To pick up where I left off, after the Great Vermetid Surveys of 2012 (see previous posts), for the past few weeks I have been focusing my efforts on deploying several field experiments out here on the island of Moorea in French Polynesia. These experiments are part of my dissertation research, and this summer in particular, I am looking at the effects of coral reef habitat loss and isolation as well as nutrient pollution on herbivory. Herbivory is essential on coral reefs, because it helps to control the abundance algae, which can outcompete coral and take over reefs, with drastic ecological consequences (simply put, from teeming coral reefs to slime).

One of our first focuses is to look at the relationship between distance from the reef and herbivory. The assumption is that herbivorous fish are scared to travel across open sand flat to find food, because they don’t want to get gobbled up by a predator or speared by a fisherman. This ‘fear effect’ could have very important implications for reef habitat loss and fragmentation that result from natural and human-driven processes. So, for one of our experiments, we have created an “algae hors d’oeuvre platter” (i.e., a cinder block with a variety of algae tied to it), which we place at 5 different distances from the reef and video tape what happens. This approach allows us not only to get a sense of how herbivory may change with distance but also tells us who is doing the eating—what species, what size, how much eating etc. After a few weeks of running these trials, we are starting to get some interesting results and also some surprises. The best so far happened two days ago, when we returned to our cameras after leaving them for 4 hours. This time, we noticed that one of the far cameras (30 meters from the reef) was now facing the sky instead of the algae hors d’oeuvre platter. This was upsetting, because it meant that we did not get the full 4 hour observation period for that unit, but we were happy that the camera was still there. We assumed that the current, which had picked up that afternoon, could have been the culprit, but fortunately the camera was still recording when we arrived, so we knew that whatever caused the camera to move was caught on video. So, we took the camera back to the lab to analyze the video. This is what we saw (turn up your volume if you can when you watch this for the full effect):

SPOILER ALERT BELOW.

The hungry animal featured in the video is called a triggerfish, a Yellowmargin triggerfish to be exact, and it primarily eats sea urchins and shellfish (hence the impressive/grotesque teeth). As evidenced by the video, these guys can be quite aggressive and bitey—lucky for me, the GoPro camera housing stood up to the challenge, except for a bit of chipped plastic. On a side note, a close but much, much larger relative of the Yellowmargin triggerfish, the aptly named Titan triggerfish (measuring nearly 3 ft long), attacked me during a dive in January.

Stock photo of a Titan triggerfish with his/her gnarly teeth showing. These things can BITE!

Fortunately, the biting was restricted to my fins, but the encounter was a stressful one to say the least.

The next day (yesterday), we deployed the video cameras again, only this time to capture a different experiment. In this experiment, we are looking at the effects of sedimentation and vermetid snails on coral growth. Sedimentation is a big problem for coral reefs around the world, because sediment can smother corals, and increased coastal development tends to lead to increased runoff and sedimentation of nearshore marine ecosystems (like coral reefs, seagrass meadows, and kelp forests). We also know that vermetid snails that use mucus nets to feed can also be quite detrimental to corals (see previous posts for more info). So, we wanted to see how these two stressors together may affect corals—for example, maybe sediment is actually pulled off of the coral by the vermetid mucus net, or, alternatively, maybe the mucus net, being sticky as it is, allows sediment to better adhere to the coral surface, causing more damage. These are the hypotheses we are testing, and to help us understand what exactly is going on, we have been shooting photos of each coral at 10-second intervals throughout the day. Yesterday was one of these days, so we again left our GoPro cameras out in the field for several hours. Upon our return to retrieve the cameras just before dusk, my assistant Julie noticed that one of the cameras was missing from the 5 lb dive weight to which we’d had it cable tied. The cable tie was mangled. She also noticed a very large octopus atop the reef next to where the camera was. When she called me over, I approached the octopus. Yes…he stole our GoPro:

Fortunately, we got the camera back in one piece, and even more fortunately, the camera was snapping photos throughout the ordeal! So we got some pretty interesting shots:

The first is the standard, (now considered boring) shot of our experiment coral:

One of our experiment corals, photographed for a time-lapse to look at sediment and vermetid mucus effects

But then, our Hero is kidnapped!

I particularly like this one, where the octopus seems to want to give back to our research a bit, by shooting his own photo of our experimental coral.

And plunged into darkness…

At this point, it seems the octopus took the camera down into his/her den within the coral. Thank goodness s/he wasn’t down there when we arrived!

And finally rescued. Woohoo!

What a wild couple of days it has been. I can’t wait to see what else these cameras capture over the next two months…

Thanks for reading/watching! More soon.

Mike

Moorea: Where I am fortunate enough to be spending my summers.

Our third and final island to survey for vermetids (snails that are linked to coral die off in French Polynesia—read more in my previous post) was our home island: Moorea (pictured above). We surveyed each shoreline—north, east and west, over three days. To give you a better idea of what our surveys are like, I’ve uploaded a video clip of one of our dives off the west coast (This time we were diving in Haapiti, another famous surf spot, as evidenced by the surge in the video. BUT, It did not compare to the big wave in my previous post…) :

As seen in the video, we place quadrats (square metal frames) on top of the reef at different locations and count up the number and species of vermetids as well as branching corals  that fall within the square.  By doing this many, many times in many locations (and across islands), we are able to get a better sense of vermetid distribution patterns and how these patterns may be linked to potential drivers, such as human development.

Fortunately, the weather cooperated nicely throughout all our inter-island surveys, aside from a little rain. But who cares about rain when you’re submerged all day anyway?

Survey bros Snout (left) and Adrian (right) during a soggy surface interval between dives. Spirits remain supercharged!

In the end, we completed all of the work we set out to accomplish and got to experience some epic scenery while island hopping. The video below features our triumphant boat ride home along the north shore of Moorea after completing our final site survey–kite surfing,  trans-Pacific yachts and a lush-green mountainous backdrop are all regular sights on the way to/from work out here:

The inter-island vermetid survey is now complete for this summer. We had a great time and a great team, and I look forward to what these data can tell us about vermetids and how we might better understand their role on the reef. Now, and for the rest of the summer, I will be conducting experiments for my dissertation (read more about the topic here). Stay tuned for more South Pacific island adventures for science!

Mike

At 5 am Monday morning, we set off under cover of darkness to travel across 60 miles of open ocean on a 26 ft boat to reach the remote Polynesian island of Maiao.

Our view of Moorea in the early morning hours, on our way to Maiao.

………..

To give you the inside scoop on this expedition, Maiao is the second of three islands that we are surveying for vermetids—small snails that live on top of corals and are linked to coral die off (see previous post). In this study, we aim to see whether the densities of vermetids differ among reefs that surround three different islands, with hopes to better understand what is causing vermetid populations to flourish and, in turn, kill off corals. Some data suggest that vermetids may thrive under high nutrient conditions, due to higher food availability. Because human development leads to nutrient pollution, it is possible that human population density is the key to vermetid outbreaks that have recently plagued areas of French Polynesia. As such, the three islands we will survey are subjected to a range of human development, from high: Tahiti, medium: Moorea, and finally low (Maiao). Maiao is inhabited by less than 300 people.

………..

Shortly before arriving at Maiao, we realized that we didn’t have enough fuel to complete the trip back home to Moorea, which was planned for the end of the afternoon. Our captain, Jacques, came up with the McGyver-like contingency plan to have another station boat (this one even smaller) meet us halfway on the return to bring us more fuel–that is, wherever our boat ran out of fuel somewhere between the two islands. This was unsettling for the group, but we saw no alternatives aside from sleeping on Maiao, which would make us lose a day of field work. So, we went along with it, hoping for the best…

When we arrived at Maiao, we were greeted by an unexpected procession. The Mayor of the island, along with some of his family, met us at the one dock (and the one sign of human settlement) on the island’s perimeter. They seemed very excited to see us–men, women, children—a little over a dozen in all. Some of them were especially interested in checking out our scuba gear on our boat. They also brought an impressive brunch, which they setup with some patio furniture. Tuna steaks, fa fa snails (snail salad), fresh coconut milk, tea and firi firi (donut-like pastries) were served in Tahitian portions (large piles). We were happy to oblige and put an impressive dent in the food pile before thanking our generous hosts profusely, grabbing a quick photo with the mayor to commemorate the unique encounter (below), and heading off into the rising sun to collect some data!

Hanging with the Mayor of Maiao (in green front and center) and his family, along with Snout and Jeff to my left (coworkers from New Zealand), and Adrian (American colleague, who took the photo).

Our work went pretty smoothely, aside from a challenging tidal surge and a kamikaze-like swim into the reef lagoon over the reef crest, which almost claimed our lives (the reef crest is the part of the reef where the waves break–BIG waves in some cases–an important protective service that reefs provide to coastlines around the world). Interestingly, the reef, as well as the vermetid population, seemed to exhibit some clear differences to Moorea, which could yield some interesting results at the conclusion of our study. We sampled from the perimeter of the entire island, which made for some cool sights—the island appeared completely untouched from the reef’s edge and from the shore.

Maiao from one of the forereef locations where we were diving for our sampling. Click to enlarge!

Maiao’s stretch of untouched beach, just west of the boat dock–the one sign of human life on the coast.

Just before calling an end to our work day and making the arduous, journey back to Moorea, which included the super-risky fuel exchange, we received a call from the Mayor offering us fuel to complete our return. Thank goodness! We obviously took him up on the thoughtful offer, and once fueled, headed off into the sunset with some nice data and an unforgettable memory.

Next on the island-hopping list: Tahiti. Stay tuned…

Mike