INTRODUCTION
I will be spending 6 days at sea and in the Bahamas on the R/V W. G. Walton Smith. We leave port in Miami on Thursday March 18, 2010, and return on the evening of Thursday, March 24. We will travel to Highbourne Cay. There are 10 scientists and 6 crew on board. The purpose of the trip is to study the stromatolites and thrombolites on Highborne Cay, in the Exhuma Cays of the Bahamas.
R/V W. G. Walton Smith
Stomatolites and thrombolites are 2 types of microbialiates. Microbialites are organic/sedimentary structures made of microbial mats (different types of microbes all hanging out in a … you guessed it… mat of slime and cells) and preserved by precipitation of calcium carbonate and/or trapping and binding of carbonate sediments. They come in many shapes and forms. Stromatolites are layered structures, as opposed to thrombolites, which have clottted texture.
Microbialites are interesting and important to study because fossil stromatolites represent the oldest reliable (although still controversial) evidence for the presence of life on earth. Stromatolites as old as 3.5 billion years old dominated the fossil record for nearly 85% of Earth’s history. The only way to learn about the formation and preservation of ancient stromatolites is to study modern ones. If we can elucidate the mechanisms leading to the formation of today’s stromatolites, we may be able to look at the fossil record and interpret the environmental conditions in which early life thrived.
Today, the only location of modern stromatolites in open marine waters is in the Exhuma Cays, in the Bahamas. Stromatolites can also be found in Shark Bay, Western Australia, in hypersaline conditions. The fossil record of stromatolites is sparse, because once multicellular eukaryotes evolved, they and grazed on stromatolites, which is why Stromatolites are still difficult to find today. Stromatolites can form in Shark Bay because the hypersaline water would kill any animals that might eat the mats on the stromatolites. It is hypothesized that stromatolites survive in the Exhuma Cays because they grow on thin long reefs along the Cays. These reefs are only a few hundred feet wide, and are bordered on the side by 1200+ foot drop-offs with strong currents running along the sides of the reefs. Also ooids (spherical layered carbonate concretions) are washed on to the reef, and the water is so full of ooids that life as a grazer on the platform, if a grazer could make it ON to the platform, would be difficult because of constant bombardment by ooid grains. Life as a stromatolite is not easy today, so they are only found in these unique marine environments.
Since I am a first-year graduate student, my role on this cruise is not very defined. I will be assisting Lexy (my first-year lab mate and good friend) with mapping the substrate (underlying surface) of the stromatolites on one of the islands. I will also assist Pieter (one of my two advisors, Christophe is not on this trip) with measuring chemical gradients in the microbialiates. Other scientsts on the boat (principal investigators [PI’s – aka professors], post-doctoral students, and graduate students) are studying the internal structure of thrombolites, molecular biosignatures of eukaryotes in the microbialites, and other related subjects. The unifying theme for all of the research here is: What can modern microbialites tell us about life deep in Earth history? How can we recognize early life on Earth? How might fossil or extant life be discovered on other planets? How can we recognize life and what can it tell us about the environment in which is evolved and thrived?
DAY 1
Colin and I left my apartment at 3:30AM. We picked up Lexy and made it to the airport at 5:30. We waited half an hour in the check in line. We joked that as soon as we got to the front of the line, Pieter would show up and whisk us through the first-class line (he’s a VERY frequent flier, so he pays coach and gets everything first-class), and all the waiting would have been in vain. Our prediction was correct. Lexy and I both stayed up all night packing, so we slept like rocks on the plane. We arrived at 9:30 AM in Miami. We got our bags and our ride arrived. We drove to the dock at the University of Miami Rosentiel School of Atmospheric and Marine Sciences (RSMAS) on Cay Biscayne. I learned that bunk rooms are small, and my suitcases are not. Lexy made fun of me for hours about my lack of packing skills. Everyone on board found out that I brought a blow dryer, and I’m never going to live that down.
We spent the day on the boat at the dock. The PI’s went out to get provisions and a fancy fishing rod. The staff loaded the boat with food for the trip, and a gas truck filled the tanks. The water is desalinated and treated on the boat. Water is not scarce, which is a relief. We have plenty for drinking, cooking, and showering (5 minute limit, but not strictly enforced, so it’s not bad). I spent all day making up for only sleeping 9 hours the last three nights. I stayed up working late for a few nights because I was told that there was no internet access on the boat. (At the moment, I’m checking my email offshore in the Bahamas!) Turns out we do have slow internet via satellite, but I’m relieved to have all my work done.
We had dinner out about a mile down the street. I put on a patch to fend of seasickness, and went to bed.
DAY 2
Leaving Miami
We left port at 8 AM. After leaving, we had a safety meeting and muster. By this point, the water was more rough and I started getting ill. As soon as muster was over, I found a seat on the back deck, looked at the water, and it was only place on board that I did not feel ill. I spent all morning and a good part of the afternoon in that chair. Lunch was delicious. I had to RUN through the cabin, snag lunch, and RUN back outside before I got ill. Running on wobbly sea legs was pretty difficult. The gulf stream had 3-6 foot swells, but it was an easy crossing compared to what it is sometimes like. I was ill, but lucky it wasn’t worse. I actually did pretty well until I went into the lab to fill out my customs form. After that, I was in big tummy trouble. I managed to run into my cabin while we were stopped at Bimini Island for customs, and fell asleep quickly, thanks to the seasickness patch. I woke up 3 hours later at 6:30 PM in calmer waters, and I’ve been doing fine since, thankfully. Dinner was delicious. I stayed up late reading Bekah’s paper, just published online in my favorite journal. It will be published in print in the next few months. It felt great to know that a project I spent ~3 years working on is now published and that I’ve helped make a contribution to my field.
DAY 3
Stromatolites!
I woke up at 7 AM, since Lexy and I still hadn’t figured out what time breakfast is served. I downed 2 cups of coffee since the patch makes me even more sluggish than usual in the mornings. We arrived at Highbourne Cay at 10 AM. We walked to the beach on the other side of the island with a wheelbarrow full of gear and sampling equipment. We visited 10 sites where stromatolites or thrombolites are present, and determined the degree of lithification (is it a rock yet?) and type of microbialite at each site. I was so excited to finally see modern stromatolites! There were some pretty awesome fish too. We returned to the boat for lunch. We had conch salad – and I tried it. I know it’s just a big snail, but I don’t find it nearly as revolting as garden snails. We returned to the field after lunch and did some sampling and took some measurements.
After our second field excursion, Lexy and I were going to head to a nearby beach for some swimming. As we walked down the dock, we saw a HUGE nurse shark swim underneath us! We told the boat crew, and they said lots of nurse sharks tended to hang around another dock, so Lexy and I made our way there. Just around the corner from the beach, and right at the end of the next dock over, there was a fish gutting station with at least 13 nurse sharks swimming around below! These were big sharks – around 6-10 feet, I think. The fishermen were friendly and Lexy threw some scraps to the sharks. There was also a black-tipped reef shark and a couple of huge groupers, some pilot fish, and some other small fish. It was really amazing.
Nurse Sharks at feeding time
DAY 4
Lexy and I went out to the beach at 9 AM to take some measurements and collect samples. However, the conditions were not great and the rest of the group was nowhere to be found, so we decided to go back to the ship and wait for low tide. We wound up at the swim beach and did some seashell collecting. After lunch we went back to work. We took photographs all along the beach and recorded GPS waypoints by each of the different microbialite sites. The rest of the group came out at 3:30 and we helped them with sample collection. I almost lost my voice from yelling over the sound of crashing waves all day. I collected some samples and we went back to the ship.
After dinner, Lexy got a migraine, so I made her go to bed. Then, I sectioned up some samples and looked at them under one of the dissecting scopes, and made some notes.
DAY 5
I woke up very early. Pieter and I left before 6 am to go to the beach. Our plan was to use microelectrodes (they’re kind of like teeny tiny pH meters, to quote Bekah many years ago) to measure some element profiles through microbial mats on the thrombolites. Unfortunately, the wind was blowing 15-20 knots and the surf was making it very difficult. The electrodes are very expensive and easy to break. They are small probes with a needle attached, and you mount one on a base, put the base on the microbialite, connect the electrode to a meter (a clunky box) and screw the needle into the microbialite half a turn at a time, making sure that you don’t break the needle. We got through 2 oxygen profiles and 2 sulfide profiles before we had to call it quits. Unfortunately, We may have broken one of the electrodes. Pieter says that those were the worst conditions he had ever used the microelectrodes in, and that I had a pretty wild introduction to microelectrodes.
I returned to the ship for breakfast and most of us got ready to go to Allen Cay to see the semi-wild iguanas. Just as we were about to get into the boat, the fuse blew (again) thanks to the giant $22,000/week boat next door. When the power was restarted, something happened and TONS of soot blew out of our smoke stacks! Someone left the door to the inside of the ship open and soot blew into the ship and got EVERYWHERE in the lab. It got on everyone’s experiments, equipment, and even into the fumehood while someone was processing samples! It was all over us too. It was very greasy and it took a long time to wipe up off the counters and off of ourselves. Once everything was in a more manageable condition, we left for the iguana islands.
We rode in one of the ships two smaller power boats over to the islands. The boat was very small, and we crammed 6 of us on to it. We went very fast over slightly choppy water, and it constantly felt like I was going to be thrown overboard! I held on tight and now I have sore arms, legs, and a sore back. Everyone else enjoyed most of the ride.
Iguanas prefer potato chips
You can see the iguanas from the boat. They hang out on the beaches waiting for visitors with junk food. Most are skittish, but some will eat from your hand. They loved the bread we fed them, and only ate the lettuce long after we ran out of bread. The iguanas don’t look like typical pet iguanas. They’re pretty big, and they have fed frills and spines, and are more grey than they are green.
Showing off for the tourists
We had a slightly-terrifying tour of some nearby islands on the way back to the ship. We saw flying fish and skipping fish. When we got back to the ship, we were told to go to the beach while the crew finished mopping up the soot. The down-time was enjoyable.
Lexy and I spent the afternoon mapping one of the sites most frequently visited for sample collection. Lexy took photos while I sketched the shapes of the microbialites. We took GPS waypoints at recognizable locations along the beach, put these on the sketch map, and used a piece of string (measured later that night) to put distances on my map. I also collected some samples from the stromatolites. Some will be made into thin sections (slices of rock that you look at on a microscope), and some have been fixed with gluteraldehyde so I can look at them with a scanning electron microscope (SEM) in the next few months.
Sunset over the stromatolites
That night I almost completely lost my voice. Lexy had to speak for me all evening. I felt fine other than the sore throat and busted vocal cords. I can’t decide if I have a cold or bad allergies to something. The only time I ever had bad allergies was when I visited Miami for 3 days when I was in middle school. This could just be a reprise.
DAY 6
Lexy and I went to the beach straight after breakfast. We measured air temperature, water temperature, pH, and electrical conductivity (salinity) at each site. We also filled carboys with seawater, and collected filtered seawater samples for chemical analysis.
Lexy with the sampling wheelbarrow
Pieter had to leave early to meet with someone who donated money to the Center for Integrative Geosciences. He had to arrange a ride on a speedboat back to Nassau, where he will catch a plane to Miami, and then go on to Connecticut. Finding a boat ride was a bit complicated, but it worked out in the end. He had to pack his suitcase into garbage bags and his laptop and backpack into a dry bag to keep them dry, since the boat is open top, and it was pouring rain all morning and afternoon. I am taking the equipment box if it won’t fit into the car to MIT. After we helped Pieter pack the gear and after he left water suddenly starting pouring out of two of the AC units! One spilled onto one of the ship’s general use PCs and the other poured water onto a shelf in the wet lab, wrecking some of our mystery samples (they belong to us, but neither Lexy or I knows what they are for). Gallons and gallons were pouring out for a long time. There were huge buckets ferried in and out to get rid of the water. The crew eventually got it under control. Turns out that the outlet for rainwater that collects on the top level of the ship was blocked by of the he buoys that keeps the ship from bumping into the dock. The water backed so far up the system that it started pouring out the AC units.
One of the best things about this trip is the aquatic wildlife. I like to visit the nurse sharks every day or so. They aren’t very active when they aren’t being fed. They are like giant sleepy puppy dogs. They look really cute and friendly. There are barracudas everywhere in the marina. They hover, dead still, in the water. There are also some spotted eagle rays that cruise around the island and in circles in the marina. In the marina I often see two of them together. One is small, and the other is very large and has a fish attached to it. I often see a solitary one cruising North to South along the stromatolite beach, and I think sometimes it comes around to the swim beach on the marina side of the island. There are these sponge-anemonie-looking things on the seabed in the harbour. We’ve been debating about what they are for days. Today we discovered that they are upside-down jellyfish! They are very pretty when they are right-side up.
The boats in the harbor are downright silly. The yachts all have staff, and staff seem to spent most of the day cleaning the yachts! Some of the yachts are longer than our 100 ft research vessel. They routinely blow the circuit breakers when they are on marina power. There are also big expensive looking sailboats. Everyone here must be rich. We are the poor grad students and middle-class to lower-upper-class scientists and researchers amongst all these ridiculously rich boat owners. We have a big clunky green research boat with an A frame and cranes amongst all these fancy boats. I feel like a rebel.
DAY 7
Sampling time
Today, Lexy and I went down to the beach at dawn to do some last minute sampling. The weather was beautiful again, like it was when we first arrived. I collected some samples from the stromatolites and we headed back to the ship. We wrapped all the samples and put them in Tupperware for transport. Then we had about 2 hours of actual vacation time! That was soooo nice. We went to the store at the marina (I got a shell covered jewelry box) and to the dock to say goodbye to the sleepy nurse sharks. The ship started moving at 1PM. I quickly slapped on a scop patch, and so far I’ve been absolutely fine. We haven’t hit the gulf stream yet, but rumor is that this ride will be much smoother than our outgoing voyage. We clear customs at Bimini Island at 5AM. We should be in Miami between 2 and 4 tomorrow. I’ve spent the day eating, relaxing, and trying to talk less and avoid losing my voice for the third night in a row, thanks to my cold.
DAY 8
Back in Miami
I made it across the gulf stream without getting sick! We had a great transit. The water much more calm than on the first day of our trip. We cleared customs in Bimini in the early morning. We arrived in Miami around noon. We had to stay on the boat until US customs came on board. They came on, talked to the captain, called us into the galley one by one, checked our passports, and then we were free to do what we liked. Our trip was over. Lexy and I will stay on board until we depart for the airport tomorrow afternoon.
REFLECTIONS
What an awesome trip! After 5 years of studying microbial mats, I FINALLY got to see living stromatolites! They aren’t exactly what I expected. Most were intertidal, and nothing like the post-card stromatolite photos from other parts of the Exhuma Cays or Shark Bay, Western Australia. However, there were some archetypal stromatolites in one spot (few feet tall, under a few feet of water, growing in small patches so I could snorkel in the middle of them and around them). I went snorkeling there on the first day at high tide, and I just remember thinking to myself that I felt like I was snorkeling in the Precambrian (the time when Stromatolites ruled the earth), until a school of fish swam by. There was a good minute of science-nerd bliss there, and that was one of the best moments of the trip.
The wild life was spectacular. I was surprised that by the end of the trip, I would look around in the harbor for the eagle rays and not be surprised when I saw them. I almost took them for granted! Spotted eagle rays! The sharks, the fish, the birds, the jellys – everything was amazing.
I really enjoyed spending time with the people on the boat. There was some boat-wide drama with one of the people on the ship, and that put a damper on the fun at times, but I don’t think any of us let it spoil our trip or override the good memories. I met some awesome people, and really got to know some of them well, and I look forward to seeing them again in the future, as I’m sure I will. The social interaction was one of the best parts of the trip.
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