Exploring the Indian Ocean by research vessel

By Jennifer Appoo. Jennifer is a PhD student supervised by Prof Sébastien Jaquemet from the University of La Réunion and Dr Nancy Bunbury from the Seychelles Islands Foundation.


The first time I participated in a research cruise, I had no idea what to expect. Even though I had a general theoretical knowledge of oceanography from my undergraduate courses, actively conducting research at sea was an unknown territory to me. Yet, from the first time I stepped on a research vessel, I felt like I was in the right place. Not only did I discover amazing tools and technologies used to conduct research at sea, I also discovered a world unknown to most – the open ocean.


Before I share my experience on research cruises, some context: I’m from the Indian Ocean, one of the least explored oceans on the planet. Compared to the Pacific and Atlantic Oceans, the Indian Ocean is bordered by less developed countries, where technologies, resources and capacity for ocean-based research is limited. The majority of marine research is concentrated within recreational human diving depths, often down to 30 m, and very little is known beyond this depth. In addition, most studies are conducted within coastal zones, usually within a few hundred metres of coastlines. However, over the last decade, scientific interest has increased on the broad state and functioning of the Indian Ocean, both at depth and away from the coasts in the open ocean areas.


Venturing into these unknowns is mostly done aboard a research vessel. These are essentially floating laboratories, equipped with often large and heavy tools deployed by a winch to collect samples; laboratories to process samples; and state-of-the-art technologies to collect and process large datasets. Combined, they enable information to be collected from incredible depths and across wide areas. Usually, research at sea occurs on a continuous basis. The ship moves along pre-defined transects from the start to the destination, along which there are multiple sampling stations. Unless the sampling is day or night-dependent, sampling can occur at any time. One often sleeps at off-hours or whenever there is a break in the schedule, which, depending on the sampling requirements, might be as little as 4-5 hours between each sampling station. A research vessel brings together scientists from different backgrounds and disciplines, so teamwork and adaptation is key. The work is dynamic, engaging and exciting.

Preparing to board the French research vessel Marion Dufresne


My experience on research vessels is all recent. It started around mid-2018, when I got the opportunity to join the Norwegian research vessel Fridtjof Nansen, conducting research across the Indian Ocean. To increase regional marine research capacity, the expedition was open to participants from countries in the survey area and I was amongst several regional scientists to apply and join the cruise. The ship trajectory started from South Africa to Sri Lanka, and was separated in several sections, called ‘legs’. I joined the leg from Mauritius to Sri Lanka crossing right across the middle of the Indian Ocean. For this leg, the main aim was to explore the distribution of mesopelagic fish, i.e. fish living at 200–1000 m depth, from the higher-oxygen regions of the southern Indian Ocean to the low-oxygen regions of the northern Indian Ocean. For this, we used net trawls of different sizes, which were deployed at variable depths to sample plankton, zooplankton and mesopelagic fish. Alongside this, the cruise aimed to collect in-situ properties of the water column to explore the influence on the distribution of mesopelagic fish. Here, I discovered equipment like the ‘rosette’ equipped with sensors and niskin bottles, able to sample water at depths down to 3000 m. The rosette is also called a CTD which represents some of the parameters it measures; conductivity, temperature and depth. The most formative experience on this cruise for me was seeing fishes with glowing blue-green lights embedded all over their bodies, aptly-named lanternfish. This group of mesopelagic fish bears light-producing organs called ‘photophores’ which are used for seeing and signaling in the dark, helping the fish blend in with light-speckled water and confuse predators.

Classifying mesopelagic organisms obtained from trawls by taxa

Lanternfishes with photophores, special organs used to produce light


For my next research cruise, I stayed closer to home, on board the Nekton Expedition in March 2019, which aimed to explore for the first time, the deep seas of Seychelles. The main goal of the expedition was to explore the benthic communities, i.e. animals living on the sea floor, and fish communities, from 10 m to 250 m deep. This cruise used primarily video systems such as remote-operated vehicles (or ‘ROV’), drop cameras, and manned submersibles to film the ocean floor. To increase opportunities in marine research for local scientists, participation in the expedition was based on research proposals using data collected during the expedition. I was selected for my research aiming to investigate the marine predator community around Aldabra Atoll, from the shallows to the deep, using video data.

On this cruise, I got the most incredible opportunity to join a submersible dive to 250 m deep! It still feels surreal writing about it. Descending in the submersible, I observed the gradual change in communities, from vibrant coral reefs at 30 m, to reefs covered with 2-3 m wide sea fans at 50 m, then to rocky substrates colonized by sponges and whip corals at 120 m and finally to bare rocky substrate at 250 m.

The water column was filled with ‘marine snow’ – sediment and organic particles falling to the seabed, which appear white due to the light from the camera systems making it look like it is snowing. The expedition obtained the first video sighting of a sixgill shark on Aldabra at 300 m, which was an exciting find for my research project!

Benthic communities at various depths seen at Aldabra during the Nekton Expedition © Nekton


Just a few months later, in October 2019, I found myself back at sea on board the Sonne, Germany’s largest research vessel in the Indo-Pacific region. Based on my previous experiences on research cruises, I participated as an observer. Our study location was a submarine bank close to Seychelles. The aim was to map the structure and composition of this submarine bank and explore how it is affected by different water masses. Here, I discovered methods involving hydro-acoustics, which are used to create 3D maps of seabeds and multiple corers for collecting sediment and rocks. The CTD was used again to study the water masses. Together, these provide information on the paleo-oceanographic changes of the submarine bank.

A fellow participant and myself collecting seawater from a rosette (or CTD) used to measure physico-chemical parameters of the water column


I write this blog as I travel again across the Indian Ocean, this time between the islands around Madagascar on board the Marion Dufresne, a 120-m long French research vessel, on my fourth research cruise. Although we are at sea, we are monitoring ocean processes linked to islands. This covers multiple disciplines such as; volcanology and geology to examine island history; oceanography to investigate island effects on the ocean; and marine biology to assess communities around oceanic islands. This cruise is unusual in that it’s essentially a training cruise. On board, students from Kenya, Tanzania, Madagascar, Seychelles, Mauritius and La Reunion are getting hands-on training from scientists, technicians and engineers on methods to collect all this information. Applications to participate were open to postgraduate students in geoscience and marine science from the Western Indian Ocean and we were selected based on our background, training requirements, capacity building intentions, and our CV.

The connection to islands and the diversity of culture on-board is probably what makes this cruise one of my favourites!

Sixgill shark sighted on Aldabra at 300 m on the drop-cam ©Nekton.

Being confined on a vessel and being surrounded by nothing but the vast ocean for many days or weeks can be challenging but I realise that I’m one of the lucky few to be able to discover the wonders of science and the ocean at the same time. Most importantly, I’ve been able to meet and exchange with researchers, students and mariners from diverse backgrounds, but who share a similar passion for the ocean.

In this space, I have grown, become more motivated and reassured in my choice to become a scientist. With every expedition, the secrets of the Indian Ocean are being discovered but most importantly, creating local custodians who are being empowered to act as ocean ambassadors.

In the submersible going down to 250 m © Nekton

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