Level 3
Experts believe the declining shark populations will have a major effect on ocean ecosystems around the world. That's because sharks serve as "ecosystem engineers" in their underwater habitats.
Sharks are apex predators. This means they have few natural predators and eat animals below them in the food web. A food web is like a food chain only larger. It explains how different plants and animals are connected in ways that help them survive. Sharks help keep ecosystems balanced by feeding on smaller fish. This is important because it prevents smaller fish from overwhelming an ecosystem. And because they are messy eaters, sharks will often leave scraps behind for other scavengers.
Sharks also help ecosystems by intimidating other species. Sharks help keep seagrass healthy by frightening sea turtles. Sea turtles feed on seagrass, and when sharks are present, sea turtles will graze more widely, rather than in a single area. Without sharks present, sea turtles will graze in one area for a long time, eventually destroying important habitats for other marine species.
Keeping seagrass healthy isn't just important for fish, it's also vital to the health of our planet. Seagrasses store large amounts of carbon, which helps limit the amount of carbon entering the atmosphere. Greenhouse gases like carbon trap heat in Earth's atmosphere and contribute to global warming.
Sharks also protect coral reefs from becoming overwhelmed with algae. Sharks help balance the number of fish that feed on algae. Without sharks, the algae become overgrown, which can be harmful to coral reefs. Additionally, sharks often feed on the weakest animals in an ecosystem. By weeding out sick animals, sharks help prevent the spread of infectious diseases in fish populations, which in the long term, helps keep these populations healthier.