Department of
Biological Sciences

Researcher, PhD
Tom J. Langbehn

Research interests

I am a quantitative ecologist with a keen focus on global change ecology, evolution, and sustainable fisheries. I specialize in pelagic ecology, where I explore how the environment and species interact in shaping traits, abundance, distribution, and behavior of zooplankton and fishes. Key facets of my research include light and vision in foraging interactions, physiology and bioenergetics, and life-history theory. I have a special fascination for polar (high latitude) ecosystems, drawn to their extreme seasonality, and a keen interest in life within the perpetual twilight of the mesopelagic zone.


Research Approach

I aim to understand how nature works at its core while also finding practical solutions, such as ensuring the sustainable use of marine resources. As an "ocean-going modeler," my research integrates theory and modeling with observations and experiments. While my focus is often on macroecological aspects like large-scale biogeographic patterns, trait distributions, and interactions, my work typically starts at the individual level. I develop coupled bio-physical simulation models that combine detailed bioenergetic calculations at the individual level with large-scale environmental datasets. To be explicit about physiological mechanisms or modes of prey detection allows rich patterns to emerge in models from the interaction of individuals. These predictions can then be confronted with observational data, allowing us to make strong inferences about population and ecosystem-level consequences.



Current projects

The fundamental role of mesopelagic fishes for the structure and change of Northeast Atlantic marine ecosystems

Role: Postdoc, contributed to idea andwriting, Project lead: Christian Jørgesen (UiB), Funder: Norges forskningsråd #294819

Within this project, I currently work on two different aspects:

  1. How are vertical migration strategies of mesopelagic fish affected by the extreme seasonality in light in high-latitude ecosystems and what are the ecosystem consequences? Using mechanistic models that link light-dependent foraging interactions with temperature-dependent physiology, we show for the first time in vertebrates that seasonality in light constitutes a barrier to range shifts that, importantly, will not move northwards with warming.


  2. Langbehn T, Aksnes DL, Kaartvedt S, Fiksen Ø, Ljungström G, Jørgensen C. 2022.
    Poleward distribution of mesopelagic fishes is constrained by seasonality in light
    Global Ecology and Biogeography. 31: 546-561. [ doi:10.1111/geb.13446 ] [ open access ] [ pdf ]
    Langbehn TJ, Aksnes DL, Kaartvedt S, Fiksen Ø, Jørgensen C. 2019.
    Light comfort zone in a mesopelagic fish emerges from adaptive behaviour along a latitudinal gradient
    Marine Ecology Progress Series. 623: 161-174. [ doi:10.3354/meps13024 ] [ open access ] [ pdf ] [ Online supplement ]


  3. How are mesopelagic and epipelagic ecosystems linked? I use the case of Greater argentine (Argentina silus), a little studied, but already commercially fished bentho-pelagic deep-water species to explore the emergent niche for advective feeding along gradients of topography, light, and advection.


Future Fisheries — How can fisheries contribute more to a sustainable future?

Role: Collaborator, contributed to development of ideas and background, Project lead: Katja Enberg (UiB), Funder: Norges forskningsråd #326896

In this project, our primary objective is to deliberately ignore current practices and beliefs as we reimagine the role of fisheries if UN’s 2030 Agenda for Sustainable Development, the Paris Agreement on Climate Change, and the Convention on Biological Diversity were allowed to define the objective as maximizing food production while minimizing footprint.

This is broken down into three secondary objectives:

  1. Use food systems analysis of fisheries as embedded within marine ecology to find ways fisheries can produce more food at reduced climate impact.
  2. Compare fisheries with other food systems to identify where seafood may alleviate global trade-offs between planetary boundaries.
  3. Measure and analyze how values, psychological mechanisms, and ethics may foster action and a bottom-up and fact-based transition towards sustainability.


Deep Impact — The impact of artificial light on arctic marine organisms and ecosystems during the polar night

Role: Collaborator, Project lead: Jørgen Berge (UiT), Funder: Norges forskningsråd #30033

As part of this project, I am currently analyzing acoustic observations from a large-scale field experiment conducted during the Polar Night Cruise in January 2020 and 2022 aimed at understanding the bias of artificial light on ship-based sampling.

Dunn M, McGowan-Yallop C, Pedersen G, Falk-Petersen S, Daase M, Last K, Langbehn TJ, Fielding S, Brierley AS, Cottier F, Basedow SL, Camus L, Geoffroy M. In press.
Model-informed classification of broadband acoustic backscatter from zooplankton in an in situ mesocosm
ICES Journal of Marine Science. [ doi:10.1093/icesjms/fsad192 ]


Nansen Legacy — Phenotypic plasticity and individual variability in life history traits

Role: Researcher, Project lead: Marit Reigstad (UiT), Subtask lead: Øystein Varpe (UiB), Funder: Norges forskningsråd #276730

As a contribution to Research Focus 4 "The Future Barents Sea" I have analyzed long-term mesozooplankton community survey data to test the hypothesis that reduced visual predation, and hence increased survival in dim habitats, explains the distribution of large copepods in the Barents Sea.

Langbehn TJ, Aarflot JM, Freer JJ, Varpe Ø. 2023.
Visual predation risk and spatial distributions of large Arctic copepods along gradients of sea ice and bottom depth
Limnology and Oceanography. 68: 1388-1405. [ doi:10.1002/lno.12354 ] [ open access ] [ pdf ]


Glacier troughs as biodiversity and abundance hotspots in Arctic and subarctic regions

Role: Collaborator, Project lead: Maxime Geoffrey (Fisheries and Marine Institute of Memorial University of Newfoundland), Funder: ArcticNet

In this project we will use large datasets comprising seafloor mapping and imagery, acoustic-trawl surveys, paleoceanography, and moorings to test the following two hypotheses:

  1. Glacial troughs allow deep waters to flow onto continental shelves, creating hotspots of abundance and biodiversity for pelagic and benthic organisms
  2. Changes in hydrography, sea-ice, and productivity related to climate change may result in a decoupling between pelagic production and benthic habitats and biodiversity loss in some Arctic areas.
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