Water Turbidity as One of the Trophic State Indices in Butrinti Lake
- 1 Department of Physics, University of Vlora, Vlora, Albania
- 2 Department of Physics, University of Gjirokastra, Gjirokastra, Albania
- 3 Department of Physics, University of Gjirokastra, Gjirokastra, Albania
Abstract
In this paper we are presenting observations, data and some conclusions regarding the water turbidity and transparency of the aquatic ecosystem of Butrinti Lake in southern Albania. Located amidst a major tourist attraction area, Butrinti Lake is fed by fresh waters from surrounding areas and discharges into Ionian Sea. Although development is preset in the area, it is still minor as part of the area is a National Park. Turbidity, as an optical property which describes the cloudiness of the water, is a measure of the degree to which the water becomes less transparent due to the presence of suspended particulates, including sediments and phytoplankton. The water turbidity parameters were measured every two weeks over a year, monitoring three selected stations in this water ecosystem. Turbidity of water in such ecosystems is measured in FTU (Formazin Turbidity Units) using a portable turbid meter (in our case type HANNA HI 93703-11), which measures the intensity of light scattered at 90 degrees, as a beam of light passes through a water sample. In addition, turbidity is evaluated using a Secchi disk. The depth (Secchi depth) until the disk can be no longer seen by the observer is recorded as a measure of the transparency of the water (inversely related to turbidity). The Secchi disk has the advantages of integrating turbidity over depth (where variable turbidity layers are present). The relationship between the depth of the viewing disk and the turbidity can be characterized by an inverse curvilinear one. The defined trend line can be expressed by the same curve related to the data of Butrinti Lake. An R2 Value of 0.85 was calculated for the above equation. Variations were observed on turbidity level of the selected stations in this ecosystem. These differences on the turbidity values of selected stations of water body can be explained by the communications sea-lagoon, fresh water supply as well as by the pollution due to human activity near a certain station. The monitored water ecosystem can be characterized by certain level of turbidity, based on the trophic state classification by Hakanson and Carlson. Furthermore, relationship between turbidity and trophic state evaluated by other bio-indicators of the monitored ecosystems is analyzed.
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