Ocean Plants

A Brief Look At The Major Types Of Ocean Plants


The number of different species of ocean plants is understandably much smaller than is the number and variety of plants and plant life found on dry land. The primary reason for this is that plant life, whether it exists in the ocean or on land, needs sunlight to survive. Sunlight can only penetrate so far in salt water, so most of the ocean is much too deep to support plant life, with the exception of plant life that does not need to be rooted to the ocean floor, but is able to freely float on or near the surface.

From Tiny Phytoplankton To Giant Kelp


Since the ocean plants requiring root systems will all be found in shallow waters, we’ve come to know most of the major species, and for those living near coastal waters, a number of these saltwater plants are quite familiar. Ocean plants range in size from the giant kelp, the largest plant found in salt water, to the tiny phytoplankton, plants that are mostly single -celled, and which are by far the ocean plants that exist in the greatest numbers. Insofar as phytoplanktons require a significant amount of sunlight to survive, they are always found quite near the surface of the water. They can be so numerous at a given time in a given area in the ocean that they literally make the sea water appear to take on colors. Phytoplanktons are not to be confused with zooplankton. Most species of zooplankton are also microscopic in size, or nearly so, but zooplankton belong to the animal kingdom, and not the plant kingdom.


The Many Forms Of Algae


Many of the plants in the ocean are members of one of the families of algae. Not all algae are plants, some are, some are not, and some are “a species of something”. Kelp is a particularly interesting species of brown algae, as kelp often takes on a role similar to what trees do on dry land. Kelp makes forests. In some coastal areas, particularly in the temperate and polar regions, huge kelp forests exist. The kelp plants in these forests anchor themselves to the ocean floor or substrate through the use of root-like masses called holdfasts. These holdfasts are not true roots, but instead serve the same purpose as tendrils serve on climbing plants. They provide a base of support, and do not provide nutrition to the plant.

The trunk, or stalk of one of these kelp “trees” is called the stype, from which fronds grow, these fronds being what we often think of as being extremely long strands of “something”. If you come across a kelp forest or kelp bed, or kelp that has washed up on the beach, you may find a peculiar looking bulb or two. These bulbs, called pneumatocysts, are gas-filled bladders whose function is to keep a kelp plant upright. Not all species of kelp feature these bladders, and not all kelp will be found in kelp forests. In shallower waters, a large number of kelp plants is often referred to as a kelp bed.



While kelp requires a significant amount of sunlight to survive, it requires certain nutrients as well, nutrients that are to be found mostly in the more northern or southern ocean waters, but are not plentiful in tropical waters. Even though there is a greater abundance of sunlight in the tropics, kelp does not grow in the tropical oceans, largely due to this lack of required nutrients.


Saltwater Grasses And Sea Mats


Just as there are “forests of kelp” in the ocean, there is also the saltwater equivalent of prairies in very shallow waters, where saltwater grasses hold forth. Many types of sea grasses are flowering plants. Sea grasses provide both food and shelter for many different types of marine life. As mentioned above, kelp is a type of brown algae. All in all there are nearly 2,000 known species of brown algae. Some types of brown algae plants are not anchored to the ocean floor but are free floating. The best known free-floating species of brown algae is the genus Sargassum, which has gained fame due to its formation of the floating mats found in an area of the North Atlantic which has long been known as the Sargasso Sea.

Coral Is Not A Plant


Coral is often considered to be a strange form of plant life, but that is not correct. Coral is actually a strange form of animal life. Coral beds or reefs however are often covered by various types of ocean plants, which may explain why in some quarters coral is looked upon as a plant.


While in the deeper parts ocean there are no plants to be found rooted to the ocean floor, and while we are familiar with many of the shallow water species of plant life, there are many, many species of ocean plant life remaining to be discovered and classified. Many of these of course are microscopic in size, while other, larger plants yet to be discovered may be restricted to small areas in remote locations  seldom visited by scientists or biologists.