If you look around you in nature, you will be surprised to learn that thousands of creatures live happily in symbiotic relationships. They are so prevalent that even humans coexist with bacteria.
Symbiosis is also a common phenomenon in the ocean. Many marine organisms depend on symbiotic relationships to survive. Symbiosis, thus, refers to long-term interactions of organisms of different species.
There are three common symbiotic relationships in the ocean. They include mutualism, commensalism, and parasitism.
Mutualism is a symbiotic interaction in which both species benefit. In commensalism, one organism benefits, while the other neither benefits nor is harmed. Parasitism, on the other hand, is a symbiotic relationship whereby one species benefits at the expense of the other.
Below is a list of the most common symbiotic relationships in the ocean.
Sea Anemones and Clownfish
Habitat: Sea anemones are mainly found in shallow tropical waters where they live in close association with clownfish.
Type of relationship: Sea anemones and clownfish have a mutualistic symbiotic relationship.
One of the most common symbiotic relationships in the ocean is the interaction between sea anemones and clownfish.
Sea anemones are stationary predators that catch passing prey with their stinging tentacles. Clownfish, on the other hand, are small, brightly colored fish that live in the tentacles of the sea anemone.
The clownfish are immune to the sea anemone’s stinging cells, providing them a safe place to live and lay their eggs. The clownfish also consume the leftover bits of food from the sea anemone’s meals.
The sea anemone, in turn, benefits from the clownfish’s presence by receiving protection from predators. The clownfish chase away polyp-eating fish and even parasites that could harm the anemone. The clownfish also aerate the water around the anemone by swimming in and out of its tentacles, which helps circulate oxygen.
This relationship is a perfect example of mutualism, where both species benefit from each other.
Pistol Shrimp and Gobies
Habitat: Gobies and pistol shrimp inhabit shallow marine habitats such as seagrass beds, coral reefs, and muddy estuaries.
Type of relationship: Gobies act as lookouts for pistol shrimps and alert them of potential predators. In return, the pistol shrimp provide a safe burrow for both species to live in, thus creating a mutualistic relationship.
Another example of mutualism in the ocean is the relationship between pistol shrimp and gobies.
Pistol shrimp are small crustaceans that burrow through the muddy and sandy sea floors looking for food. They have very poor eyesight, and the goby fish guards the shrimp as it digs the burrows. The goby fish, on the other hand, has excellent eyesight and can spot predators from a distance. When the Goby fish sees a predator approaching, it flicks its tail to warn the shrimp, which retreats into the burrow.
In return, the shrimp allows the goby to access its burrows, thus providing the goby fish a safe place to live, hide from predators, and lay eggs.
Coral and Zooxanthellae
Habitat: Coral reefs are mainly found in shallow, warm tropical and subtropical waters around the world.
Type of relationship: These tiny single-celled algae live inside the tissues of the coral, where they provide the coral with vital nutrients through photosynthesis. In turn, the coral provides algae with a safe place to live and access to sunlight, thus creating a mutualist relationship.
Coral is a marine invertebrate and is the foundation of coral reef ecosystems. Coral reefs are some of the most biodiverse ecosystems on the planet and provide habitat for countless marine species. The relationship between Coral and Zooxanthellae is an example of mutualism, where both species benefit from the interaction.
Zooxanthellae are single-celled algae that live within the tissues of coral polyps. They provide the coral with essential nutrients through photosynthesis. In return, corals provide zooxanthellae with a safe place to live and access to sunlight for photosynthesis.
The zooxanthellae also get carbon dioxide and other nutrients from the coral for photosynthesis. Besides, zooxanthellae also give corals their vibrant colors, which draw other marine species to the reef.
Notably, coral reef ecosystems are only as healthy as their relationships with zooxanthellae, thus one of the most well-known common symbiotic relationships in the ocean.
Decorator Crab and Sponges
Habitat: Decorator crabs and sponges are commonly found in shallow waters in coral reefs and rocky intertidal zones.
Type of relationship: Decorator crabs attach sponges to their exoskeleton, allowing them to blend with their surroundings. In return, sponges benefit from being transported to new locations, enhancing their chances of survival, thus creating a mutualistic relationship.
Another fascinating common symbiotic relationship in the ocean is between the decorator crab and sponges. The decorator crabs are the ultimate masters of camouflage. To enhance their survival, they attach different environmental materials to decorate their bodies. These materials include rocks, seaweed, and, most importantly, sponges.
The crabs pluck small pieces of sponges and attach them to their exoskeleton. This helps them blend in with their surroundings and avoid predators. The sponges, in turn, continue living on the crab’s shell. As the crab moves across the sea floor, the sponges benefit from being transported to new feeding areas. In this relationship, both individuals benefit.
Sharks and Pilotfish
Habitat: They are pelagic species commonly found in warm tropical and subtropical waters around the world.
Type of relationship: The sharks and pilot fish have a mutualistic relationship. The pilot fish gets protection from predators, while sharks enjoy freedom from parasites.
Pilotfish are small fish often seen swimming close to sharks, especially the larger species such as the whale, great white, and tiger shark. They have a sleek, streamlined body and are about the size of a person’s hand.
The pilot fish benefit by getting protection from predators and a steady supply of food on food scraps left behind by the shark. In return, pilot fish remove dead skin and parasites from the shark’s body, including the gill area. In doing so, it acts as a “cleaner fish, reducing the shark’s risk of infection and disease.
Further, pilotfish are also known to alert sharks of potential prey, which benefits the shark and allows the pilotfish to feed on the scraps left behind. In some cases, pilotfish also help the shark to hunt more effectively. They do this by creating a distraction that enables the shark to sneak up on its prey without being noticed.
The sharks refrain from feeding on pilot fish because they recognize the advantages of having them as close allies. Their relationship is thus a perfect example of how different organisms can effectively work together for their mutual benefit.
Remoras and Turtles
Habitat: Although the preferred habitat for turtles varies depending on the species, sea turtles are found in the world’s oceans except in the icy polar regions.
Type of relationship: Remoras hitch a ride on turtles shells. This enables them to access new food sources and also save energy. On the other hand, the turtle neither benefits nor is harmed by the remoras, thus a commensal relationship.
The interaction between remoras and turtles is another common symbiotic relationship in the ocean. Remoras, also known as suckerfish, are small fish with specialized suction discs on their heads. They use this disc to attach themselves to larger marine animals like sea turtles and manta rays.
Turtles provide remoras with food and protection. By attaching themselves to the turtles’ shells, remoras access food remnants that the turtles leave behind or stir up from the ocean floor when foraging. In addition, they also hitch a ride, allowing them to travel long distances without using much energy.
Although their relationship is more commensalism, it can also be considered mutualistic in some cases. This is because when on the turtle’s back, remoras feed on parasites and dead skin, keeping the turtles clean and healthy.
Whales and Barnacles
Habitat: They inhibit all of the world’s oceans, from tropical and temperate waters to Arctic and Antarctic zones.
Type of relationship: This relationship benefits the barnacle by providing it with a place to live and a way to get food. The whale is unaffected and does not benefit from this association; thus, a commensal relationship.
Adding to our list of common symbiotic relationships in the ocean is the commensal interaction between whales and barnacles. In this relationship, barnacles benefit from whales, while whales are neither helped nor harmed by the presence of barnacles.
Barnacles are small crustaceans that use an adhesive to attach themselves to the skin of whales. While on the whale’s skin, barnacles feed on plankton and other small organisms attracted to the whale’s movements. This provides barnacles with a source of food.
The whale also offers bernacles with protection from predators and a sturdy surface to reside on. On the other hand, whales can support thousands of barnacles at a time and are not affected by their presence.
Sea Cucumber and Emperor Shrimp
Habitat: Sea cucumber and emperor shrimp are benthic organisms living on the ocean floor. They occur in all depths, from shallow waters to deep-sea environments.
Type of relationship: The emperor shrimps grip tightly onto the sea cucumbers and uses them as a means of transport. The shrimp does not benefit nor cause any harm to the sea cucumber, thus a commensal interaction.
Featuring another common symbiotic relationship in the ocean is the commensal interaction between sea cucumber and emperor shrimp. Emperor shrimps use sea cucumbers as a mode of transport. They tightly hold onto the sea cucumber as it travels across the ocean floor.
As a result, they are transported to various food sources while using as little energy as possible. The emperor shrimp occasionally climbs down from the cucumber to look for food. After a while, they climb back up and continue their journey to the next feeding location.
This symbiotic relationship is particularly fascinating because the shrimp actively seek out sea cucumbers to form a partnership with. They will even fight other shrimps for a chance to work with a sea cucumber. Sea cucumbers do not benefit from this relationship, and neither are they harmed.
Fish and Sea Lampreys
Habitat: Although they are native to the Atlantic Ocean, sea lampreys live in both freshwater and saltwater.
Type of relationship: Sea lampreys are parasitic in their adult stage and suck the body fluids of their host fish. They benefit at the expense of the host fish, thus creating a parasitic relationship.
Unfortunately, not all interactions in the ocean get along well, especially parasitic relationships. At their adult stage, sea lampreys are parasitic and feed on the blood and body fluids of other fish species.
They do this by attaching themselves to their host, using their sucker-like mouth. They then rasp the skin of their hosts and drain all their body fluids.
Although they do not kill their prey, they feed on them until they are weak and then detach from them. After this, the host is usually severely wounded and eventually dies. Sea lampreys preferred hosts are salmon, herring, trout, and even some sharks.
In this relationship, sea lampreys benefit at the expense of the host fish, thus creating a unique common symbiotic relationship in the ocean.
Fish and Isopods
Habitat: There are over 10,000 species of isopods, with the majority inhabiting marine ecosystems, some freshwater and others living on land.
Type of relationship: Isopod eats off the tongue of a fish. It then replaces the tongue with itself and feeds on whatever the host fish eats. The host fish does not benefit from this interaction. Instead, he is damaged or even dies, thus creating a parasitic relationship.
The relationship between fish and isopods is parasitic and, impressively, one of the most common symbiotic relationships in the ocean.
Isopods are small parasitic crustaceans that attach themselves to a fish’s tongue. It sucks blood from the tongue until the tongue withers and falls off. It then replaces the tongue by attaching itself to the tongue stump.
Since it is now a part of the fish, the isopod consumes whatever food the fish ingests. The fish, in turn, loses its tongue and gets less food to eat. As a result, the host fish may get ill or starve to death.
Unlike commensal relationships, here, the isopod is the only beneficiary. The fish do not gain in any way but instead get hurt or, even worse, die.
How do symbiotic relationships in the ocean affect marine ecosystems?
The ocean’s symbiotic relationships are crucial to the health and balance of marine ecosystems. They support food webs, create new habitats, regulate nutrient cycling, and safeguard species
What are some potential threats to the ocean’s symbiotic relationships?
Overfishing, pollution, habitat loss, and climate change threaten ocean symbiotic relationships. These threats destabilize the ocean ecosystem’s populations and cause symbiotic relationships to break down or disappear.
Are sea lampreys harmful to humans?
Sea lampreys are generally not harmful to humans. While they have been known to attack humans, these incidents are uncommon and pose little threat to human safety.
Why are common symbiotic relationships in the ocean essential?
In symbiotic relationships, organisms of different species depend on each other for survival. They may share habitats or lifestyles or interact in ways that benefit from the presence of the other organism.