LTER - Georgia Land/Ocean Margin Ecosystem

一个长期生态研究地点将建立在乔治亚州中部海岸萨佩洛岛附近。这是一个堰洲岛和沼泽的综合体，阿尔塔马哈河是美国东海岸最大和最不发达的河流之一，是淡水的主要来源。将调查当地和遥远高地地区之间的联系，这些联系是由水——地表水和地下水——输送到沿海地区所介导的。由河流流量（主要是盐度，因为我们可以在高频率测量）驱动的环境因素的变化与生态系统过程和结构之间的关系将被检查。这将通过比较从阿尔塔马哈河中分离出来的河口/沼泽复合体来完成，这些河口/沼泽复合体会使河流信号潮湿和减弱。这种空间梯度类似于流域发展所预期的河流影响的时间趋势。将执行一个记录物理和生物变量的监测系统。这些变量的时间趋势和空间分布及其方差结构将用于解决控制分布、营养结构、多样性和生物地球化学等问题。将修改现有的基于地理信息系统的水文模型，以纳入随着流域的发展而可能出现的土地利用模式变化所导致的河水变化。该模型将与生态系统模型联系起来，并将作为一种启发式和管理工具。沿海发展的另一个后果是，随着河流流量的减少，地下水流量增加并变得有营养。将比较相对原始的（萨佩洛岛）地表含水层地下水排放的影响与更城市化的（大陆）地点的影响，以评估淡水与营养物质对受地下水影响的沼泽的生产力、结构和生物量周转率的相对重要性。将调查海洋过程（潮汐、风暴潮）对浅层淡水/盐界面混合的影响。另外的物理研究将把盐沼-潮溪通道复合体的形态与潮流分布和交换联系起来。这些发现将被纳入一个物理模型，该模型将与现有的生态系统模型相结合。这个陆地/海洋边缘生态系统位于两个生态系统之间的界面，其中明显不同的分解者群体控制着有机物的降解。真菌分解者在陆地生态系统中占主导地位，而细菌分解者在海洋生态系统中占主导地位。这两个群体在盐沼为主的生态系统中都很重要。具体的研究将在单个细胞和菌丝的水平上检查细菌和真菌在分解枯死的米草属植物和其他沼泽植物的群落中的关系，并检查这种关系是如何或是否沿着盐度梯度变化的。

A Long Term Ecological Research site will be established on the central Georgia coast in the vicinity of Sapelo Island. This is a barrier island and marsh complex with the Altamaha River, one of the largest and least developed rivers on the east coast of the US, as the primary source of fresh water. The linkages between local and distant upland areas mediated by water - surface water and ground water - delivery to the coastal zone will be investigated. The relationship between variability in environmental factors driven by river flow, primarily salinity because we can measure it at high frequency, and ecosystem processes and structure will be examined. This will accomplished by comparing estuary/marsh complexes separated from the Altamaha River by one or two lagoonal estuary/marsh complexes that damp and attenuate the river signal. This spatial gradient is analogous to the temporal trend in riverine influence expected as a result of development in the watershed. A monitoring system will be implemented that documents physical and biological variables. The time trends and spatial distributions of these variables and of their variance structure will be used to address questions about the factors controlling distributions, trophic structure, diversity, and biogeochemistry.An existing GIS-based hydrologic model will be modified to incorporate changes in river water resulting from changes in land use patterns that can be expected as the watershed develops. This model will be linked to ecosystem models and will serve as a heuristic and management tool. Another consequence of coastal development is that as river flow decreases, groundwater flow increases and becomes nutrified. The effects of ground water discharge from the surficial aquifer in relatively pristine (Sapelo Island) will be compared against more urbanized (mainland) sites to assess the relative importance of fresh water versus nutrients to productivity, structure and biomass turnover rate in marshes influenced by groundwater. The effect of marine processes (tides, storm surge) on mixing across the fresh/salt interface in the surficial aquifer will be investigated. Additional physical studies will relate the morphology of salt marsh - tidal creek channel complexes to tidal current distributions and exchange. These findings will be incorporated into a physical model that will be coupled to an existing ecosystem model.This land/ocean margin ecosystem lies at the interface between two ecosystems in which distinctly different groups of decomposers control organic matter degradation. Fungal decomposers largely dominate the terrestrial ecosystem, while bacterial decomposers dominate the marine ecosystem. Both groups are important in salt marsh-dominated ecosystems. Specific studies will examine, at the level of individual cells and hyphae, the relationship bacteria and fungi in the consortia that decompose standing dead Spartina and other marsh plants and, examine how, or if, this changes along the salinity gradient.