Mesophotic coral reef
[2][3][4] Many species of fish and corals are endemic to the MCEs making these ecosystems a crucial component in maintaining global diversity.
[1] Mesophotic coral reefs also serve as a transition zone between shallow and deep-sea environments which creates a specialized and unique biodiversity for the MCEs.
[5] Basic information on the taxonomic composition, depth range, habitat preferences, and abundance and distribution of the mesophotic coral ecosystem is limited.
MCE studies reveal that there are various habitats and communities of corals, sponges and fishes, which are significantly different from their shallow-water counterparts.
Other unique species that were only found in mesophotic coral reefs are Symbiodinium, Brachyuran crabs, Porites astreoides, Acropora tenella.
[14][15] Due to recent anthropogenic impacts, it was thought that the MCEs are less affected by human development and climate change, and could be used as a source for reseeding shallow water coral species.
[5] They prefer cold water environments, making them crucial inhabitants of the lower mesophotic coral reefs.
[1] They become white due to loss of the zooxanthellae and photosynthetic pigments which causes them to be under extreme amounts of stress and exposes them to high mortality rates.
[5] Internal waves can induce fluctuations of the thermocline causing temperature in mesophotic coral reefs to vary from 10 to 20 °C.
[1] Research on these coral reefs remain currently highly biased on location and region while not representing oceans globally.
[11] Other conducted studies in the following years found that Caribbean MCE's also possesses similar geomorphology and specie distribution as Goreau's discovery in 1973.
These impacts include hurricanes, thermal stress, pollution, sedimentation, and eutrophication resulting in significant mortality rates for all coral species.
These ecosystem services include: habitat economically and ecologically for important species, potential for tourism and recovery to shallow population, discovery new essential substances and coastal protection.
In Pulley Ridge, Red snappers building their nest at 60–80 m depth and it provide larvae to shallow reefs, such as Florida Keys.
Each mesophotic coral ecosystem are shaped by transgression and regression of sea levels during glacial and interglacial periods creating a unique environment.
[5] The substrate, the amount of nutrients coming from runoff, the attenuation of light, and the rates of sedimentation all influence the geomorphology of mesophotic coral reefs determining what communities are found in that specific location.
[5] MCEs are located generally on fore-reef slopes adjacent to shallow-water coral reefs, deep-water rhodolith beds, and on isolated offshore banks on the continental shelf.
Furthermore, it is thought that by virtue of their depth and their remote offshore location, mesophotic reefs have better protection from direct human impact such as nutrient run-off and overfishing.
However, more recent research done in 2016 proved that coral reefs situated in the path of hurricane Matthew (both shallow and mesophotic) suffered destruction.
In addition bottom landings gear usage can cause physical damage to the reefs and stir up sediment that smother and kill coral.
[22] For MCEs that are exposed to the UML during warm water temperature periods, their fate may be linked directly to shallow-water reefs.
In addition recent evidence has demonstrated that scleractinian corals at mesophotic depths are susceptible to thermal stress and bleaching in the same manner as that experienced by shallow-water reefs.
[3] MCEs are generally light-limited systems [23] and, thus, may be extremely vulnerable to reductions in light as a consequence of increased turbidity or rising sea level.
[3] Organisms can be removed by fishing for consumption, collection for the aquarium, medicinal, and curio trade, and inadvertent loss or out-migration from other activities or factors, such as introductions of predators and incidence of disease.
Invasive species that are introduced to a novel biogeographic range or are native but released by ecological forces have been demonstrated to act as a disturbance in MCEs.
For example, algae of the genus Ramicrusta (Peyssonneliaceae) have recently appeared in the Caribbean where they were absent or rare and have become successful space competitors.
The algae are able to overtop edges of living stony corals and other benthic organisms, causing death of underlying tissue.
This makes it difficult for conservation efforts to be conducted as they are out of human reach and a vast majority of MCEs remain undiscovered or unsurveyed.
