| Ivory bush coral | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Subphylum: | Anthozoa |
| Class: | Hexacorallia |
| Order: | Scleractinia |
| Family: | Oculinidae |
| Genus: | Oculina |
| Species: | O. varicosa |
| Binomial name | |
| Oculina varicosa | |
| Synonyms[4] | |
| |
Oculina varicosa, or theivory bush coral, is ascleractinian deep-watercoral primarily found at depths of 70-100m, and ranges fromBermuda andCape Hatteras to theGulf of Mexico and theCaribbean.[5]Oculina varicosa flourishes at theOculina Bank off the east coast ofFlorida, where coral thickets house a variety of marine organisms.[6] The U.S.National Marine Fisheries Service considersOculina a genus of concern, due to the threat of rapidocean warming.[7] Species of concern are those species about which the U.S. Government'sNational Oceanic and Atmospheric Administration (NOAA), National Marine Fisheries Service, has some concerns regarding status and threats, but for which insufficient information is available to indicate a need to list the species under theU.S. Endangered Species Act[8] (ESA). WhileOculina is considered a more robust genus in comparison to tropical corals, risingocean temperatures continue to threaten coral health across the planet.[9]
Oculina varicosa grows in arborescent branches, typically about 1 to 2 meters tall.polyps wrap around the coral branches and extend when feeding to provideOculina with essential nutrients from various forms ofplankton andalgae.O. varicosa has widely spaced, distinctcorallites, approximately 3 millimeters in diameter. WhileO. varicosa most often exists as anaposymbiotic coral (withoutsymbionts), it can also exist withsymbioticalgae which helps provide another food source. SymbioticOculina colonies withzooxanthellae generally come in various shades of brown, while azooxanthellate corals tend to have a lighter, whiter appearance.[6] Corals usually receive their brilliant color from their symbionts, so aposymbiotic colonies tend to lack bright colors.[10]
Coral growth usually relies on both food and sunlight, but becauseO. varicosa exists primarily as a deep-water coral, it typically lacks zooxanthellae. Only shallow water forms ofO. varicosa contain zooxanthellae because they have more access to sunlight. Zooxanthellae, or coral symbionts, serve in amutualistic relationship as a source of energy for coral colonies, while also receiving shelter between coral polyps.[6] Zooxanthellaephotosynthesize and transfer sugars to the coral polyp, but azooxanthellate, or aposymbiotic, coral colonies rely on obtaining energy throughheterotrophy. Coral polyps snatch planktonic matter out of the water column in order to produce energy for growth.[11] Surprisingly, corals have mouths and stomachs to digest the food they catch with their tentacles.[10] Coralheterotrophy is more nutrient dependent, while photosynthesizing symbiotic corals are more dependent on sunlight.
AlthoughO. varicosa is not considered a reef-building coral, it still serves an important role in creating larval habitat for native fish andinvertebrates.Oculina provides a base for hard-bottom communities in supporting valuable fisheries species and a variety of other economically important organisms.[12]
WhileO. varicosa does exist in both shallow waters (6 meters) and deep water, at depths of greater than 100 meters, it almost exclusively thrives on theOculina Bank off the coast of Florida.[7]Oculina coral reefs off Florida have been identified asessential fish habitat for federally managed species. TheExperimental Oculina Research Reserve preserves the Oculina Banks, a reef ofOculina varicosa existing between 70 and 100 meters depth, and spanning 130 nautical miles, approximately 15 miles off the coast of Daytona Beach.[13] Because symbionts only coexist withOculina in shallow water conditions, this excludes aposymbiotic colonies on the Oculina Bank.[6] At this location,O. varicosa branches grow into massive thickets and can reach up to 2 meters in height. Tree-like colonies on the Oculina Bank create an ideal place for a diverse population of fish and invertebrates to thrive. More than 70 species of fish and over 380 invertebrates call the Oculina Bank their home.[6] A variety ofgrouper species are known to spend much of their juvenile stages hiding in the branches ofOculina; namely,gag,scamp,speckled hind, yellowedge andsnowy grouper.[7] Discovered in 1975, the Bank became a protected area by 1984 as the Oculina Bank Habitat Area of Particular Concern. The known and documented threat in the Oculina Banks area is damage from mechanicalfishing gear, including dredges, bottom long lines, trawl nets andanchors despite supposed habitat-based protections.[14] Anchoring vessels and bottom-trending fishing gear became prohibited within the protected area, in an effort to maintain theOculina thickets and the habitat as a whole.[13]
Temperature ranges from 7 to 27 degrees Celsius on the Oculina Bank.[15] Such seasonal extremes effectively accustomOculina varicosa to wide temperature shifts. This temperature resilience indicates thatO. varicosa may be more apt to survive despite rising global ocean temperatures. Temperate corals, such asOculina arbuscula andAstrangia poculata, show relatively high tolerance to ocean warming because of these large seasonal shifts.[9] During upwelling events at the Oculina Bank, temperatures can settle around 7 degrees Celsius for days at a time.[6]
Because the genusOculina is considered one of the more resilient corals on the spectrum, it functions as a useful experimental subject, especially in the context of global climate change. Both cold and heat stress treatments on temperate corals serve as an important stepping stone in effectively dissecting coral health in response to rising ocean temperatures.[9] Researching the effects of temperature stress onO. varicosa furthers understanding of how both this species and the hard bottom communities it helps form, will change under warmer oceans.[16]
Data related toOculina at Wikispecies
