15.)   Algal blooms are significant events in lakes or seas; what kinds of organisms cause these blooms and their impact on the environment.

A.)

Algal blooms:

1. Algal blooms are high-growing toxic algal species.
2. These excessive growing algal bodies lead to the accumulation of algae in a freshwater body.
3. The process of a water body getting covered with algal blooms composed of phytoplankton (microscopic algae) and algae is known as eutrophication.

Causes of algal blooms:

1. Due to the deposition of harmful unfiltered chemical waste from factories, a population of harmful algal bloom starts growing.
2. The fertilizers high in chemicals like sulfur, phosphorus, nitrogen, etc., also lead to algal blooms.
3. The untreated wastewater from sewage treatment plants also leads to algal.

Harmful effects of algal blooms:

1. The algal blooms can destroy aquatic life as they consume oxygen available for aquatic plants and animals.
2. The algal blooms also tend to block sunlight for the coral reefs.
3. The aquatic plants and corals cannot make their food due to the blockage of sunlight.
4. These harmful algal blooms release toxic chemicals into the water bodies that enter the food chains and hence can create toxicity to the animals of the food chain.