What determines the distribution of organisms in the surface layer of water?

Life in water
As you know, according to one of the most common theories of the origin of life, life first originated in water. The first creatures got out of the water and settled on land. Water is vital to many organisms that have adapted to live on earth. Today, the species diversity of organisms living on land and in water is enormous. Still, the waters of seas, oceans and rivers are still home to countless aquatic inhabitants today. Several layers can be distinguished in water bodies, and they, in turn, are inhabited by different creatures, which can be divided into groups:
living organisms of the surface layer of waters;
living organisms of the water column;
deep water;
bottom.
It is quite natural that the percentage and distribution of organisms in water is not uniform and depends on many factors, which will be described below.

Distribution of organisms in water
Most living organisms live in the surface layer of water for a number of reasons:
it is very warm in surface waters;
there is a lot of light closer to the surface;
surface waters are rich in oxygen.
A lot of plankton live in surface waters. These are the smallest microorganisms that are invisible to the naked eye. This plankton is food for most small and large fish. Even such large creatures as the blue whale feed on plankton. The blue whale filters plankton with a whalebone. These are special plates that filter the plankton-rich water. Many corals prefer warm surface waters. Jellyfish love warm and oxygen-rich surface waters. Also, we must not forget about such microorganisms as pleiston. These organisms inhabit the upper water film. They are even smaller than plankton.
Unfortunately, today the waters of the world’s oceans are very polluted by various emissions. This negatively affects the life of aquatic life. First of all, residents of surface waters suffer. This is very bad, because the less plankton there is, the less fish there will be. And due to the general interconnection in the food chain, the number of various living organisms decreases.