Is the Chagos archipelago a stepping-stone across the Indian Ocean?

by ZSL on

Dr Catherine Head, University of Oxford, joins the Bertarelli Programme in Marine Science expedition to the British Indian Ocean Territory to investigate the connectivity of the coral reefs.

As we sit in the ship’s mess checking our specimen spreadsheets (the less glamourous side of the work, that’s for sure) we have a chance to reflect on how much we have achieved so far on this reef expedition. April and I (the Oxford Uni team), just one dive team on the Chagos Reef expedition, are collecting small fragments of 3 coral species: Acropora tenuis, Acropora cytherea, Porites lutae (don’t worry the samples are very small and taken in the most ecologically sensitive way possible – the last thing we want to do is contribute to reef degradation).

We collect and then photograph each individual colony in order to check it with Charles Sheppard, our expedition coral expert, that we have the right species because these species can be incredibly difficult to tell apart from other Porites and Acroporas on the reef.

Table Acropora with juvenile damsels, BIOT
Table Acropora with juvenile damsels in BIOT

The aim of the study is to see how connected each area of reef is to other areas in the archipelago by looking at the genetic structure of the corals. This will help us understand perhaps why some reef areas are able to recover quicker than others; for instance you would expect (all other variables being equal) that the more connected reefs, in terms of larvae flow, would have a better ability to recover than others.

We also plan to extend this study out to the wider Indian Ocean to see if the Chagos archipelago acts as stepping-stone across the Indian Ocean for coral larvae as has been suggested and found for other species.

For this we will need to collect samples from other areas in the Indian Ocean for genetic structure comparison, for instance from Seychelles, west coast Indonesia and east coast of Africa. This will be incredibly interesting and have real implications for understanding how important it is to protect the Chagos Archipelago’s marine environment for the wider Indian Ocean’s reefs.

 CH and AB on deck prepping ARMS unit. BIOT BPV.
Catherine Head and April Burt prepping ARMS equipment for use

So, once we get back to Oxford I’ll be in the lab doing DNA extractions on these coral samples, sending them off for genomic sequencing and analysing the data. In the meantime we’ll enjoy our busy dives collecting our corals, and also collecting water samples to look at zooplankton diversity using Environment DNA methods and deploying Autonomous Reef Monitoring Structures (ARMS) to look at cryptofauna diversity.

Whilst, also helping our Stanford project partners (Rob Dunbar’s team) deploy their various oceanographic instruments in order to measure the abiotic variables, e.g. pH, Oxygen levels, temperature, currents, which we can subsequently use to see what might be driving the biodiversity patterns. But more about these in the next blog!

For more updates from this and future expeditions follow us on Twitter @BIOTScience

This work was kindly funded by the Bertarelli Foundation as part of the Bertarelli Programme in Marine Science.

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