Director

Secretariat

 

Herwigstraße 31

27572 Bremerhaven

Telephone: +49 471 94460 101

Fax: +49 471 94460 199

wencke.griemsmann@thuenen.de


Shedding light on the South Atlantic: a status assessment

Project

 (c) Triatlas

South and Tropical Atlantic climate-based marine ecosystem prediction for sustainable management

In the TRIATLAS project, scientists from Europe, Brazil and southern Africa are comprehensively investigating the current state, driving forces and potential future of South Atlantic regions.

Auftaktkonferenz des TRIATLAS-Projektes in Bergen, Norwegen.
Kick-off meeting of the TRIATLAS-Project in Bergen, Norway. (© Andreas H. Opsvik)

Background and Objective

In the TRIATLAS project with 35 participating institutions, the South Atlantic is intensively studied – from ocean currents, phyto- and zooplankton to fish and marine mammals at the top of the food chain. At the Thünen Institute for Sea Fisheries, we are working in a sub-project on mesopelagic fish.

The Mesopelagic is the twilight zone of the open ocean in 200 to 1000 meters water depth, above the actual deep sea. The little sunlight that reaches these depths is not sufficient for photosynthesis. The fish are adapted to these conditions, among other things with low metabolism, light organs, and nocturnal migrations to shallower depths. The ecological importance of the mesopelagic fauna is often underestimated. We analyse the biodiversity of these communities, their distribution patterns and their food relationships in the southern Atlantic.

Our aim is to close knowledge gaps about the state and seasonal dynamics of community structures, vertical migrations and food webs of mesopelagic fish in the South Atlantic. This knowledge helps to understand how the mesopelagic is influenced by fisheries and climate, what relevance it has as a food source for commercial fish species, and what role it plays in the Earth's carbon pump.

Approach

On the basis of survey data, descriptive quantitative modelling is carried out, using size-based and trait-based approaches:

  • Fundamental ecological processes revolve around the body size of organisms. Environmental factors such as temperature affect body size, predator-prey relationships depend on the size ratio.
  • Traits are functional features of organisms, that determine how they interact with their environment. We use traits that characterize mobility and feeding types.

We investigate how size spectra and functional diversity vary between key regions and along environmental gradients. Organism sizes and traits are also needed to establish food web structures.

Data and Methods

  • On past research cruises and in new research projects (e.g. AWA, PREFACE, TRAFFIC), large-scale surveys were carried out with comprehensive fish size measurements. These two data groups are now analysed under new aspects.
  • Hydroacoustics (underwater echo sound) are used to observe daily vertical migrations of mesopelagic fish. With different sound frequencies, the proportion of different size classes can be quantified.
  • For filling gaps in the data, new scientific catches with special nets are carried out.
  • Trait information from the literature is supplemented with own data.

Our Research Questions

What are the mean state and seasonal variability of

  • diversity and size structures,
  • vertical migrations and
  • trophic relationships

in the mesopelagic fish communities of the South Atlantic?

How do these depend on external factors such as the trophic status of the environment?

How do the community characteristics differ between ecosystems of important key areas?

How will climate change affect the fish communities of the open ocean?

Links and Downloads

triatlas.w.uib.no

Thünen-Contact


Involved Thünen-Partners


Involved external Thünen-Partners


Duration

6.2019 - 5.2023

More Information

Projekt type:
Project funding number: 817578
Funding program: EU – Horizon 2020 – Societal Challenge "Food Security, Sustainable Agriculture and Forestry, Marine, Maritime and Inland Water Research and the Bioeconomy"
Project status: ongoing

Publications

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