Question

A lake which is rich in organic waste may result in
(a) Increased population of fish due to lots of nutrients.
(b) Mortality of fish due to lack of oxygen.
(c) Increased population of aquatic organisms due to minerals.
(d) Drying off the lake due to algal bloom.

Answer 1

A lake in which there is organic waste in abundance, there will be a lot of nutrients present which will favor the growth of plants, algae, which will compete for oxygen utilization.

Complete Step by Step Answer:
Due to the presence of organic waste in the lake, there will be nutrient enrichment which will lead to the excessive growth of plants, algae, and animals in the lake. This process is known as Eutrophication.
Natural eutrophication is natural aging due to nutrient enrichment of the water body. It is a slow process that may or may not be detectable in a human lifetime. A young water body has cold, clear water there is no nutrient enrichment. Runoff and streams draining into it gradually add nutrients, especially nitrogen and phosphorus, which encourage the growth of aquatic organisms. As the lake’s fertility increases, plant's and animals’ life burgeons, and organic remains begin to deposit on the lake bottom. Over the centuries, because the silt and organic dust assemble, the lake grows shallower and hotter, with the warm-water organisms replacing those who thrive in an exceedingly cold setting.
In cultural Eutrophication, the process is accelerated and thus, also known as accelerated eutrophication. It is caused by human activities like effluents from the industries and homes, run-off of fertilizer- rich agriculture fields. The nutrients over stimulate the growth of algae known as algal bloom causing unsightly scum, unpleasant odors, and robs the water of dissolved oxygen vital to other aquatic life.
Simultaneously, different pollutants flowing into a lake might poison whole populations of fish, who’s rotten remains additionally consume the water’s dissolved gas, therefore, choking the fishes to death.

So, the correct answer is, '(b) Mortality of fish due to lack of oxygen'..

Note:
- Eutrophication is both natural and accelerated.
-Natural Ageing may span thousands of years.
-The prime contaminants are the nitrates and the phosphates, which act as plant nutrients.
-Seaweed like kelps uses nitrogen and phosphorus for nourishment which can decrease eutrophication.