Ocean plant life is arguably the most important organism on the planet. For a start it is the bottom of the food chain for most animals that live in the ocean and provides them with a home. Added to that, ocean plant life produces more than half the world’s oxygen and, with the forests, oceans are said to be the lungs of the earth because ocean plant life absorbs carbon dioxide along with solar energy as they release oxygen into the ocean.
Algae, which is what ocean plant life is called, ranges from tiny single-celled phytoplankton to gigantic kelp fields under the sea.
Food
For thousands of marine organism, both large and small, plant life in the ocean is the main source of food. Phytoplankton, which is free floating microscopic algae, is the main food of many herbivores which are low on the marine food chain. Kelp and other larger ocean plants which grow in immense fields under the sea are eaten by other ocean herbivores. Most ocean plants use the sun’s light through photosynthesis to produce energy to grow. Marine ecosystems can be completely changed if there are dramatic temperature changes or pollution which causes the plants to stop growing or to grow to excess.
Habitats
Ocean plant life provides homes for many ocean animals, ranging from large crustaceans to small tropical fish. Vast underwater kelp and large algae fields provide a safe place for many small fish to hide. Small creatures in shallow, coastal ecosystems like tide pools and estuaries live among the seagrasses. Coral reefs, known as the rainforests of the sea, play host to thousands of ocean plant species and are home to over 25% of all the marine life on the planet. Human activities such as pollution and overfishing can easily damage the plants in these extremely susceptible ecosystems.
Oxygen
Ocean plant life is estimated to produce between 70 and 80% of the oxygen in the atmosphere. Because there are so many more ocean plants than there are on land, they produce so much more of the oxygen supply of the planet. Oxygen is essential for marine animals but the oxygen produced by the ocean plants is also used by humans and other land animals.
Carbon Dioxide
Carbon dioxide, along with sunlight, is absorbed during photosynthesis and because there are so many more plants in the ocean than on the land, most of the carbon dioxide produced on the Earth is absorbed by ocean plants. It is thought that the oceans store one third of the carbon monoxide from the combustion of fossil fuels. However, the more carbon dioxide the oceans absorb, the more acidic the pH of the water becomes which causes entire marine ecosystems to become unbalanced.
Types of Ocean Plant Life
Phytoplankton
The microscopic form of algae, phytoplankton, is present away from the coasts in the open sea. Plankton is a combination of phytoplankton and microscopic animal life; it becomes the main food source of many ocean creatures. So phytoplankton vital to the ocean environment and if it wasn’t there, many of the ocean animals we know and love would become extinct. Phytoplankton also produces more oxygen than all land plants giving us fresh air and reducing greenhouse gases.
Diatoms are the most abundant type of phytoplankton with 20,000 species that can produce 100 million offspring in favourable conditions. As they can reproduce so rapidly, a single gallon of seawater can contain a billion diatoms. When not eaten, phytoplankton only survives a couple of days. Phytoplankton dies off quickly if water temperatures change significantly or there aren’t sufficient nutrients in the water.
Coral Reefs
Coral Reefs are another type of algae that grow in groups near the coast and are beautiful and colourful. Coral thrives in temperate conditions and keeps coastal ecosystems stable as well as being essential to ocean biodiversity. Coral reefs provide a habitat and safe haven for many fish to lay their eggs in. Shorelines are protected from devastating waves and storms by coral reefs and a large number of medicines are made from coral. Coral reefs are threatened by human pollution and coastal development.
Kelp
The larges ocean plant is giant kelp which can reach 250 feet and live for up to 7 years. It is a type of brown algae that thrives in cool, nutrient rich, coastal waters. It grows in clusters called forest covering many miles. Kelp provides both food and habitat to many marine animals. Where it has been introduced, there has been an increase in biodiversity and provided more fish for local fishermen. Commercial harvesting of kelp, as it is used in cosmetic and vitamins, along with pollution are the greatest threat to kelp.
Seagrass
The only flowering underwater plant, seagrass grows near the ocean surface in many coastal regions in large meadows and provides habitat for many small marine animals. Seagrass meadows are the world’s third most valuable ecosystem. They absorb nutrients from coastal river run offs and stabilise sediment on the ocean bed. Human activity destroys seagrass meadows which can lead to the release of carbon dioxide into the atmosphere.
