Limiting Nutrients in Freshwater and Marine Systems

Subject: Environment
Pages: 1
Words: 256
Reading time:
< 1 min

Marine ecology allows for a stoichiometric determination of the ratios of key elements necessary to support life in aquatic ecosystems. For this purpose, the Redfield ratio has traditionally been used, numerically setting the ratio of carbon, nitrogen, and phosphorus as 106:16:1. It is worth noting that this stoichiometric proportion is actual for different zones of marine ecosystems, among which phytoplankton biomass and water column samples. The sources of this stability have not yet been established, but potential predictors of the Redfield ratio are the constancy of the water’s chemical composition and the biomass’s comfortable conditions.

Since most sunlight cannot penetrate to the bottom, the bulk of aquatic ecosystem biomass is concentrated in the upper layers of water, and thus the productivity of the entire ecosystem is directly dependent on nutrient input here. Elemental phosphorus and nitrogen are the primary limiting nutrients for most ecosystems, but there is a difference between freshwater and marine water. First of all, freshwater bodies of water have richer biodiversity due to more sparing conditions for organismal development. Secondly, phosphorus and nitrogen are very strictly limiting for freshwater systems, whereas the presence of nitrogen in seawater was not as critical. In other words, phosphorus is a more critical limiting agent for freshwater and nitrogen for marine waters. A likely source of this phenomenon is a large amount of sulfate in seawater, which initiates hydrolysis of iron sulfides with intermediate phosphate formation. Thus, excess phosphorus is present in marine systems, and thus nitrogen deficiency is key.