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The photic zone (or euphotic zone, epipelagic zone, or sunlight zone) is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological processes that supply nutrients into the upper water column .
This is the most common form of vertical migration. Organisms migrate on a daily basis through different depths in the water column. Migration usually occurs between shallow surface waters of the epipelagic zone and deeper mesopelagic zone of the ocean or hypolimnion zone of lakes. [2] There are three recognized types of diel vertical migration:
A top-down cascade is a trophic cascade where the top consumer/predator controls the primary consumer population. In turn, the primary producer population thrives. The removal of the top predator can alter the food web dynamics. In this case, the primary consumers would overpopulate and exploit the primary producers.
Plankton have traditionally been categorized as producer, consumer, and recycler groups, but some plankton are able to benefit from more than just one trophic level. In this mixed trophic strategy—known as mixotrophy—organisms act as both producers and consumers, either at the same time or switching between modes of nutrition in response to ...
The surface waters are sunlit. The waters down to about 200 metres are said to be in the epipelagic zone. Enough sunlight enters the epipelagic zone to allow photosynthesis by phytoplankton. The epipelagic zone is usually low in nutrients. This partially because the organic debris produced in the zone, such as excrement and dead animals, sink ...
The bathyal zone is the lower section of the midwater zone, and encompasses the depths of 1,000 to 4,000 metres (3,300 to 13,100 ft). [23] Light does not reach this zone, giving it its nickname "the midnight zone"; due to the lack of light, it is less densely populated than the epipelagic zone, despite being much larger. [24]
One of the most well-known surface ecoregions is the Sargasso Sea, an ecologically distinct region packed with thick, neustonic brown seaweed in the North Atlantic. Multiple ecologically and commercially important species depend on the Sargasso Sea, but neustonic life exists in every ocean basin and may serve a similar, if unrecognised, role in ...
Seaweeds are found along coastal areas, living on the floor of continental shelves and washed up in intertidal zones. Some seaweeds drift with plankton in the sunlit surface waters (epipelagic zone) of the open ocean. Back in the Silurian, some phytoplankton evolved into red, brown and green algae.