Date Received: 07-06-2013 / Date Accepted: 25-08-2013
Trophic Diatom Index (TDI) first suggested by Kelly and Whitton in 1995 is an index assessing status of organic nutrients in aquatic ecosystems which bases on the total of diatom species and individuals that indicate the eutrophication. This study used TDI values to evaluate nutrient situation in the sediment at Can Gio Mangrove Biosphere Reserver after Durian typhoon (December 6, 2006). The study analyzed 72 soil samples and 108 diatom samples in the sediment for two seasons. Analysis of variance (ANOVA) showed that in the rainy season the mean TDI was significantly different between three sites: non-forest, mix and forest (F=10.88; P=0.0012). In contrast, in dry season, the mean TDI was not significantly different between three sites (F=0.45; P=0.65). We found species Achnanthidium minutissimum which is indicative of low total phosphorus and species Luticola goeppertiana, Navicula recens indicating high total phosphorus. However, we did not find correlation between the mean TDI and the total phosphorus and total nitrogen in the study. The studies on percent tolerant valves and orthophosphate concentration may help clearly explain about the relationship between the TDI and total phophorus and total nitrogen concentrations.
