Exchange of matter and energy between ecosystems has been an important topic in ecology. In this work, we estimated the relative assimilation and seasonality of autochthonous versus allochthonous organic matter by macrofauna and fishes of a subtropical sandy beach. Sampling of consumers and autotrophic food sources (particulate organic matter in suspension-POM and in sediment-SOM) were obtained seasonally at the sandy beach for carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope analysis. The range in isotopic values of POM was nearly two-fold higher in winter than in other seasons, which coincided with similar decrease in δ¹³C values of several consumers. Such decreasing patterns in δ¹³C were associated with high rainfall and freshwater discharge during winter, which exported ¹³C-depleted continental POM to the sandy beach. The continental allochthonous matter assimilated by marine organisms originated from the drainage of wetlands by innumerous coastal streams spread along the coast and by a larger estuarine system. Bayesian isotope mixing models revealed a slightly higher average assimilation of organic matter of the coastal streams (24%) than the estuary (18%). The assimilation of allochthonous matter was higher in filter feeders bivalves and detritivore fish and lower in carnivorous guilds (e.g. zoobenthivores, zooplanktivores, carnivorous and scavengers).

生态系统之间物质和能量的交换一直是生态学中的重要课题。在这项工作中，我们估计了亚热带沙滩的大型动物和鱼类相对于同质有机物质和异源有机物质的相对同化和季节性。消费者和自养的食物来源（在悬浮液中-POM和沉积物-SOM粒状有机物）的抽样检验季节性获得在沙滩为碳（δ ¹³ C）和氮（δ ¹⁵ N）稳定同位素分析。在POM的同位素值的范围内几乎是在冬季比其他季节，它与类似的减少同时发生在δ高两倍^13个几个消费者的C值。在δ这样减小图案¹³碳与冬季的高降雨和淡水排放有关，将¹³种贫C的大陆POM出口到沙滩。海洋生物吸收的大陆异源物质来自湿地的排水，这是由于沿海岸散布的无数沿海水流和较大的河口系统造成的。贝叶斯同位素混合模型显示，沿海河流有机物的平均同化率（24％）比河口（18％）略高。滤食性双壳类动物和有害鱼类的同化物质同化率较高，而食肉行会（例如，食肉动物，食动动物，食肉动物和清道夫）的同化物质则较低。