They say this was a chronic condition in the area before the hurricanes, and that the resulting water quality in the city and in nearshore waters of the lake continues to be impacted by discharges from this contamination.
Study co-author Dr. Linda Amaral Zettler of the Woods Hole Marine Biological Laboratory, MBL, says that while floodwaters pumped from New Orleans back into Lake Ponchartrain following the hurricanes showed higher than normal levels of bacteria and pathogens, fecal indicator microbe and pathogen concentrations in the lake returned to pre-hurricane levels within two months.
But the sediments left behind in the flooded regions of the city appear to contain microbes commonly found in sewage treatment and remain a cause for concern because they may serve as a potential source of ongoing microbial exposure, she said.
'Our hope is that this data will provide some perspective not just on the immediate impact to the area, but the long term effects of this kind of natural disaster,' says Amaral Zettler. 'We certainly know a lot more now about the microbial diversity present in Pontchartrain than we did when we started the study.'
The study was a collaborative response of several institutions, including the Woods Hole Center for Oceans and Human Health, of which the MBL and Amaral Zettler are a part.
The researchers began collecting water and sediment samples from the interior canals and shoreline of New Orleans and the offshore waters of Lake Pontchartrain in October 2005 after the floodwaters had receded.
She said the Centers for Oceans and Human Health network enabled the team to mobilize quickly. 'Security was huge and the logistics of just getting around the city at that time were not trivial,' she says.
A collaborative grant from the National Science Foundation made it possible for the scientists to leverage their expertise and use their resources to contribute to a common goal. 'We really felt that as centers we were serving a role. This research would have been next to impossible if we would have had to go it alone - a true example of the whole being greater than the sum of its parts.'