奥利维亚·尼格罗博士.D. at the Ala Wai Canal and Harbor.
HPU Assistant Professor of Biology 奥利维亚·尼格罗博士.D., recently authored a research paper in the journal American Society for Microbiology. The paper is entitled “ Variable freshwater influences on the abundance of 弧菌 本文描述 in a tropical urban estuary .” Nigro’s research addresses the abundance of the infectious bacterium V . 本文描述 in the Ala Wai Canal in Waikiki and how that bacterium is strongly influenced by the amount of rainfall in the surrounding areas.
“ V. 本文描述 occurs naturally in warm, brackish waters,尼格罗说. “ We expect to find the bacterium anywhere that temperatures are warm and freshwater and seawater mix in about equal proportions. When conditions are right, the Ala Wai Canal can be a great incubator for this bacterium.”
Authors Nigro and Grieg Steward, Ph.D., professor at the University of Hawai‘i School of Ocean and Earth Science and Technology, 第一次评估 弧菌 in 2006 when Oliver Johnson died from a V . 本文描述 infection after having cuts and scrapes exposed to Ala Wai Harbor water.
“ His exposure occurred after many days of heavy rainfall, 哪一个, 考虑到我们的结果, suggests this may have been an exacerbating factor,Steward说. “ At the time, we realized there was almost no data on the ecology of V . 本文描述 in the canal, or in Hawai‘i generally, 和非常, very little in tropical waters anywhere.”
Ala Wai Canal and Harbor during heavy rain.
After a quick pilot study in 2006 that showed the bacteria are present in high, but not unexpected numbers, the team geared up for a year-long study in 2008-2009 with better methods to understand the variability in abundance over a seasonal cycle.
At higher latitudes, the abundance of V. 本文描述 shows a very strong seasonal cycle—nearly disappearing in winter when temperatures are cold. In Hawai‘i, temperatures are warm year-round, so freshwater input becomes a more important control.
The researchers observed that rainfall has a variable effect depending on the amount of precipitation.
“Too little rainfall means much of the canal is saltier than optimum for V. 本文描述 growth, too much rainfall and the canal is fresher than the bacterium likes,尼格罗说. “We also found that, because of the flushing effect of intense rainfall, the highest abundance of V. 本文描述 shifted from within the canal out into the harbor.”
The researchers observed the highest canal-wide average abundances, among the highest recorded anywhere, during a time of modest rainfall, 中等盐度, and a moderate flushing of the canal.
他们指出, although rainfall is more frequent in winter on average,significant rainfall can also occur in summer, 所以在 V. 本文描述 can be a problem any time of year. This makes it challenging to predict precisely when and where there will be high concentrations of this pathogen. 然而, based on a few variables—rainfall and resulting salinity and flushing of the canal—the relative risk of exposure to this pathogen could be predicted as an average for the system.
With additional years of data to better understand how V. 本文描述 varies in space and time, it may be possible to provide real-time predictions of when and where the bacterium is likely to be at unusually high concentrations, 哪一个 is one component in assessing the risk of infection.
“尽管V. 本文描述 can cause serious or even lethal infections, it usually only becomes a problem for individuals with underlying medical issues,Steward说. “So people should not panic about incidental exposure to canal water. But it is wise to wash off with soap and water after exposure and one should avoid exposing open wounds to canal water, especially if one is immunocompromised.”
This project was supported by funding to UHMānoa from the National Oceanic and Atmospheric Administration through Hawaiʻi Sea Grant and from the National Science Foundation.
Images provided by 奥利维亚·尼格罗博士.D. and Grieg Steward, UHM, SOEST.
