PHYTOPLANKTON AND MACROPHYTES OF KUNIAR HAOR, KISHOREGANJ IN RELATION TO SELECTED PHYSICOCHEMICAL FACTORS

Abstract

The area of Kuniar Haor is about 37 ha and it is interconnected with the River Dhonu. The catchment consists of 5 villages namely, Baribari, Shohila, Borohathi, Shimulbak and Mollapara under the Upazilla Itna, Kishoreganj. The Haor was investigated from February 2016 to January 2018. Samples were collected at one month intervals from 3 sampling stations. A total of 24 samplings were made where 72 samples were analysed during the two years’ study period. Eleven physicochemical parameters namely air and water temperature, secchi depth (SD), pH, alkalinity, total dissolved solids (TDS), conductivity, dissolved oxygen (DO), soluble reactive silicate (SRS), soluble reactive phosphorus (SRP), NO3-N and four biological parameters as chl-a, phaeopigment, phytoplankton density (PD), and macrophyte abundance were investigated. In all stations the monthly ranges of air and water temperatures were 18.5 – 38.11 oC and 19 – 33.41 oC, respectively. The ranges of other determinants were Secchi depth, 7.5 – 95 cm; pH, 6.4 – 8.1; TDS, 17 - 97 mg/l; conductivity, 31 - 208 μS/cm; DO, 4.4 – 14.8 mg/l; alkalinity, 0.5 – 5.5 meq/l; SRS, 0.77 – 23.19 mg/l; SRP, 1.05 – 55.28 μg/l; NO3-N, 0.04 – 1.15 mg/l; chl-a, 1.18 – 32.56 μg/l; phaeopigment, 0.13 – 46.32 μg/l and phytoplankton density, 1.8 – 62.2 (×104ind./l). The seasonal dynamics of the above mentioned hydrobiological components of the Haor ecosystems were also elaborated. In the studied Haor area, namely station-1, station-2 and station-3, the total species of phytoplankton recorded were 115, 120 and 90, respectively. The recorded genera were 51 in station-1, 52 in station-2 and 51 in station-3. The distribution of the recorded species showed following pattern: maximum number of species 37.4% (Station-1), 34.1% (Station-2), and 37.7% (Station-3) among the flora studied was represented by the Chrysophyta. Dominance of Chrysophyta followed by Euglenophyta (28.7% in station-1, 31.7% in station-2 and 28.8% for station-3), Chlorophyta (21.7% for station-1, 23.3% for station-2 and 21.1% for station-3), Cyanophyta (6.08% for station-1, 4.1% for station-2 and 4.4% for station-3), Cryptophyta (3.5 % for station-1, 3.3% for station-2 and 5.5% for station-3) and Pyrrophyta (2.6% for station-1, 3.3% for station-2 and 3.3% for station-3). Based on the preliminary identification, 33 species of phytoplankton may be considered as new records for the Bangladesh. The distribution of new records of phytoplankton is as follows: Euglenophyta dominate (9 taxa) followed by Chlorophyta (7 taxa), Chrysophyta (6 taxa), Cryptophyta (7 taxa), Cyanophyta (2 taxa) and Pyrrhophyta (2 taxa). A total of 48 species of aquatic macrophytes was recorded where Ipomoea aquatica Forsk and Ludwigia adscendens (L.) Hara were found to be the most dominant species. Pearson correlation of phytoplankton density showed significant positive correlation (at 1% and 5% level) with alkalinity, nitrarte-nitrogen and phaeopigment in all stations. DO showed only positive correlation with air and water temperature, Secchi depth at station-1, water temperature, secchi depth, pH, and phytoplankon density at station-2, secchi depth, with air, water temperature, alkalinity TDS, SRP at station-3 According to Shannon-Winner diversity index, Station-3 supports higher diversity at genus and specie level. Jaccard Index shows three stations are highest 53.84 % similar in October 2016 and their intersecting members are 7. The value of TDI indicate the effects due to contamination of organic matter on the wetland. In the investigation TDI = 3.3% and pollution tolerant taxa is 18.5%. As the proportion of TDI count is ˂20%, so the wetland is free of significant organic pollution. The fish to phytoplankton ratio was calculated as 933870: 1.94 × 1012. This indicates that the growth of plankton feeding fishes mostly depends on plankton dynamics of the water body in the studied Haor area. The macrophytes fed on by the fishes in this Haor represent several families of which major ones are Amaranthaceae, Araceae and Typhaceae. These are so potential for fish production, wildlife conservation, fertilizer and soil additive. The present limnological and hydrobiological study on the Kuniar Haor reveals that the water body has been passing its meso-eutrophic status. After having an intensive anthropogenic disturbance from the catchment the quality of water might get changed. And it is likely that in the near future these wetlands would be turned to eutrophic followed by hypertrophic systems. This condition is undesirable not only for ex-situ conservation but also for implemening future conservation strategy. It also becomes detrimental to the components of the biodiversity. The study also reveals that management of Kuniar Haor should be taken into consideration not only to stop the disturbances within the study sites but also the disturbances in their surrounding land areas. The investigation generated some important baseline data on the pollution status and phytoplankton community structure of the Haor. These data would be helpful in planning for future policy decisions on using the reservoir as an ecotourist center as well as in the better conservation and management of the precious wildlife in the world-famous sanctuary.