Question

The accompanying graph follows the progress of an algal bloom and two associated environmental factors over the course of a year in the North Atlantic Ocean.

Relative no. of algae	Relative light intensity	Relative concentration of nitrate
W	Y	X
X	W	Y
W	X	Y
X	Y	W

Which line in the table gives the correct identity of W, X and Y?

Answer 1

Hint: Algal blooms are formed due to blue-green algae or cyanobacteria. Increased number of algae causes depletion of oxygen in water.

Step by step solution:
Algal blooms always occur in standing water. It uses all the dissolved oxygen in water which causes the fishes living in water to die. The growth of algal bloom is so fast that it can spread all over the water body in very less time and can cause the entire population of the water body to die.
This increase in algal bloom usually starts in early spring and lasts till early summers. This event is mainly seen in the North Atlantic, coastal areas and sub-polar regions.


So, option D is correct.

Note: Changes in climate also affect the algal bloom. These changes along with the loss of nutrients in water bodies causes algal bloom to grow more intensely. Algal blooms are induced during warmer temperatures as it prevents water from mixing. Climatic changes like drought makes the water saline and causes algae to bloom. Changes in rainfall patterns and alternating drought period affect the nutrient level which in turn causes the algae to bloom. If the sea level rises, it would make the sea stable providing good condition for algal bloom.