scholarly journals An Integrative Model of Carbon and Nitrogen Metabolism in a Common Deep-Sea Sponge (Geodia barretti)

2021 ◽  
Vol 7 ◽  
Author(s):  
Anna de Kluijver ◽  
Martijn C. Bart ◽  
Dick van Oevelen ◽  
Jasper M. de Goeij ◽  
Sally P. Leys ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Deep Sea ◽  
Functional Integration ◽  
C:N Ratio ◽  
Integrative Model ◽  
Consistent Manner ◽  
Doc Production ◽  
Microbial Symbionts ◽  
Forms Of Carbon

Deep-sea sponges and their microbial symbionts transform various forms of carbon (C) and nitrogen (N) via several metabolic pathways, which, for a large part, are poorly quantified. Previous flux studies on the common deep-sea sponge Geodia barretti consistently revealed net consumption of dissolved organic carbon (DOC) and oxygen (O2) and net release of nitrate (NO3-). Here we present a biogeochemical metabolic network model that, for the first time, quantifies C and N fluxes within the sponge holobiont in a consistent manner, including many poorly constrained metabolic conversions. Using two datasets covering a range of individual G. barretti sizes (10–3,500 ml), we found that the variability in metabolic rates partially resulted from body size as O2 uptake allometrically scales with sponge volume. Our model analysis confirmed that dissolved organic matter (DOM), with an estimated C:N ratio of 7.7 ± 1.4, is the main energy source of G. barretti. DOM is primarily used for aerobic respiration, then for dissimilatory NO3- reduction to ammonium (NH4+) (DNRA), and, lastly, for denitrification. Dissolved organic carbon (DOC) production efficiencies (production/assimilation) were estimated as 24 ± 8% (larger individuals) and 31 ± 9% (smaller individuals), so most DOC was respired to carbon dioxide (CO2), which was released in a net ratio of 0.77–0.81 to O2 consumption. Internally produced NH4+ from cellular excretion and DNRA fueled nitrification. Nitrification-associated chemoautotrophic production contributed 5.1–6.7 ± 3.0% to total sponge production. While overall metabolic patterns were rather independent of sponge size, (volume-)specific rates were lower in larger sponges compared to smaller individuals. Specific biomass production rates were 0.16% day–1 in smaller compared to 0.067% day–1 in larger G. barretti as expected for slow-growing deep-sea organisms. Collectively, our approach shows that metabolic modeling of hard-to-reach, deep-water sponges can be used to predict community-based biogeochemical fluxes and sponge production that will facilitate further investigations on the functional integration and the ecological significance of sponge aggregations in deep-sea ecosystems.

In situ dissolved organic carbon (DOC) release by submerged macrophyte–epiphyte communities in southern Quebec lakes

2009 ◽  
Vol 66 (9) ◽  
pp. 1522-1531 ◽  
Author(s):  
M. Demarty ◽  
Y. T. Prairie
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Myriophyllum Spicatum ◽  
Dry Weight ◽  
Release Rates ◽  
Doc Production ◽  
Epiphyte Communities ◽  
Benthic Chambers ◽  
Freshwater Macrophyte

We studied the in situ release of dissolved organic carbon (DOC) by growing a submerged freshwater macrophyte–epiphyte complex. Incubations with benthic chambers in five southeastern Quebec lakes show a net DOC production for different communities of Myriophyllum spicatum and Potamogeton spp. Daytime DOC release rates range from undetectable to 9.7 mg C·m–2·h–1. Although DOC release was restricted to daylight hours and thus suggestive of a photosynthesis-related process, we found no strong link between DOC release rates and concurrent illumination or temperature. We found no difference in DOC release rates between the three main colonizing species of the studied region. The overall mean DOC release rate was 4.57 mg C·m–2·h–1 (standard deviation (SD), ±0.65) or 56 µg C·g dry weight–1·h–1 (SD, ±8), which we suggest can be used for extrapolations at the lake scale.

scholarly journals Temperature controls production but hydrology regulates export of dissolved organic carbon at the catchment scale

2020 ◽  
Vol 24 (2) ◽  
pp. 945-966 ◽  
Author(s):  
Hang Wen ◽  
Julia Perdrial ◽  
Benjamin W. Abbott ◽  
Susana Bernal ◽  
Rémi Dupas ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Groundwater Flow ◽  
Soil Water ◽  
Reactive Transport ◽  
Stream Water ◽  
Catchment Scale ◽  
High Discharge ◽  
Doc Production ◽  
Doc Concentration

Abstract. Lateral carbon flux through river networks is an important and poorly understood component of the global carbon budget. This work investigates how temperature and hydrology control the production and export of dissolved organic carbon (DOC) in the Susquehanna Shale Hills Critical Zone Observatory in Pennsylvania, USA. Using field measurements of daily stream discharge, evapotranspiration, and stream DOC concentration, we calibrated the catchment-scale biogeochemical reactive transport model BioRT-Flux-PIHM (Biogeochemical Reactive Transport–Flux–Penn State Integrated Hydrologic Model, BFP), which met the satisfactory standard of a Nash–Sutcliffe efficiency (NSE) value greater than 0.5. We used the calibrated model to estimate and compare the daily DOC production rates (Rp; the sum of the local DOC production rates in individual grid cells) and export rate (Re; the product of the concentration and discharge at the stream outlet, or load). Results showed that daily Rp varied by less than an order of magnitude, primarily depending on seasonal temperature. In contrast, daily Re varied by more than 3 orders of magnitude and was strongly associated with variation in discharge and hydrological connectivity. In summer, high temperature and evapotranspiration dried and disconnected hillslopes from the stream, driving Rp to its maximum but Re to its minimum. During this period, the stream only exported DOC from the organic-poor groundwater and from organic-rich soil water in the swales bordering the stream. The DOC produced accumulated in hillslopes and was later flushed out during the wet and cold period (winter and spring) when Re peaked as the stream reconnected with uphill and Rp reached its minimum. The model reproduced the observed concentration–discharge (C–Q) relationship characterized by an unusual flushing–dilution pattern with maximum concentrations at intermediate discharge, indicating three end-members of source waters. A sensitivity analysis indicated that this nonlinearity was caused by shifts in the relative contribution of different source waters to the stream under different flow conditions. At low discharge, stream water reflected the chemistry of organic-poor groundwater; at intermediate discharge, stream water was dominated by the organic-rich soil water from swales; at high discharge, the stream reflected uphill soil water with an intermediate DOC concentration. This pattern persisted regardless of the DOC production rate as long as the contribution of deeper groundwater flow remained low (<18 % of the streamflow). When groundwater flow increased above 18 %, comparable amounts of groundwater and swale soil water mixed in the stream and masked the high DOC concentration from swales. In that case, the C–Q patterns switched to a flushing-only pattern with increasing DOC concentration at high discharge. These results depict a conceptual model that the catchment serves as a producer and storage reservoir for DOC under hot and dry conditions and transitions into a DOC exporter under wet and cold conditions. This study also illustrates how different controls on DOC production and export – temperature and hydrological flow paths, respectively – can create temporal asynchrony at the catchment scale. Future warming and increasing hydrological extremes could accentuate this asynchrony, with DOC production occurring primarily during dry periods and lateral export of DOC dominating in major storm events.

scholarly journals The effect of drought on dissolved organic carbon (DOC) release from peatland soil and vegetation sources

2017 ◽  
Vol 14 (11) ◽  
pp. 2891-2902 ◽  
Author(s):  
Jonathan P. Ritson ◽  
Richard E. Brazier ◽  
Nigel J. D. Graham ◽  
Chris Freeman ◽  
Michael R. Templeton ◽  
...  
Keyword(s):  
Water Treatment ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Unit Weight ◽  
Catchment Management ◽  
Litter Layer ◽  
Peat Soils ◽  
Drought Tolerant ◽  
Doc Production ◽  
The Impact

Abstract. Drought conditions are expected to increase in frequency and severity as the climate changes, representing a threat to carbon sequestered in peat soils. Downstream water treatment works are also at risk of regulatory compliance failures and higher treatment costs due to the increase in riverine dissolved organic carbon (DOC) often observed after droughts. More frequent droughts may also shift dominant vegetation in peatlands from Sphagnum moss to more drought-tolerant species. This paper examines the impact of drought on the production and treatability of DOC from four vegetation litters (Calluna vulgaris, Juncus effusus, Molinia caerulea and Sphagnum spp.) and a peat soil. We found that mild droughts caused a 39.6 % increase in DOC production from peat and that peat DOC that had been exposed to oxygen was harder to remove by conventional water treatment processes (coagulation/flocculation). Drought had no effect on the amount of DOC production from vegetation litters; however large variation was observed between typical peatland species (Sphagnum and Calluna) and drought-tolerant grassland species (Juncus and Molinia), with the latter producing more DOC per unit weight. This would therefore suggest the increase in riverine DOC often observed post-drought is due entirely to soil microbial processes and DOC solubility rather than litter layer effects. Long-term shifts in species diversity may, therefore, be the most important impact of drought on litter layer DOC flux, whereas pulses related to drought may be observed in peat soils and are likely to become more common in the future. These results provide evidence in support of catchment management which increases the resilience of peat soils to drought, such as ditch blocking to raise water tables.

Climatic factors influencing fluxes of dissolved organic carbon from the forest floor in a continuous-permafrost Siberian watershed

2005 ◽  
Vol 35 (9) ◽  
pp. 2130-2140 ◽  
Author(s):  
A S Prokushkin ◽  
T Kajimoto ◽  
S G Prokushkin ◽  
W H McDowell ◽  
A P Abaimov ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Forest Floor ◽  
Climatic Factors ◽  
Soil Layer ◽  
The South ◽  
The North ◽  
Doc Production ◽  
Doc Flux ◽  
Forest Floor Leachates

Fluxes of dissolved organic carbon (DOC) in forested watersheds underlain by permafrost are likely to vary with changes in climatic regime that increase soil moisture and temperature. We examined the effects of temporal and spatial variations in soil temperature and moisture on DOC fluxes from the forest floor of contrasting north- and south-facing slopes in central Siberia. DOC fluxes increased throughout the growing season (June–September) on both slopes in 2002 and 2003. The most favorable combination of moisture content and temperature (deepest active soil layer) occurred in September, and we believe this was the primary driver of increased DOC concentrations and flux in autumn. Total DOC flux for June–September was 12.6–17.6 g C·m–2 on the south-facing slope and 4.6–8.9 g C·m–2 on the north-facing slope. DOC concentrations in forest floor leachates increased with increasing temperature on the north-facing slope, but were almost unaffected by temperature on the south-facing slope. Our results suggest that water input in midseason from melting of ice or precipitation events is the primary factor limiting DOC production. Significant positive correlations between amounts of precipitation and DOC flux were found on both slopes. Dilution of DOC concentrations by high precipitation volumes was observed only for the forest floor leachates collected from the north-facing slope. Our results suggest that global warming will result in increased DOC production in forest floors of permafrost regions, and that precipitation patterns will play an important role in determining the magnitude of these changes in DOC flux as well as its interannual variability. However, the longer-term response of soils and DOC flux to a warming climate will be driven by changes in vegetation and microbial communities as well as by the direct results of temperature and moisture conditions.

scholarly journals An integrated Dissolved Organic Carbon Dynamics Model (DOCDM 1.0): model development and a case study in the Alaskan Yukon River Basin

2015 ◽  
Vol 8 (12) ◽  
pp. 10411-10454 ◽  
Author(s):  
X. Lu ◽  
Q. Zhuang
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Overland Flow ◽  
Terrestrial Ecosystems ◽  
Carbon Dynamics ◽  
Water Infiltration ◽  
Dynamics Model ◽  
Study Region ◽  
Doc Export ◽  
Doc Production

Abstract. Quantitative understanding of the variation in dissolved organic carbon (DOC) is important to studying the terrestrial ecosystem carbon cycle. This study presents a process-based, dissolved organic carbon dynamics model (DOCDM 1.0) that couples the soil heat conduction, water flow, DOC production, mineralization and transport in both surface and subsurface of soil profile to quantify DOC dynamics in boreal terrestrial ecosystems. The model is first evaluated and then applied for a watershed in Alaska to investigate its DOC production and transport. We find that 42 and 27 % of precipitation infiltrates to soils in 2004, a warmer year, and in 1976, a colder year, respectively. Under warming conditions, DOC transported via overland flow does not show the expected decrease trend while the overland DOC yield shows a 4 % increase. The horizontal subsurface flow only accounts for 1–2 % of total water flux, but transports 30–50 % of DOC into rivers. Water flush due to water infiltration controls DOC transport. Snowmelt plays a noticeable role in DOC flush-out and DOC transport significantly depends on flowpaths in the study region. High soil temperature stimulates DOC production. The overland DOC export does not necessarily follow the DOC downward trend in surface water transport. Overall, this study shows that DOC export behavior is complex under changing temperature and hydrological conditions in cold-region watersheds. To adequately quantify DOC dynamics in northern high latitudes, more DOC and hydrological data are needed to better parameterize and test the developed model before extrapolating it to the region.

scholarly journals The effect of drought on dissolved organic carbon (DOC) release from peatland soil and vegetation sources

2017 ◽  
Author(s):  
Jonathan P. Ritson ◽  
Richard E. Brazier ◽  
Nigel J. D. Graham ◽  
Chris Freeman ◽  
Michael R. Templeton ◽  
...  
Keyword(s):  
Water Treatment ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Unit Weight ◽  
Catchment Management ◽  
Litter Layer ◽  
Peat Soils ◽  
Drought Tolerant ◽  
Doc Production ◽  
The Impact

Abstract. Drought conditions are expected to increase in frequency and severity as the climate changes, representing a threat to carbon sequestered in peat soils. Downstream water treatment works are also at risk of regulatory compliance failures and higher treatment costs due to the increase in riverine dissolved organic carbon (DOC) often observed after droughts. More frequent droughts may also shift dominant vegetation in peatlands from Sphagnum moss to more drought tolerant species. This paper examines the impact of drought on the production and treatability of DOC from four vegetation litters (Calluna vulgaris, Juncus effusus, Molinia caerulea and Sphagnum spp.) and a peat soil. We found that mild droughts caused a 39.6 % increase in DOC production from peat and that this DOC was harder to remove by conventional water treatment processes (coagulation/flocculation). Drought had no effect on DOC production from vegetation litters, however large variation was observed between typical peatland species (Sphagnum and Calluna) and drought tolerant grassland species (Juncus and Molinia), with the latter producing more DOC per unit weight. This would therefore suggest the increase in riverine DOC often observed post-drought is due entirely to soil microbial processes and DOC solubility rather than litter-layer effects. Long term shifts in species diversity may, therefore, be the most important impact of drought on litter layer DOC flux, whereas more immediate effects are observed in peat soils. These results provide evidence in support of catchment management which increases the resilience of peat soils to drought, such as ditch-blocking to raise water-tables.

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