Abstract
Some organisms, such as aquatic insects, are transported from the upstream to downstream region of streams through a process called drift. This process occurs in passive and active ways and can be variable throughout the day, mainly between the nocturnal and diurnal periods. Here, we evaluate the periodicity of the drift of aquatic insects in two streams of the Middle Iguaçu basin, southern region of Brazil. We predicted that the drift of aquatic insects brings the highest richness, diversity and abundance during the nocturnal period, compared to the diurnal period. In addition, we expected that the composition of species is different between these periods. In each stream, aquatic insect sampling was carried out 10 times, for 24 hours, using drift nets. A total of 2,114 aquatic insect specimens were recorded, distributed in 26 families. Of these families, 20 were recorded during the diurnal period and 24 during the nocturnal period. Our results showed an increase in the diversity and abundance of aquatic insect drift in the nocturnal period. However, only abundance was significantly different between the periods. We attribute the higher abundance in nocturnal drift possibly to biological interactions. Thus, nocturnal drift can be a strategy of some aquatic insects to avoid visual predation by other invertebrates and/or vertebrates, in Neotropical streams. We highlight the importance of our study, because it can be used for comparison in surveys of lotic environments that have been impacted by human activity (e.g. by dam construction), which can alter the water flow, and consequently the pattern of insect drift.
Highlights
Lotic environments are characterized by having a unidirectional and continuous flow of water movement, and high heterogeneity in physical, chemical and geomorphological aspects along their route (Vannote, Minshall, Cummins, Sedell, & Cushing, 1980; Covino, 2017)
Our results showed an increase in the diversity and abundance of aquatic insect drift in the nocturnal period
We highlight the importance of our study, because it can be used for comparison in surveys of lotic environments that have been impacted by human activity, which can alter the water flow, and the pattern of insect drift
Summary
Lotic environments are characterized by having a unidirectional and continuous flow of water movement, and high heterogeneity in physical, chemical and geomorphological aspects along their route (Vannote, Minshall, Cummins, Sedell, & Cushing, 1980; Covino, 2017). The intensity of organisms drifting in the water column can vary throughout the day, mainly between the nocturnal and diurnal periods, owing to the availability of hours with the presence or absence of light (Elliott, 1969; Mendonza, Montoya, & Perez, 2018). In this way, the periodicity (luminosity) influences the chemical and physical conditions of water and the biotic interactions between the communities (Douglas, Forrester, & Cooper, 1994; Guasch, Armengol, Martı,́ & Sabater, 1998; Kayombo, Mbwette, Mayo, Katima, & Jørgensen, 2002)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
