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Furthermore, phosphorus tends to be a limiting nutrient in aquatic ecosystems. [7] However, as phosphorus enters aquatic ecosystems, it has the possibility to lead to over-production in the form of eutrophication, which can happen in both freshwater and saltwater environments. [8] [9] [10]
Nutrient cycle is more often used in direct reference to the idea of an intra-system cycle, where an ecosystem functions as a unit. From a practical point, it does not make sense to assess a terrestrial ecosystem by considering the full column of air above it as well as the great depths of Earth below it.
The limitation of productivity in any aquatic system varies with the rate of supply (from external sources) and removal (flushing out) of nutrients from the body of water. [14] This means that some nutrients are more prevalent in certain areas than others and different ecosystems and environments have different limiting factors.
In the very long term, phosphorus "is often considered to be the ultimate limiting macronutrient in marine ecosystems" [21] and has a slow natural cycle. Where phosphate is the limiting nutrient in the photic zone , addition of phosphate is expected to increase primary phytoplankton production.
However, marine ecosystems are too broad a range of environments for one nutrient to limit all marine primary productivity. The limiting nutrient may vary in different marine environments according to a variety of factors like depth, distance from shore, or availability of organic matter. [20] [19]
It may even be the case that the Redfield Ratio is applicable to terrestrial plants, soils, and soil microbial biomass, which would inform about limiting resources in terrestrial ecosystems. [12] In a study from 2007, soil and microbial biomass were found to have a consistent C:N:P ratios of 186:13:1 and 60:7:1, respectively on average at a ...
The seminal synthesis by Geider and La Roche in 2002, [101] as well as the more recent work by Persson et al. in 2010, [102] has shown that C:P and N:P could vary by up to a factor of 20 between nutrient-replete and nutrient-limited cells. These studies have also shown that the C:N ratio can be modestly plastic due to nutrient limitation.
Low-nutrient, low-chlorophyll (LNLC) regions are aquatic zones that are low in nutrients (such as nitrogen, phosphorus, or iron) and consequently have low rate of primary production, as indicated by low chlorophyll concentrations. These regions can be described as oligotrophic, and about 75% of the world's oceans encompass LNLC regions.