Distribución espacial y temporal de la salinidad en la columna de agua del sector estuarino del Humedal Nacional Térraba Sierpe, Costa Rica

Spatial and temporal salinity distribution in the water column of the estuarine sector of the Terraba Sierpe National Wetland, Costa Rica. The analysis of salinity data collected during three campaigns of monitoring (2002-2004, 2005-2008 and 2011-2012) in the estuarine sector of Terraba Sierpe National Wetlands (HNTS) was performed. The information collected allows to separate a northern zone with a strong influence of the Rio Grande de Terraba, which during the period of low flow (December-April) shows charac- teristics of a partially mixed estuary, while it resembles a salt-wedge estuary during intermediate and high flows rates (May-November). A central area with greater marine influence features a vertically homogeneous or well mixed estuary, while the south of the estuary has a balanced (intermediate) condition, through the contributions of the Sierpe river and the tidal regime, which confers characteristics of a partially mixed estuary. The statistical analysis model confirms variations in the salinity values in relation to tides, time of year (season) and the dis- tance along a longitudinal profile of 24km away from the town of Ciudad Cortes to the sea opening at Coronado mouth (F 1,47 =2.5, p<0.001). The first 7km downstream from Ciudad Cortes have a very well-defined fluvial condition with salinities below 1psu, in the sector of Viuda island, located 8km towards the sea, there is a range of variation in salinity values higher than 5psu; a final section that starts 14km towards the Coronado mouth shows a gradual increase in the salinity values up to 30psu reflecting a greater influence of the tides. The even- tual development of the El Diquis hydroelectric project could cause an increase in the contribution of freshwater between an 82-66% of the minimum and maximum average flow values over the northern part of the estuarine sector of the HNTS during the low flow periods, which would create similar conditions to those recorded dur- ing the intermediate flow rates. The provided analysis constitutes a first approach to the understanding of the estuarine dynamics of the HNTS. Analysis and monitoring of the relationships between the physical, chemical and biological aspects are essential for future discern between possible sources of changes in the estuarine sector of the HNTS and must be considered to be a firm commitment by the institutions involved in the management and conservation of this ecosystem. Rev. Biol. Trop. 63 (Suppl. 1): 75-96. Epub 2015 April 01.