Nutrients are necessary

The water is cycling constantly and transporting among others nutrients. The nutrients are leaching partly into the seas and other water system, which is a positive thing because they are essential for the life in the water.  The problems appear when too much nutrients are released to the water system.

Nitrogen and phosphorus are the ingredients of the base production

There are many different and complicated food chains and networks in the aquatic ecosystem. They consist of producers, consumers and decomposers, which all are dependent on each other.

Plants, algae and vegetal plankton are the producers in the water. They are capable of photosynthesis with chlorophyll, sunlight and carbon dioxide.  As well, nutrients, in particular nitrogen and phosphorus, are required in photosynthesis. Photosynthesis generates oxygen and sugar. Sugar is used in the vital functions and multiplying of the producers. Certain bacteria are also capable of photosynthesis.

The growth and multiplying of plants, algae and vegetal plankton based on photosynthesis is called the base production. Base production is the first and the most essential link in the food web. In consequence, nitrogen and phosphorus are not harmful substances but vital growth nutrients.

Food chain begins from the base production

The base production utilizes the next ring in the food chain, consumers. Animal plankton like the water fleas, the parasitic copepods and the ciliates, is eating vegetal plankton. Animal plankton on the other hand is a nutriment to the fish and birds.

Dead animals and plant parts are sinking to the bottom, which is called sedimentation. At the sea bed, the decomposers use dead biomass as nutriment. Decomposers are for example bacteria and protozoa. Decomposition releases important minerals and nutriments back to the water, where plants use them again. This is how the nutrients cycle in the food web.