Abstract
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).
Highlights
Freshwater ecosystems include rivers, streams, lakes, freshwater swamps, peat swamps, rice fields and pools
Stable isotope analysis was conducted on biological samples of plants, aquatic insects and fish available from the study areas
The mean δ15N and δ13C values obtained displayed various degree of trophic position occurred in the rivers (Tables 1–2)
Summary
Freshwater ecosystems include rivers, streams, lakes, freshwater swamps, peat swamps, rice fields and pools. As rivers flowing to low reaches, their water quality, substrates and food sources for aquatic organisms altered as well. Food web studies have been used to understand linkage in energy flow between aquatic ecosystems and terrestrial ecosystems and integrate organic matter processing (Hershey et al 2010). The stable isotope approach has become broadly used in ecology study, providing the possibility of obtaining objective and repeatable measures of trophic position, food chain and length omnivory (Cabana & Rasmussen 1994). Stable isotope of carbon (δ13C) is used to identify the ultimate source of carbon, or the primary energy source for a group of organisms or for an ecosystem (Fry & Sherr 1984), while nitrogen (δ15N) become enriched when transferred through a food web by means of feeding and predation (Peterson & Fry 1987)
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