One of the reasons scuba diving is so captivating is the opportunity to witness the wonders of marine life. From seahorses hiding in seagrass to turtles feasting on seaweed, these incredible creatures rely on ocean plants for their survival. In this article, we will explore the fascinating world of ocean plants, their underwater adaptations, and their crucial significance for life on Earth.
What Plants Live in the Ocean?
Ocean plants are a diverse group, comprising thousands of species ranging from seaweeds to trees. Let’s take a closer look at some of the most prominent types:
Phytoplankton
Phytoplankton are single-celled, plant-like organisms that thrive in sunlit, nutrient-rich waters. They are essential to the ocean’s food chain, serving as a vital source of nourishment for zooplankton, which in turn sustain larger marine animals. Despite their microscopic size, phytoplankton blooms can cause dramatic changes in the ocean’s color, attracting a variety of megafauna.
Brown Seaweeds / Algae
Brown seaweeds come in a variety of sizes and shapes, from delicate feathery forms to large and leathery kelps. Among them, kelps are the most well-known. They anchor themselves to rocky seabeds using a “holdfast” and can grow up to 2 feet in a single day, forming dense underwater forests. Other intriguing species include the oyster thief and Neptune’s necklace.
Red Seaweeds / Algae
Red seaweeds have extra pigments that aid in photosynthesis, giving them their characteristic color. These seaweeds are particularly adept at capturing sunlight, allowing them to thrive at greater depths compared to their brown counterparts. Some species, such as crust-forming coralline algae, play crucial roles in building and protecting coral reefs. Additionally, edible varieties like Japanese nori and Welsh laverbread are considered delicacies.
Green Seaweeds / Algae
While microscopic green algae are often grouped with phytoplankton, larger green seaweeds are more similar to true plants. Sea lettuce is a common and resilient green seaweed found along rocky shorelines worldwide. However, there are numerous species with different shapes and names, such as stringy flaccid seaweed, tubular velvet horn, cactus seaweed, and sea grapes.
Sargassum
Sargassum is a unique type of brown seaweed that floats on the ocean’s surface instead of attaching to rocks. It forms extensive belts in areas like the Sargasso Sea, providing a habitat for various traveling animals, including baby turtles and sargassum fish.
Seagrasses
Seagrasses are the only flowering marine plants that live permanently underwater. Unlike seaweeds, they evolved from land plants and have roots to absorb nutrients from sediment. These marine meadows create essential habitats and cover vast areas, such as Indonesia’s 30,000 km² of seagrass beds. Some seagrass meadows, like the Mediterranean’s Neptune grass, are among the oldest known living organisms on Earth.
Mangroves
Mangrove forests are characterized by their evergreen trees and intricate network of roots. Although they are also considered plants, mangroves differ from seagrasses as they are only partially submerged. They cover approximately 12% of the world’s coastlines and provide critical ecological services, including storm protection. Famous examples include Florida’s Everglades and the Sundarbans, the largest mangrove forest in the world.
What About Sea Fans?
Although sea fans may resemble plants, many species seen while diving are actually animals. These include corals, anemones, sea whips, sea fans, urchins, barnacles, and sea cucumbers. To learn more about the fascinating underwater world, consider taking the PADI Underwater Naturalist course.
How Do Plants Survive in the Ocean?
Similar to their terrestrial counterparts, ocean plants require sunlight, air, and nutrients to survive and carry out photosynthesis. They have various adaptations to thrive in the challenging marine environment. For example:
- Kelps use long stalks or gas-filled bladders to reach sunlight.
- Phytoplankton utilize substances or spines to float in sunlit layers.
- Seaweeds and seagrasses employ various defense mechanisms, such as bad tastes or toxins, to deter grazers.
- Mangroves excrete excess salt through their roots or leaves.
- Some seaweeds produce a protective mucus to prevent dehydration during low tide.
- Kelps shed and regrow their fronds to eliminate parasites.
Why Are Ocean Plants Important?
Ocean plants serve as the foundation of life in the world’s oceans. Firstly, they form the base of the marine food chain, providing sustenance for countless organisms and creating essential habitats and shelters. Secondly, these plants are responsible for producing over 50% of the Earth’s oxygen and absorbing approximately 25% of carbon emissions. They play a vital role in maintaining a balanced ecosystem and mitigating climate change effects.
Furthermore, ocean plants offer economic benefits by providing food and income for communities. They also help protect coastal areas from storm damage and prevent erosion.
Protecting Ocean Plants — And Our Future
Unfortunately, human activities and climate change pose significant threats to ocean plants. Pollutants can cause harmful algal blooms, resulting in the death of marine life and blocking sunlight. Mangroves and seagrass meadows are also under threat, leading to the loss of crucial habitats and species such as dugongs and green turtles.
It is our responsibility as divers and stewards of the ocean to take action. By joining the Ocean Torchbearer community, you can contribute to local initiatives that promote global change, such as ocean clean-ups, mangrove restoration projects, and conservation efforts for seagrass meadows.
Together, we can protect these invaluable ocean plants that sustain life and preserve the future of our planet.