**3. Conclusions**

The e ffects of eutrophication have become particularly evident in the TWs worldwide from the 1970s [15,19]. The progressive deterioration of TWs and the concurrent loss of ecosystem services induced National and International authorities to act, protecting and restoring these habitats (US Clean Water Act, European Water Framework Directive, and the National Water Act in South Africa). At present, the positive results of the interventions counteracting the eutrophication phenomenon can be observed and confirmed by the good responses of aquatic vegetation, benthic fauna and nekton [15,17,19,20]. However, other significant threats to TWs are recently requiring attention, such as (i) the impact of climate changes determining alterations of hydrodynamism and of freshwater supply [14,18,22], (ii) the constant loss of morphological structures [23], (iii) the impact of alien and invasive species [19,23]. Climate changes are altering salinity regimes causing unbalances in the biological communities [20,21] and, hence, requiring interventions to manage the freshwater inputs [20,22]. In the framework of climate changes, the understanding of air–sea CO2 exchange flux is

of particular importance [14], because TWs can either be a source or a sink of atmospheric CO2. The loss of habitat morphological features is related to both sea level rise and anthropogenic exploitation and requires urgen<sup>t</sup> actions to save the vocational habitat of numerous aquatic species [23].

TWs require concrete managemen<sup>t</sup> policies to prevent further deterioration and to plan the needed recovery interventions. Aiming at supporting this decisional process, the usefulness of biological communities to assess ecological conditions under anthropogenic impacts are widely described [17–19,23,24].

**Funding:** This research received no external funding.

**Acknowledgments:** I am thankful to all authors that contribute with their research articles to enrich this special issue. A special thanks goes to the MDPI *Water*'s Editorial Office, to Vanessa Sun and to all the reviewers and Academic Editors that dedicated their time and expertise in the manuscript revisions.

**Conflicts of Interest:** The author declares no conflict of interest.
