Question

What are the key limiting macronutrients needed to support primary production in all aquatic ecosystems?  Explain what biological active molecules require these nutrients for synthesis in living cells.

Answer 1

Phosphorous is the key limiting macronutrient in aquatic systems for primary producers.
i.e. it is the major nutrient that is found in limiting concentrations and ultimately determines the growth and reproduction of organisms.
Phosphorous is absorbed in the form of H₂PO₄^- or HPO₄^-2 ions.
Phosphorous is a component of phospholipids and required for membrane synthesis.
Phosphorous is a component of nucleotides such as ATP and serve as energy molecules.
Phosphorous is a component of nucleic acids such as DNA and RNA.
It is also required for phosphorylation reactions in metabolic pathways.
It also serves as a post-translation regulation mechanism of proteins.

Nitrogen is also key limiting factor for primary producers in aquatic systems. It is required for the biosyntehsis of amino acids, proteins, and nucleic acids.
Phytoplanktons utilize phosphorous and nitrogen in 1:6 molar ratio.