Spatial and temporal variability in water quality, sediment, and benthic macroinvertebrates in the Mae Klong river, Thailand

Diversity and abundance of macrobenthic fauna have been extensively used to determine the quality of the aquatic environment. The Mae Klong river consists of several types of habitats which are important for human uses. The water quality of the river has deteriorated due to wastewater discharged from human activities. Although there have been many efforts to improve water quality in the past, problems still remain. This study used benthic macroinvertebrates as key indicators of water quality and sediment in the Mae Klong river and its tributaries. Spatio-temporal variability in water quality, sediment, and benthic macroinvertebrates in the Mae Klong river was investigated across 21 stations between April 2016 and March 2017, at an interval of three times per season (hot, rainy, and cold). Principal component analysis revealed that water quality variables in the cold season were clearly different from those in the hot and rainy seasons. Total organic matter, sulfide, and median grain size in the sediment were not different, whereas concentrations of copper, lead, cadmium, and zinc in the rainy and cold seasons were different from those in the hot season. Three phyla, 26 orders, 58 families, and 118 species of benthic macroinvertebrates were found. Species and their distributions were not different among the three seasons, but varied by location (upper, middle and lower parts of the river). The conditions of the upper Mae Klong River are satisfactory, but the lower Mae Klong River is contaminated with pollution. The main factors affecting the community structure, composition, and distribution of benthic macroinvertebrates in the Mae Klong River include conductivity, total organic matter, and sulfide. This present study also demonstrates that benthic macroinvertebrate taxa, including the families Ephemeridae, Baetidae, Caenidae (Ephemeroptera), Libellulidae (Odonata) and class Polychaeta (Perinereis) are useful for assessment of the health of Mae Klong river