Can we estimate the exposure to river plumes for coastal ecosystems? During my PhD fieldwork I had the opportunity to collaborate with a multidisciplinairy team of hydrologists, physical geologists, modelers, coral reef biologists to study this in East Kalimantan, Indonesia.
Category: Indonesia
-
Fieldwork Derawan 2014 photo series
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 in the 1st week). I also searched from pygmy seahorses, frogfishes and lembeh sea dragons and found them all. Enjoy the photo’s and leave a comment!
-
Green turtles threaten their own food source in MPAs: New paper Proceedings B
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 areas” and download the paper here.
After press coverage of the Associated Press the news has gone viral! see Washington Post, Time and others
-
Time Lapse Derawan
After all those weeks behind the computer I am already longing back to my view from my research base in Derawan, enjoy my time lapse video. Do you see the tide rising?
2 last hours of sun on a typical fieldwork day.
-
Green turtle stuff around Derawan
In total now we captured and measured more than 800 green turtles around Derawan and tagged 500 of them. The WWF guys (Udin, Darjon), some locals (Jeffrey, Tiar) and we catched them using the rodeo technique. This year we recaptured some individuals that we tagged previously in 2009 on Derawan Island. These turtles grew 3-6 cm (curved carapace lenght) or 3-10 kgs. On her first day on Derawan my sister Sabine saw green turtles in all kind of sizes and activities; she saw an female laying eggs, and small hatchlings coming out of their nest and she was my research assistant while cathcing green turtles in the seagrass meadow. Again a lot of pictures, enjoy because this will be the last pictures from the field for a while!
-
Experiment finalized
The last fieldwork of my Phd is finished! While writing this blog post in Dubai on the way back to the Netherlands the dried seagrass samples patiently wait on the seat next of me, together with the other 70kg of equipment where I travel with. The first unofficial results are promising. On the aerial pictures we clearly see different patterns of gaps on the 3 different stations that lie on increasing distance from the beach.
The grazing effect on the seagrass is enormous, which is clear if you remove the cages that kept away the grazing turtles. Seagrass regrows quicker into gaps behind wave barriers. And the effect of waves and grazing seem to differ between the stations, so now it is time to spend some hours analyzing the huge amount of data that we have collected and write the results up.
In these last months we had quite a lot visitors. Research (photo) journalist Hans Wolkers visited a few weeks to write an article about our research here. With his too infected he could not photograph the turtles during his last days so he ended up helping to sort out numerous seagrass samples 🙂 . And we also had family/boy/girlfriends of Iris and Peter and my sister around. it was a lot of fun having him here. Hans, Sara, Sabine, Jelco, Ger thanx a lot for the help!
-
Green turtle foraging in Raja Ampat
Our second destination in our quest to find the green turtle foraging grounds was Raja Ampat. Some of the tracks of the GPS tagged turtles show foraging greens that travel all the way from Raja Ampat to Kalimantan. We were based at Kri with papua diving and did 2 short expeditions; 1 to Batanta & 1 to Wayag – Sayang. We planned our route using the aerial pictures of Max Ammer and the tips of his friendly staff. During the first trip we saw a dugong feeding at dusk on Enhalus leaves in front of the mangroves. The majority of the seagrass meadows were strips of multispecies (incl Enhalus) meadows in front of mangrove lined islands. Because we were the first foreigners to overnight in the village people did not know what to with us and we ended up sleeping in a empty information house on the jetty. In this area the fisherman are mostly Biak people that migrated here some decades ago. The Biak people explained us that green turtles are still hunted because of the tasty meat, in contrast to dugong meat that they did not like too much. Hence not too many foraging turtles, but a very nice trip. Here is a map of our trip and below it, you can see images of the trip.
[simpleviewer gallery_id=”4″]
-
Green turtle Foraging areas in Wakatobi
After spending so much time on Derawan where green turtles are so abundant we wanted to compare Derawan with other foraging grounds in Indonesia. Wakatobi was our first destination. In contrast to nesting sites of which a lot is known. It is unclear where the green turtles forage in Indonesia, so the majority of the time we spend searching for foraging grounds. The local Bajau people spend all their time at sea and were the most helpful in pointing us in the right direction. The Bajau is the same “tribe” that settled in Derawan but in contrast to Derawan they do hunt adult turtles. So the further away from the villages the most likely to find foraging grounds. In Wakatobi, green turtles graze in highest densities on the South reefs; Karang Kapota, Karang Tomia, Karang Koko and Karang Kaledupa, and around the outer Islands were they also nest. Pulau Runduma, Pulau Anono, Maramoho.
Overall we spend our most time looking for the turtles instead of finding them. We did several surveys of seagrass meadows to look for grazing evidence and suitability for grazing. The turtles we found most were Hawksbills and not the Greens we were looking for. But there is some evidence that on the South reefs the densities are far bigger. Time to go back some day. An impression of the conditions can be seen below.
[simpleviewer gallery_id=”2″]
-
Article in Seagrass Watch
I was delighted to be requested to provide an article for Seagrass Watch magazine. The articles is published in the November issue. You can download the issue from their site (my article is on page 6) or download directly from the Seagrass Watch site (big pdf of 22MB). Enjoy the reading! -
The latest experiment on Derawan
Just got back on the mainland. Last month we succesfully set-up a large experiment on Derawan to look at interactive effects of hydrodynamics & turtle grazing on seagrasses. This involved building 30 cages and 15 large underwater wave-bunkers for which we almost used al the sand from the nearby sand spit. To determine the location of the plots we used an unmanned aerial photo plane. A small disaster happened and the plane crashed in the telephone tower, and the plane is now in Switserland for repair. See below for a photo-report of the last month:
