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

We investigated the abundance, distribution, and virulence gene content of Vibrio cholerae, V. parahaemolyticus, and V. vulnificus in the waters of southern Lake Pontchartrain in Louisiana on four occasions from October 2005 to September 2006, using selective cultivation and molecular assays. The three targeted pathogenic vibrios were generally below the detection level in January 2006, when the water was cold (13°C), and most abundant in September 2006, when the lake water was warmest (30°C). The maximum values for these species were higher than reported previously for the lake by severalfold to orders of magnitude. The only variable consistently correlated with total vibrio abundance within a single sampling was distance from shore (P ‫؍‬ 0.000). Multiple linear regression of the entire data set revealed that distance from shore, temperature, and turbidity together explained 82.1% of the variability in total vibrio CFU. The log-transformed mean abundance of V. vulnificus CFU in the lake was significantly correlated with temperature (P ‫؍‬ 0.014), but not salinity (P ‫؍‬ 0.625). Virulence-associated genes of V. cholerae (ctx) and V. parahaemolyticus (trh and tdh) were not detected in any isolates of these species (n ‫؍‬ 128 and n ‫؍‬ 20, respectively). In contrast, 16S rRNA typing of V. vulnificus (n ‫؍‬ 298) revealed the presence of both environmental (type A) and clinical (type B) strains. The percentage of the B-type V. vulnificus was significantly higher in the lake in October 2005 (35.8% of the total) than at other sampling times (P < 0.004), consistent with the view that these strains represent distinct ecotypes.

Standards based on fecal indicator bacteria (FIB) have traditionally been used by the U.S. Environmental Protection Agency to determine when recreational waters are contaminated by fecal and sewage inputs. Studies in tropical and subtropical areas, however, have shown that these same standards cannot reliably be used in these environments to determine when waters are contaminated by sewage. This is because soil, sediments, water, and plants have been shown to be significant indigenous sources of FIB in tropical/subtropical climates. In these climates, alternative fecal indicators, such as Clostridium perfringens and F+RNA coliphages, may be more reliable markers of sewage contamination, because these organisms are generally found in low concentrations in the environment. In the State of Hawaii, monitoring data relating to FIB (fecal coliform, Escherichia coli, enterococci) and alternative indicator microorganisms (C. perfringens, F+RNA) in recreational waters has been obtained for the Island of Oahu, but similar data are lacking for other islands within the state. The major goal of this study was to monitor water samples obtained from the Nawiliwili watershed on the Island of Kauai for traditional FIB (fecal coliform and enterococci) as well as alternative fecal microbial indicators (C. perfringens, somatic coliphages, and F+RNA coliphages). Results for FIB concentrations on the Island of Kauai followed a similar trend as data obtained from the Island of Oahu. In addition, in areas like the Island of Kauai where cesspools are prevalent, monitoring for F+RNA and somatic coliphages may provide more reliable data in the detection of subsurface contamination of streams by cesspool waste, which can then lead to the pollution of coastal waters. Finally, genotyping of F+RNA phages obtained from the study sites provided additional evidence that human cesspool contamination was occurring within the Nawiliwili watershed.