LAST Week Eight: Satellites and Seagrass

This week has flown by, with a lot of new and different experiences including putting a satellite tracker on a turtle and an intense three-day seagrass survey.

I started off with a little ‘holiday’, a trip out to Drake Bay on the other side of the peninsula. This is a beautiful little remote bay/small tourist town on the north side of Corcovado National Park. I went there to dive at Cano Island, which I’d heard amazing things about. Unfortunately we had some ‘weather’ come in which churned up the visibility at the first dive site we went too, but the second was amazing with clear water, incredible cliffs and canyons, massive shoals of barracuda, reef sharks, rays, etc. Although unfortunately we didn’t see them in the water there were loads of whales all around the island which made the boat journey fun.


Also, my dive buddy turned out to be a volunteer who is joining for us two weeks! It’s nice to have a volunteer around again, especially for the week we’ve had.

We started by placing a sat-track on a turtle who was being released from rehabilitation. LAST has four trackers that were donated to them, and are trying to place them on reproductive male hawksbills in an attempt to track the mating migration and find the mating ground for this population.

This was the first of the four and the director of the organisation came down to show us all how to apply them. It was a long process (even longer for the poor turtle) but very interesting, and at the end of the day we were able to send him off on his adventures. The shell has to be washed, sanded, and cleaned with acetone (it reminded me quite a lot of patching inflatable boats), then the tracker is attached with epoxy and painted over with antifouling marine paint to prevent algal growth.

All dressed up

There are two sensors that you have to be very careful not to cover. It then pings information at certain intervals when the turtle surfaces, and hopefully the satellite is in a good position at that time to receive the data with some accuracy. It’s a lot of money (about $3000 per tracker, plus a monthly payment to the company to receive the data) for potentially very little reward if the tracker comes off or the antenna is broken, but a very useful tool for sea turtle research if you can do it.

Then we started a seagrass survey, which is ten transects in the gulf with a monitoring point every fifty metres, and takes about three days to complete as it has to be carried out over low tide (and it is exhausting). At each point we took depth, Secchi (a measurement of water clarity), and looked for seagrass. If there was seagrass we had to take a biomass sample, which was a 15cm core into the sediment using a PVC pipe. This is a challenge at depth!

Halodule sp. seagrass

On the 3rd day the researchers from the University of Costa Rica who are carrying out the monitoring joined us and took lots of water samples as well. It was fun to be doing some different, and the whales hanging out in the gulf showed up all three days to give us a little whale watching break. Freediving to take samples while being able to hear whales singing is pretty much exactly how I imagined being a marine biologist when I was ten years old! However, after all that swimming and freediving I was pretty exhausted and glad to be done at the end of the third day.

Unfortunately we discovered that the mangrove nursery had been buried a bit by the tide again, so we had to dig that out and the site of it will probably have to be changed soon. Over just my time at the project there has been a lot of erosion up at the beach there and it will likely soon wash into the river.

One of the RAs, J, is leaving a little earlier so we went out to the beach bar for his last night yesterday which was super fun even if we did stay up way past our 8pm bedtime!

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2 thoughts on “LAST Week Eight: Satellites and Seagrass

  1. Hello Hayley! Really enjoying your stories from Costa Rica, very envious especially as snow is forecasted for next week! I heard on the radio about a film about plastic in the sea, think it was called Blue or Breathe, but when I googled I could not find it. If I hear again I will let you know. You probably don’t realise you sent me a card, had a Greek stamp on it, tomorrow we will be singing a certain Beatles song?? Many thanks. Keep the turtle tales coming. Love from a chilly Sweden, though fine autumn colours and we found kanterell in the hills. Mike

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