scholarly journals Net community production and stoichiometry of nutrient consumption in a pelagic ecosystem of a northern high latitude fjord: mesocosm CO<sub>2</sub> perturbation study

2012 ◽  
Vol 9 (8) ◽  
pp. 11705-11737 ◽  
Author(s):  
A. Silyakova ◽  
R. G. J. Bellerby ◽  
J. Czerny ◽  
K. G. Schulz ◽  
G. Nondal ◽  
...  
Keyword(s):  
Large Scale ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
P Uptake ◽  
Nutrient Addition ◽  
Net Community Production ◽  
Cumulative Change ◽  
Nutrient Consumption ◽  
Community Production ◽  
Three Phases

Abstract. Net community production (NCP) and ratios of carbon to nutrient consumption were studied during a large-scale mesocosm experiment on ocean acidification in Kongsfjorden, West Spitsbergen, during June–July 2010. Nutrient-deplete fjord water with natural phyto- and bacteriaplankton assemblages, enclosed in nine mesocosms of ~ 50 m3 volume, was exposed to pCO2 levels ranging from 185 to 1420 μatm on initial state. Mean values of pCO2 levels during experiment ranged from 175 to 1085 μatm in different mesocosms. Phytoplankton growth was stimulated by nutrient addition. In this study NCP is estimated as a cumulative change in dissolved inorganic carbon concentrations. Stoichiometric couping between inorganic carbon and nutrient is shown as a ratio of a cumulative NCP to a cumulative change in inorganic nutrients. Three peaks of chlorophyll a concentration occurred during the experiment. Accordingly the experiment was divided in three phases. Overall cumulative NCP was similar in all mesocosms by the final day of experiment. However, NCP varied among phases, showing variable response to CO2 perturbation. Carbon to nitrogen (C : N) and carbon to phosphorus (C : P) uptake ratios were estimated only for the period after nutrient addition (post-nutrient period). For the total post-nutrient period ratios were close to Redfield proportions, however varied from it in different phases. The response of C : N and C : P uptake ratios to CO2 perturbation was different for three phases of the experiment, reflecting variable NCP and dependence on changing microbial community. Through the variable NCP, C : N and C : P uptake ratios for 31 days of the experiment we show a flexibility of biogeochemical response establishing a strong microbial loop in Kongsfjorden under different CO2 scenarios.

scholarly journals Pelagic community production and carbon-nutrient stoichiometry under variable ocean acidification in an Arctic fjord

2013 ◽  
Vol 10 (7) ◽  
pp. 4847-4859 ◽  
Author(s):  
A. Silyakova ◽  
R. G. J. Bellerby ◽  
K. G. Schulz ◽  
J. Czerny ◽  
T. Tanaka ◽  
...  
Keyword(s):  
Phase I ◽  
Ocean Acidification ◽  
Phase Ii ◽  
Inorganic Carbon ◽  
Phytoplankton Community ◽  
P Uptake ◽  
Phase Iii ◽  
Cumulative Change ◽  
Carbon Concentrations ◽  
Community Production

Abstract. Net community production (NCP) and carbon to nutrient uptake ratios were studied during a large-scale mesocosm experiment on ocean acidification in Kongsfjorden, western Svalbard, during June–July 2010. Nutrient depleted fjord water with natural plankton assemblages, enclosed in nine mesocosms of ~ 50 m3 in volume, was exposed to pCO2 levels ranging initially from 185 to 1420 μatm. NCP estimations are the cumulative change in dissolved inorganic carbon concentrations after accounting for gas exchange and total alkalinity variations. Stoichiometric coupling between inorganic carbon and nutrient net uptake is shown as a ratio of NCP to a cumulative change in inorganic nutrients. Phytoplankton growth was stimulated by nutrient addition half way through the experiment and three distinct peaks in chlorophyll a concentration were observed during the experiment. Accordingly, the experiment was divided in three phases. Cumulative NCP was similar in all mesocosms over the duration of the experiment. However, in phases I and II, NCP was higher and in phase III lower at elevated pCO2. Due to relatively low inorganic nutrient concentration in phase I, C : N and C : P uptake ratios were calculated only for the period after nutrient addition (phase II and phase III). For the total post-nutrient period (phase II + phase III) ratios were close to Redfield, however they were lower in phase II and higher in phase III. Variability of NCP, C : N and C : P uptake ratios in different phases reflects the effect of increasing CO2 on phytoplankton community composition and succession. The phytoplankton community was composed predominantly of haptophytes in phase I, prasinophytes, dinoflagellates, and cryptophytes in phase II, and haptophytes, prasinophytes, dinoflagellates and chlorophytes in phase III (Schulz et al., 2013). Increasing ambient inorganic carbon concentrations have also been shown to promote primary production and carbon assimilation. For this study, it is clear that the pelagic ecosystem response to increasing CO2 is more complex than that represented in previous work, e.g. Bellerby et al. (2008). Carbon and nutrient uptake representation in models should, where possible, be more focused on individual plankton functional types as applying a single stoichiometry to a biogeochemical model with regard to the effect of increasing pCO2 may not always be optimal. The phase variability in NCP and stoichiometry may be better understood if CO2 sensitivities of the plankton's functional type biogeochemical uptake kinetics and trophic interactions are better constrained.

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 Fluxes of carbon and nutrients to the Iceland Sea surface layer and inferred primary productivity and stoichiometry

2014 ◽  
Vol 11 (11) ◽  
pp. 15399-15433
Author(s):  
E. Jeansson ◽  
R. G. J. Bellerby ◽  
I. Skjelvan ◽  
H. Frigstad ◽  
S. R. Ólafsdóttir ◽  
...  
Keyword(s):  
Surface Layer ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Vertical Mixing ◽  
Sea Surface ◽  
Net Community Production ◽  
Horizontal Advection ◽  
Vertical Fluxes ◽  
Biological Uptake ◽  
Community Production

Abstract. Fluxes of carbon and nutrients to the upper 100 m of the Iceland Sea are evaluated. The study utilises hydro-chemical data from the Iceland Sea time-series station (68.00° N, 12.67° W), for the years between 1993 and 2006. By comparing data of dissolved inorganic carbon (DIC) and nutrients in the surface layer (upper 100 m), and a sub-surface layer (100–200 m), we calculate monthly deficits in the surface, and use these to deduce the surface layer fluxes that affect the deficits: vertical mixing, horizontal advection, air–sea exchange, and biological activity. The deficits show a clear seasonality with a minimum in winter, when the mixed layer is at the deepest, and a maximum in early autumn, when biological uptake has removed much of the nutrients. The annual vertical fluxes of DIC and nitrate amounts to 1.7 ± 0.3 and 0.23 ± 0.07 mol m−2 yr−1, respectively, and the annual air–sea uptake of atmospheric CO2 is 4.4 ± 1.1 mol m−2 yr−1. The biologically driven changes in DIC during the year relates to net community production (NCP), and the net annual NCP corresponds to export production, and is here calculated to 6.1 ± 0.9 mol C m−2 yr−1. The typical, median C : N ratio during the period of net community uptake is 11, and thus clearly higher than Redfield, but is varying during the season.

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 Fluxes of carbon and nutrients to the Iceland Sea surface layer and inferred primary productivity and stoichiometry

2015 ◽  
Vol 12 (3) ◽  
pp. 875-885 ◽  
Author(s):  
E. Jeansson ◽  
R. G. J. Bellerby ◽  
I. Skjelvan ◽  
H. Frigstad ◽  
S. R. Ólafsdóttir ◽  
...  
Keyword(s):  
Surface Layer ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Vertical Mixing ◽  
Sea Surface ◽  
Net Community Production ◽  
Horizontal Advection ◽  
Vertical Fluxes ◽  
Community Production

Abstract. This study evaluates long-term mean fluxes of carbon and nutrients to the upper 100 m of the Iceland Sea. The study utilises hydro-chemical data from the Iceland Sea time series station (68.00° N, 12.67° W), for the years between 1993 and 2006. By comparing data of dissolved inorganic carbon (DIC) and nutrients in the surface layer (upper 100 m), and a sub-surface layer (100–200 m), we calculate monthly deficits in the surface, and use these to deduce the long-term mean surface layer fluxes that affect the deficits: vertical mixing, horizontal advection, air–sea exchange, and biological activity. The deficits show a clear seasonality with a minimum in winter, when the mixed layer is at the deepest, and a maximum in early autumn, when biological uptake has removed much of the nutrients. The annual vertical fluxes of DIC and nitrate amounts to 2.9 ± 0.5 and 0.45 ± 0.09 mol m−2 yr−1, respectively, and the annual air–sea uptake of atmospheric CO2 is 4.4 ± 1.1 mol C m−2 yr−1. The biologically driven changes in DIC during the year relates to net community production (NCP), and the net annual NCP corresponds to export production, and is here calculated as 7.3 ± 1.0 mol C m−2 yr−1. The typical, median C : N ratio during the period of net community uptake is 9.0, and clearly higher than the Redfield ratio, but is varying during the season.

Organic and inorganic whole system metabolism in two acidified coastal systems in Ireland

2020 ◽  
Author(s):  
Maria Teresa Guerra ◽  
Carlos Rocha
Keyword(s):  
Ocean Acidification ◽  
Dissolved Inorganic Carbon ◽  
Total Alkalinity ◽  
Carbonate System ◽  
Net Community Production ◽  
Coastal Acidification ◽  
Autumn And Winter ◽  
System Metabolism ◽  
Internal Buffer ◽  
Community Production

&lt;p&gt;Organic and inorganic whole system metabolism for two Irish coastal areas were compared to evaluate carbonate system resilience to acidification. The two systems are characterized by contrasting watershed input types and composition. Kinvara Bay is fed by Submarine Groundwater Discharge (SGD) derived from a karstic catchment while Killary Harbour is fed by river discharge draining a siliciclastic catchment. Freshwater sources to sea have distinct Total Alkalinity (TA) and Dissolved Inorganic Carbon (DIC) concentrations, higher and lower than the open ocean, respectively, but both evidence seasonally variable low pH, ranging from 6.20 to 7.50. Retention of TA and DIC was calculated for the two areas using LOICZ methodology. In Kinvara bay, annually averaged retention of DIC was greater than for TA (5 &amp;#215; 10&lt;sup&gt;4&lt;/sup&gt; and 1.5 &amp;#215; 10&lt;sup&gt;5&lt;/sup&gt; mol d&lt;sup&gt;-1&lt;/sup&gt;), suggesting the system is acidifying further. Conversely, Killary Harbour shows negative TA and DIC retention, with DIC:TA &lt;1, suggesting an internal buffer against ocean acidification is operating.&lt;/p&gt;&lt;p&gt;Net Community Production (NCP) was calculated for both systems using Dissolved Oxygen data. Subsequently, we estimated Net Community Calcification (NCC) from the ratio between TA and DIC. NCP was always positive in Killary Harbour with an average of 318 mmol O&lt;sub&gt;2&lt;/sub&gt; m&lt;sup&gt;-2 &lt;/sup&gt;d&lt;sup&gt;-1&lt;/sup&gt; (equivalent to 89 mol C m&lt;sup&gt;-2&lt;/sup&gt; y&lt;sup&gt;-1&lt;/sup&gt;). However, Kinvara Bay shows relatively lower positive NCP in spring and summer (average of 46 mmol O&lt;sub&gt;2&lt;/sub&gt; m&lt;sup&gt;-2&lt;/sup&gt; d&lt;sup&gt;-1&lt;/sup&gt;), but negative NCP in autumn and winter. Therefore, Kinvara Bay&amp;#8217;s Total Organic Carbon (TOC) production was low, at ~21 g m&lt;sup&gt;-2&lt;/sup&gt; y&lt;sup&gt;-1&lt;/sup&gt; and not enough to overcome acidification driven by the SGD source composition. These results emphasize the complexity of interactions between the drivers of coastal acidification rate, affecting our ability to accurately assess the resilience of the carbonate system in these areas to ocean acidification pressure in the future.&lt;/p&gt;

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