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
In order to understand how Synechococcus in the estuarine environment (Chesapeake Bay) are phylogenetically related to other known marine Synechococcus, partial rbcL gene sequences from 25 strains of Synechococcus spp. isolated from estuarine, coastal and oceanic waters were sequenced. The rbcL gene phylogeny showed that Chesapeake Bay Synechococcus isolates together with other marine Synechococcus spp. formed a monophyletic group which belongs to the form IA RuBisCO. All the Chesapeake Bay Synechococcus were able to grow in a wide range of salinity (0 to 30 ‰), and most of them belong to the Marine Cluster B (MC-B). Interestingly, several phycoerythrin (PE)-containing Synechococcus isolated from the bay were clustered in the MC-B group, which had previously only contained the non-PE Synechococcus. A set of PCR primers was developed to specifically amplify the rbcL gene from natural marine Synechococcus populations. After screening 232 clones randomly selected from 5 clone libraries (built on 5 estuarine samples respectively), at least 7 different rbcL genotypes or the operational taxonomic units (OTUs) were identified. Despite the great genetic diversity among the OTU sequences, they were all clustered with 13 Chesapeake Bay isolates. The distribution frequency of these OTUs varied dramatically from the upper to lower bay. Our results suggest that the Chesapeake estuary provides an ideal environment for the MC-B type Synechococcus populations to thrive. Marine Synechococcus appear to adapt well to various ecological niches, and a clear boundary solely based on phenotypic features may not exist when more and more novel ecotypes and genotypes are unveiled with molecular tools. KEY WORDS: Synechococcus · Estuary · rbcL gene · Phylogeny · ClassificationResale or republication not permitted without written consent of the publisher Aquat Microb Ecol 36: 153-164, 2004 logical and chemical properties and DNA base ratios, Synechococcus spp. have been divided into 6 clusters: Cyanobacterium, Synechococcus, Cyanobium, Marine Clusters (MC) A, B, and C (Waterbury & Rippka 1989). It is now known that MC-A, MC-B, the Cyanobium cluster and the Prochlorococcus group formed a monophyletic group, distinct from freshwater Synechococcus and the MC-C cluster (Fuller et al. 2003). All strains in the MC-A cluster contain phycoerythrin (PE) as their major light-harvesting pigment. PE-containing Synechococcus strains can be distinguished by the presence or absence of phycourobilin (PUB) and the ratio of PUB to phycoerythrobilin (PEB) contained in the individual cells. All strains in MC-B and MC-C contain only phycocyanin as their major light harvesting pigment, but do not contain PE (Waterbury & Rippka 1989). Non-PE type is also called PC type in this study.The PE type Synechococcus is a major primary producer in pelagic oceans (Campbell et al. 1983, Campbell & Iturriaga 1988, Olson et al. 1990, and the phylogenetic relationship among PE isolates has been extensively examined (Wood & Townsend 1990, Urbach et al. 1992, 1998,...
Water quality was assessed for five subregions of Lake Oconee and Lake Sinclair in Georgia, USA. The areas were chosen for their levels of human impact, including: (i) suburban development >30 years old; (ii) modern suburban development; (iii) industry; (iv) agriculture; and (v) an area of low human activity. The measured temperature, pH, dissolved oxygen concentration and turbidity values were normal for oligotrophic lakes. Faecal pollution in the lakes was determined using the membrane filtration method (Method 1600) on mEI plates for enterococci. There was a positive correlation between turbidity and the number of faecal enterococci in the lakes. The faecal pollution level was higher for the old suburban and agricultural areas. Faecal pollution in the agricultural region of Lake Oconee exceeded EPA regulatory standards. The faecal pollution source was identified using polymerase chain reaction detection, with Bifidobacterium adolescentis being a marker of human faecal pollution, and bovine-associated Bacteroides (BoBac) as a marker of cattle faecal pollution. Human faecal pollution was detected in the agricultural, old suburban and industrial areas of the lakes. In contrast, bovine faecal pollution was detected only in the agricultural area of Lake Oconee. Measurements of chlorophyll-a and relative algal community abundance indicated the least-impacted and modern suburban areas had significantly lower numbers of primary producers, being dominated by diatoms.
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