Determination of Trophic Structure in Selected Freshwater Ecosystems by using Stable Isotope Analysis

Stable isotope analysis has been used extensively to establish trophic relationships in many ecosystems. Present study utilised stable isotope signatures of carbon and nitrogen to identify trophic structure of aquatic food web in river and rice field ecosystems in Perak, northern peninsular Malaysia. The mean δ¹³C values of all producers ranged from -35.29 ± 0.21 to -26.00 ± 0.050‰. The greatest δ¹⁵N values noted was in zenarchopterid fish with 9.68 ± 0.020‰. The δ¹⁵N values of aquatic insects ranged between 2.59 ± 0.107 in Elmidae (Coleoptera) and 8.11 ± 0.022‰ in Nepidae (Hemiptera). Correspondingly, with all the δ¹³C and δ¹⁵N values recorded, it can be deduced that there are four trophic levels existed in the freshwater ecosystems which started with the producer (plants), followed by primary consumer (aquatic insects and non-predatory fish), secondary consumer (invertebrate predators) and lastly tertiary consumer (vertebrate predators).