Hydro-climatic Changes: Potential Effects on Nutrient Dynamics in Wetlands.

Depending on resilience, threshold and lag times, hydro-climatic changes may cause nonlinear and/or irreversible changes in aquatic systems. Thus, the studies of the influence of potential global climate change and its impacts on nutrient dynamics in wetlands are in critical need to help manage/increase the resilience of wetlands against any adverse irreversible changes in the ecosystem and its services. Nutrient dynamics in wetlands are likely to behave nonlinearly due to potential hydro-climatic changes in the decades to come. The critical question, such as, is not how much P is stored in a wetland, but how the resilience/nonlinearity relate to the stability of stored P. Studies, related to ³¹P NMR, show that a significant increase in P availability in wetlands could occur due to high levels of low stability P compounds (e.g., glycerophosphates/nucleoside monophosphates). Similarly, P flux from sediments to the water column depends on the concentration gradients of the sediment-water interface, as well as the redox status. A case study showed that P sorption maxima (S_max,) of the sediments were relatively high (up to 1667 mg kg^-1) so as the equilibrium P concentrations (0.09 -0.24 mg L^-1), indicating substantial amount of P may remain available for biological uptake in the water column. Moreover, high percentages of hysteretic P (>96%), along with a significant correlation between S_max and oxalate-extractable Fe (r=0.89), suggest that changes in sediment/water chemistry, e.g, redox status/acidity, could cause massive P release to the water column. Results also indicate that due to high activities of extra-cellular nitrate reductase and other enzymes associated with N transformations in sediments and waters, substantial amounts of NH₄⁺ and NO₃^- can be quickly lost from the systems as N₂O, NO and/or N₂, in turn, create N limited conditions in estuaries and marshes.