In January, National Geographic Indonesia published a very nice map about the important habitats for the green turtles in the Derawan Archipelago. See low resolution map below. The Editor in chief visited Derawan and interviewed all goverment NGO’s and researchers (me) having something to do with the green turtles in November and he made a good review about the most important turtle issues. Below the map you can find the text were I was quoted.
Unfortunately just after NG left, another big threat to the turtles in the area became clear. Over 100 turtles got stuck in a >1000m net in front of Maratua Island, clearly set out to catch turtles specifically. You can read more in the article of Frank Zindel. The last 4 years a turtle net (big mesh sized) was found on 4 occasions in this area and killed a hudge number of turtles: ±150 dead turtles in 2005, ±400 in 2007, ±100 november 2009, ±15 December 2009 and the Chinese illegal poaching can still continue until the local authorities have enough resources to patrol regularly in the area.
Translated (thanks google translate) from the text of NG Januari.…”Marjolijn christianen, a Dutch researcher who pursues seagrass in waters off the island, conveys her worries about many sea turtles that are run over by fast speedboats in the shallow water area were the banana boat attracks a lot of tourists. Turtle carapaces are scratched when they are hit by the engine propeller of the fast speed boat. This propellor also damaged seagrass beds. Another threat, which is huge but more subtle, is pollution from the mainland and from the island Derawan itself. “I study the interaction of nutrients from river pollution and household waste on seagrass beds and the feeding relationship with the green turtle” Marjolijn explaines. Pollutants bring nutrients that feed algae. The more algae that grow in shallow water prevent sunlight to reach the seagrass, so its growth is reduced. Seagrass is a staple food of sea turtles and may decline as a result of the pollution, seagrass and thus turtles are estimated to continue decreasing.”…..
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.
After 1 week of preparation the penyu team arrived at Derawan. Here Ibu Heldi invested my last payments in improving her place. Now it feels even more like home and our own research station even!
In the week that my supervisors are here we revisited the seagrass meadows that they sampled in 2003. Sampling the same sites from the river to the open see we saw a lot of variation in species composition, algea cover, morphology. At the moment that I write this article Leon Lamers is travelling back to Nijmegen with +/- 10kg of dried seagras, sea water, and syringes with gas. Sjoerd will analyse the samples when he is back in february, we are looking forward to the results of the plant-nutrient analysis.
Check the photos to get an impression! And leave a comment, so that we also get some information back
We can also receive old fashioned post. Here is the adress:
Nama: Sekni AS
Untuk Ibu Marjolijn tinggal di Ibu Heldi Wisma Aditya Di Derawan
JL H.ISA III 66 Mardatillah No. 16 Rt / Rw 10
Kode pos 77311
Tanjung Redeb, Kab. Berau
Propinsi Kalimantan Timur, Indonesia
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.
In august I visited Maratua for some measurements on the seagrass there. When I arrived the water was too high to work; time for some exploring! So I asked a man from the village about the marine lakes there. Off we went, through palm forests and mangroves with a “parang” cutting out our way. And then we reached this marine lake. The jellyfish were a lot smaller then those of Kakaban lake and the other more famous lake of Maratua. And when I reached the opposite of the lake I found … Enhalusacoroides!! I still have to check the literature but it’s very interesting to find this species here! This marine lake has a lower salinity (26-28‰) than the surrounding ocean (33%-34%) because of the filtering effect of the coral and years of dilution by rainwater. I know seagrass can cope a large range of abiotic factors but finding this species here suprised me. Do you know more about this, and have you seen this somewhere else? I’m pleased to receive your comment! The lake was also very turbid at the shore as you can see on this pictures (click for more pics).
After performing the same experiment with transported Thalassia hemprichiilast year I wanted to test the same treatments in the field. So after some creative thinking I came up with this set-up (click for more pics):
I’m (amongs others) testing if high ammonia concentrations could cause troubles to seagrass.
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.
Recent Comments