Organic matter remineralization in marine sediments: A Pan‐Arctic synthesis

Abstract

Climate change in the Arctic is ongoing and causes drastic modification on the ecosystem functioning. In soft-bottom environments, organic matter remineralization is considered an important ecosystem function. Here we provide a large-scale assessment of the current knowledge on the benthic organic matter remineralization and its potential response to climate change. Sediment oxygen demand (SOD) values (n = 1154), measured throughout the Arctic, were gathered from 30 publications and 16 databases, and nutrient flux values, available in a far lesser extent (n < 80), were also compiled. Generalized additive models were used to estimate the influence of explanatory variables on benthic oxygen fluxes and for interpolating SOD to the whole Arctic region. This first Pan-Arctic review of the distributions of SOD showed that oxygen fluxes strongly depended on water depth, i.e., followed the general trend observed for other regions, and also on the availability of labile organic matter. The continental shelves (representing~50% of Arctic Ocean's total area) were characterized by the highest SOD values (10.5 ± 7.9 mmol O 2 m À2 d À1 ), and differences among shelves were observed; SOD values in inflow, interior, and outflow shelves were 11.8 ± 8.0, 6.2 ± 5.6, and 3.9 ± 3.5 mmol O 2 m À2 d À1 , respectively. Moreover, seasonal variation in SOD changed significantly among areas. The interpolation based on the best fitted model showed high respiration in the inflow and interior shelves. In the inflow shelves, characterized by productive waters, benthic activities replenish bottom water with nutrients which may augment primary productivity, whereas sediments from the interior shelves, e.g., under the direct influence of the Mackenzie River, consume nutrients.

Deep-sea benthic communities and oxygen fluxes in the Arctic Fram Strait controlled by sea-ice cover and water depth

“…Our oxygen fluxes within the HSC and LSC categories are comparable to earlier findings within the Fram Strait by Sauter et al (2001) and Cathalot et al (2015) and also by findings of Boetius and Damm (1998) for the continental margin of the Laptev Sea, but slightly lower than the modelled results by Bourgeois et al (2017, Fig. 6).…”

“…Furthermore, the measurements of the benthic oxygen flux, crucial to evaluate the pelagic-benthic-coupling, remain only snapshots of remineralisation. The question, if the Arctic deep-sea benthic oxygen fluxes follow seasonal changes, has only been sparsely evaluated (Bourgeois et al, 2017). A full annual cycle of benthic remineralisation is still missing and as such, a more reliable discussion of the pelagic-benthiccoupling and the carbon cycle remains difficult.…”

“…As a consequence, the climate change induced alteration in the sea-ice cover influence biogeochemical cycles in the western Arctic (Harada, 2016). Further, arctic benthic oxygen flux model by Bourgeois et al (2017) showed a better fit when benthic chlorophyll data, indicating surface primary production patterns, were taken into account. Boetius and Damm (1998) also found a good correlation between sea-ice cover, benthic chlorophyll and benthic carbon remineralisation in the Laptev Sea.…”

“…The occurrence of sea ice is an additional factor influencing primary production across the Arctic Ocean, as it ultimately alters the light availability (Arrigo et al, 2008;Bourgeois et al, 2017). As a consequence, the climate change induced alteration in the sea-ice cover influence biogeochemical cycles in the western Arctic (Harada, 2016).…”

Scientific Considerations for the Assessment and Management of Mine Tailings Disposal in the Deep Sea

“…Submerged tailings constitute both a potential source of remobilized dissolved metals and metalloids, as well as processing chemicals (e.g., acids, flocculants and floatation agents) to pore water and overlying water (Perner et al, 2010;Shimmield et al, 2010;Angel et al, 2013;Simpson and Spadaro, 2016) by bacterially-mediated, sediment diagenetic processes associated with the remineralization of organic matter (Middelburg and Levin, 2009;Bourgeois et al, 2017). For instance, increased copper concentrations can affect microbial biomass and metabolic activity leading to reduction of their assimilative capacity, and hence impaired crucial ecosystem services such as carbon and nutrient cycling (Jonas, 1989;Almeida et al, 2007).…”