DataSheet1_Changes in Organic Matter Deposition Can Impact Benthic Marine Meiofauna in Karst Subterranean Estuaries.xlsx

Subsurface mixing of seawater and terrestrial-borne meteoric waters on carbonate landscapes creates karst subterranean estuaries, an area of the coastal aquifer with poorly understood carbon cycling, ecosystem functioning, and impact on submarine groundwater discharge. Caves in karst platforms facilitate water and material exchange between the marine and terrestrial environments, and their internal sedimentation patterns document long-term environmental change. Sediment records from a flooded coastal cave in Cozumel Island (Mexico) document decreasing terrestrial organic matter (OM) deposition within the karst subterranean estuary over the last ∼1,000 years, with older sediment likely exported out of the cave by intense storm events. While stable carbon isotopic values (δ13Corg ranging from −22.5 to −27.1‰) and C:N ratios (ranging from 9.9 to 18.9) indicate that mangrove and other terrestrial detritus surrounding an inland sinkhole are the primarily sedimentary OM supply, an upcore decrease in bulk OM and enrichment of δ13Corg values are observed. These patterns suggest that a reduction in the local mangrove habitat decreased the terrestrial particulate OM input to the cave over time. The benthic foraminiferal community in basal core sediment have higher proportions of infaunal taxa (i.e., Bolivina) and Ammonia, and assemblages shift to increased miliolids and less infaunal taxa at the core-top sediment. The combined results suggest that a decrease in terrestrial OM through time had a concomitant impact on benthic meiofaunal habitats, potentially by impacting dissolved oxygen availability at the microhabitat scale or resource partitioning by foraminifera. The evidence presented here indicates that landscape and watershed level changes can impact ecosystem functioning within adjacent subterranean estuaries.

碳酸盐岩景观中，海水与陆源大气降水发生地下混合作用，形成喀斯特地下河口（karst subterranean estuaries）——该沿海含水层区域的碳循环过程、生态系统功能及其对海底地下水排泄（submarine groundwater discharge）的影响机制，目前仍有待深入阐明。
喀斯特台地上的洞穴为海洋与陆地环境间的水体及物质交换提供了便利通道，其内部的沉积序列完整记录了长期环境变化信息。
对墨西哥科兹美岛一处淹没沿海洞穴的沉积记录研究显示，近约1000年以来，喀斯特地下河口内的陆源有机质（OM）沉积量呈逐步下降趋势，而较老沉积物可能曾因强烈风暴事件被搬运出洞穴。
尽管有机碳同位素δ¹³Corg值介于-22.5‰至-27.1‰之间、碳氮比介于9.9至18.9之间的分析结果表明，内陆落水洞周边的红树林及其他陆源碎屑是沉积物中有机质的主要来源，但研究同时观测到岩心柱样的总有机质含量向上逐渐降低、δ¹³Corg值逐渐富集的特征。
上述分布模式暗示，当地红树林生境的萎缩随时间推移降低了输入至洞穴的陆源颗粒有机质通量。
基底岩心沉积物中的底栖有孔虫群落以底内类群（infaunal taxa，如卷转虫属*Bolivina*和希望虫属*Ammonia*）占比更高，而岩心表层沉积物中的有孔虫组合则向粟孔虫类（miliolids）占比提升、底内类群占比下降的方向转变。
综合上述研究结果可知，陆源有机质输入随时间减少会对底栖小型动物栖息地产生连带影响，其潜在机制包括改变微生境尺度下的溶解氧可用性，或是通过有孔虫的资源分配作用实现。
本研究提供的证据表明，流域与景观尺度的环境变化可对邻近地下河口的生态系统功能产生显著影响。