Palmyra Atoll

A sediment core inspired road trip

US GEOLOGICAL SURVEY MENLO PARK CAMPUS
MENLO PARK, CA

As coral reefs accrete upward, their histories become buried beneath the surface. One way to unravel this history is to visit areas where the older reef has been exposed by excavations, road cuts, or storm channels. This is what we did in Bocas del Toro, Panamá and in the Dominican Republic’s Enriquillo Basin. In most places, however, living reef or mangroves grow on top of the Holocene reef. To access the underlying history, we can insert several-meter-long sediment cores into the substrate. While this technique samples a sliver of the surface area of a reef, it has the unique advantage of looking back in time. Depending on the rate of reef accretion and sedimentation, sediment cores can travel back several hundred to several thousand years with high temporal resolution. The remnants of the animals and plants captured in these cores help paint a picture of the reef in the past and how it has changed over time.

Today, I had the good fortune of sampling a gravity core extracted from Palmyra Atoll’s lagoon by a team of USGS scientists. In addition to being home to numerous sharks, Palmyra has an interesting human history despite never being settled. The atoll was originally discovered in 1802 when an American ship was blown off course in a storm. In 1862, Palmyra was claimed by the Kingdom of Hawaii, and it later became a U.S. territory following Hawaii’s annexation and subsequent statehood. At that time, it was privately owned by the Fullard-Leo family. During WWII, the U.S. Navy took over and drastically altered the atoll for use as a naval air facility. Afterwards, it was occasionally frequented by yachters despite its remote location – a nearly 1000-nautical-mile sail southwest of Hawaii. From 2000-2001 onwards, the atoll has been under the protection of the Nature Conservancy and U.S. Fish and Wildlife Service as a National Wildlife Refuge, and a handful of scientists and donors visit each year.

The 3.2m-long sediment core that I sampled covers nearly 650 years of history on the atoll, capturing its pristine state prior to discovery in addition to the last 200 years of sparse human occupation. We will use the core to begin investigating whether shark baselines on the atoll are naturally dynamic and whether the abundance and diversity of sharks changed after the arrival of humans. Palmyra has been the location of many shark tagging and survey studies over the last 12 years since the creation of the Palmyra Atoll Research Consortium (PARC), and it is considered to be a relatively untouched, healthy reef ecosystem. This new historical time series will help us understand whether its condition has fluctuated over time before these monitoring efforts began.

This opportunity was certainly worth the 10-hour round-trip road trip from Santa Barbara to Menlo Park, which is located about 40 minutes southeast of San Francisco. In addition to picking up the core from the sample storage refrigerator on the USGS campus, my secondary aim was to use their facilities to slice it into 64 5cm-long segments, each representing about 10 years of reef history. The core was composed of very fine, silty material, so cutting through it was not difficult with the help of some metal utensils and a meter stick. Furthermore, the challenging task of cutting the core in half through the PVC piping had already been accomplished. I carefully measured and cut each section and placed them into individual labeled plastic bags. After several hours of meticulous slicing and record keeping, I had amassed quite the pile of samples and was caked in a thin layer of dry mud.

My 250 pound delivery

Today was my lucky day! All of my precious samples are now here and ready to process. Hilariously, the mail distributors on campus lugged them up to the mail room on the 3rd floor, just so I could bring them all the way down again and into the building across the way where the lab is located. With the help of an old rickety cart (that fortunately did not collapse under the weight of the sediment), all of the boxes were transported in two exhausting trips. Another chapter of field work closed. May the sieving begin!

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Getting the samples packed up and shipped home

Now the time had come to get all of the sediment home, which proved to be a tad tricky. First, we had to get the samples to Honolulu. As plastic crates are bulky and expensive, I ended up packing the individual samples into ten sandbags. What better to use than a container designed for sand?

The charter flights off the atoll are both few and far between and weight restricted. Luggage is limited, and they sometimes swap people around in the plane for takeoff and landing. Therefore, fitting 250lbs of sediment onto one flight was not going to happen. The pilot was even grumbling about putting 1-2 bags on the plane. In fact, the sediment was shipped off the island on three separate flights over the course of about two weeks! I was still on the island (having transitioned by that point to bug counting and tree measuring), so I was able to help orchestrate this operation. Fortunately, one of the donor trips did not bring much luggage, so I was able to fit the majority of the bags on that flight. Later, I certainly breathed a sigh of relief when I had accounted for all ten sandbags at the airfield in Honolulu.

The next step, of course, was shipping the sediment samples back to the mainland. For anyone who’s shipped anything large or heavy recently, you know that it can add up fast. To partially circumvent this cost, we shoved the samples into 11 large flat rate boxes and sent them on their merry way only $200 later. This sounds simple enough, but it involved a lot of (somewhat unnecessary) running around the city. However, after this ordeal, we still had several hours to kill in Waikiki before our flight home. As a side note, the abrupt transition of living on a tiny remote island with 20 other people to arriving in the bustling tourist town of Honolulu was quite overwhelming! Particularly because it was Halloween.

The next few days were spent anxiously checking the package tracking information. Would the samples arrive in one piece?

Some pictures from today’s snorkel at North Barren Island

Today we went on the snorkel of a lifetime. Or perhaps it was just Palmyra’s way of saying goodbye, as this was also our last snorkel of the trip. I followed a couple of juvenile blacktip reef sharks around the reef, was circled by a curious turtle, and was blown away by the number and diversity of fish I observed. Despite being damaged by coral bleaching last year, this reef is incredibly resilient and is now on its way to recovery. Absolutely amazing!

The final samples

Today was our last day of diving. It was bittersweet, for sure. We motored around the reef terrace in search of patches of sediment. While we were limited by the placement of moorings and inability to anchor (not allowed on the terrace for good reason), we still managed to collect sediment from one more section of the reef. I was quite pleased with our haul! Below is our final sample count:

  • 14 collection sites, 7 on the reef terrace and 7 in the lagoon
  • 10 replicate sediment samples taken at each site, except for one which had very little sediment available to sample
  • 131 bulk bags total, weighing roughly around 250lbs

The next challenge: getting it all off the tiny atoll on the weight-restricted charter flights.

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Sample bags drying in the sun to reduce their weight and save us money.

Exploring the hospital: a relic of a bygone age

Tromping through the jungle and forging our own path through the thick vegetation, we must have walked right past the old WWII-age military hospital a handful of times without even knowing it was there. This time, though, we were on a mission to find it.

We came across a machete-cut path through the Cocos seedlings and followed it until we practically ran into the structure itself. It was completely overgrown and barely discernible from the surrounding trees. We followed the concrete perimeter to the entrance and ducked inside. It was as if we had been swallowed by pitch-black darkness. We switched on our headlamps to illuminate our grim surroundings. Our voices echoed eerily in the domed entryway.

The structure was impressively still intact (the ceiling was only falling down in one spot), although some of the interior had been gutted. The building was massive, possessing at least two wings and three entry points. You could still walk down what would have been the hallway and glance into the various rooms, now lacking walls or doors. Rusted cabinets and beds lay strewn about, lost in time. It was haunting to imagine the men that used to inhabit this place: doctors strolling down the corridors and patients lying wounded in the beds. Now, all of this history had been swallowed up by the jungle, and the only remaining denizens are cane spiders and several-foot-long coconut crabs. Yet another example of nature taking back the atoll for its own.

A day in the life

6:30am – Alarm rings. Go for a run or do some work in the lab before breakfast.

7:00am – Load the boat and prep SCUBA and sampling gear.

7:30am – Breakfast in the galley. Pack lunches and fill water bottles. Sunscreen up!

8:30 or 9:00am – Depart the dock for our first site.

9:30am – Arrive at our first site. Check out the substrate suitability on snorkel. Dana and I don our SCUBA gear and jump in.

10:20am – Finish sampling our first site. Depart for our second site.

10:50am – Arrive at our second site. Snack time!

11:00am – Scope out site and start sampling.

11:40am – Finish sampling our second site.

12:00pm – Lunch on the boat. Enjoy the scenery.

12:30pm – Move to our third site (or back to the station if only sampling two sites).

1:00pm – Arrive at final site for the day. Scope out on snorkel.

1:15pm – Start collecting sediment on SCUBA.

1:50pm – Finish collections. Head back to the dock for the day.

2:30pm – Arrive at the station. Wash and store gear. Carry samples to the lab to dry.

3:00pm – Afternoon coffee break or snack time.

3:30pm – Record GPS points and sampling notes for the day. Select sites and make a plan for tomorrow’s sampling. Arrange boat usage with the station and other researchers.

4:00-6:30pm – The work doesn’t end here. Help the other UCSB team sort insects, write a grant proposal, read papers for the class I’m supposedly taking on campus, edit a manuscript, etc. Put on a sparkly gold flash tattoo with the rest of the team for field solidarity.

6:30pm – Dinner in the galley. Watch the sunset. Don’t forget your headlamp!

7:30pm – Stroll back to the lab. Or perhaps to the yacht club for some evening fun. Pet a manta ray.

9:00-10:30pm – Bedtime. Maybe see a fluorescent blue-purple coconut crab on the way back to my cabin. Be careful, as it could pinch your finger off.

[Repeat.]

A jaunt around camp

For a remote tropical island, Palmyra’s field camp is quite nice. First, we are fortunate enough to eat fantastic food… when the vegetables actually make it on the plane from Honolulu. For example, Alex, one of the chefs, made breadfruit pita and a heart of palm salad for dinner with sweet potato haupia pie for dessert one day. I wasn’t expecting to get to try new foods while in the field, so this was a welcomed surprise! Second, there are showers and washing machines, although water is limited as we in a drought and the field station is completely reliant on rainwater. Cleaning chores rotate between groups of researchers. Third, we stay in small but cozy cabins shared between two researchers. Some of them are even waterfront, although the donors were assigned to those when they flew down to visit.

With regard to the science, there is both a wet and dry lab to process samples on the island. One researcher even brought a tiny -80C freezer to keep samples cold before being transported back to Hawaii. We have access to four lagoon boats (shared between all researchers on the island), and there is also a larger boat for diving on the forereef. There were on average 23 people total during my stay, so resources weren’t spread too thinly.

When you’re not working – although it’s a pretty constant state of working – you can explore the main island Cooper and the adjacent island Strawn, stroll to North Beach, go swimming at the swimming hole, relax in the galley or yacht club, or run on the runway. We even have science presentations and movie nights in the yacht club and bonfires on North Beach occasionally.

Sunrises, sunsets, and avian friends

The sun rises a little before breakfast, so I occasionally head over to North Beach with my cup of coffee for a moment of tranquility before the hustle and bustle of the day begins. Later, the sun sets just as we’re having dinner. First, this means that you are in for a pitch-black stroll to the lab if you forget your flashlight or headlamp. However, it also means that we have a spectacular backdrop after a long day of field work. Rayn, the resident rescued red-footed booby, will occasionally sit outside and enjoy the sunset with you when she’s not begging for attention. Today, she’s the star of the blog post.

Gateway to the lagoon

On a good day, you can see the bottom of the channel from the boat. Today was not one of those days. What’s lurking out there beyond the edge of the murk?

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The channel has been identified as the main elasmobranch highway between the reef terrace and the lagoon. Acoustic receivers and cameras placed along the edges of the channel have pinged the positions of many a manta ray or shark cruising through, even documenting a “shark rush hour” in the evening. There’s also lore of a lone gray reef shark known as “The Gatekeeper” that supposedly patrols the entrance to the lagoon. Obviously it’s a very sharky place.

While sampling, we were easily circled by ten blacktip reef sharks, although not all at the same time. I would shovel a couple of scoops of sand into my bag, glance hurriedly over my shoulder into the heart of the channel, and catch the eye of several blacktips that were checking me out. We would politely exchange glances, and then they would meander off into the murk. Dana and I also spotted a gray reef shark from the boat immediately after getting all of our gear back aboard. While the paranoia of something really big coming up behind me may linger in the back of my mind, I look forward to these encounters. It was incredible to get to dive with these majestic creatures and be a part of their world, if only for an hour at a time.