This Themed Section serves as a tribute to the late Dr. Brij Gopal, who passed away on January 4, 2021. Beyond being a delightful person, Dr. Gopal played an important role as an active member of the Hydrobiologia Advisory Board. It was an honor for us to organize a Themed Section in our journal dedicated to his memory.

Dr. Gopal enjoyed a successful career, as evidenced by Chauhan (2021) and Bandyopadhyay (2022). He devoted his scientific endeavors to understanding various facets of river, lake, and wetland ecology, spanning biodiversity description, ecosystem functioning, water quality, economic valuation, and natural resources conservation. His commitment extended beyond the mere publication of scientific papers and books; he actively engaged in applied aspects related to policies and laws governing water quality and biodiversity management. Additionally, Dr. Gopal left a legacy as a mentor to numerous students at various academic levels. He co-organized and hosted the first INTECOL International Wetlands Conference in New Delhi in 1980; a tradition that continues to the present.

In recognition of his significant contributions to science and the conservation of water resources and biodiversity, Dr. Gopal received several national and international awards, including the very first recipient of the Young Scientist Medal of the Indian National Science Academy in 1974 and distinguished Naumann–Thienemann Medal from the International Society of Limnology in 2004. He received the International Fellow Award of the Society of Wetland Scientists in 1997.

We extend our gratitude to the authors who promptly agreed to contribute to this Themed Section, as well as to their reviewers. The papers featured in this section honor Dr. Gopal inheritance and delve into the ecological aspects of the ecosystems that he explored throughout his lifetime: wetlands, streams, mangroves, and reservoirs located in different parts of the world.

Despite originating from a region with limited historical emphasis on science and limnology, Dr. Gopal serves as an inspiration for a new generation of scientists and environmental managers. Their role is more crucial than ever on a planet that is undergoing unprecedented changes.