Seagrass Systems Under Nutrient Loads and Grazing

From Christmas there wasn’t time to travel to the internetcafe on the mainland to update this blog because we preferred to do some extra experiments J instead of spending 2 day travelling. Now, I just arrived back home and I will give you a comprehensive update of the work of Sjoerd, Sarah and me the last 2,5 months.

Gap-regrowth: We measured the regrowth of the seagrass into the empty sand area (mimicking the situation after turtle grazing) every 2 weeks. High waves caused a lot of sand dunes to walk through the area but they luckily had a minor effect on the regrowth. Though these waves caused the cage to crash critically just 2 weeks before the end of the experiment. Our Derawanese friends helped us out by pulling the cage up with ropes behind their speedboats!

Macrofauna: Dominik Kneer and Arie Vonk visited to sample the fauna on, and in- between the roots of the seagrasses on Derawan. Because the seagrasses here are so different; small plants and dominance of 1 species (Halodule uninervis) instead of a multispecies meadow with large plants, we expect a lot of differences with Dominik’s research site Barang Lompo, Spermonde Archipelo, Sulawesi. It was good fun accompanied by some nice stinky samples!

Turtle kiting: After 2,5 months of light breezes we almost forgot about our kite. But then halfway January there was enough wind for our kite and I photographed (time-lapsed) turtles in a grid on the seagrass while grazing. Now I have to develop a script to automatically process these 1000’s of pictures. So now it is time for a year in the office to analyse this gigantic amount of data into articles!

Left: Sarah ready to harvest seagrasses from our cage. Right; our hosts and great cooks on Derawan Islands.

We explored the southern islands of the Berau Archipelago, Bilangbilangan, Blambangan and Mataha in search of more foraging areas for the green turtle.  In January 2010 National geographic Indonesia published a map + article on the green turtle in Berau. Turtle foundation is conserving the nesting beaches on these Islands and has posts on Bilangbilangan and Mataha were some very commited staff guards the turtle eggs. And you directly see the effect: On the Island without conservation posts eggs are stolen. A boat with poachers was directly fleeing when we arrived at Blambangan with our speedboat. This is the picture of a fresh egg forgotten by poachers that dug out the rest of the nest.

While egg harvesting is forbidden for some years in Indonesia local government creates their own rules and along the roadside of Samarinda and even on the local market of Berau you can still buy the ping-pong-ball-shaped green turtle eggs. Eggs are most likely from the few islands without conservation posts like Blambangan.

In the rainy season and the rest of the northeastern monsoon the number of females per night laying eggs is less but on the islands we visited it wasn’t difficult to spot them (there were still 7 that night) and in the afternoon we also encountered mysterious spots of moving sand after which more than 100 tukik per nest emerged. It is like Kill Bill 100-fold!

Like all organisms turtles development of hatchlings also sometimes fails. Here the TF guards showed us a tukik (Indonesian for hatchling) without legs and a hatchling with 2 heads.

When we arrived back we want to measure the population size of the green turtles in the area so we recaptured a lot of green turtles by rodeo method to check for tags.

All with help of Dodi, Jeffrey, Tiar and Darjon, who normally also help WWF/TNC. We used waterproof marker to prevent recapturing the same turtle. 1 of the turtles missed part of his front flipper (@pic right below). We also encountered a lot of turtles with cuts in their carapace (below-left), presumably caused by speeding speedboats around the island. If you see a turtle with tagnr 2722.. – 2725.. email me!

The special thing about this research area (Derawan, Indonesia) is the high density of Green turtles (Bokok in bahasa Bajau, the local language). Last year we found 1 turtle per 30 square meters of seagrass. However on the different feeding grounds densities differ, possibly regulated by the availability of food, seagrass. In the last 2 weeks we visited 3 islands Derawan, Maratua and Pulau Panjang (east-Kalimantan, Indonesia) and we catched, measured, painted and tagged 300 turtles. 

The sizes (of the carapace) ranged from 40 to 112 cm, the weight from 8 to 116 kg’s. The most of them were catched in nets by a team of us; Sarah, Sjoerd and me, and 4 enthusiastic Derawanese locals in a fishermen’s boat. For 3 days the local assistants of Pak Rusli from the WWF-TNC joint program Berau catched extra turtles with the rodeo method by jumping from a speedboat. The coming month we will try to spot our tagged/painted turtles back, so that we can learn about their movement and the population size. In addition we are also cooperating with Udayana University to study the population genetics of these turtles.

Transport of the turtle from the net – boat by kano.

Even in heavy rain the crew is searching for turtles. See here the net of 100 meters in front of the village of Payung Payung, Maratua.

*Next fieldwork period from Augustus 2009*

Are you looking for a research project for your MSc specialisation? AND:

• Interested in Marine Ecology and Ecosystem wide processes?
• Would like to participate in fieldwork in the Derawan Archipelago, East Kalimantan, Indonesia
• Would like to gain experience in fieldwork in an experimental setting and in chemical laboratory technique
• Highly motivated & enjoys working in field and lab?
• Interested in being a co-author on a scientific paper?

Then please send a 1-2 page CV and a letter with your motivation to me: m.christianen@science.ru.nl

Background
The objective of our project:

• We wish to address the possible shifting states of seagrass in relation to eutrophication and turtle grazing, using field experiments in the Derawan Archipelago, Kalimantan, Indonesia.
• In parallel, we wish to obtain insight in the variation in production and community composition of seagrass assemblages between sites at diffent distance to the river and relate this variation to spatial and environmental variables.

Most field experiments will be carried out in the coastal zones of the Berau and Mahakam rivers, East-Kalimantan, Indonesia. Ecosystems states (e.g. eutrofication, turtle grazing) and possible shifts between them will be provoked in a series of experiments involving turtle exclosures, turtle grazing mimicking and nutrient enrichments, both in the field and in the lab. The research will be carried by Radboud University Nijmegen (The Netherlands) in close cooperation with the Indonesian Institute of Science (LIPI, Indonesia) and the Netherlands Institute of Ecology in Yerseke.

What you will do:
Participate in fieldwork and exclosure-experiments. Participate in lab-work, collecting toxicity and biogeochemical data. We can discuss the details of the internship to create an exciting project that encompasses both your research interests and the goals of our project.
Your project could start in the middle of 2009, with fieldwork (3-6 months) starting from beginning of August 2009. Due to application deadlines of funding (and visa preparations) It is advised to start early < 6 month before the start of your project with the preparations.

In Dutch:
Studenten gezocht: Stage Mariene Ecologie Indonesie,
Als je op zoek bent naar een buitenlandse stage voor je master in Mariene Ecologie / Biologie lees dan bovenstaande beschrijving even door. Ik ben op zoek naar studenten die bereid zijn om voor hun master project ook veldwerk uit te voeren in het buitenland. Indonesie op het eiland Kalimantan voor verschillende maanden. Heb je interesse, neem dan contact met me op.

Time is flying. The enclosure experiment is finished and Laura and Madelon left for their holidays. Time for me to visit the civilized world and put some pictures on the internet. It isn’t very structured but that is because only emailing this pictures costed me 1 1/2 a small discription can be found next to the pictures. The last 3 weeks will be spend on performing an NH4 toxicity experiment and a comparison of seagrass productivity at an island close to the river compared to an island far from the river.

Time for a presentatie for WWF, TNC and the local goverment in Berau about our research in Derawan. After a morning with presentations (Nina thanks for the translation in Bahasa Indonesia) and a very nice discussion it was time for a afternoon of jungle. We rented a boat and drove 0,5 hours from Berau to a small river where it was seeming with monkeys. The “Orang Belanda” Proboscis monkey was there and 4 other species. Not al pictures are sharp but more for the archives

Two months into my first research period I would like to update you on my progress. Because it’s almost impossible to post from my research location on Derawan I will show a compilation of photo’s. When I will be back in the Netherlands I will elaborate some more on the specific experiments. Click on the photo for all the research photo’s.

In the first week at Derawan I saw so many turtles, therefore a post about the “production of new turtles”. Yesterday night I saw 4 turtles (Chelonia mydas) crawling on the beach to search for a suitable site to lay their eggs above the high tide line.

She digged out a large hole in the surface of the beach using a swimming movement of her front flippers, creating the “body pit”. After ten minutes or more, actively throwing sand behind her, she beginned digging with her hind limbs, excavating the egg chamber of about 60 cm deep. Without pausing she continued laying 90 ‘ping-pong-sized-eggs’ (While the eggs are being deposited into the egg chamber, they can tolerate bouncing, rolling, tumbling or handling, but about two hours after being laid, the embryo will resume development, and may be killed by a simple roll of the egg.) Ferry from the WWF digged up the eggs to protect them from poachers. Now we have to wait 45-70 days for the small Tukik (turtle hatchling in Bahasa Indonesia) to hatch. Higher temperatures produce more females and result in shorter incubation periods. At Derawan Ferry will check development of the nests so that he can digg the eggs out and release the small flippering friends before poachers or predators find them.
After nesting, the female went back to the coral reef to rest and complete the next clutch of eggs. They are known to mainly rely on their stored fat reserved while resting and completing the next clutch of eggs. She can lay several clutches of eggs at approximately two-week intervals before finally migrating back to her feeding ground. We are still in doubt if the mother turtles are the same ones grazing on the seagrass fields in front of Derawan at daytime, or if they only visit this Island to lay their eggs and travel back to their feeding ground.

The first days I’m testing the set-up of my experiment, I’m snorkeling 4 hours a day to check out the seagrass and the turtles here (also found dugong grazing trails!), and I’m talking to officials here and setting up logistics at this island. The 21th of May my supervisors and students are arriving so I will travel back to Balikpapan to pick them up and do some measurements at Balikpapan bay.

At this moment I’m staying at Derawan Beach Cafe. It’s a convenient place with very kind people, good food (with vegetables, and nasi goreng as breakfast) 24hrs power, airco and a toilet to sit on. The only question is if I can stay here until september because the 300.000rp per night.

For some more pictures click here!