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Estuaries: where the ocean meets fresh water

Estuaries are biomes that occur where a source of fresh water, such as a river, meets the ocean. Therefore, both fresh water and salt water are found in the same vicinity; mixing results in a diluted (brackish) saltwater. Estuaries form protected areas where many of the young offspring of crustaceans, mollusks, and fish begin their lives. Salinity is a very important factor that influences the organisms and the adaptations of the organisms found in estuaries. The salinity of estuaries varies and is based on the rate of flow of its freshwater sources. Once or twice a day, high tides bring salt water into the estuary. Low tides occurring at the same frequency reverse the current of salt water.

The short-term and rapid variation in salinity due to the mixing of fresh water and salt water is a difficult physiological challenge for the plants and animals that inhabit estuaries. Many estuarine plant species are halophytes: plants that can tolerate salty conditions. Halophytic plants are adapted to deal with the salinity resulting from saltwater on their roots or from sea spray. In some halophytes, filters in the roots remove the salt from the water that the plant absorbs. Other plants are able to pump oxygen into their roots. Animals, such as mussels and clams (phylum Mollusca), have developed behavioral adaptations that expend a lot of energy to function in this rapidly changing environment. When these animals are exposed to low salinity, they stop feeding, close their shells, and switch from aerobic respiration (in which they use gills) to anaerobic respiration (a process that does not require oxygen). When high tide returns to the estuary, the salinity and oxygen content of the water increases, and these animals open their shells, begin feeding, and return to aerobic respiration.

Freshwater biomes

Freshwater biomes include lakes and ponds (standing water) as well as rivers and streams (flowing water). They also include wetlands, which will be discussed later. Humans rely on freshwater biomes to provide aquatic resources for drinking water, crop irrigation, sanitation, and industry. These various roles and human benefits are referred to as ecosystem services    . Lakes and ponds are found in terrestrial landscapes and are, therefore, connected with abiotic and biotic factors influencing these terrestrial biomes.

Lakes and ponds

Lakes and ponds can range in area from a few square meters to thousands of square kilometers. Temperature is an important abiotic factor affecting living things found in lakes and ponds. In the summer, thermal stratification of lakes and ponds occurs when the upper layer of water is warmed by the sun and does not mix with deeper, cooler water. Light can penetrate within the photic zone of the lake or pond. Phytoplankton (algae and cyanobacteria) are found here and carry out photosynthesis, providing the base of the food web of lakes and ponds. Zooplankton, such as rotifers and small crustaceans, consume these phytoplankton. At the bottom of lakes and ponds, bacteria in the aphotic zone break down dead organisms that sink to the bottom.

Questions & Answers

simple definition for respiratory system
Gift Reply
Respiratory system is a network of organs and tissues that helps you to breathe or help in getting the rids of oxygen and discharge of carbon dioxide in the body.
Ruhiyatu
how is a aerenchyma tissue adapted to its function
fatuma Reply
what does DNA mean
innocent Reply
dioxiribo nucleic acid
Lekan
what is a zygote
Victor Reply
zygote is developed or fertilized egg cell
Lekan
what is the difference between cell wall and cell membrane
Ruhiyatu Reply
cell wall is found in plant while cell membrane is found in animal cell
Lekan
please this is the main answer to that question okay Cell wall gives shape and support to the cell whiles Cell membrane support the movement of substances into and out of the cell. This question is very tricky that's why I asked.
Ruhiyatu
how cell I form
Elijah Reply
what difference between animal cell and plant cell
Lazarus Reply
what is animal call
Rita
Animal cell does not have a cell wall but plant cell have a cell wall
Ruhiyatu
plant have cell Wall well animal have not cell wall
Yula
what is fertilization?
Muhamed Reply
Fertilization is the fusion of male sex cell and female sex cell to form a zygote.
Ruhiyatu
What kind of nutrients is composed of plants
Annie Reply
phosphorus,potassium,nitrogen
Kritika
NPK
Ruhiyatu
what is hormones
Igwe Reply
hormon is the chemical messanger
Sneha
Genes can make someone dull?
Taperah
21ecological instrument and their diagrams
Ayomide Reply
cell biology
Muhamed
I am sorry
onuoha
for wat
ezeadaugo
no reason
KP
nothing but speculate
KP
Sorry without reason is nothing but speculate
Leilah
what are the kidney disease
Immaculate Reply
kidney stones
Gracelyne
it is a disease that affects the kidney
Miriam
what are some lung diseases
Gracelyne
kidney cancer
Victor
what is micro-organism
Jackson Reply
what is the hypothesis
Jackson
hypothesis is a proposed explanation for a phenomenon
Miriam
hypothesis is raw materials
KP
what is biology
KP
biology is the study of living things and their interaction with their environment
Miriam
what is zyogot?
Muhamed
what is fertilization?
Muhamed
zygote is an unfertilized eggs
KP
fertilization refers to the fusion of a sperm and ovum
KP
organs that can't be seen physically
Victor
what does mean stigma
Amira Reply
the stigma receives pollen grains during pollination
Ruhiyatu
what is the full of the MOST dangerous disease in the world where one stops sleeping and just dies :Hint ; FFI
God Reply
fatal familial insomnia which affects the thalamus
Miriam
there are other dangerous diseases like CAD i.e coronary artery disease
Miriam

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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