Report of the 2004 Workshop on In Situ Iron Enrichment Experiments in the Eastern and Western Subarctic Pacific

Foreword 1. BACKGROUND AND OBJECTIVES (pdf, 0.1 Mb) 2. 2004 WORKSHOP SUMMARY (pdf, < 0.1 Mb) 2.1. What have we learned from the enrichment experiments? 2.2 What are the outstanding questions? 2.3 Recommendations for SEEDS-II 3. EXTENDED ABSTRACTS OF THE 2004 WORKSHOP 3.1 Synthesis of the Iron Enrichment Experiments: SEEDS and SERIES (pdf, 0.5 Mb) Iron fertilization experiment in the western subarctic Pacific (SEEDS) by Atsushi Tsuda The response of N and Si to iron enrichment in the Northeast Pacific Ocean: Results from SERIES by David Timothy, C.S. Wong, Yukihiro Nojiri, Frank A. Whitney, W. Keith Johnson and Janet Barwell-Clarke 3.2 Biological and Physiological Responses (pdf, 0.2 Mb) Zooplankton responses during SEEDS by Hiroaki Saito Phytoplankton community response to iron and temperature gradient in the NW and NE subarctic Pacific Ocean by Isao Kudo, Yoshifumi Noiri, Jun Nishioka, Hiroshi Kiyosawa and Atsushi Tsuda SERIES: Copepod grazing on diatoms by Frank A. Whitney, Moira Galbraith, Janet Barwell-Clarke and Akash Sastri The Southern Ocean Iron Enrichment Experiment: The nitrogen uptake response by William P. Cochlan and Raphael M. Kudela 3.3 Biogeochemical Responses (pdf, 0.5 Mb) What have we learned regarding iron biogeochemistry from iron enrichment experiments? by Jun Nishioka, Shigenobu Takeda and W. Keith Johnson Iron dynamics and temporal changes of iron speciation in SERIES by W. Keith Johnson, C.S. Wong, Nes Sutherland and Jun Nishioka Dissolved organic matter dynamics during SEEDS and SERIES experiments by Takeshi Yoshimura and Hiroshi Ogawa Formation of transparent exopolymer particles during the in-situ iron enrichment experiment in the western subarctic Pacific (SEEDS) by Shigenobu Takeda, Neelam Ramaiah, Ken Furuya and Takeshi Yoshimura Atmospheric measurement by Mitsuo Uematsu 3.4 Prediction from Models (pdf, 0.3 Mb) Modelling iron limitation in the North Pacific by Kenneth L. Denman and M. Angelica Peña A proposed model of the SERIES iron fertilization patch by Debby Ianson, Christoph Voelker and Kenneth L. Denman 4. LIST OF PARTICIPANTS FOR THE 2004 WORKSHOP (pdf, < 0.1 Mb) APPENDIX 1 Report of the 2000 Planning Workshop on Designing the Iron Fertilization Experiment in the Subarctic Pacific (pdf, 1 Mb) APPENDIX 2 Terms of Reference for the Advisory Panel on Iron fertilization experiment in the subarctic Pacific Ocean (pdf, < 0.1 Mb) APPENDIX 3 Historical List of Advisory Panel Members on Iron fertilization experiment in the subarctic Pacific Ocean (pdf, < 0.1 Mb) APPENDIX 4 IFEP-AP Annual Reports (pdf, 0.1 Mb) APPENDIX 5 PICES Press Articles (pdf, 0.6 Mb) (194 page document

Chromatic Acclimation in Cyanobacteria: A Diverse and Widespread Process for Optimizing Photosynthesis

International audienc

Phytoplankton dynamics and bio-optical variables associated with Harmful Algal Blooms in aquaculture zones

The surveillance of Harmful Algal Blooms (HABs) in aquaculture zones is a crucial component in monitoring and mitigation of adverse effects caused by accumulation of high biomass of algal cells and/or associated toxins. Integrated findings of this thesis strongly stress the significance of synoptic bio-optical and conventional measures for efficient surveillance of HABs and their environmental triggers over required spatio-temporal scales, here shown for a case study in the Ebro Delta, NW Mediterranean. In particular, the installation of an environmental observatory in the Ebro Delta aquaculture area, and the capability of a radiometric sensor system as key component are highly motivated by study results. Yet it was clearly shown that for the interpretation of bio-optical data, detailed knowledge on bloom characteristics is crucial. By such effective coverage of bloom dynamics, combined with insights on environmental scenarios that promote the proliferation of certain taxa, public and private responses can be optimised. In a future scenario, this knowledge can be transferred to predictive models of HABs. In this sense, these future steps may advance towards preventive measures rather than mitigation actions to deal with this environmental hazard

MOLECULAR STUDIES OF KARENIA MIKIMOTOI (DINOPHYCEAE) FROM THE CELTIC SEA REGION

K. mikimotoi has been classified under many names and has been mis-assigned to different species and genera in the North Atlantic and Pacific because of its morphological similarities to other Gymnodinoid species. It is now known to be widely distributed, but there remain unresolved questions about whether K. mikimotoi was introduced into the North Sea from Japanese waters, or whether it has always inhabited this region and been erroneously classified as Gymnodinium spp. or has been a part of the hidden flora prior to be recognised in a bloom off the Norwegian coast in 1966. To address questions about geographical genetic variation within K. mikimotoi and broader issues about its biogeography it was deemed important to develop a suitable diagnostic molecular marker that could then be used to monitor the presence/absence of different K. mikimotoi ecotypes over long time scales in European waters. This study showed that the partial rDNA LSU (D1-D2) was too conserved to separate the different strains of K. mikimotoi, while, the ITS region was better able to discriminate between the different strains. However, the rbcL gene was the most informative gene and contained sufficient substitutions to separate the different strains of K. mikimotoi. Specific PCR-primers were designed to amplify a variable region of the rbcL gene able to distinguish differences between K. mikimotoi isolates from the different regions. The innovative high resolution melting temperature (HRM) technique based on specific primer set allowed rapid discrimination of K. mikimotoi from distinct geographic localities (= sequence variants) that differed by only a single nucleotide. Moreover, this study used archival environmental samples collected from the Celtic Sea shelf-break region. The high resolution melting temperature assay successfully detected the European K. mikimotoi isolate within the south-western English Channel in a 1963 sample, which is prior to thefirst report of a K. mikimotoi bloom in Norwegian waters in 1966 and in the south-western English Channel in 1975 and in western Japan in 1965. HRM observations were further validated using clone libraries and sequencing. In summary, this data provided more information about the genotypes present over the analysed timescales, revealing that K. mikimotoi sub-species 2 (European and New Zealand strains) was present in south-western English Channel and south-west Ireland for over 47 years, with sub-species 1 (the Japanese isolate) being absent from all examined samples. This finding supports the hypothesis that K. mikimotoi isolates within Europe are not of Japanese origin and suggests that they are native species to the region.Kuwait Institute for Scientific Researc

Accounting for mixotrophy within microbial food webs

Protist plankton contribute to both primary and secondary production in the oceans fuelling life within pelagic food webs. Despite commonly perceived as ‘phytoplankton’ or ‘zooplankton’, most protist plankton are mixotrophs through the combination of photoautotrophy and phagotrophy within a single cell. Nevertheless, we lack a clear understanding of their biogeography and impact on ecosystem functioning. The aims of this thesis were: i) to investigate the biogeography of mixotrophs according to their functional diversity across oceanic biomes and to evaluate how it relates to environmental variability; ii) to explore the competitive outcomes between mixotrophs and their auto- or hetero- trophic counterparts and the effect of mixotrophy on ecosystem functioning; and iii) to investigate the seasonal succession of protist trophic strategies and the vertical distribution of mixotrophs within a coastal temperate sea. These aims were explored utilizing global databases, long-term monitoring datasets, and numerical models of plankton food webs across different spatio-temporal scales. Mixotrophs were found to be ubiquitous in the global oceans; however, different types displayed different distributions. Among non-constitutive mixotrophs, those that host prey populations dominate within oligotrophic seas while those that steal prey plastids dominate high-biomass systems. In turn, global databases were strongly biased by size, taxonomy, and oceanic biome, failing to represent the importance of smaller constitutive mixotrophs. The modelling studies showed that mixotrophs control nutrient regulation, trophic transfer, and the microbial loop. Size was an important trait determining the success of mixotrophs with an innate capacity for photosynthesis while the specificity of prey from which acquired phototrophs can photosynthesize affected their success. Model and data showed that mixotrophy is a persistent trait over the seasonal cycle and throughout the water column within coastal temperate seas. These findings significantly change our understanding of the functioning of marine food webs and biogeochemical cycling in the oceans, underscoring the need to integrate mixotrophy within marine ecology research

Influence de la lumière et de l'horloge circadienne sur la gestion de la carence en fer chez Ostreococcus sp.

Iron is an abundant element in the earth crust and is essential for almost organisms. In the marine environment, however, its bioavailability is often low and the iron supplies sporadic. Phytoplanktonic species have developed various strategies to face iron limitation and adapt to different ecological niches. Green picoalgae from the genus Ostreococcus (Prasinophyceae) are widespread in the global ocean and numerous ecotypes have been isolated from contrasted environments. The main objective of my thesis was to identify the strategie(s) used by the genus Ostreococcus in response to iron starvation and in particular the influence of the day/night cycle and the circadian clock in the regulation of iron homeostasis. I focused my work on the lagoon ecotype, Ostreococcus tauri (Clade C), which has emerged as a model organism for functional genomics approaches thanks to the development of genetic transformation by random insertion and homologous recombination. I have studied ferritin, a protein involved in iron storage which is present throughout the tree of life. I showed that ferritin is regulated by the light/dark cycle and the circadian clock and that it is a key player in the regulation of iron uptake and the recycling. Finally, I characterized the acclimation and adaptation strategies to iron limitations of several Ostreococcus ecotypes including O.tauri, RCC802 (Clade A), RCC809 (Clade B) and a cell biomass mutant of O.tauri. The reduction of cell biomass appears to be a main mechanism of acclimation in response to iron limitation.Le fer est un élément présent en abondance dans la croûte terrestre, indispensable à la quasi-totalité des êtres vivants. Cependant, en milieu marin la biodisponibilité du fer est souvent faible et sporadique. Les micro-algues du phytoplancton ont développé des stratégies pour faire face à cette limitation en fer et s’adapter à des niches écologiques variables. Les micro-algues vertes du genre Ostreococcus (Prasinophyceae) présentent une large distribution géographique dans l’océan mondial, et de nombreux écotypes venant de milieux contrastés ont été isolés. L’objectif principal de ma thèse était d’étudier les différentes stratégies mises en place par le genre Ostreococcus, et notamment l’influence de la lumière et de l’horloge circadienne, dans la gestion de la carence en fer. Mon travail s’est focalisé sur l’étude d’Ostreococcus tauri, écotype lagunaire (Clade C), que de récentes techniques de transformation par insertion et recombinaison homologue ont promu comme un organisme modèle pour des approches de génétique fonctionnelle. J’ai étudié la ferritine, une protéine impliquée dans la gestion de la réserve en fer chez de nombreux organismes, et mis en évidence sa régulation par l’alternance jour/nuit et l’horloge circadienne. J’ai montré son rôle dans l’assimilation du fer, la régulation de l’homéostasie du fer et le recyclage du fer intracellulaire lors d’une carence. Enfin, j’ai caractérisé les stratégies d’acclimatation et d’adaptation à la carence en fer chez plusieurs écotypes d’Ostreococcus, dont O. tauri, RCC 802 (Clade A), RCC 809 (Clade B) et un mutant de taille/biomasse. Une stratégie d’acclimatation par réduction de la biomasse cellulaire a été mise en évidence