AME 68:159-169 (2013)  -  DOI: https://doi.org/10.3354/ame01607

ABSTRACT: We conducted 158 bioassays to determine phytoplankton growth limitation in the northern Gulf of Mexico and made the following observations. Light limitation occurred where salinity was <20; at higher salinities, phytoplankton biomass yield became mostly limited by N or by a co-limitation of N plus P (NP). The number of N-limited bioassays was 5 times greater than the P-limited bioassays. NP synergism occurred where salinity was >20, and represented 59% of all samples that were not light-limited. The interaction of N and P co-limitation was frequently synergistically additive, i.e. the combined effects of N and P limitation together created a greater response than the sum of either separately. The dissolved inorganic nitrogen:phosphate ratio (DIN:Pi) and various concentrations of DIN and Pi did not offer reliable chemical boundaries describing likely areas of exclusive N or P limitation in these bioassays. We conclude that reducing N loading to the shelf is a prudent management action that will partially remediate eutrophic conditions, including those that lead to hypoxia, but the omission of a concurrent reduction in P loading would be shortsighted.

KEY WORDS: Nutrient limitation · Algal community · Eutrophication · Hypoxia · N:P ratios · Mississippi River

Full text in pdf format

Cite this article as: Turner RE, Rabalais NN (2013) Nitrogen and phosphorus phytoplankton growth limitation in the northern Gulf of Mexico. Aquat Microb Ecol 68:159-169. https://doi.org/10.3354/ame01607 Export citation Share:    Facebook - - linkedIn