A biome, bioclimatic landscape or biotic area is a set of ecosystems that share environmental conditions that condition similar adaptations in flora and fauna, that is, they are climatically and geographically defined areas that share similar ecological conditions.
Unlike other biogeological divisions, within a biome there do not have to be genetic or taxonomic ties; The biome is defined by similarities in climate, life forms, and large-scale environmental features, often related to latitude, altitude, or depth, so the same biome can encompass large geographic areas, even separate areas on different continents.
These conditions influence the evolutionary development of living organisms that inhabit a given biome, so that different organisms develop similar adaptive characteristics.
For example, tropical forests are a type of terrestrial biome. In all of them, a similar structure, soil composition and type of plants can be observed in different tropical areas of the planet, although they are inhabited by living organisms with separate evolutionary historiesIn fact, tropical forests are generally ecosystems with a high amount of endemism.
Biomes are generally divided into two major groups, terrestrial biomes and aquatic biomes. In the WWF classification of main habitat types, equivalent to biomes, terrestrial biomes are further divided into terrestrial and freshwater biomes.
The dense rainforest, savannah, steppe, temperate forests or tundra are some of the most outstanding terrestrial biomes.
Among the large aquatic biomes, the marine biome stands out, which is not only the largest aquatic biome, but also the largest biome of all in terms of extension since it occupies 3/4 parts of the Earth’s surface.
Types of marine biomes
Within the marine biome, different ecozones and different types of habitat. The WWF divides the marine biome into two major groups:
One of the characteristics that most strongly shape marine biomes is the amount of sunlight that reaches them as a function of depth. Based on this, three large vertical zones are usually distinguished:euphotic zone: It is the upper layer of the oceans where sunlight reaches with relative abundance. dysphotic area: sunlight arrives weakly, can be compared to twilight on land. aphotic zone: is the deepest area that is not reached by light. In addition to being dark, they are usually cold waters with few nutrients. Approximately 80% of the ocean water mass is located in the aphotic zone.
As for the types of habitats, four zones are generally distinguished; the intertidal, demersal, pelagic, benthic and abyssal zones.
Intertidal and demersal zone
The intertidal zone is the area where seawater and land meet. It is the most superficial zone of the oceans and they are also usually the most temperate. The intertidal zone covers a range of variable depth and is not always submerged due to the tides, which means that communities of living beings are often subject to continuous changes.
Inside rocky shores you can see a very light layers. In the high part, where the tides arrive less frequently, there are fewer established species, usually limited to a few species of algae and molluscs. In the intermediate strata that stay submerged longer, there is a greater variety of algae and small invertebrate animals, such as crabs, snails and starfish, and numerous fish, usually small, can be found.
The intertidal zone on the shores of the beach is covered with sand that is constantly renewed by the tides; this lack of a surrounding substrate makes algae rare. Among the characteristic animals of the beach we can mention clams, predatory crustaceans and many shorebirds.
Following the intertidal zone, we find the so-called demersal zone, which encompasses the bodies of water close to the coastline and which are strongly affected by benthos (benthic zone) and marine soils. Larger fish species can be found in the demersal zone than in the intertidal zone, eg reef rays.
The pelagic zone, often referred to as the open ocean, comprises bodies of water farther from land than not located on the continental shelf. The temperature in the pelagic zone is generally cooler than in the intertidal zone, although currents produce a constant mixture of cold and warm waters.
the plankton in the pelagic zone is very abundant and therefore you can see larger fish and some marine mammals such as whales and dolphins. In addition, photosynthetic plankton that live in the sea make a very important contribution to the production of atmospheric oxygen.
The most superficial zone of the pelagic zone, known like epipelagic or simply piélago, reaches up to 200 m of depth. This is followed by the mesopelagic zone that reaches up to 1000 my, to which very little light reaches.
From 1,000 to 4,000 m deep is what is known as the mesopelagic zone, or bathyal zone, which is the first aphotic zone with almost total darkness, except for bioluminescence phenomena in some animals. Here there are no more live algae and most organisms survive on substances that fall from higher levels or as predators of other animals.
GalleryPelagic zones in the marine biome
The abyssal zones are the deepest areas of the oceans, from 4000 m to the bottom of the sea. Also called abyssopelagic zone. The abyssal zone reaches the terrestrial tectonic plates and the most abundant life forms are some bacteria and some fungi, although there is also a characteristic and scarce abyssal fauna, such as Melanocetus johnsonii.
Approximately below 6000 m is hadal zone, name derived from Hades, the underworld of Greek mythology. The deepest hadal zones are in ocean trenches, some of which are more than 10,000 m deep, such as the Mariana trenches that reach 11,033 m. Some species of molluscs were found in the hadal zone.