculated in site – D in the rainy season 4.379 mg/L) and that of the lowest value calculated in site – A in the summer season 1.056 mg/L). Biochemical Oxygen Demand value calculated was the highest in site –D in summer season 2.226 mg/L) and the lowest in site – A in summer and rainy season and site – B in the winter season 0.453 mg/L). The highest COD value was 375 mg /L at summer in site – A and the lowest was 35 mg/L at winter season in site – D.