5 Underwater Working Relationships

Have you ever thought of the ocean as a workplace, where everyone fulfills certain tasks and responsibilities to keep a healthy, harmonious environment and relationships by working as a team?


A coral reef is a complex and wondrous ecosystem, with new exciting discoveries every day. As scuba divers we are fascinated watching life going about its daily schedule, life working together to thrive in a colorful city of coral.


Here are 5 surprising fun facts about marine animals collaborating with plants, algae, each other, and the reef at large.

1. Damsel Fish Farmers

A nip on your finger. Another tug on your fin. If you’ve been swimming close to the reef, you are likely to have experienced a small angry fish. Damselfish are fierce when it comes to protecting their territories, and no matter how big you are, they won’t stand for your trespassing.

They live in mutualistic relationships with turf algae in which they farm in small patches for food. And like any good farmer they care and protect their crop. They weed diligently, plucking unwanted algae and carrying it away from the area. They also ferociously chase off any invading predators such as parrotfish and urchins, charging and nipping at the invader. 

Both the Damselfish and algae benefit from this relationship, as the Damsel has a good supply of food and the algae is protected from over grazing and invasive species. 

Moreover, Damselfish lay their eggs inside this territory. You can see them fluttering just over them, aerating the eggs with their fin and mouths. During that time, the damselfish do undoubtedly up their security!



2. Sea Slugs + Prey Cells = Beauty & Diversity

Do you remember that beautiful photo of a Lettuce Sea Slug (Elysia crispata) from our February newsletter and blog «10 Awesome Creatures of the Caribbean«? 

They are so named for their iridescent ruffles and green colorings, but can you guess how they get their green color? You might assume that they turn green after consuming green algae. This is partly true, though most likely not in the way you may think. 

Some species of sea slugs (sacoglossans) don’t digest all of their food, but move some of those cells – the chloroplasts – into those ruffled appendages (parapodia), where they are able to maintain their functionality – the photosynthesis – and store them for weeks if not months in large transparent digestive glands, turning them into beautiful shades of green. For this reason, this species is also known as solar-powered sea slugs.

Not only does the Lettuce Sea Slug resemble lettuce but it actually uses those ruffles like leaves to provide a large surface area for light capture to produce energy via photosynthesis. This is the ultimate way to eat an eco-friendly slow burning diet!

This slug is not alone in using its meal for more than just food. Redistributing and reusing it preys cells in parts of its own body. Other of its relatives use nematocysts (tiny stinging structures) taken from eating such animals as anemones and hydroids. They manage to eat their prey without discharging all of the stinging cells, and relocate them into their skin, where they continue to function, using them to sting and ward off predators. 


3. Mesmerizing Cleaning Stations = Hygiene + Full Bellies

Cleaning stations are a brilliant example of marine collaborations. If you were lucky to see one in action, this experience will be burnt into your memories forever. Large fish coming close into the reef for some thorough grooming and maintenance work are swarmed by smaller cleaner wrasse, juvenile fish and other creatures to win a meal. The usual rules of predation are suspended, as fish get together for their mutual benefit. 

For some fish and shrimp, cleaning provides a major food source throughout their lives, while others take advantage of this dining opportunity just during their juvenile years. 

Each species focuses on a different cleaning job. Certain gobies feed on tiny parasites, while some shrimp actually jump into the mouth of fish to clean out its gills. Banded Coral Shrimps with their larger claws are great at cleaning out the larger bits of debris stuck between teeth. Working together they offer a full service.

Groupers can spend up to eight hours a day getting fussed over at cleaning stations. Turtles, rays, sharks and eels belong to the frequent visitors. 

Watch for the larger fish’s behavior as it indicates that it wants to be cleaned. They go close up to the station, often hanging mid water at a strange angel, some even changing in color or pattern to gesture their desire to be cleaned by the smaller fish.




4. Coral + Algae = Colorful Coral

Most hard and soft corals live in symbiosis with an algae called zooxanthellae. Up to 95% of the coral’s food is provided by the algae’s photosynthesis. The rest is actively caught from the water by the coral’s tentacles. The algae benefit from a safe place to live and get to consume the corals carbon dioxide and nitrogenous waste.

As much as 30% of the coral’s tissue can contain zooxanthellae, as many as 8 zooxanthellae per cell, which gives the coral its color. There are many types of zooxanthellae. Each coral chooses to house a different one and therefore creates the rainbow of coral colors that we see.

This relationship is vital to the corals’ survival. Without the zooxanthellae the coral would starve. Coral bleaching is the mass expulsion of a coral’s zooxanthellae due to stress; hence the name bleaching, as they lose all their color as the algae leaves. This can happen due to elevated temperature and high light levels. If conditions return to normal relatively quickly, corals can regain their zooxanthellae and survive. 



5. Algae + Parrotfish Poop = Beautiful Sand Beach

Our favorite fun fact. Did you know that it is estimated that more than 80% of the beautiful white sand you are laying on is parrotfish poop! The famous white-sand beaches of the Caribbean actually contain a large portion of it. 

The parrotfish feeds off algae growing on rock and dead coral, as they bite and scrap off the algae with their strong beak-like teeth, they also grind up the rock passing it through their systems and pooping it out as a fine white sand. 

Parrotfish can produce hundreds of pounds of white sand each year. Researchers found that the Caribbean small striped parrotfish (scarus croicensis) can produce up to six pounds of sand a year. Remarkable considering the striped parrotfish is usually only about six inches long. And researchers working in the Maldives found that the 28-inch Steephead Parrotfish can produce a whopping 900 pounds/ 410 kg of sand per year!!! 

Their diligent crunching is an important relationship between the fish and reef, helping to maintain a diverse coral ecosystem and keep algae growth in check. Keeping a healthy home for many creatures. 

Listen carefully on your next dive to hear their powerful crunching and watch for the long white streams of poop hanging in the water. 


This is just a handful of unexpected underwater relationships. Which one did you like the most? Got some exciting ones to share with us for one of our next blogs? Write to our team at marketing@prodiveinternational.com!


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