Kim, H.; Son, S.; Montagna, P.; Spiering, B. and Nam, J., 2014. Linkage between freshwater inflow and primary productivity in Texas estuaries: Downscaling effects of climate variability.
The estuaries of Texas are lagoons that lie in a climatic gradient in the northwestern Gulf of Mexico (GOM). Estuaries located in the northeastern part of the Texas coast receive more rainfall than estuaries in the southwestern part, and consequently greater runoff and concomitant freshwater inflow. Extreme inter-annual variability of precipitation caused by El Niño Southern Oscillation (ENSO) events is another characteristic of the Texas coast. During El Niño periods, salinities in Texas estuaries decrease because of increased precipitation and increased freshwater inflow to the coast. During La Niña periods, salinities increase due to drier climatic conditions and reduced freshwater inflow. The combination of the climatic gradient and temporal variability of freshwater inflow drive changes in the frequency, timing, duration, and magnitude of river flows to coastal waters, which in turn control the salinity, nutrients, organic matter, and sediments in Texas estuaries. Chlorophyll biomass, as an indicator of primary production, was estimated from Moderate Resolution Imaging Spectroradiometer (MODIS) data from July 2002 to December 2011 for all Texas estuaries. The climate patterns in the Pacific Ocean delivers a cascading signal via freshwater inflow changes to estuaries that effects primary production subsequently. The maximum correlation was found at the 5th lag (month) with correlation coefficient (ρ) being 0.45 (NIÑO3.4 is fixed as a reference). The combination of the local climatic gradient and quasi-periodic natural variability in ENSO has been influencing estuarine ecosystem dynamics over decadal scales in this region. The present study demonstrates that freshwater inflow is an important driver in maintaining primary productivity of Texas estuaries, which is required to maintain estuarine health and sustainability.