What global biogeochemical consequences will marine animal–sediment interactions have during climate change?

Abstract

Benthic animals profoundly influence the cycling and storage of carbon and other elements in marine systems, particularly in coastal sediments. Recent climate change has altered the distribution and abundance of many seafloor taxa and modified the vertical exchange of materials between ocean and sediment layers. Here, we examine how climate change could alter animal-mediated biogeochemical cycling in ocean sediments. The fossil record shows repeated major responses from the benthos during mass extinctions and global carbon perturbations, including reduced diversity, dominance of simple trace fossils, decreased burrow size and bioturbation intensity, and nonrandom extinction of trophic groups. The broad dispersal capacity of many extant benthic species facilitates poleward shifts corresponding to their environmental niche as overlying water warms. Evidence suggests that locally persistent populations will likely respond to environmental shifts through either failure to respond or genetic adaptation rather than via phenotypic plasticity. Regional and global ocean models insufficiently integrate changes in benthic biological activity and their feedbacks on sedimentary biogeochemical processes. The emergence of bioturbation, ventilation, and seafloor-habitat maps and progress in our mechanistic understanding of organism–sediment interactions enable incorporation of potential effects of climate change on benthic macrofaunal mediation of elemental cycles into regional and global ocean biogeochemical models.

Carbon Fluxes in the Coastal Ocean: Synthesis, Boundary Processes, and Future Trends

“…Global ocean biogeochemical models (GOBMs) (Dunne et al 2020, Tjiputra et al 2020, such as those used in the United Nations Intergovernmental Panel on Climate Change (Ciais et al 2013) or the Global Carbon Project (Friedlingstein et al 2020), have resolutions that are typically too coarse to provide a reliable basis for the analysis of coastal ocean carbon fluxes (Holt et al 2009, Mathis et al 2017). An equally important limitation is that these models do not include or only provide simplistic representations of processes relevant to the coastal ocean interface, such as time-varying riverine fluxes (Lacroix et al 2020), their modulation by the estuary-coastal vegetation continuum (Bauer et al 2013), and benthic carbon processing (Bianchi et al 2021, Krumins et al 2013. However, improved model resolution, afforded by advances in computational capabilities, allows GOBMs to represent important features of the coastal ocean, such as three-dimensional material and substance transports, residence times (Lacroix et al 2021a, Liu & Gan 2017, air-sea CO 2 exchange (Bourgeois et al 2016), and riverine fluxes (Dunne et al 2020;Lacroix et al 2020Lacroix et al , 2021a representation of specific coastal processes (e.g., heterotrophic respiration and burial of organic carbon, benthic calcification) greatly lags behind improvements in model resolution.…”

A global assessment of the mixed layer in coastal sediments and implications for carbon storage

“…This characterization can lead to more insights about hotspots of organic matter cycling in marine sediments 56 , which can more broadly support Earth System Models. Finally, as many marine macrofaunal benthos in the coastal ocean are undergoing poleward range expansion due to global warming 70 , SMLs will likely undergo additional change that will also need to be included in ongoing modeling efforts.…”

Benthic Invertebrates on the Move: A Tale of Ocean Warming and Sediment Carbon Storage

“…However, few people recognize the potential feedback between these changes and climate change itself, through alteration of carbon cycling in the marine environment. Recent syntheses have argued that climate‐related changes in the assemblage of seafloor communities, for example, could alter the biological and physical properties of marine ecosystems, which, in turn, will impact carbon sources and sinks in ocean sediments (Bianchi et al 2021). These ocean sediments represent Earth's largest interactive landscape for organic carbon (OC) storage, serving as a vital CO 2 sink.…”