Abstract. In October 2017, the Sentinel-5 Precursor (S5P) mission was launched, carrying the TROPOspheric Monitoring Instrument (TROPOMI), which provides a daily global coverage at a spatial resolution as high as 7 km × 3.5 km and is expected to extend the European atmospheric composition record initiated with GOME/ERS-2 in 1995, enhancing our scientific knowledge of atmospheric processes with its unprecedented spatial resolution. Due to the ongoing need to understand and monitor the recovery of the ozone layer, as well as the evolution of tropospheric pollution, total ozone remains one of the leading species of interest during this mission.

In this work, the TROPOMI near real time (NRTI) and offline (OFFL) total ozone column (TOC) products are presented and compared to daily ground-based quality-assured Brewer and Dobson TOC measurements deposited in the World Ozone and Ultraviolet Radiation Data Centre (WOUDC). Additional comparisons to individual Brewer measurements from the Canadian Brewer Network and the European Brewer Network (Eubrewnet) are performed. Furthermore, twilight zenith-sky measurements obtained with ZSL-DOAS (Zenith Scattered Light Differential Optical Absorption Spectroscopy) instruments, which form part of the SAOZ network (Système d'Analyse par Observation Zénitale), are used for the validation. The quality of the TROPOMI TOC data is evaluated in terms of the influence of location, solar zenith angle, viewing angle, season, effective temperature, surface albedo and clouds. For this purpose, globally distributed ground-based measurements have been utilized as the background truth. The overall statistical analysis of the global comparison shows that the mean bias and the mean standard deviation of the percentage difference between TROPOMI and ground-based TOC is within 0 –1.5 % and 2.5 %–4.5 %, respectively. The mean bias that results from the comparisons is well within the S5P product requirements, while the mean standard deviation is very close to those limits, especially considering that the statistics shown here originate both from the satellite and the ground-based measurements.

Additionally, the TROPOMI OFFL and NRTI products are evaluated against already known spaceborne sensors, namely, the Ozone Mapping Profiler Suite, on board the Suomi National Polar-orbiting Partnership (OMPS/Suomi-NPP), NASA v2 TOCs, and the Global Ozone Monitoring Experiment 2 (GOME-2), on board the Metop-A (GOME-2/Metop-A) and Metop-B (GOME-2/Metop-B) satellites. This analysis shows a very good agreement for both TROPOMI products with well-established instruments, with the absolute differences in mean bias and mean standard deviation being below +0.7 % and 1 %, respectively. These results assure the scientific community of the good quality of the TROPOMI TOC products during its first year of operation and enhance the already prevalent expectation that TROPOMI/S5P will play a very significant role in the continuity of ozone monitoring from space.

IDENTIFYING THE MAIN STRUCTURE OF BENTHIC TROPHIC NETWORKS IS NECESSARY TO UNDERSTAND THE FUNCTIONING OF MARINE COMMUNITIES. FOR THAT PURPOSE, THE TRAINEE WILL ANALYSE NATURAL ¹³C AND ¹⁵N STABLE ISOTOPES AND FATTY ACID BIOMARKERS ON ECHINOID SPECIMENS TO ALLOW DISCRIMINATING AMONG THE FOOD SOURCES OF TARGET SPECIES, THE MEAN/BROAD POSITION OF THE TARGET SPECIES IN THE TROPHIC NETWORKS (FEEDING STRATEGIES), AND THE TROPHIC PLASTICITY OF THESE SPECIES. THREE TARGET ECHINOID SPECIES WITH ALREADY KNOWN A PRIORI CONTRASTED TROPHIC STRATEGIES WILL BE STUDIED: STERECHINUS DIADEMA, ABATUS CORDATUS, AND CTENOCIDARIS NUTRIX. ELEMENTAL (C/N) AND ISOTOPIC ANALYSES (¹³C, ¹⁵N) WILL ALSO BE PERFORMED ON DIFFERENT ORGANIC MATTER SOURCES (DISSOLVED ORGANIC MATTER OF SEA WATER, SEDIMENT ORGANIC MATTER, MACROALGAE) AND COMPARED WITH OTHER PRIMARY AND SECONDARY CONSUMERS (SPONGES, KEY MARINE INVERTEBRATES). THIS WILL BE COMPLETED BY DIGESTIVE TRACK CONTENT ANALYZES OF SAMPLED SPECIMENS.