Impacts of Hurricanes Katrina and Rita on the microbial landscape of the New Orleans area

Abstract

Floodwaters in New Orleans from Hurricanes Katrina and Rita were observed to contain high levels of fecal indicator bacteria and microbial pathogens, generating concern about long-term impacts of these floodwaters on the sediment and water quality of the New Orleans area and Lake Pontchartrain. We show here that fecal indicator microbe concentrations in offshore waters from Lake Pontchartrain returned to prehurricane concentrations within 2 months of the flooding induced by these hurricanes. Vibrio and Legionella species within the lake were more abundant in samples collected shortly after the floodwaters had receded compared with samples taken within the subsequent 3 months; no evidence of a long-term hurricane-induced algal bloom was observed. Giardia and Cryptosporidium were detected in canal waters. Elevated levels of fecal indicator bacteria observed in sediment could not be solely attributed to impacts from floodwaters, as both flooded and nonflooded areas exhibited elevated levels of fecal indicator bacteria. Evidence from measurements of Bifidobacterium and bacterial diversity analysis suggest that the fecal indicator bacteria observed in the sediment were from human fecal sources. Epidemiologic studies are highly recommended to evaluate the human health effects of the sediments deposited by the floodwaters. Preliminary investigations in mid-September 2005 documented high levels of microbial and toxicant contamination in the NO floodwaters (1-3). Reports of mean total coliform and total Escherichia coli levels as high as 8 ϫ 10 8 CFU per 100 ml and 3 ϫ 10 7 CFU per 100 ml, respectively (1) indicated the presence of sewage contamination and associated sewage-borne pathogens. Elevated concentrations of fecal coliforms have previously been observed in floodwaters of the NO region, but the 2005 event was characterized by an unusually large volume and long duration of human exposure (4). The most contaminated area tested near the Superdome also contained high levels of nonsewage pathogens, with an estimated Aeromonas spp. concentration of 1.7 ϫ 10 8 per 100 ml (1). Concentrations of Vibrio spp. were not measured, but the temperature and salinity of the floodwaters would have been favorable for their growth, and the number of Vibrio infections reported in the month following Hurricane Katrina was higher than normal (5).As shown in the satellite floodwater image, Ϸ34 billion liters of water covered NO as of August 30, 2005, with floodwater depths in several areas in excess of 3 m (Fig. 1). As these floodwaters were pumped back into LP, sediments were deposited throughout the flooded regions of the city (including the interior of homes). To a large extent, these sediments, now dried, remain even after 1 year

Diverse, rare microbial taxa responded to the Deepwater Horizon deep-sea hydrocarbon plume

“…DNA extraction was performed from the entire sterivex filter (see Sample collection section) using the Gentra Puregene Kit (Qiagen, Valencia, CA, USA) as described previously (Sinigalliano et al, 2007), in combination with a lytic enzyme solution (Qiagen; Zettler, 2013). DNA extracts were stored at − 80°C until PCR amplification.…”

Microbial community structure across the tree of life in the extreme Río Tinto

“…Polymerase chain reaction (PCR) amplification, cloning and sequencing Genomic DNA from each of the 27 samples was PCR amplified in triplicate using universal primers designed to target all three domains of life (bacteria, archaea and eukarya; Sinigalliano et al, 2007). This region spans E. coli positions 517-1391 corresponding to hypervariable regions V4-V8.…”

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

“…Clearly, the microbial burden of the floodwaters was very large. In contrast, after the floods had receded, Sinigalliano et al (5) rarely found Lake Pontchartrain water to exceed the aforementioned Environmental Protection Agency exposure level, and then only at stations near the shoreline. Water samples from the canals, however, frequently exceeded the mark.…”

“…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.…”

“…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.…”