Baseline Caribbean

Tetiaroa: sampling a little piece of paradise

Tetiaroa is an atoll I never expected to visit. Privately owned by Marlon Brando, this island hosts an interesting mix of hotel guests (paying €3000-4000 per night to stay in luxurious beachside villas), staff, and researchers. Upon becoming enamored with the island’s beauty and later purchasing it, part of Marlon Brando’s vision was to preserve and showcase its natural resources as well as facilitate scientific investigations. As such, the Tetiaroa Society was born, and an ecostation was constructed to provide logistical support for visiting researchers like us.

But why Tetiaroa? Let me back up a bit. First off, why is the Baseline Caribbean team in the Pacific? The short answer is that we can use similar sampling techniques to answer interesting ecological questions about the histories of coral reef communities across wide gradients of reef health, oceanographic conditions, and human settlement histories. Sharks are also much more abundant on many islands in the Pacific than in the Caribbean, making it more feasible to retrieve high-resolution chronologies of predator assemblages over space and time. In other words, we can get more bang for our buck, or more denticles in smaller samples. It’s a win-win situation.

Within the Pacific, French Polynesia is an ideal study system for several reasons. Here, sharks are ecologically important, revered in Polynesian culture, and help bolster tourism. French Polynesia was also recently designated a shark sanctuary. Within French Polynesia, the islands have different human settlement histories and are known – at least anecdotally – to have varying numbers of sharks. First, we can leverage this gradient to quantify how shark abundance and diversity differ spatially across islands. Second, we can explore temporal patterns of shark abundance and diversity in parallel with the diverse human histories of each island. For this study, we decided to collect samples from Moorea, Tetiaroa, and Rangiroa, which span this gradient and are easily accessible.

Tetiaroa is geographically close to Moorea and Tahiti (Society Islands), which have high population densities and human histories stretching back at least 1000 years. Tetiaroa is a bit different. While it was discovered by the Polynesians around the same time as the other Society Islands, it did not host permanent human settlements until centuries later. In its early history, it was visited infrequently and its resources were exploited at low intensities by people inhabiting the other Society Islands. Even later, its resident population was much smaller than that on Moorea or Tahiti, and it was used as a retreat by Polynesian royalty in the 19th century. Today, there are no permanent residents, and half of the reef and lagoon has been set aside as a marine reserve.

This brings us to the other day, when we departed Moorea to begin our journey to Tetiaroa. We were originally scheduled to take a boat from Tahiti. However, the bad weather that plagued our sampling efforts on Moorea struck again. We received an email two days before our trip informing us that the boat was cancelled but that we might be able to take a plane instead. Our plans were turned upside-down as we waited in suspense. Would we actually make it out there after so much preparation, or would our plans be thwarted?

The evening before we were supposed to depart, I received another email confirming that a flight was indeed available. The catch was that we had a luggage allowance of 10kg each total. We started scrambling to get everything packed. What would stay on Moorea until the end of the trip? What did we absolutely need in Tetiaroa? What would we leave in Tahiti and take with us to Rangiroa? I currently have personal items scattered across three islands as I write this blog post. With all our sampling gear and SCUBA equipment combined, we really only had room for a t-shirt, a bathing suit, and a toothbrush. Talk about traveling light! Even then, we were over the weight limit. Luckily, they let it slide.

Air Tetiaroa does not fly out of the regular domestic terminal at the Papeete airport. They have their own private building and security, and they serve fancy juices for free in the waiting area. We indulged in a small piece of this luxury that we could otherwise never dream of affording.

The flight was only 20 minutes, but it provided a breathtaking view of Tetiaroa. Yesterday, the wind had been too strong for the plane to land. Today, we were in luck. The Twin Otter plane was wavering back and forth as we approached the tiny runway for the final descent. Even seconds before contacting the pavement, it felt like we were undulating in the wind. Despite these rough conditions, kudos to the pilots for a solid and safe landing. We had made it!

We were greeted with strong winds and a downpour. This would be a continuing trend during our days on Tetiaroa. But more on that later.

[to be continued]

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Get your optimism from the past

When we think about a “pristine” untouched ecosystem we often have a single, preconceived image in mind. It could be a grassland with thousands of bison, a thick tropical forest, or a coral reef teeming with fish and sharks. These places certainly existed, and in many cases are now lost or replaced by alternatives, but there has always been variation and not everywhere would fit into these limited boxes. There must always have been marginal ecosystems and vast amounts of variation.

It is this variation that we propose can help conservation. If we can describe that variation we can do a better job at placing modern ecosystems into context. In this paper, published in Conservation Biology, BaselineCaribbean members discuss our ideas of how the fossil record can be used to redefine what should be considered “pristine” and the positive benefits of doing so for conservation.

Open Access available

O’Dea, A., M. Dillon, E., H. Altieri, A. and L. Lepore, M. (2017), Look to the past for an optimistic future. Conservation Biology. doi:10.1111/cobi.12997

DCIM105GOPRO

DCIM105GOPRO

What’s in a sample?

Monday was a good day. We met our boat exactly where and when planned (a first!) and motered south to Caracasbaai, past the colorful buildings of Willemstad, a towering cruise ship, and a fleet of tiny sailboats that looked remarkably like the schools—flocks? — of flying fish that also skimmed the waves. Erin easily located a potential denticle site in a short snorkel foray, and the dive team quickly got to work filling the sample bags. While they worked, the boat captain tossed in a fishing line baited with what he’d caught on the trip down. By the time Felix and I were winching the samples up to the surface, more fresh fish sizzled on the boat’s tiny stove. It is immensely satisfying to snack on fresh fish and simultaneously admire a pile of fresh samples. Like I said, it was a good day. We traveled back to Piscadera with tired bodies, satisfied stomachs and 20 bags full of denticles.

…Well, not quite. The sample bags are filled with fine-grained reef sediment, which may or may not contain denticles. So, why are we collecting bags and bags of sand anyway? It may seem like a strange way to determine the relative health of a coral reef ecosystem, much less shark abundance. However, hidden within the reef sediment is a time-averaged sample of some components of the reef ecosystem. It’s similar to a school’s lost-and-found: over time, the accumulated detritus preserves a sampling of the year’s fashion trends and fads. Grabbing a sample of the lost-and-found might better represent the school’s generalized clothing choices than an hour’s observation during gym. Similarly, observing a reef during the day (when humans are most active) may not accurately represent the diversity of the reef’s inhabitants, or provide a good way to compare a declining reef to a “pristine” reef less impacted by, or familiar to, human presence. The reef sediment is analogous to the lost-and-found: the denticles, shells, teeth, bones, and other hard parts are the cumulative signal of the reef’s inhabitants. While not every part of the reef is preserved, what is preserved can be compared between sites and across time to assess key differences in reef diversity. The sediment is a way to look at several years’ worth of diversity rather than assessing the reef based on a couple days of highly-variable observation.

At present, it appears that sharks are uncommon in the waters surrounding Curacao. We haven’t seen any in our time here. In contrast, anecdotal evidence suggests that sharks were very common in the past. The samples collected on this trip will hopefully address this disparity. Furthermore, other members of the O’Dea lab will look at otoliths (fish ear bones that preserve growth history much like tree rings do), molluscs, bryozoans and other components of the sediments, trying to piece together a broader picture of the reef’s health. Hopefully, the sediment collected in this field trip will show how the reef we see today—the reef which supported the delicious, though small, fish we snacked on—compares to the reef’s recent years, and how that compares the reef before humans arrived. Just as the bulk sample bags preserve a time-averaged history of the reef’s inhabitants, they also preserve the time-averaged impacts of industry, tourism and fishing on the reef’s health. That’s pretty good for a bag of sand!

An unexpected trip to Curaçao

“How would you like to go to Curaçao?” These were not the words I expected to hear when I answered my phone after the third consecutive call from an “Unknown Number” on Monday night. Thirty-six hours later, I was dragging a heavy metal object through the airport on my way to join the search for shark dermal denticles. My surprise journey with the Grab Sampler is only part of what is becoming an epic battle against Murphy’s Law in the ongoing Denticle Quest of the Baseline Caribbean team. This post details some of the obstacles the team has already overcome. You can watch many of these events unfold in the live-science videos.

Obstacle 1: Small Denticles

Shark dermal denticles are small—smaller than a grain of salt—and you might think that collecting denticles would be harder than finding a needle in a haystack. However, their small size helps the Baseline Caribbean team narrow down potential denticle sites. In areas washed by waves or current, any denticles would likely be swept away. Consequently, denticles only accumulate in low-energy locations where they can settle undisturbed. These sheltered locations are what the team is seeking in “1: Looking for Sites.” Silty sediment is an indication that the water is quiet enough for the denticles to remain.

Obstacle 2: Deep Denticles

The team came prepared to scuba dive in and dig for denticles by hand. You can see them at work in “2: The Perfect Sediment.” However, it turns out that in Curaçao at least, much of the “perfect sediment” is deeper than the divers are prepared to go. So, how to collect these deep silty sediments without diving? The Grab Sampler provides a solution: it is a heavy metal scooper that can be lowered over the side of a boat to collect deep sediments. Problem solved, right? …except that the Grab Sampler remained in Panamá. Lucky for me, the easiest way to get it to Curaçao was for me to bring it. I got to travel to Curaçao, several customs officers got to learn about the mysterious metal object in my luggage, and the Baseline Caribbean team got back to work, digging denticles.

Obstacle 3: The Grab Sampler works! And then it doesn’t.

The Grab Sampler may look like a boring metal scoop, but it is actually an instrument of high drama and suspense. After it’s lowered over the side of the boat, it sinks into the blue depths and disappears. The line keeps feeding downward, down past the rising bubbles, down farther until suddenly it goes slack: the Grab has hit bottom. Quickly, all hands go to the rope, everyone sweating to pull it back up and wondering what it will bring. That first retrieval, we all crowded around, watching as it surfaced, watching as Felix swung it over the side, leaning in to see… a single algae-encrusted shell deposited on the tray. The second go brought nothing. We tried a slower descent, than a faster one. We moved shallower, then deeper. Finally, we started bringing up the silty material we were looking for. Success! We danced the Denticle Dance, and our collection of sample bags started growing.

Unfortunately, that was not the end of the Grab Sampler’s drama. As we sent it down again, the wind picked up, pushing the boat over the descending line. The Grab Sampler must have dragged along the bottom, because when we retrieved it the sturdy metal was bent out of shape, rendering the instrument useless. As we research options for fixing the Grab, the team is back to diving for sediment in the sites that are not too deep.

. . .

Beyond these obstacles, the team has struggled against 75 million-year-old radiolarians (the backbone of the island is silica-rich rock made of ancient plankton skeletons, and as it erodes into the bays it makes the denticle search more difficult), wary property owners, Carnival traffic, difficult-to-find docks, and even an issue with the coast guard. Yet even when it seems that everything that can go wrong does go wrong, the team finds a way around the problem and the search for denticles continues.  This is how science works—often it is the challenges that lead to creative problem solving, novel approaches, and interesting new questions. And sometimes when things go wrong, an intern gets to go on an unexpected trip to Curaçao.