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Microbes and Mermaids - Explore Bahamian Blue Holes

June 4 2018

Blue Holes are, sometimes very deep, vertical caves formed in KARST geological systems (eroded limestone). They are dominant feature of Andros Island in The Bahamas which has the highest density of these sink holes in the world. They were formed long ago when sea level was far lower than today as slightly acid rainfall percolated through and dissolved the limestone rock. Underground caverns were formed and in many cases the ceiling collapsed leaving a round opening to the surface. Sea level rose, rain fell and now there is a lens of freshwater filling the surface layers of many Blue Holes with sea water underlying that. The result – surface waters look much like quarries, but the deep layers are permanently ANOXIC (lacking molecular oxygen) and contain high concentrations of toxic hydrogen sulfide.
While this toxic chemical soup limits macroscopic life (e.g. fish) to the upper layers, microorganisms flourish under these harsh conditions. Using the most modern genetic techniques our goal is to identify these extremophile microbes throughout the depths of several Blue Holes – one inland with fresh water at the surface, one estuarine and one oceanic. Although many residents of Andros Island believe that Blue Holes are very dangerous places, we will explorer them using a remotely operated vehicle and then precisely collect water samples while scuba diving. We will of course be watchful for Mermaids, which are said to live in the Blue Holes and lounge along their rocky shores combing their hair, and for the infamous Lusca, the half octopus, half shark monsters believed to snatch swimmers and divers and even people walking too near the Blue Holes and carry them to their deaths in the depths.

June 4 2018


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Preparation Stage

Flying the Trident ROV

Just received my new Trident ROV this week. Have been "playing" with it on the floor checking out all the functions. I have never flown one of these before so it will be interesting to see how the learning curve goes. FYI regarding technical issues: the Cockpit software is running on my Samsung S6 phone - seems to be fine. It can be controlled by a Moga Hero Power game controller with the switch in the "B" position. All controls work fine. Controls three motors, forward, reverse, pitch and yaw – Also turns on/off the camera and lights. That is pretty much all it has. The underside has lots of points for attachments – but I don’t really have anything unless we attach the water quality probe there for cave work since at one site we cannot drop the probes straight down. Maybe we can fly the probe into the cave. The Cockpit display shows depth so we should be able to get Temp., dissolved oxygen, pH, salinity and redox potential - IF we can fly the probe into the cave and not get tangled.

The Cockpitsoftware is not designed for VR use as yet. BUT it turns out that I was able to clone the app and can run two versions of it side by side on my phone in landscape mode. Then with phone in the VR goggles you get a quasi 3D image and hopefully can fly in the virtual world. Only tried it with the apps search screen but it looks OK – not perfect but the VR goggles are cheap ones. Still in bright sun they should be a help since lack of screen visibility is a major a common complaint.

A quick update - I chatted with a very nice lady at the BEST Commission (Bahamas Environmental Science and Technology Commission) yesterday regarding my application to conduct research in The Bahamas. FYI for anyone considering research, even collecting water samples, in a country other than the US (and even in the US is many circumstances) - apply early and contact the permitting authority. In my case I sent the application to the wrong group in Nassau , and that has delayed review. On the good side this is all now electronic (who knew) so the permit will come in email as PDF.

One of our three sample sites is a blue hole known both as Church's or Captain Bill's. This is within the Blue Hole National Park system of the Bahamas. It is a very good thing that this Park was established (2002) to preserve these unique aquatic systems and surrounding coppice and pinelands. It does, however, require that I get a second permit from the Bahamas National Trust. There is a modest fee for processing each of these permit applications. URLs if anyone wants to see what these folks do.

Andros is only about 35 miles from Nassau, but is a whole world away in terms of development. Consequently we will need to be pretty much self sufficient in technical equipment. I have two highly experienced scuba divers with me (one a commercial diver) for underwater support and sample collection. It turns out that they are my adult sons, both of whom have sailed and dived Andros in the past.


WHY Explore Blue Holes in Andros Island, The Bahamas?
So why would anyone want to explore sink holes in remote Andros Island? It might surprise folks to know that these stratified, anoxic ecosystems came to our attention because they are like the Chesapeake Bay and the “dead-zone” in the Gulf of Mexico. Really – it was NOT just because we wanted to visit The Bahamas in January. The development of hypoxic (low oxygen) and anoxic (no oxygen) aquatic ecosystems is increasing globally. Knowing the microbes that both drive and survive this oxygen loss will be vital to understanding effects on larger ecosystems.

The thing is that the Chesapeake Bay is “salinity stratified” like the Andros Blue Holes. Basically the surface layer is a lot “fresher” (less salty) than the bottom water. The interface between the salty deep water and fresher upper layer is often quite thin. Salinity increases very rapidly with increasing depth.

Here is a depth profile of one of our research stations in the middle of the lower Potomac River – a tributary of the Chesapeake. These data were collected by college student is our Environmental Science BS degree program at George Mason U. As salinity increases with depth (red line), dissolved oxygen declines and goes to “zero” at about 7m (black line). Deep water anoxia happens every year in the Chesapeake, but only in summer. Because of lower temperatures and more wind mixing, there is some amount of oxygen in the deep water during fall, winter and spring.

On the other hand the Blue Holes in Andros are permanently salinity stratified and anoxic in the deep water. Being subtropical and relatively confined (a few hundred feet in diameter at most) they don’t have temperature effects and wind mixing. From a research point of view they are great exploration sites because we can revisit them over and over again to investigate newly discovered phenomena. With the advent of modern genetic and bioinformatics methods of identifying microbes, now is the opportune time to visit these sites.

Expedition Background

George Mason University has sent students and researchers to Andros Island in the past. Now, however, modern genetic techniques will allow unprecedented understanding of the "microbiomes" of these Blue Holes and give insight into how these microbes can survive and even thrive under such extreme conditions. Currently we are assembling the research and technical equipment for this expedition.

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