What is Brackish Water?

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  • Written By: Mary McMahon
  • Edited By: Bronwyn Harris
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  • Last Modified Date: 29 December 2019
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Brackish or brack water is water with a level of salinity between freshwater and seawater. In many places around the world, brackish water appears naturally, and it forms an important habitat for some unique animal species. It can cause environmental damage, however, since it is harmful for organisms that have not adapted to it. This becomes an issue when such water is deliberately cultivated, as is done in some regions to farm desirable food fish. It is also unpleasant to drink, and it may cause health problems.

The term "brackish" was first used to describe portions of the potable water table that had been contaminated by salt water in the 1500s. The mixing of salt and fresh created mildly salty water that was not as salty as seawater, but still distasteful. Many people also noted that the water was harmful, due to unique microorganisms that cause human illness that thrive in it.

In nature, estuaries are a common site of brackish water. An estuary is a location where salt and fresh water mix, typically around the opening of a river. The estuary environment is quite distinctive, as it bridges oceans and rivers, hosting unique fish, plants, and animals. When the balance of an estuary is disrupted, it can be serious for the animals that call the area home. Many anadramous fishes appreciate estuaries, because the slow change in salinity allows the fish to accustom themselves.


Mangrove swamps are also classically brackish. Many mangroves are located along shorelines, so there is a transitional area of saltiness that ebbs and flows with the tide. Many fish breed in such swamps, and unique plants call these regions home. In some regions, mangroves are an important buffer zone between the ocean and the land, protecting the land from storm surge as a result of hurricanes and tsunamis.

Semi-salty water can also be found in some inland lakes and seas, such as the Caspian Sea. The salinity in these lakes and seas may vary, depending on water flow and time of year, and they often host a range of unique animals and plants. It is not uncommon to see stratification in these bodies of water, with cold salt water on the bottom and warmer fresh or brackish water on the top. Each layer hosts different animals, and disruption of the layers can have unfortunate results for the local ecology.


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Post 8

I did not know that brackish water had any benefits, because there are a lot of drawbacks, such as people who are accustomed to drinking fresh, clean water can not drink brackish water. Also it is kind of a waste of fresh water because brackish water is not used much, and the fresh water in the mix is contaminated by the salt water. The world does not have much fresh water.

Post 4

I have heard of some people in Hawaii using a seaweed found in brackish ponds as fertilizer for their vegetable gardens. However, they do rinse it with fresh water to remove any salts from the brackish water.

Post 3

Many people decide to try a brackish water aquarium before switching to salt water. There are many fish who live in brackish water and would be best suited to a brackish aquarium. Some varieties are the Black Sailfin Molly, Bumble Bee Goby, Dalmation Molly, Columbian Shark. There are several others. The salinity and p.h. of the brackish water must be in a speicific range for these fish to survive. Although this would be a beautiful tank to have it would be very difficult to maintain.

Post 1

How does the diamondback terrapin survive in brackish water?

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