Journal article
Seasonal drivers of carbon dioxide dynamics in a hydrologically modified subtropical tidal river and estuary (Caboolture River, Australia)
Journal of Geophysical Research : Biogeosciences, Vol.123(6), pp.1827-1849
20/04/2018
Metrics
30 Record Views
UN Sustainable Development Goals (SDGs)
This output has contributed to the advancement of the following goals:
Source: InCites
Abstract
Estuaries are dynamic hot spots for carbon cycling and atmospheric evasion. Here we assess the dynamics and drivers of CO2 in a hydrologically modified subtropical Australian estuary. Over 1 year, 10 high‐resolution spatial surveys of pCO2, radon, chromophoric dissolved organic matter, chlorophyll a, and physicochemical parameters were conducted from the estuary mouth to a weir located 25 km upstream. The riverine respiratory quotient revealed that processes besides water column respiration were driving high CO2 within the tidal river (salinity < 2) but not in the estuary (salinity > 2). Conservative mixing plots for pCO2 and 222Rn implied that groundwater may be a contributing source of CO2 during most surveys, but not during dry conditions. A multiple linear regression model explained 88% of the annual pCO2 variability, indicating that mixing, metabolism, temperature, and groundwater inputs were key drivers of CO2. Inputs from an upstream wastewater outfall potentially fuel observed seasonal algal blooms, resulting in the lowest daytime CO2 emissions periods. Postbloom surveys had the highest daytime CO2 emissions. The average tidal river CO2 atmospheric flux rate was 379 ± 53 mmol m−2 day−1. The average estuarine CO2 flux was 78 ± 17 mmol m−2 day−1, equating to 28 ± 6 mol m−2 yr−1. Although the tidal river surface area was ~10 times smaller than the estuary, about one third (35%) of the CO2 emissions were derived from the tidal river. Our results suggest that CO2 emissions along the tidal river‐estuary continuum are dynamic over small temporal and spatial scales and that a combination of hydrological and biological processes is a controlling factor of this variability. Plain Language Summary Estuaries are dynamic hotspots for carbon cycling and atmospheric emissions of the greenhouse gas carbon dioxide (CO2). Understanding the drivers and emissions of CO2 is important for global carbon budgets. Here we assess the seasonal drivers of CO2 in a subtropical Australian estuary. Over one‐year, spatial surveys of pCO2 and associated drivers were measured from the estuary mouth to a weir located 25km upstream. Our analysis revealed processes besides water column respiration were driving high CO2 within the tidal river but not in the estuary. Conservative mixing plots implied groundwater may be contributing to the source of CO2 upstream. A modeling exercise indicated the mixing of seawater, metabolism, seasonality and groundwater inputs were important predictors of CO2. Inputs from the upstream wastewater outfall potentially fuel observed seasonal algal blooms, resulting in lowest daytime CO2 emissions whilst post‐bloom surveys had the highest daytime CO2 emissions. The average estuarine CO2 flux was 28 ±6 mol m−2 yr−1, which is in line with recent global estimates. Our results suggest that CO2 emissions along the tidal river‐estuary continuum are dynamic over small temporal and spatial scales and that a combination of hydrological and biological processes are controlling factors of this variability. Key Points Annual spatiotemporal sampling constrained pCO2 dynamics in a hydrologically modified tidal river‐estuary A MLR model with salinity, dissolved oxygen, temperature, and 222Rn could explain 88% of the annual pCO2 variability Multiple lines of evidence suggested that groundwater may be an important driver of surface water CO2
Details
- Title
- Seasonal drivers of carbon dioxide dynamics in a hydrologically modified subtropical tidal river and estuary (Caboolture River, Australia)
- Creators
- Luke C Jeffrey (Corresponding Author) - Southern Cross UniversityIsaac R Santos - Southern Cross UniversityDouglas R Tait - Southern Cross UniversityUriah Makings - Southern Cross UniversityDamien T Maher - Southern Cross University
- Publication Details
- Journal of Geophysical Research : Biogeosciences, Vol.123(6), pp.1827-1849
- Identifiers
- 991012831987702368
- Academic Unit
- National Marine Science Centre; School of Environment, Science and Engineering; Southern Cross GeoScience; Science; Faculty of Science and Engineering
- Language
- English
- Resource Type
- Journal article