By Roos Swart, Dive master @ Dive Friends Bonaire
Every tourist, diver, and snorkeler alike visits Bonaire for the abundance of turtles! Many green sea (Chelonia mydas) and hawksbill turtles (Eretmochelys imbricata) can be found all around the island, and even the loggerheads (Caretta caretta) and leatherbacks (Dermochelys coriacea) are occasionally sighted.
The most abundant species, the green turtle, visits Bonaire for its favorite snack: the seagrass fields in Lac Bay. Their breakfast, lunch, and dinner is, “surprise surprise” called Turtle Grass (Thalassia testudinum) – a lush green grass that can grow up to 30 cm. The fields are perfectly mowed by our visitors. Green turtles are serious gardeners and keep their lawns fresh and perky.
Two years ago, joined a study of these awesome turtles’ grazing habits in Lac Bay. A new seagrass had arrived at Bonaire around 2010. Quite like the arrival of invasive Lionfish to Bonaire, this Halophila stipulacea came by shipping vessels ballast water. It thrived on Bonaire and rapidly spread throughout the bay. Research has been ongoing since 2010 to see if this new seagrass would change marine behavior in Lac.
My friend Irene and I researched grazing behavior over a 4-month period, looking at how abundance of marine life differed between patches of H.stipulacea and Turtle Grass. Every day, we took out kayaks loaded with dive gear, and spent 2-3 hours observing random spots in Lac Bay.
What an adventure! Apart from our research, we had Lionfish in our research cage and saw one of the biggest grey stingrays I have seen on Bonaire! Our research area indicators, wooden sticks with pink duct tape, were stolen by smooth trunkfish that kept following us across the bay. At one moment five trunkfish were following me in a perfect line.
From our research, we concluded that Lac Bay remains an extremely diverse marine habitat. Millions of juveniles safely mature there before finding their way to the reef. However, the new H.stipulacea provides less protection and nutrition for juveniles compared to Turtle Grass, which our turtles still prefer. Unfortunately, the mowed lawns of Turtle Grass are more easily invaded than thick bushes – thus turtle grazing will likely help the invasion of H.stipulacea. The question remains if the Turtle Grass can survive this invasion (click here for the scientific paper).
Visit the turtles
Lac Bay is different from everything on Bonaire. The serenity and food availability keep not only green sea turtles happy but give all turtles a restful place to visit. Luckily for the turtles, diving in Lac Bay is forbidden. However, if you would like to get involved, you can dive Turtle City with East Coast Diving, enjoy snorkeling in the mangroves, sign up for the Turtle Awareness Specialty with Dive Friends, or join monthly lectures and volunteering opportunities with Sea Turtle Conservation Bonaire.