Ages 13-16
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Interrelationships in coral reefs
Biodiversity of a coral reef
facts about coral reefs
climate change and the coral reef
All about coral reefs
Invasive Species
Invasive species are not native to the coral reef, but they end up there by accident. The arrival of invasive species is often disastrous for the biodiversity, because the local species are not adapted to deal with the threat these species pose. For example, there was once an island without any snakes. It had a very diverse bird population. But when people came to the island, they introduced a few snake species by accident. The birds were not accustomed to the threat the tree snakes posed, and their numbers were quickly decimated. The same thing happens in coral reefs when there are new species introduced. For example, a main threat to coral reefs is the lionfish. Lionfish are native to the Indo-Pacific waters and their reefs, but they have moved to the North Atlantic waters. They pose a threat because they eat organisms who are normally eaten by other things and upset the balance within an ecosystem (food webs). Invasive species are mostly spread through various fishing endeavors and wreak havoc in the ecosystems.
Coral Bleaching
Another threat to coral reefs is coral bleaching. Coral bleaching occurs when the zooxanthellae (mutualism and biotic and abiotic factors) are expelled by the coral colony. This happens when the coral is under great stress, like a dramatic change in temperature. The zooxanthellae leave and the coral turns white. The coral is not dead, but is very vulnerable and this has disastrous effects on the community that call the coral their home. With ocean temperatures rising as a result of global warming, the corals are stressed and become bleached. This can also happen when the water becomes colder. The issue of coral bleaching is becoming increasingly prevalent as Earth’s temperatures rise.
These are some of the main issues that coral reefs are facing, but there are many others. Mostly, they have to do with the pollution that we are inflicting on our poor planet and global warming. We have to start thinking about where the by products of our society and what effect that has on the planet.
Ecosystems need to be complex (at least to an extent) in order for biodiversity to flourish. Coral reefs are definitely complex and biodiverse ecosystems, so as you will see. The coral exoskeletons provide the perfect environment for lots of anemones, jellyfish, barnacles, sponges, crabs, lobsters, octopii, sand dollars, squid, countless species of fish, and much more.
Here is a food web that is based off of the Great Barrier Reef, the largest coral reef in the world.
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You may notice on these webs that the organisms that are doing well have more than one food source. This is because if one species were to suddenly go extinct and another species was solely dependent on that species for food, they would die out too. Since fluctuation is population sizes is natural, the species that do the best are adapted to eating more than one thing. In general, the more diversity within the species, the better the species will do when faced with adversity. If the species is varied, than some of the individuals might be better prepared to deal with a change and though some of the individuals would die, the species as a whole would have a better chance of survival. This is basically how evolution works.
So what else causes an ecosystem to be more biodiverse? Well, as you see in the food webs above, a complex food web helps to keep biodiversity high. Another thing that helps biodiversity is when the climate remains consistent. In the case of corals, changes in temperature have stressed the corals out, causing coral bleaching. Ecosystems are accustomed to dealing with some change, but the dramatic changes that the world is facing today are sometimes too much for the ecosystems to cope with. When this happens, species are lost and the biodiversity decreases.
Why do we care? Biodiversity keeps the ecosystems stable and besides their amazing natural beauty, coral reefs provide homes to animals that we hunt, keep as pets, and see in aquariums. We appreciate coral reefs, and if we want to keep them beautiful, we have to start working to protect them from the problems we are causing them. Which brings us to a new topic. What is happening to the coral reefs and how can we help?
Interrelationships are the interactions between different species. They are very important to the well being of ecosystems, because they help to create a balance between species, and a complex and diverse ecosystem is like a safety net if some disaster were to strike a single species. In the coral reef, there are lots of different sorts of interrelationships. In a coral reef, we can find examples of mutualism, commensalism, parasitism, predator prey relationships, and the relationships between herbivores and autotrophs. We are going to group the relationships based on who benefits.
Mutualism
When two species are working together and both are benefiting from the collaboration, then it is an example of a relationship demonstrating mutualism. In a coral reef, you can find mutually beneficial relationships such as coral polyps and zooxanthellae. Since coral polyps are animals and therefore need an energy source, they have a very special bond with tiny creatures called zoooxanthellae. Zooanthellae are similar to plants in that they can photosythesize, meaning that they can turn light energy into sugar, which can be used by the corals. But most of the time, when a primary consumer (like the coral) gets energy from a producer (zooxanthellae), they normally eat the organism (herbivore autotroph relationship). When a rabbit (primary consumer) needs energy, it eats a plant (primary producer). Coral polyps and zooxanthellae are different. The zooxanthellae photosythesize and the coral is able to get the sugar from the photosythesis. The coral needs zooxanthellae. But the zooxanthellae are also helped by the coral. The coral provides protection and a good environment. So they are an example of mutualism.
Commensalism
When one species is reliant upon another species without damaging or helping the other organism. An example of commensalism is the relationship between manta rays and remora. Manta rays and remora are both consumers eat small fish, crustaceans, and jellyfish. Remoras follow the manta rays and eat the bits that the rays leave behind, which is helpful for the remora, and doesn’t matter to the ray.
Parasitism
When one species obtains nutrients from the host, but this damages the host. There are two broad categories of parasites, internal parasites and external parasites. If you ever have to do a tick check after going for a walk in the woods, then you already know about external parasites. They live on the outside of the host. Internal parasites live inside of the host animal. For example, if you have a dog, you probably give your dog heartworm medicine. Heartworm medicine protects the dog from heartworms, very dangerous parasites for pets. In the coral reef, there are lots of parasites. Here is an example. Tapeworms are part of the class Platyhelminthes. They live in the intestines of their host animal. Tiger sharks happen to be one animal that hosts a type of tapeworm, so
the relationship between them is parasitism. Tapeworms are a varied group though, so the tapeworms inside of tiger sharks are different from those inside, say, an eel.
Predator Prey Relationships
These are very important relationships that are easy to find everywhere! A predator hunts and eats the prey, so if you ever go fishing, you are the predator and the fish is the prey. Predator prey relationships keep populations balanced and are vital to a healthy ecosystem. Naturally, there are lots of predator prey relationships in coral reefs. For example, coral polyps are eaten by the Copperband Butterflyfish (Chelmon rostratus). The coral polyps are the prey and the Butterflyfish the predator.
Herbivore Autotroph Relationships
A herbivore autotroph relationship is when a primary consumer (herbivore) eats an autotroph (producer) to obtain energy. For example, seaweed (a producer) is eaten by crustaceans like crabs and lobsters. This keeps the seaweed population at a healthy level and the crustaceans fed.
How You Can Help
save coral reefs
Anybody can be a coral reef hero. All it takes is a donation of any size to help preserve and protect our beloved coral reefs. Every penny counts. Coral is not abiotic. It is a living organism that needs to be preserved and protected. No matter where you live, there are things you can do to protect coral reefs. From reducing carbon emmisions or improving water use, you can take steps right now to becoming an advocate for reefs. Donate today and start making a difference.
