The main goal of CODENET, which was to understand the ecological and evolutionary patterns of coccolithophore diversity, has been achieved by extensive collaboration between researchers at eight different European institutions. Coccolithophores are cosmopolitan unicellular planktic marine algae and their exceptional fossil record preserved in deep-sea sediments offers a unique opportunity to test evolutionary hypotheses and the links between this dominant oceanic phytoplankton group, ocean dynamics and climate. In order to more efficiently utilise fossil coccoliths as tracers of past global changes, it is necessary to understand their biodiversity and ecology at the present day and their evolution during the geological past.
CODENET focussed on seven of the most common living coccolithophore taxa in the world's oceans. A multidisciplinary team of geologists, chemists, biologists and oceanographers from the various institutes, studied different aspects of these keystone species. Individual cells of these species were captured by various CODENET researchers and laboratory cultures were eventually maintained at University of Caen. Strains of these cultures formed the basis of detailed ecological, morphological and biomineralisation experiments carried out by various teams. A key theme within the experimental work was the relationship between morphology and ecology and its role in addressing the fine scale biodiversity observed in all keystone taxa. Molecular genetic analyses of these and other strains carried out by the AWI team led to the development of a molecular genetic tree containing all keynote species and their relationship with other major phytoplankton groups. This tree, which is the first of its kind, confirms that much of the fine scale morphological groups are in fact separate species.
The hypotheses erected through focussed experimental work and molecular genetics was also strengthened by extensive observations of modern coccolithophores from filtered water samples (ETHZ, CSIC, NMH). An electronic microfossil image data base (EMIDAS) with over 200 high-resolution SEM images of 120 living coccolithophore species was developed by the ETHZ team and is available on the internet for scientific reference and teaching.
The analysis of sediment trap samples by the ETHZ team clarified the contribution that each of the keynote coccolithophore species makes to the calcium carbonate transferred to the deep-ocean basins. The burial of calcium carbonate is an essential component of the carbon cycle and is a major factor controlling the Earth's climate. In addition, significant progress has been made by scientists from the ETHZ, CSIC and NIOZ teams towards understanding the pigments and alkenones released by coccolithophores upon death and their potential as a tool for palaeoreconstructions.
The analysis of fossil coccolithophores was also a major component of the CODENET project. The calculation of divergence times by the AWI group using the molecular clock technique permitted the calibration of genetic events with those of the classic morphological approach which has up to now been used to interpret coccolithophorid evolution. New morphological analyses of fossil coccolithophores tied in well with the analysis of the living keystone species and will improve the interpretation of biodiversity back in geological time. Morphometric analyses at ETHZ led to the development of new paleotemperature transfer functions which can be applied in the future to extremely small sediment samples such as those found in annual varves in anoxic basins.
The overall perspective that was afforded by this highly rewarding project has spearheaded a new approach to the scientific analysis of coccolithophores. Multidisciplinary collaboration which seeks to link the present and past and large and small scale processes by combining biology and ecology with palaeontology and oceanography, will be highlighted and further promoted at the forthcoming Coccolithophore Conference (CoccoCo) organised by the ETHZ team at Monte Verità, Ascona.
CODENET Teams
The Natural History Museum, London, U.K. (NHM)
ETHZ, Zurich, Switzerland (ETHZ)
Vrije Universiteit Amsterdam, Netherlands (VU)
Universite de Caen Basse Normandie, Caen, France
Alfred Wegener Inst. fuer Polar und Meeresforschung, Bremerhaven, Germany (AWI)
Institut de Ciencias del Mar, CMIMA (CSIC)
Museu Nacional de Historia Natural da Universidade de Lisboa, Portugal
Nederlands Instituut voor Onderzoek der Zee, Amsterdam, Netherlands (NIOZ)
WWW - Links
CODENET -
http://www.nhm.ac.uk/hosted_sites/ina/CODENET/index.htmlETHZ Micropalaeontology Group - http://www.geology.ethz.ch/mp/
EMIDAS-
http://www.emidas.ethz.chCoccoCo -
http://www.coccoco.ethz.ch/
