The ocean is one of the last unexplored frontiers, one of the last places filled with mysterious, undiscovered flora and fauna. One thing we do know is that there are two main types of plant life in the ocean: flora that takes root in the sea floor and those plants that are simply free-floating. Every day, scientists and oceanographers are learning more about the different varieties of both types of plants.
Phytoplankton are tiny, microscopic plants that float in almost all areas of the ocean. Individually, these tiny plants are invisible to the naked eye. However, their effects can be seen. Like their plant counterparts on land, phytoplankton rely on things such as sunlight and carbon dioxide for survival; they also utilize various nutrients from the ocean itself. When those nutrients (like iron) are absorbed by the phytoplankton in abundance, the tiny plants can take on various hues; this is why the ocean can sometimes appear different shades of greens, blues, purples and even reds.
Since phytoplankton require a number of different nutrients to thrive, they are also dependent on cold ocean water and an ever-changing, healthy tide and deep currents to keep renewing their food sources. Because of this constant need, monitoring the phytoplankton in an area can provide valuable information about the state of the deeper parts of the oceans and the surrounding environment.
Phytoplankton is one of the basic building blocks of life in the ocean, as it is a major food source for both small and large fish as well as some whales.
Seaweed is actually a large form of algae that grows only in the oceans. Like their smaller counterparts the phytoplankton, they also get their nutrients from sunlight, the air and the water currents. Because of this, they have no need of roots or any similar structure that would allow them to pull nutrients from the soil. They do, however, grow only near the shorelines and occur in a number of different colors, including greens, browns and reds. Currently, more than 5,000 species are known worldwide.
Also like phytoplankton, seaweed is one of the most basic components of the food chain, consumed by many fish and mammals.
Seaweed is used in a number of everyday objects, often as a dye or emulsifier. For many coastal nations, seaweed is a dietary staple as it is rich in vitamins and minerals. Some Pacific nations consider seaweed a main vegetable.
Seagrasses are exactly what their name suggests--slender, long-bladed grasses that have taken root on the sea floor. Most seagrasses (with some exceptions, such as Johnson's seagrass), reproduce in the same way many terrestrial plants do, via pollination.
Seagrasses are found in the coastal regions of the oceans, where they serve as a valuable habitat for many marine creatures from fish to manatees and sea turtles. The grasses provide shelter, hiding places and food for many creatures. Different varieties of seagrass have different tolerances to water temperature and salinity.
Some types of seagrasses, like Johnson's, are considered endangered, and conservation efforts are under way. Because of their proximity to coastlines, these plants are vulnerable to conditions such as erosion, toxic runoff, dredging, sedimentation and damage from boats.