**Preface to "A Glimpse into Future Research on Microalgae Diversity, Ecology and Biotechnology"**

Microalgae are photosynthetic unicellular microorganisms that represent an extremely important component of the aquatic ecosystem productivity, diversity, and functioning. Moreover, these microorganisms, using a network of signals, interact with all the other organisms present in their environment. Signals are often secondary metabolites that play an important role in competition, defense, attraction, and signaling. These molecules are recognized for having bioactive properties, but some of them are still largely underexplored and underexploited. This Special Issue focuses on studies that aim to improve knowledge on microalgal ecology (diversity and dynamics) in aquatic ecosystems, as well as on their capacity to produce bioactive compounds with potential biotechnological applications.

The value of ecological papers in this Special Issue derives from the increase in knowledge of phytoplankton diversity in specific environments (freshwater and brackish systems), but also from providing data on the effects of the increase in CO<sup>2</sup> concentrations in the era of global changes in a cosmopolitan marine microalgal species. Another interesting aspect concerns the biological remediation of microalgal species that are considered "harmful"due to their ability to produce toxins that negatively impact human health.

Investigations on microalgal bioactive compounds are a very promising area in full development. The growing interest is due to the wide range of applications including the food industry, agrochemicals, cosmetics, and pharmaceutical products. The studies presented in this Special Issue range from the biological activity of two new species to the production of protocol for the recovery, fractionation, and purification of high-value molecules (phycocyanin) and the effects of an herbicide (glyphosate) on a cyanobacterial species cultivated for the production of animal and human food additives.

> **Carmela Caroppo and Patrizia Pagliara** *Editors*
