Hidrografía y plumas estuarinas en Golfo Dulce, Pacífico Sur de Costa Rica

Abstract

Variables oceanográficas en 33 estaciones en el Golfo Dulce, Costa Rica, entre 2009 y 2010 fueron analizadas a través de perfiles con CTD, donde la salinidad, la temperatura, sigma-T y las corrientes se estudiaron en la columna de agua. Disco Secchi y clorofila-a, fueron medidos a nivel superficial.. El objetivo fue estimar el área de dispersión de las plumas estuarinas a través del seguimiento de las variables físicas temperatura, salinidad y sigma-T. En agosto 2009, entre los ríos Coto Colorado y Esquinas disminuyeron la salinidad (<30) en un área de 250km2 aproximadamente, un 37% de la superficie total, creándose frentes termohalinos a lo largo de casi todo el golfo. Se documentó el efecto de El Niño Oscilación del Sur en enero 2010 durante su fase de acentuada intensidad. Las concentraciones de clorofila-a se correlacionaron en un 33.7% (P=0.05) con la transparencia del agua según el disco Secchi en la estación lluviosa. Se caracterizó el agua superficial del Golfo Dulce por tener salinidad <31.5 temperatura >27ºC y ocupar los cinco primeros metros de la columna de agua.

Habitat suitability and area of occupancy defined for rare New World sea snake

“…Additionally, we inspected long-term average sea surface temperature and salinity variables from the MARSPEC dataset (Sbrocco & Barber, 2013) but did not include them in our models as the raster resolutions were considerably courser than our data and on the local level values were found to be inconsistent with the literature for Golfo Dulce: waters near a northern rivermouth represented the highest salinity with lower salinity nearer the open ocean, and SSTs were ≤4 C cooler than those reported in situ (23.0-30.0 C vs. 26.9-32.5 C per Acuña-Gonz alez et al, 2006;Morales-Ramírez et al, 2015;Rinc on-Alejos & Ballestero-Sakson, 2015). Traditional bioclimatic variables were downloaded from WorldClim version 2.1 (Fick & Hijmans, 2017) but were not used as the resolutions of those projections were too broad to spatially divide our small area of study.…”

“…Freshwater drainage from multiple rivers feeds the marine environment (Umaña‐V, 1998) and relative to the ocean's average salinity of 35 ppt, measurements in Golfo Dulce are low at <32 ppt, sometimes dropping to <21 ppt near large river outlets during the rainy season (Acuña‐González et al, 2006; Rincón‐Alejos & Ballestero‐Sakson, 2015). Sea surface temperatures (SST) in Golfo Dulce vary but remain relatively warm, averaging approximately 30°C and occasionally reaching 32.5°C (Rincón‐Alejos & Ballestero‐Sakson, 2015) as compared with SST of 28.3–28.6°C in the adjacent Pacific (Wellington & Dunbar, 1995; Rasmussen et al, 2011a, 2011b; Lillywhite et al, 2015). Dissolved oxygen levels in the inner basin are generally higher near the surface, decreasing with depth, and are considered anoxic below about 100 m depth (Dalsgaard et al, 2003).…”

“…Oxygen concentrations reach ≃0 in waters 150–180 m deep (Richards et al, 1971; Acuña‐González et al, 2006; Morales‐Ramírez et al, 2015). Turbidity has historically been assessed with a Secchi disc and measurements in Golfo Dulce have suggested temporal variance: during the dry season, lower turbidity readings are obtained in the deeper midwaters with higher readings nearest the shoreline, especially at rivermouths, while in the rainy season river output increases turbidity throughout the embayment (Rincón‐Alejos & Ballestero‐Sakson, 2015).…”

Safe from sunburn: The divergent diel pattern of a Hydrophis sea snake

“…Although SST does not fully describe the thermal environment, we measured an average of 29.2°C, with the daytime average only 0.3°C higher than at night. Importantly, at the height of the dry season, SST in Golfo Dulce can surpass 32°C (Rincón‐Alejos & Ballestero‐Sakson, 2015, Bessesen 2015), and while the critical thermal maximum for H. p. xanthos is unknown, its parent taxon, H. p. platurus , has a reported maximum of 33–36°C (Dunson & Ehlert, 1971; Graham et al, 1971). A black dorsum collects heat when exposed to sunlight (Graham, 1974), and diurnal foraging naturally increases that exposure.…”

“…Combining dry and rainy season data, SST in Golfo Dulce can average ~30°C (Rincón‐Alejos & Ballestero‐Sakson, 2015), compared with an average of ~28°C in the neighboring Eastern Tropical Pacific (Rasmussen et al, 2011; Wellington & Dunbar, 1995). Conversely, salinity in Golfo Dulce is lower at ≤31.9 ppt (Rincón‐Alejos & Ballestero‐Sakson, 2015) compared with the oceanic standard of 35 ppt, probably due to the influx of freshwater from four large rivers and numerous tributaries (Wolff et al, 1996). Annual day‐length variation in Costa Rica is minimal (~1 h; Rivera & Borchert, 2001), and during the diel survey, the photoperiod only changed by 15 min, with sunrise shifting from 05:39 h to 05:24 h and sunset remaining constant at 17:50 h.…”