CANDYFLOSS, Work Module 3 The Autotrophs

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1 2014 SSB AGM Liverpool CANDYFLOSS, Work Module 3 The Autotrophs Alex Poulton (NOC) Anna Hickman (University of Southampton)

2 CANDYFLOSS, WM3: The Autotrophs WM3 - THE AUTOTROPHS (Hickman/Poulton) Focuses on the uptake of inorganic C, N, P, Si by the Autotrophic components of the plankton community, and the partitioning of organic matter into dissolved and particulate forms. Supports Objective 2 (Determine the relative importance of external nutrient sources and internal biogeochemical cycling in maintaining the shelf pump). A Hickman, M Moore A Poulton, S Painter, A Rees, D Clark, G Tarran, M Stinchcombe C Widdicombe *Kieran Curran (SSB PhD) *James Fox (SSB PhD)

3 CANDYFLOSS, WM3: Hypothesis 3 C, N, P Si POC, PON, POP BSi, CaCO 3 DOC DON DOP Hypothesis - 3: Autotrophic community structure and resource availability influence the stoichiometry of organic matter through increasing C:N:P:Si ratios under nutrient depleted conditions. H3i: The spring bloom uses C and nutrients (N, P, Si) at close to canonical Redfield ratios. H3ii: Departures from spring stoichiometry occur in response to available resources; C:N within autotrophs will increase as N becomes limiting, accompanied by release of C-rich DOM. H3iii: Horizontal and vertical gradients in phytoplankton community structure drive shifts in the stoichiometry of POM and DOM.

4 CANDYFLOSS, WM-3: Plankton Succession Sp Wi Su Fa Widdicombe et al Western English Channel Observatory (L4)

5 CANDYFLOSS, WM-3: Development of particulate and dissolved stoichiometry Carbon Nitrogen Spring: Redfield C and N uptake Low DOC and DON production Summer: High C uptake relative to N (high C:N) Increase in DOC production (high C:N) Van den Meersche et al L&O - Expt. Bloom in Randers Fjord, Denmark

6 CANDYFLOSS, WM-3: Taxa specific elemental ratios Tend to be N rich under nutrient replete conditions (Relative to Redfield) Bertilsson et al L&O

7 CANDYFLOSS, WM-3: Vertical partitioning During summer, stratification of the water column and autotrophic community Influence on uptake and elemental stoichiometry Hickman et al 2009 L&O Celtic Sea

8 CANDYFLOSS, WM-3: The Plan (details) Each cruise: 4 process sites, 2 profiles per site, 6 light depths Each depth will have: Nutrients, SF-Chl-a, Autotroph abundance and biomass (AFC, Lugols, SEM), POC/N (WM5), POP (WM5), PIC, BSi, HPLC*, PABS*, FRRF* (*SSB PhD) Short-term (6 h) DIN (NO 3, NH 4 ) uptake and DON production ( 15 N) (Clark et al. 2011) Short-term (6 h) DIC and DIP uptake and DOC and DOP production ( 14 C, 33 P) (Bjorkman et al. 2000; Duhamel et al. 2006, 2007; Duhamel and Moutin 2009; Lopez-Sandoval et al. 2011) Daily (24 h) dsi uptake and BSi production ( 32 Si) (also DIP uptake via daughter 32 P) (Brown et al. 2003; Poulton et al. 2006a; Krause et al. 2011, 2012) Daily (24 h) Size-fractionated (0.2, 2, 20 μm) Primary production ( 14 C) (Maranon et al. 2001; Poulton et al. 2006b) Daily (24 h) Primary production and Calcite production ( 14 C) (Poulton et al. 2006, 2010, 2013) Short-term (2-3 h) Size-fractionated Photosynthesis v Irradiance Curves ( 14 C)* (SSB PhD) (Lorenzo et al. 2005; Hickman et al. 2012)

9 Abandoning on-deck incubators CANDYFLOSS, WM-3: The Plan (details) Simulated In Situ (SIS), on deck incubators: - irradiance driven by natural light conditions (clouds, snow) - irradiance also influences C:N uptake (Hickman 2007) - comparability between sites dependent on weather - CANDYFLOSS focus on stoichiometry not primary production Artificial light banks (LED light panels): - comparable / controlled irradiance across sites (& seasons) - ensure separate rate measurements comparable - successfully used within the UKOA program for pco 2 experiments - need to reconstruct in situ light levels (seasonal, depth) Spring Summer Fall Notes E above (mol PAR m -2 d -1 ) % RSD, 8-day satellite E 0 (mol PAR m -2 d -1 ) Based on 0.65 E 0 /E above (Hickman, 2007) E 55% (mol PAR m -2 d -1 ) DCM ~5-10% E 0 (Hickman, 2007) E 1% (mol PAR m -2 d -1 ) Daylength (h) LED output for E 55% μe m -2 d -1

10 CANDYFLOSS, WM-3: The Plan (summary) Measurement outcomes (based on current plan) Short-term (6 h) Long-term (24 h) Short-term (3 h) - particulate C:N:P uptake and dissolved C:N:P release particulate C:P:dSi uptake pico:nano:micro (total) primary production (C) CP:PP (inorganic to organic C production) Algal photo-physiology (a, P max, E k, for pico:nano:micro)** Seasonally, spatially, vertically resolved Cross-reference with (a) Autotroph biomass and community composition (b) Dissolved nutrient stoichiometry (C:N:P:Si) and DOM (c) Production:Biomass ratios for pico:nano:micro (total) (d) Biomass specific dsi uptake (V) and dsi (e) Cell-specific calcification (cell-cf) and ph / Ω C Extras(?): BSi dissolution (P D = P P P N ) (cold BSi incubations, P N ) (Krause et al 2012)

11 CANDYFLOSS, WM-3: Summary and Deliverables Summary - Autotrophic uptake of C:N:P:dSi set particulate and dissolved stoichiometry (H3) - Uptake stoichiometry set by community composition and resource availability - Measure C:N:P:dSi uptake and production of dissolved organic C:N:P Deliverables - Spatially- and seasonally-resolved measurements of the stoichiometry of C, N, P and dsi uptake (H3i-iii) - Spatially- and seasonally-resolved measurements of the stoichiometry of DOC/DOP/DON production (H3-ii, iii) - Spatially and seasonally-resolved community structure (H3ii, H3iii) - Quantification of shelf sea calcification and nitrogen fixation (H1i, H2i) THANKS FOR LISTENING