Freshwater Inflow Biotic Index (FIBI)for the Lavaca-Colorado Estuary, Texas

摘要

Freshwater inflow is an important source of physical variability in estuaries. Effects ofwater flow are dynamic, and it is impossible to sample all conditions as they vary overspace and time. Benthos, however, are fixed in place, continuously sample the overly-ing water conditions, and demonstrate a variety of consistent responses to multiplesources of stress. Benthic indices of biotic integrity (BIBIs) have been particularly use-ful for assessing aquatic systems. However most indices have focused on assessingeffects related to changes in water quality rather than water quantity. This study devel-ops a Freshwater Inflow Biotic Index (FIBI) to determine how changes in freshwaterinflow affect benthic populations, which in turn reflect the ecological condition of anestuary. Based on benthic succession theory and long-term data, 12 biotic metricswere chosen that characterized benthic community structure in response to inflowregimes. The metrics were ranked and then reduced to one variable using principalcomponent analysis (PCA) to form the index. The FIBI and hydrological PC variableswere significantly correlated, indicating that benthic communities respond to changesin salinity and do so in a relatively predictable manner. If inflow is reduced (i.e., salinityincreased), it will cause upstream communities to take on characteristics of down-stream communities. The FIBI successfully characterized effects of a salinity gradientin the Lavaca-Colorado estuary, and application of the FIBI approach should be suc-cessful in other estuarine ecosystems.