Translation of Optical Measurements into particle Content, Aggregation & Transfer


Sinking particles transport organic carbon to the deep sea, where they form the base of life. The magnitude of particle export and the rate at which particles are consumed determine carbon sequestration in the oceans, and directly influence atmospheric carbon dioxide concentrations and global climate. Traditionally, sinking particles have been collected using sediment traps. However, the limited spatial and temporal coverage of sediment traps have led to new technologies that focus on optical measurements to allow the collection of large data sets describing both frequencies and types of sinking particles. These can be used from ships or installed on remote platforms, promising greater spatial and temporal coverage. Yet, whilst technologies to image particles have advanced greatly during the last two decades, techniques to analyze the often immense data sets have not. One short-coming is the translation of optical particle properties (e.g. the image) into particle characteristics such as carbon content and sinking speed. Moreover, different devices often measure different optical properties, leading to difficulties in comparing results. This working group aims to bring together experts in observation, experimentation, theoretical modelling, and data analyses to systematically improve the process of converting in-situ particle measurements to global export estimates. Final outcomes will include publications detailing intermediate steps and a framework outlining the most efficient way of converting large volumes of particle measurements into export estimates. The output of this working group should have high impact on future ocean research by enabling efficient use of the rapidly developing field of optical sensors.

Terms of reference

The working group will focus on the use of optical instruments to size and otherwise characterize particles, thereby facilitating their use to characterize organism concentrations and distributions, particle flux and export, and the interactions between particle and organisms. It aims specifically to

  1. Review current devices that optically measure particles, and document the capabilities and limitations of each device.
  2. Make vocabularies more transparent and interoperable using international standards.
  3. Define key parameters for interpretation of optical information, and recommend which optical measurements are useful for characterizing particle type, interactions and export.
  4. Evaluate various techniques and algorithms for the conversion of optical observation into particle type, size, concentration, mass, composition, and fluxes, and recommend ways of improving our understanding of the relationships between these properties.
  5. Promote sharing of software examples and codes, placed on a public repository.
  6. Improve the visibility and usage of data by hosting an inventory of published datasets.

We are funded by the Scientific Committee on Oceanic Research.


sari-roundSari Giering (Researcher at the National Oceanography Centre, Southampton, UK)

Sari is a marine biogeochemist with research focus in carbon export, zooplankton ecology and particle dynamics. She uses a combination of field measurements, models and data synthesis to better constrain the ocean carbon cycle. She is the chair of TOMCAT, so please feel free to get in touch about TOMCAT!


klas-roundKlas Ove Möller (Researcher at HZG, Institute of Coastal Research / Operational systems, Germany)

Klas’ expertise is in optical sampling methods and underwater technologies (e.g. Video Plankton Recorder, Remotely operated vehicles, TRIAXUS) and automatic image classification. He is interested in biological and physical forcing on plankton and particle distribution patterns from small- to meso-scale and carbon flux from shelf to ocean basins. Get in touch.


catarina-roundCatarina Marcolin (Assistant Professor at the Federal University of the South of Bahia, Brazil)

Catarina uses optical systems such as the LOPC and ZooScan to automatically detect and measure plankton and particles size distributions in situ and ex situ. She is currently interested in how to provide realistic estimates of particle fluxes from LOPC data.
Get in touch.


morten-roundMorten Iversen (Head of Helmholtz Young Investigator Group SeaPump at the Alfred Wegner Institute, Germany)

Morten’s research focuses on understanding how food web composition influences particle export dynamics, specifically how particle size and composition determine sinking speed and particle remineralization. His group is developing several new camera systems and new in situ methods to determine particle sizes, abundance, sinking velocities, and to collect intact marine particles.


sandy-roundSandy Thomalla (Principal Scientist at Southern Ocean Carbon and Climate Observatory (SOCCO), CSIR, South Africa)

Sandy’s research focuses on linking optical measurements (scattering, absorption, attenuation) with phytoplankton community characteristics (biomass, species composition, carbon content and size structure). An optical characterization of the plankton community contributes towards the development of improved ocean colour algorithms that provide new insight into Southern Ocean ecosystem function and export potential. She further uses bio-optics sensors on floats with upward facing transmissometers to estimates particle flux.


george-roundGeorge A Jackson (Professor of Oceanography Emeritus, Department of Oceanography, Texas A&M )

George has in developed models of particle aggregation and disaggregation to predict particle size distributions and fluxes in the ocean. He has also worked with multiple particle measurement systems to test the models. As part of this effort, he compared observations made by different particle sizing techniques. Most recently, he has been working with Dave Checkley of Scripps to interpret hourly profiles of particle size distributions at 2 m depth resolution made with the SOLOPC system.


sunnje-roundSünnje Basedow (Researcher at UiT – The Arctic University of Norway, Tromsø, Norway)

Sünnje’s research focuses on how biological-physical interactions shape spatial patterns of zooplankton and energy flow within marine pelagic food webs. She uses the laser optical plankton counter (LOPC) for enhanced spatial resolution in sampling, and to analyse ecological processes based on size spectrum theories. She has compared the LOPC to the VPR and Multinet for intercalibration of instruments.


Lionel Guidi
(Researcher at Laboratoire d’Océanographie de Villefranche sur Mer, France)

Lionel’s expertise is optical sampling measurements (especially the Underwater Vision Profiler, UVP), automatic particle recognition, large data compilation and analysis, and conversion of imaging data into flux estimates. Recent efforts included a global synthesis of particle size distribution and related estimate flux profiles as calculated from the UVP.


tom-roundTom Trull (Professor of Marine Biogeochemistry, Australia)

Tom Trull leads the Australian Climate and Ecosystems Cooperative Research Centre Carbon Program and the Australian Integrated Marine Observing System Southern Ocean Time Series (SOTS) set of autonomous moorings for climate and carbon cycle research. He has expertise in isotope geochemistry, marine biogeochemistry, and chemical oceanography. His work on quantifying the marine biological carbon pump includes bio-optical measurements from profiling floats and towed bodies, deployment of moored and free-drifting sediment traps, imaging of particles collected in gel-filled traps, and determination of in-situ particle sinking rates using indented rotating sphere sediment traps operated as settling tubes.


nathan-roundNathan Briggs (Postdoctoral Fellow at Laboratoire d’Océanographie de Villefranche-sur-Mer, France)

Nathan uses simple optical measurements (scattering, fluorescence, absorption) aboard autonomous platforms to study the dynamics of particles in the ocean and their effects on ocean biogeochemistry. His current focus is extracting particle size information from high-frequency variability in these optical measurements in order to identify particle aggregation and the sinking flux of large particles through the mesopelagic.


emma-roundEmma Cavan (Postdoc at University of Tasmania)

Emma collects particles from in situ for ship-board experiments to study what controls and influences the efficiency of the biological carbon pump. This involves using images of particles and more recently the FlowCAM to measure particles sinking rates. This method also gives high quality, high magnification images of particles to infer particle type and compare to sinking rates. Get in touch.


dhugal-roundDhugal Lindsay (Senior staff scientist at Japan Agency for Marine-Earth Science and Technology)

Dhugal uses optical systems such as the VPR, ZooScan, ROV video cameras (to 8K), still cameras, light field cameras, a DPI plankton imager (an in situ schlieren system) etc for in situ research on gelatinous zooplankton, for taxonomy, and for marine snow studies.


andrew-roundAndrew McDonnell (Assistant Professor at the University of Alaska Fairbanks, USA)

Andrew’s research focuses on assessing the distributions and dynamics of marine particles throughout the oceans. He uses a wide range of field based methods including in situ imaging, sediment traps, and in situ particle incubations to investigate particle size distributions, sinking fluxes, sinking velocities, remineralization, flux attenuation, and lateral transport.