Abstract
The distribution of marine phytoplankton will shift alongside changes in marine environments, leading to altered species frequencies and community composition. An understanding of the response of mixed populations to abiotic changes is required to adequately predict how environmental change may affect the future composition of phytoplankton communities. This study investigated the growth and competitive ability of two marine diatoms, Phaeodactylum tricornutum and Thalassiosira pseudonana, along a temperature gradient (9–35°C) spanning the thermal niches of both species under both high‐nitrogen nutrient‐replete and low‐nitrogen nutrient‐limited conditions. Across this temperature gradient, the competitive outcome under both nutrient conditions at any assay temperature, and the critical temperature at which competitive advantage shifted from one species to the other, was well predicted by the temperature dependencies of the growth rates of the two species measured in monocultures. The temperature at which the competitive advantage switched from P. tricornutum to T. pseudonana increased from 18.8°C under replete conditions to 25.3°C under nutrient‐limited conditions. Thus, P. tricornutum was a better competitor over a wider temperature range in a low N environment. Being able to determine the competitive outcomes from physiological responses of single species to environmental changes has the potential to significantly improve the predictive power of phytoplankton spatial distribution and community composition models.
Highlights
Competition plays an important role in shaping biological communities in terrestrial and aquatic ecosystems (Tilman, 1987)
Being able to determine the competitive outcomes from physiological responses of single species to environmental changes has the potential to significantly improve the predictive power of phytoplankton spatial distribution and community composition models
To display the strength of how closely our local estimated scatter plot smoothing (LOESS) smoother followed the calculated competition coefficients, we reported R2values and residual standard errors (RSE) in the results
Summary
Competition plays an important role in shaping biological communities in terrestrial and aquatic ecosystems (Tilman, 1987). . |2 the minimum requirement of a species to support its temperature and light-dependent maximum growth rate (μmax) and, become limiting (Andersen, 2005). The minimum resource concentration that supports net population growth, and for which uptake rates by the population and supply rates by the environment are in balance, is called R* (Tilman, 1981). Apart from limiting nutrients, species diversity is governed by other major regulating forces which can be biotic (e.g., differential grazing pressure or various forms of symbiosis such as mutualism or parasitism) or abiotic (e.g., temperature, pH, salinity) (Begon, Townsend, & Harper, 2006; Cloern & Dufford, 2005)
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