Temperature dependency of metabolic rates in the upper ocean: A positive feedback to global climate change?

Abstract

The temperature of seawater can affect marine plankton in various ways, including by affecting rates of metabolic processes. This can change the way carbon and nutrients are fixed and recycled and hence the chemical and biological profile of the water column. A variety of feedbacks on global climate are possible, especially by altering patterns of uptake and return of carbon dioxide to the atmosphere. Here we summarize and synthesize recent studies in the field of ecology, oceanography and ocean carbon cycling pertaining to possible feedbacks involving metabolic processes. By altering the rates of cellular growth and respiration, temperature-dependency may affect nutrient uptake and food demand in plankton and ultimately the equilibrium of pelagic food webs, with cascade effects on the flux of organic carbon between the upper and inner ocean (the "biological carbon pump") and the global carbon cycle. Insights from modern ecology can be applied to investigate how temperature-dependent changes in ocean biogeochemical cycling over thousands to millions of years may have shaped the long-term evolution of Earth's climate and life. Investigating temperature-dependency over geological time scales, including through globally warm and cold climate states, can help to identify processes that are relevant for a variety of future scenarios.

Functional Genomics Differentiate Inherent and Environmentally Influenced Traits in Dinoflagellate and Diatom Communities

“…Temperature effects on marine plankton are often described in the context of two fundamental concepts, namely, the metabolic theory of ecology [60,61] and the hypothesis of temperature-dependent physiology [62,63]. Although these two concepts are often studied separately, they are directly linked to each other by the influence of temperature on chemical reactions and metabolic rates, i.e., the sum of all enzyme-driven chemical reactions within cells [64].…”

“…Increases in temperature translate into increased rates of cellular and metabolic processes, most of which require ATP. The increased cellular demands result in an increased production of ATP, which is derived from respiration and photosynthesis [61,64,65]. Both processes are affected differently by temperature increases, with respiration possessing a relatively higher activation energy and hence respiration rates should increase more rapidly compared with photosynthesis [61,64,65].…”

Evolutionary temperature compensation of carbon fixation in marine phytoplankton

“…CR < GPP) to net heterotrophy (CR > GPP) (Cael & Follows ). Indeed, studies that have reconstructed rates of organic carbon remineralisation (John et al ) and deep ocean deposition (Olivarez Lyle & Lyle ) during previous climatic warming perturbations (particularly during the Eocene) suggest that ‘hyperthemal’ events reduced the potential for carbon sequestration in deep ocean sediments, because elevated temperatures resulted in increased rates of respiration and more efficient remineralisation of organic carbon at shallower depths (John et al ; Boscolo‐Galazzo et al ). These palaeoceanographic interpretations have been supported by Earth system model reconstructions (John et al ; Hülse et al ), thereby raising realistic concerns that contemporary ocean warming could also cause future reductions in deep ocean carbon burial via changes in microbial metabolism.…”

Linking Marine Plankton Ecosystems and Climate: A New Modeling Approach to the Warm Early Eocene Climate

“…An increase in mean cell size is also consistent with outputs from an ecosystem model that explored the response of plankton communities to anthropogenic climate change in the 21st century (Lefort et al, ). Heterotrophy is expected to be up to 2 times more sensitive to temperature changes than photosynthesis (Boscolo‐Galazzo et al, ), whereas these are treated uniformly in EcoGEnIE. As such, the effect of increased grazing pressure here is likely an underestimate.…”

“…This would have led to more rapid nutrient cycling in the upper ocean. Lastly, higher temperatures via increased metabolic rates could have additionally influenced ecological interactions such as increased growth rates and zooplankton grazing rates (e.g., Boscolo-Galazzo et al, 2018;Winder & Sommer, 2012).…”