LTER - Georgia Land/Ocean Margin Ecosystem

将在佐治亚州中部海岸萨佩洛岛附近建立一个长期生态研究地点。这是一个障碍岛和沼泽综合体，阿尔塔马哈河是美国东海岸最大和最不发达的河流之一，是主要的淡水来源。将调查由地表水和地下水向沿海地区输送的当地和偏远高地地区之间的联系。我们将研究河流流量(主要是盐度)驱动的环境因素的可变性与生态系统过程和结构之间的关系，因为我们可以高频测量它。这将通过比较与阿尔塔马哈河分开的河口/沼泽复合体来实现，这些河口/沼泽复合体由一个或两个泻湖河口/沼泽复合体隔开，这些复合体抑制和衰减了河流信号。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。将实施一个监测系统，记录物理和生物变量。这些变量及其方差结构的时间趋势和空间分布将被用来解决控制分布、营养结构、多样性和生物地球化学的因素问题。现有的基于地理信息系统的水文模型将被修改，以纳入随着流域发展而预期的土地利用模式变化导致的河水变化。该模型将与生态系统模型相联系，并将作为启发式和管理工具。沿海开发的另一个后果是，随着河流流量的减少，地下水流量增加并变得营养丰富。从相对原始的(萨佩洛岛)地表含水层排放的地下水的影响将与城市化程度较高的(大陆)地点进行比较，以评估受地下水影响的沼泽中淡水与营养物质对生产力、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)对表层含水层中淡水/盐分界面混合的影响。其他物理研究将把盐沼-潮汐小溪航道复合体的形态与潮流分布和交换联系起来。这些发现将被合并到一个物理模型中，该物理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上，在这两个生态系统中，明显不同的分解者群体控制着有机物的降解。真菌分解者在很大程度上主导了陆地生态系统，而细菌分解者主导了海洋生态系统。在以盐沼为主的生态系统中，这两个群体都很重要。具体的研究将在单个细胞和菌丝的水平上检查分解死立的斯巴达和其他沼泽植物的联合体中细菌和真菌的关系，并检查这种关系如何或是否沿盐度梯度变化。

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.