Abstract
Diatoms are the primary source of nutrition and energy for the Southern Ocean ecosystem. Microalgae, including diatoms, synthesise biological macromolecules such as lipids, proteins and carbohydrates for growth, reproduction and acclimation to prevailing environmental conditions. Here we show that three key species of Southern Ocean diatom (Fragilariopsis cylindrus, Chaetoceros simplex and Pseudo-nitzschia subcurvata) exhibited phenotypic plasticity in response to salinity and temperature regimes experienced during the seasonal formation and decay of sea ice. The degree of phenotypic plasticity, in terms of changes in macromolecular composition, was highly species-specific and consistent with each species’ known distribution and abundance throughout sea ice, meltwater and pelagic habitats, suggesting that phenotypic plasticity may have been selected for by the extreme variability of the polar marine environment. We argue that changes in diatom macromolecular composition and shifts in species dominance in response to a changing climate have the potential to alter nutrient and energy fluxes throughout the Southern Ocean ecosystem.
Highlights
Macromolecules, including proteins, lipids and carbohydrates are the building blocks of life
This was indicative of a greater magnitude of change in macromolecular composition in F. cylindrus and C. simplex than P. subcurvata, as outlined below
This paper builds on Petrou et al by showing that phenotypic plasticity was manifest as changes in macromolecular composition
Summary
Macromolecules, including proteins, lipids and carbohydrates are the building blocks of life. In the Antarctic, greater than 50% of this production is contributed by diatoms, which dominate the microalgal assemblage, providing food for krill, fish, whales, penguins, and seabirds [1]. This capacity to synthesise macromolecules enables microalgae to acclimate to prevailing environmental conditions. Lipids are synthesised to sustain membrane structure and function and for energy storage, while proteins and carbohydrates have wide-ranging uses including maintenance of cell walls, membrane structure and function, mucus production, and osmoregulation [2,3,4] Such responses to environmental conditions have trophic implications because microalgal macromolecular composition affects herbivore assimilation efficiencies and reproductive success [5]
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