Great question. However, for a spectral library to be build we will need the spectral characteristics of different mangrove species around the world, and to my knowledge these are yet to be fully defined. I do hope that someone is already working on this.

Narayanan rm

this is a great question, and a very topical issue,

I would like to have access to such a database myself

recently I saw the initial assumptions for the project, which was to create such a base for forests in Europe, but this is just the beginning, and unfortunately not what you are looking for

Good luck!