Friday 15 February 2008 à 14:47

A veritable floating laboratory!

Par Philippe Koubbi. Correspondent aboard the Umitaka Maru

(written with Patrice Pruvost)
As you know from preceding dispatches, the Umitaka Maru is a veritable floating laboratory. At each station, all the scientists on board wait impatiently for the samples to get at the materiel needed for their research.

Everything is examined with a fine-tooth comb in order to describe better the biodiversity of the Dumont d’Urville Sea. Several teams, specialized in the different aspects of the ecosystem, use physical and chemical methodologies to analyze all the hydrological parameters, from plankton (phytoplankton and zooplankton) to nekton (fishes and cephalopods).

From the assorted sampling stations in the middle of the ocean’s immensity, we are now going to move to the second phase of the program, which will take place in the laboratory: detailed identification of the species and ecological analyses. These will let us understand how biodiversity functions in this sector and its hydrological and ecological specifics.

Professor Takashi Ishimaru and Graham Hosie coordinated all the scientific activities on the ship, in association with the different teams.

Takashi Ishimaru and Graham Hosie.

Now we introduce you to the work of foreign colleagues traveling with us.

1. Oceanographic parameters

The physical and chemical parameters of the water are measured by recorders or after filtering out the different elements in the water. Nutrient salts, photosynthetic pigments, etc. are all measured.

Kazuo Amakasu, assistant professor at TUMSAT.

2. Phytoplankton

Phytoplankton is studied by filtering the water or by examining the different algae caught in the nets under a microscope. Two teams are working on studying these parameters on the ship.

My name is Naho Horimoto and I am an assistant professor at the TUMSAT laboratory (link to their site). I am studying the spatial variation in species composition and carbon biomass of phytoplankton. I also have two more interests; phytoplankton photosynthetic performance, and the relationship between phytoplankton growth and microzooplankton. Primary production is assessed from C13 uptake and FRRf (fluorescence) techniques.

Naho Horimoto, © J.H. Hecq.

I am Toru Hirawake and I am accompanied by Naoki Kondo. We work at the Graduate School of Fisheries Sciences, Hokkaido University. The objectives of our study are to:
1. reveal the relationship between optical properties and the dominating phytoplankton group,
2. quantify the relationship between light absorption and primary productivity, and
3. validate satellite ocean color sensors in the Southern Ocean.
We measure underwater spectral radiation (PRR-800/810, Biospherical), light absorption and beam attenuation (ac-s, WETLabs), volume scattering function (VSF3P, WETLabs), and aerosol optical thickness (Microtops II, SOLAR Light). Sea water samples are also treated to analyze chlorophyll a concentration, pigments composition with HPLC, and light absorption of particulate and dissolved materials. Results from these measurements will be utilized for the estimation of phytoplankton groups and primary production using satellite ocean color data.

Toru Hirawake, © J.H. Hecq.

3. Zooplankton

Zooplankton is sampled with nets of different-sized mesh and it is studied as a function of the size of the organisms. The microzooplankton will be studied in the laboratory after the campaign. The macrozooplankton has been partially sorted on the ship, identified, photographed and entered in collection records. Two other teams worked in parallel to carry out this work, as well as that of Jean-Henri Hecq: Russel Hopcroft’s team and Dhugal Lindsay’s team.

An echosounder was used to detect krill in the water column. Catches help calibrate the signals received.

Russel Hopcroft, © J.H. Hecq.

I am Russel Hopcroft, and I work as an associate professor with the University of Fairbanks in Alaska. Let me quickly introduce you to my activities. The diversity of zooplankton communities is unknown to the public and poorly appreciated by many scientists. During the CEAMARC cruise, I am taking three approaches to address this gap.
- Firstly, along with colleagues Dhugal Lindsay and Veronica Fuentes, we will be focusing on the soft-bodied “gelatinous” zooplankton that are often neglected in the analysis of zooplankton samples. Gelatinous zooplankton are important planktonic predators, but because they are heavily damaged by collection with traditional nets—and distorted or dissolved by preservatives—identification and quantification are problematic. Our team has the expertise to address this taxonomic gap and identify new species within these groups.

Veronica Fuentes, post-doctorate at the Instituto Ciencias del Mar, © J.H. Hecq.

- Secondly, to improve the general appreciation of zooplankton diversity, we are taking numerous images of living specimens observed underwater or under our microscopes to share their beauty publicly.
- Thirdly, we are contributing specimens to a global zooplankton DNA “barcode” library as a tool to help resolve new species and aid future identification..
Dhugal Lindsay, © J.H. Hecq.

My name is Dhugal Lindsay and I work at the Japan Marine Science and Technology Center.
The sea is full of tiny animals floating with the currents–the plankton. Plankton at the sea surface can be captured alive in bottles and jars. However, to observe the plankton that live far below the surface in the darkness of the deep sea, we haul fine-meshed nets and retrieve them from their hidden habitats. Many animals die or are damaged in the long haul to the surface as their tiny bodies smash against the sides of the net or against each other. Nevertheless, these specimens are invaluable for us humans to figure out how the ocean works and how we are impacting it with our modern society.

Another way to study the plankton is to send special cameras into the ocean to photograph them or videotape them in their own habitat. This is perhaps the best way to study the gelatinous plankton, whose bodies are so fragile that they are often completely destroyed by plankton nets. On this CEAMARC cruise my colleagues and I we will be using the MULTISPLASH frame, a platform consisting of a high-definition video camera and 150-watt halogen light, two in situ darkfield illumination microscopes (color Visual Plankton Recorders or color VPRs), a CTD (Conductivity Temperature Depth meter), a dissolved oxygen meter, a chlorophyll sensor, turbidity meter, and a transmissometer, particularly to investigate such gelatinous organisms as siphonophores, ctenophores and medusae, which are voracious predators, that can occur in huge numbers, and are still not well understood. The array of sensors on the MULTISPLASH frame will allow us to correlate distributions and habitat preferences of the gelatinous fauna to a level of accuracy that is virtually impossible using more traditional survey approaches. We will also, of course, be looking through the contents of any net that comes to the surface for specimens to correlate with the images we capture in situ, to aid us in our task of identifying real animals from the images we are gathering.

4. Nekton

Nekton was studied by two teams: one led by Philippe Koubbi with Eric Tavernier and Patrice Pruvost and the other led by Moteki San.

Masato Moteki, © J.H. Hecq.

I am Masato Moteki, assistant professor at TUMSAT, and I have two major interests in the Antarctic Ocean. One is to clarify fish fauna in the meso- to bathypelagic realm in the Indian Ocean Sector. This realm is one of the most unknown parts of the earth.

Our previous researches made by Training and Research Vessel Umitaka Maru off Lutzow Holm Bay and on the 140° E meridian line have clarified larger biomass of fish below 500 m depth than we expected.

Another aim of my study is to clarify early life history of major taxa in the Antarctic Ocean (e.g. Myctophidae, Bathylagidae, Gonostomatidae, Notothenioidae). Vertical and horizontal habitat migrations with larval development, including osteological development, are known in the other sea. However, in the Antarctic Ocean, knowledge of this larval migration is limited to a few major species. Comparative study of early life history of fishes would be helpful to clarify unique evolution processes in the Antarctic Ocean.
TRV Umitaka Maru is equipped on this cruise with a multiple opening/closing net system (RMT 1+8) and large pelagic trawl (IYGPT). Research by this ship and collaborative study with Phillipe Koubbi, Patrice Pruvost and Eric Tavernier, and scientists in the other fields would achieve large progress in the various fields of ichthyology.

All the scientific teams were assisted by many masters and doctoral students, a few of whom we show here:

- Fuminori Hashihama, Saori Yasui.

- Margaret Lindsay, Andrea Walters.

- Ryoji Toda, Rina Nagano, Naoki Kondo.



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