Temperature controls carbon cycling and biological evolution in the ocean twilight zone

Abstract

Theory suggests that the ocean’s biological carbon pump, the process by which organic matter is produced at the surface and transferred to the deep ocean, is sensitive to temperature because temperature controls photosynthesis and respiration rates. We applied a combined data-modeling approach to investigate carbon and nutrient recycling rates across the world ocean over the past 15 million years of global cooling. We found that the efficiency of the biological carbon pump increased with ocean cooling as the result of a temperature-dependent reduction in the rate of remineralization (degradation) of sinking organic matter. Increased food delivery at depth prompted the development of new deep-water niches, triggering deep plankton evolution and the expansion of the mesopelagic “twilight zone” ecosystem.

Early Paleocene Paleoceanography and Export Productivity in the Chicxulub Crater

“…Another possibility that must be addressed is the effect of temperature on metabolic rates of grazers, with warmer waters facilitating increased remineralization of sinking organic matter, essentially making the biological pump less efficient (e.g., Boscolo-Galazzo et al, 2021;Griffith et al, 2021). Unfortunately, pervasive diagenetic alteration of carbonates means that it is not possible to make meaningful interpretations of temperature trends at Site M0077 using the bulk carbonate oxygen isotope record.…”

End-Permian marine extinction due to temperature-driven nutrient recycling and euxinia

“…If correct, this might be explained by ecologicallydriven changes in organic matter sinking rates or reactivity [25][26][27] that drive a vertical repartitioning of organic carbon respiration (and hence δ 13 C) in the ocean, although the nature and impact of such changes remain to be quantified. Here, by recognizing the universally important role of temperature in controlling microbial respiration 28 , we provide a simple mechanistic and data-constrained explanation for how expanded oxygen-minimum zones 26,27 and (episodic) shoaling of sulfidic waters 29 could have occurred and hence acted as an important kill mechanism during the mass extinction.…”

Adaptive Ecological Niche Migration does not Negate Extinction Susceptibility

“…One of the most pressing and fundamental issues for palaeoceanography, is whether fossil organisms identified via their external morphology used for the inference of paleoclimatic data maintain ecological uniformitarianism for the entirety of their stratigraphic range. Our study, alongside other novel research on modern and fossil populations 18,[55][56][57][58][59][60][61][62][63][64] suggests not, and as such deriving environmental interpretations from fossil taxa, particularly during intervals of climate variability, should be treated with caution. Whether the documentation of these behaviours indicate failed efforts at stress mitigation via water-depth associated parapatric anagenesis is currently undetermined, but further high-resolution comparable investigations through speciation events may help to understand the fundamental mechanisms driving evolution and extinction in an ecosystem with limited vicariance potential such as the open ocean.…”