Our oceans are filled with innumerable, incredible plant species. Ten of these are included on this list of the strangest and most interesting marine plants. From kelp forests to algal blooms, the plants on this list are incredible features of our planet that are often overlooked.  

Kelp 

Large brown algae

Can grow up to 250 feet underwater

The long and strange Kelp Marine Plant
The long and strange Kelp Marine Plant

Credit: NOAA’s National Ocean Service, CC BY 2.0, via Wikimedia Commons

Kelp forests are well-known, beautiful underwater rainforests. They are the largest plants in the ocean and extremely fast-growing, perhaps the fastest of all plant species. Kelp has flotation bulbs that help them stay afloat on the surface of the ocean. They can be found in cool and tropical waters. They are usually brownish-green in color. The first likely appeared in the Miocene, 5 to 23 million years ago.

Kelp forests can be seen along the west coast of North American, where they live in shallow waters along the shoreline. They grow quite densely and provide a home for a wonderful variety of other plants and animals. The blades are used to shelter young, and the ocean floor around the forests provides a prime hunting ground for crabs, octopi, sharks, and more. 

Phytoplankton 

Microscopic marine plants

Require carbon dioxide to survive

The strange Phytoplankton marine plant is invisible to the eye
The strange Phytoplankton marine plant is invisible to the eye

Phytoplankton is microscopic Marin algae that are similar to terrestrial plants. They require sunlight to live and grow and are divided into two categories, dinoflagellates, and diatoms. They are the base of the marine food web and can be found in salt and freshwater. They have chlorophyll, like land plants, to capture sunlight turn it into energy. They also consume carbon dioxide and release oxygen. Their growth is dependent on the presence of carbon dioxide as well as other nutrients like nitrate, silicate, and calcium.

The water temperature, as well as the salinity, depth, and wind, can also impact their growth. Everything from zooplankton to whales feeds on phytoplankton. But, they can also be dangerous. Certain species create biotoxins, commonly associated with “red tides.’ These are algal blooms that are toxic to marine life and can greatly damage the food chain in a specific area. 

Surf Grass 

Provide habitat and food for nearly 70% of all sea life

Good nursery habitats for fish

Surf Grass

Credit: Peter D. Tillman

Surf grass is a kind of sea grass that exists in waters around or below the low tide line. 

It’s capable of pollinating at the surface or underwater. They’re an important food source for birds and any creature residing in a tide pool. It is native to the western North American coast, all the way from Alaska to Baja. 

Waterwheel Plant

An aquatic Venus fly trap

Does not have any roots

The deadly and strange Waterwheel marine plant
The deadly and strange Waterwheel marine plant

Credit: Daiju Azuma, CC BY-SA 2.5, via Wikimedia Commons

The waterwheel plant, also known as Aldrovanda vesiculosa, is the only living species of its genus and family. The plant is notable for its ability to trap small invertebrates, one of the only rapid moving plants on the earth. These traps are centered around a stem that floats freely and is made up of two lobes that snap shut, similar to how a Venus flytrap works. Unfortunately, populations of this plant have declined in the last years, with only 50 confirmed worldwide. They can be found all over the world, from Africa to Asia and Europe. The plant is popular with hobbyists, and there are thought to be some invasive species in the United States.

Sea Anemone

Tentacles with poisonous stingers

Can reach up to 6 feet in diameter

Sea Anemone - a weird predatory marine plant
Sea Anemone – a weird predatory marine plant

Bernard Spragg. NZ from Christchurch, New Zealand, CC0, via Wikimedia Commons

The sea anemone is a predatory animal. They are named after the terrestrial flowering plant of the same name due to their appearance. Anemones come in many different shapes and colors. Most species are made up of a polyp attached to a hard surface through a base, but some live in soft sandy areas of the ocean floor and a few that also float near the surface of the water. 

Sea Grass

Underwater flowering plant that requires sunlight to survive

Responsible for around 15% of whole ocean’s carbon dioxide absorption

The interesting Sea Grass marine plant
The interesting Sea Grass marine plant

Credit: Peter Southwood, CC BY-SA 4.0, via Wikimedia Commons

Seagrasses are a flowering plant of which there are about 60 species. Seagrasses have long stems with narrow leaves that, like Neptune grass, take up large areas on the ocean floor. These are often referred to as meadows or grasslands. They are sometimes made up of a variety of species or just a single species. They create productive ecosystems and provide homes to innumerable other species, such as fish and algae. 

Neptune Grass 

Creates a thick meadow on the bed

Very slow growing, but can live for a long time

The weird blue marine grass known as Neptune Grass
The weird blue marine grass known as Neptune Grass 

Credit: Alberto Romeo, CC BY-SA 2.5, via Wikimedia Commons

Neptune grass, or Posidonia oceanica, is also known as Mediterranean tapeweed. It is endemic to the Mediterranean Sea, where it creates large underwater “meadows.” The fruit floats freely in the water and the leaves, which are bright green, long, and ribbon-like. The plants are found between one and thirty-five meters in depth, or 3.3 or 114.8 feet. The species only lives in the Mediterranean Sea, where it is unfortunately in decline. Neptune grass grows in clear water and suffers from increases in pollution. One of the oldest colonies was found near the island of Ibiza, estimated at around 100,000 years in age. 

Mangroves 

Great habitat for nursery fish, due to their roots

Excrete salt through their leaves to survive salty water

The strange marine plant Mangroves
The marine plant Mangroves sits on the water with its roots

CC BY-SA 3.0, via Wikimedia Commons

Mangroves are interesting trees and shrubs that sit on water with long, propped up roots. They grow in coastal regions where water meets with the land. Some species live quite close to the ocean water, so much so that they are flooded/covered in water every day. Their roots have a complex filtration system that keeps out the dangerous salt. They are well-known for their ability to survive in challenging environments. Nowadays, despite their strength and evolutionary abilities, they are endangered due to human activities and the degradation of coastlines. 

Red Algae

Consists of around 6,000 different species

Used extensively for different medical applications

The unusual looking Red Algae
The unusual looking Red Algae

Credit: John Martin Davies, CC BY-SA 3.0, via Wikimedia Commons

Red algae are among the oldest groups of eukaryotic algae and are numerous in ocean habitats but rare in freshwater (only 5% are found in freshwater). Red algae are rich in protein and vitamins and are often consumed in Asian countries. It has existed on earth for more than 500 million years, and the color is a result of the masking of chlorophyll by phycobilin pigments, as described by Britannica. Their pigment absorbs blue light and reflects red. Some appear green or blue rather than red, depending on how much phycoerythrin they contain. 

Sargassum

Floats on the surface of the ocean

There is an area of the ocean that contains 2 million square miles of Sargasso

The Sargassum comes in abundance across the ocean
The Sargassum comes in abundance across the ocean

Credit: James St. John, CC BY 2.0, via Wikimedia Commons

Sargassum is also known as gulfweed and sea holly. It’s a floating marine plant that is brown and green in color. It’s dense and bushy with “bladders” that help keep it at the water’s surface. The proximity to the sun improves its ability to photosynthesize. They form large floating masses and are distributed throughout the temperate and tropical oceans. The plant is sometimes used as a herbal remedy. 

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