MARINE BIOMES: CHARACTERISTICS, TYPES, FLORA, FAUNA - ENVIRONMENT - 2025

The marine biome are ocean areas have physical and biological characteristics similar, gathering various ecosystems. They are characterized by their high content of salts, variation in temperature, density and brightness gradient.

The marine environment consists of a large body of water interconnected by both surface and deep currents that transport nutrients, living beings and pollutants. All this determines a zoning of the marine areas both horizontally and vertically, finding differences between the coastal zone and the open sea.

Marine biomes. Source: LBM1948 / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

The United Nations Environment Program (UNEP) recognizes 66 large marine ecosystems that are grouped into marine biomes that are not always clearly delimitable. Some classifications separate some particular biomes such as coastal zones, open ocean, coral reefs, macroalgal forests, and deep-sea hydrothermal vents.

Marine biomes are inhabited by thousands of species of almost all known groups of living things. Highlighting the algae and underwater grasses in the flora, and the fish, marine mammals, mollusks, crustaceans and bivalves in the fauna.

Characteristics of marine biomes

The world's oceans are interconnected, forming a large body of water that does not present clear barriers to the dispersal of living beings. Barriers in marine biomes are determined by differences in temperature, pressure, lighting, and nutrients.

The establishment of these barriers is influenced by latitude, the coastal relief and the contributions of fresh water and other materials from the mainland. Likewise, areas are determined both in the horizontal and vertical dimensions of the oceans.

- Sea water

The most relevant characteristic of marine biomes is that the environment where they develop is seawater. This has particular characteristics of composition and pH, as well as is subject to the effect of different environmental factors.

Salinity

Sea water is salty, with a high content of mineral salts that are dragged from the mainland by the water currents coming from rainfall. However, the concentration of salts is not the same in all areas, varying between 30 and 50 grams per liter of water, the ocean with the highest concentration being the Atlantic.

- The ocean temperature

Water has a high caloric capacity (it is capable of absorbing large amounts of heat), but its cooling is slow. Also, the temperature is not the same in all the world's oceans and varies with latitude and depth.

For example, in the equatorial Atlantic Ocean the temperature reaches 29 ºC, while in the Arctic it drops to -50 ºC in winter. While vertically the temperature varies from maximums of 30 ºC to temperatures below 0 ºC in the abyssal depths.

- Solar radiation

The incidence of solar radiation on the oceans varies with latitude and its penetration is limited by the density of the water. In this sense, sunlight does not reach beyond the first 200 m depth, being a limitation for primary production based on photosynthesis.

- Ocean currents and global ocean circulation

The oceans are interconnected by continuous flows of water masses, that is, ocean currents. These have great relevance in the circulation of living organisms, nutrients and pollutants.

- Marine areas

In the horizontal dimension, the littoral or neritic zone (area of ​​the coast affected by waves and tides) and the pelagic zone are presented. The latter corresponds to the rest of the water column that is above the ocean floor and beyond the littoral zone.

Then, in vertical terms, the water column presents the photic zone defined by the surface water layer as far as the sunlight reaches, which is about 200 m. Below this is the aphotic area where sunlight cannot reach.

On the other hand, the ocean floor is called the benthic zone as opposed to the pelagic zone or water column. This oceanic floor when it is located below the aphotic zone is called the abyssal zone (at great depths).

Types of marine biomes

There is no clearly established delineation of marine biomes, although there are some biomes that can be delineated quite precisely. In this sense, 9 marine biomes are presented here, one of them, the mangrove-underwater prairie, a transition between land and sea:

- Mangroves and underwater meadows

They are coastal ecosystems of transition between land and sea, which in turn are directly associated with underwater grasslands. This biome is distributed along almost all the coasts of the tropical and subtropical seas of the world.

Mangroves. Source: Boricuaeddie / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

Mangroves are coastal forests of small trees adapted to conditions of high salinity in association with underwater monocot grasslands. They are breeding sites for many marine species and extend along much of the coasts of tropical and subtropical seas.

- Coral reefs

They develop in waters with temperatures above 20 ºC in tropical and subtropical areas, and their base is colonies of coral polyps forming calcareous external skeletons.

When the colony multiplies, it constitutes a barrier similar to a reef that generates a protected area from currents and waves where many marine species converge.

Coral reef. Source: No machine-readable author provided. HeikeM assumed (based on copyright claims). / Public domain

These coral reefs develop in shallow waters (photic zone) and receive a large amount of solar energy. Due to these characteristics and the biodiversity they concentrate, they form one of the most productive marine biomes.

- Macroalgae forests

Underwater forests of macroalgae or giant algae develop in various areas of the world in subtropical seas. These algae can reach up to 30 to 50 m in length and inhabit nutrient-rich waters with temperatures below 20 ºC.

They are found in various areas of the world such as the Gulf of Mexico and in the maritime province of Magallánica in Argentina. As well as in the western US and Canada, as well as on the shores of the Cape of Good Hope in South Africa, the shores of Japan and New Zealand.

- Tropical seas

They have average temperatures above 25 ºC in most cases and a lower amount of dissolved oxygen in the water. These waters have less nutrients than cold seas, with high solar radiation uniformly distributed throughout the year.

These are spread throughout the intertropical area near the continental masses and tend to have great biodiversity. One of these is the Caribbean Sea, with warm waters and great biological wealth, especially sea turtles.

- Temperate seas

They are waters with average minimum temperatures of up to 12 ºC, or in any case not lower than 10 ºC, and are rich in nutrients. They are located in a strip between the tropics and the polar areas and the solar radiation they receive varies with the seasons, being higher in summer.

An example of this type of sea is the Mediterranean between Europe, Africa and Asia, characterized by a high concentration of salts and nutrients. Due to these characteristics, in this sea population explosions of algae are frequent

- Cold seas

They are distributed from the polar zones to approximately 45º north and south latitude, although these limits are not so strict. Thus, on the western coast of South America the cold waters rise beyond the tropic of Capricorn due to the effect of the Humboldt current.

These marine waters have temperatures below 17 ºC and are very rich in nutrients that rise with them from the seabed. They present a great diversity of fish attracted by the great development of plankton due to the abundance of nutrients.

For this reason, on the coasts of Chile and Peru there are more than 600 species of fish, as well as whales, dolphins and sea lions. In addition, in the case of polar seas, a frozen surface layer forms during winter.

- Open coasts

In many continental areas there are coasts open directly to oceanic waters where seas do not form. For example, the eastern and western coasts of South America, as well as most of the western coasts of Africa and Australia.

In these cases, the physical conditions of the waters do not differ much from those of the open sea, except in the cases of the mouths of large rivers. In them, flora and fauna typical of the intertidal zone and the continental shelf can be established.

- Underwater hydrothermal fumaroles

The oceanic abyssal depths were considered submarine deserts until not many decades ago, because sunlight does not reach such depths, so primary productivity is restricted.

However, the explorations carried out have confirmed the existence of underwater oases rich in biological diversity. They take place around the fumaroles that expel water and gases at temperatures from 25ºC to 300ºC.

They are found in the mid-ocean ridges of the Atlantic and Pacific, as well as in hot spots in the submarine crust at depths between 1,000 and 5,000 m.

These vents provide heat and mineral elements to their environment, such as sulfur that can be used by archaea (prokaryotic organisms) to do chemosynthesis. In addition, there are phototrophic bacteria that use the glow of black fumaroles as a light source, as well as bivalves and abyssal fish.

- Ocean biome

The largest ocean area is the pelagic region of the open ocean, beyond ocean seas and coasts. It forms a practically continuous biome throughout the world's oceans, thanks to the system of marine currents through which migratory species such as whales and sea turtles circulate.

Flora

The flora of the different marine biomes is constituted mainly by species of algae and in the coastal biomes there are species of aquatic angiosperms.

Phytoplankton

It is a set of photosynthesizing living beings that float freely in ocean currents and are the basis of most of the food webs of marine biomes. It is made up of various species of unicellular algae, which today are classified as bacteria (cyanobacteria) or as protists (diatoms with more than 20,000 species).

Mangroves and seagrass beds

This biome includes 12 genera that contain about 60 species of salt-tolerant trees, in addition there are several species of seagrass. These species of grasses belong to the group of monocotyledonous angiosperms, such as Zostera marina and Thalassia testudinum.

Macroalgae forests

There are numerous species of macroalgae or giant algae that make up these underwater forests. Among them the most common belong to brown algae, but there are also red and green algae.

Macroalgae forest. Source: FASTILY / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

The most abundant are the brown algae included in the Sargasso group of the genera Sargassum, Macrocystis, Nereocystis, Lessonia and Durvillea.

Algae in corals

Red, pink and purple patches of red, pink and purple are observed on coral reefs that are caused by encrusting red algae or coralline algae. They belong to the order Corallinales and have a calcareous hard stem or foot.

Fauna

The fauna that inhabits marine biomes is very diverse, ranging from microscopic organisms such as zooplankton to the largest animal on Earth such as the blue whale.

Zooplankton

It is part of the base of marine food webs and is made up of numerous species of protists and larvae of larger animals. All species of zooplankton feed by ingestion of organic matter.

Mangroves and seagrass beds

Both crabs and manatees (Trichechus spp.) And sea turtles inhabit here permanently or in passing.

Saltwater crocodiles are found in the mangroves and even in the open ocean coast biome. Such is the case of the marine crocodile (Crocodylus porosus), the largest in the world, and the American or Tumbes crocodile (Crocodylus acutus).

Macroalgae forests

Anemones such as Corynactis carnea and clams such as Gaimardia trapecina inhabit the seabed of these kelp forests. In addition, numerous species of fish that transit and feed in these areas as well as sea lions, seals and elephant seals.

Coral reefs

This biome has great biological diversity, with numerous species of fish such as the parrotfish (Scaridae family) and the moray eel (murénidae). Other examples are surgeonfish (family Acanthuridae), trumpetfish (Aulostomus strigosus), clownfish (Amphiprion ocellaris), and seahorses (genus Hippocampus).

Tropical seas

In all the seas of the world there is a great diversity of animal life, in the case of tropical seas, for example, yellowfin tuna (Thunnus albacares) and black merlin (Istiompax indica).

Whale shark (Rhincodon typus). Source: Abe Khao Lak / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

Likewise, there is the whale shark (Rhincodon typus), which reaches up to 12 m in length and feeds on plankton. Another species is the black-winged manta ray (Manta birostris), which reaches up to 6 meters from end to end of its lateral fins.

Temperate seas

There are various species of fish, such as monkfish (Lophius piscatorius) and European hake (Merluccius merluccius). As well as marine mammals such as the Mediterranean monk seal (Monachus monachus).

Various species of sharks also inhabit these seas, such as the blue shark (Prionace glauca) and the basking shark (Cetorhinus maximus).

Cold seas

Towards the North Pole there are various species of marine mammals such as seals, walruses, narwhals, whales and killer whales. In addition, it is the habitat of the polar bear that, although it is not an aquatic animal, is adapted to dive and fish in these waters.

There are also species adapted to these extremely cold waters, such as the Arctic cod (Boreogadus saida). Another species of interest is the boreal shark (Somniosus microcephalus) that lives at 2000 m depth, is blind and can live up to 400 years.

Hydrothermal fumaroles

Little-studied species such as tube worms (Riftia pachyptila) and blind shrimp live here, with phototrophic bacteria and chemosynthetic archaea at the base of the food chain.

Marine biomes of Mexico

The coasts of Mexico are bathed by tropical and subtropical waters both from the Atlantic Ocean on its eastern coast, and from the Pacific on the west.

Coasts of Mexico. Source: isaacpanoramio / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

The marine biomes represented with ecosystems in Mexico include the warm sea with the Caribbean and the temperate one with the Gulf of Mexico and the Gulf of California. All these biomes harbor a great biological diversity, only in marine mammals about 42 species are located and in fish more than 1,500 species.

Coral reefs

In the Gulf of Mexico from the Campeche region there are coral reefs that continue with the Yucatan coral reef. All of this is part of the Mesoamerican-Caribbean coral reef, which is the second largest in the world.

500 species of fish, 350 species of mollusks and 65 species of coral inhabit these reefs. In addition, there are deep and cold water corals in the Gulf of Mexico, made up of species such as Lophelia pertusa and Madrepora oculata.

Macroalgae forests

Macroalgae forests are found in Mexican marine waters, the largest of which are in the Pacific on the shores of the Baja California peninsula. There are abundant brown algae (Phylum Heterokontophyta), red algae (Phylum Rhodophyta) and green (Division Chlorophyta).

In the waters of the Atlantic we find this biome represented by smaller forests in the Gulf of Mexico and in the Mexican Caribbean.

Mangroves and seagrass beds

Sea meadows. Source: Alberto: //www.romeofotosub.it / CC BY-SA (https://creativecommons.org/licenses/by-sa/2.5)

This biome occupies some 750,000 hectares in Mexico, both on the Pacific and Atlantic coasts, with four species of mangroves. While the seagrass meadows include about 9 species of grasses from the monocot group.

Underwater hydrothermal fumaroles

Off the coast of the Mexican Pacific there are underwater hydrothermal vents corresponding to the eastern Pacific ridge.

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