Contribution of hurricane-induced sediment resuspension to coastal oxygen dynamics

Abstract

Hurricanes passing over the ocean can mix the water column down to great depths and resuspend massive volumes of sediments on the continental shelves. Consequently, organic carbon and reduced inorganic compounds associated with these sediments can be resuspended from anaerobic portions of the seabed and re-exposed to dissolved oxygen (DO) in the water column. This process can drive DO consumption as sediments become oxidized. Previous studies have investigated the effect of hurricanes on DO in different coastal regions of the world, highlighting the alleviation of hypoxic conditions by extreme winds, which drive vertical mixing and re-aeration of the water column. However, the effect of hurricane-induced resuspended sediments on DO has been neglected. Here, using a diverse suite of datasets for the northern Gulf of Mexico, we find that in the few days after a hurricane passage, decomposition of resuspended shelf sediments consumes up to a fifth of the DO added to the bottom of the water column during vertical mixing. Despite uncertainty in this value, we highlight the potential significance of this mechanism for DO dynamics. Overall, sediment resuspension likely occurs over all continental shelves affected by tropical cyclones, potentially impacting global cycles of marine DO and carbon.

Seabed Resuspension in the Chesapeake Bay: Implications for Biogeochemical Cycling and Hypoxia

“…Observational studies from different locations (e.g., Lampitt et al 1995;Abril et al 1999;Queste et al 2016;Zeng et al 2017;Niemistö et al 2018;Porter et al 2018;Bianucci et al 2018), as well as recent modeling efforts for different environments (e.g., this study; Moriarty et al 2017Moriarty et al , 2018Lajaunie-Salla et al 2017), have indicated that the impact of resuspension on biogeochemical processes varies among systems. In Chesapeake Bay, for example, our results showed that vertically varying, bidirectional fluxes of POC due to estuarine circulation impacted the effect of resuspension on Bay biogeochemistry (see "Along-Estuary Variability in the Response of Primary Productivity and Remineralization to Resuspension" and "Implications for Oxygen and Nitrogen Dynamics" sections).…”

“…Resuspension entrains inorganic particulates and particulate organic matter (POM) into the water column, increasing turbidity and light attenuation (e.g., Cloern 1987;Xu et al 2005;Gallegos et al 2011;Shi et al 2013). Transference of material from the seabed to the water column may also enhance remineralization rates due to the increased POM concentrations in bottom waters, as well as the exposure of that organic matter to an oxic water column (Stahlberg et al 2006;Aller 1998;Hartnett et al 1998;Burdige 2007;Queste et al 2016;Bianucci et al 2018). Resuspension may also influence fluxes of dissolved oxygen and nutrients through the seabed-water interface (e.g., Glud 2008;Toussaint et al 2014).…”

The Role of Sediment-induced Light Attenuation on Primary Production during Hurricane Gustav (2008)

“…Meanwhile, the post-hurricane stratification recovery in summer and fall seasons prevented oxygen ventilation to the bottom. Another major process that might further lower the oxygen level was the high respiration rate caused by resuspended POM (Bianucci et al, 2018). McCarthy et al (2013) reported a post-Gustav respiration peak associated with organic matter resuspension in the bottom boundary layer.…”

Hurricanes Enhance Labile Carbon Export to the Deep Ocean

“…The global impact of hurricane activity on the ocean carbon cycle remains to be evaluated. Although there are uncertainties in historical trends of hurricane intensity (Klotzbach et al, 2015;Sobel et al, 2016;Walsh et al, 2016;Yan et al, 2017), recent modeling studies suggest that hurricane intensity will increase as climate warms (Bhatia et al, 2019;Bianucci et al, 2018;Kossin, 2017). Further studies, in particular at long time series sites, are needed to elucidate the various effects of hurricanes on the oligotrophic ocean's biological pump.…”