The estuarine character of the Gulf of Nicoya, an embayment on the Pacific coast of Central America

Abstract

Hydrography and exchange processes in a tropical estuary, the Gulf of Nicoya, Costa Rica, are described from data collected in 1979 and 1980 . The measurements and analyses were made in both the dry season and wet season and include temperature, salinity, and density at twenty locations in the gulf and currents (over a semi-diurnal tidal cycle) at five locations . These new results enlarge on the early study by Peterson (1958) . Circulation in the lower gulf shows a marked east-west asymmetry due to the predominant runoff along its eastern shore from Rio Barranca and Tarcoles . The freshened surface water from the upper gulf combines with the runoff from these rivers and flows southward along the eastern side of the lower gulf . This flow is compensated by a northward flow of more saline water on the western side at all depths and on the eastern side along the bottom . The boundary between the southward and northward surface flow is marked by a strong salinity front in the rainy season . There is a rapid increase in tidal energy density toward the shoaling northern reaches of the lower gulf, between San Lucas Island and Puntarenas Peninsula . Enhanced mixing must accompany this increase, and direct measurements in the constriction between San Lucas and Puntaneras show that tidal mixing is dominant in transporting salt into the upper gulf against the freshwater runoff .

Evaluación de las concentraciones de <i>Escherichia coli</i> en <i>Crassostrea gigas</i> y agua de mar en dos zonas de cultivo de ostras ubicadas en el Golfo de Nicoya, Costa Rica

“…The salinity variation recorded in this study reinforces the observations by Peterson (1960) and Voorhis et al (1983), who established that this parameter is a seasonality indicator in the Gulf of Nicoya. Salinity in Punta Cuchillo and Punta Morales growing areas increased during the dry season.…”

Dinámica anual de tintínidos en las aguas estuarinas de dos áreas marinas de pesca responsable en el Golfo de Nicoya, Costa Rica

“…La disminución gradual de la salinidad, la temperatura desde inicios de la época lluviosa y la subsecuente elevación de estos parámetros conforme inicia la época seca podrían explicarse principalmente por los efectos de las precipitaciones asociadas a la época lluviosa (Solano-León, 2012), donde se da un incremento en el caudal del río Tempisque, el Barranca y el Grande de Tárcoles. Estos ríos tienen influencia directa en las zonas de estudio, aumentan el aporte de agua dulce y disminuyen la concentración de sal y temperatura del agua, además de la concentración de oxígeno en el agua (Brenes, León & Chávez, 2001;Brenes, 2001;Kress, León, Brenes, Brenner & Arroyo, 2001;Lizano & Vargas 1994;Voorhis, Epifanio, Maurer, Dittel & Vargas, 1983).…”

Trophic planktonic dynamics in a tropical estuary, Gulf of Nicoya, Pacific coast of Costa Rica during El Niño 1997 event

“…1). According to Voorhis et al (1983) two main regions may be identified: an external zone delimited to the south by the open ocean, and to the north by a line from San Lucas Island to Puntarenas peninsula; and a shallow internal zone which comprises the rest of the gulf. The external zone is bordered by a rocky coast with sandy beaches and its bottom drops abruptly toward the mouth.…”

“…The gulf dynamic structure is principally controlled by salinity variations (Peterson 1958, Lizano & Vargas 1994 and strong gradients in physical-chemical parameters during the rainy season. In particular, the internal region of the gulf behaves as an estuary, showing stratification during the rainy season because of reduction in surface salinity (Epifanio et al 1983). Lizano (1998) showed that the strong saline stratification in the internal region may have an important impact on fisheries in the gulf.…”

“…Lizano (1998) showed that the strong saline stratification in the internal region may have an important impact on fisheries in the gulf. The strong seasonal stratification also influences nutrients and dissolved oxygen dynamics (Epifanio et al 1983, Chaves & Birkicht 1994 which in turn leads directly to biological differences between the two regions of the gulf (see Vargas 1995). …”