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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 .
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]
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.
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 ...
In a few days, the sac fry will absorb the yolk sac and start feeding on smaller plankton. Ichthyoplankton are the eggs and larvae of fish. They are mostly found in the sunlit zone of the water column, less than 200 metres deep, which is sometimes called the epipelagic or photic zone.
The ocean's surface is hit hard by anthropogenic change, and the surface ecosystem is likely already dramatically different from even a few hundred years ago. For example, prior to widespread damming, logging, and industrialisation, more wood may have entered the open ocean, [ 14 ] while plastic had not yet been invented.
They are mostly found in the sunlit zone of the water column, less than 200 metres deep, which is sometimes called the epipelagic or photic zone. Ichthyoplankton are planktonic, meaning they cannot swim effectively under their own power, but must drift with the ocean currents. Fish eggs cannot swim at all, and are unambiguously planktonic.