Phytoplankton exhibit a high diversity of carotenoids, yet most of them are broadly labeled as photoprotective and antioxidants indistinctly, constituting somewhat of a paradox. Comparative photochemistry of carotenoids has revealed structural trade-offs linked to specialized cellular roles that vary in prevalence across life strategies such as the CSR: organisms with co-adapted traits optimized to forcings of competition for resources (Competitive, C), constraints on production (Stress-tolerants, S), and disturbances (Ruderals, R). Here, we hypothesize that different life strategies of phytoplankton prioritize different structure-derived cellular roles of carotenoids: Ruderals with carotenoids that efficiently redirect and dissipate the energy flux (NPQ) in the large light gradient of mixed water columns; Stress-tolerants with high ³chl and ¹O₂ (oxidative excited states) quenching carotenoids to minimize photodamage under nutrient depletion; and Competitors with free radical quenching carotenoids to deal with the oxidative conditions of high light driven photosynthesis. We classified the carotenoids into cellular roles based on structure and tested their link to life strategies in lake phytoplankton and cultures. R-strategists had elevated NPQ and light harvesting carotenoid fractions; S-strategists had more ¹O₂ and ³chl quenchers; free radical quenchers were present in C-cultures and CSR-balanced lakes; and ³chl quenchers were predominant in C-strategists. Overall, we found support that the carotenoid groups reflect the organismal life strategies relationship to light.

Primary Presenter: Bruno Cremella, Université de Sherbrooke (brunocremella@gmail.com)

Authors:

Bruno Cremella, Département de géomatique appliquée, Université de Sherbrooke  (Bruno.Nicolas.Cremella.Palmerini@USherbrooke.ca)

Sylvia Bonilla, Limnology Section, University of the Republic Montevideo, Uruguay  (sbon@fcien.edu.uy)

Beatrix Beisner, Department of Biological Sciences, University of Quebec at Montreal  (beisner.beatrix@uqam.ca)

Yannick Huot, Département de géomatique appliquée, Université de Sherbrooke  (Yannick.Huot@usherbrooke.ca)