The upper northwestern Gulf basin is characterized by a relatively shallow but well-developed continental shelf with an extensive system of mid-and outer shelf hard banks formed on unique tectonically created salt diapirs of varying origin and composition. Observations done by our laboratory while participating in monitoring cruises to the National Marine Sanctuaries of the E and W Banks of the Flower Gardens (TX), Stetson Banks (TX), Sonnier Banks (LA) and dredging cruises off Louisiana reveal a surprisingly different floristic composition among the sites. Several range extensions, new macroalgal records for the Gulf of Mexico, and new species imply a much more complex algal community than previously documented. Our ongoing project includes the development of a modern taxonomic, phylogenetic and morphological database essential to informed management for preservation of biological diversity. It also provides a framework of seasonal algal composition against which long-term trends and anomalies in algal distribution and health of the Gulf of Mexico can be assessed at future dates.

Key words: floristics, Gulf of Mexico, Louisiana, marine sanctuary, seaweeds, Texas