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PICODIV Roscoff Sampling Station

PICODIV Roscoff Sampling Station. Context : Western English Channel.  A large shallow continental shelf. 100.  Stratified, frontal and homogeneous regions. Maddock et al. 1981. Homogeneous. Statified. Frontal. Euphotic zone. Shallow. Deep. Aphotic zone. Maguer et al. 1996.

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PICODIV Roscoff Sampling Station

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  1. PICODIV Roscoff Sampling Station

  2. Context : Western English Channel  A large shallow continental shelf 100

  3.  Stratified, frontal and homogeneous regions Maddock et al. 1981

  4. Homogeneous Statified Frontal Euphotic zone Shallow Deep Aphotic zone Maguer et al. 1996

  5. « Stratified regions » (summer stratification) : classical seasonal cycle - Spring Diatom Bloom - Production controlled by Nitrate concentration Homogeneous regions : Very original seasonal cycle Tidal currents and winds are major processes - Late spring/summer Diatom bloom - Production controlled by light all year round - Phytoplankton grows essentially on regenerated N in summer)

  6. Characteristics of the water column off Roscoff - Long term study (salinity, temperature) since 1952 - Present Long-term studies sites (ASTAN, ESTACADE) ASTAN ESTACADE

  7. ASTAN ESTACADE Maguer et al. 1996

  8. ASTAN : Depth profile (Chl a, T°, Salinity)

  9. ESTACADE : measurements of phycical, chemical and biological parameters (1985-1992, 1994- ) - Depth = 3-11 m - sampling = 2 X per month at neap-tide - 1 m depth Physical and chemical conditions at the ESTACADE (1985-1991)

  10. (µM L-1) (µM L-1) - Maximal values in automn and/or winter - Short term impoverishment in spring - Phosphates concentrations have a similar evolution

  11. (µM L-1) - Variations are opposite to variations observed for Nitrate and Nitrite (µM L-1) - Maxima in autumn and winter - Never = 0

  12. in µg L-1 - Maxima in late spring or summer - 0,2 to 2 µg Chla L-1 in cells mL -1 - Significant numbers in spring and summer only (100-1700 cells per mL) - Maxima in spring (Guinardia delicatula)

  13. - No adequation between Chl a concentration and Diatom (> 20 µm) cell number  Other phytoplankton groups contribute to Chl a biomass (Dinoflagellates, Dictyochophyceae, etc.)  Smaller cells

  14. Picoplankton cell numbers : ESTACADE (86-88) Cell numbers per mL Time - Synechococcus : 1000-10000 cells/mL - Stable - Picoeukaryotes : 1000-30000 cells/mL - More Variable

  15. Station S : Study conducted over 1 year (1992-93) 15-200 µm 1-15 µm < 1 µm Spring Summer Autumn Winter Maguer 1995

  16. What about the diversity ? Microphytoplancton - Winter : high diversity, lots of benthic species in plankton - Spring and summer : low diversity, small species with long chains

  17. Species diversity indices A B Summer phase : Low diversity Winter phase : High diversity 5 species = 95 % of total population No species < 30% of total population More benthic species Grall et Jacques (1983) (1962-1963)

  18. Occurrence of selected species off Plymouth (1963-85) Boalch 1989 Long-term variations

  19. Picophytoplancton - Synechococcus - Picoeukaryotes : few data come from observations with TEM Micromonas pusilla Chrysochromulina sp. Petasaria sp. Prymnesiophyceae Pedinophyceae? Prasinophyceae Chrysophyceae Bacillariophyceae

  20. PICODIV : - Samples taken around midday, bi-mensually (lowest tide coefficient): < 200 µm - T°, N, P, Si, Chl a, Lugol fixed sample, Formalin fixed net sample - Samples for HPLC (1 L, <3µm, >3µm) - GF/F, Nuclepore - Samples for FISH (200mL) - Anodisc - 4 times per year : DNA samples + isolation of cultures

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