Increased nitrogen loading to the Louisiana shelf has been postulated as a factor leading to eutrophication and the subsequent development of hypoxia west of the Mississippi River delta. Bioassays were performed with nutrient additions to surface waters collected from the Louisiana shelf to examine the potential for specific nutrient limitation. Experiments were conducted in March and September 1991, and May 1992. The results suggest that phosphate and silicate potentially limit phytoplankton growth during the winter-spring, particularly at low salinities. In late summer, in contrast, nitrogen limitation may be prominent at higher salinities.