Sediment oxygen consumption in a developed coastal lagoon of the Mexican Caribbean

摘要

Nichupte is estuarine lagoon connected to the Caribbean Sea by two channels with very high levels of organic carbon in sediments, which ranged from 1.56 to 9.29 %, with the maximum concentration at the northeastern zone, known as Bojorquez, a section with high greater anthropogenic impacts. The rate of sediment oxygen consumption (measured in the laboratory) during summer (July) was 292 mmol O_2 m~(-2) d~(-1) at Bojorquez, with a mean value of 70 mmol O_2 m~(-2) d~(-1). During winter (January), at the same site, the rate increased to 309 mmol O_2 m~(-2) d~(-1) (average 125 mmol O_2 m~(-2) d~(-1)). The total average for both seasons (summer and winter) was 97 mmol O_2 m~(-2) d~(-1). For the whole lagoon system (48.3 km~2), the total oxygen consumption by sediments was 4.6 x 10~6 mol O_2 d~(-1). During summer, the net input of oxygen from the sea to the lagoon was 1.6 x 10~5 mol O_2 d~(-1), decreasing towards winter (1.5 X 10~5 mol O_2 d~(-1)). The oxygen input from sea to lagoon, represented only 3 % of the oxygen consumed by sediments, indicating that, if some of the oxygen sources like photosynthesis or wind re-aeration are interrupted or diminished, hypoxia might occur, particularly at Bojorquez zone.