Maroneze, D.M. (2017). Interações entre invertebrados planctônicos de lagoas impactadas por peixes não-nativos (médio rio Doce – MG): uma abordagem experimental e paleolimnológica. Interactions between planktonic invertebrates from lakes impacted by non-native fish (middle Doce River – MG): an experimental and paleolimnological approach. Instituto de Ciências Biológicas, Tese de Doutorado, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. 237 pp. [In Portuguese and English].

510176

Maroneze, D.M.

2017

237 pp. [In Portuguese and English]

Publication

http://hdl.handle.net/1843/75230

Available for editors  

Currently, the trophic webs of several middle Doce River lakes (MG) are strongly impacted by non-native piscivorous fish. In such communities, the native planktivorous ichthyofauna became scarce and the predatory Chaoborus larvae (Diptera) may have formed dense populations (“ecological release”). As a result, small-sized cladocerans were possibly suppressed or even became extinct, which may have stimulated the growth of phytoplankton biomass. This research had as general objective to study the ecology of Chaoborus larvae from two middle Doce River lakes (Lakes Carioca and Jacaré). Specifically, it sought to investigate how the local Chaoborus larvae interact with each other and with their zooplanktonic prey. For this, we used different research approaches: in situ experiments (mesocosms), larval diet description based on the crop analysis, traditional population monitoring techniques, larval biometry, paleolimnological evaluation of sediments, visual observations of live zooplankters, and laboratory predation experiments. According to our mesocosm experiments in Lake Carioca, the Chaoborus larvae does not strongly control (top-down) the dominant rotifers and cyclopoid copepods. Locally, the larvae of the three sympatric Chaoborus species are omnivorous ingesting a wide variety of prey items throughout their development. There, heterospecific individuals of the same instar exhibit distinct morphometric characteristics and relatively low diet overlap which, in theory, may be contributing to their coexistence. The microfossil analysis of invertebrates indicated a significant numerical decline of cladoceran caparaces (genus Bosmina) in the sediment samples corresponding to the period after the invasion of non-native piscivorous fish. Thus, in fact, they may have negatively affected not only their direct prey species (native planktivorous fish) but also the organisms of other trophic levels (herbivorous cladocerans). Additionally, our visual observations of live zooplankters from Lake Jacaré showed that an anti-predation behavioral Physocypria schubarti ostracods by local Chaoborus larvae. Laboratory predation experiments also suggested that high densities of this ostracod speciesin the water column negatively affect the predatory performance of Chaoborus larvae on Ceriodaphinia silvestrii neonates. In general, our data demonstrated how complex and variable can be the ecological interactions established between freshwater planktonic invertebrates even in poor communities highly impacted by non-native piscivorous fish such as those from the middle Doce River lakes.

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