Author: seanmattson

Mission accomplished … phase one, at least

Two weeks after crisscrossing the Dominican Republic from one compass extreme to another, the Baseline Caribbean team delivered their collection of reef fossils and modern reef sediments — all 800kg of it — to Santo Domingo’s Las Américas International Airport for shipping to Panama.

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Erin and Félix carefully pack the crates at the Santo Domingo airport.

In all, the expedition logged about 1,500km on the road, three full field days exploring fossil reefs, 14 dives on modern reefs, two birthdays (Aaron had his b-day, too) — and only a couple of upset tummies from the mystery meat dishes and/or the choppy seas.

The 18 crates of samples include 65 large bulk bags and 130 small ones. “There are a lot of steps you have to go through to get them shipped,” said Erin. “Filling out papers with customs, checking the permits, waiting around, sending the samples through customs where some get randomly opened, and then packing them up nicely.”

If all goes as planned, the samples should arrive for analysis at the lab of STRI staff scientists Aaron O’Dea in the next few days. Then the “real” work begins — finding and identifying all the corals, dermal denticles and other traces of past and modern Caribbean reef in those bulk bags will take many months. But let’s not remind the team of that until everyone gets a much deserved rest after two nonstop weeks on the road!

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Phase two: 800 kilograms of lab work

 

Farewell, Samaná

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Samaná under the waves

After three days of sampling in Samaná Bay, it’s time to pack up and head back to Santo Domingo with another 90 sediment samples. It was neat to see the differences between the fossil reefs of the Enriquillo Valley and their modern counterparts in Samaná, a bay with a similar form and comparable sheltered fringing reef environment.

While one of our study sites was home to a large thicket of living staghorn coral (Acropora cervicornis), most of the reefs we visited were devoid of this IUCN critically endangered species. All that remained were eroded fragments of their branches covered in algae and encrusting organisms. Instead, algae, sponges, the occasional coral head, soft coral, or gorgonian (sea fan) populated the sandy bottom. Starfish and urchins patrolled the substrate, but we saw few fish.

In contrast, fish were much more abundant at the reef with healthy staghorn coral. We spotted small parrotfish, wrasses, surgeonfish, lizardfish, and territorial damselfish tending their algal gardens amongst the branches of the staghorn coral. We even saw an octopus crawling along a crevice between coral heads. In this shallow habitat, we collected sediment between the living staghorn colonies or in areas containing its rubble. While we encountered large waves and wind during our visit, the bay is normally more quiet. As such, we found the sediment to be fine and silty — exactly what we were looking for.

Deeper on the reefs, the corals were more densely distributed than I had originally expected them to be. As on the fossil reefs, we collected sediment samples between the thickets of coral heads, including brain coral (Diploria), star coral (Orbicella), lettuce coral (Agaricia), and starlet coral (Siderastrea). We even observed some of the same coral species that we had identified a week earlier on the fossil reefs.

While our qualitative observations suggest differences between the mid-Holocene and modern reef communities, the next step is processing the sediment we collected to characterize the microfossils left behind by the inhabitants of these reefs — both common and cryptic. Now we just need to get the samples back to Panama!

—Erin Dillon

 

¿Porqué los moluscos de hace 7,000 años eran mas grandes y fuertes?

Félix Rodríguez nos comparte unas observaciones sobre los fósiles de moluscos que hemos encontrado durante la expedición:

Después de los corales fósiles que hemos visto, los moluscos son los mas diversos y abundantes en los sitios donde estuvimos, tanto al norte como al sur del Lago Enriquillo. Lo que mas llama mi atención de estos moluscos es su preservación, algunos incluso

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Félix en Samaná, República Dominicana.

mantienen matices de color. Además  se ven como si estuvieran suspendidos en el tiempo, es decir, son una real fotografía del pasado de hace 7 mil años. Otro aspecto interesante de estos moluscos fósiles es su gran tamaño y grosor, comparándolos con los actuales, que son mas pequeños y frágiles, siendo las mismas especies  en algunos arrecifes donde actualmente estamos trabajando. En mi mente surgen varios interrogantes: ¿Qué ha cambiado? ¿eran mas longevos los moluscos que hoy día? ¿había mas alimento para ellos? ¿es por esta razón su talla y grosor? Por el momento, no hay una respuesta, pero de seguro esto nos ocupará tiempo en responder.

 

Exploring Punta Cana in pictures

With fantastic help from Victor Galvan and the team at the Punta Cana Ecological Foundation, we found a few underwater sites with potential for the dermal denticle project. The foundation also showed us their successful coral nursery and out-planting sites for Acropora cervicornis, which is being placed on dead reefs for recolonization. A no-take zone that covered one reef site was impressively full of fish for a degraded reef site, a sign that populations can recover quite quickly, even in a small area where no fishing is allowed.

Blue Vision Adventures kindly gave us access to their excellent dive facilities.

Modern Caribbean reefs: where are the sharks?

Sharks aren’t easy to spot on many, if not most, Caribbean reefs these days so figuring out what species remain and in what amount is a daunting task. Even though sharks are rare, they still leave traces behind — dermal denticles, their tiny tooth-like scales. Finding these can tell researchers like STRI fellow Erin Dillon what a shark community looks like, no matter how small it is.La Caleta (1 of 4)

But finding dermal denticles is only slightly less difficult than seeing a shark on a reef dive. They are so small that most can only be seen under a microscope and even relatively large concentrations are equivalent to about 25 per 10-kilogram sack of sediment. So identifying the correct site to sample is essential. These spots are often what scientists call low-energy sites, meaning they are not subject to strong wave action or currents, which sweep tiny particles like denticles away.

When a potentially apt site is identified, it’s time to get to work. Today, Erin and Mauro Lepore dug up some 100 kilograms of sediment. Doing so required that they carry more La Caleta (3 of 4)weight than usual in order to stay put on the sea floor when pushing into the hard surface. Otherwise, each thrust of the trowel would push them up from the bottom. It’s also important to avoid losing any fine sediments by digging too vigorously. When each sample bag is full, Félix Rodríguez, the O’Dea lab manager, drops a line down with a mesh bag and hoists the bags to the surface.

Erin, Mauro and Félix are just beginning their trek around the reefs of the Dominican Republic. Over the next few days they aim to gather another half ton of sediments. And while that might sound like hard work, once the samples are back at the lab of STRI scientist Aaron O’Dea in Panama, it will take a solid year (and an intern or two) to digest all the material (a process that involves copious amounts of acid). This, they hope, will get us one critical step closer to learning just how drastically shark communities on Caribbean reefs have changed since humans became the major driver of their decline.

The team tackles a 12-meter wall of fossil coral

We made it to Las Clavellinas and its monstrous wall of Acropora Cervicornis, a reef-building coral that is a threatened species today but was clearly abundant in Caribbean reefs 7,000 years ago. Here we collected another five bulk samples (10-kilogram cloth bags), and ten smaller bags, that will be brought to Panama and painstakingly picked apart for their tiny shark dermal denticles (all 25 or so per bag), sponge spicules, mollusks, and corals. The amazing Mauro Lepore and Félix Rodríguez were the climbers-in-chief, but everyone on the team had the chance to hack a bag of samples out of the hard fossil wall.

 

 

Coral and cacti: collecting fossils in Owl Canyon

It took a few wrong turns but we made the trip to the Cañon del Buho (Owl Canyon), on the shores of the Dominican Republic’s Lake Enriquillo.

Stay tuned for more updates and videos. Here are some photos from the field trip.

 

What do shark scales say about their owners?

In this shark tale for Save our Seas Foundation, Erin Dillon explains the characteristics of some of the shark scales found on four well-known shark species. Erin is pioneering a new technique that uses these scales, known as dermal denticles, found in modern reefs and the fossil record to study changes in shark abundance and community composition over time.

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Erin carries a bulk bag of a fossil reef sediment from Cañon del Buho in the Dominican Republic on March 17, 2016. The ten-kilogram bag may hold some 25 tiny shark scales known as dermal denticles.

 

A quick sundown stop at a huge fossil reef

First stop before Jimani (1 of 3)

Erin, Félix, Aaron and Mauro take a quick look at fossil reefs excavated along the road around Lake Enriquillo

We reached the banks of Lake Enriquillo just before nightfall. A new road has been cut through the Holocene fossil reef — to circumvent the steadily rising hypersaline lake, which is 40 meters below sea level — and the spoil of fossils line the road for kilometers.  Acropora cervicornis (staghorn coral) is the dominant species found here, along with a variety of other coral species, snails and clams. Nightfall and a brief rain kept the exploratory visit short. The serious sampling begins tomorrow…

First stop before Jimani (2 of 3)

Erin and Mauro and fossil corals aplenty.