American Oceans

The Different Types of Ocean Plants

Ocean plants are found in saltwater all over the world. The unique vegetation is famous for divers to search out for its beauty, although every one of us benefits from marine plants.

ocean plants

We may not come across sea plants in our day-to-day lives, but the oxygen they provide is crucial for the ecosystem and, in turn, us.

There are several types of underwater vegetation, all of which have their distinctive characteristics and benefits. Some plants are edible and provide health benefits, while others help maintain a balanced ecosystem.

Let’s discuss the different types of ocean plants and what they do for our planet.

What Is a Marine Plant?

A marine plant is a plant that grows under salt water but within reach of sunlight.

There are two main types of aquatic plants: algae and seagrass. Algae is an essential part of the food chain and vital to have a balanced ecosystem.

Marine plants are crucial parts of the environment for several reasons. They are food sources for aquatic animals and offer shelter to small fish.

Ocean plants also provide 70% of the Earth’s oxygen, making them crucial for human life.

Types of Underwater Ocean Vegetation

There are over 8,000 species of Plantae in the ocean waters that we know of.

Ocean plants fall into one of the following categories: phytoplankton, kelp, red algae, seagrass, and sargassum.

We will expand on the most common types of marine plants below to give you a better idea of what lies below the water’s surface.


Phytoplankton, or microalgae, are microscopic and invisible to the naked eye.


Like land plants, they contain chlorophyll and require sunlight to grow and survive. They also need inorganic nutrients, like nitrates, to convert into protein, carbohydrates, and fats.

Microalgae may be small, but they’re the foundation of the ocean’s food web. Aquatic creatures from zooplankton to sperm whales and everything in-between feed on phytoplankton. Without it, many marine species would struggle to survive.

Although they’re immensely beneficial for the environment, phytoplankton can also harbor diseases. They’re responsible for “red tides,” which can kill marine life and harm humans who eat the contaminated seafood.


Kelp is an enormous brown seaweed growing in shallow coastal regions worldwide.

People with various diets enjoy eating kelp for its flavor and health benefits. You can eat it cooked or raw or find it in supplements, sushi, sauces, salads, and more.

Sea vegetables like kelp are excellent sources of Vitamin B, iron, zinc, iodine, and omega-3s. They’re fast-growing marine plants that feed not only humans but are a primary food source for various ocean creatures as well.

Additionally, seaweed farming is one of the most sustainable practices in the aquaculture world. Because it removes carbon dioxide during its rapid growth, it helps balance nutrient levels in the surrounding water.

Red Algae

Red algae, or Porphyra, is one of the oldest non-bacterial photosynthetic organisms on the planet, surviving millions of years.

Red Algae

This species plays a significant role in building coral ecosystems by attracting larvae (feeding reef animals) and growing over breaks in coral skeletons.

As the name suggests, red algae come in shades of red or purple and may be slimy or hard like coral. It gets its magnificent colors because of the pigment phycoerythrin, which reflects red light and absorbs blue light. This plant can grow in places other marine plants can’t, deep in the ocean.

Like kelp, there are types of red algae commonly in foods. In Japan, it’s referred to as “nori,” which they use to wrap sushi.


Seagrass gets the name because most species feature green grass-like leaves.

Many confuse it with seaweed, though it’s more closely related to land plants. These flowering plants are the only species that can live entirely submerged underwater.

There are 72 marine seagrass species worldwide, and they belong to four different families: Posidoniaceae, Zosteraceae, Hydrocharitaceae, and Cymodoceaceae.

Seagrasses anchor to the ocean floor and get nutrients from their roots. Therefore, seagrass can only grow along coastlines in shallow waters to ensure it gets enough sunlight and nutrients from the ground.


Sargassum is a brown macroalga, a type of seaweed abundant in the ocean.


It features stems with leafy appendages and round berry-like air bladders, referred to as pneumatocysts.

The pneumatocysts are filled with oxygen, allowing the plant to float on the water’s surface. Once the pneumatocysts lose their buoyancy, the sargassum sinks to the ocean floor, providing carbon to deep sea creatures.

Because you can typically find sargassum in shallow waters, it provides food and shelter for marine life like crabs, birds, sea turtles, fish, and shrimp.


Sea anemones have a similar shape and appearance to the anemone on a flower.


They may be mauve, purple, pink, red, or white and change colors throughout the seasons.

As close relatives of jellyfish and coral, anemones are stinging polyps with venomous tentacles. They use their venom to trap small fish or plankton to feed on.

Anemones are well-known for their relationship with clownfish, which have a layer of mucus that protects them from the anemone’s sting. In return, the anemone can eat the clownfish’s food scraps.

Sea Whip

Aptly named, sea whips are soft corals that look like tangles of red or yellow ropes when they wash up on the shore.

Sea Whip

They look like long, grassy branches extending upward up to two feet tall in the water.

Despite their appearance, this species is actually an animal, not a plant. Sea whips are suspension feeders and eat small fish or plankton as it passes by them. As filter feeders, sea whips aren’t photosynthetic.

Sea whips have grown in value over time, and there’s growing concern about overfishing and overharvesting of this species in the Caribbean. Harvesting may also be harmful to the environment around the sea whips.


Corals are marine invertebrate animals that are either soft or hard corals.

yellowish-brown elkhorn coral in caribbean sea

Soft corals, like sea whips mentioned above, typically resemble trees or plants and are bendable. On the other hand, hard corals, like staghorn coral, have skeletons made of a hard substance called calcium carbonate.

Hard corals, or reef-building corals, grow in colonies and consist of thousands of individual animals called polyps. The polyps feed on small animals for food, which enters their separate stomachs and is then expelled through the same opening.

Not only are coral reefs attractive to look at when snorkeling or scuba diving, but they are also beneficial to the environment. They provide shelter for several species in the ocean.

Add comment