Mud, Mud, Glorious Mud...

Lake near Red Bays

One of the wonderful parts of this Bahamian adventure is the wallowing in various shallow lakes and ponds that have a blanket of algal mats to stand on which is overlaying the holey and sharp limestone.  These algal mats are not designed to take the weight of a human (in fact any macro-sized creature) and always give way underfoot, where you either encounter the treacherous bedrock or an aromatic hydrogen sulphide layer of mud (it smells worse than rotten eggs) and carbonate which is rather sinky.  However the lakes themselves are often very beautiful to look at.


Lakes in carbonate environments are a big deal in the oil research world at the moment, stemming from a large oil discovery Petrobras made a few years ago in an ancient lake environment.  The carbonate rocks formed in these lake environments are referred to as lacustrine and often are helped along by microbes living in the water and the mats.  Research into how these lacustrine carbonates form has been building momentum over the past decade and it is an area of interest for both Maurice, Fiona and Alex so in terms of BAPs projects its pretty high up the agenda.  The thing we are most interested in is how the life processes of the microbes (i.e. photosynthesis or put more simply, breathing) affect the water chemistry and in turn how that might affect the precipitation (formation) of the carbonate muds.

I left Fiona and Maurice to investigate the lakes on a previous day and they came back all positive with sediment cores, water samples from the lake and such from a small lake, on the road stretching to the west of the island (towards the settlement of Red Bays) past the wellfield area.  Then myself, Miles, Fiona and Mike went to have a further poke around and to place some logging sondes into the lakes (we eventually found two lakes of interest very close to each other) to monitor the temperature, specific electrical conductivity (which is a proxy for the amount of total dissolved solids in the water), dissolved oxygen (the amount of oxygen in the water), pH and turbidity (how cloudy the water is).  These sondes were placed overnight to give us an indicator of how the water chemistry changes when there was no sunlight and it gets cold (cold is a relative term here with below 25C being classed as cold!).

Miles taking the Manta into the lake

As well as placing these sondes, we collected sediment pore water, which are the waters that sit within the algal mats and the underlying sediments, and also placed some refresher sized pills of carbonate rock at different depths in the mud to allow for the microbes to have a new home to live on, so we can then bring them back to Bristol and study what types of microbes live in these lakes on the underlying rock.  TO understand the microbes in the lake water itself we also undertook some biological oxygen demand experiments (BODs).  These experiments allow us to measure how much oxygen the microbes use (by breathing) over a measured period of time.  This gives us an indicator of how active the microbes are in the water, high BOD means lots of breathing microscopic creatures loving our lake waters.

All this sounds very easy to do, just placing some equipment in, taking some waters out, measuring a few things. Sorted. Well if only life were that easy...A number of difficulties stood in our way, the first was the road scraping which separated us from the lake.  This almost was as deep as Fiona is tall, so a jolly little swim across a very smelly moat was in order.  

Mike and Miles wadding through the scrap back to dry land!

The second was once we were over the scrape then the "ground" under foot became less and less firm and more and more precarious.  Injuries and comical positions to be stuck in plagued us all at this point. The most notable were: Fiona bruised her knee "running" after an escaped water sampling bottle (all in the name of science!), Miles twisted his ankles on the rock and me getting stuck up to my hip in sediment and having to get a little assistance in removing myself from such a position (Fiona was more interested in how deep the sediment could get to and wanted to measure my leg rather than help me out!).  The third was battling against the rain to make sure we could measure the BOD correctly.  Why is it when you want rain, like at the beginning of the trip, its dry but as soon as you want dry calm weather you end up with a thunder storm.  Finally wedging the pills into place at the correct depths in the sediment involved a number of trip and a lot of thinking outside the box.

Pills placed inside a core of sediment which was then replaced into the lake

All in all a wondrous wallow in the mud, looking forward to counting those microbes once I am back in the UK!