Dataset: Change in denitrification - N2 flux
Deployment: Cheerystone_Inlet

Change in denitrification (N2 Flux) due to the oyster reef.

Principal Investigator:

Michael F. Piehler (University of North Carolina at Chapel Hill, UNC-Chapel Hill)

Co-Principal Investigator:

Mark J. Brush (Virginia Institute of Marine Science, VIMS)

Bongkeun Song (Virginia Institute of Marine Science, VIMS)

Craig Tobias (University of Connecticut, UConn - Avery Point)

Contact:

Michael F. Piehler (University of North Carolina at Chapel Hill, UNC-Chapel Hill)

BCO-DMO Data Manager:

Hannah Ake (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Project:

Microbial Regulation of Greenhouse Gas N2O Emission from Intertidal Oyster Reefs (Oyster Reef N2O Emission)

Current State:

Final no updates expected

Version:

Final

Version Date:

2017-06-06

Data URL:

https://www.bco-dmo.org/dataset-deployment/704368/data

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Description

Nutrient flux data from several landscapes in coastal North Carolina.

Methods & Sampling

Dataset acquisition description

Methodology from Smyth, A. R., Piehler, M. F. and Grabowski, J. H. (2015), Habitat context influences nitrogen removal by restored oyster reefs. J Appl Ecol, 52: 716–725. doi:10.1111/1365-2664.12435

Within 4 h of collection, sediment cores were set up in a continuous flow core incubation system to measure steady-state nutrient and dissolved gas fluxes, described in Piehler & Smyth (2011). Briefly, cores were sealed with gas-tight lids, which had an inflow and outflow port. Water from a reservoir was pulled over the cores at a flow rate of 1 mL min−1. Triplicate dissolved gases and duplicate dissolved inorganic nitrogen samples were collected from the outflow and inflow periodically over the next 24 h. To examine how sediments from different habitat contexts responded to nitrate pulses, nitrate concentration in the reservoir water was elevated with NaNO3 (~800 μm) after 48 h of sampling. Dissolved gas and inorganic nitrogen samples were then collected for an additional 48 h. Incubations were conducted in the dark and at ambient temperature (30 °C).

Water samples from laboratory experiments were analysed immediately upon collection for dissolved gasses (N2, O2 and Ar) with membrane inlet mass spectrometry (MIMS). Concentrations of dissolved N2 and O2 were determined using the ratio with Ar (Kana et al. 1994). Coefficients of variation for N2/Ar were 0·05% and 0·04% for O2/Ar. Water samples from laboratory experiments for dissolved nutrient determination were filtered through Whatman GF/F glass fibre filters (25 mm diameter, 0·7 μm nominal pore size) and frozen until analysis. Dissolved inorganic nutrients were analysed with a Lachat Quick-Chem 8000 automated ion analyser for [math formula] + [math formula] (reported as NOx) and [math formula] concentrations using standard protocols (Lachat Instruments, Milwaukee, WI, USA: [math formula] / [math formula] method 31-107-04-1-A, [math formula] method 31-107-06-1-A; detection limits: 0·04 μm NOx, 0·18 μm [math formula] ; CV(%): 0·9% NOx and 2·6% [math formula] ).

Upon completion of the incubations, the upper 2 cm of sediment in each core was sampled for organic matter content by mass difference from dried sediments before ignition (105 °C for 6 h) and after ignition (525 °C for 3 h).

Water Quality Data:

Data Processing Description

Dataset Processing Description

Fluxes across the sediment–water interface were calculated as (Co−Ci) × f/a, where Co is the outflow concentration (μmol L−1), Ci is the inflow concentration, f is the flow rate (0·06 L h−1), and a is the sediment surface area (0·0032 m2). Successive measurements from each core (triplicates for dissolved gas and duplicates for dissolved inorganic nutrients) were averaged to give core-specific values. This results in a net N2flux (gross denitrification – gross nitrogen fixation) and does not distinguish between the sources of N2. Consequently, denitrification refers to net N2 production. Oxygen fluxes were calculated using the concentrations of O2 obtained from the MIMS, presented as sediment oxygen demand (SOD), and serve as an indicator of organic matter quality, such that more labile organic matter is associated with higher SOD (Ferguson, Eyre & Gay 2003). To determine the influence of oyster reefs on sediment N2 fluxes, the change in denitrification between the control and reef habitat pair in each zone was calculated (Kellogg et al. 2014). Denitrification efficiency was computed as the percentage of the dissolved inorganic nitrogen efflux that was N2 (Piehler & Smyth 2011).

Statistical analyses were performed using r 2.13.1 (R Foundation for Statistical Computing 2011). Linear mixed-effects models (lme in R nlme package), where habitat nested in sampling location was included as a random effect for the intercept, were used to investigate the effects of oyster reef presence, habitat context, nitrate concentration (ambient vs. elevated) and the interaction between these factors on response variables. Fluxes of N2, NOx ( [math formula] + [math formula] ) [math formula] , denitrification efficiency and SOD were analysed using all three fixed effects. For sediment organic matter, only habitat context and reef presence were included as fixed effects. The effects of ambient vs. elevated nitrate concentration and habitat context on oyster reef-mediated changes in denitrification were also analysed with a mixed-effects model (fixed effects: nitrate concentration × habitat context; random effects: habitat nested in location). Relationships between oyster density and habitat context were made using a mixed-effects model (fixed effects: habitat context; random effects: habitat nested in location). Comparisons were conducted using linear contrasts and judged against an alpha level of 0·05. Interactions were assessed using Tukey's HSD (lsmeans in R lsmeans package). Assumptions of homogeneity were tested using Levene's tests. Regression analyses were used to investigate the effect of oyster density on denitrification. Models with the lowest Akaike's information criterion corrected for small sample sizes (AICc) were chosen.

BCO-DMO Processing Notes:

- column names reformatted to comply with BCO-DMO naming standards.
- lat and lon columns added to correspond with locations.

More information about this dataset deployment

Funding

Award Number	Funding Source
OCE-1233372	NSF Division of Ocean Sciences

Instruments

Isotope-ratio Mass Spectrometer

Supplied Name: IRMS

Supplied Description:

Instrument Type

Generic Name: Isotope-ratio Mass Spectrometer

Acronym: IR Mass Spec; IRMS

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/LAB16/

Generic Description:

The Isotope-ratio Mass Spectrometer is a particular type of mass spectrometer used to measure the relative abundance of isotopes in a given sample (e.g. VG Prism II Isotope Ratio Mass-Spectrometer).

Nutrient Autoanalyzer

Supplied Name: Lachat Quick-Chem 8000 automated ion analyzer

Supplied Description:

Used to analyze dissolved inorganic nutrients

Instrument Type

Generic Name: Nutrient Autoanalyzer

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/LAB04/

Generic Description:

Nutrient Autoanalyzer is a generic term used when specific type, make and model were not specified. In general, a Nutrient Autoanalyzer is an automated flow-thru system for doing nutrient analysis (nitrate, ammonium, orthophosphate, and silicate) on seawater samples.

Temperature Logger

Supplied Name: YSI 600 Series Sonde and Model 650 data logger

Supplied Description:

Used to collect water quality data

Instrument Type

Generic Name: Temperature Logger

Generic Description:

Records temperature data over a period of time.

Parameters

Supplied Name	Supplied description	Supplied Units	Standard Name
date	Date of collection; YYYY/MM/DD	unitless	date
area	Type of substrate where oysters were measured	unitless	site
location	PI issued location IDs that correspond to specific coordinates and experimental treatments	unitless	site
lat	Latitude	decimal degrees	lat
lon	Longitude	decimal degrees	lon
nutrients	Indication of whether or not experimental levels of nutrients were used	unitless	treatment
dN2	Change in denitrification (N2 flux) due to the oyster reef. Calculated by difference from reef and control in each location.	umol N m-2 hr-1	no_bcodmo_term

Database

Contribute Data

Dataset: Change in denitrification - N2 flux
Deployment: Cheerystone_Inlet

Dataset acquisition description

Dataset Processing Description

Database

Contribute Data

Dataset: Change in denitrification - N2 fluxDeployment: Cheerystone_Inlet

Dataset acquisition description

Dataset Processing Description

Dataset: Change in denitrification - N2 flux
Deployment: Cheerystone_Inlet