Benthic macrofauna modifies carbon and nutrient retention and recycling processes in coastal habitats. However, the contribution of benthic consumers to carbon and nutrient storage and recycling shows variation over spatial scales, as the benthic community composition changes in response to differences in environmental conditions. By sampling both shallow sandy and deep muddy sediments across a land-to-sea gradient in the northern Baltic Sea, we explored if benthic community composition, stoichiometry and process rates change in response to alterations in environmental conditions and food sources. Our results show that benthic faunal biomass, C, N, and P stocks, respiration rate and secondary production increase across the land-to-sea gradient in response to higher resource quality towards the open sea. The seston δ¹³C indicated terrestrial runoff and δ¹⁵N sewage input at the innermost study sites, whereas more fresh marine organic matter towards the open sea boosted benthic faunal carbon storage, respiration rate, and secondary production, that is, the generation of consumer biomass, which are essential processes for carbon turnover in this coastal ecosystem. Also, biological factors such as increasing species richness and decreasing biomass dominance of the clam Macoma balthica were significant in predicting benthic faunal C, N, and P stocks and process rates, especially at sandy sites. Interestingly, despite the variation in food sources, the benthic faunal C:N:P ratios remained stable across the gradient. Our results prove that human activities in the coastal area can influence the important links between biodiversity, structure, and process rates of benthic communities by modifying the balance of available resources, therefore hampering the functioning of coastal ecosystems.

大型底栖动物改变了沿海栖息地的碳和养分保留和回收过程。然而，底栖消费者对碳和养分储存和回收的贡献在空间尺度上表现出变化，因为底栖群落组成会随着环境条件的差异而变化。通过对波罗的海北部陆海梯度上的浅层沙质和深层泥质沉积物进行采样，我们探索了底栖群落组成、化学计量和过程速率是否会随着环境条件和食物来源的变化而变化。我们的结果表明，随着公海资源质量的提高，底栖动物生物量、碳、氮和磷库、呼吸速率和次生生产在陆地到海洋梯度上均有所增加。δ ¹³ C 表明陆地径流和最内部研究地点的δ ¹⁵ N 污水输入，而更多的新鲜海洋有机物流向公海，促进了底栖动物的碳储存、呼吸速率和二次生产，即消费的产生。生物质，这是沿海生态系统碳周转的重要过程。此外，生物因素（例如蛤Macoma balthica的物种丰富度增加和生物量优势下降）对于预测底栖动物碳、氮和磷储量和加工速率具有重要意义，特别是在沙地。有趣的是，尽管食物来源存在变化，底栖动物的 C:N:P 比率在整个梯度上保持稳定。我们的研究结果证明，沿海地区的人类活动可以通过改变可用资源的平衡来影响底栖群落的生物多样性、结构和过程速率之间的重要联系，从而阻碍沿海生态系统的功能。