互花米草入侵对黄河三角洲秋季底栖食物网的影响

为了保滩护岸,互花米草于1990年被引种至黄河三角洲,随后迅速蔓延,给滨海湿地生态系统带来了严重威胁。为了明晰互花米草入侵对黄河三角洲湿地底栖食物网结构的影响,本研究基于稳定同位素技术,于2020年11月对互花米草入侵区域大型底栖动物的潜在食源、营养级和食物网结构进行了采样分析。结果表明: 调查区域潜在食源δ¹³C平均值的变化规律为沉积物(SOM)>互花米草>底栖微藻>悬浮颗粒物(POM)>盐地碱蓬,潜在食源δ¹⁵N值的变化范围为1.24‰～9.03‰,且不同食源间的δ¹⁵N值存在差异。调查区域大型底栖动物的营养级范围为1.73～4.19,其中双壳类的营养级最低;互花米草及其腐败后的碎屑是大型底栖动物的重要食源之一,但对大型底栖动物的营养级结构没有显著影响。互花米草入侵通过上行效应改变了底栖生物的食源组成,进而可能影响黄河三角洲湿地食物网的结构。

Impacts of Spartina alterniflora invasion on the benthic food web in the Yellow River Delta during autumn

Spartina alterniflora was introduced into the Yellow River Delta (YRD) in 1990 with the purpose of shore protection and siltation accretion. However, it spread rapidly and became a severe threat to the local coastal wetland ecosystem. To assess the impacts of S. alterniflora invasion on the benthic food web, we sampled the potential food sources of macrobenthos in November 2020, analyzed the trophic level and the benthic food web structure based on stable isotope technique. Results showed that the average δ¹³C values of macrobenthic food sources followed an order: sediment organic matter (SOM) > S. alterniflora > benthic microalgae > particulate organic matter (POM) > Suaeda salsa. The average δ¹⁵N values significantly differed among food sources, ranging from 1.24‰ to 9.03‰. The trophic levels of different macrobenthos ranged from 1.73 to 4.19, of which the bivalve species was the lowest one. S. alterniflora and the decayed debris were the most important food sources for macrobenthos, but without any impact on the trophic level structure of macro-benthos. In conclusion, Spartina alterniflora invasion distinctly changed the composition of food sources of macrobenthos through a “bottom-up” effect, which would probably impact the local food web structure in the YRD wetland.