• Kelp forests are a home to marine life.Paul Souders/Photodisc/Getty Images
  
  The ocean is a complex environment that is home to many types of plant species. Plants found in the ocean provide a basic source of food and shelter for marine life. The kinds of plants found in the ocean are of two basic types: those that have roots and those that do not.
  
  

Seaweed

• Seaweed is an ocean plant that has roots to attach to the ocean floor. According to the Ocean Link website, the root in seaweed is called the holdfast. Seaweed is a kind of algae, which is part of the Kingdom Protista, and Class Phaeophyceae. Seaweed is neither truly a plant or animal. However, like plants, it can perform photosynthesis, giving it green pigmentation in addition to any other pigments the plant has. Seaweed has a stem called a stipe and a gas-filled chamber called a float that keeps it buoyant. Seaweed may be very small, or it may grow to as long as 30 yards.
  
  

Seagrass

• The Seagrass Watch website states that seagrass belongs to the angiosperm category, meaning that it is a flowering ocean plant. Found rooted on the ocean floor in coastal areas, seagrass provides an important component of the habitat for coastal marine wildlife. It also helps to support the balance in coastal waters by preventing erosion and providing food to animals.
  
  

Phytoplankton

• According to NASA's Earth Observatory website, phytoplankton are free-floating, single-celled plants found throughout the ocean. Phytoplankton use photosynthesis to produce nutrients, but depend heavily on the nutrients found in the ocean water around them. When phytoplankton are in ideal conditions, they rapidly reproduce and grow, creating a large "bloom" that is visible on satellite images. Phytoplankton live only for a few days.
  
  

Kelp

• Like seaweed and algae, kelp belongs to the Kingdom Protista. Kelp is known for its large blades that twist together to form large kelp forests. Depending on the region where kelp grows, it can have a green or brown color. Kelp forests provide a safe habitat for many types of marine life.
  
  

Red Algae

• Red algae has a pigment called phycoerythrin that gives it a bright red color. Because of this pigment, red algae can live at lower depths than other algae as it does not need as much light for photosynthesis. This type of algae also forms an important part of Asian diets as it contains significant amounts of protein.
  
  

Coralline Algae

• Coralline algae grow on coral reefs and help the coral reefs to hold their structure together. Coralline algae differs from other algae in that it calcifies, or hardens, to form a tough structure as part of the coral reef. This calcification is due to the calcium carbonate found in coralline algae.