scholarly journals Impact of bottom trawling on sediment biogeochemistry: a modelling approach

2020 ◽  
Author(s):  
Emil De Borger ◽  
Justin Tiano ◽  
Ulrike Braeckman ◽  
Adriaan D. Rijnsdorp ◽  
Karline Soetaert
Keyword(s):  
Organic Carbon ◽  
Electric Pulse ◽  
Carbon Mineralization ◽  
Sandy Sediment ◽  
Bottom Trawling ◽  
Benthic Metabolism ◽  
Sedimentary Environments ◽  
Sediment Biogeochemistry ◽  
Sediment Types ◽  
Modelling Approach

Abstract. Bottom trawling in shelf seas can occur more than 10 times per year for a given location. This affects the benthic metabolism, through a mortality of the macrofauna, resuspension of organic matter from the sediment, and alterations of the physical sediment structure. However, the trawling impacts on organic carbon mineralization and associated processes are not well known. Using a modelling approach, the effects of increasing trawling frequencies on early diagenesis were studied in five different sedimentary environments, simulating the effects of a deep penetrating gear (e.g. a tickler chain beam trawl) and a shallower, more variable penetrating gear (e.g. an electric pulse trawl). Trawling events strongly increased oxygen and nitrate concentrations in surface sediment layers, and led to significantly lower amounts of ammonium (43–99 % reduction) and organic carbon in the top 10 cm of the sediment (62–96 % reduction). As a result, total mineralization rates in the sediment were decreased by up to 28 %. The effect on different mineralization processes differed both between sediment types, and between trawling frequencies. The shallow penetrating gear had a slightly smaller effect on benthic denitrification than the deep penetrating gear, but there were no statistically different results between gear types for all other parameters. Denitrification was reduced by 69 % in a fine sandy sediment, whereas nitrogen removal nearly doubled in a highly eutrophic mud. This suggests that even relatively low penetration depths from bottom fishing gears generates significant biogeochemical alterations. Physical organic carbon removal through trawl-induced resuspension of sediments, exacerbated by a removal of bioturbating macrofauna, was identified as the main cause of the changes in the mineralization process.

scholarly journals Impact of bottom trawling on sediment biogeochemistry: a modelling approach

2021 ◽  
Vol 18 (8) ◽  
pp. 2539-2557
Author(s):  
Emil De Borger ◽  
Justin Tiano ◽  
Ulrike Braeckman ◽  
Adriaan D. Rijnsdorp ◽  
Karline Soetaert
Keyword(s):  
Organic Carbon ◽  
Electric Pulse ◽  
Carbon Mineralization ◽  
Sandy Sediment ◽  
Bottom Trawling ◽  
Benthic Metabolism ◽  
Sedimentary Environments ◽  
Sediment Biogeochemistry ◽  
Sediment Types ◽  
Modelling Approach

Abstract. Bottom trawling in shelf seas can occur more than 10 times per year for a given location. This affects the benthic metabolism, through a mortality of the macrofauna, resuspension of organic matter from the sediment, and alterations of the physical sediment structure. However, the trawling impacts on organic carbon mineralization and associated processes are not well known. Using a modelling approach, the effects of increasing trawling frequencies on early diagenesis were studied in five different sedimentary environments, simulating the effects of a deeper-penetrating gear (e.g. a tickler chain beam trawl) versus a shallower, more variable penetrating gear (e.g. an electric pulse trawl). Trawling events strongly increased oxygen and nitrate concentrations in surface sediment layers and led to significantly lower amounts of ammonium (43 %–99 % reduction) and organic carbon in the top 10 cm of the sediment (62 %–96 % reduction). As a result, total mineralization rates in the sediment were decreased by up to 28 %. The effect on different mineralization processes differed both between sediment types and between trawling frequencies. The shallow-penetrating gear had a slightly smaller effect on benthic denitrification than the deeper-penetrating gear, but there were no statistically different results between gear types for all other parameters. Denitrification was reduced by 69 % in a fine sandy sediment, whereas nitrogen removal nearly doubled in a highly eutrophic mud. This suggests that even relatively low penetration depths from bottom fishing gears generate significant biogeochemical alterations. Physical organic carbon removal through trawl-induced resuspension of sediments, exacerbated by a removal of bioturbating macrofauna, was identified as the main cause of the changes in the mineralization process.

scholarly journals Supplementary material to "Impact of bottom trawling on sediment biogeochemistry: a modelling approach"

2020 ◽  
Author(s):  
Emil De Borger ◽  
Justin Tiano ◽  
Ulrike Braeckman ◽  
Adriaan D. Rijnsdorp ◽  
Karline Soetaert
Keyword(s):  
Bottom Trawling ◽  
Sediment Biogeochemistry ◽  
Supplementary Material ◽  
Modelling Approach

scholarly journals A new look at the multi-G model for organic carbon degradation in surface marine sediments for coupled benthic–pelagic simulations of the global ocean

2018 ◽  
Vol 15 (11) ◽  
pp. 3391-3407 ◽  
Author(s):  
Konstantin Stolpovsky ◽  
Andrew W. Dale ◽  
Klaus Wallmann
Keyword(s):  
Steady State ◽  
Organic Carbon ◽  
Degradation Kinetics ◽  
Carbon Mineralization ◽  
Global Scale ◽  
Global Ocean ◽  
Global Database ◽  
Sedimentary Environments ◽  
Carbon Burial ◽  
Organic Carbon Burial

Abstract. The kinetics of particulate organic carbon (POC) mineralization in marine surface sediments is not well constrained. This creates considerable uncertainties when benthic processes are considered in global biogeochemical or Earth system circulation models to simulate climate–ocean interactions and biogeochemical tracer distributions in the ocean. In an attempt to improve our understanding of the rate and depth distribution of organic carbon mineralization in bioturbated (0–20 cm) sediments at the global scale, we parameterized a 1-D diagenetic model that simulates the mineralization of three discrete POC pools (a multi-G model). The rate constants of the three reactive classes (highly reactive, reactive, refractory) are fixed and determined to be 70, 0.5 and ∼ 0.001 yr−1, respectively, based on the Martin curve model for pelagic POC degradation. In contrast to previous approaches, however, the reactivity of the organic material degraded in the seafloor is continuous with, and set by, the apparent reactivity of material sinking through the water column. Despite the simplifications of describing POC remineralization using G-type approaches, the model is able to simulate a global database (185 stations) of benthic oxygen and nitrate fluxes across the sediment–water interface in addition to porewater oxygen and nitrate distributions and organic carbon burial efficiencies. It is further consistent with degradation experiments using fresh phytoplankton reported in a previous study. We propose that an important yet mostly overlooked consideration in upscaling approaches is the proportion of the reactive POC classes reaching the seafloor in addition to their reactivity. The approach presented is applicable to both steady-state and non-steady state scenarios, and links POC degradation kinetics in sedimentary environments to water depth and the POC rain rate to the seafloor.

scholarly journals A new look at the multi-G model for organic carbon degradation in surface marine sediments for coupled benthic-pelagic simulations of the global ocean

2017 ◽  
Author(s):  
Konstantin Stolpovsky ◽  
Andrew W. Dale ◽  
Klaus Wallmann
Keyword(s):  
Steady State ◽  
Organic Carbon ◽  
Degradation Kinetics ◽  
Carbon Mineralization ◽  
Global Scale ◽  
Global Ocean ◽  
Global Database ◽  
Sedimentary Environments ◽  
Carbon Burial ◽  
Organic Carbon Burial

Abstract. The kinetics of particulate organic carbon (POC) mineralization in marine surface sediments is not well constrained. This creates considerable uncertainties when benthic processes are considered in global biogeochemical or Earth system circulation models to simulate climate-ocean interactions and biogeochemical tracers in the ocean. In an attempt to improve our understanding of the rate and depth distribution of organic carbon mineralization in bioturbated (0–10 cm) sediments, we parameterized a 1-D diagenetic model that simulates the reactivity of three discrete POC pools at global scale (a multi-G model). The rate constants of the three reactive classes (highly reactive, reactive, refractory) are fixed and determined to be 70 yr−1, 0.5 yr−1, and ~0.001 yr−1, respectively, based on the Martin curve model for pelagic POC degradation. In contrast to previous approaches, the reactivity of the organic material degraded in the seafloor is continuous with, and set by, the apparent reactivity of material sinking through the water column. The model is able to simulate a global database (185 stations) of benthic oxygen and nitrate fluxes across the sediment-water interface in addition to porewater oxygen and nitrate distributions and organic carbon burial efficiencies. It is further consistent with degradation experiments of fresh phytoplankton. We propose that an important yet mostly overlooked consideration in previous upscaling approaches is the proportion of the relative reactive POC classes reaching the seafloor in addition to their reactivity. The approach presented is applicable to both steady-state and non-steady state scenarios, and links POC degradation kinetics in sedimentary environments to water depth and the POC rain rate to the seafloor.

scholarly journals Long-Term Nitrogen Addition Decreases Soil Carbon Mineralization in an N-Rich Primary Tropical Forest

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 734
Author(s):  
Xiankai Lu ◽  
Qinggong Mao ◽  
Zhuohang Wang ◽  
Taiki Mori ◽  
Jiangming Mo ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Tropical Forest ◽  
Soil Carbon ◽  
Tropical Forests ◽  
Carbon Mineralization ◽  
N Deposition ◽  
Soil Carbon Mineralization ◽  
N Additions

Anthropogenic elevated nitrogen (N) deposition has an accelerated terrestrial N cycle, shaping soil carbon dynamics and storage through altering soil organic carbon mineralization processes. However, it remains unclear how long-term high N deposition affects soil carbon mineralization in tropical forests. To address this question, we established a long-term N deposition experiment in an N-rich lowland tropical forest of Southern China with N additions such as NH4NO3 of 0 (Control), 50 (Low-N), 100 (Medium-N) and 150 (High-N) kg N ha−1 yr−1, and laboratory incubation experiment, used to explore the response of soil carbon mineralization to the N additions therein. The results showed that 15 years of N additions significantly decreased soil carbon mineralization rates. During the incubation period from the 14th day to 56th day, the average decreases in soil CO2 emission rates were 18%, 33% and 47% in the low-N, medium-N and high-N treatments, respectively, compared with the Control. These negative effects were primarily aroused by the reduced soil microbial biomass and modified microbial functions (e.g., a decrease in bacteria relative abundance), which could be attributed to N-addition-induced soil acidification and potential phosphorus limitation in this forest. We further found that N additions greatly increased soil-dissolved organic carbon (DOC), and there were significantly negative relationships between microbial biomass and soil DOC, indicating that microbial consumption on soil-soluble carbon pool may decrease. These results suggests that long-term N deposition can increase soil carbon stability and benefit carbon sequestration through decreased carbon mineralization in N-rich tropical forests. This study can help us understand how microbes control soil carbon cycling and carbon sink in the tropics under both elevated N deposition and carbon dioxide in the future.

The vulnerability of Arctic shelf sediments to climate change

2015 ◽  
Vol 23 (4) ◽  
pp. 461-479 ◽  
Author(s):  
Robie W. Macdonald ◽  
Zou Zou A. Kuzyk ◽  
Sophia C. Johannessen
Keyword(s):  
Organic Carbon ◽  
Carbon Sources ◽  
The Arctic ◽  
Sedimentary Environments ◽  
Carbon Supply ◽  
Shelf Sediment ◽  
Wide Range ◽  
Metabolic Conditions ◽  
Shelf Sediments ◽  
Ocean Ecosystem

The sediments of the pan-Arctic shelves contribute an important component to the Arctic Ocean ecosystem by providing a habitat for biota (benthos), a repository for organic and inorganic non-conservative substances entering or produced within the ocean, a reactor and source of transformed substances back to the water column, and a mechanism of burial. Sediments interact with ice, ocean, and the surrounding land over a wide range of space and time scales. We discuss the vulnerability of shelf sediment to changes in (i) organic carbon sources, (ii) pathways of sediment and organic carbon supply, and (iii) physical and biogeochemical alteration (diagenesis). Sedimentary environments of the shelves and basins are likely to exhibit a wide variance in their response to global change because of their wide variation in sediment sources, processes, and metabolic conditions. In particular, the Chukchi and Barents shelves are dominated by inflowing waters from oceans to the south, whereas the interior shelves are more closely tied to terrigenous sources due to river inflow and coastal erosion.

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