Quantifying photosynthetic rates of microphytobenthos using the triple isotope composition of dissolved oxygen

Stanley, Rachel H. R.; Howard, Evan M.

doi:10.4319/lom.2013.11.360

Cited by 7 publications

(10 citation statements)

References 68 publications

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“…NEP and respiration in the mesocosms were similar to rates from Waquoit Bay (Rao and Charette 2011;Stanley and Howard 2013), suggesting the experimental system adequately mimicked field conditions. Both trophic history and nutrient treatments influenced sediment metabolism (Table 2; Fig.…”

Section: Mesocosm Experimentsmentioning

confidence: 65%

Benthic biogeochemical responses to changing estuary trophic state and nutrient availability: A paired field and mesocosm experiment approach

Spivak

2014

Limnol. Oceanogr.

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To test how benthic biogeochemistry responds to changing nutrient availability and estuary trophic state, I conducted mesocosm and field experiments. In the mesocosm experiment, sediment cores from eutrophic and oligotrophic estuaries were incubated under high or low nutrient levels. Net production rates were greater in eutrophic vs. oligotrophic cores while respiration rates were greater in high nutrient treatments, indicating that sediment metabolism was affected by trophic history and nutrient availability. Sediment organic matter (SOM) composition was insensitive to the nutrient treatments but varied with trophic history as carbon : nitrogen ratios were lower, δ15N was higher, and algal and bacterial fatty acids (FAs) were more abundant in eutrophic sediments. In the field experiment, intact cores were reciprocally transplanted between eutrophic and oligotrophic estuaries and changes in SOM composition were followed over four months. SOM responses were more dramatic in cores transplanted to the oligotrophic vs. eutrophic estuary. In sediments moved from the eutrophic to oligotrophic estuary, carbon and nitrogen content as well as abundances of algal and bacterial FAs fell within one month. Conversely, sediment δ15N increased sharply while algal and bacterial FAs rose slightly in cores transplanted from the oligotrophic to eutrophic estuary. Different SOM responses between the experiments were likely due to direct vs. indirect effects of nutrient enrichment. Nutrient levels were manipulated in the mesocosm experiment while the estuaries differed in nutrients, macroalgal biomass, benthic animal communities, and oxygen levels. Consequently, sediment biogeochemical responses to watershed nutrient mitigation will likely follow broader changes in estuary habitat quality.

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Section: Mesocosm Experimentsmentioning

confidence: 65%

Benthic biogeochemical responses to changing estuary trophic state and nutrient availability: A paired field and mesocosm experiment approach

Spivak

2014

Limnol. Oceanogr.

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“…O 2 is distributed heterogeneously within the pond, reflecting the spatial variability of production; a survey of O 2 around the perimeter of the study pond revealed peak O 2 of 200% to 300% of saturation in areas with visible benthic algae or vascular plants. Photosynthetic O 2 production tracks photosynthetically active radiation (PAR, 400–700 nm; Stanley & Howard, ; Howard, ), and local O 2 supersaturation may form bubbles at nucleation points (such as photosynthesizing algae).…”

Section: Resultsmentioning

confidence: 99%

Using Noble Gases to Compare Parameterizations of Air‐Water Gas Exchange and to Constrain Oxygen Losses by Ebullition in a Shallow Aquatic Environment

et al. 2018

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Accurate determination of air-water gas exchange fluxes is critically important for calculating ecosystem metabolism rates from dissolved oxygen in shallow aquatic environments. We present a unique data set of the noble gases neon, argon, krypton, and xenon in a salt marsh pond to demonstrate how the dissolved noble gases can be used to quantify gas transfer processes and evaluate gas exchange parameterizations in shallow, near-shore environments. These noble gases are sensitive to a variety of physical processes, including bubbling. We thus additionally use this data set to demonstrate how dissolved noble gases can be used to assess the contribution of bubbling from the sediments (ebullition) to gas fluxes. We find that while literature gas exchange parameterizations do well in modeling more soluble gases, ebullition must be accounted for in order to correctly calculate fluxes of the lighter noble gases. In particular, for neon and argon, the ebullition flux is larger than the differences in the diffusive gas exchange flux estimated by four different wind speed-based parameterizations for gas exchange. We present an application of noble gas derived ebullition rates to improve estimates of oxygen metabolic fluxes in this shallow pond environment. Up to 21% of daily net oxygen production by photosynthesis may be lost from the pond via ebullition during some periods of biologically and physically produced supersaturation. Ebullition could be an important flux of oxygen and other gases that is measurable with noble gases in other shallow aquatic environments.

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“…Because the respiration and GPP rates from EC measurements are conservative estimates due to the assumption that daytime and nighttime respiration is equivalent (Hume et al 2011, Long et al 2013, further in situ research is required to evaluate how respiration rates influence C storage in seagrass beds. In future studies, the EC determination of respiration and GPP could be improved by comparisons with other techniques that specifically determine the daytime respiration or GPP, such as triple oxygen isotopes (Stanley & Howard 2013).…”

Section: Florida Bay Gradientsmentioning

confidence: 99%

Sub-tropical seagrass ecosystem metabolism measured by eddy covariance

Long¹,

Berg²,

McGlathery³

et al. 2015

Mar. Ecol. Prog. Ser.

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The metabolism of seagrass ecosystems was examined at 4 sites in south Florida, USA, using the eddy covariance technique under in situ conditions. Three sites were located across a phosphorus-driven productivity gradient to examine the combined effects of dynamic variables (irradiance, flow velocity) and state variables (sediment phosphorus and organic content, seagrass biomass) on ecosystem metabolism and trophic status. Gross primary production and respiration rates varied significantly across Florida Bay in the summer of 2012 with the lowest rates (64 and −53 mmol O 2 m −2 d −1 , respectively) in low-phosphorus sediments in the northeast and the highest (287 and −212 mmol O 2 m −2 d −1 , respectively) in the southwest where sediment phosphorus, organic matter, and seagrass biomass are higher. Seagrass eco systems offshore of the Florida Keys had similar large daily production and respiration rates (397 and −217 mmol O 2 m −2 d −1 , respectively) and were influenced by flow through the permeable offshore sediments. Across all sites, net ecosystem metabolism rates indicated that the seagrass ecosystems were autotrophic in the summertime. Substantial day-today variability in metabolic rates was found due to variations in irradiance and flow velocity. At all sites the relationship between photosynthesis and irradiance was linear and did not show any sign of saturation over the entire irradiance range (up to 1400 µmol photons m −2 s −1). This was likely due to the efficient use of light by the large photosynthetic surface area of the seagrass canopy, an effect which can only be examined by in situ measurements that integrate across all autotrophs in the seagrass ecosystem.

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Quantifying photosynthetic rates of microphytobenthos using the triple isotope composition of dissolved oxygen

Cited by 7 publications

References 68 publications

Benthic biogeochemical responses to changing estuary trophic state and nutrient availability: A paired field and mesocosm experiment approach

Benthic biogeochemical responses to changing estuary trophic state and nutrient availability: A paired field and mesocosm experiment approach

Using Noble Gases to Compare Parameterizations of Air‐Water Gas Exchange and to Constrain Oxygen Losses by Ebullition in a Shallow Aquatic Environment

Sub-tropical seagrass ecosystem metabolism measured by eddy covariance

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