Estuaries

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Estuaries

Hydrosphere 8th

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What is an estuary?

• An estuary is formed when two bodies of water and their habitats meet.

• For example, when a river empties into the ocean.

• Off the coast of NC, the Pamlico Sound is one of the largest estuaries in the US.

• They are very special because their waters are brackish.

• This means the water is a mixture of freshwater from the river and ocean water.

• This mixture lowers the overall salinity content (typically less than 35 ppm).

• Estuaries are some of the most productive ecosystems in the world because many animals rely on it for food, places to nest, and breed.

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Characteristics of an estuary

• _{They are a transition between two very different}

environments.

• _{The daily tides (usually 2 high and 2 low tides}

each day) have a big impact on these

environments, but depends greatly on its location, depth, winds, shape of the coastline, and anything that may restrict water flow.

• _{Because estuaries are partially enclosed by land,}

it is protected from the full impact of the ocean waves, winds and storms.

• _{No two estuaries are the same! They are}

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Nurseries of the Sea

• _{Estuaries are home to lots of different organisms:}

salmon, herring, horseshoe crabs, bass, and ducks to name just a few.

• _{These organisms come here to live, feed, nest and}

reproduce.

• _{They provide an estimated 75% of commercial}

fish and a larger percentage of the recreational fish catch for the US.

• _{Estuaries also are visited by millions of people}

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Estuaries are water filters!

• _{As the water enters from the river and ocean, the}

marsh grasses and peat filter out pollutants like herbicides, pesticides, heavy metals, excess

sediments and nutrients, storing them in the sand.

• _{Oysters will eat some of these bad things,}

collecting the contamination inside their bodies.

• _{Bacteria also eat the organic matter and release}

carbon dioxide, hydrogen sulfide, and methane into the atmosphere.

• _{Because of the excess nutrients coming from the}

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Estuaries Protect!

• _{They are considered a buffer zone, stabilizing the}

shoreline and protecting the coast, inland

habitats, and human communities from flooding and storm surges from hurricanes.

• _{They also protect rivers, streams, and coasts from}

excess erosion by wind, water, and ice.

• _{Sand bars buffer the impact of waves, and plants}

and shellfish beds anchor the shore against the tides.

• _{Swamps and marshes are the first to be impacted}

by high winds, soak up heavy rains and storm

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Types of Estuaries in NC

• _{Trunk estuaries}

• Run perpendicular to the coast, in line with the rivers that feed them

• Example: Neuse River estuary • _{Tributary estuaries}

• Flow into trunk estuaries • _{Back barrier estuaries}

• Lie parallel to the coast, between the mainland shore and the barrier islands

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Characteristics of the Pamlico

Estuary

• _{The Pamlico Estuary is the largest estuary in NC.} • _{Water that drains here are the Chowan, Roanoke,}

Pasquotank, Pamlico, and Neuse rivers to name a few.

• _{These rivers deposit sediments high in nutrients,}

which will settle on the sand and mud of the bottom of the estuary.

• _{It is less than 30 feet deep, so sunlight can reach}

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Threats to the estuarine

system

• _{Changes to the land:}

• As the land is developed for human use, it will change the flow of water through this ecosystem.

• Roads made of asphalt and concrete deflect water so that it runs off with all the contaminants directly into the

rivers, estuaries, and sea.

• _{Wetlands were used for logging and farming}

before laws and restrictions were in place.

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More threats!

• _{Dredging allows large boats to pass through or}

dock closer to shore.

• Dredging is when the bottom of the water is scraped and made deeper.

• This causes damage to plants, oyster beds, and stirs up sediments that clouds the water.

• When the water is cloudy, fish cannot breathe properly and may take in contaminants, and predators cannot see their prey to eat.

• It can actually have the reverse effect on the water, where sediment deposition is increased and dredging has to

continually occur.

• _{Global warming is causing sea levels to rise as}

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And more…nutrients

• _{Increase in nutrients can have a negative affect.} • Sewage treatment plants, septic systems, polluted air,

and fertilizers deposit nutrients like nitrogen and phosphorus into rivers which make it into estuaries.

• These high levels of nutrients can increase the amount of algae at such a rate that the algae will block sunlight from reaching through the water, killing off other plants.

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And more still…sewage &

toxins

• _{Sewage plants, septic tanks and run off from farms into}

rivers carry fecal matter from humans and animals to the estuarine system.

• This brings bacteria, viruses, and parasites that transmit diseases to this ecosystem.

• _{Toxins can also cause an overgrowth of plants, removing}

too much oxygen from the environment, which kills fish and other organisms through suffocation.

• This can also happen when the salt and freshwater are not

appropriately mixed together: salt water sinks and freshwater floats.

• Bottom dwellers begin to live in very salty conditions, which has less oxygen and causes them to suffocate.

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Resources

• http://oceanservice.noaa.gov/education/tutorial_estuaries/ • http:// oceanservice.noaa.gov/education/tutorial_estuaries/est04_geology.html • http:// oceanservice.noaa.gov/education/tutorial_estuaries/est03_ecosystem.htm l • http:// oceanservice.noaa.gov/education/tutorial_estuaries/est02_economy.html • http:// oceanservice.noaa.gov/education/tutorial_estuaries/est01_whatis.html

• http://www.learnnc.org/lp/pages/544

• http://

scnces.ncdpi.wikispaces.net/file/view/Unpacked_Content_Grade8Science_ RevisedSeptember2012.docx.pdf