Après le déluge: Microbial landscape of New Orleans after the hurricanes

Abstract

Now would I give a thousand furlongs of sea for an acre of barren ground. William Shakespeare, The Tempest When storms of hurricane force unleash their power on natural systems, they can reset successional sequences and even change the structure of biological communities (e.g., refs. 1–3). Should that same power descend on a center of human population, the results can be deadly catastrophic. A recent and unforgettable example is the one-two punch delivered to New Orleans in August and September 2005 by hurricanes Katrina and Rita. Failure of levees within the city and the resultant flooding by waters from Lake Pontchartrain set the stage for a collapse of social norms and governmental order. Images of New Orleans' human misery after the storms have become iconic. After landfall of Hurricane Katrina, much was conjectured about potential public health repercussions of the storm (4). The arrival of Hurricane Rita 26 days afterward served only to compound the situation and increase such speculation. Fortunately, there were no large-scale outbreaks of serious communicable disease. There has been, however, increasing documentation of the storms' effects on the city's environment, especially in those low-lying areas that were under as much as 3 m of water. What are the concerns associated with the sediment, toxic chemicals, metals, and microbes mobilized by the hurricanes? In a recent issue of PNAS, Sinigalliano et al. (5) consider the poststorm “microbial landscape” of New Orleans and environs. They show that Lake Pontchartrain's microbial environment returned to prestorm (but not pristine) conditions 2 months after the hurricanes. Furthermore, they argue persuasively that the lake was not the source of fecal contamination in floodwater sediments; instead, the city's deficient sanitary infrastructure was responsible. The study represents the efforts and expertise of investigators distributed among eight academic institutions and three National Science Foundation/National Institute of Environmental Health Sciences national centers. Sampling began and was most intensive during the 2 months after New Orleans was “dewatered,” i.e., when floodwaters were pumped back into Lake Pontchartrain. Results cover the time span from October 2005 to December 2006. Thus, Sinigalliano et al. (5) did not sample floodwaters but instead tested water samples from Lake Pontchartrain and canals draining from the city into the lake. In addition, their article evaluates sediments deposited in private homes and those collected from sites around the city.