This book is based on study of Hooghly-Matla estuarine system along with its mangrove vegetation. The chapters in this book include general account of mangroves, detritus, sampling location of the present work. This book focuses on construction of conceptual model of nitrogen dynamics involved in the degradation of mangrove litter and its contribution as dissolved inorganic nitrogen to the adjacent estuary of Sagar island and how this dissolved inorganic nitrogen controls the grazing food chain of the Hooghly - Matla estuary. Moreover, this book has also covered the experimental and field studies and step by step model development followed by sensitivity analysis, calibration and validation. This book will help B.S, M.S students, research workers and people involved in ecosystem management around the globe