Small volumes of introduced freshwater can affect water and sediment quality in estuaries Hydrobiologia

The aim of this study is to evaluate the potential environmental benefits of hydrological conservation or restoration projects by quantifying the effects of small changes of inflow volumes on estuary ecosystem health. Discharge, water quality (indicated by nutrients and chlorophyll), and sediment quality (indicated by benthic communities) were sampled monthly at five stations in the upper reaches of the Guadalupe and Lavaca-Colorado Estuaries. Distinct oligohaline and mesohaline benthic communities were present in both estuaries. A positive correlation between multivariate water quality and benthic metrics indicates a positive relationship between small flow changes and estuarine health. The Guadalupe Estuary’s average monthly freshwater inflow rate was 92% higher than the Lavaca-Colorado Estuary, so a larger flow volume increase is necessary to affect estuarine health in the Guadalupe Estuary. This analysis indicates that an increased small volume, as low as 10% of freshwater inflow volume, can have positive benefits to estuarine conditions and health. Thus, hydrological protection or restoration projects based on small volumes can improve estuaries degraded by freshwater diversions. Grant no. NA21SEC4810004