Wetlands host complex biotic communities, and it is expected that the size and diversity of these communities are directly related to the quality and quantity of available resources. Wetlands are essential for maintaining an ecological balance through elemental cycling, and are sensitive to anthropogenic impacts. In this paper we review the inter-relationships between and within carbon, nitrogen, phosphorus, sulfur cycles as influenced by both external and internal forcing functions. Both biotic and abiotic processes regulating these cycles will be discussed. Case examples of a freshwater wetland and a saltwater marsh will be used. The review will identify critical research needs for better understanding of elemental cycles in wetlands as related to water quality, carbon sequestration, and global climate change.