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Hereon researchers develop innovative method to calculate predator-prey relationships more precisely
Marine food webs are highly complex. Until now, researchers have been unable to understand exactly how they are affected by climate change, overfishing and other threats. Scientists at the Helmholtz-Zentrum Hereon in Geesthacht have now achieved a breakthrough. They have developed a new computer model that can be used to simulate food webs more accurately than ever before. The work, which has been published in the journal Nature Ecology & Evolution, opens up new perspectives in the field of marine conservation.
“Until now, there has been a lack of computer models that could realistically simulate the reaction of food webs to fishing, climate change and other influences with a manageable amount of effort,” says Dr Ovidio Fernando García-Oliva, ecosystem modeler at Hereon and lead author of the study. There are already computer models that simulate the complicated interdependencies of food webs according to the principle of “who eats whom”. But they are too imprecise. García-Oliva has developed a new method together with the head of the ecosystem modeling working group at Hereon, Prof. Kai Wirtz.
Conventional models are too imprecise
To understand what this new computer model can do, it is important to understand the limitations of previous approaches. There are species-specific and size-based models. The former establish the individual relationships between hundreds and thousands of algae and animal species. Herring, for example, eat fish larvae and small crustaceans, small crustaceans eat different algae, and so on. "However, our knowledge is still far too incomplete for such a complex representation. For many organisms in the sea, we still don't know what they eat, how much they eat or who eats them," says Wirtz. Size-based models, on the other hand, are usually based on just one simple rule: “Predators eat prey that is around five to ten times smaller in diameter than themselves.” But this rule, says García-Oliva, only applies to around 50 percent of all marine life. Therefore, it is not sufficient to simulate food webs in their entirety.
Hereon researchers discover new prey strategies
The scientists from Geesthacht have integrated two further key feeding strategies of marine organisms into a size-based model. Firstly: “Predators eat significantly larger prey, regardless of their own size”. This includes, for example, orcas, which attack significantly larger whales. Second: “Predators eat significantly smaller prey whose size range does not vary with their own size”. These are, for example, baleen whales, which filter feed on krill regardless of age, size or species, or small crustaceans, which feed on the tiny particulate remains of dead animals and algae. These two feeding patterns are found in crustaceans, fish, jellyfish and also marine mammals - in other words, in every species group. So they are well suited to comprehensively describe food webs.
Better understanding oceans as complex systems
These two prey strategies have so far only been partially taken into account in species-specific models. Namely, when species are explicitly known to eat larger species, such as orcas. García-Oliva and Wirtz have combined the two strategies into rules for the first time, described them formally and quantitatively and then integrated them into a size-based model. This allows them to map 85 to 90 percent of all predator-prey relationships in the sea. According to Wirtz, this is accurate enough to use the model for future simulations - for example, to understand how marine habitats react to climate change. In addition, the model is also suitable for predicting how a marine habitat will change if it is placed under protection and fishing is prohibited. “Such findings are extremely important for the future management of marine protected areas,” says Wirtz. And they help researchers to better understand the coasts and oceans as complex systems and to model them digitally.
Dr Ovidio Fernando García-Oliva
Scientist
Institute of Coatsal Systems - Analysis and Modeling
Department of Ecosystem Modeling
Tel: +49 (0)4152 87-1818
Mail: ovidio.garcia@hereon.de
Prof. Dr. Kai Wirtz
Head of Department
Institute of Coatsal Systems - Analysis and Modeling
Department of Ecosystem Modeling
Tel: +49 (0)4152 87-1513
Mail: kai.wirtz@hereon.de
https://www.nature.com/articles/s41559-025-02647-1
https://hereon.de/institutes/coastal_systems_analysis_modeling/index.php.en
The relationship between predators and their prey in the sea is very complex and difficult to grasp ...
Hereon/iStock
Hereon
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The relationship between predators and their prey in the sea is very complex and difficult to grasp ...
Hereon/iStock
Hereon
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