scholarly journals Dynamics of dissolved inorganic carbon and aquatic metabolism in the Tana River Basin, Kenya

2013 ◽  
Vol 10 (3) ◽  
pp. 5175-5221 ◽  
Author(s):  
F. Tamooh ◽  
A. V. Borges ◽  
F. J. R. Meysman ◽  
K. Van Den Meersche ◽  
F. Dehairs ◽  
...  
Keyword(s):  
Primary Production ◽  
Water Column ◽  
Chlorophyll A ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Community Respiration ◽  
Wet Season ◽  
Stream Community ◽  
Tana River ◽  
Diurnal Fluctuations

Abstract. A basin-wide study was conducted in the Tana River Basin (Kenya), in February 2008 (dry season), September–November 2009 (wet season), and June–July 2010 (end of the wet season) to assess the dynamics and sources of dissolved inorganic carbon (DIC) as well as to quantify CO2 fluxes, community respiration (R), and primary production (P). Samples were collected along the altitudinal gradient (from 3600 m to 8 m) in several headwater streams, reservoirs (Kamburu and Masinga), and main Tana River. DIC concentrations ranged from 0.2 mmol L–1 to 4.8 mmol L–1 but with exceptionally high values (3.5 ± 1.6 mmol L–1) in Nyambene Hills tributaries. The wide range of δ13CDIC values (−15.0‰ to −2.4‰) indicate variable sources of DIC with headwater streams recording higher signatures compared to main Tana River. With few exceptions, the entire riverine network was supersaturated in CO2, implying the system is a net source of CO2 to the atmosphere. pCO2 values were generally higher in the lower main Tana River compared to headwater tributaries, opposite to the pattern typically observed in other river networks. This was attributed to high suspended sediment in the main Tana River fuelling in-stream community respiration and net heterotrophy. This was particularly evident during 2009 wet season campaign (median pCO2 of 1432 ppm) compared to 2010 end of wet season (1002 ppm) and 2008 dry season (579 ppm). First-order estimates show in-stream community respiration was responsible for the bulk of total CO2 evasion (59% to 89%) in main Tana River while in tributaries respiration accounted for 4% to 52% of total CO2 evasion, suggesting CO2evasion in tributaries was sustained by processes than respiration, such as CO2-oversaturated groundwater input. While sediment loads increase downstream and thus light availability decreases in the water column, both chlorophyll a (0.2 μg L–1 to 9.6 μg L–1) and primary production (0.004 μmol L–1 h–1 to 7.38 μmol L–1 h–1) increased consistently downstream. Diurnal fluctuations of biogeochemical processes were examined at three different sites along the river continuum (headwater, reservoir, and mainstream), and were found to be substantial only in the headwater stream, moderate in the reservoir and not detectable at main Tana River. The pronounced diurnal fluctuations observed in the headwater stream were largely regulated by periphyton as deduced from the low chlorophyll a in the water column.

scholarly journals Dynamics of dissolved inorganic carbon and aquatic metabolism in the Tana River basin, Kenya

2013 ◽  
Vol 10 (11) ◽  
pp. 6911-6928 ◽  
Author(s):  
F. Tamooh ◽  
A. V. Borges ◽  
F. J. R. Meysman ◽  
K. Van Den Meersche ◽  
F. Dehairs ◽  
...  
Keyword(s):  
Primary Production ◽  
Water Column ◽  
Chlorophyll A ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Community Respiration ◽  
Wet Season ◽  
Stream Community ◽  
Tana River ◽  
Diurnal Fluctuations

Abstract. A basin-wide study was conducted in the Tana River basin (Kenya) in February 2008 (dry season), September–November 2009 (wet season) and June–July 2010 (end of the wet season) to assess the dynamics and sources of dissolved inorganic carbon (DIC) as well as to quantify CO2 fluxes, community respiration (R), and primary production (P). Samples were collected along the altitudinal gradient (from 3600 to 8 m) in several headwater streams, reservoirs (Kamburu and Masinga), and the Tana River mainstream. DIC concentrations ranged from 0.2 to 4.8 mmol L−1, with exceptionally high values (3.5 ± 1.6 mmol L−1) in Nyambene Hills tributaries. The wide range of δ13CDIC values (−15.0 to −2.4‰) indicate variable sources of DIC, with headwater streams recording more positive signatures compared to the Tana River mainstream. With with only a few exceptions, the entire riverine network was supersaturated in CO2, implying the system is a net source of CO2 to the atmosphere. pCO2 values were generally higher in the lower Tana River mainstream compared to headwater tributaries, opposite to the pattern typically observed in other river networks. This was attributed to high suspended sediment in the Tana River mainstream fuelling in-stream community respiration and net heterotrophy. This was particularly evident during the 2009 wet season campaign (median pCO2 of 1432 ppm) compared to the 2010 end of the wet season (1002 ppm) and 2008 dry season (579 ppm). First-order estimates show that in-stream community respiration was responsible for the bulk of total CO2 evasion (77 to 114%) in the Tana River mainstream, while in the tributaries, this could only account for 5 to 68% of total CO2 evasion. This suggests that CO2 evasion in the tributaries was to a substantial degree sustained by benthic mineralisation and/or lateral inputs of CO2-oversaturated groundwater. While sediment loads increased downstream and thus light availability decreased in the water column, both chlorophyll a (0.2 to 9.6 μg L−1) and primary production (0.004 to 7.38 μmol C L−1 h−1) increased consistently downstream. Diurnal fluctuations of biogeochemical processes were examined at three different sites along the river continuum (headwater, reservoir and mainstream), and were found to be substantial only in the headwater stream, moderate in the reservoir and not detectable in the Tana River mainstream. The pronounced diurnal fluctuations observed in the headwater stream were largely regulated by periphyton as deduced from the low chlorophyll a in the water column.

Vertical Variability of Primary Production and Chlorophyll a in the Kara Sea in the Middle of Summer: Contribution of Subsurface Maxima to the Water Column Values

Oceanology ◽  
2021 ◽  
Vol 61 (5) ◽  
pp. 645-661
Author(s):  
A. B. Demidov ◽  
V. I. Gagarin ◽  
E. V. Eremeeva ◽  
V. A. Artemiev ◽  
A. A. Polukhin ◽  
...  
Keyword(s):  
Primary Production ◽  
Water Column ◽  
Chlorophyll A ◽  
Kara Sea ◽  
Vertical Variability

scholarly journals Texas A&M University Radiocarbon Dates IV

Radiocarbon ◽  
1978 ◽  
Vol 20 (3) ◽  
pp. 455-460 ◽  
Author(s):  
R A Parker ◽  
W M Sackett
Keyword(s):  
Water Column ◽  
Mississippi River ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
River Delta ◽  
Cariaco Basin ◽  
Mississippi River Delta ◽  
Radiocarbon Dates ◽  
Carbonate Carbon ◽  
Total Dissolved Inorganic Carbon

Organic and carbonate carbon in sediments deposited in the Cariaco Basin and on the Mississippi River Delta and the total dissolved inorganic carbon in four water column profiles comprise the samples in this list. Except as noted below the samples were processed using the benzene synthesis and other procedures described by Mathews, et al (1972).

Linkage between Epilithic Algal Growth and Water Column Nutrients in Softwater Lakes

1992 ◽  
Vol 49 (8) ◽  
pp. 1641-1649 ◽  
Author(s):  
G. Winfield Fairchild ◽  
John W. Sherman
Keyword(s):  
Nutrient Limitation ◽  
Water Column ◽  
Chlorophyll A ◽  
Standing Crop ◽  
Crop Production ◽  
Dissolved Inorganic Carbon ◽  
Inorganic Nitrogen ◽  
Algal Growth ◽  
Acidic Lakes ◽  
Softwater Lakes

We examined the dependence of epilithic algal standing crop, production, and nutrient limitation upon water column nutrients in 12 softwater lakes of northeastern Pennsylvania. Elevated dissolved inorganic nitrogen accompanied low dissolved inorganic carbon in the more acidic lakes, while P varied little within the study area. The growth of epilithon on clay flower pot substrata diffusing combinations of N (NaNO3), P (Na2HPO4), and C (NaHCO3) was compared with growth on control substrata to evaluate which of the three nutrients limited growth in each lake. Standing crop accrual as chlorophyll a on control substrata averaged 0.8 μg/cm2, with little variation among lakes. Nutrient limitation of growth, however, was strongly related to lake alkalinity. Chlorophyll a was typically enhanced by N and/or P only in lakes with alkalinity greater than ~100 μeq/L and responded strongly to C enrichment in the two most acidic lakes. Combined addition of all three nutrients produced the largest chlorophyll a accrual in all 12 lakes. Invertebrate grazer biomass, dominated by chironomids in the more acidic lakes and by snails at higher alkalinity, was negatively related to chlorophyll a on these NPC substrata (r = −0.57, p = 0.05) and may have reduced algal standing crop well below nutrient-sustainable levels in some lakes.

scholarly journals Seasonal distribution of dissolved inorganic carbon and net community production on the Bering Sea shelf

2010 ◽  
Vol 7 (1) ◽  
pp. 251-300 ◽  
Author(s):  
J. T. Mathis ◽  
J. N. Cross ◽  
N. R. Bates ◽  
S. B. Moran ◽  
M. W. Lomas ◽  
...  
Keyword(s):  
Primary Production ◽  
Bering Sea ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Inner Shelf ◽  
Net Community Production ◽  
Important Indicator ◽  
Bering Sea Shelf ◽  
Community Production ◽  
The Bering Sea

Abstract. The southeastern shelf of the Bering Sea is one of the ocean's most productive ecosystems and sustains more than half of the total US fish landings annually. However, the character of the Bering Sea shelf ecosystem has undergone a dramatic shift over the last several decades, causing notable increases in the dominance of temperate features coupled to the decline of arctic species and decreases in the abundance of commercially important organisms. In order to assess the current state of primary production in the southeastern Bering Sea, we measured the spatio-temporal distribution and controls on dissolved inorganic carbon (DIC) concentrations in spring and summer of 2008 across six shelf domains defined by differing biogeochemical characteristics. DIC concentrations were tightly coupled to salinity in spring and ranged from ~1900 μmol kg−1 over the inner shelf to ~2400 μmol kg−1 in the deeper waters of the Bering Sea. In summer, DIC concentrations were lower due to dilution from sea ice melt and primary production. Concentrations were found to be as low ~1800 μmol kg−1 over the inner shelf. We found that DIC concentrations were drawn down 30–150 μmol kg−1 in the upper 30 m of the water column due to primary production between the spring and summer occupations. Using the seasonal drawdown of DIC, estimated rates of net community production (NCP) on the inner, middle, and outer shelf averaged 28±10 mmol C m−2 d−1. However, higher rates of NCP (40–47 mmol C m−2 d−1) were observed in the ''Green Belt'' where the greatest confluence of nutrient-rich basin water and iron-rich shelf water occurs. We estimated that in 2008, total productivity across the shelf was on the order of ~105 Tg C yr−1. Due to the paucity of consistent, comparable productivity data, it is impossible at this time to quantify whether the system is becoming more or less productive. However, as changing climate continues to modify the character of the Bering Sea, we have shown that NCP can be an important indicator of how the ecosystem is functioning.

scholarly journals Seasonal distribution of dissolved inorganic carbon and net community production on the Bering Sea shelf

2010 ◽  
Vol 7 (5) ◽  
pp. 1769-1787 ◽  
Author(s):  
J. T. Mathis ◽  
J. N. Cross ◽  
N. R. Bates ◽  
S. Bradley Moran ◽  
M. W. Lomas ◽  
...  
Keyword(s):  
Primary Production ◽  
Bering Sea ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Inner Shelf ◽  
Net Community Production ◽  
Important Indicator ◽  
Carbonate Formation ◽  
Community Production ◽  
The Bering Sea

Abstract. In order to assess the current state of net community production (NCP) in the southeastern Bering Sea, we measured the spatio-temporal distribution and controls on dissolved inorganic carbon (DIC) concentrations in spring and summer of 2008 across six shelf domains defined by differing biogeochemical characteristics. DIC concentrations were tightly coupled to salinity in spring and ranged from ~1900 μmoles kg−1 over the inner shelf to ~2400 μmoles kg−1 in the deeper waters of the Bering Sea. In summer, DIC concentrations were lower due to dilution from sea ice melt, terrestrial inputs, and primary production. Concentrations were found to be as low ~1800 μmoles kg−1 over the inner shelf. We found that DIC concentrations were drawn down 30–150 μmoles kg−1 in the upper 30 m of the water column due to primary production and calcium carbonate formation between the spring and summer occupations. Using the seasonal drawdown of DIC, estimated rates of NCP on the inner, middle, and outer shelf averaged 28 ± 9 mmoles C m−2 d−1. However, higher rates of NCP (40–47 mmoles C m−2 d−1) were observed in the "Green Belt" where the greatest confluence of nutrient-rich basin water and iron-rich shelf water occurs. We estimated that in 2008, total NCP across the shelf was on the order of ~96 Tg C yr−1. Due to the paucity of consistent, comparable productivity data, it is impossible at this time to quantify whether the system is becoming more or less productive. However, as changing climate continues to modify the character of the Bering Sea, we have shown that NCP can be an important indicator of how the ecosystem is functioning.

scholarly journals Winter measurements of biogeochemical parameters in the Rockall Trough (2009–2012)

2013 ◽  
Vol 6 (2) ◽  
pp. 389-409
Author(s):  
T. McGrath ◽  
C. Kivimäe ◽  
E. McGovern ◽  
R. R. Cave ◽  
E. Joyce
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Total Alkalinity ◽  
Dissolved Inorganic Nutrients ◽  
Chemical Signatures ◽  
Rockall Trough ◽  
Biogeochemical Parameters ◽  
Oxidised Nitrogen

Abstract. This paper describes the sampling and analysis of biogeochemical parameters collected in the Rockall Trough in January/February of 2009, 2010, 2011 and 2012. Sampling was carried out across two transects, one southern and one northern transect each year. Samples for dissolved inorganic carbon (DIC) and total alkalinity (TA) were taken alongside salinity, dissolved oxygen and dissolved inorganic nutrients (total-oxidised nitrogen, nitrite, phosphate and silicate) to describe the chemical signatures of the various water masses in the region. These were taken at regular intervals through the water column. The 2009 and 2010 data are available on the CDIAC database.

scholarly journals Estimates of ikaite export from sea ice to the underlying seawater in a sea ice–seawater mesocosm

2016 ◽  
Vol 10 (5) ◽  
pp. 2173-2189 ◽  
Author(s):  
Nicolas-Xavier Geilfus ◽  
Ryan J. Galley ◽  
Brent G. T. Else ◽  
Karley Campbell ◽  
Tim Papakyriakou ◽  
...  
Keyword(s):  
Sea Ice ◽  
Water Column ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Carbon Dynamics ◽  
Total Alkalinity ◽  
Main Process ◽  
Saturation State ◽  
Ice Growth ◽  
Ice Melt

Abstract. The precipitation of ikaite and its fate within sea ice is still poorly understood. We quantify temporal inorganic carbon dynamics in sea ice from initial formation to its melt in a sea ice–seawater mesocosm pool from 11 to 29 January 2013. Based on measurements of total alkalinity (TA) and total dissolved inorganic carbon (TCO2), the main processes affecting inorganic carbon dynamics within sea ice were ikaite precipitation and CO2 exchange with the atmosphere. In the underlying seawater, the dissolution of ikaite was the main process affecting inorganic carbon dynamics. Sea ice acted as an active layer, releasing CO2 to the atmosphere during the growth phase, taking up CO2 as it melted and exporting both ikaite and TCO2 into the underlying seawater during the whole experiment. Ikaite precipitation of up to 167 µmolkg−1 within sea ice was estimated, while its export and dissolution into the underlying seawater was responsible for a TA increase of 64–66 µmolkg−1 in the water column. The export of TCO2 from sea ice to the water column increased the underlying seawater TCO2 by 43.5 µmolkg−1, suggesting that almost all of the TCO2 that left the sea ice was exported to the underlying seawater. The export of ikaite from the ice to the underlying seawater was associated with brine rejection during sea ice growth, increased vertical connectivity in sea ice due to the upward percolation of seawater and meltwater flushing during sea ice melt. Based on the change in TA in the water column around the onset of sea ice melt, more than half of the total ikaite precipitated in the ice during sea ice growth was still contained in the ice when the sea ice began to melt. Ikaite crystal dissolution in the water column kept the seawater pCO2 undersaturated with respect to the atmosphere in spite of increased salinity, TA and TCO2 associated with sea ice growth. Results indicate that ikaite export from sea ice and its dissolution in the underlying seawater can potentially hamper the effect of oceanic acidification on the aragonite saturation state (Ωaragonite) in fall and in winter in ice-covered areas, at the time when Ωaragonite is smallest.

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