Mangrove forests are productive habitats and major potential exporters of organic matter and nutrients to adjacent habitats. Here we examine the extent to which mangrove carbon is transferred to adjacent intertidal food webs in the second largest mangrove-covered area in Africa, in Guinea-Bissau. Applying stable isotope analysis and mixing models, we made comparisons at two spatial scales: (1) a large scale, comparing intertidal flats with (mangrove sites) and without (control sites) adjacent mangrove forests regarding the carbon isotopic signature of macrozoobenthos and sediment organic matter (SOM), and the relative importance of potential primary food sources in sustaining macrozoobenthos, and (2) a fine scale, performing stable carbon isotope measurements along 200 m transects from the coastline out to open intertidal flats, to trace mangrove carbon in macrozoobenthos and in the SOM. We found no evidence that mangrove carbon sustains intertidal food webs, despite SOM being significantly more depleted in ¹³C in mangrove sites. Mangrove leaves had the lowest relative contribution to the diet of macrozoobenthos, while macroalgae, benthic microalgae and POM showed variable but overall relevant contributions. Yet, at a smaller scale, mangrove carbon was detectable in SOM and in most macrozoobenthos, being strongest within 50 m of the mangrove edge and quickly fading with increasing distance. Our results suggest that there is only a marginal input of mangrove carbon into the food webs of unvegetated intertidal flats. Still, this leaves open the possibility of mangrove forests acting as sources of dissolved inorganic carbon and processed nitrogen, which can be assimilated by the algae and subsequently fuel adjacent food webs.

红树林是生产性栖息地，是潜在的有机物质和养分向邻近生境的主要出口者。在这里，我们研究了几内亚比绍非洲第二大红树林覆盖区域中红树林碳转移到相邻潮间带食物网的程度。应用稳定的同位素分析和混合模型，我们在两个空间尺度上进行了比较：（1）大尺度，比较了具有（红树林地带）和没有（对照地）相邻红树林的潮间带有关大型带状带和沉积有机物的碳同位素特征物质（SOM），以及潜在主要食物来源在维持大型动物中的相对重要性，以及（2）规模小，在从海岸线到开阔的潮间带的200 m横断面进行稳定的碳同位素测量，在大型动物和SOM中追踪红树林碳。我们没有发现证据表明红树林的碳能维持潮间带食物网，尽管SOM的消耗大大增加了。¹³下，在红树林的网站。红树林叶片对大型动物的饮食的相对贡献最低，而大型藻类，底栖微藻类和POM表现出可变但总体相关的贡献。但是，在较小的规模上，在SOM和大多数大型动物中可检测到红树林碳，在红树林边缘50 m以内最强，并随着距离的增加而迅速褪色。我们的结果表明，无植被的潮间带的食物网中只有少量的红树林碳输入。尽管如此，这仍留下了红树林作为溶解的无机碳和加工过的氮的来源的可能性，它们可以被藻类吸收并随后为邻近的食物网提供燃料。