Dr. Lewis' research has primarily focused on the trophic ecology of estuarine fish.
Estuaries are a primary nursery ground for many coastal fishes.
The value of these habitats is considered to be partly due to the abundance of food for young and developing fish. The high secondary productivity has been linked to the primary productivity of the marshes. In these systems the detrital pathway is considered to be vital in the conversion of vascular plant energy to higher consumers. The importance of amorphous detrital aggregates in the diet of the filter-feeding Atlantic menhaden has been examined. Further research is planned to examine mechanisms used by these fish and possibly other omnivorous macroconsumers to digest refractory compounds such as humic and fulvic acids.