Chemical and Physical Observations in Golfo, Dulce, an Anoxic Basin on the Pacific Coast of Costa Rica1

Golfo Dulce is an embayment containing small concentrations of hydrogen sulfide near the bottom due to sulfate reduction. The processes of denitrification, nitrate reduction, and organic decomposition are also evident. Hydrographic data taken 8 days apart indicated an influx of ocean water into the basin. It appears from past observations in the eastern tropical Pacific that the basin erratically receives ocean water during winter and spring.