Spatiotemporal patterns in the basal resources fueling the macrobenthic food web of a temperate coastal embayment subject to a low-turbidity riverine discharge (Gwangyang Bay, Korea) were evaluated using carbon and nitrogen stable isotopes. This study examined trophic links of macrobenthic food web with primary production in diverse wetland habitats along the riverine–estuarine–coastal marine continuum. δ¹³C and δ¹⁵N values of macrobenthic assemblages collected along the salinity gradient of the main channel and their putative sources of organic matter (i.e., riverine particulate organic matter (RPOM), Phragmites australis, microphytobenthos (MPB), phytoplankton, and Zostera marina) were determined. A permutational analysis of variance test showed seasonal uniformity in the isotopic niches of the macrobenthic community within different channel locations. In contrast, isotopic nestedness calculated for the microbenthic community emphasized clearly different trends in its isotopic niches among locations. The δ¹³C values of phytoplankton, suspended and sedimentary organic matter, and macrobenthic community displayed a consistently positive relationship with salinity, characterizing an important contribution of local phytoplankton to the nutrition of macrobenthic community. The isotope mixing model revealed that Phragmites-derived organic matter contributed considerably to the nutrition in the estuarine channel, whereas MPB and Zostera provided trophic subsidies to the deep bay and offshore communities. The nutritional importance of RPOM was minimal at all sites. Overall results suggest that phytoplankton production is a major nutritional contributor to the macrobenthic community in the main channel and that trapping POM originated from neighboring wetlands leads to a longitudinal isotopic niche shift in the macrobenthic community.

中文翻译：

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大型无脊椎动物的同位素变化及其沿河口梯度的有机质来源

使用碳和氮稳定同位素评估了在低浊度河水排放下（韩国光阳湾）温带沿海小海湾基层资源为大型底栖食物网提供燃料的时空格局。这项研究研究了大型底栖食物网与沿河-河口-沿海海洋连续体的不同湿地生境中初级生产的营养联系。δ ¹³ C和δ ^15个沿主信道的盐度梯度收集底栖组合的N个值和它们的有机物质（即，河流颗粒有机物质（RPOM），推定的源芦苇，microphytobenthos（MPB），浮游植物，和大叶码头）确定。方差检验的排列分析表明，在不同渠道位置，大型底栖动物群落的同位素生态位具有季节性均匀性。相比之下，为微底栖动物群落计算出的同位素嵌套明显强调了不同位置之间其同位素生态位的不同趋势。该δ ¹³浮游植物，暂停和沉积有机质和底栖动物群落C值显示随着盐度一贯的正相关关系，本地特性浮游植物对大型底栖动物群落的营养做出了重要贡献。同位素混合模型表明，芦苇来源的有机物对河口通道的营养起了重要作用，而MPB和Zostera向后海湾和近海社区提供营养补贴。在所有地点，RPOM的营养重要性极低。总体结果表明，浮游植物的生产是主要通道中大型底栖动物群落的主要营养成分，而捕集源自邻近湿地的POM会导致大型底栖动物群落的纵向同位素生态位转移。