47 Bloomin' Algae-Low

Bloomin Algae FOCUS Question How does an unbalanced ecosystem cause blooms of algae to form?

What's That Green Stuff? Have you ever visited a pond in spring or summer? You may have seen green stuff floating on the water's surface. What is that murky stuff? It's algae! Algae are a group of organisms with thousands of different species. They're not plants or animals. But like plants, they use photosynthesis. That means they make their own food from sunlight, water carbon dioxide, and chlorophyll. Chlorophyll is a chemical that causes many types of algae and plants to be green. Some algae are one-celled organisms. You would need a microscope to see them. Other types have many cells. These types sometimes grow to a huge size. Algae may not seem exciting. But they have a very important job. Tiny algae are at the base of aquatic food webs. This means they produce the food that many other organisms depend on. These producers are food for animals that eat algae and plants. The plant-eating animals are often food for meat eaters. Without the producers at the base of the food web, no one would have anything to eat! Word Wise The word algae (AL-jee) is plural for alga (AL-guh). a single organism.

Algae are important for another reason, too. Through photosynthesis, they make oxygen. Humans and almost all other organisms need oxygen to stay alive. We depend on algae and plants for this precious resource.

Algae Out of Balance Algae need water, sunlight, and certain nutrients— especially nitrogen and phosphorus—to grow Sometimes the nutrients become too plentiful. Then algae can grow too fast. They build up and create blooms. Algal (AL-gull) blooms can cause problems for other living things. They are a sign that the ecosystem is out of balance. The main cause of harmful algal blooms (HABs) is nutrient pollution in oceans and lakes. This problem occurs when too much nitrogen and phosphorus get into the water.

Dangers to Life Forms Harmful algal blooms can create dead zones in oceans or lakes. In dead zones, the water does not contain enough oxygen to support most living things. Animals living near dead zones must leave the area or die. Where does the oxygen go? As algae complete their life cycle, they die. Bacteria break down the dead algae. During this process, bacteria use some of the oxygen in the water. In HABs, the increase in algae growth results in more dead algae. Then more bacteria use up more of the oxygen to break down all the dead algae.

Algae Toxins Some HABs are harmful because the algae make poisons called toxins. The toxins are released when the algae die. These poisons can kill fish and other animals. Sometimes small fish absorb the toxins. These fish are food for other animals. As the toxins travel up the food web, they can kill larger animals such as birds, turtles, and dolphins. Humans can come in contact with these toxins through drinking water, showering, swimming, and boating. The toxins can cause rashes and nervous system problems. They can even make it hard to breathe.