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RAJASTHAN PMT Rajasthan - PMT Solved Paper-2010

  • question_answer
    A lake near a village suffered heavy mortality of fishes within a few days. Consider the following reasons for this.
    I. Lots of urea and phosphate fertilizer were used in the crops in the vicinity.
    II. The area was sprayed with DDT by an aircraft.
    III. The lake water turned green and stinky.
    IV. Phytoplankton populations in the lake declined initially thereby greatly reducing photosynthesis.
    Which two of the above were the main causes of fish mortality in the lake?

    A)  II, III                     

    B)  III, IV

    C)  I, III                      

    D)         I, II

    Correct Answer: C

    Solution :

    Presence of large amounts of nutrients in waters causes excessive growth of planktonic (free floating) algae, called an algal bloom, which imparts a distinct colour to the water bodies. Algal blooms cause deterioration of the water quality and fish mortality.


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