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The underwater world is a marvelous one, consisting of over 70% of the earth’s surface. While the majestic, pelagic fish like manta rays and sharks leave us gasping in awe and the colorful reef fish tell the story of an underwater city, we often overlook one of the most important aspects of the marine world: PLANTS!
Although nature will always find a way, it is currently known that marine life would simply not exist without aquatic plants. And because they provide the Earth’s atmosphere with about 50% oxygen and absorb about 25% of the carbon dioxide, we above-ground dwellers are also likely to have a very hard time.
In this blog post, we’ll take a closer look at these unsung heroes of the underwater world and learn about the most common ones!
What is an Ocean Plant?
An ocean plant is an aquatic plant that is adapted to living in seawater. Like terrestrial plants, (that live on the earth’s surface), they survive on a process called photosynthesis, which is basically using sunlight and chlorophyll to turn water and carbon dioxide into nutrients on which they rely.
Fun Fact: Photo means “light”, and synthesis means “put together”!
Unlike their terrestrial counterparts with roots that absorb nutrients from the ground, ocean plants get the good stuff from the waters around them. Instead, their roots anchor them to the seabed of corals, rock formations, or sand, to stop them from floating freely.
The amount of sunlight that can penetrate water is significantly reduced at depth, which is why most ocean plants are found in shallow reefs and not deeper waters. However, nature is wonderful, and many plants have since evolved to metabolize bicarbonate ions as a source of carbon instead.
Common Types of Ocean Plants
There are over a million species of underwater flora! However, they can be broadly classified into a few categories.
Phytoplankton
These little microscopic algae are the foundation of the oceanic food chain. Not only do they provide food for a vast number of marine species, but they also provide oxygen and absorb carbon dioxide.
There are two main types of phytoplankton: diatoms and dinoflagellates. Diatoms are single-celled algae that are mainly responsible for food and oxygen production while dinoflagellates cause bioluminescence, the fantastic greenish or bluish lightshow you see in some marine environments.
Seaweeds, also called Macroalgae
There are numerous species of seaweeds, and they typically fall into one of three categories: kelp, red algae, and green algae.
Kelp is the long, brown seaweed commonly found in underwater forests. Not only does kelp provide shelter and food for many species, but it also reduces the impact of strong winds and waves, protecting the shoreline from erosion. Two common species of kelp are Giant Kelp (Macrocystis pyrifera) and Bull Kelp (Nereocystis luetkeana).
Red algae, also known as Rhodophyta, are red because of a pigment called phycoerythrin, allowing the plants to survive in deeper waters by absorbing blue light and reflecting red. They contribute to the formation and stabilization of reefs and also support the marine world by supplying food and shelter.
In recent times, green algae, or Chlorophyta, has shot to the limelight as a superfood and common supplement ingredient. Species like chlorella and spirulina are harvested for their nutritional benefits and others are studied as potential sources of fuel. Underwater, green algae plays a crucial role in providing habitat and food, as well as producing vast amounts of oxygen.
Seagrasses
Seagrasses are found in shallow coastal waters, forming dense, underwater meadows that provide habitat and food for marine life. They are also often nursery grounds for larger fish as the vulnerable shelter from other predators.
Seagrasses have roots, stems, and leaves, helping stabilize sediment and prevent land erosion. They play a huge role in capturing and storing carbon, making them crucial to mitigating climate change.
Mangroves
Mangroves are an interesting group of trees and shrubs that have evolved to thrive in salty environments. While most of the plant grows above the water, the specialized root systems remain underwater, providing stability to soft, muddy seabeds and reducing erosion. They also provide the surrounding environment vital protection against strong winds, waves, storms, and tsunamis.
Mangroves are rich habitats, nurseries, and breeding grounds for many species, both terrestrial and aquatic like insects, fish, birds, and crustaceans.
Sargassum
If you’re walking along the beach and see a bunch of seaweed-like looking plants that have little bubbles in them, chances are, that’s sargassum! This genus of seaweed floats freely on the ocean’s surface and provides valuable food and shelter for many marine species, serving as nurseries for young organisms and protecting them from predators.
Ocean Plants: Frequently Asked Questions
Are there plants in the deep ocean?
Like terrestrial plants, underwater plants need sunlight for photosynthesis, which is why the majority of plants are found at shallower depths where light can still penetrate. Blue light penetrates water best, and as red and brown algae can absorb blue light, they can be found at greater depths.
How do plants survive in the ocean?
Unlike their terrestrial (land-dwelling) counterparts, ocean plants do not get their nutrients from their roots. Instead, they get them from the surrounding waters. In addition, they absorb sunlight and convert them to carbon dioxide and nutrients in a process called photosynthesis.
Final Thoughts
Ready to check out some cool plants? While snorkeling is a fun way to see them, the way to go is scuba diving, where you can get up close and personal with these underwater superheroes.
Because kelp and other sea plants can get you tangled, be sure to take a scuba knife to cut yourself free if necessary, and a scuba light to bring out colors and see better in a dark environment. Try not to touch anything but if unavoidable, be sure to handle any aquatic plants with diving gloves to protect your hands from stings and abrasions. If you have difficulty identifying the plants, you can use an underwater camera like a GoPro to keep an accurate record and confirm their identity once you’ve reached the surface.
