Effect of Temporarily Opening and Closing the Marine Connection of a River Estuary

Abstract The lower Rio Grande is a river-dominated estuary that serves as the border between Texas, USA, and Tamaulipas, Mexico. River estuaries encompass section of river influenced by tidal exchange with Gulf Mexico, but connection intermittent can be temporarily open or closed. During 4.8-year study period, mouth was closed 30% time, mostly during average dry climatic conditions, temporary closing being linked to hydrology. When closed, salinity low (1.5 psu compared 4.8 when open), nitrate plus nitrite are (4.4 μM 31.5 ammonium high (9.6 4.3 chlorophyll similar (20 μg/L 21 open). Benthic macrofaunal abundance biomass higher closed: 16,700 individuals m −2 3.3 g 8800 2.4 open. community structure divided into two groups: chironomid larvae Oligochaeta dominated whereas polychaetes Mediomastus ambiseta Streblospio benedicti implications these results for managing freshwater flows conditions each have characteristic benthic strongly system