BACKGROUND Sponges are important suspension-feeding members of reef communities, with the collective capacity to overturn the entire water column on shallow Caribbean reefs every day. The sponge-loop hypothesis suggests that sponges take up dissolved organic carbon (DOC) and, via assimilation and shedding of cells, return carbon to the reef ecosystem as particulate organic carbon (POC). Sponges host complex microbial communities within their tissues that may play a role in carbon and nutrient cycling within the sponge holobiont. To investigate this relationship, we paired microbial community characterization (16S rRNA analysis, Illumina Mi-Seq platform) with carbon (DOC, POC) and nutrient (PO4, NOx, NH4) flux data (specific filtration rate) for 10 common Caribbean sponge species at two distant sites (Florida Keys vs. Belize, ~ 1203 km apart). RESULTS Distance-based linear modeling revealed weak relationships overall between symbiont structure and carbon and nutrient flux, suggesting that the observed differences in POC, DOC, PO4, and NOx flux among sponges are not caused by variations in the composition of symbiont communities. In contrast, significant correlations between symbiont structure and NH4 flux occurred consistently across the dataset. Further, several individual symbiont taxa (OTUs) exhibited relative abundances that correlated with NH4 flux, including one OTU affiliated with the ammonia-oxidizing genus Cenarchaeum. CONCLUSIONS Combined, these results indicate that microbiome structure is uncoupled from sponge carbon cycling and does not explain variation in DOC uptake among Caribbean coral reef sponges. Accordingly, differential DOC assimilation by sponge cells or stable microbiome components may ultimately drive carbon flux in the sponge holobiont.

中文翻译：

---

测试微生物组组成与加勒比珊瑚礁海绵中碳和养分通量之间的关系。

背景技术海绵是珊瑚礁群落重要的悬浮物喂养成员，具有每天翻转整个加勒比浅礁石上整个水柱的集体能力。海绵环假说表明，海绵吸收了溶解的有机碳（DOC），并通过同化和脱落细胞，将碳作为颗粒有机碳（POC）返回到珊瑚礁生态系统。海绵在其组织内拥有复杂的微生物群落，这些群落可能在海绵状全生命周期内的碳和养分循环中发挥作用。为了研究这种关系，我们将10种常见的加勒比海海绵物种的微生物群落特征（16S rRNA分析，Illumina Mi-Seq平台）与碳（DOC，POC）和养分（PO4，NOx，NH4）通量数据（特定过滤速率）配对在两个遥远的地点（佛罗里达群岛与伯利兹，相距约1203公里）。结果基于距离的线性模型揭示了共生体结构与碳和养分通量之间的总体关系较弱，这表明所观察到的海绵中POC，DOC，PO4和NOx通量的差异并非由共生体群落组成的变化引起。相反，在整个数据集中，共生体结构与NH4通量之间存在显着的相关性。此外，几个单独的共生生物类群（OTU）表现出与NH4通量相关的相对丰度，包括一个与氨氧化菌Cenarchaeum相关的OTU。结论综上所述，这些结果表明微生物组结构与海绵碳循环无关，并且不能解释加勒比珊瑚礁海绵中DOC吸收的变化。因此，