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

Abstract

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 O₂ m⁻² d⁻¹ at Bojorquez, with a mean value of 70 mmol O₂ m⁻² d⁻¹. During winter (January), at the same site, the rate increased to 309 mmol O₂ m⁻² d⁻¹ (average 125 mmol O₂ m⁻² d⁻¹). The total average for both seasons (summer and winter) was 97 mmol O₂ m⁻² d⁻¹. For the whole lagoon system (48.3 km²), the total oxygen consumption by sediments was 4.6 × 106 mol O₂ d⁻¹. During summer, the net input of oxygen from the sea to the lagoon was 1.6 × 105 mol O₂d⁻¹, decreasing towards winter (1.5 × 105 mol O₂d⁻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.