**5. Conclusions**

The present study is one of the few investigations on the meiofaunal community structure, composition, and diversity conducted in transitional waters (TWs) in the Western Mediterranean Sea. The high environmental variability and habitat heterogeneity of the Cabras Lagoon, the largest TW in Sardinia, was reflected in significant di fferences in meiofauna among the study sites. Spatial di fferences in several faunal parameters (i.e., community structure, richness, Pielou-evenness, and Ne/co ratio) were stronger than temporal variation, suggesting that meiofaunal organisms are good indicators of the physical-chemical variation in TWs. Furthermore, the Cabras Lagoon showed high values of meiofaunal species richness further supporting the idea that TWs may be biodiversity hotspots and meiofauna is an important biotic component to understand their functioning.

**Author Contributions:** Conceptualization, F.S., M.F.G. and P.M.; methodology, F.S., M.F.G. and P.M.; formal analysis, F.S., M.F.G. and P.M.; data curation, F.S., M.F.G. and P.M.; writing-original draft preparation, F.S., M.F.G. and P.M.; writing-review and editing, F.S., M.F.G. and P.M.; visualization, F.S., M.F.G. and P.M.

**Funding:** We would like to thank Marcello Giorgi, University of Rome "Tor Vergata", for technical support in data analysis procedures.

**Acknowledgments:** We gratefully acknowledge the two reviewers whose comments greatly contributed to an improved version of the original manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.
