Lidia Lins

Nematode communities in the Sai Gon River harbors in relation to tributyltin concentrations

The impact of toxic tributyltin (TBT) compounds was investigated on free-living nematode communities in the Sai Gon River. Samples were collected from 11 harbor stations downstream of the Sai Gon river plus one upstream station during the dry and rainy seasons. The results showed that all butyltin compound (mono-, di-, and tri) concentrations were relatively low compared to historical data from the same or adjacent estuaries, supporting the effectiveness of the 2009 ban on these products as antifouling. Nematode communities were typical for oligohaline regions showing a high spatial and temporal variability in abundance and diversity. Nematode community composition clearly differed between the two seasons, with the nematode communities being less variable in the rainy season compared to the dry season, while nematode communities differed significantly between stations. TBT values were still significantly negative correlated with nematode densities and selective deposit feeders during the dry season, partly confirming earlier experimental results on the response of nematodes to TBT. The historical presence of TBT contamination can possibly have caused a long-term impact on nematode communities in the Sai Gon river sediment, reflected in depressed densities during the dry season.

Nematode morphometry and biomass in the Saigon River harbours in relation to antifouling contaminants

Morphometry and biomass of nematode communities in different harbours of the Saigon River were investigated in the dry and wet seasons in relation to environmental variables such as total organic carbon, pH, conductivity, salinity and oxygen redox potential, in addition to concentrations of different butyltin compounds. The results indicated that nematodes in contaminated sediments from the Saigon River harbours were mainly characterised by slender morphotypes, whilst very few thin and stout nematodes were observed. Individual nematode biomass was generally low, especially in the wet season. There was no significant correlation between butyltin compounds and nematode morphometrics in the dry season but significant correlations were found for the wet season. Although significant correlations were observed for the wet season, the strong seasonal differences in nematode biomass spectra suggest a potential limitation in their use for environmental monitoring.