The term algae refers to many different types of organisms that may be found in a marine ecosystem. The classification algae includes organisms of a wide range of sizes and colors. Some species of algae are microscopic, unicellular organisms that grow in groups. Other types are much bigger, such as seaweed or giant kelp. Algae can be green, yellow, blue-green, red, or brown.
Algae are an essential part of a healthy marine ecosystem. One type of unicellular, plant-like alga is known as phytoplankton. Phytoplankton occurs near the surface of a body of water, where it is exposed to sunlight. It is the base of the marine food chain.
Some other species of algae exist in symbiotic relationships with other organisms. For instance, some sea sponges coexist with green algae. The algae live near the sponges’ surface, producing sugar and oxygen through their metabolic process. The sea sponges take in the sugar and oxygen in order to grow. The green algae are protected from predators by the sponges.
A coral reef is a marine ecosystem that is often dependent on algae. A coral reef needs to exist in equilibrium, with coral growth balancing with marine erosion. Certain species of algae can speed up the metabolism of the invertebrates that form coral. These invertebrates make use of the algae’s sugar and oxygen. Without the algae, the reef would gradually deteriorate.
While certain algae is necessary for a functioning marine ecosystem, other species can be damaging. A small percentage of algae species naturally produce toxins, which can be harmful to animals that consume them. Microscopic algae will sometimes start to reproduce and accumulate rapidly in one area, forming an algal bloom. When one of the toxic algae species increases in this way, it is called a harmful algal bloom.
Harmful algal blooms can have significant negative effects on marine species. These incidents have led to the deaths of large numbers of fish, sea turtles, and marine mammals. The toxins sometimes lead to human illness when seafood becomes contaminated. Harmful algal blooms can also cause oxygen depletion in a body of water.