Many marine animals feed by separating food particles from water, known as filter feeding. This method of eating is similar to removing boiling water from cooked vegetables with a sieve or strainer. Filter feeders include a wide range of animals including bivalves, some snails, sponges, fan worms, barnacles, corals, sea lilies, some fish, and even some birds like Flamingos and baleen whales like the Blue Whale.

Filter Feeding

Filter Feeding is Like Using a Sieve

The many filter-feeding animals, sometimes called suspension feeders,[1] use various methods of filtering. Baleen whales and the Flamingo suck food-containing water into their mouths then press the water out past sieve-like mouthparts (baleen "teeth" of the whale), retaining the food in their mouths. The Whale Shark swims through the water with its mouth gaping, then closes its jaws and presses the water out its gills, retaining the food within. Depending on the animal, these larger filter feeders sometimes consume smaller filter feeders like the larvae of crustaceans and bivalves.

Krill, a shrimp-like crustacean, have long legs with “feeding baskets” that branch out to collect food particles and filter it from the water. The animal then draws the collected food into its mouth. Bivalves collect food as part of their respiratory activities. As water passes through the animal’s gills, food particles collect in the sticky mucus on the surface of their gills and are transported by cilia to the animal’s mouth.

Krill Feeding Basket

Krill “Feeding Basket”

Filter feeding plays an important role in marine ecosystems. The water filtered by these animals is effectively being cleaned because particles are being removed. This clean water allows other marine life to thrive. The Gulf of Mexico is home to 15,000 diverse species of marine plants and animals. The clean water produced by these filter feeders allows sunlight to enter the water’s depths to reach plants and animals like coral that need sunlight to grow.

The Deepwater Horizon oil spill has caused great concern about filter-feeding animals. As the oil enters their habitats, animals like clams and oysters will undoubtedly filter oil-containing water. In small amounts, the oil might not kill these animals because of their well-documented abilities to tolerate low levels of toxin. However, when these animals are consumed by larger animals, they will also consume the oil that has accumulated in their prey. Bivalve filter feeders are well known to “bioaccumulate” toxins like the hydrocarbons found in oil, making them an especially dangerous part of the food web for predators, including human consumers. Dr. José Leal, Director of the Bailey-Matthews Shell Museum on Sanibel Island, stated that a main concern is the “hydrocarbons, which are very powerful carcinogens … if someone eats that then they will have a problem right away.”

[1] A Revised Classification of Suspension Feeders | NZETC