Collaborative Research: Macrofaunal community effects on benthic exchange fluxes

海底在浅水生态系统的元素循环中起着关键作用。虽然对沿海底栖生物的研究相对较好，但底栖动物在改变营养循环等关键生态系统服务方面的数量作用仍然受到很大限制。这主要是由于难以将在地块（毫米-米）尺度上观察到的生物地球化学动态扩展到沿海生态系统的更大框架。在这个合作项目中，格鲁吉亚大学和马里兰州大学的研究人员？美国切萨皮克生物实验室将在受控条件下对底栖动物活动及其生态相互作用的小尺度动态进行量化，并将这些数据纳入一种新的沉积物地球化学建模方法。具体而言，他们将进行一系列实验研究，以1）确定在复杂的三维域中洞穴的空间排列在多大程度上改变了沉积物生物地球化学，2）测量物种相互作用对沉积物生物地球化学的影响和反馈，以及3）使用这些研究结果为本质上异质的沿海海底取样提供指导。 实验室实验将使用沉积物微宇宙与人工洞穴和真实的生物？在不同的实验中，发现了无处不在的冠状沙蛛和杂色沙蚕。将测量沉积物和上覆水之间几种成岩和生态上重要溶质的通量。洞穴模拟实验将提供详细的经验资料，洞穴灌溉和空间定位对沉积物-海水交换的影响。这一信息将被用来参数化的三维反应传输模型。包含不同组合的两个macrofaunal物种分布在均匀和集群的空间安排将被用来确定物种的相互作用对洞穴的几何形状和灌溉，溶质通量的后果。实验数据将阐明底栖动物对空间邻近性的反应以及物种之间和物种内部的相互作用。将利用观测数据与模型模拟的比较来评估大型底栖动物相互作用对沉积物生态地球化学的影响。最后，将针对大型底栖动物密度和空间排列及其相互作用不同的情景进行反应性迁移模型模拟。将通过将海底划分为若干小块来估算沉积物-水界面的总通量，从而可获得模型通量估算值。这一方法将用于评价各种可能的取样策略，并确定有限数量的通量测量值在多大程度上能够近似底栖动物对沿海生物地球化学循环的贡献。就更广泛的影响而言，这项研究预计将提供一个框架，用于将沿海沉积物中的单个通量测量值扩展到更大规模的质量通量。这些发现将拓宽我们对沿海海洋营养动态的理解，并通过为通量数据的解释和测量活动的设计提供背景，使一般实验界受益。一名研究生将接受实验和数值方法方面的培训。此外，为CBL游客中心制作的关于沉积物地球化学和底栖动物的宣传材料和展览，每年将使大约3 500名游客接触到海洋环境中鲜为人知的方面。

The seafloor plays a critical role in the elemental cycling within shallow water ecosystems. Although the coastal benthos has been relatively well studied, the quantitative role of infauna in modifying critical ecosystem services such as nutrient cycling remains still poorly constrained. This stems largely from difficulties in scaling biogeochemical dynamics observed at the plot (mm - m) scale to the larger framework of coastal ecosystems. In this collaborative project, researchers at the University of Georgia and the University of Maryland?s Chesapeake Biological Laboratory will quantify small-scale dynamics of infaunal activities and their ecological interactions under controlled conditions and incorporate these data into a novel modeling approach of sediment biogeochemistry. Specifically, they will carry out a series of experimental studies to 1) determine to what extent spatial arrangement of burrows in a complex 3-dimensional domain alters sediment biogeochemistry, 2) measure species-interaction effects and feedbacks on sediment biogeochemistry, and 3) use these findings to provide guidance on sampling the intrinsically heterogeneous coastal seafloor. Laboratory experiments will be developed using sediment microcosms with artificial burrows and real organisms ? the ubiquitous Arenicola cristata and Nereis diversicolor - in separate experiments. Fluxes between the sediment and the overlying water of several diagenetically and ecologically important solutes will be measured. Burrow mimic experiments will provide detailed empirical information on burrow irrigation and spatial orientation effects on sediment-seawater exchange. This information will be used to parameterize a three-dimensional reactive transport model. Microcosms containing different combinations of the two macrofaunal species distributed in even and clustered spatial arrangements will be used to determine species interaction effects on burrow geometry and irrigation, and consequences for solute fluxes. The experimental data will elucidate the response of infauna to spatial proximity as well as the interaction across and within species. Comparison of observational data to model simulations will be used to assess the impact of macrofaunal interactions on sediment biogeochemistry. Finally, reactive transport model simulations will be performed for scenarios differing in densities and spatial arrangement of macrofauna, as well as their interactions. Aggregate fluxes across the sediment water interface will be estimated by dividing the seafloor up into tiles for which model flux estimates can be obtained. This approach will be used to evaluate various possible sampling strategies, and determine how well a limited number of flux measurements can approximate the contribution of benthic infauna to coastal biogeochemical cycles. In terms of broader impacts, this study is expected to provide a framework for scaling individual flux measurements taken in coastal sediments to larger scale mass fluxes. The findings will broaden our understanding of nutrient dynamics in the coastal ocean and benefit the general experimental community by providing context for the interpretation of flux data and design of measurement campaigns. One graduate student will be trained in experimental and numerical methodology. In addition, development of outreach materials and exhibits about sediment biogeochemistry and benthic infauna for the CBL visitor center will expose roughly 3500 visitors per year to lesser known aspects of the marine environment.