Bocas del Toro

Evidence of a nighttime visitor

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Scanning electron microscope image of a denticle extracted from the fossil reef in Bocas del Toro, Panama. 283x magnification.

Here is a denticle that I was not expecting to find. It belongs to a shark that I only on second thought included in my denticle reference collection, one that ought not belong on a coral reef. This appears to be the denticle of a crocodile shark (Pseudocarcharias kamoharai). While denticles can normally only be identified at the family level, this one fails to resemble any other denticle in my reference collection… except one. It looks almost identical to those that I isolated from the skin of a verified crocodile shark at the Smithsonian National Museum of Natural History (image below), except that it is a little smaller and much more weathered.

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Scanning electron microscope image of a denticle isolated from the body of a crocodile shark for inclusion in our reference collection. 185x magnification.

Not only are crocodile sharks unassociated with coral reefs – in fact they generally only ascend from the depths at night to feed – but this shark has not been documented in the region in which this denticle was found. What’s more amazing is that this denticle is not even modern. It was extracted from our  6,600-year-old fossil reef!

While you may have never heard of a crocodile shark, they are listed as ‘Near Threatened’ on the the International Union for Conservation of Nature (IUCN) Red List. We obviously need to learn more about this species of shark in order to better protect it.

Our finding suggests that crocodile sharks did occasionally venture onto the lagoonal reefs of Bocas del Toro, Panama in the past (and perhaps even in the present day as well). More importantly, to me, this denticle epitomizes the beauty of the technique. Extracting and analyzing dermal denticle assemblages can reveal the rare, cryptic, or ephemeral elasmobranch visitors on reefs, an otherwise very challenging task to accomplish.

Crocodile shark. Source: PIRO-NOAA Observer Program. Wikimedia commons.

 

Time to ring in the New Year with some coral measurements

Sometimes we do a little more than just dig in the sand. Over the New Year, Mauro and I taught the coral reef ecology unit of an undergraduate field course from the University of Wisconsin–Green Bay and St. Norbert College at the STRI field station in Bocas del Toro, Panama. While we spent a portion of our time in the lab discussing the importance of the area and looking at creatures under microscopes, we also brought the class snorkeling on the reefs with us to do some field work and explore. For some of the students, this was their first time snorkeling and seeing a coral reef in person. For me, that moment was life-changing, so I’m delighted to be able to share this magic with them. We visited a diversity of reefs during the trip, some of which were clearly healthier than others, and we discussed the differences between them and the potential underlying anthropogenic and natural drivers. For example, instead of merely reading that runoff and eutrophication are harmful for coral reefs, the students were able to glimpse algae-covered corals off the coast of the Changuinola River floodplain, the site of extensive banana plantations.

The students also got some hands-on experience doing field work. With the help of the class, we’re investigating long-term bioerosion rates on branching corals, specifically staghorn (Acropora cervicornis) and finger (Porites sp.) corals, in Almirante Bay. This study will improve our understanding of the carbonate budget on reefs in the region and, in particular, which way the seesaw between reef accretion and dissolution is tilting. This question pertains directly to the future of reefs in Bocas del Toro as well as how resilient they may be to future perturbations such as storms. Furthermore, it helps us key into one of the processes contributing to the reef substrate, which is where our lab collects bulk samples and sediment cores to reconstruct historical reef communities. Understanding whether the reef is actively contributing to this substrate through coral growth and reef accretion or whether it is stagnant or even shrinking can provide context for interpreting patterns of microfossil abundance. This study may also shed light on dates we computed for corals extracted from cores at these sites, which suggest that some of the dead corals lying on the surface are far from modern.

We started this study in December 2015 by collecting, measuring, and redeploying recently-dead pieces of coral on mesh plots. We successfully relocated the plots this past December and took our first annual measurements. Some bioeroders were even see in action on the reef! Interesting trends are already starting to emerge in the data. One of the students will be conducting an independent study to try to unravel some of these patterns, so stay tuned for her findings.

The next installment of shark denticle photos is here!

Over the next several weeks, I’ll be showcasing scanning electron microscope (SEM) images of some of the denticles that we extracted from the modern and ~7,000-year-old fossil coral reefs in Bocas del Toro, Panama. While the SEM images that I released previously were from known species of sharks in my reference collection, the denticles that I’m about to show you came from sediment samples we collected and processed. Our job now is to become sleuths and figure out what types of shark shed them.

Like a portrait, these denticles can paint a picture of the sharks they came from. They are the bards of the sharks of lore, lost in the sands of time… Ok, that’s one massive cliché (and I might be a bit too obsessed with denticles), but you get the point. Denticle morphology can provide us with useful insight into the historical ecology of sharks. For example, a denticle’s thickness can reveal whether its owner lived in the crevices of a reef or up in the water column. Its ridges can tell us whether or not it was a fast swimmer, speed which it may have used to catch nimble prey or swim long distances.

Some denticles are better storytellers than others, however, so we need to figure out who is who. This is one of the more unusual denticles that I’ve found so far. What type of shark do you think it may have come from? Stay tuned for my interpretation.

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Coring Caribbean reefs

Alongside our work examining the relative abundances of coral and mollusc skeletons, shark dermal denticles, sponge spicules and fish otoliths in large tracts of exposed mid-Holocene reefs, we have also been collaborating with Drs. Katie Cramer and Richard Norris (Scripps) to explore sequential changes in Caribbean reef ecosystems by extracting reef matrix cores in Belize and Bocas del Toro, Panama. We collected more than twenty 6m long aluminium cores from several lagoonal fringing reefs that capture reef ecosystem conditions going back the last couple of thousand years.

See more about the approach in this little video

Nicte-Ha’s farewell!

Earlier this year, the coral project was set. The research question was clear, the samples – the key to the question – were at hand, and I was making good progress. But the coral team had only one member: me. This was not great because I love working in teams and to learn new stuff. How best to learn if not by teaching?

Potential interns had shown interest in working in the lab. Not always, however, this works well for the intern or researchers. It is hard to find a good match. Then, a young woman emailed Aaron. Shortly after, she was standing in front of us. “Gosh! Nicte-Ha is very determined”, I initially thought. And she was.

On day one, Nicte-Ha said that she aimed to find a research job in Bocas del Toro. We were sitting hundreds of kilometers from Bocas, but for Nicte-Ha, we were pretty close. A few hours after she analyzed the last sample in our lab, she headed off to Bocas del Toro.

What do you think happened between day one and the last sample she analyzed? Success! That is what determined people consistently get. Just to name a few of her achievements, Nicte-Ha learned fast and taught others, analyzed hundreds of kilograms of coral samples, developed and presented a poster at a conference, and was actively engaged in the daily life and discussions of our scientific community. More than anything, she got a special place in everyone’s heart.

Thank you, Nicte-Ha. Today we see you leave, moving in the direction you chose. We are happy and proud.

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Nicte-Ha Muñoz presents a poster in APANAC.

Great news from the coral team!

The coral team has great news to share: one reef from Bocas del Toro may be a bright spot! This blog explains what a bright spot is, why it is important and where we may have found one.

Coral reefs are declining worldwide but not all of them are in bad shape. Bright spots are, among coral reefs, those reefs that are in better condition than expected given the environmental and socio-economic conditions they are exposed to (Cinner et al. 2016). If we can learn why bright spots are different, we may be able to improve degraded reefs. But first we need to identify bright spots! And we may have found one in Bocas del Toro, Panama.

To do this, we became time-travelers! We compared (fossil) reef corals that lived in Bocas del Toro around 7 000 years ago (figure 1a) with (subrecent) reefs corals that have lived here over the past few decades (figure 1b). We measured the amount and type of reef corals both in fossil and subrecent reefs. From this data we are learning how reefs changed since substantial human impact began.

Our preliminary results show that one reef from Bocas del Toro, Punta Caracol, is a potential bright spot. Compared to other subrecent reefs, Punta Caracol is exposed to similar environmental conditions and human pressures but it seems substantially healthier. In fact, it is almost identical to the pristine reefs that lived in the region 7 000 years ago.

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Figure 1. When fossil (a) and modern (b) reefs from Bocas del Toro are compared, Punta Caracol is outstanding, likely a bright spot. It is healthier than other subrecent reefs and similar to pristine reefs that lived in Bocas 7 000 years ago.

Our next step is to refine this exciting finding. We plan to precisely describe how Punta Caracol is special. For example,

  • What type of corals drive the difference between Punta Caracol and other subrecent reefs?
  • What are the key similarities between Punta Caracol and the pristine reefs that lived in Bocas del Toro 7 000 years ago?

We will let you know what we find out!

It’s Melisa’s farewell

Today we say farewell to Melisa! Because she has done great and has big plans ahead, we want to celebrate.

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Melisa never gets stuck (except this one time)!

During her three-month internship, Melisa was outstandingly productive. For example, she (a) identified over a hundred kilograms of tiny coral fragments, (b) planned a fieldtrip, (c) reviewed literature, (d) developed a guide and a reference collection to identify coral skeletons, (e) wrote an abstract and produced a conference poster, (f) presented interesting topics at multiple lab meetings, (g) attended to multiple scientific seminars and (h) organized the research collection of the coral team. And most importantly, Melisa connected personally with everyone she met. She is easy going, kind, and respectful.

But the semester starts soon so she has to go back to college. For her farewell, we gave Melisa a little present and took her out to lunch. The restaurant we chose was Napoli’s Restaurant and Pizzeria, a place that has hosted the special occasions of the O’Dea lab and its scientific family, including the legendary Tony Coats and Jeremy Jackson, over decades.

The coral team, the O’Dea lab and many others at the Smithsonian Tropical Research Institute will remember and miss her a lot. Because she is smart, positive and hard working, Melisa will never hit a roof. So I am confident this is only the beginning of something even bigger and better.

Melisa, we wish you the best because you deserve it!