Using Zooplankton as Bioindicator for Trophic State of Irrigation Canals in Gia Lam, Hanoi

Abstract

     Zooplankton is not only dependent on the trophic state through food chains of algae but also controls nutrient levels through consumtion of algae. The study was conducted with 16 irrigation canals in the district of Gia Lam that had different nutrient levels to prove the relationship. Many of these irrigation canals were contaminated by various waste sources, showing nutritional status from moderate to high level (60-100 points). From January to May (2015), 71 species of zooplankton were identified with Rotifers being dominant both in number of species (39 species) and density (> 70%). The diversity index was moderate at medium trophic level (H' was 2.52 at the TSI of 60 - 80) and lower in high trophic level (H’ was 1.83 at the TSI of 80-100). The species of lower trophic levels (TN < 7 mg/l and

TP<0.4 mg/l) included Brachionus budapestinensis, Brachionus falcatus, Brachionus forficula, Keratella tropica (Rotifer); Sida crystallina, and Ceriodaphnia quadraugula (Cladoceran). The species adaptable to moderate to high trophic included Ceriodaphnia laticaudata, Alona davidi (Cladocerans); Eucyclops serrulatus, and Ectocyclops phaleratus (copepods). They may be the pollution sensitive and pollution resistant species.