Wednesday, May 18, 2016

Sea turtles of Martinique and Guadeloupe

Today we turn over the blog to Caitlyn Webster, who helped PhD student Beth Whitman with her research on sea turtles off the Caribbean islands of Martinique and Guadeloupe!  Coming up soon will be updates on Global FinPrint from Guadeloupe, Martinique and Madagascar!

The turtles of Martinique and Guadeloupe

Caitlyn diving down to survey seagrass
After landing in the tropical paradise of Martinique, Beth Whitman, lab researcher Dr. Jeremy Kiska, and I set out to elucidate the ecological significance of sea turtle grazing on the spread of an invasive seagrass,Halophila stipulacea. We hit the ground running on the first day as we met with local collaborators, including the ever helpful and lovely, Emilie Dumont-Dayot (Coordinater at Rêseau Tortues Marines Martinique), in order to develop an idea of the general seagrass composition within potential field sites. We were quite fortuitous to have boat time, donated by the national park service, for the day to conduct our initial surveys within Grande Anse and to visit the potential sites of Andse du Bourge and Petite Anse. For our surveys we dropped quadrats from the surface, while freediving Beth and I plunged into the pleasant waters within Grand Anse to quantify the seagrass community composition and abundance. We even managed to spot a few turtles when our heads weren’t buried in the seagrass! That evening we returned, a bit sun kissed, and began entering data, running power analyses, and designing our experimental game plan for the next weeks on island. 

In the morning we tested the settings of the DJI Phantom 3 quadcopter/drone over land before releasing it to the elements over an open body of water. France requires fashionable parameters for flight! 

Grand Anse in Martinique.  Beth Whitman (with drone), Dr. Jeremy Kiszka, and Caitlyn Webster are dressed in the required safety gear and the landing pad is roped off!

We launched the drone over Grand Anse for a test flight in hopes of using the aerial vantage point to survey turtle densities and map seagrass cover within the bay. Although the drone took impressive aerial footage, the glare, rippling of the water's surface, and water depth made it difficult to detect turtles while flying high enough to avoid collision with the many boat masts scattered throughout the bay. Admitting this is a fantastic technology, but more applicable to shallow, mast-free environments, we opted for plan B: in-water snorkel surveys of turtle abundance. Over the course of the next week in Martinique we conducted 60 of these surveys along 300-600m long transects, and then 30 more in Guadeloupe! During our snorkel surveys we found that most of the moorings in Grand Anse were broken, and unusable for the many pleasure yachts that inevitably anchored in the seagrass and/or sand throughout the bay. These anchors leave large scars and leaving open areas for the invasive seagrass Halophila stipulacea and dispurse fragments of the seagrass contributing to it’s spread. During our snorkel transects we dodged boats (usually successfully) while recording turtle locations, behaviors and food availability. Some nights we asked ourselves, “Is 7PM too early for bed”? However, our hard work paid off! Surveying until the very morning of our departure, we completed 60 transects throughout Grande Anse. 

Green turtle grazing in a mixed bed of native and invasive seagrass
We also collected focal follow video footage of individual turtles. Armed with GoPros attached to extendable poles and GPSs we filmed foraging green turtles to investigate the turtle behavior and grazing preferences. For the most part turtles proved unperturbed by our presence. As the turtles foraged below, we could often hear the crisp crunching of the naturally occurring seagrass, Syringodium filiforme

Our local collaborator, Emilie, agreed to continue focal follows and seagrass collection (for nutrient analysis at FIU) in our absence after showing us a site she has great interest in, Sainte-Anne. The invasion of H. stipulacea in Sainte Anne is not as as great as in Grand Anse, so it will be interesting to see if our pilot surveys detect a significant difference. Also, keep an eye out for Beth and I in the local Martinique newspaper. After catching enough eyes with our bright orange buoys, clipboards, and zinc-oxide caked faces, Emilie coordinated an interview with a journalist about the research that we were conducting. After twelve days 11, we said “Au revoir!” to Martinique and hopped over to our next field site, Malendure, Guadeloupe.

Beth, Emilie and Caitlyn collecting seagrass samples
In Guadeloupe we continued with our surveys in a much smaller bay than Grand Anse. After researching all day, Beth and I were delighted to wash our gear in the convenient river flowing alongside our temporary home thanks to another local collaborator, Gaëlle Vandersarren , grab a daily baguette down the road, and walk the dogs through the mountainous jungle surrounding our accommodations. We joined forces with an avid marine conservationist, Caroline with Association Evasion Tropicale, to begin a valuable collaboration of integrating years of her data with our own. She also agreed to continue focal follows and seagrass collection in our absence. As our trip was coming to a close, Beth had the terrible misfortune of kicking a long-spined urchin (Diadema sp.) as we were, quite literally, hopping between transects in the shallows. Determined and motivated, Beth continued our surveys sans one fin! Serendipitously, Phil Matich (Heithhaus lab alumni and Post-Doc at Sam Houston State University) came to assist us in the field for a few days in between deploying BRUVs and joining the sperm whale team on board the Saravi III. With a fresh set of particularly tall legs, our team produced an impressive amount of seagrass surveys and collections. Beth and I wrapped up all of the field work and data entry with just enough time, and barely enough endurance, to summit a remarkable volcano, La Grande Soufriѐre, on our last day. Thus concludes our “vacation” at the beach in the French Antilles. Stay tuned for updates about Beth’s next turtle endeavors in the Caribbean at her field site in Abaco!
View from the summit (1,467m) of La Grande Soufriere.