Once a subterranean oceanic cave fed by the Atlantic Ocean, Devil's Hole eventually collapsed and is now a large water-filled sinkhole. Prior to its collapse, Devil's Hole was one of the island's most popular (and oldest!) tourist attractions, serving as a natural aquarium and offering up close views of Bermuda's indigenous marine life. Since the 1950s scientists from around the world have studied a variety of natural marine processes and organisms in Devil's Hole, including carbonate sedimentation, the ecology of boring sponges, and nutrient flux of sediments. Today, Devil’s Hole forms a natural laboratory that scientists are using to understand how marine organisms and sediments are responding to changing physical and chemical seawater conditions.
Each year Devil's Hole undergoes reliable transitions: there is a period of summer stratification that causes lower waters to be seasonally hypoxic (low in oxygen), followed by an overturn during the winter months during which the entire water column returns to typical oxygenated waters. As a result, observations of bacterioplankton in Devil's Hole can demonstrate how the community changes in response to low pH and O2 and increased levels of pCO2. Researchers are particularly interested in bacterioplankton and associated microbial processes because they are believed to be of increased importance as ocean surface warming creates more numerous and more frequent oxygen minimum zones.
Chemical and Bacterioplankton Changes
In 2008, under the guidance of Rachel Parsons and Andreas Andersson, two NSF-funded Research Experience for Undergraduate (REU) students began work on the Devil's Hole project, with one student looking at bacterioplankton aspects (identification of bacterioplankton species and community shifts) and the other investigating changes in water chemistry. Further information on this study can be found in this summary document.
Further Devil’s Hole Research in 2009
One of the REU students returned to BIOS in 2009 as an intern with the Oceanic Microbial Observatory. During this time, she used new fluorescent in-situ hybridization (FISH) probes to identify bacterioplankton in the surface waters, as well as the low oxygen layer at 24m depth. Further studies, including nutrient analysis, were conducted and funded by Craig Carlson at UCSB to confirm these initial findings. Learn more about 2009 results here.
Completing the Study in 2011
In 2011, a Fall Semester student finished the project by using Catalyzed Reporter Deposition FISH (CARD-FISH) to determine the contribution of archaea to Devil’s Hole during periods of low oxygenated bottom waters and following convective mixing of the entire water column.
The results of this 3-year study have been submitted for publication and accepted with minor revisions by Environmental Microbiology. Parsons, RJ, Nelson, CE, Demnan, CC, Andersson, AJ, Kledzik, AL, Vergin, K, McNally, SP, Treusch, AH, Carlson, CA, and Giovannon, SJ. (2014) “Marine bacterioplankton community turnover within seasonally hypoxic waters of a sub-tropical sound: Devil¹s Hole, Bermuda.” Environmental Microbiology (in press). You can view the abstract and purchase the full paper online here.
Additional research done at Devil's Hole includes this paper: Andersson, AJ, Bates NR, and Mackenzie, FT. (2007) "Dissolution of Carbonate Sediments Under Rising pCO2 and Ocean Acidification: Observations from Devil's Hole, Bermuda." Aquatic Geochemistry 13(3): 237-264.