Marcus is a long time North Queensland resident. He completed his University education at James Cook University, with a PhD in Marine Biology completed in 1995. He is currently a Professor in the College of Marine and Environmental Sciences at James Cook University. Marcus heads an active Estuary and Tidal Wetlands research group, and has published widely in the fields of estuary and wetlands ecosystem ecology, fish assemblages, nursery grounds and ecosystem supporting processes, and climate change. Current major research projects include impacts of oil palm on aquatic ecosystems, adaptation of estuaries to climate change, the role of mangroves as fish habitats in Pacific Islands, and livelihood benefits and fisheries ecology of an indigenous black bass sport fishery in Papua New Guinea.