Preface: A themed section honoring the legacy of Dr. Brij Gopal.

This document is a preface to a themed section in the journal Hydrobiologia, dedicated to honoring the legacy of Dr. Brij Gopal. Dr. Gopal was a respected scientist and member of the Hydrobiologia Advisory Board, known for his work in river, lake, and wetland ecology. He made significant contributions to understanding biodiversity, ecosystem functioning, water quality, and natural resources conservation. Dr. Gopal also mentored numerous students and received several national and international awards for his work. The papers featured in this themed section explore the ecological aspects of the ecosystems that Dr. Gopal studied, including wetlands, streams, mangroves, and reservoirs around the world. [Extracted from the article]