3.1 Intertidal and Estuarine Ecosystems. Flashcards
What is the intertidal zone also called?
Littoral zone.
The ________ zone is the area of a beach that is above the tide line and is occasionally splashed by waves and wind, but is never completely covered by the ocean
Spray.
The ________ zone is the area of a beach that is covered by the ocean during high tides, but is dry for long periods of time between tides.
High intertidal.
The ________ zone is the area between the average high and low tide marks on the coast where land and sea meet.
Mid intertidal.
The ________ zone is the area between the average and lowest low tide levels on the shoreline where land and sea meet.
Low-intertidal.
Estuaries contain salt water and fresh water, so they circulate and mix but sometimes, the upper and lower layers of water may experience a high difference in density. This may prevent the layers from mixing. This ends up in a phenomenon called _________.
stratification
Stratification can be dangerous for marine organisms because it prevents dissolved oxygen from mixing between layers.
These cycles occur every year and mostly depend on the seasons. Seasonal changes in temperature cause changes to the water temperature. Changes in estuarine water temperature may lead to migration of certain species. Temperature changes can also affect the currents in an estuary.
Annual cycles.
Cycles that occur daily are based on conditions that change through the course of the day, such as sunlight. The change in the amount of available sunlight can affect the growth of phytoplankton. This, in turn, has an effect on the levels of dissolved oxygen and chlorophyll in the water.
Daily cycles.
______ cycles depend primarily on the location of the Moon. Tides move salt water into the estuary during high tide. Low tides see a rise in concentrations of fresh water. The changes in salinity can also affect the organisms that reside in the estuarine zone.
Tidal cycles.
This is the zone characterized by the point where fresh water starts to become saline. It is also referred to as the river head. This is the least saline zone of the estuary, having a salinity of about 0.5 to 5 ppt (parts of salt per thousand parts of water). The sea bed in this zone consists of fine gravel. Good water circulation ensures the mixing of oxygen and nutrients. This allows life to thrive in this zone. Bottom dwellers include oysters, clams, sea stars, and so on. Fresh water migrant species can also be found in this zone. The upper layers host fish, sea jellies, and dolphins. This zone is also home to many small and large sea plants. Some fresh water species can also be found in this zone due to its low salinity. Ducks and geese can also be found hunting in this zone.
Oligohaline.
This zone has a higher salinity between 5 and 18 ppt. It is a more balanced mixture of fresh and sea water. The estuarine bed is mainly made up of mud with minimal currents. This zone is usually marshy, with tall grass that forms a food source for herbivores. This zone is home to mussels and crabs, as well as many small fish. Ducks, geese, otters, raccoons, and other animals that subsist on fish can be found hunting in this zone.
Mesohaline
The next zone has a salinity range between 18 and 30 ppt. The estuarine bed consists of mud with some sand. If the estuary experiences strong tidal currents, then the tide will bring in large amounts of sand. Such estuaries therefore have a higher concentration of sand. The creatures found in this zone are called euryhaline organisms. These creatures can live in both fresh as well as saline water. Some common creatures include green crab, salmon, eels, and so on. Life in this zone is very diverse; it can also include creatures that have migrated from the sea, such as salmon that travel upstream in order to spawn. Mangroves are also common in this zone. Mangroves are important trees that grow as forests in brackish water. They are characterized by large supporting stilt roots and aerial roots that grow above the ground. These roots provide shelter for many creatures.
Polyhaline
This zone forms the mouth of the river and has the highest salinity. The salinity of this zone ranges from 30 to 35 ppt. The estuarine bed is characterized by rock or sand. Creatures found in this zone are mostly marine or stenohaline. Stenohaline creatures cannot tolerate major changes in salinity and therefore do not move upstream. These species develop other mechanisms to deal with changing salinity levels, such as burrowing, moving, or some protective mechanism. For example, worms and mollusks can release slime to protect themselves from slight rises in salinity. The high salinity is not conducive to the growth of mangroves. This zone has the highest number of species as compared to the other zones. Some species include delta clams, oceanic jelly, moon jelly, salt water cordgrass, and so on.
Euhaline
