A.L. Knorr’s Elementals Series
I originally found this while researching other ocean and/or mermaid-like creatures when I stumbled across Born of Water. Eight books later and I’m still reading! On that note…
Here’s a series to sink your tail into if you enjoy reading about teenage girls saving the world (or at least Saltford, Canada) while discovering themselves and their power. There’s even some romance. Each girl cares about the world she is thrust into. The siren (mermaid) cleans part of the sea, the fire mage puts out fires, the Wise protects against electronic pollution and caring for the earth, the Euroklydon is of the air and worries about the continued existence of the planet (you’ll have to read it), and the Akuna Hanta is of the aether, saving the world from demons and showing us that love saves all.
Want to know more? You can find her books at: https://www.alknorrbooks.com/