## 4 Conclusions  
Little data are available on _D. vermicularis_ chemical composition in the literature, except for polyphenols and coumarins analysis, and the present research is a comprehensive investigation of _D. vermicularis_ from the Adriatic Sea (Croatia) regarding VOCs and less polar nonvolatile compounds for the first time. VOCs from both fresh (FrDV) and air-dried (DrDV) samples were presented. Both HS-SPME and HD were used, showing a great variability among HS-FrDV and HD-FrDV, as well as among HS-DrDV and HD-DrDV. Utilising these two methods, VOCs of different polarities and volatility were isolated. There is clearly a noticeable difference in fresh (FrDV) and air-dried (DrDV) samples. Aromatic compounds were dominant in both fresh and air-dried HS samples with benzaldehyde and 2-phenylbut-2-enal as the most abundant in fresh samples. C\({}_{11}\)-hydrocarbons dictyopterpene C\({}^{\prime}\) and dictyopterpene D\({}^{\prime}\) were detected with great abundance in HS-FrDV. Aliphatic compounds were dominant in both HD-FrDV and HD-DrDV samples. In HD-FrDV, dictypene alcohols (cempka-4,7,11,15-tetraen-3-ol and (\(Z\))-falcarinol) and sesquiterpene alcohol cubenol were dominant. Its amount decreased, but C\({}_{13}\)-norisoprenoides (\(\alpha\)-ionone and \(\beta\)-ionone) increased during the air-drying process. The less polar compounds in F3 and F4 were analysed and identified by UHPLC-ESI(+)-HRMS. Identified compounds belonged to a group of pigments (7 compounds), fatty acid derivatives (13 compounds), as well as steroids and terpenes (10 compounds). Porphyrin-based compounds (C\({}_{55}\)H\({}_{74}\)N\({}_{4}\)O\({}_{5-7}\)), xanthophylls, sphingolipid compounds, fatty acid amides, and phytosterols represent the majority of identified compounds. In vitro analysis of the antioxidant potential of less polar compounds from _D. vermicularis_ by implementing five independent assays (Folin-Ciocalteu, FRAP, DPPH, ORAC, and ABTS) showed a high activity of both F3 and F4 fractions. F3 exerted a higher inhibition of reactive oxygen species than F4, which can be related to the presence of pigments, namely xanthophylls. When compared to the results obtained by in vivo analysis, F3 also showed protective effects against the H\({}_{2}\)O\({}_{2}\)-induced mortality of zebrafish embryos. The first results on _D. vermicularis_ suggest that this green alga might be a potent source of natural antioxidants such as pigments, terpen, and porphyrin-based compounds, and further research regarding different biological activities is in progress. Conceptualization, S.R., I.J., S.J. and S.B. ; methodology, S.R., A.-M.C., S.B. and L.C. ; formal analysis, I.J., S.R., S.J. and R.C.-R.; investigation, R.C.-R., I.J. and S.J. ; resources, I.J., S.J. and R.C.-R.; data curation, S.R., S.B. and L.C. ; writing--original draft preparation, S.R. and I.J. ; writing--review and editing, I.J., S.J. and R.C.-R.; supervision and funding acquisition, R.C.-R. All authors have read and agreed to the published version of the manuscript. This research was funded by the Croatian Government and the European Union through the European Regional Development Fund--the Competitiveness and Cohesion Operational Programme (KK.01.1.1.01) through the project Bioprospecting of the Adriatic Sea (K.K.01.1.1.01.001) granted to The Scientific Centre of Excellence for Marine Bioprospecting--BioProCro. Animal housing and spawning were performed in aquaria units approved by the Croatian Ministry of Agriculture and according to the Directive 2010/63/EU. All experiments in this study were conducted on the nonprotected embryonic stages (up to 96 hpf), which do not require permission by animal welfare commissions (Directive 2010/63/EU). Not applicable. Data Availability Statement: Data are contained within the article.