[INFORMATIVE] Coral Reef Ecosystems

Coral Reef Ecosystems

By: Lusine Galstyan

Coral reefs, well-known for their beauty and biodiversity, are important in maintaining Earth’s health. Coral reefs support marine life and provide various benefits to humans. Let’s explore some of the essential and basic components of the coral reef ecosystem.

Understanding the Coral Reef Ecosystem: Biotic and Abiotic Interactions & Keystone Species:
The ecosystem includes all biotic and abiotic parts of the given area. While biotic factors contain all the living things, the abiotic factors include all the non-living things. To better understand the difference between these two factors, let's view some examples of the biotic and abiotic factors of the coral reef ecosystem. Examples of biotic factors in the coral reef ecosystem are plants, crabs, fish, and coral. On the other hand, some examples of abiotic factors are water clarity, temperature (23-29°C), sunlight, salt, depth, oxygen, and waves (National Ocean Service).

Another essential thing to know about each ecosystem is the keystone species in it. Keystone species are species that have greater influence than the other species in that ecosystem. As the name of the ecosystem itself mentions, the keystone species of the coral reef ecosystem are corals themselves. Corals provide homes and safety for many sea creatures and keep the ocean healthy.

Food Webs and Trophic Levels:
Another crucial thing to know about ecosystems is the food webs. In simple terms, a food web has all the possible food chains in the ecosystem in it. Food webs are made up of different groups of organisms called trophic levels. The different groups include producers, consumers, and decomposers. Producers are in the first trophic level. They are the organisms that produce their energy through photosynthesis. Algae, phytoplankton, zooxanthellae, and seagrass are some examples of producers that can be found in coral reef ecosystems. Next are the consumers, who feed off other organisms. Some simple examples of consumers would be coral, sea turtles, and fish (ex: sharks, starfish, jellyfish, sea snakes, etc). Lastly, there are decomposers, which consume dead organic material and complete the cycling of energy (National Geographic). Examples of decomposers can be fan worms, snails, crabs, bacteria, etc.

Now that several organisms and their role in the food web have been discussed, let’s explore what symbiotic relationships can be found between organisms in the coral reefs, while also mentioning the overall size and distribution of the coral reef ecosystem.

Population Size, Distribution, and Symbiotic Relationships:

Coral reefs are not widespread globally. They are counted to cover only 284,300 km² (109,800 sq mi). This size is less than 0.1% of the ocean's surface area. Coral reefs live in warm ocean waters in the tropics and subtropics (Florida Museum). They can also be found outside of this area where warm water currents flow. For example, coral reefs can be seen in the Gulf Stream Current, which carries warm water from the Caribbean to Bermuda.

Even if coral reefs are not widely spread around the world, many examples of symbiotic relationships can be found in that ecosystem. A symbiotic relationship is simply a close relationship between two organisms. In the coral reef ecosystem, all 3 examples of symbiotic relationships (commensalism, mutualism, parasitism) can be found. An example of commensalism, where one organism benefits and the other stays unharmed, is the jellyfish and small fish example. Small fish hide in jellyfish tentacles to stay safe from predators. The jellyfish isn't harmed or helped by this. Another example of a symbiotic relationship is when both of the organisms benefit, which is called mutualism. Mutualism can be seen between coral and zooxanthellae. Zooxanthellae get a home in the coral and the coral gets energy from the zooxanthellae. And lastly, there is parasitism, where one organism benefits and the other gets harmed. An excellent example of this can be isopods and host fish. Several isopods eat fish’s tongue and live in its mouth taking whatever food the fish tries to eat (Press Books). By these actions, the fish gets harmed, while the isopod benefits.

Now that we gained an overall preview of what the ecosystem looks like and how the organisms in it function, let’s take a look at any disruptions in the ecosystem and how it affects the organisms in it.

Recent Disruptions:
The exquisitely coral reef ecosystem is under a severe threat: coral bleaching. Corals are keystone species that play a vital role. Thus, their loss has a strong negative effect on the entire coral reef ecosystem. Scientists warn that if urgent action is not taken, the very existence of corals could be in jeopardy. Higher sea temperatures and altering sea chemistry are huge risks to coral reefs. These are troubles brought on by increased air temperatures and more carbon dioxide in seawater. Warmer water stresses corals, making them lose the algae they need to survive, leading to coral bleaching. Other climate impacts such as sea-level rise and stronger storms, also damage coral reefs. This makes it even harder for corals to build their structure (US EPA).

However, coral bleaching is not the only issue. Millions of tons of plastic waste end up in the ocean every year. This pollution affects the life of coral reefs and other organisms living there. The thrown plastic, whether it is a grocery bag or water bottle, stays in the ocean. Those plastics not only block the sunlight from reaching the corals, but they also tear open the corals’ skin and allow various infections to form. While diving researchers gathered information about plastic found underwater and “they estimate that over 11 billion plastic items could be entangled in coral reefs in the Asia-Pacific region, home to over half the world's coral reefs” (Christopher Joyce). Therefore, coral reefs are very likely to undergo the most dangerous decline and face possible extinction if the dangers mentioned above remain unsolved.

After learning about the disruptions of the ecosystem and more possible harms that can come up, let’s explore coral reefs’ importance for humans and acknowledge why it is important to care for the ecosystem and work towards helping it gain strength.

Importance for Humans:

• Coral reef ecosystems play a crucial role in humans’ lives. Knowing some of the important aspects that coral reef ecosystems help humans with can lead to a better understanding of their importance and the necessity to address the dangers that risk the health of the coral reef ecosystem. Below are some of the main importances coral reef ecosystems have for humans.
• Food resources: Coral reefs can potentially produce 15 tons of fish and seafood per square kilometer each year. They support 6 million fishers in nearly 100 countries. “They are a primary source of food and protein for many coastal communities. In fact, 4.3 billion people around the world rely on fish for 15% of their animal protein intake” (Coral Reef Alliance).
• Protection: Coral reefs protect humans from waves, floods, and storms. They also prevent loss of life, property damage, and erosion. When reefs are damaged or destroyed, coastal communities face more harm from regular waves and strong storms without the coral reef natural barrier (National Ocean Service).
• Medicine: Many coral reef organisms produce chemicals used for treatments for cardiovascular diseases, and skin cancer. Over half of new cancer drugs come from marine life. Scientists believe there are still many medical discoveries to be made from coral reef organisms (Coral Reef Alliance). Thus, protecting coral reefs can lead to important medical discoveries.
• Jobs: Coral reefs provide job opportunities for fishers. About half of federal fishers rely on coral reefs for their job and contribute about $100 million to the U.S. economy. On a smaller scale, the local economy gains millions of dollars from visitors through diving tours, fishing trips, and nearby businesses (National Ocean Service).
• Tourism: The bright colors of coral reefs attract multiple tourists to coastal areas. About 80% of all tourism happens in coastal regions, and over 350 million people visit coral reef coasts each year (Sustainable Travel International). Many activities for tourists can be hosted in coral reefs, including diving, whale watching, and sport fishing.
• Coral reefs are vital for marine life and its health. They also provide various benefits for humans worldwide. It is up to us to protect coral reefs so future generations can continue to enjoy the benefits presented by corals.

Citations

Coral Reef Alliance. “Food - Coral Reef Alliance.” Coral Reef Alliance, Sept. 2021, coral.org/en/coral-reefs-101/why-care-about-reefs/food/#:


Florida Museum. “Geographical Distribution.” South Florida Aquatic Environments, 2024, www.floridamuseum.ufl.edu/southflorida/habitats/corals/geographical-distribution/#:


Joyce, Christopher. “NPR Choice Page.” Npr.org, 25 Jan. 2018, www.npr.org/sections/thetwo-way/2018/01/25/580227045/plastic-pollution-is-killing-coral-reefs-4-year-study-finds.


National Geographic. “Coral Reef Food Web.” Education.nationalgeographic.org, 4 Aug. 2024, education.nationalgeographic.org/resource/coral-reef-food-web/#.


National Ocean Service. “In What Types of Water Do Corals Live?” Noaa.gov, 2024, oceanservice.noaa.gov/facts/coralwaters.html#:


Press Books. “Symbiotic Relationships in the Coral Reef Ecosystem.” Pressbooks.pub, Pressbooks, 2024, https://pressbooks.pub/tropicalmarinebio/chapter/mutualism-in-coral-reef-ecosystem-mutualism-in-coral-reef-ecosystem/#:


Sustainable Travel International. “How Coral Reefs Support Local Communities.” Sustainable Travel International, Sustainable Travel International, 5 Nov. 2019, sustainabletravel.org/coral-reefs-local-communities/#:


US EPA. “Threats to Coral Reefs.” US EPA, 30 Jan. 2017, www.epa.gov/coral-reefs/threats-coral-reefs#:~:text=Increased%20ocean%20 temperatures%20and%20 changing.