Goal 3.03 Earth’s Oceans are Reservoirs

/ An Estuary Is…
Adapted from
An estuary isa partially enclosed body of water(such as bays, lagoons, sounds or sloughs) where two different bodies of water meet and mix.
Crash! Thunder rumbles overhead. Raindrops fall, collect in a twisty, turning stream and dash downhill. Salmon flash and splash, struggling against the tugging current to spawn upstream. Fresh water swirls over a mossy green log, then flows into a broad, sweeping river. The river swells from incoming creeks and streams following a well-worn channel. Paddling ducks dash into a stand of cattails seeking shelter. Off in the distance, a lone seagull cries out. The river flow slows down, churning and twisting in its banks. This wide water road carries fresh water to its final destination – the coastal inlets and bays of a salty sea. Estuaries are places where rivers meet the sea!
An estuary begins where fresh river water flows into coastal bays and inlets. These areas of transition between the land and the sea are driven by tides, like the sea, but sheltered from the full force of ocean wind and waves, like a river. When fresh water meets salty seawater, both liquids combine turning into a brackish mixture. Estuaries can be called interior bays, lagoons, sounds or sloughs.
But, remember... estuaries are not only found wherefresh water from rivers and salt water from the ocean meet and mix. Estuaries can also be found wherefresh water from rivers or streams and chemically distinct water of a large lake meet and mix. These estuaries are called freshwater estuaries.
What Role do Estuaries Play in Earth’s Cycles?
Estuaries are connected to many different cycles on Earth including the nutrient cycle, the water cycle and the cycle of life.
In the nutrient cycle, estuaries serve as a place weremany elements are recycled and made available to living organisms.These elementsmust be kept in balance to maintain the health of the estuary.
In the water cycle, estuaries serve as places where evaporation of water occurs, and also serve to recharge ground water.
In the cycle of life, estuaries provide shelter, food and nursery grounds for animals. Decomposing animals in estuaries can provide nutrients for other organisms.
Estuaries are unique places that are valuable to the environment and to society.
Estuaries are places like no other. Each with its own specific characteristics, but all playing vital roles in the environment and in our lives.Some examples of estuaries’ unique and important features are:
Each estuary can make up an individual ecosystem. Look on a world map. The Mississippi Delta estuaries in the Gulf of Mexico are different from estuaries in San Francisco Bay, California. However, estuaries are also interconnected with other surrounding environments (oceans, lakes, forests, grassy plains) and nearby human communities.
Estuaries are constantly changing and are areas of transition. Life is dynamic and diverse in estuaries. Some animals and plants specialize in, or adapt to, living in the unique conditions of estuaries.
Estuaries vary widely around the world. Earth’s changing geology, flowing water and different weather patterns help create many diverse types of estuarine habitats.
Rivers provide nutrients, organic matter, and sediments to estuaries. Rivers flow downstream delivering fresh water from streams, small rocks and silt, and leaves and other vegetation debris. Nutrients support life in the estuary.
Estuaries can filter small amounts of pollutants and runoff. Vegetation helps filter and trap silt. However, too much nutrient or sediment input will create an unbalanced situation causing the health of the ecosystem to decline.
Estuaries act like huge sponges, buffering and protecting upland areas from crashing waves and storms and preventing soil erosion. They soak up excess water from floods and stormy tidal surges driven into shore from strong winds.
Estuaries provide a safe haven and protective nursery for small fish, shellfish, migrating birds, and coastal shore animals. In the U.S., estuaries are nurseries to over 75% of all fish and shellfish harvested.
People enjoy living near estuaries and the surrounding coastline. They sail, fish, hike, swim, and enjoy bird watching. An estuary is often the center of a coastal community.
/ Estuaries & You - How are Estuaries Connected to My Life?

/
Estuaries are important parts of our lives; interconnected to our economy, hobbies and culture, and an important part of our coastal and ocean ecosystems.
Estuaries provide commercial economic benefit to the U.S. in the form of seafood sales and jobs.
Recreational activities – such as fishing, birding, boating and hiking – are enjoyed by millions of Americans each year in estuaries bringing income to coastal communities.
Estuaries offer cultural importance to Americans. They are often city and trade centers, they are an important source of food, the buffer communities from storm surges, and they have a long history of cultural use by Native Americans.
Estuaries are vital ecosystems providing diverse habitat and nursery areas for many important organisms.
Because we are all connected to the nation’s coasts, our activities have many affects on estuaries, many of which are negative.
Anthropogenic disturbances to estuaries include coastal development, introduction of invasive species, pollution via runoff, over fishing, dredging and filling, dams and global climate change.
From government agencies and laws – established to protect estuaries – to volunteer citizens groups, our coasts are protected, restored and conserved in many ways.
There are many things you can do around your home an in your community to keep estuaries clean.

Color Your Own Estuary

Maybe someday you could be a nature illustrator like John Dawson. You can start practicing now by printing out these pages and coloring some estuary scenes.

Mid Atlantic/Gulf Coast Estuary Coloring Book Activity


Marine Ecosystems –

Marine ecosystems are a part of the largest aquatic system on the planet,covering over 70% of the Earth's surface. The habitats that make up this vast system range from the productive nearshore regions to the barren ocean floor. Some examples of important marine ecosystems are:

  • Oceans
  • Estuaries and Salt Marshes
  • Coral Reefs and Other Tropical Communities (Mangrove Forests)
  • Coastal areas like Lagoons, Kelp and Seasgrass Beds and Intertidal systems (rocky, sandy, and muddy shores)

Marine ecosystems are home to a host of different species ranging from tiny planktonic organisms that comprise the base of the marine food web (i.e., phytoplankton and zooplankton) to large marine mammals like the whales, manatees, and seals. In addition, many fish species reside in marine ecosystems including flounder, scup, sea bass, monkfish, squid, mackerel, butterfish, and spiny dogfish. Birds are also plentiful including shorebirds, gulls, wading birds, and terns. Some marine animals are also endangered including whales, turtles, etc. In summary, many animal species rely on marine ecosystems for both food and shelter from predators.

Marine ecosystems contain several unique qualities that set them apart from other aquatic ecosystems, the key factor being the presence of dissolved compounds in seawater, particularly salts. This total gram weight of dissolved substances (salts) in one kg of seawater is referred to as salinity. In general 85% of the dissolved substances are Sodium (Na) and Chlorine (Cl) in seawater. On average seawater has a salinity of 35 parts per thousand grams (ppt) of water. These dissolved compounds give seawater its distinctive "salty" taste, affect species composition of particular marine habitats, and prevent oceans from freezing during the winter. Daily changes in factors such as weather, currents, and seasons as well as variations in climate and location will cause salinity levels to vary among different marine ecosystems. In areas such as estuaries, tidal marshes, and mangrove forests, tidal and freshwater influences from river and streams makes it necessary for marine organisms to adapt to a wide range of salinity levels. These organisms such as mussels, clams, and barnacles, are called euryhaline (salt tolerant) organisms. Other organisms, in particular finfish, are unable to tolerate such changes in salinity. These organisms are considered to be stenohaline (salt intolerant). These species require more constant levels of salinity, forcing them to either migrate to new areas when fluctuations in salinity levels occur or to seek out areas where salinity change is minimal (e.g., the deep ocean).

Like other aquatic ecosystems, marine ecosystems require nutrients and light to produce food and energy. However, both nutrients and light are limiting factors in marine ecosystem productivity. Like many other aquatic plants, photosynthetic marine organisms (i.e., phytoplankton) rely upon sunlight and chlorophyll a to absorb visible light from the sun as well as nitrogen (N), phosphorus (P), and silicon (Si) to generate food and promote growth and reproduction. However, the amount of light penetrating the ocean surface tends to decrease with increasing water depth, therefore photosynthesis can only take place within a small band near the surface of the water (called the photic zone). In addition, nutrient availability often varies significantly from place to place. For example, in the open ocean, nutrient levels are often very poor causing primary production to be very low. In contrast, nearshore waters such as estuaries and marshes are often rich in nutrients, allowing primary production to be very high. In some instances, nearshore ecosystems have an excess of nutrients due to runoff and other terrestrial sources. Excess nutrients can cause an over-stimulation of primary production, depleting oxygen levels and causing eutrophic conditions to occur in coastal habitats.

Marine ecosystems are very important in to the overall health of both marine and terrestrial environments. According to the World Resources Center, coastal habitats alone account for approximately 1/3 of all marine biological productivity, and estuarine ecosystems (i.e., salt marshes, seagrasses, mangrove forests) are among the most productive regions on the planet. In addition, other marine ecosystems such as coral reefs, provide food and shelter to the highest levels of marine diversity in the world.

The diversity and productivity of marine ecosystems are also important to human survival and well-being. These habitats provide us with a rich source of food and income, and support species that serve as animal feed, fertilizers for crops, additives in foods (i.e., ice-cream) and cosmetics (i.e., creams and lotions). Areas such as mangroves, reefs, and seagrass beds also provide protection to coastlines by reducing wave action, and helping to prevent erosion, while areas such as salt marshes and estuaries have acted as sediment sinks, filtering runoff from the land. Despite the importance of marine ecosystems, increased human activities such as overfishing, coastal development, pollution, and the introduction of exotic species have caused significant damage and pose a serious threat to marine biodiversity. Please visit USEPA's Web site for resources on Marine Ecosystems,Oceans, Coasts and Estuaries, and Marine Species at Risk. Also, read about EPA's 2007 Report on the Environment Coastal Benthic Community indicator.

LIFE CYCLE OF AN UPWELLING EVENT
First Stage: Warmer surface water, colder bottom water.
During the summer months increased exposure to the sun heats the water on the ocean's surface. Much of the heat of the sun is trapped in tiny particles floating at or near the surface of the water, which keeps the heat from penetrating and reaching the water closer to the bottom. Therefore, the water closer to the bottom is usually colder than that found on the surface.
Second Stage: Warm surface water is blown offshore; cold seafloor water rises.
Just remember that the surface water moves away from the coast, even though the wind is blowing along (parallel to) the coast. When the warm surface water moves away from the coast of New Jersey in the summer, colder water from the bottom rises to replace it along the shore, and an upwelling occurs.
Third Stage: Cold water brings nutrients to the surface.
Upwelling can have important impacts on the plants and animals in the ocean. Phytoplankton are single-celled microscopic plants that live in the ocean. Similar to plants on land, phytoplankton need light, nutrients, and carbon dioxide to live and grow. Near the surface of the ocean, there is plenty of light and carbon dioxide in the water, but usually low levels of nutrients because they have been used up by the existing phytoplankton. The cold water found closer to the bottom of the ocean is rich in nutrients, and when these nutrients are carried to the surface during an upwelling the phytoplankton can grow and multiply in huge numbers. This is called a phytoplankton bloom. A bloom causes the water to appear green and murky, and attracts fish and other marine creatures who feed on the phytoplankton or the small animals that eat the phytoplankton.

1