Elkhorn coral rely on their excreted coral bodies to retract into and hide from predators. These predators include many species of damselfish (Pomacentridae), which suck and pluck the coral polyps out of the coral body. Fireworms (such as Hermodice carunculata) and corallivorous snail species in the family Coralliophilidae range over the coral colony grazing on polyps.
Known Predators:
Elkhorn coral maintains a relatively large coral body. Elkhorn coral was named after its branching pattern, which is remnant of an elk’s antlers. These antler-like branches are sturdy and thick. The color of the coral, due to the symbiotic zooanthellae, ranges from yellow to a yellowish-brown.
Average length: .75 m.
Sexual Dimorphism: sexes alike
Other Physical Features: ectothermic ; radial symmetry
Elkhorn coral reaches its maximum size at 10 to 12 years old. Elkhorn coral’s branches can increase in length as fast as 2-4 inches per year. While a colony can persist for centuries, individual coral polyps usually live for 2 to 3 years.
Elkhorn coral is found in shallow water, generally ranging from 1 to 5 meters deep. Elkhorn coral is a tropical species and inhabits waters with a temperature range of 66 tol 86 degrees F. This coral tolerates salinities within the normal range of 33 to 37 parts per thousand. Elkhorn coral often establishes in heavy surf close to shore, where the preferential exposed reef crests create an optimal habitat.
Range depth: 1 to 20 m.
Average depth: 3.5 m.
Habitat Regions: tropical ; saltwater or marine
Aquatic Biomes: reef ; coastal
Other Habitat Features: intertidal or littoral
Elkhorn coral is present in coral reefs from southern Florida southward to the northern coasts of Venezuela. The coral has native populations throughout this range, most notably in the Bahamas and the Caribbean.
Biogeographic Regions: atlantic ocean (Native )
Elkhorn coral get much of their food energy from the algae symbionts that live in their tissues. The polyps provide the algae protection, suitable habitat, and waste products that the algae use as nutrients In return, the zooxanthellae produce surplus sugars that the polyps use as food. Elkhorn coral polyps also use their tentacles to capture small particles of detritus and also small organisms, including phytoplankton, microbes, and small zooplankton.
Animal Foods: zooplankton
Plant Foods: sap or other plant fluids; phytoplankton
Other Foods: detritus ; microbes
Primary Diet: herbivore (Eats sap or other plant foods); planktivore
Elkhorn coral is a major component of many reef ecosystems. Its physical structure provides essential refuges for reef animals, both young and adult, as well as food for many species.
Ecosystem Impact: creates habitat
Mutualist Species:
The presence of elkhorn coral has several major economic implications for humans. Ecotourism in the Caribbean relies on healthy reefs, with not only healthy coral, but a healthy ecosystem full of interesting things to see such as fish and other marine animals. The pet trade, in the form of troical reef fish, is supported by healthy coral popualtions which house juvenille reef fish. Elkhorn coral also builds many reefs that are researched extensively, such as those in the Florida keys and the Caribbean.
Positive Impacts: pet trade ; ecotourism ; research and education
Elkhorn coral offers no direct economic negativities, although is does offer a reflection of negative humans impacts. The destruction of coral reefs due to rising ocean temperatures and an runoff is causing severe economic damage in ecotourism and coastal fisheries. The anthropogenic effects on Elkhorn coral will lead to negative economic implications.
In elkhorn coral, eggs and sperm are released into the water column and fertilization occurs near the surface. After about 78 hours, larvae of planula develop cilia, giving them the appearance of “fuzzy balls.” Motility is observed at this stage. Larvae remain in surface waters during their early development aided by high lipid content. The coral larvae live in the plankton for 3 to 5 days until finding a suitable area to settle. Few larvae actually survive. Those that do, metamorphose into the polyp stage. These polyps then contribute to the development of a new colony.
Development - Life Cycle: metamorphosis ; colonial growth
Populations of elkhorn coral have declined drastically since the 1980's. Estimates are in the range of 90-95% reduction in abundance since 1980 in areas where loss has been quantified. Reductions of 75-90% were observed in some areas such as the Florida keys in 1998 due to bleaching and hurricane damage. The species is listed as Threatened under the U.S. Endangered Species Act, and Critically Endangered by the IUCN. Like all stony corals (Scleractinia) it is listed in Appendix II of CITES, so international trade is somewhat limited.
US Federal List: threatened
CITES: appendix iii
State of Michigan List: no special status
IUCN Red List of Threatened Species: critically endangered
Although elkhorn coral polyps do not communicate with other polyps directly, they do exhibit some behaviors indicating some sort of perceptive response. For example, the release of gametes for breeding occurs with all polyps at the same time per breeding season. On a full moon in August or September, the polyps will release gametes; this is an indication of perception of light (length of day), temperature, and nightime light from the moon. The polyps also exhibit a form of tactile response in that they react to touch and release venomous nematocytes.
Perception Channels: visual ; tactile
A majority of elkhorn coral reproduction involves asexual reproduction. Branches of the coral can break off and attach to substrate. The coral animals within the branch can then colonize the new area and begin a new colony.
Elkhorn coral also reproduce sexually. Each colony contains both male and female structures, and is simultaneously hermaphroditic. Millions of male and female gametes are released into the water at the same time (usually synchronized with other adjacent colonies). This sexual reproduction occurs once a year, usually in August or September on a full moon. The coral larva, or planula, will float in the water column as plankton for several days until they land on suitable substrate. The planula then metamorphose into colonial polyps. Thus, a new colony is started.
Breeding interval: Elkhorn coral spawn once a year.
Breeding season: August to September
Key Reproductive Features: iteroparous ; seasonal breeding ; simultaneous hermaphrodite; sexual ; asexual ; fertilization (External ); broadcast (group) spawning; oviparous
Elkhorn coral exhibit no parental care.
Parental Investment: no parental involvement
"Elkhorn coral, like many corals, receive most of their energy and oxygen from symbiotic organisms called zooxanthellae." (NOAA Fisheries OPR)
"Elkhorn coral is found on coral reefs in southern Florida, the Bahamas, and throughout the Caribbean. Its northern limit is Biscayne National Park, Florida, and it extends south to Venezuela; it is not found in Bermuda. Once found in continuous stands that extended along the front side of most coral reefs, the characteristic "Acropora palmata zone" supported a diverse assemblage of other invertebrates and fish. These zones have been largely transformed into rubble fields with few, isolated living colonies." (NOAA Fisheries OPR)
"Over the last 10,000 years, elkhorn coral has been one of the three most important Caribbean corals contributing to reef growth and development and providing essential fish habitat." (NOAA Fisheries OPR)
"Elkhorn coral was formerly the dominant species in shallow water (3 ft-16 ft (1-5 m) deep) throughout the Caribbean and on the Florida Reef Tract, forming extensive, densely aggregated thickets (stands) in areas of heavy surf. Coral colonies prefer exposed reef crest and fore reef environments in depths of less than 20 feet (6 m), although isolated corals may occur to 65 feet (20 m)." (NOAA Fisheries OPR)
"NMFS finalized the ESA listing of elkhorn and staghorn coral on May 4, 2006 (71 FR 26852). NMFS designated critical habitat for elkhorn and staghorn corals in November 2008." (NOAA Fisheries OPR)
"Like counting rings in the trunk of a tree, the age of corals can be determined by examining coral growth rings." (NOAA Fisheries OPR)
"Florida Keys National Marine Sanctuary (FKNMS), the largest coral reef management entity in the region, has developed a management plan for the Sanctuary's corals that includes protective activities, such as zoning, channel markings, and restoration efforts.
Restoration activities have included efforts to re-attach Acropora fragments generated by ship groundings and hurricane events; these efforts have had mixed success. Similar efforts to re-attach coral fragments have also been made in Puerto Rico and the U.S. Virgin Islands.
Other restoration efforts have included attempts to culture and settle coral larvae with very limited success. New techniques for restoring Acropora are currently being pursued. Such new techniques involve enhancing sexual recruitment, reestablishing ecological roles within reef systems (e.g. herbivorous urchins), and other methods for controlling predators and disease.
In 1998, the United States Coral Reef Task Force was established by Presidential Executive Order 13089 to coordinate and strengthen efforts for protecting coral reef ecosystems. The Task Force is co-chaired by the Departments of Commerce and Interior, and includes leaders of 12 federal agencies, seven U.S. states and territories, and three freely associated states. In 2002, the Task Force adopted a resolution calling for the development of Local Action Strategies, which are locally-driven plans for collaborative and cooperative action among federal, state, territory, and non-governmental partners to reduce key threats on valuable coral reef resources. Three Local Action Strategies have been developed within the range of elkhorn coral for Florida, Puerto Rico, and the U.S. Virgin Islands. These strategies are underway and will be implemented over a three-year period (FY2005-2007)."
"The coral larvae (planula) live in the plankton for several days until finding a suitable area to settle, but very few larvae survive to settle and metamorphose into new colonies. The preponderance of asexual reproduction in this species raises the possibility that genetic diversity may be very low in the remnant populations." (NOAA Fisheries OPR)
"The dominant mode of reproduction for elkhorn coral is asexual fragmentation; this life history trait allows rapid population recovery from physical disturbances such as storms. However, this mode of reproduction makes recovery from disease or bleaching episodes (in which entire colonies or even entire stands are killed) very difficult. The large role of asexual reproduction for this species increases the likelihood that genetic diversity in the remnant populations may be very low. Scientists are becoming increasingly concerned for this species based on its demographic paramaters; specifically, how species recruitment and genetic diversity affect recovery potential." (NOAA Fisheries OPR)
Die Elchgeweihkoralle (Acropora palmata) ist eine Steinkoralle (Scleractinia). Sie ist eine von nur drei Acropora-Arten aus der Karibik, den Küsten von Florida bis Venezuelas, wo sie oft die oberen, stark durch Wellen bewegten Bereiche der Korallenriffe dominieren. Den deutschen Trivialnamen erhielt sie aufgrund ihrer großen, schaufelartigen Äste.
Die Äste dieser Korallenart erreichen Durchmesser von über zehn Zentimeter. In großen, monospezifischen Beständen wachsen die Enden der Äste oft zusammen, so dass sie ein Dach in ein bis zwei Meter Höhe über dem Substrat bilden. Das sich darunter befindende Labyrinth aus Korallenästen dient vielen Fischen und anderen Tieren als Versteck. Im Lauf der Zeit werden die Lücken dann mit Sediment gefüllt. So entstanden auch Kalksteinschichten auf den Florida Keys die 125.000 Jahre alt sind.
In der Riffaquaristik spielt sie keine Rolle. Acropora palmata wird nicht importiert.
White pox disease[1]
Wissenschaftler haben nunmehr nachgewiesen, dass die Bakterienart Serratia marcescens bei der Acropora palmata die sogenannte White pox Krankheit[2] auslöst. Gentests und Laborversuche ergaben, dass dieser für Korallen tödliche Keim nicht von anderen Tieren stammt, sondern aus Abwässern des Menschen.[3]
Die Elchgeweihkoralle (Acropora palmata) ist eine Steinkoralle (Scleractinia). Sie ist eine von nur drei Acropora-Arten aus der Karibik, den Küsten von Florida bis Venezuelas, wo sie oft die oberen, stark durch Wellen bewegten Bereiche der Korallenriffe dominieren. Den deutschen Trivialnamen erhielt sie aufgrund ihrer großen, schaufelartigen Äste.
Elkhorn coral (Acropora palmata) is an important reef-building coral in the Caribbean. The species has a complex structure with many branches which resemble that of elk antlers; hence, the common name. The branching structure creates habitat and shelter for many other reef species. Elkhorn coral is known to grow quickly with an average growth rate of 5 to 10 cm (2.0 to 3.9 in) per year. They can reproduce both sexually and asexually, though asexual reproduction is much more common and occurs through a process called fragmentation.
Although Elkhorn coral dominated the Caribbean in the early 1980s, the species has since dramatically declined in numbers. Scientists have estimated that between 1980 and 2006, when it was listed in the Endangered Species Act (ESA), the population declined by around 97%. This decline was due to a variety of factors, including disease, algae growth, climate change, ocean acidification, and human activity. In May 2006, Elkhorn coral was officially listed as threatened in the ESA along with another species in the Acropora genus, staghorn coral. Some conservation efforts are now in place to protect the species and promote increased genetic variability among the species.
Elkhorn coral produce hard antler-like structures composed of calcium carbonate. These structures can be over 2 (> 6 ft.) meters high and 13 meters (43 ft) wide and are a dull, brownish-yellow.[3]
Elkhorn coral's primary source of nutrients comes from photosynthetic algae, zooxanthellae, that live inside the coral's cells.[4] Therefore, Elkhorn coral are highly dependent on the sunlight for sustenance, leaving Elkhorn coral vulnerable to increased turbidity or water clarity. During bleaching events, or long-term periods of increased turbidity, Elkhorn coral can obtain nourishment from alternative food sources through filter feeding.[5]
As mentioned, Elkhorn coral have special algae living in their tissues known as zooxanthellae. Zoothanthellae meet their nutritional requirements using photosynthesis, a process that converts carbon dioxide and water into sugars and oxygen. Elkhorn coral provide habitat for these algae and, in turn, receive an abundant source of oxygen, enabling them to grow quickly.[3]
Elkhorn coral can also use filter feeding techniques to obtain food. At night, Elkhorn coral use their tentacles to snatch free-swimming zooplankton from the water. Zooplankton complete daily diel migrations. In the morning, zooplankton sink to the depths of the ocean where predators are scarce, and then come nightfall, they rise back towards the surface. By concentrating their predation activities at night, Elkhorn coral expend less energy catching large amounts of prey.[3] However, because filter feeding is more energy intensive than relying on zooxanthellae, Elkhorn coral will only resort to this feeding method when water conditions are poor and block out sunlight.[6]
Elkhorn coral live in shallow habitats, which give them abundant access to light. Like all animals, Elkhorn coral requires oxygen to survive, most of which they obtain through special, photosynthetic algae living in their tissues called zooxanthellae. Therefore, in order to help zooxanthellae produce as much oxygen as possible, Elkhorn coral live in shallow regions between 1 and 5 meters deep to ensure that abundant light reaches the zooxanthellae, maximizing photosynthesis.[3][6]
These corals are found in clear, shallow water throughout the Bahamas, Florida, the Caribbean, and beyond to the northern shores of Venezuela.[4] The most northern region occupied by Elkhorn coral is off the coast of Broward County, Florida.[7] Characteristically found in shallow, turbulent water ranging from 1 to 5 meters, Elkhorn coral thrive best in high-energy zones where wave action is frequent. This success is because wave action increases fragmentation, which allows more new colonies to form.[4]
Due to fragmentation and rapid growth rates, Elkhorn coral were the primary foundation in the development of the Caribbean coral reefs. Over the last 5,000 years, Elkhorn coral, Staghorn coral, and Star coral comprised the southeastern reefs.[5] Research has shown that the Elkhorn coral evolved during the Mid-Pliocene epoch, 5.2-2.58 million years ago.[8] The unstable climate during this period allowed Elkhorn coral to thrive during glacial and interglacial events. During glacial events, sea levels rise and cause an increase in wave energy. As previously mentioned, Elkhorn coral does best in environments that are shallow and experience high energy changes, which aid in the reproductive process.[8]
Through their ecosystem services, Elkhorn coral increase the commercial value of coral reefs.
Like the foundation of a house, Elkhorn coral support coral reef communities. Their interwoven lattice-like branches create a variety of habitats varying in topography, which in turn, support diverse fish populations.[9] These habitats support fish nurseries and protect fish from predators, increasing reef diversity.[6] This elevated diversity makes the reefs more appealing to tourists, thereby increasing their economic value.
Elkhorn coral provide insulation from storms to beaches and reefs. Their thick branches absorb the energy of storm waves, in turn, dissipating the force that crashes into beach shorelines.[10] With less force, beachfront properties experience less damage, reducing the financial demand needed to restore the homes and livelihoods of many.
Elkhorn coral colonies live for centuries. These colonies grow 5-10 cm (2-4 inches) each year, reaching maximum size in 10 to 12 years.[7] Healthy Elkhorn coral can grow up to 13 cm (5 inches) in branch length a year, making them one of the fastest growing coral species. Elkhorn coral can span a diameter of 4 m (12 feet) wide and 2 m(6 feet) tall.[4] Under stressful conditions, Elkhorn coral colonies and fragment growth slow down substantially. For example, the Fortuna Reefer Vessel grounding site showed no measurable growth over the last ten years due to stress.[4] Elkhorn coral create thick, interlocking groups known as thickets. Thickets provide shelter to other marine life such as fish, crustaceans, and marine invertebrates, and consist of many identical polyps that have grown together.[4] These dense groups provide protection to shorelines against large waves and storms.
The Elkhorn coral is a simultaneous hermaphrodite, meaning that in each coral colony both egg and sperm are produced.[4] Despite this, self-fertilization usually does not occur. In order for successful fertilization to take place, two genetically distinct parents are needed. Successful reproduction rates are low in Elkhorn coral which limit the growth of new colonies. The probability of successful reproduction rates are low in Elkhorn coral because only about 50% of Elkhorn corals are genetically unique individuals.[11] The Elkhorn coral reproduction cycle occurs once per year, after a full moon in the late summer, during the months of either July, August, or September. The gametes are released for only a few nights by broadcast spawning eggs and sperm into a water column. Once fertilized, the eggs develop into larvae that settle on hard surfaces and begin the growth of a new colony.[5]
Most commonly, Elkhorn coral reproduce asexually, their most common type of reproduction. During storms, strong waves, or ship disturbances, fragments of coral break off and are transported to other areas where new colonies can begin. The new colonies are genetically identical to their parent colonies, while sexual reproduction results in new genotypes. Also, as opposed to sexual reproduction, fragmentation can occur at any time of the year.[5]
Quantitative data available on the distribution and abundance of Elkhorn coral is scarce. Present locations of the Elkhorn coral include the southern coasts of Florida and the northern regions of the Gulf of Mexico.[5] Elkhorn coral are also located in the Bay Islands of Honduras.
There are four critical habitats for the Elkhorn coral that are essential to the conservation of this species. The specific regions designated and protected by the Endangered Species Act as critical habitats include regions in Florida (1,329 square miles of marine habitat), Puerto rico (3,582 square miles of marine habitat), St.John/St.Thomas (121 square miles of marine habitat), and St.Croix area (126 square miles of marine habitat).[6][12]
Elkhorn coral populations once dominated the southeastern region of the Northern hemisphere. Due to bleaching events, disease, and climate change, Elkhorn population has significantly decreased since the 1980s. In total, 80-98% of the Caribbean coral reef population has been lost. A longitudinal study done from 2005-2015 shows that the Elkhorn coral population had a proportional decline of 0.4-0.7 times in colony density across the entirety of its occupied range.[13] This decline indicates that despite conservation efforts, the population is still decreasing. Overall, there are no concrete estimates of current or historical population sizes due to technological limitations.
Several factors limit the amount of information regarding the life history of Elkhorn coral. These factors include the necessity for additional tools to assess future population changes, sexual reproduction, and environmental disturbances.[5]
In ESA listings, Elkhorn coral is listed alongside Staghorn coral, A. cervicornia, because the corals share the same genus. While recognized as two separate species in scientific literature, they inhabit similar ranges and share many of the same characteristics.[14]
Since the 1980s, Elkhorn coral populations have rapidly declined by an estimated 97%.[15] Elkhorn coral was initially recognized as a candidate for ESA listing in June of 1991, but was removed from the list of candidates in 1997 for a lack of sufficient evidence in regard to their status and threats. However, they were re-added to this list in 1999 due to concrete evidence of their population decline. In April of 2004, they were transferred from the candidate species list to the species of concern list.[14]
In 2004, the National Marine Fisheries Service (NMFS) received a petition to list the Elkhorn coral, Staghorn coral, and a hybrid species, A. prolifera, as either threatened or endangered. The NMFS determined that the petition contained substantial information and established the Atlantic Acropora Biological Review Team (BRT) to review the status of these coral species.[15] The BRT included a diverse group of experts from many different scientific fields, including coral conservationists.[14] The BRT published a status review on March 3, 2005, which summarized the relevant, published literature on these species, comments from the public, and an assessment regarding current conservation efforts.[15]
The BRT's status review concluded that the ESA should list the Elkhorn coral as a threatened species, given the importance of its ecosystem contributions and the severity of the numerous threats impacting the species. As a formerly abundant species, its high growth rate allowed it to keep up with sea level changes. The branching morphology created homes and protection for many other reef organisms. Since its decline, no other coral species has been able to fulfill these ecosystem functions. As mentioned, the species faces many threats, which include but are not limited to disease, temperature-induced bleaching, and physical damage from hurricanes. The BRT determined that Elkhorn coral was not at risk for extinction, but could become so in the foreseeable future because its population sizes were low and the severity of threats was predicted to increase.[14]
After reviewing the BRT's 2005 status report, the NMFS published a final rule on the status of Elkhorn coral on May 9, 2006. Effective June 8, 2006, the species was listed as threatened under the Endangered Species Act of 1973.[15]
In 2012, there was discussion surrounding the status of Elkhorn coral and whether it should be reclassified from threatened to endangered. The reasoning behind this proposed change was the continued population decline since the time of the ESA listing in 2006 as well as evidence of recruitment failure in several populations. The persisting population decline was potentially attributable to several increasing threats such as ocean acidification and levels of thermal stress.
However, many members of the scientific community and the public expressed disagreement with this proposed reclassification. Several comments referenced instances of increasing abundance and recovering populations with some citing population and genetic diversity statistics as well as population models. Many people argued that there had been significant advances in active restoration projects, and they feared that listing this coral as endangered would possibly disrupt and discourage the ongoing conservation efforts.
In September 2014, the NMFS published a final rule on the listing status of 65 reef-building coral species. This included a re-evaluation of the status of Elkhorn coral. The coral was kept listed as threatened due to concerns from the public that listing it as endangered might impact the ongoing restoration projects as people may see them as less worthwhile.[11]
Elkhorn coral face many global threats such as climate change, ocean acidification, and overfishing.[3]
Like other species, Elkhorn coral are threatened by climate change. Climate change refers to the general warming of earth's average temperature caused by carbon emissions. Warmer atmospheric temperatures incidentally also increase water temperature. As mentioned, Elkhorn coral have special algae called zooxanthellae, living on their tissues, which provide many benefits. However, when water temperatures warm, Elkhorn coral expel their zooxanthellae. Without their zooxanthellae, Elkhorn coral first lose their prime oxygen source, then color, and then usually die. In addition, climate change increases the severity and prevalence of storms, which can decimate Elkhorn coral populations.[3]
Elkhorn coral are also threatened by ocean acidification. Ocean acidification refers to the growing acidity of marine water caused by the increasing presence of dissolved carbon dioxide, a result of carbon emissions. The skeleton of Elkhorn coral is made of calcium carbonate. Carbon dioxide forms chemical bonds with water and, through chemical reactions, remove carbonate ions that the corals need to make calcium carbonate. With fewer carbonate ions, the coral skeletons are weaker and break easier.[3]
Like many corals, overfishing affects Elkhorn coral by reducing fish populations that feed on harmful macroalgae. Macroalgae damage Elkhorn coral by producing toxic chemicals and by decreasing the nearby available oxygen. Macroalgae can further harm Elkhorn coral by facilitating pathogen growth. Also, macroalgae reduce the amount of suitable areas where Elkhorn coral larvae attach, reducing the ability for Elkhorn reefs to recover.[16]
Local water pollution, also known as wastewater, negatively impacts Elkhorn coral by increasing the prevalence of white pox disease, the abundance of macroalgae, and by increasing water cloudiness.
Human pathogens found in untreated wastewater are especially harmful to Elkhorn coral. Serra marcescens, commonly called white pox disease, is extremely lethal and contagious.[17] The disease first causes the coral to emit a foul smelling mucus, followed by the formation of thick lesions, which then fall off, removing coral tissue. These lesions grow quickly, and can grow up to 10.5 cm2 per day, causing tissue loss of 2.5 cm2 per day.[18] This disease helped put the Elkhorn coral on the endangered species list in 2006 after a case of Serra marcescens wiped out 75% of the Caribbean corals in 2005.[17]
Untreated wastewater also contains high levels of nutrients, which increase macroalgae growth. As mentioned above, this macroalgae growth is detrimental to Elkhorn survival.[16]
Another stressor is an increase in water turbidity. This turbidity increase can result from a myriad of issues like untreated wastewater and beach erosion activities. Elkhorn coral live within very shallow regions, enabling their photosynthetic zooxanthellae to receive much light. When waters become turbid, or cloudy, access to this light is impeded. With less available light, less photosynthesis occurs, and thus zooxanthellae produce less oxygen. As stated earlier, most of the oxygen coral receive is from their zooxanthellae, so without this oxygen, Elkhorn coral can quickly suffocate and die.[19]
All of these stressors independently weaken corals. Collectively they reduce the chance that corals have of surviving any single stressor.
Prior to the ESA listing in 2006, there were no regulatory mechanisms in place to protect Elkhorn coral. Some documentation with regulations existed; however, no documents specifically mentioned by name the Elkhorn coral or any other Acropora corals.
Most of the existing regulation was intended to protect corals against physical impacts incurred through fishing gear, anchoring, and vessel grounding. Florida law protects Scleractinia corals as well as Milleporina corals from collection, commercial exploitation, and direct physical damage. Puerto Rico also established similar laws protecting corals and encouraging conservation. In 2001, the National Park Service established two national monuments – the Virgin Islands Coral Reef and the Buck Island Reef National Monument. The creation of these two monuments established thousands of acres of non-extractive zones.[15]
While the United States had some policy in place before the listing, many other nations did not. Given that the range of the Elkhorn coral extends along the coasts of several different countries, the inconsistency in policy presented an issue. The official listing of Elkhorn coral allowed for the establishment of more specific protection.
The NMFS published a recovery plan in March of 2015, which clearly outlined the conservation goals and efforts for Elkhorn coral. This document indicated that the main goals are to increase the abundance of this species and protect the genetic diversity throughout its entire range.[20]
This latter goal is especially important for conservation. Elkhorn coral are capable of both sexual and asexual reproduction; however, asexual reproduction is more common, which has resulted in only about 50% of Elkhorn being genetic individuals.[11] The lack of genetic variation makes the species more susceptible to threats and is, therefore, an important focus for conservation.
Most of the ongoing restoration projects for Elkhorn coral involve the creation of protected areas, which are intended to promote reproduction and growth by minimizing some of the threats to the species.
On November 26, 2008, the NMFS issued a final rule, effective December 26, 2008, which designated 2,959 square miles (7,664 sq km) as critical habitat for Elkhorn coral. The habitat described is composed of four different areas, which include the coasts surrounding Florida, Puerto Rico, the St. John and St. Thomas area, and St. Croix. These areas were specifically chosen because they contain the surface features which are necessary for the conservation of Elkhorn. In order to increase the amount of successful sexual and asexual reproduction events, the species require hard surfaces within water depths ranging from the mean high water line to about 30 meters.[6]
In 2009, the United States government enacted the American Recovery and Reinvestment Act, which provided funding for coral conservation through the National Oceanic and Atmospheric Administration (NOAA) department. This funding allowed for the creation of a network of coral nurseries throughout the waters off the coast of southern Florida and the U.S. Virgin Islands for the recovery of Elkhorn coral. The nurseries have proven helpful in conducting genetic research in the facilitation of overall reef growth and restoration.[11]
Even 14 years after being listed as threatened, the Elkhorn coral remains so. This failure is in part due to the time and energy-intensive procedures that were previously required to rehabilitate Elkhorn coral reefs. These procedures needed coral to be grown for months to years in nurseries before being planted in the ocean. However, new research suggests that Elkhorn coral can be planted in the ocean after just two weeks of being raised in a nursery. This decrease in nursery time makes it approximately 30 times cheaper to rear Elkhorn coral now. This cost reduction makes it financially easier for nations to restore their reefs.[21]
Elkhorn coral (Acropora palmata) is an important reef-building coral in the Caribbean. The species has a complex structure with many branches which resemble that of elk antlers; hence, the common name. The branching structure creates habitat and shelter for many other reef species. Elkhorn coral is known to grow quickly with an average growth rate of 5 to 10 cm (2.0 to 3.9 in) per year. They can reproduce both sexually and asexually, though asexual reproduction is much more common and occurs through a process called fragmentation.
Although Elkhorn coral dominated the Caribbean in the early 1980s, the species has since dramatically declined in numbers. Scientists have estimated that between 1980 and 2006, when it was listed in the Endangered Species Act (ESA), the population declined by around 97%. This decline was due to a variety of factors, including disease, algae growth, climate change, ocean acidification, and human activity. In May 2006, Elkhorn coral was officially listed as threatened in the ESA along with another species in the Acropora genus, staghorn coral. Some conservation efforts are now in place to protect the species and promote increased genetic variability among the species.
El Acropora palmata es una especie de coral de la familia Acroporidae, orden Scleractinia.
Su nombre común es coral cuerno de alce, pues su estructura se asemeja mucho a la de los cuernos de alce. Es considerado como uno de los corales de arrecife más importante en el Caribe. Esta especie de coral es de estructura compleja, con muchas ramas grandes. Estas ramas crean hábitats para muchas especies como langostas, peces loro, pargos, y otros peces de arrecife de coral.
Forma las colonias coralinas más grandes de todas las especies de Acropora, comúnmente con 4 m de ancho, 2 m de alto y 0.4 m de grueso en la base. Las ramas son cónicas, muy gruesas, paralelas, oblicuamente inclinadas y horizontalmente aplanadas hacia sus extremos. Los coralitos son tubulares y desiguales en tamaño. Los coralitos axiales, si los forman, son indistintos.[2]
Las colonias de coral cuerno de alce tienen un extraordinario rápido crecimiento, con una tasa promedio de 5-10 cm por año, alcanzando su tamaño máximo en un periodo de entre 10 y 12 años.[3]
El color de esta especie es café, verde o amarillo-marrón. El color es el resultado de la combinación de los pigmentos y las zooxantelas simbióticas que viven dentro del tejido del coral. Los coralitos axiales son blancos, al no poseer zooxantelas, porque son alimentados por el resto de la colonia, por esta razón los extremos de las ramas, donde se ubican, son blancos.
Los pólipos contienen algas simbióticas llamadas zooxantelas. Las algas realizan la fotosíntesis produciendo oxígeno y azúcares, que son aprovechados por los pólipos, y se alimentan de los catabolitos del coral (especialmente fósforo y nitrógeno).[4] Esto les proporciona entre el 75 y el 95 % de sus necesidades alimenticias. El resto lo obtienen atrapando plancton microscópico y materia orgánica disuelta en el agua.
La mayoría de la reproducción del coral cuerno de alce se produce asexualmente, lo que ocurre cuando una rama del coral se rompe y se une al sustrato, dando origen a la formación de una nueva colonia (fragmentación). El grado estándar con el cual se reproducen por fragmentación varía en el Caribe, pero, más o menos, el 50 % de las colonias son resultado de la fragmentación, en lugar de la reproducción sexual.
La reproducción sexual se produce una vez al año, en agosto o septiembre, cuando las colonias de coral liberan millones de gametos por el desove de difusión. Sexualmente son hermafroditas simultáneos, lo que quiere decir que las colonias generan gametos masculinos y femeninos, lanzando simultáneamente al exterior sus células sexuales, siendo por tanto la fecundación externa. Los huevos una vez en el exterior, permanecen a la deriva arrastrados por las corrientes varios días, más tarde se forma una larva plánula[5] que, tras deambular por la columna de agua marina, y en un porcentaje de supervivencia que oscila entre el 18 y el 25 %, según estudios de biología marina,[6] cae al fondo, se adhiere a él y comienza su vida sésil, secretando carbonato cálcico para conformar un esqueleto de aragonita, o coralito. Posteriormente, forman la colonia mediante la división de los pólipos por gemación.
A. palmata en Florida, EE.UU.
A. palmata, vista de coralitos.
Ramas de A. palmata saliendo del agua, isla San Salvador, Bahamas.
A. palmata, isla San Salvador, Bahamas.
Buceo sobre A. palmata en el Parque Nacional Vizcaíno, Florida.
Buceo sobre A. palmata en el Parque nacional Biscayne.
A. palmata.
A. palmata en Bonaire.
A. palmata en el Caribe.
"Escuela" de A. coeruleus rodeando colonia de A. palmata, Puerto Rico.
A. palmata en isla San John, islas Vírgenes, EE.UU.
El coral cuerno de alce ocurre principalmente en aguas poco profundas, cerca de la superficie, en arrecifes exteriores expuestos a fuerte oleaje.[1] Son una de las especies más abundantes en las aguas que van desde 1-5 m de profundidad, y algunas colonias se han registrado en aguas de hasta 20 m de profundidad (por ejemplo, en la isla de Navaza). Su rango de profundidad es entre 1 y 20 m,[7] aunque se reportan localizaciones hasta 41 m, y en un rango de temperatura entre 26 y 28.06 ºC.[8]
Se encuentra en el Caribe, las Bahamas y los cayos de la Florida. Su área de distribución llega hasta el norte del Parque nacional Biscayne, la Florida y hasta el sur de Venezuela. Sin embargo, se ha sugerido que, como resultado del cambio climático, la gama de coral cuerno de alce se ha expandido hacia el norte a lo largo de la península de Florida y hacia el norte del golfo de México.
Es especie nativa de Anguila; Antigua y Barbuda; Bahamas; Barbados; Belice; Bonaire, San Eustatius y Saba (Saba, Sint Eustatius); islas Caimán; Colombia; Costa Rica; Cuba; Curazao; Dominica; República Dominicana; Estados Unidos; Granada; Guadalupe; Haití; Honduras; Jamaica; México; Montserrat; Nicaragua; Panamá; Saint Barthélemy; San Kitts y Nevis; Santa Lucía; San Martín (parte francesa); San Vicente y las Granadinas; San Martín (parte holandesa); Trinidad y Tobago; Turks y Caicos; Venezuela e islas Vírgenes, Británicas.[1]
El cuerno de alce fue una de las especies más abundantes de coral en el Caribe y los Cayos de la Florida. Desde 1980 se ha estimado que del 90-95 % de este coral se ha perdido. Las amenazas incluyen enfermedades como, el blanqueo de los corales, la depredación, el cambio climático, daños de tormentas, sobrepesca, turismo sin control y la actividad humana. Todos estos factores han creado un efecto sinérgico que disminuye en gran medida la supervivencia y el éxito reproductivo del coral cuerno de alce. La recuperación natural de los corales es un proceso lento, y se dificulta con esta especie, porque hay muchos inhibidores que influyen en su supervivencia.
Las enfermedades que afectan al coral cuerno de alce son: la enfermedad de la viruela blanca o serriatosis de acróporas, la enfermedad de banda blanca y la enfermedad de banda negra. La enfermedad de la viruela blanca es una enfermedad que sólo afecta a estos corales. Es causada por un enterobacterium fecal, Serratia marcescens. La enfermedad es muy contagiosa y generalmente se mueve de una colonia a su vecino más cercano. La viruela blanca crea lesiones blancas en el esqueleto del coral y los resultados son la pérdida de tejido, aproximadamente de 2,5 centímetros cuadrados por día, pero puede causar la pérdida de tejido de más de 10,5 centímetros cuadrados por día. La enfermedad de banda blanca y la enfermedad de banda negra también han reducido en gran medida la abundancia del coral. Las enfermedades son una de las principales causas de mortalidad de los corales, sin embargo, no se han estudiado o comprendido suficientemente.
Los depredadores del coral cuerno de alce incluyen caracoles (Abbreviata coralliophila), poliquetos como el gusano barba de fuego y las damiselas. La depredación por parte de estos organismos reduce el crecimiento de los corales y la capacidad de reproducirse. La depredación puede conducir eventualmente a la muerte de unas colonias de corales.
Ha habido varios esfuerzos para la conservación del coral cuerno de alce, que han tenido resultados mixtos. El Santuario Marino Nacional de los Cayos de Florida, ha sido una región protegida para las especies de coral de la zona. Este mismo, también ha elaborado planes para la protección y restauración del coral cuerno de alce. Los esfuerzos de restauración han incluido los intentos de volver a conectar los fragmentos de coral que se rompieron durante los huracanes o por los buques. Los intentos de volver a conectar los fragmentos de coral también se han producido en Puerto Rico y las Islas Vírgenes, pero todos han tenido un éxito limitado.
También se está intentando, para conservar el coral, el cultivo de fragmentos de coral. El Santuario Marino Nacional de los Cayos de Florida, la Administración Nacional Oceánica y Atmosférica de Estados Unidos (NOAA) y el Laboratorio Marino Mote, están teniendo un éxito limitado con los viveros de coral en los cayos de Florida y Puerto Rico.
En México se han establecido diversas Áreas Naturales Protegidas, como el Parque nacional Cozumel, el Parque nacional Costa Occidental de Isla Mujeres, Punta Cancún y Punta Nizuc, y la Reserva de la Biosfera Arrecifes de Sian ka´an, que fue declarada Patrimonio de la Humanidad por la Unesco en el año 1987.[3]
La Administración Nacional Oceánica y Atmosférica ha desarrollado, y probado, varios métodos ecológicos para restaurar esta especie de coral. Estos métodos incluyen la eliminación de depredadores de coral y la reintroducción de especies herbívoras en los ecosistemas, que se alimentan de algas nocivas que crecen en el coral.
En 2004, el Centro para la Diversidad Biológica pidió al Servicio Nacional de Pesca Marina (National Marine Fisheries Service, NMFS) que el coral cuerno de alce tenga un lugar en la lista de especies en peligro de extinción. En 2005, el NMFS decidió que el coral cuerno de alce fuese calificado como una especie en peligro de extinción en virtud de la Endangered Species Act de 1973. El 4 de mayo de 2006 el coral cuerno de alce y el coral cuerno de ciervo (A. cervicornis) fueron oficialmente incluidos en la Lista Roja de la UICN.
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El Acropora palmata es una especie de coral de la familia Acroporidae, orden Scleractinia.
Su nombre común es coral cuerno de alce, pues su estructura se asemeja mucho a la de los cuernos de alce. Es considerado como uno de los corales de arrecife más importante en el Caribe. Esta especie de coral es de estructura compleja, con muchas ramas grandes. Estas ramas crean hábitats para muchas especies como langostas, peces loro, pargos, y otros peces de arrecife de coral.
Le corail corne d’élan (Acropora palmata) est un des principaux coraux formant les récifs de coraux des Caraïbes.
Le corail corne d’élan a une structure complexe avec de nombreuses grandes branches qui forment un habitat privilégié pour divers habitants des récifs comme les homards, les poissons perroquets. Les colonies de corail à cornes d’élan croissent très vite (5 à 10 cm par an) et peuvent atteindre un diamètre de 3,50 mètres. Sa couleur varie du marron au brun-jaunâtre. Elle résulte d’une symbiose avec une zooxanthelle qui vit à l’intérieur des tissus de ce corail. Cette algue réalise la photosynthèse et fournit le corail en nutriments.
Acropora palmata dépend des composés organiques produit par les zooxanthelles symbiotes. Il consomme également des proies telles que du zooplancton et des petits poissons, qu'il capture avec ses tentacules[2].
Historiquement, la majorité de la reproduction du corail à cornes d’élans est asexuée, et a lieu lorsqu’une branche du corail se rompt et va s’implanter dans un autre substrat, créant une nouvelle colonie (fragmentation). On considère généralement que 50 % des colonies ont pour origine la fragmentation, bien que ce chiffre varie localement à travers les Caraïbes. La reproduction sexuée se déroule une fois par an en août ou septembre quand les colonies de corail relâchent des millions de gamètes dans l’eau.
Cette espèce est présente dans les Caraïbes, le golfe du Mexique, la Floride et les Bahamas[3]. Elle s'étend au sud jusqu'au Venezuela[4].
Acropora palmata fait partie des espèces protégées du Endangered Species Act depuis le 4 mai 2006[5],[2]. En décembre 2012, le NOAA's National Marine Fisheries Service propose de reclasser l'espèce en tant qu'espèce menacée[6],[2].
Le corail corne d’élan (Acropora palmata) est un des principaux coraux formant les récifs de coraux des Caraïbes.
Acropora palmata is een rifkoralensoort uit de familie van de Acroporidae.[2] De wetenschappelijke naam van de soort is voor het eerst geldig gepubliceerd in 1816 door Lamarck. De soort komt voor in de Caraïbische Zee, de Golf van Mexico en bij Florida en de Bahama's. De soort staat op de Rode Lijst van de IUCN geklasseerd als 'kritiek'.[1]
Bronnen, noten en/of referenties
Acropora palmata er ein steinkorall som finst i Karibia, der han er ein viktig korallrevbyggjar. Han er rekna som ein truga art.
Acropora palmata er ein steinkorall som finst i Karibia, der han er ein viktig korallrevbyggjar. Han er rekna som ein truga art.
Acropora palmata là một loài san hô trong họ Acroporidae. Loài này được Lamarck, mô tả khoa học năm 1816.
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Acropora palmata là một loài san hô trong họ Acroporidae. Loài này được Lamarck, mô tả khoa học năm 1816.
