**5. Concluding Remarks**

Understanding the trophic response of the community to eutrophication and depicting the structure of food webs in coastal lakes is still problematic [14], mainly due to the extraordinary biological diversity and complexity of the potential trophic links between species [2,86,87]. In our study, the stable isotope analysis of carbon (δ13C) and nitrogen (δ15N) provided an effective approach with which to (1) track the propagation of anthropogenic nutrient inputs along food chains, (2) evaluate the relative contributions of food sources to fish diets, and (3) quantify the trophic relationships between organisms [31,37,62,87–89]. Here, the diet resulting from the application of the method recently proposed by Rossi et al. [31] substantially improved our ability to understand the response of communities to increasing eutrophication, as well as its effect on the feeding behaviour and food choices of important fish species in Mediterranean coastal lakes. Together, our results confirm food web theory as a powerful approach for obtaining valuable information for the managemen<sup>t</sup> and conservation of these complex and productive ecosystems.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2076-3417/10/8/2756/s1, Figure S1: Isotopic niche biplots of the community in each lake, Table S1: Carbon (δ13C) and Nitrogen (δ15N) Isotopic signature and abundances (n◦ Ind./m2) of invertebrate in each lake, Table S2: Contingency table for Invertebrates (Total Individuals) community composition in each lake, Table S3: Contingency table for fish (Total individuals) community composition in each lake.

**Author Contributions:** Conceptualisation, Supervision and Funding Acquisition: L.R. and M.L.C.; Field sampling: E.C. and G.C.; Investigation: S.S.C., E.C., G.C., F.F. and D.M.; Formal analysis and Visualisation: S.S.C. and G.C.; Writing—Original Draft Preparation: L.R., M.L.C., S.S.C.; Writing—Review & Editing: All Authors. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by: SAMOBIS-project granted by Provincia Latina, PNRA-2015/AZ1.01 (M.L. Costantini) and PNRA16\_00291 (L. Rossi) granted by MIUR-PNRA and the APC was funded by Progetti di Ricerca di Ateneo-RM11916B88AD5D75 (E. Calizza).

**Acknowledgments:** This work was supported by Latina Provincial Administration (Project: SAMOBIS), PNRA-2015/AZ1.01 (M.L. Costantini) and PNRA16\_00291 (L. Rossi). We thank Mr. George Metcalf for revising the English text.

**Conflicts of Interest:** The authors declare no competing interests.
