海藻碎屑补贴对典型岛礁海域大型底栖动物群落结构的影响研究

Resource subsidies function as an important link between habitats. The subtidal habitat between the seaweed bed and open sea, due to lack of self-produced primary production, is the main area receiving macroalgal detritus subsidies. With the construction scale of seaweed bed increasingly expanded, the increased export of macroalgal detritus would be likely to alter the structure of macrobenthos community in the adjacent benthic habitat. The proposed study will take the subtidal waters of Zhangzidao island, a typical offshore island ecosystem in the northern Yellow Sea, as the study area, will sample surface sedimentary organic matter including macroalgal detritus and macrobenthos across a range of water depths during the phases of macroalgae growing and decaying of two consecutive years, will analyze the spatial and temporal dynamics of macrobenthos community using contemporary multivariate statistics, will determine the temporal and spatial distribution characteristics of contribution degrees of macroalgal detritus to the composition of surface sedimentary organic matter, and evaluate the inter-specific differences in competitive use of macroalgal detritus by macroinvertebrate by using stable isotope mixing model. The last component will use ecological stoichiometry to explore how the nutrients differ between detritus-feeding primary consumers and their food sources, how this affects the inter-specific variation of relative biomass, and elucidate the mechanism that macroalgal detritus subsidies drive the shift in the macroinvertebrate community structure. The anticipated results would provide valuable insight into the effects of artificial seaweed beds on the coastal marine environments and allow informed decisions to support marine ranching construction to be made.

资源补贴是链接不同生境的重要纽带。由于缺少自源性初级生产，介于岛礁海藻场和开放外海之间的潮下带底栖生境是海藻碎屑补贴的主要区域。伴随海藻场建设规模的扩大，增加的海藻碎屑输出可能会改变邻近底栖生境中大型底栖动物的群落结构。为此本研究选取典型岛礁生态系统—獐子岛近岸海域作为研究区域，通过在海藻盛衰季节对不同水深梯度内的表层沉积物有机质（海藻碎屑）和大型底栖动物连续两年的采样，运用多变量统计分析阐明大型底栖动物群落结构的时空变化；通过利用稳定同位素混合模型，解析海藻碎屑在表层沉积物有机质中贡献度的时空分布特征，评价海藻碎屑作为食源在种间的利用性竞争关系；进而结合生态化学计量学，着重探讨碎屑食性大型底栖动物通过营养元素的利用调节对种间相对生物量的影响，阐明海藻碎屑补贴对大型底栖动物群落结构的影响。研究结果有助于深入理解海藻场建设对近海生态系统的影响，为科学建设海洋牧场提供基础理论支持。

资源补贴是链接不同生境的重要纽带。介于岛礁海藻场和开放外海之间的潮下带底栖生境是海藻碎屑补贴的主要区域，跨生境输入的海藻碎屑可能会改变邻近底栖生境中大型底栖动物的群落结构和功能。为此，本研究分别于2020年5月（海藻生长季）和8月（海藻衰亡季）对典型岛礁海藻场—北黄海褡裢岛海藻场邻近海域大型底栖动物调查的基础上，采用多变量统计分析阐明海藻盛衰期间大型底栖动物群落结构的季节变化特征，并结合碳氮稳定同位素和生态化学计量学方法，探讨海藻碎屑补贴对大型底栖动物群落结构的影响机制。结果表明：本研究共采集到大型底栖动物 134 种，种类数、丰度、生物量和群落组成在海藻盛衰期间变化明显，造成季节间群落组成差异的主要分歧种为紫蛇尾、尖顶大狐钩虾、叶虾等。大型底栖动物群落的δ13C值在季节间差异显著，且在海藻衰亡的8月大型底栖动物的δ13C值，群落营养多样性水平和营养生态位宽幅更高。稳定同位素混合模型（SIAR）估算结果表明，海藻源对邻近海域表层沉积物有机质（SOM）的平均贡献度在8月明显上升（26.1%->40.3%），而POM的平均贡献度却下降明显（67.70%->54.02%），同时，海藻源对大型底栖动物食源的重要性在8月也明显提高。大型底栖动物对碎屑源的选择性分析表明，须鳃虫、仿刺参等碎屑食性大型底栖动物对SOM中的裙带菜、孔石莼等碎屑具有明显的选择性。生态化学计量分析表明，大型底栖动物、POM和海洋大型植物的C、N、P元素含量和化学计量比值呈现出季节变化，并且大型底栖动物化学计量比特征在种间差别明显，相对于蛇尾类化学计量特征在季节间变化的保守性，多毛类和双壳类的化学计量属性在季节间更为多变的，这反映了大型底栖动物种类间在生源要素利用方面的差异。本研究结果有助于深入理解海藻场建设对近海生态环境的影响，为科学建设海洋牧场提供科学依据。