微塑料胁迫对近江牡蛎免疫及抗菌力的影响

Effects of microplastics stress on the immunity and antibacterial activity of Crassostrea ariakensis

为探究微塑料对近江牡蛎(Crassostrea ariakensis)免疫及抗菌力的影响,本研究将不同浓度(0.05 mg/L、0.5 mg/L、5 mg/L)的聚苯乙烯微塑料—菌悬液注入牡蛎壳腔内,研究牡蛎在胁迫24 h和72 h后鳃组织中6种免疫指标的活力,同时记录死亡率。结果显示,微塑料胁迫24 h后,丙二醛(malondialdehyde,MDA)含量和超氧化物歧化酶(superoxide dismutase,SOD)活力随暴露浓度的升高而升高,但一氧化氮合成酶(nitric oxide synthase,NOS)和乙酰胆碱酯酶(acetylcholinesterase,AchE)随暴露浓度升高被显著抑制,碱性磷酸酶(alkaline phosphatase,AKP)活力仅在0.5 mg/L处理下显著上升,过氧化氢酶(catalase,CAT)的活力呈现先上升再下降后上升的趋势。微塑料胁迫72 h后,CAT、AKP、A-chE和SOD的活力变化趋势与24 h的变化趋势大致相同,但活性显著减弱,牡蛎的累计死亡率与对照组相比显著上升。以上结果表明,随着微塑料浓度的增加和暴露时间的延长,牡蛎的抗菌能力和免疫能力均呈下降趋势。

Oyster Crassostrea ariakensis is one of the typical bivalve molluscs and is an important economic species in China. It mainly grows in the estuary in China and occupies an important position in the bivalve industry in Guangdong. In this study, C. ariakensis was selected as the experimental organism to explore the impact of the polystyrene microplastics on the immunity of C. ariakensis. In order to study the effects of microplastics immunity and antibacterial activity of oyster, the oysters(average shell length: 6.6 cm) were injected with different concentrations of polystyrene microplastics, respectively(0.05 mg/L, 0.5 mg/L, 5 mg/L,with sterilized saline water as diluent) by intra-shell injection(without damage to the soft tissue of oyster). The gills were sampled after being treated with microplastics for 24 h and 72 h, respectively, activities of six immune related indexes, including alkaline phosphatase(AKP), superoxide dismutase(SOD), malondialdehyde(MDA), catalase(CAT), nitric oxide synthase(NOS), acetylcholinesterase(A-chE) and the mortality rates were recorded. The results showed that the activities of SOD and A-chE in the gill of oysters were significantly affected by microplastic concentration after 24 h(P<0.05). The activities of AKP increased first and then decreased, while SOD and MDA showed an upward trend, A-chE and NOS showed a downward trend. After 72 h of microplastic treatment, the enzyme activity was significantly lower than those of 24 h(P<0.05). With the increase of microplastic concentration, the trend of changes in enzyme activity is roughly consistent with 24 h trend. When the concentration of microplastics was above 0.5 mg/L, the activity of NOS was lower than that of the control group, and the cumulative mortality of oysters was significantly higher than that of the control group(P<0.05). The above results showed that with the increase of microplastic concentration, the oxidative stress of oysters was more intense. With the extension of exposure time, the antibacterial ability and immune ability of oysters decreased. It is expected to provide reference data for the analysis and evaluation of the potential risks of microplastics to the filter-feeding bivalves.