Biodiversity of aquatic insect and physicochemical water quality parameters in Mae Tao

Biodiversity of aquatic insect and physicochemical water quality parameters in receiving water bodies in Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom Province, central Thailand were assessed during October 2010 to September 2011. Seven sampling stations, each 100 m long, were established. Three replicates of samplings by aquatic D-net were used at sampling sites. A total of 4,257 individual of aquatic insect were collected during one year. Six Orders and 12 families were recorded in this study. The family Hydropsychidae and Chironomidae were the most abundance of aquatic insects that found in receiving water bodies. The CCA revealed the family Mesoveliidae and Chironomidae were correlated with alkalinity in receiving water bodies, whereas dissolved oxygen was correlated with family Baetidae, Coenagrionidae, Hydrophilidae, and Helotrephidae. Signs of increasing water quality deterioration were evident in the result of the physicochemical analyses.

Aquatic insects can accumulate pollutants such as cadmium from stream sediments. This research aimed to monitor cadmium concentrations in both larvae and adult Hydropsychidae (Trichoptera, Insecta) in Mae Tao (MT1 to MT5) and Mae Ku (MK2 and MK8) watersheds in northern Thailand. Samples were collected twice a month from July 2011 to May 2012 at seven sampling sites. The cadmium concentrations in the stream sediments ranged from 0.12 to 21.5 mg kg-1 wet weight. The highest concentration was recorded from the MT3 sampling site (21.5 mg kg-1), which is also closest to a mining area. The lowest concentration was recorded from the MK2 sampling site (0.12 mg kg-1). Cadmium concentrations in both larvae and adult Hydropsychidae were not significantly different at all sampling sites. However, the cadmium concentrations in Hydropsychidae larvae that ranged from 0.07-1.70 mg kg-1 were higher than the detected cadmium in adult samples (average 0.020 mg kg-1). There was no significant correlation between cadmium concentrations in sediments, and in both larvae and adult Hydropsychidae. Concentrations of cadmium in adult Hydropsychidae in this study were low. Even though the contamination of heavy metals was low in adult Hydropsychidae, long-term exposure to heavy metals could seriously impact terrestrial animals such as birds and bats that consume these insects.