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Transcript of Coral Reefs
Coral Reefs Explained
What Are Coral Reefs?
Coral reefs are aquatic habitats made up of cnidarians known as coral polyps. In order to protect and support themselves, the polyps secrete a bone like calcium carbonate exoskeleton, forming the "coral" part of the reef.
Why are Coral Reefs Important?
While they only occupy 0.1% of our oceans, coral reefs are home to 25% of all marine life. This means that they are extremely dense ecosystems which house species from 32 out of the 34 recognized animal phyla. Coral reefs are one of the ecosystems with the highest biodiversity in the world.
Coral Reefs house a number of animal phyla, including chordates, molluscs, echinoderms, porifera, cnidarians, platyhelminthes, and nematoda
Because reefs host such a large diversity of marine life, many people have made a food source out of some of these species, in fact fish and molluscs caught in these reefs feed from 30 to 40 million people every year. Even larger than people is the amount of marine species that make these coral reefs their feeding grounds.
Coral reefs also have the ability to regulate the amount of CO2 in the ocean because of their ability to secrete shells from calcium and carbon. The amount of CO2 in the ocean is significantly lower due to these important ecosystems.
Coral reefs can also act as barriers to large waves, slowing the water before it reaches shore and physically protecting the land nearest to it.
What Happens if Coral Reefs Disappear?
How it Works
30-40% of the carbon dioxide released by humans into the atmosphere eventually dissolves into earths oceans, lakes, rivers, and other large bodies of water.
When CO2 enters the ocean, it bonds with the water, creating carbonic acid. Because it's basic, the shell of the coral goes through a pH reaction with the acid, the acid giving up a hydrogen ion. The reaction creates two bicarbonate ions, one from the acid and one from the shell. This causes the shell to wear corrode, and is part of the reason that coral reefs are becoming endangered.
In addition to this, the acidified water kills off zooxanthellae, a type of photosynthesizing plankton that form a symbiotic relationship with the coral and make up 90% of their food supply. With such a large percent of their food supply wiped out, the coral dies.
Effects of Ocean Acidification
Because the polyps can (through the secretion of carbon in their exoskeletons) regulate CO2 in the ocean, if coral reefs were to disappear, the CO2 levels would rise dramatically, contributing more and more to ocean acidification.
Ocean Acidification kills off a number of species simply through its nature, but also indirectly affects species making a home out of these coral reefs. If the reef dies, a significant number of coral reef species will lose the protection of the reef.
How it works
Coral bleaching is caused by extreme heat.
When conditions become too hot, the photosynthesizing algae inside the coral, zooxanthellae, either die out or leave the coral. Because the algae give the coral its pigmentation, the coral becomes white when this happens, hence the use of the term "bleaching"
This heat is most likely coming from climate change. In recent decades, our carbon emissions have climbed dramatically, increasing the average temperature. In fact, this year, the year following one of the hottest years on average, our carbon concentration reached 400 Parts per million. During 1997-98 "El Niño" (the irregular climate pattern in the Pacific equatorial regions associated with extreme heat) around 16% of the worlds coral was destroyed due to coral bleaching.
Because the algae provides for 90% of the corals food, the coral will die soon after bleaching occurs.
The warmer water also allows for the growth of harmful algae on top of the coral, which blocks out the sun, preventing whatever zooxanthellae there are left from photosynthesizing.
Effects of Coral Bleaching
Bleached corals are weakened and will eventually die, meaning they can no longer provide communities within the ecosystem with certain services such as protection
Throws off species living within the reef
Direct Human Impact
People fishing in coral reefs tend to use explosives to actually blow up the reefs so they wont have to do any actual fishing, and the dead fish will float to the top
These "Fishermen" will also use poisons such as arsenic to kill the fish, harming the reef at the same time.
Conservation of Coral Reefs
People have been both intentionally and unintentionally growing artificial coral reefs. An example of an artificial reef may be anything from a designated structure to a shipwreck to a pile of used tires.
Pretty much any upright structure in the right place can become a coral reef. Plankton will be swept into the structure, fish will use it for shelter from predators, which will in turn follow them there. In the following months, coral, sponges, algae, etc. will start to grow on the structure.
Artificial reefs, however are somewhat controversial, as many environmental groups believe they need to be re-examined, claiming that they are toxic, damage ecosystems, and worsen overfishing by concentrating fish into one place.
Many environmental agencies like the EPA and NOAA have created programs addressing the problem.
They lobby for stricter conservation of these reefs, and try to get funds to put towards protecting them.
In 1998, President Clinton issued an executive order to form the United States Coral Reef Task Force, a committee which would oversee the protection and conservation of coral reefs on a domestic and international scale.
Environmental organizations are looking into numerous methods of mitigating the destruction of coral including:
Researching and finding ways to cure and prevent coral diseases as well as treating coral injuries such as oil spills or anchor drags
Finding ways to better the water quality by reducing pollutants in our atmosphere and oceans
Reducing Climate change to prevent coral bleaching
Controlled reproduction/ cultivation of coral to rebuild coral reefs without certain effects of toxicity, acidity, heat, etc.
Coral Reefs are Disappearing
Numerous studies put forth compelling new evidence that these aquatic metropolises are dying out.
In fact, just recently, a team of Australian and Chinese scientists found that Chinese reefs, which had once been some of the most flourishing in the world, have decreased by 80% in the past 30 years. This is strong evidence of pollution's effects on coral reefs in that China had been only recently industrialized 30 years ago, and are now notorious for pollution and extremely poor air quality. This is proof of our role in both ocean acidification as well as coral bleaching in that we are providing the pollution that causes these phenomena.
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Because coral reefs are such diverse and thriving ecosystems, they host a number of important species.
Corals- Corals are the most prominent species in reefs, they are really just polyps that secrete an exoskeleton, giving them the "coral" part.
Sponges- Sponges filter feed on particles and organic carbon, making them the recyclers of a reef.
Herbivorous fish- Herbivorous fish use coral reefs mainly for protection from strong ocean currents as well as carnivorous fish. In return, the fish clean the reef of algea, preventing it from smothering the reef. An example would be the clown fish using the anemone as shelter.
Carnivorous fish, sharks, and rays- Carnivorous fish feed off of the species living in coral reefs, mainly other fish and crabs.
Crabs- Crabs are important to coral reefs in that they actually help clean up reefs, keeping them healthy for other species to live in.
Mesograzers- Control the admission of different benthic organisms into reefs (by eating them)
Zooxanthellea- Photosynthesizing plankton that live inside of corals and account for roughly 90% of their food source.
Anemones- Sea anemones play a significant role in protecting clown fish, the fact that they are used as shelter characterizes one of the most important aspects of the reef
Plenty of Organizations and interest groups advocating for the preservation and conservation of coral reefs have found the funding to do so. Government committees as well as environmental groups have very heavily researched coral reefs, and have developed a number of plans to fix them, however these organizations only started caring about coral within the past decade, meaning that a much longer time than a few years is necessary to compensate for the amount of corals lost, so the projects are still ongoing. In general, conservation efforts are a work in progress.