Isolating top-down effects of aquatic macroconsumers on benthic structure and function in a neotropical stream
Binderup, Andrew Joseph
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Macroconsumer taxa, such as fishes and crustaceans, can exert strong top-down effects on ecosystem properties and processes in streams and rivers. Previous work in montane streams in Trinidad showed that different assemblages of consumers exert different effects on benthic ecosystems. This study employed novel methodology to separate out effects of individual consumer taxa, using diurnally- and nocturnally- active electric fields. We found that one species in particular, the guppy (Poecilia reticulata) exerted both direct and indirect top-down effects, directly slowing rates of algal accrual via direct consumption of benthic biofilm material, while indirectly speeding up the process of leaf decomposition, likely due to an interruptive effect on a trophic cascade that occurs between an insectivorous fish, Rivulus hartii, a shredding invertebrate, Phylloicus hansoni, and the decay rate of leaf litter. This study helped to further our understanding of ecological-evolutionary interactions in situ, using guppies as a model organism.