Mutualism in Coral Reefs | Sciencing
The mutually beneficial relationship between algae and modern corals — which provides algae with shelter, gives coral reefs their colors and. The corals couldn't survive without these microscopic algae–called zooxanthellae (zo-zan-THELL-ee). This cutaway diagram of a coral polyp shows where the. Symbiosis between Zooxanthellae & Corals. By. Mark Mergler. What are Zooxanthellae? Unicellular yellow-brown dinoflagellate algae which live in the gastrodermis of corals; Provide corals with Symbiotic Relationship between the Two.
The coral bleaching phenomenon occurs when zooxanthellae are expelled by the coral, in which case eventually the coral will die.
The anemone and clown fish is an example of facultative mutualism. The clown fish brings food to the anemone while the anemone wards off predators with its stinging polyps. However, the clown fish could live in another type of home and the anemone could capture food from the water without being fed by the anemone. Shifting Relationships The exact nature of a mutualistic relationship may shift from neutral to positive to negative.
These changes occur over time, with changing environmental conditions, or because of changes in the organism communities. Coevolution The symbiotic relationship that occurs in a mutualistic partnership, especially in an obligate mutualism, creates a situation where coevolution may occur. 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. 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.
The Symbiotic Relationship between Zooxanthellae and Coral by Brianna Velasquez on Prezi
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.
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.
Zooxanthellae and their Symbiotic Relationship with Marine Corals - microbewiki
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.
Zooxanthellae and their Symbiotic Relationship with Marine Corals
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 Symbiotic corals exhibit banded growth patterns right, indicated by red arrows that correspond to the availability of daylight.
The algae use photosynthesis to produce nutrients, many of which they pass to the corals' cells. The corals in turn emit waste products in the form of ammonium, which the algae consume as a nutrient.
This relationship keeps the nutrients recycling within the coral rather than drifting away in ocean currents and can greatly increase the coral's food supply. Symbiosis also helps build reefs — corals that host algae can deposit calcium carbonate, the hard skeleton that forms the reefs, up to 10 times faster than non-symbiotic corals.
Finding out when symbiosis began has been difficult because dinoflagellates have no hard or bony parts that fossilize. Instead, the researchers looked for three types of signatures in the coral fossils that indicate the past presence of algae: This polished fossil slab used in the study dates to more than million years ago and contains well-preserved symbiotic corals.
The fossils were collected in a mountainous region in Antalya, Turkey, and originated in the Tethys Sea, a shallow sunlit body of water that existed when the Earth's continents were one solid land mass called Pangea.