Eureka!

That’s the subject line of an email I just received from Benja.

When the rest of Team Tanganyika left Tanzania back in August for (a much less exciting) life in the States, Benja stayed behind on a quest to collect data on the lake for an entire year.

And while the stories from the field are no longer mine, I still hope to share noteworthy updates from time to time (and live vicariously through my friend). 

This week something Very Noteworthy happened, and what follows is Benja’s epic tale regarding the critical piece of field gear that we love to hate: the thermistor chain.

It's been At Large since sometime in September, but luckily for Benja, the lost has been found.

Keep on keepin' on, Benja!

Hi All,

So here is the thermistor chain story…

The day was off to a very bad start. 

All of the gear was loaded up in the boat and Hagai, George and I launched out from TAFIRI at about 8:45 am to go install a new thermistor chain mooring. After motoring for about 200 meters, the engine started making a terrible noise and died. George started taking apart the engine as we drifted north across Kigoma bay. When we opened up the carburetor, we discovered what was wrong: where the carburetor should have been full of fuel, it was full of WATER. 

 Georgie's boat. It's a little more robust than our Zodiac

Uncertain about where the water came from, we decided to investigate the contents of the fuel tank. George unplugged the fuel line from the engine and pumped the contents of the fuel can into the lake. Sure enough, the liquid streaming from the fuel line was entirely clear. There was no rainbow sheen on the surface of the
lake like you would expect to see if it was fuel. To be sure, George stuck the fuel line in his mouth and gave a couple pumps. It tasted like water too. 

So, we started paddling back to TAFIRI, wondering about how the fuel tank could have come to be full of water. The best explanation that we could come up with was that the gas station where I filled the fuel tanks must have gotten rainwater in its storage compartment. Rainwater that subsequently got pumped into our tanks and sold as fuel. 

When we got back to TAFIRI, we started dumping all of the fuel I had recently purchased into buckets to see what was inside. Of the 80 L of fuel I had bought the week before, about 60 L was water. Determined to deploy the thermistor chain anyway, we decanted the actual fuel into one fuel tank and George worked on fixing the engine—taking it apart, emptying the water, replacing the spark plugs.

After taking the engine apart and putting it back together 3 times, the engine was fixed and we were on our way.

For the new thermistor chain, I planned to center the boat over the target deployment and toss the anchor/rope/buoys overboard and let it fall so that the anchor would have a better chance of embedding into the sediment. So we centered over the point where the 2012 thermistor chain had been deployed 5 months before and tossed the new thermistor chain overboard. After snorkeling from the surface, it appeared that the metal TAFIRI buoy was right at our target, 10 m below the surface. George and I loaded up our SCUBA gear and went down to add more buoys to the string to give it some extra floatation just in case one of the buoys were to fail.

We added a little good luck charm to last year's chain (yes, I mangled some US currency! On the 4th of July! I felt twinges of guilt...) hoping we'd be able to find it again.

But, when we got down to the top of the mooring, I arrived first and saw that the metal buoy had already failed. The pressure had caused the buoy to totally collapse, and a slow stream of bubbles was emanating out from one of the resulting cracks in the metal. Feeling quite dejected, I started thinking about what to do. 

This photo is from last year, but it illustrates the point. Even under the best conditions (i.e., no biofilm accumulation, no waves, etc.), that tiny white dot is all you can see from the boat at 10m. And THAT is what holds this Very Expensive Equipment!

Just then, I turned to my right, and there IT was, in all of its biofilm-covered glory, the thing I had spent days and days searching for, months lamenting its loss, not 10 meters away from where the new thermistor chain had been deployed. I turned back to George and he was already excitedly pointing at it. We swam toward each other and gave a big underwater hug. I’m sure he could see the grin on my face even with the regulator in my mouth.

It's hard to express emotion with a regulator in your mouth...

So, our plans changed a little bit. We swam to the old thermistor chain, attached a surface tracer buoy, detached the sonde and thermistors, and came to the surface with shouts of joy. We brought it all back to Aqualodge, downloaded the data, redeployed the instruments, and made it back to TAFIRI at sunset. In light of all that had happened that day, so many unanswered questions came up:

What do we do with the new mooring?
What do we do with the new thermistors that are, as we speak, on their way to Kigoma?
What do we do with the 60 L of water that we paid an exorbitant amount for as fuel?
HOW THE HELL DID WE MISS THE THERMISTOR CHAIN BEFORE?!?!

Nothing in the data suggests how we could have missed it. For example, according to the depth sensor, the chain did NOT spend a month down at the bottom of the lake only to be resurrected when we plunged the new mooring down on top of it. We did, however, catch another offshore spike in chl-a at the end of September that coincides with a chl-a spike near shore. More on data updates later, though.

I hope this news finds all of you happy and healthy back in the US! If you have any ideas on the questions above, let me know. I’ll probably come up with a plan early next week for the new mooring. 

Happy December!