Question

Two types of aquatic organisms in a lake show specific growth patterns as shown below, in a brief period of time. The lake is adjacent to agricultural land extensively supplied with fertilizers.
Answer the questions based on the facts given above:
i. Name the organisms depicting patterns A and B.
ii. State the reason for the growth pattern seen in A.
iii. Write the effects of the growth patterns seen above.

Answer 1

Water pollution is being increased day by day on a huge scale. The pollution of water is maximally due to anthropogenic actions. Due to such activities of humans, the lakes, streams, ponds, rivers, oceans, and estuaries are getting polluted all over the world. Domestic sewage, industrial effluents, agricultural wastes are some of the main pollutants that pollute the water bodies.

Complete answer: The above-given graph shows the relation between the number of organisms and the time in which their population is changing.
According to the graph, the answer to the above given questions are-
i. Curve A shows the growth of planktonic or free-floating algae, on the other hand, curve B shows fish and other aquatic animals.
ii. The prime reason behind the growth of these planktonic organisms is the presence of excessive amounts of nutrients or fertilizers in waters which comes from the agricultural land that is situated adjacent to the lake.
iii. Due to the increasing planktonic organisms and algae the lake starts giving foul odors, the amount of dissolved oxygen decreases due to which the biological oxygen demand increases. The mortality rate of fishes and other aquatic organisms increases.

Note: Biological oxygen demand is used to measure the amount of biodegradable organic matter present in sewage water. The unit in which it is measured is mg per L. The process of biodegradation of organic matter from sewage water involves microorganisms that consume a lot of oxygen and thus the amount of dissolved oxygen decreases significantly, which ultimately causes mortality of fishes and other organisms.