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  • 1
    Publication Date: 2024-04-26
    Description: The sinking of particulate matter from the upper ocean dominates the export and sequestration of organic carbon by the biological pump, a critical component of the Earth's carbon cycle. Controls on carbon export are thought to be driven by ecological processes that produce and repackage sinking biogenic particles. Here, we present observations during the demise of the Northeast Atlantic Ocean spring bloom illustrating the importance of storm-induced turbulence on the dynamics of sinking particles. A sequence of four large storms caused upper layer mean turbulence levels to vary by more than three orders of magnitude. Large particle (>0.1 to 10 mm) abundance and size changed accordingly: increasing via shear coagulation when turbulence was moderate and decreasing rapidly when turbulence was intense due to shear disaggregation. Particle export was also tied to storm forcing as large particles were mixed to depth during mixed layer deepening. After the mixed layer shoaled, these particles, now isolated from intense surface mixing, grew larger and subsequently sank. This sequence of events matched the timing of sinking particle flux observations. Particle export was influenced by increases in aggregate abundance and porosity, which appeared to be enhanced by the repeated creation and destruction of aggregates. Last, particle transit efficiency through the mesopelagic zone was reduced by presumably biotic processes that created small particles (〈0.5 mm) from larger ones. Our results demonstrate that ocean turbulence significantly impacts the nature and dynamics of sinking particles, strongly influencing particle export and the efficiency of the biological pump.
    Type: Article , NonPeerReviewed
    Format: text
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  • 2
    Publication Date: 2022-05-26
    Description: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS One 9 (2014): e112379, doi:10.1575/1912/6845.
    Description: Increasing Transparent Exopolymer Particle (TEP) formation during diatom blooms as a result of elevated temperature and pCO2 have been suggested to result in enhanced aggregation and carbon flux, therewith potentially increasing the sequestration of carbon by the ocean. We present experimental results on TEP and aggregate formation by Thalassiosira weissflogii (diatom) in the presence or absence of bacteria under two temperature and three pCO2 scenarios. During the aggregation phase of the experiment TEP formation was elevated at the higher temperature (20°C vs. 15°C), as predicted. However, in contrast to expectations based on the established relationship between TEP and aggregation, aggregation rates and sinking velocity of aggregates were depressed in warmer treatments, especially under ocean acidification conditions. If our experimental findings can be extrapolated to natural conditions, they would imply a reduction in carbon flux and potentially reduced carbon sequestration after diatom blooms in the future ocean.
    Description: This work was supported by National Science Foundation grants OCE-0926711 & OCE-1041038 to UP and Helmholtz Graduate School for Polar and Marine Research and Jacobs University Bremen to SS.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 3
    Publication Date: 2022-05-26
    Description: NSF Biology of the Biological Pump Workshop, February 19–20, 2016 (Hyatt Place New Orleans, New Orleans, LA)
    Description: The net transfer of organic matter from the surface to the deep ocean is a key function of ocean food webs. The combination of biological, physical, and chemical processes that contribute to and control this export is collectively known as the “biological pump”, and current estimates of the global magnitude of this export range from 5 – 12 Pg C yr-1. This material can be exported in dissolved or particulate form, and many of the biological processes that regulate the composition, quantity, timing, and distribution of this export are poorly understood or constrained. Export of organic material is of fundamental importance to the biological and chemical functioning of the ocean, supporting deep ocean food webs and controlling the vertical and horizontal segregation of elements throughout the ocean. Remineralization of exported organic matter in the upper mesopelagic zone provides nutrients for surface production, while material exported to depths of 1000 m or more is generally considered to be sequestered — i.e. out of contact with the atmosphere for centuries or longer. The ability to accurately model a system is a reflection of the degree to which the system is understood. In the case of export, semi-empirical and simple mechanistic models show a wide range of predictive skill. This is, in part, due to the sparseness of available data, which impedes our inability to accurately represent, or even include, all relevant processes (sometimes for legitimate computational reasons). Predictions will remain uncertain without improved understanding and parameterization of key biological processes affecting export.
    Description: Funding for this workshop was provided by the National Science Foundation (NSF). Coordination and logistical support for this workshop was provided by the Ocean Carbon and Biogeochemistry (OCB) Program (www.us-ocb.org)
    Repository Name: Woods Hole Open Access Server
    Type: Book
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