skip to primary navigation skip to content
 

Landmark issue 2

Current Postgraduate Research

The Amiranti Ridge

By Sarah Hamylton

Amiranti Ridge diagram

Interested in the application of Geographical Information Systems (GIS) and Remote Sensing (RS) to environmental management problems, with reference to tropical marine ecosystems

The Seychelles islands are renowned for white beaches, clear blue seas and uncomplicated indulgence, our fieldtrip to Alphonse atoll was just that experience! In September 2007, I was invited to spend six days on an atoll that had spent as many months on my computer screen in Cambridge. Needless to say, I jumped at the chance! Our task was to ground reference one of a series of 12 habitat maps of islands along the Amiranti ridge in the West Indian Ocean, produced by the Geography Department’s Coastal Research Unit and Unit for Landscape Modelling. Airborne remote sensing surveys had been carried out over each island for the production of digital habitat maps, a basis for modelling the shallow water community dynamics. Despite staying in a resort closely resembling utopia, our team had a "to do" list so long that it weighed on my mind. Relaxation was replaced by a sort of sixth sense, a constant alertness to ways in which our surroundings could be recorded and analysed. An unrelenting voice in my head asked "What are the processes at work here? How can they be quantified? Where do they sit among my existing body of knowledge? Why can’t I forget this and sunbathe by the pool?!" Like most tourists, my experience was one of indulgence, but my cocktail was a blend of underwater adventure, physical exertion, intellectual stimulation and the satisfaction of achievement at the end of the day. To give you an idea of the flavour, I will describe one of our days in the field. Woken for breakfast at 6.30am, we jumped onto our bicycles (ideal transport on a flat atoll!) and cycled to the staff kitchen for bread rolls and a cup of tea. Following a discussion our boat skipper, we decided to make the most of the flat calm sea to survey the southeast point of the atoll, where the trade winds usually blew a prohibitive gale. After bundling an assortment of bathymetric sounders, underwater cameras, measuring tapes and dive kit into the boat, we motored towards the lagoon channel, using a GPS to guide us to our survey site. Crossing the ominous Canal Du Mort, the fins of a pod of Bottleneck dolphins broke the surface of the water next to our boat. We spared a few minutes to jump in and photograph the pod, which made a surprised getaway upon our appearance. At our survey site, we kitted up and descended to the spur and groove coral formations. With photo records of community transects and profiles of the reef topography, we jumped back into the boat and motored in the direction of the resort. Taking advantage of the calm conditions, we took in a quick snorkel survey of the southeast atoll face, which ended uncomfortably near the wave breaker zone! Finning back to the boat, the swell failed to curb my excitement at having collected bathymetric profiles from a highly desirable, yet virtually forbidden, area. Returning through the lagoon, we took GPS positions of a few patch reefs, to cross reference back to the map and headed in to refill our cylinders before lunch. The afternoon was spent carrying out topographic surveys of the substantial reef flat. This consisted of wading through knee deep water to measure vertical profile changes associated with the various seagrass, rubble and sand zones. We were certainly pleased to see the boat coming to collect us once finished, with the rising tide and numerous rays swimming close to see what all the fuss was about. Once back, there was just enough time to help Lindy, the head of the Island Conservation Society overlay the locations of her much loved Wagtail Shearwater nests onto the our digital map before dinner. Afterwards, remaining energy stocks allowed us to cycle out to these nests and pay the comical flightless birds a visit, before returning to enter the days data and collapse, exhausted but happy!

Sarah Hamylton

Sarah Hamylton

My interest is in the application of Geographical Information Systems (GIS) and Remote Sensing (RS) to environmental management problems, with reference to tropical marine ecosystems.

To find out more about Sarah go to:
www.geog.cam.ac.uk/people/hamylton/

 

* Navigating to points of interest on the habitat map (Source: A. Hagan)

* Reef flat surveys for habitat map validation (Source: A. Hagan)

* A view of Alfonse Atoll from space