Dissolved inorganic nutrients in a reef lagoon influenced by submarine groundwater discharge in the Mexican Caribbean

Abstract

Submarine groundwater discharge (SGD) worldwide has been considered an important source of dissolved inorganic nutrients, pathogens, and terrestrial materials transported from land to sea. However, nutrient behavior associated with SGD in the Mexican Caribbean has long been ignored. Here, we investigate the variability in nutrient and pathogen distribution during a neap-spring diurnal cycle in the Nohoch-Teek fringing reef influenced by SGD during the “nortes” season. The spatio-temporal behavior of nitrate and silicate followed three patterns during a neap-spring diurnal cycle: 1) An increasing trend from the beginning to the end of the day; 2) A spatial gradient with decreasing values from SGD-Teek towards the coral reef; and 3) The highest concentrations in the SGD-Teek and southwest of SGD-Teek. No significant differences were recorded in the temporal behavior (p > 0.05); however, the highest concentrations were observed during the lowest spring tide. The ammonium exhibited an increasing trend from the beginning to the end of the day. Significant differences were recorded regarding temporal behavior, with variations during the morning and afternoon of both spring and neap tides, with the highest concentrations recorded in the afternoon. The spatial distribution of phosphate was more homogeneous. The presence of pathogens was evidenced in addition to the variation in the spatial and temporal behavior of nutrient input through SGD. The correlation between salinity and water level suggests that sea level variations influenced the flow. Silicate as tracers proved efficient, showing a predominant flow towards the southwest during both neap and spring tides, with the maximum extent recorded during the spring tide.