Scientific Results from The Black Hole, South Andros

Bacteria
[click to enlarge]

"The unfathomed depths of the kilometre-wide Black Hole that pierce the flat Bahamian landscape", a huge underwater cavern still unexplored were the words that the late Rob Palmer used to describe this landlocked feature.

"The Black Hole" of South Andros. However in January of 1998 and again in June 2000, the mystery of the Black Hole was finally revealed.

It was assumed for many years that the colour of the entrances to the underwater networks of caves in the Bahamas was an indicator of its depths. However, following the second visit to the Black Hole, this was proven to be wrong. The reason that the Black Hole is black is because located at 17.8 metres is a one metre dense layer of purple bacteria. Under the one metre layer the water is again crystal clear. It is this bacterial layer which gives this particular entrance its colour.

Stephanie slipping through the bacterial layer

Sample of the purple bacteria have been cultured by scientific collaborators in the UK and thus far two pure cultures have been revealed and discovered to be sulphate reducers. That means that they use sulphate to drive their metabolic activities. Sulphate reducers generally are responsible for generating hydrogen sulphide, a substance that we recognize by its rotten egg smell.

In February DNA analysis will be performed on these bacteria to determine if new species have been found. Results will be posted.

View Geochemistry Graphs

Prior to entering the Black Hole, it needed to be determined how dangerous the water conditions were. From the first visit to the Black Hole, this black layer was discovered to be very hot and very toxic based on the smell and taste of hydrogen sulphide. On the first visit to the Black Hole, I did not have the equipment nor did I have a guide line to pass through this layer. Based on Rob's description, I did not think that I needed the extra equipment. On the second trip in, I had a hydrolab, an instrument which can measure pH, temperature, dissolved oxygen and salinity. The measurement in which I was most interested was the dissolved oxygen. If there is no oxygen it generally means that the conditions are ripe for very high levels of hydrogen sulphide, a very toxic substrate, which when concentrations are high enough can cause death.

Not wanting to lose any expedition team members or my own life, I lowered the hydrolab through the entire water column to make the earlier mentions conditions. It turns out that the Black Hole is only 48 metres deep and that conditions were boarder-line for diving. Once through the purple layer and a bit, the floor, or what was though to be the floor appeared. It turned out the the floor is covered in an unknown thickness of microbial mats. The landscape was very Martian looking.