We are currently looking upon the mountains of Capo Verde, looking even more magnificent behind the tropical haze. With islands on both port and starboard, we are sailing through the middle of the archipelago.  

We managed to carry out our mini chemistry session and filtered the boiled diet salts to separate the potassium chloride (KCl) from the sodium chloride. After then filtering the water out of the product and drying the salts I was left with pure crystals of KCl. To make my KCl solution I had to measure out 37.5g of KCl to 1 litre of distilled water. To do this I had to measure. With the sway of a boat, measuring scales become pretty useless. Fortunately, with a boat that is used to swaying comes problems that will have been encountered before and as a result come hand scales. This allowed me to counteract the rolling of the boat and measure out the very precise 37.5g of KCl. Yay! I have KCl solution! Now to try it out on the bioluminescent dinoflagellates.

Last night at 03:30, I conducted my first plankton trawl since departing from Tenerife. With much excitement, but equally some apprehension, I set up my science equipment with my freshly made KCl solution. The tropics either side of the equator are a hotspot for bioluminescence, this is because winds at the equator cause downwelling which displace water and cause upwelling of warm waters and nutrients to the tropics. You could tell. The net in the water was glowing with bioluminescence. After half an hour we pulled up the trawl… so much life!! I put my sample in a container so that we could better view the organisms.

Slightly side-tracked by the biodiversity in my sample we ended up checking out the species, including some organisms I am unsure of, such as a teeny tiny type of ctenophore, something I can only describe as a ghost-like eel with phosphorescent spots down its body, a lot of plankton and also, amazingly, a dragonfish (I think!) and a sardine with beautiful photophores down its ventral side. On the dinoflagellate front the KCl solution worked at first and then stopped working.

My conclusion is that the dinoflagellates must lose the capacity to bioluminesce perhaps through loss of luciferin available or perhaps death through too high a salinity in the water. I pulled up a fresh bucket of seawater from over the side to test but it was hard to tell whether the KCl was affecting the dinoflagellates due to the low concentration of organisms in there. Next sample I think I need to take the dinoflagellate sample immediately and simultaneously have the microscope prefocussed in the dark before adding the potassium chloride. Then I can take a long exposure photo and be able to count the organisms. 

Looking forward to the next trawl!!