Life in an Estuary Marine Life

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Imagine that you live in the sea and sometimes the water is salty and sometimes it is almost entirely freshwater. The water levels also rise and fall and even the chemistry of the water changes. How would you adapt to all these changes? These are the challenges of living in an estuary and the organisms that are found here are constantly adapting to different conditions.

Great Blue Heron eating fish in estuary
Great Blue Heron catching a fish in an estuary.
Source: NOAA News

Estuaries are areas of water and shoreline typically found where rivers meet the ocean. Many different types of plant and animal communities call estuaries home because their waters are brackish - a mixture of fresh water draining from the land and salty seawater. This unique combination of salt and fresh water creates a variety of habitats for the plants and animals to live in. Some common estuarine habitats are: oyster reefs, kelp forests, rocky and soft shorelines, submerged aquatic vegetation, coastal marshes, mangroves, deepwater swamps, and riverine forests. With so many places to live and so many niches to fill it is no wonder why estuaries are some of the most productive ecosystems in the world.

Importance of Estuaries

Estuaries are very important to the lives of many animal species. They are often called the “nurseries of the sea” because numerous animal species rely on estuaries for nesting and breeding. Most of the fish and shellfish eaten in the United States, including salmon, herring, and oysters, complete at least part of their life cycles in estuaries. Besides being a source for food, humans also rely on estuaries for recreation, jobs, and even our homes. Of the 32 largest cities in the world, 22 are located on estuaries. This can be both a good and a bad thing. Estuaries filter out sediments and pollutants from rivers and streams before they flow into the ocean, providing cleaner waters for humans and marine life. However, coastal development, introduction of invasive species, over fishing, dams, and global climate change have led to a decline in the health of estuaries, making them one of the most threatened ecosystems on Earth.

Estuary Stewardship

Ensuring the health of our estuaries is vital to the survival of the plant and animal communities that call them home and the humans that depend on them for their way of life. To preserve our estuaries, the National Estuarine Research Reserve System was established to protect more than 1.3 million acres of estuarine habitat for long-term research, monitoring, education, and stewardship throughout the coastal United States. However, you can also help protect estuaries at your home by planting native plants, using fertilizers sparingly, and cleaning up after your pets.

Educational Connection

Education also plays an important role in protecting our estuaries. An estuarine literate person understands the interconnectedness and interdependency of estuarine systems with other earth system in both time and space; can communicate about estuaries in a meaningful way; and is able to make scientifically informed and responsible decisions regarding estuaries and coastal areas. To creating an estuarine literate society, the National Estuarine Research Reserve System has developed six estuarine principles and concepts. Educators can use this framework to build lessons and curriculum that will teach their students the importance of estuaries and what they can do to help protect them.

Adapted from: Estuaries Tutorial, NOAA National Ocean Service and Basic Facts about Estuaries, National Estuarine Research Reserve System
Last Modified: April 2015

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