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Marine ecosystem: what is it, characteristics, flora and fauna

The marine ecosystem, origin of life and source of a gigantic and sometimes unknown diversity of regions, marine plants, marine animals, microorganisms and organic molecules. Although the appearance of marine ecosystems seems homogeneous, the reality is that it is one of the most heterogeneous ecosystems on the planet, with very different characteristics from the poles to the tropics, as well as from one side of the world to the other. The communities of living beings that coexist in saltwater ecosystems demonstrate the great variety and richness of these regions, thus constituting places full of life in mangroves and reefs, in pelagic systems of the open sea and even in the deep sea.

In this AgroCorrn article you will discover one of the most precious and at the same time threatened ecosystems on the planet, the marine ecosystem: what it is, characteristics, flora and fauna .

You may also be interested in: Polar ecosystem: characteristics, fauna and flora

What are marine ecosystems

Marine ecosystems are a type of aquatic ecosystem , characterized by the presence of salt water as its main component. Marine ecosystems include, in turn, different ecosystems, such as oceans , seas, marshes, reefs, coastal shallow waters, estuaries, coastal saltwater lagoons, rocky coasts and coastal areas.

As we can imagine, this great variety of marine ecosystems together support an astonishing diversity of plant and animal life. In the next sections we will see which groups of marine plants and marine animals make up the biodiversity of these ecosystems, as well as the main physical-chemical characteristics that define them.

Characteristics of marine ecosystems

The set of all marine ecosystems occupy 70% of the planet’s surface . Distributed in different biogeographic zones, marine ecosystems present the following characteristics common to all of them:

  • They are included within the group of aquatic ecosystems .
  • They are composed of waters with dissolved salts as the main component.
  • Said salt water has a higher density than those other freshwater aquatic ecosystems , guaranteeing the survival of marine plants and marine animals adapted to this high water density.
  • In them there are two types of regions depending on whether they receive sunlight rays or not, thus differentiating the photic regions (with light) and the aphotic regions (without light).
  • The correct functioning of marine ecosystems depends to a large extent on marine currents, whose function is based on mobilizing and transporting the various nutrients that allow the development and survival of the flora and fauna that inhabit these complex ecosystems.
  • Marine ecosystems are a source of great biological wealth, being constituted by different biotic factors such as the presence of producer organisms (plants) and primary consumers (fish and mollusks), secondary consumers (small carnivorous fish) and tertiary (large carnivorous fish). size), as well as decomposing organisms (bacteria and fungi).
  • In turn, certain abiotic factors define the properties and characteristics of these natural ecosystems, such as the temperature, salinity and pressure of their waters, as well as the amount of sunlight it receives.

Flora of marine ecosystems

Numerous plants, both submerged and emerging and floating species, constitute the rich plant biodiversity of each and every one of the marine ecosystems. Directly related to the physicochemical characteristics of the type of marine ecosystem in which they inhabit, these species will present some or other forms of life, also having certain vital needs.

Seaweed: the most widespread

The seaweed (United Algae)they constitute par excellence the flora of marine ecosystems. A great variety of families, genera and species fill marine ecosystems with life and color, grouping themselves into those commonly known as brown algae (protist organisms – Class Phaeophyceae), red (Phylum Rodophyta) or green (Eukaryotic Plants – Clorophyta Division). Some are microscopic (diatoms and dinoflagellates), while others are considered macroalgae, highlighting the gigantic laminar algae of the genus Macrocystis. They have very varied forms of life and different habits, thus existing algae that float and many others that live fixed to the seabed, on rocks or sometimes even on animals or other plants. Always adapted to the temperatures and other physical-chemical characteristics of the waters in which they grow and live,

As a curiosity, we recommend reading this other Green Ecology article about the Similarities and differences between plants and algae .

More important marine flora

In addition to seaweed, the flora of marine ecosystems is represented by various plant species, among them the so-called sea ​​grasses (species of the families Zosteraceae, Cymodoceaceae, Ruppiaceae and Posidoniaceae), the only flowering plants in these ecosystems; the mangroves (with species such as the red mangrove: Rhizophora mangle and the white mangrove: Laguncularia racemosa ) and the abundant phytoplankton .

Fauna of marine ecosystems

The seas, oceans, coasts and other marine ecosystems constitute some of the most biodiverse habitats in the world, in which animals of different groups, families and species coexist in biological balance.

Both small and large vertebrates and invertebrates, as well as microorganisms, coexist in harmony in the marine ecosystems of the planet. Let’s put some examples of the fauna of marine ecosystems to learn more about how characteristic and varied it is:

Mammals of marine ecosystems

Marine fish

  • White shark ( Carcharodon carcharias )
  • Marbled stingray ( Aetobatus narinari )
  • Common Bonito ( Sarda sarda )
  • Swordfish ( Xiphias gladius )
  • Seahorses (genus Hippocampus)

Marine reptiles

  • Leatherback turtle ( Dermochelys coriacea )
  • Hawksbill turtle ( Eretmochelys imbricata )
  • Loggerhead sea turtle ( Caretta caretta )
  • Marine crocodile ( Crocodylus porosus )
  • Marine iguana ( Amblyrhynchus cristatus )

Sea birds

  • Kelp gull ( Larus dominicanus )
  • Andean gull ( Chroicocephalus serranus )
  • Mediterranean gull ( Ichthyaetus melanocephalus )
  • Traveling Albatross ( Diomedea exulans )
  • Penguins (Spheniscidae family)


  • Bivalve mollusks: oysters (family Ostreoida), clams (family Veneroida) and mussels (family Mytilidae).
  • Cephalopod mollusks: octopus (order Octopoda), squid (order Teuthida), nautilus ( Nautilus pompilius ) and cuttlefish (order Sepiida)
  • Echinoderms: starfish (class Asteroidea) , sea urchins (class Echinoidea) and holothurians (class Holothuroidea).
  • Cnidarians: jellyfish (subphylum Medusozoa), anemones and corals (subphylum Anthozoa)


Protozoa and the characteristic marine zooplankton (composed mainly of krill: Meganyctiphanes norvegica ).

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