Imagine you are a stone thrown into the ocean. What do you notice? Blue, which seems to never end, a lot of living things (biotic) and a lot of non-living (abiotic) factors create a very large ecosystem. We call the name of this system Marine Ecology. There is a great order and functioning in the sea as everywhere there are living beings. We can think of it as interconnected rings. If one of these rings breaks, the rings will fall apart. There is a similar link in Marine Ecology.

Figure 1

Figure 1

As with most ecosystems, the ecosystem has primary prıducers at its conglomeration. In the ocean, these include both microscopic (phytoplankton and some bacteria/Archaea) as well as microscopic organisms (macroalgae and marine plants). ¹

Trophic Levels

Primary producers supply nutrients to all other creatures in the world and therefore from the base of the entire food web. Organisms that directly consume primary producers are called primary consumers. In the ocean, these include zooplankton, herbivorous invertebrates, and herbivorous vertebrates². These organisms also turn become food for creatures such as herbivores and carnivores, which are composed of secondary consumers. Tertiary consumers and upper-level consumers are fed with all these species and we call these carnivores. We know these groups as Trophic Levels.

An average energy loss of 90% occurs between each trophic level. When it comes to energy, if a higher-level living creature eats a lower level, only 10% of that energy is stored in the body. For instance, if a killer whale eats a seal, only 10% of the energy it consumes is converted into energy stored in the body. The same energy losses occur at other levels. Based on these energy losses, the number of living things decreases as we move to the upper layers.

Food Webs

The network of feeding interactions among diverse co-occurring species in a particular habitat³. Many creatures maintain different areas of their lives at different trophic levels. As a consequence, it is also an indication that predators and prey can also be involved in different groups.

Nutrient Cycles

Certain elements (and nutrients) are needed by living things. The most important of these are carbon, C, hydrogen, H, oxygen, O, nitrogen, N, and phosphorous, P ⁴. These are absorbed by primary producers from seeing. Then they are included in organic molecules. Carbohydrates and fats contain elements of carbon, hydrogen and oxygen. In addition to these, protein also contains nitrogen. Nucleic acids include carbon, hydrogen, oxygen, nitrogen and phosphorous. These molecules are found in nucleic acids (DNA and RNA), which contain the energy, cellular structures (cells and body parts), hormones, enzymes and genetic information that all living things need.

  • Symbiosis: Organisms do not only engage in trophic interactions. They also constantly interact differently with other creatures in the ecosystem. There are many samples of cooperation and competition in the marine ecosystem. There are three types of symbiotic relationships, all host and enigmatic.
  • Symbiotic Relationship: In a symbiotic relationship in which one of the creatures benefits while being damaged. It is expressed as “(+, – )”. The damaged creature is called a “host”. The creature that benefits are called a “parasite”. As an example of this relationship, I can give examples of living, fleas or intestinal worms, which also appear in humans.
  • Mutualistic Relationship: Symbiotic is a symbiotic life form in which both creatures benefit. It is expressed as “(+, +).  I can give anemone and clownfish as an example of this relationship. A species of sea coral called anemone forms the habitat of the clownfish. Anemon protects the clownfish from its enemies with its scorching tentacles, while the clownfish removes the anemone-fed fish.
  • Commensalism Relationship: It is a symbiotic life form in which one living thing is not affected at all and the other benefits ⁵. It is expressed as “(0,+)”. As a sample of this relationship, we can say its relationship with the fish named Remora Brachyptera which wanders alongside sharks.


  1. Mariscal, R. N. (1974). Experimental Marine Biology. London: 24/28 Oval Road.
  2. Cushing, D. H. (1975). Marine Ecology and Fisheries. Cambridge University Press. ²
  3. Whittaker, R.H. Communities and Ecoystems (Collier Macmillan, London,1975).
  4. May, R.M. Nature 238, 413-414 (1972)
  5. Hall, S.J., & D. Raffaekkş. 1991. Food-web patterns: lessons from a species-risch web. Journal of Animal Ecology 60: 823-842.

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