NSFGEO-NERC: Novel imaging, physiology and numerical approaches for understanding biologically mediated, unsteady sinking in marine diatoms

Lead Research Organisation: Marine Biological Association of the United Kingdom
Department Name: Marine Biology

Abstract

Diatoms account for up to 40% of oceanic primary production sinking behavior is an important species-specific property that can determine the community composition, aggregate formation and the amount of material lost to depth. Although they are unable to swim, diatoms are far from passive, controlling their sinking speeds over long time scales in response to environmental factors, such as nutrient concentration, irradiance, and temperature and biological factors, such as reproductive state. Early work on diatom sinking demonstrated the capacity of diatoms to regulate their buoyancies over hours to days in response to changing environmental conditions. However, some species can also control their sinking speeds over much shorter time scales of seconds, performing a recently discovered unsteady sinking behavior. To date, diatom suspension studies have largely used bulk measurements such as settling columns (SETCOLSs) due to the ease of measurement and assumption that bulk rates adequately capture the essential characteristics of this group. We offer evidence that this assumption is not justified and propose a series of laboratory experiments using advanced optical techniques, physiological tools that measure processes around single cells and numerical approaches to investigate taxonomic and morphological variability in unsteady sinking over a range of environmental conditions and examine the implications the observed differences.

This project will leverage an interdisciplinary collaboration involving innovative optical techniques, advanced cell physiology tools and numerical modeling approaches to characterize diatom suspension properties at the individual cell level. The shift from time-averaged sinking measurements to small time scales has indicated that sinking speeds can vary orders of magnitude over seconds. We will address several aspects of instantaneous velocity control behavior in order to determine the adaptive significance of unsteady sinking. This novel observation suggests that models of diffusion limited transport need to be revised in order to accommodate species-specific differences. We will use individual cell level experimental data from a variety of species and environmental conditions to inform 3D numerical models which will be used to characterize what, if any, adaptive significance unsteady sinking in diatoms has and why it may be constrained to certain taxonomic groups.

Publications

10 25 50

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Brownlee C (2023) Regulation and integration of membrane transport in marine diatoms. in Seminars in cell & developmental biology

 
Description We have been able to measure the diffusion boundary layer around single phytoplankton cells and detemrine how this is influenced by different flow rates. This has enabled us to understand the potneital benefits of dynamic sinking behaviour that is observed in large centric diatoms as a means to enhance nutrient acquisition. We now have empirical evidence that shows for the first time how the diffusion boundary layer is influenced by sinking behaviour.
Exploitation Route The funding outcomes will researchers to develop furthe rnumerical models to understand the processes that drive compettion between phytoplankton types in the ultra-low nutirent waters that span much of our global oceans.
Sectors Environment

Manufacturing

including Industrial Biotechology

 
Title Microelectrode assessment of diffusion boundary layer around single phytoplankton cells 
Description We have developed techniques to measure the extent of the boundary layer around single phytoplankton cells using microelectrodes. This has allowed us to determine how the diffusion boundary differs with cell size and influences nutirent uptake in marine phytoplankton. 
Type Of Material Technology assay or reagent 
Year Produced 2023 
Provided To Others? No  
Impact ongoing - awaiting publication 
 
Description Imaging systems to detect phytoplankton sinking in situ 
Organisation University of Plymouth
Country United Kingdom 
Sector Academic/University 
PI Contribution The MBA partner has identified unique sinking behaviour in phytoplankton. They will collaborate with the partners to develop new technologies to observe these phytoplankton in situ.
Collaborator Contribution The University of Plymouth partner will develop their holographic imaging systems for direct visualisation of phytoplankton sinking behaviour, both in the laboratory and in situ
Impact Ongoing
Start Year 2023
 
Description Sinking of Phaeocystis blooms 
Organisation University of Bristol
Country United Kingdom 
Sector Academic/University 
PI Contribution We have developed a new collaboration using the techniques developed in this award to study the export of Phaeocystis blooms from the surface ocean. Phaeocystis is a bloom-forming alga that form nuisance blooms in many coastal areas due to the vast ammounts of foam they produce. We will apply the techniques use din this award to detemrine sinking rates of Phaeocystis colonies to understand how these blooms contribute to carbon flux to the deep ocean.
Collaborator Contribution The collaborators will use the data that we have generated to develop numerical models to assess carbon fluxes associated woth Phaeocystis blooms.
Impact None yet
Start Year 2023