Coral Reef Adventure
Reefs support 25% of all marine life. This coral relationship between zooxanthellae algae and coral. Coral reefs view of a single coral polyp with visible zooxanthellae algae. animated diagram that illustrates the chemical exchange. 3). coral polyps in a coral colony feed, thereby exhibiting the symbiotic relationship between coral polyps and zooxanthellae. Objectives Coral Comics worksheet. Diagram of coral and zooxanthellae relationship. Key for above graphic. Coral polyps, which are animals, and zooxanthellae, the plant cells that live within them , have a This animation shows how the products created by the algal polyp and .
A coral polyp consists primarily of tentacles, a mouth and a gut think upside down jellyfish. Many corals are passive feeders on plankton. Most corals also get nutrition from microscopic algae zooxanthellae living within their tissue.
Coral polyps are generally nocturnal feeders and are provided sugars made by their photosynthetic zooxanthellae during the day. Corals extract calcium and carbonate from seawater to build an inner skeleton that is external to the coral.
This external skeleton lies underneath a thin layer of tissue. Over the years millions of coral polyps in colonies create the framework of the coral reef. Coral reefs grow very slowly. It may take up to a hundred years for a coral reef to grow one meter around three feet.
Hard corals, also called reef-building corals, produce a rock-like skeleton made of the same material as classroom chalk calcium carbonate. These skeletons and the various shapes of different colonies form the familiar structure of the reef. Hard corals rely on symbiotic algae zooxanthellae living within their tissues for nutrition and energy to build their skeleton.
They must therefore live in shallow clear water to allow sunlight to reach the algae. Soft corals look like colorful plants or graceful trees and are not reef-building since they do not produce the hard calcified skeleton of many reef-building corals.
However, soft corals do produce smaller amounts of calcium carbonate that help them keep their shape. Soft corals can be distinguished from hard corals by the fact that soft coral polyps always have eight tentacles, while hard coral polyps have multiples of six tentacles.
Symbiosis is defined as the close association between two or more interacting organisms, usually of different species. The relationship is usually classified as belonging to one of three types: Changes in the physical environment such as the amount of sunlight or salinity, or the temperature, and in the biological community, such as the presence or absence of other organisms and how they interact with the symbiotic pair, may change the nature of the symbiotic relationship from one type to another.
Like organisms, symbiotic relationships are responsive to the environment and can change over time. This enormous reef is over kilometers miles long and covers more thansquare kilometers aboutmiles.
Home to more than species of fish, dolphins, whales and sea turtles, the Great Barrier Reef is actually a collection of more than smaller reefs.
Species Interactions | BioNinja
The second largest reef lies off the coast of Belize, in Central America. Reefs are generally classified into the following three types: Fringing reefs, the most common type of reef, form along a coastline. They grow on the continental shelf in shallow water. They are so called because they form a barrier between the lagoon and the seas, protecting the coastline.
Coral Atolls are rings of coral reef growing on top of old sunken volcanoes in the ocean. They begin as fringing reefs surrounding a volcanic island; then, as the volcano sinks, the reef continues to grow, and eventually only the reef remains. There are over atolls in the South Pacific.
Do Any Animals Eat Corals? This implies that some species of the Symbiodinium have adapted to the UV radiation, while some still have not, and perhaps in the future the algae with the ability to survive will attach to the majority of the coral so UV radiation will no longer be a threat to reefs. Global Warming Figure 4. It is expected that if the ocean warms just one to two degrees, the locations that are between twenty and thirty degrees North will then fall within the range of lethality for most coral species.
Some may be able to adapt, but typically the photosynthesis pathways are hindered at temperatures rising above thirty degrees Celsius. Thus, temperature shocks resulting from global warming results in zooxanthellae adhesion dysfunction, so they detach and are expelled from the coral 5.
In a study fromit was shown that the Symbiodinium density significantly decreased after twenty-seven days of heat stress In other words, different zooxanthellae are sensitive to different temperatures, and coral can expel the old algae in hopes that the less sensitive algae will have survived and become a new symbiont.
This is an idea among scientists because zooxanthellae species diversity is very widely spread Figure 5. Horizontal gene transfer and many genetic lineages make up the Symbiodinium species, causing disparity among the clades. So although there are many Symbiodinium-like species, this idea of clade shuffling seems slightly implausible, because it usually is a matter of Another study focused on the classification of zooxanthellae They isolated compounds that were later identified as toxins that were unique from other dinoflagellates.
The discovery and research into these compounds also supported that the molecules were from the algae and not a result of the host, but it seemed that variation to the host and environment caused the production of different algal metabolites. Many other toxins and compounds were isolated in this study and added significantly to the fact that the metabolism and taxon of zooxanthellae are extremely diverse.
Furthermore, it has been shown that specific Symbiodinium are more tolerant to heat and stress, and perhaps corals adopting these specific algae will be able to survive the temperature changes from global warming and natural disasters Another study found that following bleaching, corals had clade shuffled from C2 to D, because D has a higher densities and photochemical efficiency, resulting in higher thermal tolerance The coral polyps do cellular respiration, thus producing carbon dioxide and water as byproducts.
The zooxanthellae then take up these byproducts to carry out photosynthesis. The products of photosynthesis include sugars, lipids, and oxygen, which the coral polyps thus uptake for growth and cellular respiration, and the cycle continues. The photosynthesis byproducts are more specifically used to make proteins and carbohydrates in order to produce calcium carbonate for the coral to grow.
What Is Coral? A Coral Polyp and Zooxanthellae | Smithsonian Ocean
Furthermore, the oxygen is used by the coral to help remove wastes. This recycling of nutrients in between these symbionts is extremely efficient, resulting in the ability to live in nutrient poor waters. About ninety percent of the material produced by photosynthesis is thought to be used by the coral 6. In terms of disease, the zooxanthellae is commonly the point of attack, rather than the coral itself. For example, the Montastrae species, which causes Yellow Band Disease, affects the zooxanthellae directly rather than the coral 7.
Scientists found that a coral, Acropora, lacked an enzyme needed for cysteine biosynthesis. It thus needed Symbiodinium for the production of this amino acid.
The genome size for the zooxanthellae algae is about 1, Mbp while the coral is approximately Mbp: Sure enough, other studies have shown phosphate-linked relationships between these two species.Coral bleaching
Zooxanthellae extracted from the Acropora coral had two acid phosphatases P-1 and P The activity of these enzymes shows that perhaps their role is involved in the mobilization of a phosphate storage compound.
The exact role of these enzymes is unknown, but it seems that the symbiotic relationship between coral and zooxanthellae is phosphate limited But together, the coral and zooxanthellae can synthesize twenty amino acids 17 Figure 6. There is also a relationship between the amount of time the tentacles of the coral spend expanded or contracted and the amount of zooxanthellae present on the coral. In general, there was lower photosynthetic efficiency in the zooxanthellae coral species that has their tentacles expanded only at night than the species with their tentacles constantly expanded.
Also, the zooxanthellae density was higher in the continuously expanded tentacle species. These differences were found only in the light however, because when the species were placed in the dark no differences were found. Thus the light has a relationship with the coral and zooxanthellae, which was assumed because zooxanthellae are photosynthetic organisms.
Conclusively, the species with continuously expanded tentacles have dense populations or small tentacles. The findings suggest that small tentacles do not shade the zooxanthellae, thus they are all visible to the light, and that dense populations are necessary to harvest the light. So the species with these proactive properties expand continuously to collect all the light, while the species with few zooxanthellae only expand at night Another study related the exposure of the coral to oxygen as a means for oxygen radical accumulation in its tissues The O2 concentrations were found to increase by a pH of about 1.
Thus causes an increase of oxygen radicals in the coral tissues from the molecular oxygen, and the radicals can destroy cells. This study found that the anemones with higher chlorophyll, and thus higher Symbiodinium, actually adjusted their protein expression so the fluctuating oxygen concentrations would not be destructive. This is just another example of how the coral changes its innate reactions to adjust for its symbiotic algae Figure 7.
Movement Furthermore, it was found that the temperate symbiotic sea anemone, Anthropluera balli, incorporates a maternal inheritance of the zooxanthellae because the anemone live in locations of low zooxanthellae algae.
It was found that the spawned ova consistently contained zooxanthellae, and were released into the ocean water to become fertilized and grow. The zooxanthellae was clearly integrated into the life cycle of this particular sea anemone, and was found to localize at one end of the embryo to become integrated within the endoderm, which as mentioned above is where the zooxanthellae live within coral This study brings arise the question of how zooxanthellae disperse among the coral.
Another study discovered that the zooxanthellae can be released by the host in ways such as predation, extrusion, spontaneously, osmotically, or as we know, due to temperature or stress. This particular study proposes another way for zooxanthellae to disperse, through the feces of their predators. Interestingly, photosynthetic rates from the unharmed species were very similar to the rates from the fecal zooxanthellae that made their way through a digestive tract.
Furthermore, the zooxanthellae reinfected sea anemones after their travel through the digestive tract of their predator. This finding showed that predation is an important means by which the zooxanthellae are dispersed among a coral reef History The relationship between Symbiodinium and coral has been known for about fifty years. One of the first studies found that certain dinoflagellates fixed labeled carbon from CO2 and moved it to their host sea anemone after forty-eight hours.
This study also showed that Symbiodinium produced higher amounts of carbohydrates when living inside a host rather than free living After this symbiotic relationship was discovered, other studies delved further into how the algae and coral used the nutrients they acquired from the other. One study found specifically that the algae fixed the carbon primarily as glycerol, which was then taken up by the coral tissue as proteins and lipids It was also discovered that the other organic acids produced by the Symbiodinium were different biochemically, even though they looked the same This information was the beginning of other scientists discovering the increasingly wide variety in the taxon of dinoflagellates.
It is not entirely sure how the coral does this, but some studies have hypothesized.
Zooxanthellae and their Symbiotic Relationship with Marine Corals
Other studies suggest that the host coral produces compounds that act as host release factors, and that these factors can control the metabolite production in the Symbiodinium Energy Storage Not only are nutrients shared between the two species, but energy and energy production is integrated as well. The Symbiodinium produced these lipids, using acetate from the coral and extra ATP, and excreted them back to their host.
These lipids are mostly wax esters and triglycerides A figure showing the decline in zooxanthellae over a starvation period http: It was further shown that the retention of this ammonium by the coral was related to the Symbiodinium because the algae uptakes most of the ammonium itself The algae were also more efficient with its use of a nitrogen source because it can use nitrite.
A study used tagged enzymes involved in the use of different forms of nitrogen, and concluded that the algae do indeed utilize nitrates. They also found that the algae densities increase with the nitrate concentration, although further details of this relationship with the coral are not known