The transitional environments or transition ecosystems are those that arise in the border zone between two clearly defined and contrasting environments. This generally occurs between very different environments such as air-ground and aquatic environments, but also between different contrasting aquatic or terrestrial environments..
The characteristics of these transitional environments are usually a combination of the interacting environments. They are emergent properties, that is, they arise as a result of the interaction of neighboring environments, but they are different from those manifested by said environments..
In general, transition environments have less stable abiotic conditions than regular environments and faster rates of change. On the other hand, there are species typical of the environments that interact in the area and others typical of the transitional environment..
Transitional environments are classified as natural and induced or artificial (caused by human action). Examples of transitional environments are the coastal zone and the margins of rivers, lagoons, ponds and other wetlands such as mangroves..
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Transition environments are generated in ecotones (zones of tension due to the interaction of two contrasting stable ecosystems). In these environments the energy exchange is maximum due to the fact that different food webs are crossed and new possibilities are opened to different elements of the food chain.
The greater flow of energy facilitates the increase in the number of species and the size of the populations, that is, the number of individuals. On the other hand, the tensions between the interacting environments make an unstable condition emerge.
For example, on the sea coast the areas alternately go from emerged to submerged and oxygen comes from the air or water in each condition.On the banks of rivers, floods and overflows also cause constant changes in the transition area..
Plants and animals that colonize such transitional environments must adapt to withstand such dynamics..
Transitional environments arise naturally in the fringes of interaction between natural environments, but also the product of human action. In the first case, the sea coast or the shore or plain of a river are clear examples, as well as a mangrove or a delta..
However, human actions transforming the natural environment also create transitional environments, then called induced or artificial..
Such is the case of a dam or reservoir, irrigation canals and even cultivated areas, since their crop margins are transitional environments with the natural environment. There are some plants and animals adapted to the best conditions provided by the crop and thousands of years of agricultural activity has given rise to pests..
Then, within the natural transition environments, the most outstanding are those between very contrasting environments. For example, between air-ground and aquatic environments, where living beings adapted to each condition and species adapted to the transition environment coexist.
The same occurs between the aquatic environment and the terrestrial sub-crust, as is the case of the interaction between the ocean and geothermal sources (fumaroles). In this case, a highly productive ecosystem is produced in the middle of an underwater desert..
On the other hand, there are less obvious transitional environments, such as those generated in the ecotone between forest and grassland. As well as between the tundra and the taiga, and many other ecosystems with more or less delimited borders.
The flora in transitional environments varies according to the particular environment and can sometimes be scarce. For example, the vegetation in the beach marine littoral is limited to species of saline sandy environments as well as lichens on rocks and submerged seaweed and algae..
Among the coastal plants is the batatilla (Ipomoea pes-caprae), a creeping of the convolvulaceae and the grass called saladillo (Sporobolus virginicus). While among the submerged sea grasses are the species of the genera Thalassia, Posidonia, Zostera and others.
Turtle grass (Thalassia testudinum) is a common species in the Caribbean, named for serving as food for sea turtles. While Posidonia oceanica it is endemic to the Mediterranean Sea.
On the other hand, in the mangroves there are species adapted to the transitional environment itself, they are called mangroves. They are trees with anatomical and physiological adaptations to withstand conditions of extreme salinity and lack of oxygen such as the red mangrove (Rhizophora mangle) and the black mangrove (Avicennia germinans).
In transitional environments on the shores of freshwater bodies, the vegetation is much denser and more diverse. It covers a whole gradation of adaptations that includes marsh and aquatic plants, both floating, energetic and submerged..
Here the plants furthest from the shore endure periodic floods, while the marshy plants are found in flooded areas. Among the marshlands are species such as reeds (Juncus spp.), the reed (Phragmites australis) and papyrus (Cyperus papyrus).
While among the floating ones that are located in the transition between water and air, there is the Victoria regia (Victoria amazonica). Water cabbagePistia stratiotes) and water hyacinth (Eichhornia crassipes).
Animals adapted to transitional environments are as diverse as such environments exist. The most relevant are aquatic mammals, which evolved to return from the terrestrial to the marine environment.
This includes cetaceans (whales, dolphins, porpoises) that live in the sea, but require air to breathe. Like the sirenids (manatees and dugongs) that inhabit rivers, deltas and mangroves.
Another group of interest is the pinnipeds (true seals, otariums and walruses), which live in the transitional environment of the marine littoral. For example, the harbor seal (Phoca vitulina), Galapagos fur seal (Arctocephalus galapagoensis) and the walrus (Odobenus rosmarus).
Sea turtles also enter the transitional environment for their reproduction, such as the green turtle (Chelonia mydas).
In transitional environments between land and fresh water, animals such as the capybara are found (Hydrochoerus hydrochaeris). Similarly, various species of alligators (alligator spp. Y Melanosuchus niger) and crocodiles (Crocodylus spp.).
There are also both saltwater otters (Enhydra lutris) like sweet (Pteronura brasiliensis), like the beaver (Beaver spp.) in temperate zone rivers. In the Galapagos Islands there is the marine iguana (Amblyrhynchus cristatus), occupying the transition between the sea and the rocky coast.
This environment constitutes a transition between the air-ground environment and the marine environment, forming a gradation from the land inland to the coastal bottom. The tree species that make up the mangrove have adapted to the different levels of presence of water and salt.
In such a way that the button mangrove (Conocarpus erectus) grows inland, while other species go out to sea, such as the red mangrove and the black mangrove. In addition, this ecosystem is generally associated with the presence of underwater pasture meadows, such as turtle grass..
This is a complex transitional environment that includes diverse species of crustaceans, mollusks, fish, and mammals. In this environment they have abundant sunlight and water, but they must adapt to the alternating periods of rise and fall in the water level..
Like the onslaught of the waves, some organisms develop forms of attachment to the rocks. While others such as bivalves bury themselves in the sand waiting for the next wave or rise of the tide.
This transitional environment combines the interaction of 4 different environments, terrestrial, aerial, freshwater and marine. Here are species of freshwater fish, others of salt water and those adapted to brackish water.
Likewise, different species of plants adapted to different humidity and salinity conditions. The changing nature of transitional environments is also manifested, with phenomena such as seasickness..
Maceration occurs in large deltas such as the Amazon and Orinoco rivers and consists of large waves of up to 4 m that periodically penetrate deep into the river advancing. These waves are the product of the interactions between the tidal forces and the current of the river.
It is a transition between the freshwater environment and the air-ground environment, due to the periodic flooding of the jungle. These jungles are of two types, of black water rivers (igapó) like the Negro river and white water rivers (várzea) like the Amazon.
Each one with its particularities due to the physicochemical characteristics of the waters and both plant and animal species adapted to these conditions develop. Perhaps the most representative example of the transitional character of this environment is the arapaima fish (Arapaima gigas) 3 m long and 250 Kg.
This fish swims among the roots of large trees in the Amazon understory during the period when the rivers overflow. It even feeds on insects and birds perched on the branches, which it catches by jumping over the water..
Similarly, in high areas of the Amazon plain, when the water level drops a lot, it survives buried in the mud, sticking its head out. In fact, it breathes both through gills and sucking in air through its mouth..
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