T. Holtrop MSc

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PhD researcher


The oceans can be considered the true lungs of our planet, producing more than half of the oxygen and absorbing the majority of the carbon dioxide (CO2) in the atmosphere. Phytoplankton, microscopic algae that live in our oceans, rivers and freshwater lakes are responsible for these processes. The ability to capture changes in the dynamics of phytoplankton is essential in order to understand how the biological, chemical and physical processes of our oceans are affected now and in the future.

As a PhD researcher at the department of Water and Climate Risk I have the exciting opportunity to develop new methodologies to monitor our oceans’ health on a global scale. Satellite sensors such as NASA’s SeaWiFs and MERIS and the more recent OLCI sensor onboard ESA’s Sentinel-3 satellite have opened up the possibility to get a birds-eye view of our oceans and track changes over decadal scales. My research will revolve around the development of a physical model (forward model) that is able to reconstruct (as closely as possible) the signal that is acquired by ocean colour satellites as a function of the biological (phytoplankton) and chemical constituents of the ocean. The output of our physical model will be compared to the actual satellite measurements (model inversion) in order to estimate water quality parameters such as the concentration of different phytoplankton groups in the oceans. In this manner we hope to get a better understanding of the biological and chemical evolution of our oceans.


My interests lie in the development of numerical and statistical models to address environmental questions. In recent years I have focussed on solving spatial explicit problems by combining satellite observations and data-mining techniques. I have a strong interest in a multidisciplinary approach where environmental sciences, computer science and data-analyses find common ground.

Academic training

2013-2016MSc Oceanography, University of Amsterdam, Amsterdam, The Netherlands
2015Research intern, Global Change Institute, University of Queensland, Brisbane, Australia
2014-2015Research intern, NIOZ Royal Netherlands Institute for Sea Research, Yerseke, The Netherlands
and Institute for Biodiversity and Ecosystem Dynamics, University Amsterdam, The Netherlands
2006-2009BSc Neuroscience, University of Amsterdam, Amsterdam, The Netherlands

Professional employment history

PhD researcher, dept Water and Climate Risk, Institute for Environmental Studies (IVM),
Vrije Universiteit Amsterdam, The Netherlands
Visiting researcher, Institute for Biodiversity and Ecosystem Dynamics,
University of Amsterdam, The Netherlands
2013-2014Ecological research volunteer, The Ocean Cleanup, Delft, The Netherlands

Selected publications

González-Rivero, M., Beijbom, O., Rodriguez-Ramirez, A., Holtrop, T., González-Marrero, Y., Ganase, A., Roelfsema, C., Phinn, S. & Hoegh- Guldberg, O. (2016). Scaling up Ecological Measurements of Coral Reefs Using Semi-Automated Field Image Collection and Analysis. Remote Sensing, 8(1), 30. http://doi.org/10.3390/rs8010030.

Zuijderwijk, R., Walworth, N., Schmidt, K. & Holtrop, T. (2014). Phytoplankton. In Slat, B. (ed.), How the Oceans Can Clean Themselves, a Feasibility Study (pp. 314-319). The Ocean Cleanup, Delft, The Netherlands. Retrieved from: https://www.theoceancleanup.com/fileadmin/media-archive/Documents/TOC_Feasibility_study_executive_summary_V2_0.pdf