Meiofauna is the major metazoan component of benthic ecosystem. Within the meiobenthos free living marine nematodes are an excellent taxon for use as an ecological indicator of benthic environments. The present book provides information about the ecology of marine nematode in the coastal and inshore waters of Arabian Sea, Pakistan. It includes the selected locations along the coastline of the Sindh and Balochistan. Certain environmental parameters were also taken into consideration. Assessment of marine nematode fauna in pre-monsoon, monsoon and post-monsoon seasons for three consecutive years showed variations in nematodes faunal composition. In trophic group composition epistrate feeder were found as the dominant group. The response of marine nematode community to heavy metal contamination and their co-relation analysis with mean nematode density showed significant negative co-relation with some environmental parameters and heavy metals in the samples. The marine nematode fauna associated in the mudflats of mangrove swamps were also investigated. This book gives the first report on the community structure of free living marine nematodes from northern Arabian Sea of Pakistan.