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The Never-ending Grandeur of Oceans

Updated: Dec 21, 2023

The marine biome is the world’s largest biome, covering 75% of the earth’s surface and include oceans, coral reefs, and estuaries (where the ocean meets fresh water). Oceans, in particular, are the largest ecosystems, with the Pacific Ocean extending beyond 64 million sq. miles. They can also be described as a continuous body of salt water--did you know that oceans hold about 1 cup of salt for every gallon of water? Nonetheless, this incredible biome is home to an astonishing, assorted group of species that include marine mammals, corals, cephalopods, crustaceans, sea turtles and other reptiles, sea birds, sharks and rays. What is even more amazing is that each of these creatures and plants has adapted to life in the ocean based on the biome’s physical diversity called zones. “Dive in” to find out more about the plethora of phenomena that exists in oceans.

Coral Reef. Photo: Unsplash/Delbert Pagayona

Physicality of Oceans

Even though the ocean contains fewer species than there are on land, oceans contain the most diversified of species because of how the ocean is physically divided. The ocean contains 4 distinct “zones” based on how far light reaches into the water: intertidal, pelagic, benthic, and abyssal zone. Due to the different amounts of lights that reach each of these depths, each zone has a discrete group of species that has adapted to the conditions there. The intertidal zone is the region closest to the shore, where the ocean meets the land. Here, there is a constant cycle of tides and waves (hence, the name), leaving some areas submerged with water and other areas high and dry. Because of this variability, the types of organisms present in this zone are dependent on the tides. Algae and mollusks, snails, crabs, and sea stars tend to exist where the highest tides reach, whereas seaweed and fish can be found in the lowest tides. In the dry areas, the exoskeletons of crustaceans help protect them from drying out and wave damage. The pelagic zone refers to the open ocean. Since sunlight hits the surface of this zone, there is a mixing of warm and cold ocean currents. This zone is home to surface seaweed, plankton, whales, and dolphins. The benthic zone is located directly underneath the pelagic zone in shallow regions. Since less sunlight penetrates to this region, the temperatures get colder and species found here are mainly seaweed, bacteria, fungi, sponges, and worms that have adapted to the specific conditions. This region also has the highest nutritional content because of dead organisms that fall from the top of the ocean. Lastly, the deepest part of the ocean (depths of 4000m or more) is the aptly named abyssal zone. These depths are very cold with low nutritional content (since sunlight does not penetrate to these depths), however, contain high amounts of pressure and oxygen. Because of the lack of sunlight, photosynthetic organisms do not survive here and namely include invertebrates and fish.

Bee Pollination
Ocean Depths. Photo: Unsplash/Marek Okon

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Endangered Ocean Species

With oceans being so physically diverse, it is no wonder that this biome supports such a diversified biotic community. Unfortunately, due to overfishing, pollution, and global warming, ocean species are at risk. Conservation groups like Oceana, U.S. Fish and Wildlife Service, and National Marine Fisheries Service are taking enormous strides in the preservation of marine flora and fauna. Here are 3 less common endangered marine species that you should know:

1. Dugong: Dugongs may look like a manatee twin, but they are quite a different creature. These animals are friendly, gentle, herbivores, and can reach almost 700 pounds at maturity.

2. Bluefin Tuna: Some consider this species as the most valuable fish and is critically endangered, with fewer that 25,000 left in the wild mainly due to overfishing and loss of prey.

3. Humphead Wrasse: Also known as the Napolean fish, the Humphead Wrasse is characterized by the prominent “hump” on its forehead, big lips, and 2 thin horizontal lines behind its eyes. They are found in the Indo-Pacific region, within the tropical and subtropical waters. Interesting fact: these fish are hermaphrodites, meaning they are able to change from one sex to another during maturation.

Humphead Wrasse
Humphead Wrasse Photo: Unsplash/David Clode

Coral Reefs

Coral reefs are largely found in warm, shallow waters and along barriers of continents. Perhaps the most well-known coral reef is the Great Barrier Reef off of Australia. Corals may look like plants, but they are actually a hybrid of algae and animal tissue made of hundreds to thousands identical “polyps” to form a colony in the ocean. Since the nutritional content here is low, corals absorb nutrients through the algae by ways of photosynthesis and plankton. Corals are also protectors of the ocean--they form barriers to protect the shore from waves, preventing damage and loss of life.

Rusty Patched Bumble Bee
Colony of Corals. Photo: Unsplash/Q.U.I


Estuaries is where the convergence of freshwater with the ocean occurs, resulting in a mixing of waters with different salt concentrations. Due to this unique ecosystem, another set of diversified species exist here like marsh grasses, mangrove trees, oysters, and waterfowl.

Mangrove Trees
Mangrove Trees. Photo: Unsplash/Kon Karampelas

How to Support our Oceans

With so much diversity in our aquatic ecosystems, we can all do our part in helping keeping oceans clean and protected. Some easy ways we can contribute include:

1. Reduce plastic waste by using a re-usable water bottle

2. Conserve water by turning off faucets so excess doesn’t flow into the ocean

3. Reduce pollutants by choosing nontoxic chemicals and dispose waste responsibly

Did You Know?

Do you know how many oceans are there in the world? If you guessed 5, you would be correct! They include Pacific, Atlantic, Indian, Arctic, and Southern in addition to smaller Gulfs and Bays.


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