Shallow gas seeps in the Golfo Dulce, South Pacific of Costa Rica: geological, physicochemical, and biological characterization

Abstract

Abstract Methane is a greenhouse gas with a heat absorption capacity 25 times greater than CO2, potentially playing a significant role at the atmospheric level. Thus there is a growing interest about studying the diversity and ecology of habitats that are important contributors of this gas to the atmosphere. This research aims to carry out a geological, physicochemical, and biological description of a superficial gas seepage in the tropical waters of the Golfo Dulce in Costa Rica. To study this environment underwater visual censuses of fish and bottom cover were conducted, along with collection of water samples for nutrient analysis, and gas to determine the composition of emissions. In addition, rock samples were collected to determine the geological origin and the associated cryptofauna. The seeps are composed of 49.5% methane and the rock that makes up the platform is sandstone from the Charco Azul Group. The bottom cover is dominated by sand (20%), hydrozoans (18%), and 12% of the «other» category. A total of 18 species of fish were found, and wrasses (Labridae) were the dominant group. Regarding cryptofauna, a total of 93 taxa were recorded. This study presents a new report of the ghost shrimp Biffarius for the Eastern Tropical Pacific. This ecosystem presents unique features because it is a shallow, highly diverse place, with a structure of the biological community different from what it is known for the Pacific coast of Costa Rica and the region. Knowing the above, it is recommended to establish conservation strategies.