Some of you may have heard me mention ‘the DR’ recently. This is short for the Dominican Republic (you’ll learn quickly that scientists love acronyms). I am leaving for this Caribbean nation on Sunday (in 2 days!) and have planned the majority of the field expedition in the last 10 days.
The trip is last minute because of a number of coincidences and lucky breaks, but the most important thing is that it is happening. So all of the last minute flight purchases, revisions of my espanol skills, and purchase of field tools are worth it! I am going with on of my co-advisors and his wife, and we will meet our Panamanian tech/assistant upon arrival. We’ll be there for a week, and spend most of the time near Lago Enriquillo– in the bottom left corner of the DR, near (but not on) the Haitian border. This is one of the hottest, dryest, places on the island of Hispaniola with some of the highest temperatures. For mild relief, we’re staying in a hotel by the beach in the town of Barahona. It was highly recommended because it has a pool and wine is available.
We are bringing things you might expect- hiking boots, shovels, zip loc bags to put samples in, sharpies to label everything; and things you may not expect- tweezers, paintbrushes, vegetable grilling baskets, and folding magnifying glasses.
So why, you may be wondering, are we going to this somewhat questionable place with a very questionable assortment of gear?
Lago Enriquillo is in the Enriquillo Valley, which has been naturally dammed from rainwater for hundreds of years. Ancient rivers once carved through this valley draining into the lake, and they exposed cross-sections of limestone. This limestone is in fact one of the best preserved Holocene (that’s the last 10,000 years) coral reefs in the world. Corals are intact and even in life position, along with algae and shells.
I study coral reefs, things that stress them out, and things that people might be able to do about it. The deeper you dig into history, the more you realize that people have been messing with the ocean for hundreds or even thousands of years. To better understand what a healthy or ‘pristine’ coral reef might look like, we need to do a little detective work. The fossil reef at Lago Enriquillo is a great opportunity to do this, because we can learn a great deal about the corals, algae, and bivalves that lived there 4000-9000 years ago. This straddles the time when the first hunter gatherer tribes reached the Caribbean- 6000 years ago. We are looking specifically for fish parts, most notably teeth. These are preserved in the sand that would have been in the reef lagoon thousands of years ago. We know from work of a past Scripps student, Loren McClenachan, that fish in the Florida Keys have changed dramatically in the past 100 years. But I want to go back even further than that, to before any humans were around.
So we will be digging out shovelfuls of sand from the lower parts of this fossil reef, running them through sieves (that’s what the vegetable grilling basket is for) to save material between about 1 centimeter and 0.1 millimeters in size. The finer stuff will be carefully packed and labeled to ship to San Diego. We’ll use the folding magnifying glasses, tweezers, and paintbrushes to pick through the coarser sand (2 millimeters to 1 centimeter) for anything that resembles a tooth, bone, or interesting fossil. Then those will also be carefully packed up to ship to our lab. So just in case you thought I’d be sipping sangria next to that pool on the coast- well, you may be right, but I’ll also be carefully going through our samples to try to reduce the volume that we need to bring home and grab anything that looks interesting. Although fish teeth are super cool, they are also pretty rare- a full gallon zip loc bag of sand only gives us a few hundred teeth. Back home in the lab, we will check out all of the sand under a microscope, pick out anything interesting, then soak it in weak acid for a week or two. The acid dissolves most of the material- reef sand is predominately made of calcium carbonate (that include sea urchin spines, coral skeletons, shells, algae). Teeth, however, are calcium phosphate, and they will be leftover when our dissolution is done. From counting and identifying ALL of the teeth in all of the sand that we collect, from the oldest to the youngest part of the reef, we can reconstruct the fish community of 1000s of years ago! I’ll update you on what we find as it happens 🙂