Petroleum production platforms as sites for the expansion of ciguatera in the northwestern Gulf of Mexico

Ciguatera is a common human disease of tropical, coral reef ecosystems acquired by consuming finfish-containing ciguatoxins (CTX). There are few records of this disease in the northwestern Gulf of Mexico, a region characterized by soft muddy bottoms that are considered poor habitat for the CTX source dinoflagellate Gambierdiscus toxicus. However, the approximately 4000 petroleum production platforms and hundreds of state-sponsored artificial reefs located in the Gulf of Mexico provide hard substrate and often support coral and other components of the tropical benthos. In addition to their role in their resource extraction, these oil production platforms are also popular sites for recreational fishing and sport diving. We examined these platforms as potential substrate for G. toxicus and report a first record of this species in the NW Gulf of Mexico. All the platforms (n = 6) examined harbored the dinoflagellate as an epiphyte on the fouling community, with three finds of G. toxicus associated with the pelagic macroalga Sargassum. Only minor toxicity (<0.15 ppb) was noted in two of 20 great barracuda (Sphyraena barracuda) examined. Tagging data suggest trans-Gulf migrations by barracuda are common; thus, we cannot determine if the toxicity was acquired locally or transported in migrating fish.These platforms are a clear example of how human activity has altered the environment in a way that allows expansion of a HAB population. The rapid increase in production platforms since 1942 has provided novel substrate in a sandy/muddy bottom environment generally considered to be poor habitat for these benthic dinoflagellates. These platforms create a unique habitat in the upper euphotic zone and serve as intersection points for fishermen and potentially toxic fish. Many Gulf of Mexico states have active programs to turn non-producing platforms into artificial reefs. Our results suggest that the use of these platforms as fisheries enhancement structures could have unintended consequences for human health, particularly if projected rising sea-surface temperatures over the next century alter benthic distributions and fish migration patterns. These concerns also extend to mariculture operations around oil production rigs or offshore wind farms, both of which would also add substrate for epibenthic microalgae.