Publication Date:
2022-10-27
Description:
© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tsakalakis, I., Follows, M. J., Dutkiewicz, S., Follett, C. L., & Vallino, J. J. Diel light cycles affect phytoplankton competition in the global ocean. Global Ecology and Biogeography, 31(9), (2022): 1838-1849, https://doi.org/10.1111/geb.13562.
Description:
Aim
Light, essential for photosynthesis, is present in two periodic cycles in nature: seasonal and diel. Although seasonality of light is typically resolved in ocean biogeochemical–ecosystem models because of its significance for seasonal succession and biogeography of phytoplankton, the diel light cycle is generally not resolved. The goal of this study is to demonstrate the impact of diel light cycles on phytoplankton competition and biogeography in the global ocean.
Location
Global ocean.
Major taxa studied
Phytoplankton.
Methods
We use a three-dimensional global ocean model and compare simulations of high temporal resolution with and without diel light cycles. The model simulates 15 phytoplankton types with different cell sizes, encompassing two broad ecological strategies: small cells with high nutrient affinity (gleaners) and larger cells with high maximal growth rate (opportunists). Both are grazed by zooplankton and limited by nitrogen, phosphorus and iron.
Results
Simulations show that diel cycles of light induce diel cycles in limiting nutrients in the global ocean. Diel nutrient cycles are associated with higher concentrations of limiting nutrients, by 100% at low latitudes (−40° to 40°), a process that increases the relative abundance of opportunists over gleaners. Size classes with the highest maximal growth rates from both gleaner and opportunist groups are favoured by diel light cycles. This mechanism weakens as latitude increases, because the effects of the seasonal cycle dominate over those of the diel cycle.
Main conclusions
Understanding the mechanisms that govern phytoplankton biogeography is crucial for predicting ocean ecosystem functioning and biogeochemical cycles. We show that the diel light cycle has a significant impact on phytoplankton competition and biogeography, indicating the need for understanding the role of diel processes in shaping macroecological patterns in the global ocean.
Description:
Simons Collaboration on Computational Biogeochemical Modeling of Marine Ecosystems supported M.J.F. and S.D. on CBIOMES grant #549931; C.L.F. on CBIOMES grants #827829 and #553242; and J.J.V. and I.T. on CBIOMES grant #549941. The National Science Foundation supported I.T. and J.J.V. on award #1558710 and J.J.V. on awards #1637630, #1655552 and #1841599.
Keywords:
Biogeography
;
Diel light cycle
;
Global ocean
;
Modelling
;
Nutrient cycles
;
Phytoplankton
;
Resource competition
Repository Name:
Woods Hole Open Access Server
Type:
Article
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