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Seasonal Changes in Plankton Food Web Structure and Carbon Dioxide Flux from Southern California Reservoirs.

Adamczyk EM, Shurin JB - PLoS ONE (2015)

Bottom Line: We sampled three reservoirs in San Diego, California, weekly for one year.We found that San Diego reservoirs are most often undersaturated with CO2 with respect to the atmosphere and are estimated to absorb on average 3.22 mmol C m(-2) day(-1). pCO2 was highest in the winter and lower in the summer, indicating seasonal shifts in the magnitudes of photosynthesis and respiration associated with day length, temperature and water inputs.Our data indicate that reservoirs of semi-arid environments may primarily function as carbon sinks, and that carbon flux varies seasonally but is unrelated to nutrient or DOC availability, or the abundances of phytoplankton or zooplankton.

View Article: PubMed Central - PubMed

Affiliation: Division of Biological Sciences, Section of Ecology, Behavior and Evolution, University of California San Diego, La Jolla, California, United States of America.

ABSTRACT
Reservoirs around the world contribute to cycling of carbon dioxide (CO2) with the atmosphere, but there is little information on how ecosystem processes determine the absorption or emission of CO2. Reservoirs are the most prevalent freshwater systems in the arid southwest of North America, yet it is unclear whether they sequester or release CO2 and therefore how water impoundment impacts global carbon cycling. We sampled three reservoirs in San Diego, California, weekly for one year. We measured seasonal variation in the abundances of bacteria, phytoplankton, and zooplankton, as well as water chemistry (pH, nutrients, ions, dissolved organic carbon [DOC]), which were used to estimate partial pressure of CO2 (pCO2), and CO2 flux. We found that San Diego reservoirs are most often undersaturated with CO2 with respect to the atmosphere and are estimated to absorb on average 3.22 mmol C m(-2) day(-1). pCO2 was highest in the winter and lower in the summer, indicating seasonal shifts in the magnitudes of photosynthesis and respiration associated with day length, temperature and water inputs. Abundances of microbes (bacteria) peaked in the winter along with pCO2, while phytoplankton, nutrients, zooplankton and DOC were all unrelated to pCO2. Our data indicate that reservoirs of semi-arid environments may primarily function as carbon sinks, and that carbon flux varies seasonally but is unrelated to nutrient or DOC availability, or the abundances of phytoplankton or zooplankton.

No MeSH data available.


Related in: MedlinePlus

Partial regression plots of the significant drivers of pH and pCO2 across all reservoirs.Drivers were identified by the model averaging procedure pH versus (A) total nitrogen (mg N L-1) and (B) bacteria abundance (# L-1), and pCO2 versus (C) zooplankton community biomass (mg L-1) and (D) particulate organic nitrogen (mg N L-1). Symbols indicate the reservoir as shown in the legend.
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pone.0140464.g003: Partial regression plots of the significant drivers of pH and pCO2 across all reservoirs.Drivers were identified by the model averaging procedure pH versus (A) total nitrogen (mg N L-1) and (B) bacteria abundance (# L-1), and pCO2 versus (C) zooplankton community biomass (mg L-1) and (D) particulate organic nitrogen (mg N L-1). Symbols indicate the reservoir as shown in the legend.

Mentions: The model to predict pCO2 based on the variables used to calculate it (water temperature, total alkalinity, pH, and total phosphorus) identified pH as the dominant factor determining pCO2. pH explained 64% of the variation in pCO2, while the other variables explained only between <1% (total phosphorus) and 17% (total alkalinity) of the variation. We therefore constructed a model to predict pH based on the other bio-physical variables that were not included in the calculation of pCO2. The variables included in the top six models to predict pH were TN and bacteria (Fig 3A and 3B). Chlorophyll-a, POC, PON, and DOC were also included in the best six models to predict pH, but none contributed significantly to the fit of the data (Table 2A). The most important variables to predict pCO2 identified by the model averaging were zooplankton biomass and PON (Fig 3C and 3D). Other variables included in the top six best fit models to predict pCO2 included TN, bacterial abundance, and chlorophyll-a; however, none of these contributed significantly to the fit of the model (Table 2B). Zooplankton biomass and PON were not correlated in our data set (Pearson correlation = 0.024, p = 0.779).


Seasonal Changes in Plankton Food Web Structure and Carbon Dioxide Flux from Southern California Reservoirs.

Adamczyk EM, Shurin JB - PLoS ONE (2015)

Partial regression plots of the significant drivers of pH and pCO2 across all reservoirs.Drivers were identified by the model averaging procedure pH versus (A) total nitrogen (mg N L-1) and (B) bacteria abundance (# L-1), and pCO2 versus (C) zooplankton community biomass (mg L-1) and (D) particulate organic nitrogen (mg N L-1). Symbols indicate the reservoir as shown in the legend.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608793&req=5

pone.0140464.g003: Partial regression plots of the significant drivers of pH and pCO2 across all reservoirs.Drivers were identified by the model averaging procedure pH versus (A) total nitrogen (mg N L-1) and (B) bacteria abundance (# L-1), and pCO2 versus (C) zooplankton community biomass (mg L-1) and (D) particulate organic nitrogen (mg N L-1). Symbols indicate the reservoir as shown in the legend.
Mentions: The model to predict pCO2 based on the variables used to calculate it (water temperature, total alkalinity, pH, and total phosphorus) identified pH as the dominant factor determining pCO2. pH explained 64% of the variation in pCO2, while the other variables explained only between <1% (total phosphorus) and 17% (total alkalinity) of the variation. We therefore constructed a model to predict pH based on the other bio-physical variables that were not included in the calculation of pCO2. The variables included in the top six models to predict pH were TN and bacteria (Fig 3A and 3B). Chlorophyll-a, POC, PON, and DOC were also included in the best six models to predict pH, but none contributed significantly to the fit of the data (Table 2A). The most important variables to predict pCO2 identified by the model averaging were zooplankton biomass and PON (Fig 3C and 3D). Other variables included in the top six best fit models to predict pCO2 included TN, bacterial abundance, and chlorophyll-a; however, none of these contributed significantly to the fit of the model (Table 2B). Zooplankton biomass and PON were not correlated in our data set (Pearson correlation = 0.024, p = 0.779).

Bottom Line: We sampled three reservoirs in San Diego, California, weekly for one year.We found that San Diego reservoirs are most often undersaturated with CO2 with respect to the atmosphere and are estimated to absorb on average 3.22 mmol C m(-2) day(-1). pCO2 was highest in the winter and lower in the summer, indicating seasonal shifts in the magnitudes of photosynthesis and respiration associated with day length, temperature and water inputs.Our data indicate that reservoirs of semi-arid environments may primarily function as carbon sinks, and that carbon flux varies seasonally but is unrelated to nutrient or DOC availability, or the abundances of phytoplankton or zooplankton.

View Article: PubMed Central - PubMed

Affiliation: Division of Biological Sciences, Section of Ecology, Behavior and Evolution, University of California San Diego, La Jolla, California, United States of America.

ABSTRACT
Reservoirs around the world contribute to cycling of carbon dioxide (CO2) with the atmosphere, but there is little information on how ecosystem processes determine the absorption or emission of CO2. Reservoirs are the most prevalent freshwater systems in the arid southwest of North America, yet it is unclear whether they sequester or release CO2 and therefore how water impoundment impacts global carbon cycling. We sampled three reservoirs in San Diego, California, weekly for one year. We measured seasonal variation in the abundances of bacteria, phytoplankton, and zooplankton, as well as water chemistry (pH, nutrients, ions, dissolved organic carbon [DOC]), which were used to estimate partial pressure of CO2 (pCO2), and CO2 flux. We found that San Diego reservoirs are most often undersaturated with CO2 with respect to the atmosphere and are estimated to absorb on average 3.22 mmol C m(-2) day(-1). pCO2 was highest in the winter and lower in the summer, indicating seasonal shifts in the magnitudes of photosynthesis and respiration associated with day length, temperature and water inputs. Abundances of microbes (bacteria) peaked in the winter along with pCO2, while phytoplankton, nutrients, zooplankton and DOC were all unrelated to pCO2. Our data indicate that reservoirs of semi-arid environments may primarily function as carbon sinks, and that carbon flux varies seasonally but is unrelated to nutrient or DOC availability, or the abundances of phytoplankton or zooplankton.

No MeSH data available.


Related in: MedlinePlus