Coral Reefs: More than Beautiful Jennifer Miselis University of South Carolina Program of Marine Science
Phylum: Classification of Corals Cnidaria Class(4): Anthozoa Hydrozoa Cubozoa Cubozoa Subclass(3): Octocorallia Ceriantipatharia Hexacorallia Orders(11): Antipatharia Ceriantheria Gorgonacea (sea fans/whips) Telestacea Pennatulacea Helioporacea Alcyonacea (soft corals) Actinaria Scleractinia* (hard corals) Zoanthidea Corallimorpharia
*Scleractinians are further divided into Hermatypic and Ahermatypic Corals each having unique characteristics -Hermatypic- Produce Reefs Shallow water Warm water Need sunlight for symbiotic organisms -Ahermatypic- Do not produce reefs Deep water Cold water Have no symbionts Occur in isolated and colonial forms
Building partners: The polyp and the algae Corals grow through calcification Calcification:the build up of calcium to form a solid mass A coral s skeleton is made up of aragonite which is calcium carbonate (CaCO 3 ) in crystalline form
The Polyp and the Algae-continued Coral polyps absorb calcium and carbonate ions from seawater and food Calcium ions are secreted with bicarbonate (HCO 3 ) in mucus in the gut (mesentary) Zooxanthellae (algae) live within the cells of the coral polyp s gut
The Polyp and the Algae-continued During the day, the zooxanthellae go through photosynthesis The by-products of photosynthesis pass to the coral tissue The by-products help increase the precipitation of calcium carbonate i.e., coral skeleton formation The Reaction for Skeleton Formation Ca 2+ + 2HCO 3- Ca(HCO 3 ) 2 then Ca(HCO 3 ) 2 CaCO 3* + H 2 CO 3 *Crystalizes on substrate of existing aragonite to build reef.
The Polyp and the Algae-continued The relationship between coral polyps and algae is symbiotic. A symbiotic relationship between two organisms in which both benefit is called mutualism. This fish is protected from predators by the stinging anenome but also attracts food to the anenome, thus both benefit from each other
Primary Production Coral Reefs in the scheme of things Typical rates of net primary productivity for terrestrial and aquatic ecosystems Values reported in (g C / m 2. yr) Range of Primary Productivity for Coral Reefs: 300-5000 g C / m 2. yr
Primary Production-continued 1. Rates of Primary Production range from 300-5000 g C / m 2. yr. Sources of production are the benthic algae and the zooxanthellae. 2. Reefs are self-sufficient in terms of nutrients. Nutrient concentrations are usually low around coral reefs Coral reefs use regenerative and recycling mechanisms to create and maintain necessary nutrients 3. Coral reefs are multitrophic. They are capable of both autotrophy(self feeding, usually refers to photosynthesis) and heterotrophy(feeding on other organisms). 4. Coral reefs also support secondary production. The support comes from the breakdown and decomposition of the primary producers.
1. Temperature Factors that Effect the Growth and Distribution of Corals Temperature range for corals is between 18 C and 36 C. Ideal range is between 25 C and 29 C. Corals flourish in the tropics because the temperature is almost constant and within the ideal range. 2. Salinity Salinity range is between 27ppt and 40ppt (parts per thousand). Ideal salinity is 36ppt. 3. Light While the corals themselves do not require light, their algae symbionts do. Therefore, corals have to live in areas that receive strong light energy. Corals cannot grow where there is a lot of suspended sediment in the water column because it interferes with the amount of light the coral recieves.
Factors-continued 4. Depth Corals live from the surface to a maximum depth of 90m. Most, however, live above 50m. Ahermatypic corals live in deep sea up to 6000m because don t need zooxanthellae. Depth is very much related to temperature and light. Note how close this staghorn coral is to the water s surface.
Global Distribution of Coral Reefs The starred circles show the principal reef sites in the world. Note that most of the reefs occur between 30 N and 30 S latitude. The tropics represent optimal conditions (discussed previously) for reef growth.
Four Main Types of Coral Reef Types of Coral Reef 1. Atoll Occur in the Indian and Pacific Oceans Form from the complete subsidence of a marine volcano 2. Barrier Reef Best known examples are the Great Barrier Reef off the coast of Australia and the Great Sea Reef off the coast of Fiji Form parallel to the coasts but some distance off shore Result from the partial subsidence of a marine volcano 3. Fringing Reef Develop around islands Best known example is the Jamaican Reefs 4. Patch Reef Solitary reef structures; not associated with landforms
Types of Coral Reef-continued This figure shows the formation of the previous three reefs. Over time, a fringing reef will become a barrier reef and eventually a barrier reef will become an atoll due to the subsidence of a volcanic island.
Threats to Coral Reefs Anthropogenic Factors Coastal Development: -detrimental sedimentation (coastal erosion, dredge spoils, excessive river runoff) -mining runoff and industrial toxic waste effluents -excess nutrients (sewage release) cause algal blooms -hot water discharges from industrial plants Overexploitation and destructive fishing practices: -overfishing causes shifts in fish size, diversity and abundance -blast fishing, fishing with cyanide and toxic chemicals -unregulated tourism (poaching, anchors, trampling by divers and snorkelers)
Threats to Coral Reefs-continued Natural Factors: Hurricanes: -Heavy wind and wave action often breaks off large parts of the coral skeleton which then settle to the ocean floor where the corals are unable to recover due to lack of light. -Large storms also stir up sediment which blocks out the suns energy.
Examples of Diseases of Coral Bleaching Black-band disease Yellow-blotch/Yellow band Red-band disease
Coral reefs demonstrate the perfect balance of complexity and delicacy. While the coral reef is extremely productive it is very sensitive to its surrounding environment. We must strive to protect the delicate balance of every ecosystem so as to continue to enjoy the creative and colorful displays nature has provided for us.
References(to be provided soon!)