Question

How are algal blooms caused?

Answer 1

Hint An algal bloom, also known as an algae bloom, occurs when the population of algae in freshwater or marine water systems rapidly increases or accumulates. The colouring in the water caused by the algae's colours is a common indicator.

Complete answer:
Available nutrients, temperature, sunlight, ecosystem disturbance (stable/mixing conditions, turbidity), hydrology (river flow and water storage levels), and water chemistry (pH, conductivity, salinity, carbon availability)
However, the complex combination of elements that cause and sustain an algal bloom is currently unknown, and it is impossible to assign algal blooms to a single cause. are all likely factors in the development and proliferation of algal blooms.
Nutrients
Algae and Cyanobacteria thrive on nutrients, which stimulate and sustain their growth. Eutrophication (nutrient enrichment) of streams is thought to be a significant influence. Phosphorus and nitrogen are the two most important nutrients in eutrophication.
Temperature
Early blue–green algal blooms are most common in the spring, when the water temperature is warmer and more light is available. During the warmer months of the year, the growth continues. The growth of Cyanobacteria is best at temperatures over 25°C. Blue–green algae have a competitive edge over other forms of algae whose ideal development temperature is lower.
Light
When light blue–green algae are subjected to high light intensities over long periods of time (photo-inhibition), their population declines, but when they are exposed to high light intensities periodically, their development is ideal. These conditions exist beneath the water's surface, where the light environment is constantly changing.
Turbidity
The presence of suspended particles and organic matter (flocs) in the water column causes turbidity. When a large amount of water is flowing through the system, turbidity rises (high discharge after a rain event). Low turbidity occurs when the water column contains just a tiny amount of suspended materials. Slow moving or stagnant water can cause low turbidity by allowing suspended particles to settle out of the water column.

Note: The majority of blue–green algae require stable water conditions with low flows, long retention durations, gentle breezes, and little turbulence; others favour murky habitats and mixing conditions.