Elsevier

Atmospheric Environment

Volume 115, August 2015, Pages 269-277
Atmospheric Environment

Fluxes of greenhouse gases at two different aquaculture ponds in the coastal zone of southeastern China

https://doi.org/10.1016/j.atmosenv.2015.05.067Get rights and content

Highlights

  • Aquaculture ponds in the coastal zone are sources of atmospheric CH4 and N2O.

  • Aquaculture pond types have a significant influence on GHG emissions.

  • Aquaculture ponds have higher GHG emissions during the drained period.

Abstract

Shallow water ponds are important contributors to greenhouse gas (GHG) fluxes into the atmosphere. Aquaculture ponds cover an extremely large area in China's entire coastal zone. Knowledge of greenhouse gas fluxes from aquaculture ponds is very limited, but measuring GHG fluxes from aquaculture ponds is fundamental for estimating their impact on global warming. This study investigated the magnitude of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes from two coastal aquaculture ponds during 2011 and 2012 in the Shanyutan wetland of the Min River estuary, southeastern China, and determined the factors that may regulate GHG fluxes from the two ponds. The average fluxes of CO2, CH4 and N2O were 20.78 mgCO2 m−2 h−1, 19.95 mgCH4 m−2 h−1 and 10.74 μgN2O m−2 h−1, respectively, in the shrimp pond. The average fluxes of CO2, CH4 and N2O were −60.46 mgCO2 m−2 h−1, 1.65 mgCH4 m−2 h−1 and 11.8 μgN2O m−2 h−1, respectively, in the mixed shrimp and fish aquaculture pond during the study period. The fluxes of all three gases showed distinct temporal variations. The variations in the GHG fluxes were influenced by interactions with the thermal regime, pH, trophic status and chlorophyll-a content. Significant differences in the CO2 and N2O fluxes between the shrimp pond and the mixed aquaculture pond were observed from September to November, whereas the CH4 fluxes from the two ponds were not significantly different. The difference in the CO2 flux likely was related to the effects of photosynthesis, biological respiration and the mineralization of organic matter, whereas the N2O fluxes were controlled by the interactions between nitrogen substrate availability and pH. Water salinity, trophic status and dissolved oxygen concentration likely affected CH4 emission. Our results suggest that subtropical coastal aquaculture ponds are important contributors to regional CH4 and N2O emissions into the atmosphere, and their contribution to global warming must be considered. Furthermore, we also suggest that aquaculture pond type should be considered when evaluating regional GHG budgets in coastal aquaculture ponds.

Introduction

Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are key radiatively active greenhouse gases (GHGs) in the atmosphere that have been recognized as contributing to global warming by 60, 25 and 5%, respectively (Mosier, 1998). The current global atmospheric concentrations of the three GHGs are approximately 390.5 ppm, 1803 ppb and 324.2 ppb in 2011, and these concentrations have increased steadily over the past century by approximately 0.50, 1.10 and 0.26%, respectively, per year (IPCC, 2013). Increasing atmospheric concentrations of GHGs have stimulated research to determine their production and emissions in different ecosystems (Selvam et al., 2014).

Global freshwater environments based on estimates from recent research could be emitting 1.2–2.1 Pg of C (CO2 equiv.) year−1 as CO2 (Aufdenkampe et al., 2011) and 0.65 Pg of C (CO2 equiv.) year−1 in the form of CH4 (Bastviken et al., 2011), i.e., more than 2 Pg C (CO2 equiv.) year−1 in total. It has been suggested that CO2 and CH4 emissions from freshwater environments counterbalance a large portion of the global land carbon sink of 2.6 Pg of C year−1 (Selvam et al., 2014). Freshwater aquatic ecosystems play an important role in global carbon biogeochemical cycles and are considered significant emission sources of GHGs (Natchimuthu et al., 2014). Therefore, GHG emissions from aquatic ecosystems have been studied widely in recent years because of their contribution to global warming (Selvam et al., 2014). At present, research on GHG emissions from aquatic ecosystems is focused on inland freshwaters, including natural lakes (Huttunen et al., 2003, Xing et al., 2005), rivers (Aufdenkampe et al., 2011, Clough et al., 2011), ditches (Schrier-Uijl et al., 2011) and reservoirs (Soumis et al., 2004, Diem et al., 2012). These reports suggested that the magnitude and pattern of spatiotemporal variations in GHG emission are influenced by weather, water thermal regime, nutrient content, hydrodynamic condition and biological activity (Zhu et al., 2010, Palma-Silva et al., 2013, Natchimuthu et al., 2014). However, very few studies have presented GHG fluxes from aquatic environments in coastal zones, especially fluxes caused by anthropogenic disturbances on aquatic environments, including aquaculture ponds.

Currently, large coastal wetlands areas around the world have been converted to aquaculture ponds because of economic benefits and the expansion of human populations (Cao et al., 2011). In contrast to natural wetlands, aquaculture ponds receive large amounts of nutrient inputs from aquaculture activities (Serrano-Grijalva et al., 2011). Excess availability of nutrients facilitates aquaculture pond primary production but can also have significant effects on microbial processes, which can directly or indirectly affect carbon and nitrogen biogeochemical processes. However, information on global GHG emissions from coastal aquaculture ponds is very limited, and the potential effects of exogenous nutrient loading on producing and emitting gaseous carbon (CH4 and CO2) and nitrogen (N2O) into the atmosphere have remained poorly documented until now. Additionally, microbial processes affecting GHG production are regulated by many parameters, including temperature, salinity, pH, dissolved oxygen and substrate availability (Xing et al., 2005, Schrier-Uijl et al., 2011). Evaluating the influence of different environmental factors on GHG emissions from coastal aquaculture ponds is important.

Aquaculture ponds cover a large and significant area in China's entire coastal zone; the area of aquaculture ponds was 1260 km2 (Zuo et al., 2013). Therefore, it is critical to quantify GHG fluxes and controlling factors in aquaculture ponds to accurately evaluate coastal ecosystem GHG budgets and scientifically manage coastal wetlands. We investigated GHG fluxes and environmental variables in this paper for two coastal aquaculture ponds in the Min River estuary. The aims of this study are to (1) quantify and compare GHG fluxes at the water-atmosphere interfaces of a shrimp pond and mixed culture pond and (2) investigate the temporal variations in GHG fluxes and influencing factors.

Section snippets

Study area and sampling sites

The study region is located on the Shanyutan wetland (26°00′36″–26°03′42″ N, 119°34′12″–119°40′40″ E) in the Min River estuary, southeastern China; this wetland covers 3120 ha. The climate is typically subtropical monsoon with a mean annual temperature of 19.6 °C and a mean annual precipitation of 1350 mm (Zheng et al., 2006). Within the Shanyutan wetland there is a tidal marsh vegetation landscape dominated by native species Phragmites australis and Cyperus malaccensis and the invasive plant

Environmental variables and trophic conditions

The daily air temperature during the sampling period ranged from 21.4 to 33.4 °C in the shrimp pond and from 18.8 to 32.0 °C in the mixed culture pond (Fig. 2a). The water temperature at a depth of 10 cm ranged from 20.3 to 33.3 °C and from 17.4 to 31.3 °C in the two ponds (Fig. 2b). Daily atmospheric pressure varied from 999.2 to 1016.4 Pa and from 1007.5 to 1018.7 Pa in the shrimp pond and mixed culture pond, respectively (Fig. 2c).

The water in both ponds was slightly alkaline, with a mean pH

CO2 flux and environmental factors

The dominate factor controlling CO2 production and emission in different aquatic environments is different. Tank et al. (2009) reported that the algal activity and the mineralization of organic matter might play a more important role in CO2 flux dynamics in the Mackenzie Delta lakes within the Arctic Landscape. Zhu et al. (2010) found that the respiration and the mineralization of organic matter in sediments were important factors influencing CO2 emission in Lakes Tuanjie and Mochou in the

Conclusion

The results in this study indicate that aquaculture ponds in the coastal zone are strong CH4 emitters and weak N2O emitters during the culture period and are a source of GHG emissions during the drained period. GHG fluxes are regulated by pH, thermal regime, trophic status and metabolic activity of algae in aquaculture ponds during the culture period. GHG emissions from the aquaculture ponds of coastal zones in China play a more important role in global GHG budgets because of their higher CH4

Acknowledgements

This research was supported financially by the National Science Foundation of China (No.41071148, 41371127), the Program for Innovative Research Team of Fujian Normal University (IRTL1205) and the Key Sciences and Technology Project of the Fujian Province (2014R1101). We would like to thank Hui-Xu and Yong-Yue Ma of the School of Geographical Sciences, Fujian Normal University for their field assistance and Liu-Ming Yang and Yuan-Zhen Peng of the School of Geographical Sciences, Fujian Normal

References (41)

  • J.S. Yang et al.

    Effect of water table level on CO2, CH4 and N2O emissions in a freshwater marsh of Northeast China

    Soil Biol. Biochem.

    (2013)
  • R.B. Zhu et al.

    Carbon dioxide and methane fluxes in the littoral zones of two lakes, east Antarctica

    Atmos. Environ.

    (2010)
  • S. An et al.

    Enhancement of coupled nitrification-denitrification by benthic photosynthesis in shallow estuarine sediments

    Limnol. Oceanogr.

    (2001)
  • I. Aselmann et al.

    Global distribution of natural freshwater wetlands and rice paddies, their net primary productivity, seasonality and possible methane emissions

    J. Atmos. Chem.

    (1989)
  • A. Aufdenkampe et al.

    Riverine coupling of biogeochemical cycles between land, oceans, and atmosphere

    Front. Ecol. Environ.

    (2011)
  • D. Bastviken et al.

    Freshwater methane emissions offset the continental carbon sink

    Science

    (2011)
  • I. Bergier et al.

    Carbon dioxide and methane fluxes in the littoral zone of a tropical savanna reservoir (Corumba, Brazil)

    Oecologia Aust.

    (2011)
  • L. Cao et al.

    Life cycle assessment of Chinese shrimp farming systems targeted for export and domestic sales

    Environ. Sci. Technol.

    (2011)
  • T.J. Clough et al.

    Nitrous oxide dynamics in a braided river system, New Zealand

    J. Environ. Qual.

    (2011)
  • T. Diem et al.

    Greenhouse gas emissions (CO2, CH4, and N2O) from several perialpine and alpine hydropower reservoirs by diffusion and loss in turbines

    Aquat. Sci.

    (2012)
  • Cited by (0)

    View full text