Food web pathways for fish communities in small tropical streams
Author(s)
Reis, Andressa da Silva
Albrech, Miriam Pilz
Bunn, Stuart E
Griffith University Author(s)
Year published
2020
Metadata
Show full item recordAbstract
It is often assumed that invertebrate consumers in small tropical streams are dependent on allochthonous sources, although recent studies indicate that algae can form the base of food webs in tropical streams. Fish in tropical streams can feed across several trophic levels and the origin and path of energy and nutrient flow is uncertain for many species. We collected fish, insects, periphyton, and leaf litter from 20 streams across four Atlantic Forest catchments. We analysed stomach contents of fish to define trophic guild and fish dietary trophic position. We also analysed stable isotopes of carbon and nitrogen of fish and ...
View more >It is often assumed that invertebrate consumers in small tropical streams are dependent on allochthonous sources, although recent studies indicate that algae can form the base of food webs in tropical streams. Fish in tropical streams can feed across several trophic levels and the origin and path of energy and nutrient flow is uncertain for many species. We collected fish, insects, periphyton, and leaf litter from 20 streams across four Atlantic Forest catchments. We analysed stomach contents of fish to define trophic guild and fish dietary trophic position. We also analysed stable isotopes of carbon and nitrogen of fish and their resources to identify the main basal resources of the food web and to estimate trophic positions and identify the path of energy flow. We found that autochthonous sources were the primary resource base for fish communities. Trophic positions estimated from diet and isotopes were similar and correlated for insectivore and algivore–insectivore fish, but not for algivore–detritivore or omnivore fish. Using path analysis, fish classified as algivore–detritivores appear to have derived their biomass through a diet of primary consumer insects and periphytic algae and thus, are more likely to play a trophic role as algivore–insectivores in these streams. However, omnivores probably derived much of their biomass from aquatic insects. Our findings support other studies of tropical systems in which the main basal resource is autochthonous, even in small streams. We also show that the assignment to a specific trophic guild for some fish species, based on gut contents, does not reflect what they assimilate into their bodies. In some species, food sources that are uncommon can make a disproportionately important contribution to their biomass. This study affirms the important role of inconspicuous algal resources in aquatic food webs, even in small forested streams, and demonstrates the effectiveness of taking a combined approach of diet analysis, isotopic tracing, and modelling to resolve food web pathways where the level of omnivory is high.
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View more >It is often assumed that invertebrate consumers in small tropical streams are dependent on allochthonous sources, although recent studies indicate that algae can form the base of food webs in tropical streams. Fish in tropical streams can feed across several trophic levels and the origin and path of energy and nutrient flow is uncertain for many species. We collected fish, insects, periphyton, and leaf litter from 20 streams across four Atlantic Forest catchments. We analysed stomach contents of fish to define trophic guild and fish dietary trophic position. We also analysed stable isotopes of carbon and nitrogen of fish and their resources to identify the main basal resources of the food web and to estimate trophic positions and identify the path of energy flow. We found that autochthonous sources were the primary resource base for fish communities. Trophic positions estimated from diet and isotopes were similar and correlated for insectivore and algivore–insectivore fish, but not for algivore–detritivore or omnivore fish. Using path analysis, fish classified as algivore–detritivores appear to have derived their biomass through a diet of primary consumer insects and periphytic algae and thus, are more likely to play a trophic role as algivore–insectivores in these streams. However, omnivores probably derived much of their biomass from aquatic insects. Our findings support other studies of tropical systems in which the main basal resource is autochthonous, even in small streams. We also show that the assignment to a specific trophic guild for some fish species, based on gut contents, does not reflect what they assimilate into their bodies. In some species, food sources that are uncommon can make a disproportionately important contribution to their biomass. This study affirms the important role of inconspicuous algal resources in aquatic food webs, even in small forested streams, and demonstrates the effectiveness of taking a combined approach of diet analysis, isotopic tracing, and modelling to resolve food web pathways where the level of omnivory is high.
View less >
Journal Title
Freshwater Biology
Volume
65
Issue
5
Subject
Environmental sciences
Biological sciences
Science & Technology
Life Sciences & Biomedicine
Ecology
Marine & Freshwater Biology