Abstract
Abstract. Interactions between seawater and benthic systems play an important role in global biogeochemical cycling. Benthic fluxes of some chemical elements (e.g., C, N, P, O, Si, Fe, Mn, S) alter the redox state and marine carbonate system (i.e., pH and carbonate saturation state), which in turn modulate the functioning of benthic and pelagic ecosystems. The redox state of the near-bottom layer in many regions can change with time, responding to the supply of organic matter, physical regime, and coastal discharge. We developed a model (BROM) to represent key biogeochemical processes in the water and sediments and to simulate changes occurring in the bottom boundary layer. BROM consists of a transport module (BROM-transport) and several biogeochemical modules that are fully compatible with the Framework for the Aquatic Biogeochemical Models, allowing independent coupling to hydrophysical models in 1-D, 2-D, or 3-D. We demonstrate that BROM is capable of simulating the seasonality in production and mineralization of organic matter as well as the mixing that leads to variations in redox conditions. BROM can be used for analyzing and interpreting data on sediment–water exchange, and for simulating the consequences of forcings such as climate change, external nutrient loading, ocean acidification, carbon storage leakage, and point-source metal pollution.
Highlights
Oxygen depletion and anoxia are increasingly common phenomena observed in the World Ocean, inland seas, and coastal areas
We demonstrate that BROM is capable of simulating the seasonality in production and mineralization of organic matter as well as the mixing that leads to variations in redox conditions
The model simulated the periodic replacement of oxic with anoxic conditions in the benthic boundary layer (BBL) following seasonal mixing and OM production
Summary
Oxygen depletion and anoxia are increasingly common phenomena observed in the World Ocean, inland seas, and coastal areas. Oxic conditions during periods of intense mixing are followed by near-bottom suboxia or anoxia after the seasonal pycnocline forms, restricting aeration of the deeper layers. This occurs, for instance, on the Louisiana shelf (Morse and Eldridge, 2007; Yu et al, 2015) and in Corpus Christi Bay (McCarthy et al, 2008), the Sea of Azov (Debolskaya et al, 2008), and Eleusis Bay (Pavlidou et al, 2013)
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