This approach replaces species with individuals defined by key traits linked through trade-offs. Our goal is to identify traits that best represent organism fitness across ocean life forms, to quantify trade-offs, and to generalize findings beyond experimentally studied species. These insights inform trait-based models to assess ecosystem functions and services.
Classical species-centred ways of describing and modelling marine ecosystems considers how the many species interact with one another. This approach has two problems: (i) it becomes very complex if one wants to embrace the complexity of real systems, with many interacting species; and (ii) interactions in the oceans are not between species, but between individuals.
These two problems are addressed by trait-based approaches that rather than considering species, describe the interactions between individual organisms that are characterized by the few key traits that best describes their Darwinian fitness. The main components of fitness are resource acquisition, survival, and reproduction (cell division rate), so key traits are all related to these fundamental activities, although they play out differently for different life forms.
Trait-based models may be used to quantify ecosystem functions, such as the ability of the ocean to sequester carbon or produce proteins (fish).
An introduction to trait-based approaches, how key traits are identifies, trade-offs quantified, and all incorporated into models of marine ecosystems may be found via the link.
The four components of the trait-based approach, from individuals to ecosystem structure and function.
Key to the development of trait-based approaches is the quantification of organismal trade-offs, essentially the trade-offs between resource acquisition, survival, and growth/reproduction.
I have spent considerable effort in quantifying such trade-offs, mainly for plankton organisms (phytoplankton, flagellates, copepods), using both theoretical and experimental approaches. Focus has been on defense-growth trade-offs and on foraging-defense trade-offs.
The goal has been to achieve a mechanistic understanding of trade-offs (in contrast to correlations between trait-values), as this allows for generalizations beyond the few species one can examine experimentally as well as for simple mathematical formulations that facilitate the incorporation of trade-off relations in models of marine ecosystems. A review of organismal trade-off relations and quantification can be found here
An example of a defense-growth tradeoff. Diatoms thicken their shell in response to grazer cues, which reduces their risk of being consumed by a copepod but at the cost of a reduced cell division rate. From Kiørboe 2024