A review was conducted of nitrogen and phosphorus loadings and of concentrations entering and leaving natural and engineered wetland ecosystems, including alluvial swamp ecosystems in south Louisiana, sewage treatment systems and riparian buffer strips. The general observation is that there is a maximum nutrient uptake (retention) which can be saturated at high loading rates, and there may be a net nutrient release at low loading rates. The percent nitrogen and phosphorus retention in alluvial swamp forests is usually much lower than that observed in wetland wastewater systems. This difference may be because, in comparison to sewage treatment wetlands, natural wetland systems have relatively low nutrient concentration in the influent, a short duration of the overland flow water (<2 weeks), a larger size, and smaller belowground flows. Thus both nutrient concentration and nutrient loading can affect the percent TN and TP removal rate of water flowing over wetlands. These results support the conclusion that strategic wetland restoration for water quality improvement in the Mississippi River watershed will be best in small streams near the pollutant source where the concentration is relatively high, and will be much less beneficial where the nutrient loading is near a 'background' concentration and the loading rate is low. Although raising water levels to increase the loading for water with low nutrient concentrations is one water management option, that action may have the effect of compromising tree production and other ecosystem attributes.