Influence of phytoplankton size structure on ocean carbon cycling and on ocean colour

Bob Brewin1,2,3, Shubha Sathyendranath1,3,

with contributions from Giorgio Dall’Olmo1,3, Icarus Allen1,3, Lee De Mora1 , Momme Butenschon1

1 Plymouth Marine Laboratory (PML), Prospect Place, The Hoe, Plymouth PL1 3DH, UK2 ESA Changing Earth Science Network post-doctoral fellowship of the STSE program

3 National Centre for Earth Observation, PML, Plymouth PL1 3DH, UK

Earth system modelling is used for predicting and determining how the ocean and land sinks may respond in the future. These models are constrained / improved by comparison and verification with observations.

http://earthobservatory.nasa.gov

Importance of Phytoplankton

The ocean contributes to ~1/4 of anthropogenic CO2 (Le Quéré et al. 2009)~1/2 of net global primary production (Longhurst et al. 1995)

Evidence of declining ocean CO2 sink(Canadell et al. 2007) Future changes are highly uncertain!

Source ESA: http://www.esa.int/esaEO/SEMB88KX3XG_index_1.html

Phytoplankton biomass and climate

see also papers by Behrenfeld et al. (2006) Nature and Martinez et al. (2009) Science

A number of biogeochemical models use a size class partitioning

Cell size

Nutrient uptake

Light absorption

Sinking rate

Exported production

Phytoplankton physiology

Metabolic rates

Marine food-web

An integrative approach to describing

phytoplankton function and structure in relation to marine

bio-geochemical cycling

(Marañón 2009).

Influence of size structure on carbon cycle

Phytoplankton size structure

Brewin et al. (2010) Ecol. Model.Brewin et al. (2011) Appl. Optics

Brewin et al. (2012a) Opt. ExpressBrewin et al. (2012b) Deep Sea Res. II

Brotas et al. (2013) Rem. Sens. Environ.Brewin et al. (2014a) Deep Sea Res. IBrewin et al. (2014b) J Geophys. Res.

Lin et al. (2014) Mar. Pollut. Bull.

Influence of size structure on ocean colour

PICO<2 μm

Influence of size structure on ocean colour

NANO2-20 μm

Influence of size structure on ocean colour

MICRO>20 μm

Influence of size structure on ocean colour

Influence of size structure on ocean colour

Influence of size structure on ocean colour

Influence of size structure on ocean colour

Satellite estimates of size structure

Brewin et al. (2010) Ecol. Model.

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Phytoplankton size and climate

Brewin et al. (2012) Deep-Sea Res. II

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Phytoplankton size and climate

Brewin et al. (2012) Deep-Sea Res. II

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Model comparison EURO-BASIN Programme

Holt et al. (2014) Progress in Oceanography

MEDUSA

PISCES ERSEM

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Model comparison EURO-BASIN Programme

Holt et al. (2014) Progress in Oceanography

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Model data assimilation

Xiao and Friedrichs (2014) J Geophys. Res

Before assimilation

After assimilation

When implementing assimilative models with

more than one phytoplankton size class, the assimilation of size-fractionated chlorophyll provides an advantage over the assimilation of

total chlorophyll.

- Phytoplankton size structure is an importance component of the ocean carbon cycle and other biogeochemical cycles.

- Phytoplankton size structure has a direct influence on variations in reflected light within the visible electromagnetic spectrum.

- These variations are implicitly build into standard empirical algorithms designed to estimate the total chlorophyll concentration as a function of reflected light.

- These variations can be revealed through simple empirical relationships between total chlorophyll and size structure.

- Satellite estimates of size structure can improve our understanding of the relationship between physical variables and size structure, and are useful for validation of, and assimilation into, multi-phytoplankton biogeochemical models.

- This will ultimately improve our predictions and understanding of how the ocean ecosystem is responding to changes in climate.

Summary

We thank contributors, crew and staff involved with the collection of all in situ data, particularly for AMT and NOMAD.

We thank all data contributors without whom this work would not be possible. In particular, Ray Barlow, Vanda Brotas and

Jeremy Werdell.

We thank the ESA Changing Earth Science Network of the STSE program, NCEO and ESA OC-CCI project for financial

support.

Acknowledgements