Spatial and temporal variation of nine elements (Ba, Ca, Cu, Mg, Mn, Na, Se, Sr, and Zn) and some additional environmental parameters (salinity, water levels, and conductivity) were examined over two 2,000 km along the length of the main Mekong River channel from Luang Prabang in Northern Lao PDR to the Mekong Delta in Vietnam. Longitudinal profiles of some dissolved elemental concentrations varied significantly along the river channel. For example, Sr concentration in marine water was up to 83 times higher than in fresh water. By contrast, Ba concentration was around 4 times higher in fresh water than in marine water, but was significantly influenced by inflows from major tributaries in Cambodia (dilution effects). We found dissolved Ba was elevated in low salinity. Furthermore, Sr concentration was more variable than Ba, especially in the Mekong Delta due to different tidal influences in each of the Delta branches. Selenium was only present along the coast and one river branch in the delta. The variation in water chemistry of the Mekong main channel identified through this study provides information that can be used in the interpretation of regional fish movements using otolith chemistry, including across the freshwater, estuarine and marine interface. Accurate interpretation is essential given the Lower Mekong Basin has a high biodiversity that is under threat from rapid development, and substantial knowledge gaps exist on the life history requirements of numerous fish species.

在沿长度的两千公里范围内，检查了九种元素（Ba，Ca，Cu，Mg，Mn，Na，Se，Sr和Zn）的时空变化以及一些其他环境参数（盐度，水位和电导率）从老挝北部的琅勃拉邦到越南的湄公河三角洲的湄公河主要河道。一些溶解的元素浓度的纵向剖面沿河道变化很大。例如，海水中的Sr浓度比淡水高83倍。相比之下，淡水中的Ba浓度比海水中的Ba浓度高约4倍，但受到柬埔寨主要支流的流入的显着影响（稀释作用）。我们发现在低盐度下溶解的Ba升高。此外，Sr的浓度比Ba更易变，特别是在湄公河三角洲，因为每个三角洲支流的潮汐影响不同。硒仅存在于沿海地区和三角洲的一个河流分支中。通过这项研究确定的湄公河主河道水化学变化提供了可用于利用耳石化学来解释区域鱼类运动的信息，包括跨淡水，河口和海洋界面。鉴于湄公河下游流域的生物多样性高度丰富，受到快速发展的威胁，而且在众多鱼类的生活史需求上存在着巨大的知识鸿沟，因此准确的解释至关重要。通过这项研究确定的湄公河主河道水化学变化提供了可用于利用耳石化学来解释区域鱼类运动的信息，包括跨淡水，河口和海洋界面。鉴于湄公河下游流域的生物多样性高度丰富，受到快速发展的威胁，而且在众多鱼类的生活史需求上存在着巨大的知识鸿沟，因此准确的解释至关重要。通过这项研究确定的湄公河主河道水化学变化提供了可用于利用耳石化学来解释区域鱼类运动的信息，包括跨淡水，河口和海洋界面。鉴于湄公河下游流域的生物多样性高度丰富，受到快速发展的威胁，而且在众多鱼类的生活史需求上存在着巨大的知识鸿沟，因此准确的解释至关重要。