An estuary is an area where fresh water from rivers flows into the salt water from an ocean. Though these areas can be biologically productive ecosystems that provide habitats for many animals and plants, they can also be a harsh environment for others because of their high salt content.
Plants of the Estuary
Plants that grow in estuaries must contend with exposure to wind and strong currents, as well as low oxygen levels and salty conditions. Despite these hazards, many species of plants prosper in the estuaries. Seagrass, or the Zostera capricorni, is a New Zealand native. It is a flowering plant with small, dark ribbonlike leaves that grows in the seawater. Eelgrass also thrives in the conditions of the estuary. Growing below the lowest tide level, eelgrass functions best when submerged in water. Serving as food for some species, eelgrass is a meal of choice for the American Wigeon and Brant. Algae also grows in the estuary, but has a shorter lifespan than some of the other plants. While it grows despite the temperature, it generally only lasts a few weeks at the most.
Birds of the Estuary
Bird species are plentiful in the estuaries. Feeding on plants, snails and fish, birds find an easy hunting ground in the shallow waters of the ecosystems there. Bald Eagles come to the estuary to feed on dead fish and birds, while Peregrine Falcons make meals of the sandpipers on the beaches. Ducks hunt in the mud to find plankton and small animals. Feeding on shellfish and insect larvae, the godwits find their prey by digging into the sediment with their beaks. Herons fly atop the water searching for fish, and fernbirds can be found in the reeds of the estuaries. The Black Brant bird, which migrates up to 3,000 miles, stops by to eat eelgrass on its way past the estuary.
Fish of the Estuaries
Many species of fish make their way to the estuaries. Eels swim through on their way to their breeding grounds at sea. The adult whitebait lays its eggs in the estuary. A puffer fish look-a-like, the Pacific Spring Lumpsuker, eats small animals. The largest of the Pacific Salmon, the Chinook Salmon, also lives in the estuary but is suffering from declining numbers.
Other Creatures of the Estuary
Along with plants, birds and fish, many other creatures make their home in the estuary ecosystems. The Mud Shrimp thrives here. Dungeness Crabs start their lives out in the eelgrass, and as they grow, they graduate to the waters of the estuary. River Otters are comfortable both in fresh water or saltwater, but dine on fish and crabs while passing through. Harbor Seals often bask in the sun on the banks of the water and dive in for herring and salmon. The largest of all sea stars, the Sunflower Star, can be found in estuary waters as well.