Carbon dioxide fluxes from two typical mariculture polyculture systems in coastal China

Abstract

During the farming season of 2013 and 2014, carbon dioxide (CO2) fluxes at the water-air interface were determined from two typical seawater polyculture systems. The mean CO2 fluxes of 2013 and 2014 were − 0.316 ± 0.0674 μmol m−2 s−1 and -0.173 ± 0.242 μmol m−2 s−1 in the bi-species polyculture system of swimming crab (Portunus trituberculatus) with kuruma shrimp (Marsupenaeus japonicus) (PM) and 0.249 ± 0.251 μmol m−2 s−1 and 0.426 ± 0.151 μmol m−2 s−1 in the tri-species polyculture system of swimming crab with shrimp and short-necked clam (Ruditapes philippinarum) (PMR) (Negative flux values refer to CO2 uptake and positive values refer to CO2 emission). During the farming season, the CO2 budgets in PM and PMR were − 113.1 g CO2 m−2 and 154.0 g CO2 m−2, respectively. Water pH seemed like a stable indicator for CO2 flux and Chlorophyll a concentration was a key factor regulating the CO2 flux. Subsequent decreasing in water pH and Chl a concentration was supposed to be the main contributor changing the carbon source/sink function from a CO2 sink of PM to a CO2 source of PMR. Under the condition of current study, pH of 8.26 could be considered to be the critical value between influxes and effluxes in seawater crab-shrimp and crab-shrimp-clam polyculture systems.