Seston is tiny bits of stuff in water that come from living things, like plants or tiny animals.
Seston is important for the water and the things that live in it.
Examples:
The water is full of seston.
The fish eat the seston in the water.
Seston is important for the plants and animals in the water.
The seston in the river is like the food in the fridge.
In the ocean, there is a lot of seston for the animals to eat.
The seston in the lake is like the air we breathe.