Nygaard s Algal Index in Determination of Trophic State of lake Ecosystem

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1 Nygaard s Algal Index in Determination of Trophic State of lake Ecosystem M.K. Mahesh1 and S. P. Hosmani2 1.Professor and Head, Department of Botany, Yuvaraja s College, Mysore 2.Professor and Head, Department of Biotechnology, SBRR Mahajana First Grade College, Jayalakshmipuram, Mysore

2 INTRODUCTION Nygaard (1976) proposed five indices to evaluate the organic pollution of waterbodies based on various groups of planktonic algae occurring in them. These indices include Cyanophycean or Myxophycean index, Chlorophycean index, Bacillariophycean index, Euglenophycean index and a combination of these called compound coefficient index. All these are useful in determination of the trophic status of a particular lake. This calculation is based on the fact that algae have the capacity to tolerate organic pollution. Cyanophycean, Euglenophycean members can tolerate pollution and categorise the water body as eutrophic. Pennate diatoms and Desmids usually inhabit oligotrophic water. The oligotrophic or eutrophic status is based on the calculation of these indices proposed by Nygaard (1976).

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6 Materials and Methods Site Description: Hadhinaaru Lake is located at North latitude and East longitude at an altitude or meters HMSL. It is situated 20 Km away from Mysore city and is located in Nanjangud Taluk. It has an independent catchments area of 8.57 sq. kms. Its maximum depth when full is 5 mtrs. The Lake receives water mainly from Kapila River and Varuna canal. The water is almost clean and is used for irrigation. The major disturbance to the lake is by the villagers, who use the water extensively for domestic purpose. Thus slightly polluting the water near the village.

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12 Phytoplankton Analysis: Collection: Water samples are collected from the lake for plankton analysis in black coloured plastic carbuoys of one liter capacity every month between 10 am and 12 pm. Filamentous algae and other floating debris were eliminated. Preservation: For each sample collected, 25 ml of 4% formaldehyde was added (Welch 1948) along with few drops of Lugol s iodine. Sedimentation was done in Glass columns. The sediment was finally reduced to 20 ml and preserved in glass vials for further use.

13 Cont.. Enumeration: The algae were identified by making camera lucida drawings, photographs and consulting monographs. General identification-prescott (1982),Blue green algae Desikachary(1959),Chlorococcales- Philipose(1967),Bacillariophyceae-Sarode and Kamath(1984). Phytoplankton count was done by Lackey s drop method (1938) and modified by Saxena (1987). However for Nygaards index, organisms per drop were determined.

14 Nygaard s Trophic state indices Myxophycean index = Myxophyceae/Desmidaceae Chlorophycean h Index = Chlorococcales/Desmidaceae l Euglenophycean index = Euglenophyceae/Myxophyceae y p y + Chlorophyceae Compound Co-efficient = (Myxophyceae + Chlorophyceae + Bacillariophyceae + Euglenophyceae)/Desmidaceae

15 Physico-Chemical Parameters of hadhinaru Lake (2008) Sl. No. Parameters Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 1 Air Temperature ( 0 C) ph DO mg/l BOD mg/l Total alkalinity mg/l Total hardness mg/l Calcium mg/l Magnecium mg/l Chlorides mg/l Carbonates mg/l Bicarbonates mg/l Phosphate mg/l Sulphates mg/l Nitrate mg/l Nitrite mg/l Total Phosphorous TDS mg/l

16 Phytoplanktons

17 Phytoplanktons

18 Phytoplanktons

19 Table 1 : The rating of the Trophic state indices of Nygaards is presented belo Index Oligotrophic Eutrophic Myxophycean Chlorophycean Euglenophycean Compound < The distribution of Phytoplankton and Nygaard s Trophic state indices are presented in Table 2 and 3 respectively.

20 Table 2 : Distribution of Phytoplankton in Hadhinaaru Lake (Per / ml) Phytoplankton Group Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Chlorophyceae Myxophyceae Bacillariophyceae Euglenophyceae Desmidaceae

21 Table : 3 Nygaard s Trophic state Indices in Hadhinaru lake. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ave Trophy Myxophyceae Oligotrophy to eutrophic Chlorophyceae Eutriphic Euglenophycean Oligotrophic Compound coefficient Eutrophic

22 Results and Discussions The distribution of Phytoplankton and Nygaard s Trophic state indices are presented in Table 2 and 3 respectively. According to the Myxophycean index the lake shows oligotrophic nature from the month of August to November and later shows a gradual tendency towards eutrophism. On an average the lake tends from oligotrophy to eutrophy. As per the chlorophycean index, the value range from a minimum of 1 to a maximum of and indicates that the lake water is eutrophic in nature.

23 Cont However the Euglenophycean index shows oligotrophy for a major part of the year. They are less in number indicating that there is no organic pollution in the lake. The compound quotient values indicate that the lake always tends to become eutrophic. The water stored in the lake is river water and the ph ranges from 7.9 to 8.6 (slightly alkaline). This may be due to pollutants added along the flow of the river water filling the lake. The Bacillariophycean index cannot be calculated since centric diatoms were not present in the lake.

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25 Conclusion Nygaard s trophic state index can be a handy tool in determining the status of pollution in lakes; further it involves only algal identification and the detailed analysis of physiochemical parameters can be omitted. References: 1. Nygaard G 1976 Talverne fra Dansk Phytoplanktons. Gyledondal pp Welch P. S Limnological methods Balakiston, Philadelphia, USA pp Lackey 1938, Standard methods for the examination of water and Waste water. APHA, AWWA, WPCF (1995).

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