Rio Grande water and sediment quality data affecting benthic macrofaunal community obtained from 2000-10-24 to 2005-08-06

The lower Rio Grande is a river-dominated estuary that serves as the border between Texas, USA and Tamaulipas, Mexico. River estuaries encompass the section of the river influenced by tidal exchange with the Gulf of Mexico, but the connection with the Rio Grande is intermittent and can be temporarily open or closed. During the 4.8-year study period, the river mouth was closed 30% of the time, mostly during average or dry climatic conditions, with the temporary closing of the river mouth being linked to hydrology. When the Rio Grande estuary is closed, salinity is low, nitrate plus nitrite are low, and ammonium is high, but chlorophyll is similar. Benthic macrofaunal abundance and biomass are higher when the river mouth is closed than open. Benthic macrofaunal community structure divided into two groups: chironomid larvae and Oligochaeta dominated when the river mouth was closed, whereas polychaetes Mediomastus ambiseta and Streblospio benedicti dominated when the river mouth was open. The implications of these results for managing freshwater flows are that the open and closed conditions each have a characteristic benthic macrofaunal community that is strongly influenced by system hydrology.

格兰德河下游（Rio Grande）是一条以河流作用为主导的河口湾，作为美国得克萨斯州与墨西哥塔毛利帕斯州的界河。河口湾指受墨西哥湾潮汐交换影响的河流河段，但格兰德河的河道连通性呈间歇性，可临时开启或封闭。在为期4.8年的研究周期内，河口封闭状态占总时长的30%，多发生在平水或干旱气候条件下，河口临时封闭与流域水文状况密切相关。当格兰德河河口处于封闭状态时，水体盐度、硝态氮与亚硝态氮含量均较低，铵态氮含量较高，但叶绿素含量无显著差异。河口封闭时的底栖大型动物（benthic macrofaunal）丰度与生物量均高于开放状态。底栖大型动物群落结构可分为两类：河口封闭时，以摇蚊幼虫（chironomid larvae）和寡毛类（Oligochaeta）为优势类群；河口开放时，则以多毛类（polychaetes）的Mediomastus ambiseta与Streblospio benedicti为优势类群。本研究结果对淡水流量管理的启示在于：河口的开放与封闭两种状态分别对应特征性的底栖大型动物群落，且此类群落的组成强烈受系统水文状况的调控。