Maharashtra State PSC Model Paper 1

The correct answer is 2 and 3 only.

• Effects
  • The decrease in the DO (Dissolved Oxygen) Levels
    • Coldwater contains more oxygen than hot water so increases in temperature also decrease the oxygen-carrying capacity of water (leads to anaerobic conditions in water bodies). 
    • In addition, raising the water temperature increases the decomposition rate of organic matter in water, which also depletes dissolved oxygen.
      • These decreases in the oxygen content of the water occur at the same time that the metabolic rates of the aquatic organisms, which are dependent on sufficient oxygen supply, are rising because of the increasing temperature. Hence, Statement 1 is NOT correct.
      • Only statements 2 and 3 are correct.
    • Ocean invertebrates, fish, and marine reptiles are obligate poikilotherms - their body temperatures depend entirely on the surrounding water. 
      • Each species is adapted to a single range of temperatures and many pass through several different life stages, each with an individual range of tolerance.
      • The ocean's vast populations of microbes, fungi, and sea plants also rely on narrow temperature ranges for optimal growth.