2014 SSB AGM Liverpool
CANDYFLOSS, Work Module 3
The Autotrophs
Alex Poulton
(NOC)
Anna Hickman
(University of Southampton)
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,
M Stinchcombe
*James Fox (SSB PhD)
A Rees, D Clark, G Tarran,
C Widdicombe
*Kieran Curran (SSB PhD)
CANDYFLOSS, WM3: Hypothesis 3
C, N, P
Si
POC ,
PON, POP
BSi,
CaCO3
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.
CANDYFLOSS, WM-3: Plankton Succession
Sp
Wi
Su
Fa
Widdicombe et al. 2010
Western English Channel
Observatory (L4)
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. 2004 L&O
- Expt. Bloom in Randers Fjord, Denmark
CANDYFLOSS, WM-3: Taxa specific elemental ratios
Tend to be N rich
under nutrient
replete conditions
(Relative to Redfield)
Bertilsson et al. 2003 L&O
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
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 (NO3, NH4) uptake and DON production (15N)
(Clark et al. 2011)
Short-term (6 h) DIC and DIP uptake and DOC and DOP production (14C,
33P)
(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 (32Si) (also DIP uptake via daughter 32P)
(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 (14C)
(Maranon et al. 2001; Poulton et al. 2006b)
Daily (24 h) Primary production and Calcite production (14C)
(Poulton et al. 2006, 2010, 2013)
Short-term (2-3 h) Size-fractionated Photosynthesis v Irradiance Curves (14C)* (SSB PhD)
(Lorenzo et al. 2005; Hickman et al. 2012)
CANDYFLOSS, WM-3: The Plan (details)
Abandoning on-deck incubators
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 pCO2 experiments
- need to reconstruct in situ light levels (seasonal, depth)
Spring
Summer
Fall
Notes
Eabove (mol PAR m-2 d-1)
36.8
43.2
9.4
20-25% RSD, 8-day satellite
E0 (mol PAR m-2 d-1)
23.8
27.9
6.1
Based on 0.65 E0/Eabove
(Hickman, 2007)
E55% (mol PAR m-2 d-1)
13.1
15.3
3.3
DCM ~5-10% E0 (Hickman, 2007)
E1% (mol PAR m-2 d-1)
0.2
0.3
0.1
Daylength (h)
14
16
9
LED output for E55%
260
305
65
μE m-2 d-1
CANDYFLOSS, WM-3: The Plan (summary)
Measurement outcomes (based on current plan)
Short-term (6 h) –
particulate C:N:P uptake and dissolved C:N:P release
Long-term (24 h) –
particulate C:P:dSi uptake
pico:nano:micro (total) primary production (C)
CP:PP (inorganic to organic C production)
Short-term (3 h) -
Algal photo-physiology (a, Pmax, Ek, 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 / ΩC
Extras(?):
BSi dissolution (PD = PP – PN) (cold BSi incubations, PN)
(Krause et al 2012)
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