Imad,

Past research since 1970s into the eutrophication of coastal marine waters has demonstrated that nitrogen is the key limiting factor to algal production and eutrophication. In contrast phosphorus has been shown to be the limiting factor in freshwater systems. I have attached a few studies that should provide you enough information on the subject. The paper by Cha et al 2016 should be of great interest to you since it does shed some new light into the N-P relationship. The paper by Moore et al 2013 is an excellent review of our current knowledge on nutrient limitation in marine systems.

Cheers,

Tomas

ps: Redfield ratio is 106C:16N:1P

N:P in marine waters is usually in 10:1 & as compared to Nitrogen, Phosphates takes longer time for its recycling. Hence it is P which is a limiting factor in phytoplankton production, generally. Very rarely the limiting factor is N.

Thank you Mr. Chandravadan

Please are you have reference documented that N:P ratio in marine is 10:1

Regards 

Imad,

Past research since 1970s into the eutrophication of coastal marine waters has demonstrated that nitrogen is the key limiting factor to algal production and eutrophication. In contrast phosphorus has been shown to be the limiting factor in freshwater systems. I have attached a few studies that should provide you enough information on the subject. The paper by Cha et al 2016 should be of great interest to you since it does shed some new light into the N-P relationship. The paper by Moore et al 2013 is an excellent review of our current knowledge on nutrient limitation in marine systems.

Cheers,

Tomas

ps: Redfield ratio is 106C:16N:1P

Thank you very much Tomas 

I am agree with you the ratio is 16:1 and some reference 15:1 .The attached files is very rich with information about N & P I will read its good to understand which is controlling factor. I think P is limiting one in marine environment but not sure?

 Regards

Imad 

I agree with tha answer of Prof. Tomas Tomascik.

Regards

SM Najim

During my doctoral research on aquatic ecosystems in Aral Sea Basin I have revealed that Nitrates were always in enough concentrations for the normal development of aquatic flora (my Doctoral Dissertation Thesis, 1995). However, in some lakes Phosphorus was detected only in trace concentrations near to absence especially in central open parts situated far from water inflow. Therefore, I have concluded that Phosphorus is a main limiting macro element in lake ecosystems.  So, Dr. Tomascik has right saying phosphorus is the limiting factor in freshwater waterbodies. I think that this is generally applicable to many freshwater ecosystems in various continents.

With best wishes, Bakhtiyor

Working on oligotrophic waters and on diazotrophic marine cyanobacteria I will say the ultimate limiting factor in marine system in order to initiate primary production is posphorous as diazotrophs are able to fuel the system in C and N by fixing cabone and nitrogen through phtotosynthesis and nitrogen fixation.

The attached paper by Smith 1984 is an excellent review on the subject, it is well worth the read to understand the complexities of the question.

Tomas

ps:  papers  by Elser 2007 and by Howarth and Marino 2006 are good reviews.

Thank you very mach Tomas

I agree with everything that was said.

Let me also sum up what Tyrell said in the attached paper (Which only applies for the global marine system).

On longer time scales, P is the only limiting factor while in shorter time scales, N is limiting.

The mechanism is the nitrogen fixation and de-nitrification which adjust N concentration to P concentrations to almost fit the Redfield ratios.

As always, when you go coastal the system becomes much more complex and more depended of external inputs.

Just to thank you all, and to Imad for asking this question, because it has derived in a very enriching discussing, from which many others, including me, can benefit. Thank you in particular to Tom for the explanation and references, and also to Yair, I agree with both. Let´s keep up the interaction!