Tropical Ecology

Heading: Woods Hole Oceanographic Institution and Massachusetts Institute of TechnologySub heading: Welcome to the 2013 Field Course in Tropical Marine Ecology !

With support from the Henry L. and Grace Doherty Professor of Oceanography Fund, we have again brought six MIT-WHOI Joint Program students to the Liquid Jungle Lab, located on “Simca Island”, a small remote island off the Pacific coast of Panama. In Fall 2012, the students prepared for the field course, by enrolling in “The Biology and Ecology of Coral Reefs,” a topics course within WHOI’s Biology Department.

We are now exploring coral reefs, as well as mangrove and intertidal environments. The course has a particular emphasis on interactions between the biological and physical components and on unique aspects of the Eastern Pacific coastal ecosystems. During this two-week course, the students will also develop and complete independent projects. Please stay tuned to future blog entries to get an idea of class activities, independent projects and other educational adventures!

On the first day of our journey, we flew from Boston, through Miami and into Panama City. The next day, after a painfully early start, we traveled by van and small boat to the “Liquid Jungle Lab”. We don’t travel light…in addition to snorkeling and dive gear, we brought microscopes, oceanographic surveying equipment and all sorts of vials, bottles, nets and sieves. Upon arriving on the island, we immediately launched into the first of a series of student-led lectures and began planning our field studies. It was quite a long day, but we are all excited to get in the water tomorrow.

This year, the participating students come from three WHOI departments: Hannah Barkley (Marine Geology and Geophysics), Melissa Moulton (Applied Ocean Physics and Engineering), Maja Edenius, Ben Jones, Emily Moberg, Katie Pitz (Biology). We are fortunate to receive assistance from Vicke Starczak, a former resident of Panama and seasoned expert in the local mangrove environments. We hope you enjoy reading the blog postings from the students!

Jesús Pineda and Ann Tarrant (instructors)

[Photo] Caption: A sunny 3-hour boat ride to the island (Photo by J. Pineda).

Heading: 10 JANUARY 2013 – EMILYSub heading: Mangroves, Corals, and Fish – Oh, my!

Today was our first full day at the Liquid Jungle Lab in Panama. We awoke this morning to find lizards, beetles, giant butterflies, and the occasional iguana running around the lab and its surroundings. We started the work for the day with the rollercoaster ride of traveling on the little golf carts around the island. These careening carts then went to the marina, where we hopped on a boat to go out to a nearby island to collect barnacles from the mangroves.

The crew on the boat going down the tidal inlet. Everyone took a break from our extensive sampling to smile.

Why were we traveling all this way to look at mangroves? Mangroves are really funky trees that live in the water much of the time. They look like they are on stilts; instead of having roots that go into the ground, they have these long, spindly roots that they send down—sometimes meters—into the water and eventually to the ground (well some do; some have roots that stick up into the air or that look like the buttresses of old cathedrals). Barnacles, which are relatives of clams and oysters, then colonize some of these roots. We were collecting them to find out about their reproductive cycle, which we hypothesize is really tightly linked with the tides, since they spend so much time above the water. After sloshing around in the mangrove for a while, we got back in the boat and did some more sampling from the boat. We took temperature and salinity measurements at different locations to determine where the water had come from. We saw some cool signatures (no pun intended; the water actually was pretty cold too) of freshwater.

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Mangrove trees with roots hanging down (in the foreground). Katie nestled herself into the branches for some extra intensive sampling. Picture courtesy of Melissa Moulton.

After our mangrove expedition we came back for lunch and an afternoon of snorkeling. Not to knock the mangroves, but the snorkeling was far more exciting. Corals are one of the systems we are really interested in studying while we are here. The coral reefs in Panama are unique in that they are really stressed by temperature extremes, salinity, and nutrient loading, among other things. Because this provides us with insight into how corals might respond to climate change, this is a great location to study. However, despite the stressful conditions, there are still some really spectacular corals here.

But first, we had to find them. Looking for corals underwater is kind of weird; you have a limited range of vision in the water, so you could be 10 feet away from a coral and not know until you are on top of it; this made for exciting surprises. At first, I didn’t see any and was getting discouraged, but my discouragement was short lived. We saw several types—branching and massive—and they were surrounded by colorful entourages of fish. Some corals looked like giant exposed brains sitting at the bottom of the ocean, while others looked like tiny, fragile fingers reaching for the sky. Sometimes they were alone on the seafloor, other times they covered massive expanses.

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A partially bleached coral. Bleaching is a sign of stress in corals; they expel their symbiotic algae that help feed them. Photo courtesy of Ben Jones.

The fish were my favorite part of snorkeling. They came is many shapes and sizes; long and skinny, pancake flat, balloon shaped and covered in spines, and everything in between. They were big and small, alone and in schools. One type, a small bumble-bee colored fish, liked to school with us as we were snorkeling, apparently using us as a sort of escort to avoid predation by larger fish.

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One of the schooling fish that accompanied us. I named this little guy Gustav; he swam with me for about 10 minutes. Photo courtesy of Ben Jones.

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A porcupine-fish swimming near some corals. Photo courtesy of Ben Jones.

Overall, it was a very exciting journey under the sea and I cannot wait to dive back in and meet more colorful friends.

Heading: 11 JANUARY 2013 – MELISSA

Today was a day of barnacles! Specifically, decades-old barnacle adults living on mangroves, and days-old barnacle larvae riding the tide.  The early-morning trip to collect elderly barnacles (according to Jesus, they can live for many years!) was Emily Moberg’s idea. She wants to test a hypothesis about whether barnacles of a particular species expend their last stores of energy on rampant reproduction.

Barnacles are arthropods, related to crabs and lobsters. They make their home by permanently cementing themselves to things (this one I knew, from scraping off the bottoms of boats, or pressure gauges left in the water too long), and they eat by grabbing things that pass by. And they have a fascinating life cycle, aided by the largest penis to body size ratio in the animal kingdom.

The species of barnacle that Emily is interested in tends to grow on mangrove roots at the elevation of the average mid- to high-tide. This barnacle syncs the release of its larvae with the spring-neap tidal cycle in the hopes that its larvae can ride the big full-moon or new-moon high tides to the highest ground, where they have the best chance of survival. An important caveat is that reproducing every time there’s a full or new moon (every two weeks) uses up too much energy, so this barnacle species has evolved to reproduce on only a fraction of the full/new moons. Emily’s hypothesis is that old barnacles don’t need to worry about saving energy (they’re going to die soon anyway), and so they may reproduce more often. She’s testing this hypothesis by looking at the fraction of old and younger barnacles that are producing larvae during a particular full or new moon.

Today is a new moon, so it is the perfect time to collect barnacles and count their larvae! This morning our boat “El Lobo” dropped us off at the mouth of “la Isleta” (a tidal inlet) at low tide. On foot, we marked some trees with barnacle clusters, and Emily started to collect some barnacle clusters (see Figure 1A) from mangrove roots by scraping off a section of bark, revealing the red tannin-tinted mangrove wood underneath. The tide was starting to rise, and our second project of the day at a nearby estuary required that we delay the rest of the collection for a few hours. By the time we returned, the tide had risen and collection was not so easy (see Figure 1B)! We’re all curious what Emily will find when she dissects the barnacles in lab.

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Figure 1. Barnacle collection. Panel A. Emily marks and labels a tree for collection at low tide, Panel B. Things look pretty different just a few hours later! Jesus volunteers to dangle from branches at high tide to scrape off more barnacles.

In the nearby estuary “Managua”, our task for the day was to measure the incoming tide, and the barnacle larvae it carried with it. We drove up into the estuary, hoping to get to a river at the end of a fork we checked out yesterday, but we were stopped short by a large tree that’d fallen in the way. At first we were bummed, but it turned out this was an interesting site to study: we were in a deep channel (around 2-3 m deep) beside a large shallow flat (from dry to a few cm deep) a couple hundred meters from the mouth of the estuary (Figure 2A). After tying off to a tree, we immediately started taking temperature and salinity measurements, and starting filtering water to collect larvae (see Figure 2B) in order to determine how the concentration of larvae changes during the tidal cycle.

We’re still working on analyzing the data, but our preliminary results show that the barnacle larvae enter the estuary in a wedge of salty water with the incoming tide. The channel was initially filled with fairly cold fresh water at first and flooded with cool salty ocean water as the tide rose. As the tide rose higher, water started to flow across the shallow flat, and was heated by the sun before flowing into the channel. It turned out that the impassable tree was a good platform for our velocity measurement campaign (sticks, a stopwatch, and a measuring tape), which may allow us to estimate the flux of larvae into the estuary, once we finish counting larvae in lab!

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Figure 2. Studying temperature, salinity, and larval concentration on the rising tide at Managua estuary. Panel A. Study site just short of the tree. The boat is in a deep channel, tied to a tree on the edge of a wide shallow flat. Panel B. Jesus and Ben (right) use a portable CTD (conductivity, salinity, temperature profiling gauge), while Katie casinolta loydat joka tilanteeseen sopivan laakkeen: taitopelin himoon blackjackia tai videopokeria, onnenpeliin raaputusarpa, vauhdikkaaseen viihteeseen videohedelmapeli ja supervoiton metsastykseen jackpot-peli. and Hannah use water pumped from near the channel bottom to monitor salinity and collect barnacle larvae to be counted later under a microscope in lab. Panel C. Emily uses a stopwatch to measure how long it takes floating sticks to pass 5 meters downstream.

Heading: 12 January 2013 – HANNAH

Our focus today turned to Panama’s coral reef ecosystems. In order to tackle the task of characterizing the cover and diversity of the organisms living on the ocean floor, our group split into two teams: Team SCUBA (Melissa, Ann, Luis, and myself) and Team Snorkel (Emily, Katie, Ben, Maja, Jesús, and Vicke). While Team Snorkel first headed back out to Isleta to collect more barnacles, Team SCUBA motored out to the island of Coiba – a former penal colony recently transformed into the heart of Panama’s largest marine protected area – to show our permits that would allow us to study the reefs within the marine park. Team SCUBA then ventured about an hour northwest across surprisingly calm seas to the Contreras Islands.

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Coral reef structure and development tend to vary dramatically as the level of wave energy changes, and one of the goals of Team SCUBA was to compare the reefs that live within a high wave energy environment with those that inhabit a calmer, less exposed environment. To this end, our first stop was the wave-battered coast of southern Brincanco Island. After plunging into the water, we were greeted by a swarm of salps and ctenophores, an unusual sighting as these animals are usually only found very far off from land in the open ocean. We descended 50 feet along a rocky wall, and were excited to find that the reef was teeming with large schools of fish. As we swam along the wall, we glimpsed abundant soft corals and sea fans, a spotted eagle ray, moray eels, bumphead parrotfish, and a 6 -foot long grouper that (suspiciously) only Luis was able to see. However, we were equally fascinated by what we didn’t see: while crowded with fish, the exposed reef was largely devoid of very large colonies of hard corals. Forty minutes later, we surfaced from our dive and traveled over to a more sheltered bay on nearby Uvas Island. We immediately noticed differences in the reef community structure between sites: while more depauperate with respect to fish and soft coral, the sheltered bay was inhabited by expansive fields of Pocillopora branching corals.

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We met Team Snorkel at Uva Island, and both the diving and snorkeling teams then endeavored to survey the benthic cover using a series of transect surveys, and we employed two types of transect survey methods to examine and quantify the community structure of the Uvas Island reef. The first method we used was the point transect method, in which we lay down a 50m transect line on the ocean floor. A diver or snorkeler then swam along the length of the transect and recorded the type of cover (branching coral, massive coral, turf algae, macroalgae, crustose coralline algae, rubble, rock, Students should avoid practice permit test that promise classes lasting fewer than three weeks. or sand) underneath the transect tape at each 1m interval. The second method we used to document the benthic cover was a series of photo quadrats. A quadrat is the scientific terminology for what amounts to a 1m by 1m square of PVC pipe that we placed onto the reef at every 5m interval along the transect line. A diver or snorkeler swam directly over each quadrat and took a photo of the benthos contained within its bounds. We then load the photos onto the computer and analyze the series of images in a specialized program to determine what sorts of sessile organisms live on the reef and how many of them there are. We eventually intend to compare these data with transect data collected from other local reef sites to see how coral communities change across a range of environmental conditions.

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Heading: 14 January 2013 – KATIE

We ventured into the heart of the intertidal this morning, braving rocks slippery with algae and at times razor sharp and hot from the sun. One of our goals was to find a species of Panamanian limpet, renowned for its large size. We knew that most intertidal creatures here favor inhabiting crevices and cracks in the rock, sheltering themselves from the harsh conditions in the intertidal zone. Hot temperatures, wave action, and heavy predation make inhabiting the intertidal challenging.

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After locating a few limpets, we decided to see what would happen if we removed them from their crevice, particularly, we tested whether they would be able to return to their home crevice. Labeling them with a nail polish tag on their shells, we lined up several limpets equidistant from a crevice. Within just a little under an hour and a half, three of the nine limpets we had removed made their way back to the original spots along the crevice. The first one made it there in under 45 minutes! The original location of the limpets didn’t seem to affect their ability to find the home crevice since limpets originally from the home crevice and a limpet from another location were all able to reach the crevice.

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We also explored a nearby bat cave. The cave partially floods at high tide but is high enough to allow bats to roost in the ceiling. One of them was surprised by the flash of Jesus’ camera.  Later on, back in the Liquid Jungle Lab, we had an encounter with a different animal. While eating our dinner, a scorpion entered the dining room. Jesus showed his skills in scorpion wrangling as he captured it inside of a box.  Unfortunately, it later escaped during a scorpion anatomy demonstration at the dinner table, soon after which Melissa demonstrated how fast she can jump on top of a chair. Thinking the excitement was over, we retired to the projector room to give class presentations only to encounter two more scorpions during the course of the evening. Hopefully it was a one-night reign of terror that will not be repeated.

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(Editorial Observation:  The entire dining hall was impressed by Jesus and Vicke’s remarkably deft and nimble reflexive motor skills while they intrepidly avoided the lunging advances of the 3-centimeter-long arthropod).

Heading: 15 January 2013 – MAJA

Day 6 began with a sunny morning filled with sounds from the jungle. After an early morning breakfast we headed out to continue exploring the intertidal near Playa Ventana to check on the limpets we tagged yesterday, collect more gastropods for behavioral experiments, and further study this interesting and harsh environment.

We loaded the boat with equipment and made our way to Playa Ventana. We hopped off at a small beach and proceeded to the rocky intertidal. We could hear howler monkeys calling within the island as we began collecting data (figure 1). Hannah, Katie, and Melissa found that the limpets they marked yesterday had largely returned to the nearby crevice. Intrigued we began searching for more limpets and set up a new series of experiments targeted toward identifying the cues limpets might use to direct their movements. Limpets, a group of gastropod mollusks (snails) with a simple conical shell are found in rocky intertidal areas throughout the world. These snails make indentations or “home scars” perfectly formed around their shells where they can happily “sit” during low tide without losing too much water, while at the same time not needing to clamp down tightly to the extremely hot rock.

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Figure 1: Unloading in the rocky intertidal.

While Hannah, Katie, and Melissa delved deeper into limpet behavior, Ben began recording limpet morphometrics (diameter and height) in a deep crevice where these animals had been measured by the 2011 class (figure 2). He is interested in whether the shape of the snails (such as the relationship between height and diameter) changes as the snails grow. We are also curious as to whether the size structure of the population has changed over time, and we will compare our results with data of the population taken in 2011 by the previous JP class. Emily mapped the locations of two species of corals that had managed to grow in the lower intertidal, noting coloration and physical variations that could potentially allow assessment of coral health.

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Figure 2: Hannah, Jesus and Ben preparing to collect data on limpet size and shape.

The Panamanian rocky intertidal is a particularly harsh environment, where the intense sun causes the substrate to reach extreme temperatures. Measurements from the previous day showed tide pool temperatures above 40ºC. And not only do the creatures here need to deal with these physical conditions, but the intertidal is also exposed to high predation as the tide comes in, bringing with it hungry fish. As a result, the western Panamanian intertidal is sparsely populated compared to many temperate and even other tropical areas. The animals that are present, mainly snails, seek refuge in crevices leaving exposed surfaces relatively empty.

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In an attempt to understand some of the processes forming this community, I collected two species of snails to investigate the behavioral responses between them (figure 3). To identify avoidance behavior of the prey species to the predatory species, prey individuals were placed in artificial habitats (aka boxes), with and without a predatory snail to monitor behavior.  As the sun was beginning to bake the dark rocks of the intertidal and us, we retreated to the shade for lunch. After a full morning on the intertidal we headed back to the Liquid Jungle Lab with snails and data to analyze in the lab.

Heading: 16 January 2012 – BEN

Life in paradise is exhausting. For the past week, we have been collecting data on coral reefs, mangroves, and intertidal habitats. In addition to the group projects, we have each been working on an experiment to present at the end of the trip. I spent the morning analyzing allometric measurements of limpets and reflecting on the past week’s experiences. After nearly a week conducting fieldwork in the brutal tropical sun, the comforting glow of a computer screen in shady comfort was a welcome relief from snorkeling. Meanwhile, more adventurous individuals spent the morning conducting transects to quantify substrate type and collecting algae to look for the presence of toxic dinoflagellates at the service marina.

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Picture 1 – Sometimes randomly chosen points in a transect contain unexpected surprises.

As a modeler, I’ve found the process of designing and conducting an experiment in only a few days enlightening. This project is smaller than many of the ones I work on back at WHOI, but is also about a system that is much less familiar to me. Upon returning to the lab to enter data each evening, I notice additional relationships that would be interesting to examine further. My initial plan was to examine the relationship of limpet size to placement relative to the water height, but it was soon apparent that the strongest relationship was between the minimum width of the limpet and its height. I had collected the necessary measurements to observe that, but not to explain why it might be. Tomorrow I’ll be returning to the field to collect more measurements based on what I observed today. For us, the field is a short ride down the hill; scientists who conduct field experiments on larger scales may get only one opportunity to travel to distant field sites and need to plan their collection techniques far more carefully.

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Picture 2 – In the afternoon, we were treated to a refreshing dip in the pool below a waterfall.