Diatoms are important primary producers that are widespread in marine ecosystems. Their high species richness and diversity, and strong relationships to water quality, make them ideal organisms for bioassessments of ecosystems (Desrosiers et al. 2013). However, before these organisms can be used in bioassessments, their taxonomy must be better understood. The great number of individual diatom species increases the likelihood that a few of them will exhibit changes in relative abundance in response to changes in particular environmental characteristics. Salinity is one of the most infl uential variables affecting the spatial distribution of diatoms, with many taxa limited to either marine, brackish, or freshwater habitats (Frankovich et al. 2006; Saunders 2011; Haynes et al. 2011; Wachnicka et al. 2010; 2011). Nutrient availability has also been shown to infl uence the composition and abundance of diatom assemblages 1 Department of Biological Sciences, Marine Science Program and Southeast Environmental Research Center. Florida Bay Interagency Science Center, 98630 Overseas Highway, Key Largo, Florida 33037.