The ecophysiological basis for co-variability in light-limited and saturated rates of phytoplankton photosynthesis.
Lead Research Organisation:
University of Southampton
Department Name: Sch of Ocean and Earth Science
Abstract
The phytoplankton are a diverse group of single celled organisms which live in the sunlit upper layer of the oceans. These organisms are responsible for the vast majority of the photosynthetic conversion of light energy to chemical energy in oceans. Phytoplankton thus form the basis of the marine food chain and are ultimately responsible for around half the biologically mediated global production of oxygen and removal of carbon dioxide from the atmosphere each year. Due to their key role in controlling the cycles of these major elements, it is important that we understand what controls phytoplankton photosynthesis and ultimately how susceptible these organisms might be to ongoing climate change. A necessary first step in understanding the global impact of phytoplankton is an accurate measure of the amount of carbon they take up. Phytoplankton carbon fixation can be reasonably well approximated as a function of the amount of light available for photosynthesis and the amount of the pigment, chlorophyll, which absorbs this light. Both of these variables can be accurately measured using a number of methods ranging from small scale ship based measurements to large scale year round repeated measurements using earth observing satellites. However, a simplistic treatment of phytoplankton carbon fixation simply as pigment multiplied by light ignores important variability in phytoplankton physiology. Indeed, the efficiency with which phytoplankton convert the light they absorb into carbon varies hugely in the oceans. Much of this variability is currently poorly explained, introducing large uncertainties into our best estimates of the amount of carbon fixed each year. The current study aims to address some of this uncertainty by studying a specific aspect of unexplained variability in phytoplankton photosynthesis in a range of environments. During research cruises we will make simultaneous measurements of the overall rate of phytoplankton light absorption (which is equivalent to the conversion of photons of light to electrons in their photosynthetic apparatus) and the rate of carbon fixation. At the same time we will measure a number of factors which we suspect are responsible for causing the unexplained variability in the ratio of light absorption and carbon fixation. By performing this work we will not only increase our understanding of the physiology of these important organisms, but will also make significant progress towards increasing the accuracy of our current best estimates of phytoplankton carbon fixation.
Publications
Ryan-Keogh TJ
(2012)
THE CYANOBACTERIAL CHLOROPHYLL-BINDING-PROTEIN ISIA ACTS TO INCREASE THE IN VIVO EFFECTIVE ABSORPTION CROSS-SECTION OF PSI UNDER IRON LIMITATION(1).
in Journal of phycology
Ryan-Keogh Thomas J.
(2014)
Understanding the role of chlorophyll fluorescence in nutrient stress
Oxborough K
(2012)
Direct estimation of functional PSII reaction center concentration and PSII electron flux on a volume basis: a new approach to the analysis of Fast Repetition Rate fluorometry (FRRf) data
in Limnology and Oceanography: Methods
Macey A
(2014)
Photosynthetic protein stoichiometry and photophysiology in the high latitude North Atlantic
in Limnology and Oceanography
Lawrenz E
(2013)
Predicting the electron requirement for carbon fixation in seas and oceans.
in PloS one
Fernández-González C
(2020)
Effects of Temperature and Nutrient Supply on Resource Allocation, Photosynthetic Strategy, and Metabolic Rates of Synechococcus sp.
in Journal of phycology
Christopher Moore (Author)
(2011)
Understanding the functional response of the photosynthesis-irradiance relationship within natural shelf sea phytoplankton populations.
Description | Two major fieldwork programmes were undertaken as part of this project. New data collected on both cruises demonstrated how the photosynthetic characteristics of natural phytoplankton communities are altered by environmental forcing. Additionally, the research has contributed to the development of new algorithms for the assessment of phytoplankton photosynthetic rates in situ. Publication of the results of the project are now complete. The project has led to development of new funding opportunities and indisutry collaboration. |
Exploitation Route | Aspects of the work have contributed to new algorithms which have been incorporated within commercial software routines supplied alongside commercial research and monitoring equipment. Knowledge of the environmental controls on oceanic ecosystem processes are potentially of importance for marine policymakers. The work also has potential commercial application within the marine instrument manufacture and monitoring sectors and led to a successful application for funding to develop a new instrument for facilitating autonomous primary production measurements in collaboration with an industry partner. |
Sectors | Environment |
Description | Information from research associated with grant are being used to inform the development of commercial instrumentation and algorithms for the intrepretation of data generated by such instrumentation. A proposal for development of a new system to facilitate in situ autonomous application of primary production measurements was submitted and funded (see NE/P020844/1). |
First Year Of Impact | 2017 |
Sector | Environment |
Impact Types | Economic |
Description | Marine Autonomous Sensors Call |
Amount | £900,000 (GBP) |
Funding ID | NE/P020844/1 |
Organisation | Natural Environment Research Council |
Sector | Public |
Country | United Kingdom |
Start | 07/2017 |
End | 07/2017 |
Description | Collaboration with Chelsea Technologies Group |
Organisation | Chelsea Technologies Group |
Country | United Kingdom |
Sector | Private |
PI Contribution | Knowledge exchange, contribution of data and development of data analysis routines |
Collaborator Contribution | Loan of equipment. Advice on opperation |
Impact | Co-written paper: Oxborough et al. 2012 |
Description | Continued collaboration with CTG limited as part of the STAFES-APP development project |
Organisation | Chelsea Technologies Group |
Country | United Kingdom |
Sector | Private |
PI Contribution | Important collaborations with between CTG and University of Southampton are ongoing, in particular relating to the development of new autonomous sensor systems. UoS led the development of the proposal which currently funds this ongoing work. |
Collaborator Contribution | The project partner brings crucial technical expertise and background IP to the project. |
Impact | Hughes et al. (2018) Roadmaps and Detours: Active Chlorophyll-a Assessments of Primary Productivity Across Marine and Freshwater SystemsEnviron. Sci. Technol., 2018, 52 (21), pp 12039-12054 DOI: 10.1021/acs.est.8b03488 |
Start Year | 2017 |
Description | Continued partnership with CTG generating new funding applications |
Organisation | Chelsea Technologies Group |
Country | United Kingdom |
Sector | Private |
PI Contribution | Continued interactions including feedback on instrument design. Preparation and submission of grant proposal for new instrument to facilitate autonomous in situ measurements |
Collaborator Contribution | Loan of equipment and advice on operation of existing equipment |
Impact | Outputs as currently listed in previous submissions |