Water quality change in the Mississippi River, including a warming river, explains decades of wetland plant biomass change within its Balize delta

Ecosystem properties of riverine wetlands are known for high inter-annual variability. This multi-decadal study within the wetland complex of the Mississippi River's Balize Delta, USA assesses how river parameters (temperature, discharge, and sediment load) impact wetland plant biomass over time and space. The Mississippi River's annual temperature has increased 0.9 degrees C/decade, while discharge and sediment load has varied without trend over the same period. End-of-season herbaceous biomass increased 14 g/m(2)/year between 1988 and 2008, extrapolating to large (m-ton) area-wide increases. The river's temperature, discharge and sediment impacted the Delta's biomass in two ways: the increase in temperature had a positive impact on the growing season length which increased biomass; whereas discharge and load had negative impacts affecting the inter-annual variation without a temporal trend. The results explain natural variability in ecosystem processes in a dynamic deltaic system and likely trace a signal related to both climate warming and land use change within the drainage of the Mississippi River. The discovered decadal increase in herbaceous biomass has implications on carbon storage in the inshore and offshore receiving basins of the world's riverine wetlands experiencing longer growing seasons. (C) 2016 Elsevier B.V. All rights reserved.