Photic zone
It undergoes a series of physical, chemical, and biological processes that supply nutrients into the upper water column.The photic zone is home to the majority of aquatic life due to the activity (primary production) of the phytoplankton.The thicknesses of the photic and euphotic zones vary with the intensity of sunlight as a function of season and latitude and with the degree of water turbidity.These phytoplankton grow extremely quickly because of sunlight's heavy influence, enabling it to be produced at a fast rate.[3] Ninety percent of marine life lives in the photic zone, which is approximately two hundred meters deep.Animals within the photic zone use the cycle of light and dark as an important environmental signal, migration is directly linked to this fact, fishes use the concept of dusk and dawn when its time to migrate, the photic zone resembles this concept providing a sense of time.Typical euphotic depths vary from only a few centimetres in highly turbid eutrophic lakes, to around 200 meters in the open ocean.It also varies with seasonal changes in turbidity, which can be strongly driven by phytoplankton concentrations, such that the depth of the photic zone often decreases as primary production increases.In between, the colours of the visible spectrum comprise the familiar “ROYGBIV”; red, orange, yellow, green, blue, indigo, and violet.[12] The ocean can be divided into depth layers depending on the amount of light penetration, as discussed in pelagic zone.Proxy data is used in order to relate elements collected in modern-day sedimentary samples to climatic and oceanic conditions in the past.Paleoclimate proxies refer to preserved or fossilized physical markers which serve as substitutes for direct meteorological or ocean measurements.In 2015, Swann and Snelling used these isotope records to document historic changes in the photic zone conditions of the north-west Pacific Ocean, including nutrient supply and the efficiency of the soft-tissue biological pump, from the modern day back to marine isotope stage 5e, which coincides with the last interglacial period.Peaks in opal productivity in the marine isotope stage are associated with the breakdown of the regional halocline stratification and increased nutrient supply to the photic zone.[15][16][17][18] The decrease of abyssal water upwelling associated with this may have contributed to the establishment of globally cooler conditions and the expansion of glaciers across the Northern Hemisphere from 2.73 Ma.Marine bacteria, algae, coral and most other organisms within the ocean release this, constituting a range of gene families.