Last month we completed a nine-day trek across the Yucatan Peninsula, for part II of an expedition that started back in 2016. Last time we were there, we sampled several mangrove populations along the coast, and one inland population along the San Pedro River. This time, we returned in search of mangroves deep within the heart of the Peninsula. We wanted to know what other freshwater bodies might have mangroves, a typically coastal marine plant.
Ben and I arrived in Merida, short one very crucial piece of luggage containing key pieces of equipment including our plant presses and chemical buffers. The delay set us back several hours, and so—having finally obtained the missing luggage—we were forced to race against the sun on a 6-hour drive to the San Pedro River to re-visit our original freshwater site and gather more information there. We pulled up to the river’s edge just as the sun was setting. Fortunately, we met a local guide who took us in her canoe to the nearby mangrove patch for us to document and collect what we needed. Day one was a narrow success.
Next, we headed deeper into Tabasco, to the upper reaches of the San Pedro River. With the help of another local guide, we set out to discover the distributional range of these freshwater mangroves, traveling upriver until we reached a stand of red mangroves just 12 kilometers from the Guatemalan border. Not only did we sample and document the mangroves, but we also surveyed the surrounding ecosystem to learn more about what types of plants and animals cohabitate in this freshwater space.
Our days of long drives not yet over, we headed north once again into Quintana Roo to the small town called Dziuche. We had heard of sightings of these marine intertidal plants inhabiting this stagnant freshwater lagoon located over 100 km from the nearest coastline. And yet, there was no concrete evidence that this was indeed the case. In fact, I had been here once before on our last trip, chasing red mangroves across the Chichankanab Lagoon. However, that time we did not get too far, because we were manually rowing a panga along a body of water that stretches over 15 kilometers in length.
This time, though, we came prepared with a small dingy equipped with an outboard engine to do a full survey. After several hours surveying the coastline, we lay to rest the question that had been nagging at us since this project began: is there Rhizophora in the Chichankanab Lagoon? Our conclusion was that there was, in fact, no red mangrove in this lagoon. Though this initially left us feeling empty-handed, what soon followed was excitement at the realization that this on-the-ground field research could finally dispel a myth that had been propagating through the scientific community for years.
From Dziuche we headed east to Tulum, the final site in this chasing mangroves saga. The first stop we made was to Laguna Kaan Luum. The easiest site to access by far, we walked along the lagoon’s pier documenting the mangrove stands that surrounded the clear blue waters. In contrast to Laguna Kaan Luum, our second stop, Laguna Unión, was much farther inland and, as far as we could tell, completely inaccessible by car. So, we headed into the forest on foot, and, two-and-a-half very tiresome and hot hours later, we arrived at the lagoon’s edge, overjoyed at the sight of a tall, dense forest of Rhizophora.
We chase mangroves to help us make discoveries and tell stories, such as this story of a Yucatan from long ago. Why are these mangroves in freshwater habitats? How and when did they arrive? What dynamics are at play in these inland ecosystems, as opposed to in the coastal mangroves we all know?
Field expeditions don’t just help us collect data for analysis. In this case, we went searching for things we were not sure were there. At the San Pedro River, we did find the mangroves we were looking for. In Chichankanab, on the other hand, we came up empty-handed. On-the-ground field work is an essential part of any research project. Confirming, and sometimes dispelling, expectations always contributes to a stronger understanding of the system being studied.
Now that we have all this information from the field, we can move onto lab analyses that will help us answer the many questions posed above. With the samples we collected, we can begin to map the genetic relatedness of these mangrove populations and start to understand when they became isolated from one another. And, as is often the case with research projects, from these results, many more new questions will likely arise.