| In recent years, the productivity of mariculture has been increasing rapidly in China. Nevertheless, impacts on water quality of adjacent sea exerted by mariculture and pollutant loadings produced by this anthropogenic activity are largely unknown. In this study, the influence of mariculture on the adjacent water bodies was investigated by monitoring the concentration of aquatic pollutants in outlet creek located in Kenli county, Shandong Province, during October (breeding period) and December (fallowing period) in 2014. Pollutant loadings of mariculture were estimated with statistical data, and the ratio of mariculture pollutant loadings among the fluxes of pollutants into the estuary were analyzed. Monte Carlo simulation was performed, and critical factors were identified by sensitivity analysis, for conducting further scenario simulation and providing basics for the sustainable development of mariculture.Monitoring results indicated that the concentration of pollutants were high during both sampling periods. During breeding period, the range (mean) concentrations of dissolved inorganic nitrogen (DIN), total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (CODMn) and total organic carbon (TOC) were 0.32-0.46 (0.40) mg/L,0.80～1.51 (1.17) mg/L,0.04～0.17 (0.09) mg/L,2.03～6.50 (4.11) mg/L and 3.44～8.05 (6.21) mg/L, respectively. During fallowing period, the range (mean) concentration of pollutants were 1.17 ～2.50 (1.83) mg/L,1.50～3.68 (2.93) mg/L,0.04～0.17 (0.07) mg/L,4.20～7.21 (6.21) mg/L and 4.82～7.22 (6.19) mg/L, respectively. Concentrations of DIN, TN, CODMn and TOC were regularly increased during the ebb tide and decreased during the rising tide, but the trends of concentration variation of TP and DIP with tide effect were opposite. Discharge of mariculture wastewater at the ebb tide phase can be responsible for the decrease of dissolved oxygen (DO) and pH value, and induce the increase of nutrients. DIN and CODMn were considered as the most significant polluting indices according to water quality criteria. Besides, eutrophication was aggravated during fallowing period.Based on national surveyed coefficients of pollutants emission of mariculture and statistical data of aquatic products, the national pollutant loadings of TN, TP, COD, copper and zinc of mariculture were 17,414 t,3145 t,55,505 t,53 t and 242 t, respectively, in 2012. A good linear correlation was observed between mariculture pollutant loadings and mariculture output within coastal provinces. Pollutants fluxes from different sources demonstrated that terrigenous input was the major contribution to the pollutant loadings. Maricultural pollutant loadings were relatively mild compared to that from other sources, however not negligible in terms of its impact on the water quality of localized coastal areas. Sensitivity analysis revealed that the maricultural mode was an essential factor influencing the pollutant loadings. With constant mariculture output, scenario simulation showed that by increasing the ratio of pond culture and decreasing net pen cage culture, the pollutant loadings of TN, TP and COD can be reduced by 3.2%,22.6% and 8.8%, respectively. It is essential to select appropriate breeding modes and improve the availability of baits to minimize the mariculture impacts on adjacent aquatic environment. |
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