Marjolijn Christianen

Our in-water survey of sea turtles and their habitats in St. Eustatius (a.k.a. “Statia”) was very successful. We aimed to collect data to analyse the habitat use and population connectivity of green and hawksbill turtles as part of a larger NWO research program encompassing the 6 Dutch Caribbean Islands. Together with STENAPA (National Park authority of St Eustatius) and volunteers, and support [...]

Based on the monitoring data on nesting turtles that Jessica Berkel and her team at STENAPA are collecting we were able to predict the turtle’s return to the beaches. For this we used the inter-nesting durations of the first green turtles tracks that were reported for Zeelandia beach, St. Eustatius. Equipped with a turtle box, satellite transmitters, our red [...]

During our fieldwork on St. Eustatius. Laurent helped as a volunteer to catch turtles. He also made some really nice video footage while free diving. His guest post: “Being a volunteer in a scientific mission is very simple : You just have to listen to the Project Leader, and you have to be available anytime, [...]

Sea turtle sex is not determined at the time of fertilization like in humans, it is set by the temperature level during nest incubation. Recently for some small island rookeries througout the Caribbean researchers reported a shift towards a more female dominated hatchlings/populations as nest temperatures slightly increased in these areas (warmer beaches result in female turtles). At St. [...]

Lisa Becking (Wageningen University and IMARES) and I, together with Sea Turtle Conservation Bonaire (STCB) ; Mabel Nava, Sue Willis and Robert van Dam have shown in a recent publication that sea turtles who breed in Bonaire, Caribbean Netherlands, migrate great distances of up to 3500km to reach their foraging grounds across the Caribbean in 10 different countries. [...]

Bon dia! My name is Moniek and as an Ecology and Evolution student at the University of Groningen I have been doing fieldwork on Bonaire for my MSc internship. Most importantly I have been continuing the turtle exclusion experiment in Lac Bay; going out with a kayak and diving gear to measure and/or clean at [...]

Grazing is an important driver of ecosystem functioning! Not only in seagrass ecosystems :). This paper is a result of a very nice collaboration with Liesbeth Bakker and other colleagues working on herbivory in other ecosystems. Paper highlights: In this paper we show that herbivores provide strong top-down regulation on freshwater macrophytes and seagrasses. Their effects are [...]

Today 2 papers of our group were published online! This papers are the result of a successful collaboration between the University of Groningen, NIOZ and Radboud University, The Netherlands The first study by Els van der Zee et al. demonstrates that food web structure and complexity can be fundamentally shaped by habitat-modifying species.  This works through facilitation rather than trophic interactions [...]

Within the Dutch Caribbean, green and hawksbill turtle rookeries and foraging grounds are found. Green and hawksbill turtles have been decimated by human exploitation and habitat degradation, calling for knowledge of population structure and demographic history. Here we investigate migration patterns in these highly migratory species and evaluate current population status. In other words: How many turtles were there [...]

Last week we* successfully placed a satellite transmitter on a big green turtle female after she nested at Little Curacao’s turtle beach. The signals of the ARGOS satellite are updated hourly and I am very happy to report that this female is swimming very fast in the direction of Nicaragua 1050km in the first 10 [...]

I am Fee, the first master student who will monitor the exclusion cages in Lac Bay on Bonaire for three months. I arrived two weeks ago. My main research questions are: How does turtle grazing affect the productivity of and competition between the native T. testudinum and invasive H. stipulacea in Lac Bay, and what [...]

4 sub-adult green turtles that we caught in Lac Bay are now equipped with satellite transmitters to study their movements and use of the seagrass meadows, (see more photos below). The greens that forage in the shallow Lac Bay area are typically sub-adults. We selected some of the biggest turtles that forage here, to not [...]

Two weeks ago we arrived on Bonaire. Since then we worked non-stop and we made great progress! The first thing we did was to set up a turtle exclosure experiment on the seagrass beds in Lac Bay, after Funchi (STCB) and Sabine Engel (STINAPA) kindly showed us all the suitable seagrass areas. The native dominant [...]

I am very excited to finally start our fieldwork on sea turtles and seagrass in the Bonaire, Aruba and Curacao! What started as a proposal (initiated by Lisa Becking and me) in August 2013, finally resulted in a research project May 2015 entitled  “Ecology and conservation of Green and Hawksbill turtles in the Dutch Caribbean”. [...]

Who eats who in the Wadden Sea? We collected 12000 samples in one of the largest dbases of stable isotope samples. Using these samples we found that the energy in the Wadden Sea (primary production) is mainly provided by the production of benthic algae (diatoms) on the tidal flats. Papers about this are underway but [...]

The Wadden Natuur kaart (Wadden Sea Nature Map) is now online: this is one of the publications of the Waddensleutels project on which I worked in the last 2+years. You should definitively explore and test it. For example; activate the benthos hotspot layer (upper left) and see which areas are most interesting as foraging areas for [...]

The Waddensleutels project finished 16 april 2015 with a symposium in Leeuwarden, and with that also my 1st post-doc project.  Topics here were: Which measures should we take to increase the area of musselbeds in the Dutch Wadden Sea & what is the current foodweb stucture and state (and how is this affected by the [...]

I had the opportunity to go back to Derawan for 3 more weeks of fieldwork, thanks to the Schure Beijerink Popping foundation. I gathered samples for food web analysis, checked the current turtle density and seagrass biomass, recaptured green turtles and made a new series of aerial photographs with a kite (with super assistant Sipke [...]

Our new paper is out in Proceedings of the Royal Society B! Green turtle populations have expanded so much in Indonesia’s east coast islands marine protected areas that they are adopting new feeding habits, degrading the ecosystem and threatening their own conservation. Read more about  “Habitat collapse due to overgrazing threatens turtle conservation in marine protected [...]

This summer we (the Waddensleutels team) visited all dutch Wadden Islands to collect samples for food web comparisons between mussel beds and surrounding habitats. It was a very successful operation. We collected around 1800 samples of organism that are now going to be analyzed for stable isotopes at the NIOZ, Texel. Sampling involved fishing with [...]