Editing Limiting factor (section)

== Oceanography ==
In oceanography, a prime example of a limiting factor is a '''limiting nutrient'''. Nutrient availability in freshwater and marine environments plays a critical role in determining what organisms survive and thrive. [[Nutrient|Nutrients]] are the building blocks of all living organisms, as they support biological activity. They are required to make proteins, DNA, membranes, organelles, and exoskeletons. The major elements that constitute >95% of organic matter mass are carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. Minor elements are iron, manganese, cobalt, zinc and copper. These minor elements are often only present in trace amounts but they are key as co-limiting factors as parts of enzymes, transporters, vitamins and amino acids. Within aquatic environments, nitrogen and phosphorus are leading contenders for most limiting nutrients.

Discovery of the [[Redfield ratio]] was a major insight that helped understand the relationship between nutrient availability in seawater and their relative abundance in organisms. Redfield was able to notice elemental consistencies between carbon, nitrogen and phosphorus when looking at larger organisms living in the ocean (C:N:P = 106:16:1).<ref>{{Cite journal |last=Redfield |first=A.C. |date=1958 |title=The biological control of chemical factors in the environment," |url=https://ebme.marine.rutgers.edu/HistoryEarthSystems/HistEarthSystems_Fall2008/Week4b/Redfield_AmSci_1958.pdf |journal=American Scientist}}</ref> He also observed consistencies in nutrients within the water column; nitrate to phosphate ratio was 16:1. The overarching idea was that the environment fundamentally influences the organisms that grow in it and the growing organisms fundamentally influence the environment. Redfield's opening statement in his 1934 paper explains "It is now well recognized that the growth of plankton in the surface layers of the sea is limited in part by the quantities of phosphate and nitrate available for their use and that the changes in the relative quantities of certain substances in seawater are determined in their relative proportions by biological activity".<ref>{{Cite journal |last=Redfield |first=A.C. |date=1934 |title=On the proportions of organic derivatives in seawater and their relation to the composition of plankton |url=https://hahana.soest.hawaii.edu/cmoreserver/summercourse/2012/documents/bronk_05-30-12/Redfield_1934.pdf |journal=James Johnstone Memorial |pages=176–192}}</ref> Deviations from Redfield can be used to infer elemental limitations. Limiting nutrients can be discussed in terms of dissolved nutrients, suspended particles and sinking particles, among others. When discussing dissolved nutrient stoichiometry, large deviations from the original Redfield ratio can determine if an environment is phosphorus limited or nitrogen limited. When discussing suspended particle stoichiometry, higher N:P ratios are noted in oligotrophic waters (environments dominated by [[cyanobacteria]]; low latitudes/equator) and lower N:P ratios are noted in nutrient rich ecosystems (environments dominated by [[Diatom|diatoms]]; high latitudes/poles).<ref>{{Cite web |last=Benitez-Nelson |first=Claudia |date=2018 |title=The Building Blocks of Life: From Oceanic to Molecular Scales and Back Again |url=https://www.youtube.com/watch?v=i6aKqhZ_r5c&t=841s  |access-date=19 February 2023 |website=Youtube}}</ref> 

Many areas are severely nitrogen limited, but phosphorus limitation has also been observed. In many instances trace metals or co-limitation occur. Co-limitations refer to where two or more nutrients simultaneously limit a process. Pinpointing a single limiting factor can be challenging, as nutrient demand varies between organisms, life cycles, and environmental conditions (e.g. thermal stress can increase demand on nutrients for biological repairs).