Carbon budgets of two typical polyculture pond systems in coastal China and their potential roles in the global carbon cycle

D Zhang,Y Chen,S Dong,J Feng,Rp He,K Zhang,X Tian

doi:10.3354/aei00349

Abstract

The role of aquaculture systems in the global carbon cycle is poorly understood to date. We investigated the carbon budgets in 2 polyculture systems (PM: swimming crab Portunus trituberculatus with kuruma shrimp Marsupenaeus japonicus; and PMR: crab, shrimp and short-necked clam Ruditapes philippinarum) during the farming season (125 d in total). The main carbon input occurred via water (PM: 55.06%; PMR: 62.50%), followed by that via feed. PM absorbed 21.55 g C m-2 across the air-water interface, accounting for 13.27% of the total input. The carbon output via water was the main output in both PM (89.17%) and PMR (46.43%). PMR emitted 53.00 g C m-2 into the atmosphere during the farming season, accounting for 32.53% of the total output. The carbon output by harvested animals in PMR accounted for 19.48% of the total output, which was much higher than that in PM (5.71%). Carbon accumulation in the sediment was significantly higher in PM than in PMR (p < 0.05), but the value of both represented a small portion of the total output. Clam farming in the polyculture system profoundly altered the carbon budgets by changing the CO2 flux direction, reducing carbon accumulation in water and sediments and increasing the carbon output by harvested animals. In terms of the global warming potential, which was calculated from the results of CO2 and CH4 fluxes across the air-water interface, PM had the potential for mitigating the greenhouse effect on the 20 yr horizon, whereas PMR exacerbated global warming. Our results suggest that PM acted as a net carbon sink in the global carbon cycle, while PMR acted as a carbon source.

Highlights

Carbon dioxide (CO2) and methane (CH4) are the 2 main greenhouse gases contributing to global warming
41.86% in polyculture systems (PM) and PMR, respectively, which was followed by feeds and the water column
Organic carbon tends to accumulate in aquaculture wastewaters due to feed residue, the excretion and egestion of cultured animals, etc. during the farming process

Summary

Introduction

Carbon dioxide (CO2) and methane (CH4) are the 2 main greenhouse gases contributing to global warming. Aquatic ecosystems are important parts of the global carbon cycle. Aquacult Environ Interact 12: 105–115, 2020 most important player in the global carbon cycle. The annual CH4 emission by oceans was estimated to be 10.9−17.8 Tg (Bange et al 1994, Ortiz-Llorente & Alvarez-Cobelas 2012). Global inland water emits an estimated 2.1 Pg C yr−1 by CO2 emission (Raymond et al 2013) and 0.08 Pg C yr−1 by CH4 emission (Bastviken et al 2011). Aquatic ecosystems can sequester carbon by burial in the sediment, affecting the global carbon cycle. According to an estimation by MullerKarger et al (2005), at least 0.06 Pg C yr−1 may be buried in sediments in coastal areas. Inland waters could bury 0.23 Pg C yr−1, mainly in lakes and reservoirs (Cole et al 2007)

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