The core was collected manually from a boat employing a gravity core sampler. The core was sliced every two centimeters in the field, packed in individual identified plastics bags, and kept refrigerated. The THIII sediment core (N 28°01.626, W 12°16.558), measuring 48 cm, was recovered in one of the sections of the main water entrance channel in the Lagoon. This site is approximately seven meters deep and lies between two islets of exposed sediment dominated by marine grass specimens of Zostera noltii. During the sampling, salinity at the site was 40 PSU (Practical Salinity Unit). Due to its proximity to the inlet, this site is highly influenced by the seawater entrance and ocean nutrients. Aiming the recognition of the environmental changes at this point of the lagoon, we have performed the following measurements in the core's sediments: isotopic ratio of C, dating (210Pb and 137Cs calibration), sedimentation rate, mean grain size, Chlorophyll, Total Organic Carbon (TOC), C/N elemental ratio and C/S elemental ratio.