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Limnological Status of Trimohini Beel of Rajshahi, Bangladesh

MD. AZIZUL ISLAM
Limnology Laboratory, Department of Botany, Rajshahi University, Rajshahi

ABDULLAH HARUN CHOWDHURY1
Environmental Science Discipline, Khulna University, Khulna

Abstract/ Executive Summary:

A total of 38 zooplankton genera and 26 physico-chemical variables were recorded in Trimohini Beel. This beel marked as a medium level of polluted wetland based on the values of the redox characteristics i.e. pH, DO, BOD, COD, Eh and rH2, chlorides, nitrites, ammonium, phosphate values etc. and on the presence of some zooplankton as indicator of pollution. A large number of inland fresh water non-culturable fishes and other aquatic biota of the Trimohini Beel may be eliminated in future due to mixing of continuous chemicals from agriculture fields. It is necessary to conserve the ecosystem of Trimohini Beel for the fresh water non-culturable fishes and other aquatic biota.

Keywords: Wetland, Agro-chemicals, Zooplankton, Fish disease, Catchment area, Eutrophic nature

Location: Trimohini Rajshahi, Bangladesh.

Start Date: 00-01-2010

End Date: 00-12-2011

Program Area: Risk Management in Agriculture

Commodity: Carp fish

Objectives:

To find out the physicochemical and zooplankton conditions of Trimohini Beel of Rajshahi for evaluating the pollution level of water of this wetland.

Methodology:

Trimohini wetland is near Rajshahi, Bangladesh. The investigated wetland lies between 24º35' to 24º40'N latitudes and between 88º35' to 88º40'E longitudes (Anon 1997). This perennial wetland is 24 km² (8 km????3 km) and covers an area of 50 km² (10 km????5 km) during monsoon. The catchments area is 150 km² (20 km????7.5 km), where intensive cultivation is being practiced by using organic, inorganic manures, insecticides, herbicides and fungicides. Water and plankton samples were collected from January 2010 to December 2011 in four different spots of the wetlands. Fortnightly samplings were done in this wetland and in each sampling date physico-chemical and biological samples were collected three times (8 A.M, 12 Noon and 4 P.M.). An average of these data for each spot was made and average depth of each spot was also determined. Water samples were collected from a depth 10-15 cm below the surface using a 250 ml. BOD bottle. Water colour was detected by following method as stated by Welch (1948). Temperature was noted by a digital thermometer (Model China Empex-range 10-110°C). Transparency was determined by a Secchi disc. A digital pH meter (Model pH epi HANNA instruments CEEN 50081-1) and portable conductivity meter (Model OSK CM-1K) were used for the measurement of pH and conductivity respectively. DO content of water was measured by DO meter (Model- JENWAY-9015). Free CO₂, CO₃, HCO₃, alkalinity, total hardness, chloride, BOD₅, COD, mobile NH₃ and NH_4-N were determined by following APHA (1989), FAO (1984) and (Welch 1948). Total phosphate, Oxidation-reduction Potential(Eh) and Oxidation reduction index (rH2) were measured by following Gautam (1990). Primary productivity was measured by Gaarder and Graan (1927). Plankton were collected by using a plankton net No. 20 silk bolting cloth of mesh size 76μm. Identification of plankton was done immediately after collection. Plankton abundance was measured by using a Sedgewick-Rafter counting chamber (Welch 1948) and expressed in unit/l whether it is an individual or part thereof.

Source of Information: J. Asiat. Soc. Bangladesh, Sci. 39(2): 173-182, December 2013

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The findings of the present study indicate that a large number of inland fresh water non-culturable fishes and other aquatic biota of the Trimohini Beel may be eliminated in future due to mixing of continuous chemicals from agriculture fields. Toxic chemicals have a deleterious effect on the wetlands ecosystem as a whole . So, it is necessary to conserve the ecosystem of Trimohini Beel for the fresh water non-culturable fishes and other aquatic biota. A sustainable management plan as well as area demarcation is necessary for the agriculture to protect the further degradation of water quality and biodiversity of the study area.

Knowledge Management: Journal