Short-term spatial and temporal variation of sediment oxygen dynamics in a tropical tidal salt flat

Abstract

Short-term spatial and temporal heterogeneity of oxygen dynamics and net primary production were studied in a tree day diurnal variation at a tidal tropical salt flat in the estuarine system of Sepetiba/Guaratiba coastal plain, Rio de Janeiro, Brazil. Oxygen concentrations were measured in situ with high temporal and spatial resolution oxygen microsensors. The results showed a remarkable heterogeneity of both oxygen penetration depth (from 0.18 to 0.85 cm) and net primary production (from -0.085 to 0.115 lmol O 2 cm -2 s -1 ) at different stations and sampling periods. Fast variations in abiotic factors like salinity and light due to the variable rainy weather were possibly the drivers of the high heterogeneity. In conclusion, short-term temporal changes could have a remarkable influence in sediment microalgae primary production. Not considering these changes can lead to wrong conclusions concerning the role and importance of sediment microalgae on tidal salt flats.

Primary production and respiration of hypersaline microbial mats as a response for high and low CO<sub>2</sub> availability

“…Since the light intensity used in our microcosm study is common in field conditions (especially in the tropics) and the CO 2 concentrations are close to our actual and projected future atmospheric conditions (380 and 550 ppm, respectively), we suggest that phototrophic communities in aquatic shallow ecosystems can be carbon limited. Field studies in a tropical tidal salt flat revealed repeated flattened oxygen profiles during day time (Oliveira et al, 2011), corroborating our suggestion.…”