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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.


Time series for chlorophyll-a (chl-a), total phosphorous (TP), total nitrogen (TN), and particulate organic nitrogen (PON) for the three reservoirs.(A) chlorophyll-a (μg L-1), (B) TP (mg P L-1), (C) TN (mg N L-1), and (D) PON (mg N L-1). The vertical dashed lines represent dates that received >1 cm precipitation. Precipitation during our study period totaled 14.78 cm, and average annual precipitation in San Diego County is 26.26 cm.
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pone.0140464.g005: Time series for chlorophyll-a (chl-a), total phosphorous (TP), total nitrogen (TN), and particulate organic nitrogen (PON) for the three reservoirs.(A) chlorophyll-a (μg L-1), (B) TP (mg P L-1), (C) TN (mg N L-1), and (D) PON (mg N L-1). The vertical dashed lines represent dates that received >1 cm precipitation. Precipitation during our study period totaled 14.78 cm, and average annual precipitation in San Diego County is 26.26 cm.

Mentions: Chlorophyll-a (μg L-1) concentration was consistently highest in Lake Murray ( = 4.017 μg L-1) and lower in the other two reservoirs (Miramar = 1.684 μg L-1; Poway = 1.516 μg L-1) and precipitation events did not have an effect on phytoplankton biomass (p > 0.05) [Fig 5A]. Chlorophyll-a was higher in Lake Murray in the winter than the summer, and higher in summer of 2013 than of 2014. The other two reservoirs showed consistent chlorophyll concentrations between 1–2 μg L-1 with no pronounced seasonality. Chlorophyll-a was inversely correlated with zooplankton community biomass and mean individual body size in Lake Murray (r = -0.323 and r = -0.515 respectively) but not in Lake Poway (r = 0.001 and r = -0.026 respectively) or Lake Miramar (r = -0.047 and r = -0.072 respectively). The seasonal patterns of pCO2 were not mirrored in chlorophyll-a within or among reservoirs, and chlorophyll-a was not retained as a significant predictor of pCO2 in the multiple regression model.


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

Adamczyk EM, Shurin JB - PLoS ONE (2015)

Time series for chlorophyll-a (chl-a), total phosphorous (TP), total nitrogen (TN), and particulate organic nitrogen (PON) for the three reservoirs.(A) chlorophyll-a (μg L-1), (B) TP (mg P L-1), (C) TN (mg N L-1), and (D) PON (mg N L-1). The vertical dashed lines represent dates that received >1 cm precipitation. Precipitation during our study period totaled 14.78 cm, and average annual precipitation in San Diego County is 26.26 cm.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0140464.g005: Time series for chlorophyll-a (chl-a), total phosphorous (TP), total nitrogen (TN), and particulate organic nitrogen (PON) for the three reservoirs.(A) chlorophyll-a (μg L-1), (B) TP (mg P L-1), (C) TN (mg N L-1), and (D) PON (mg N L-1). The vertical dashed lines represent dates that received >1 cm precipitation. Precipitation during our study period totaled 14.78 cm, and average annual precipitation in San Diego County is 26.26 cm.
Mentions: Chlorophyll-a (μg L-1) concentration was consistently highest in Lake Murray ( = 4.017 μg L-1) and lower in the other two reservoirs (Miramar = 1.684 μg L-1; Poway = 1.516 μg L-1) and precipitation events did not have an effect on phytoplankton biomass (p > 0.05) [Fig 5A]. Chlorophyll-a was higher in Lake Murray in the winter than the summer, and higher in summer of 2013 than of 2014. The other two reservoirs showed consistent chlorophyll concentrations between 1–2 μg L-1 with no pronounced seasonality. Chlorophyll-a was inversely correlated with zooplankton community biomass and mean individual body size in Lake Murray (r = -0.323 and r = -0.515 respectively) but not in Lake Poway (r = 0.001 and r = -0.026 respectively) or Lake Miramar (r = -0.047 and r = -0.072 respectively). The seasonal patterns of pCO2 were not mirrored in chlorophyll-a within or among reservoirs, and chlorophyll-a was not retained as a significant predictor of pCO2 in the multiple regression model.

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.