Abstract
We evaluated the response of the biomass of aquatic macrophytes under limnological changes after water level fluctuation (WLF) of two tropical reservoirs (R1 and R2), located in northeastern Brazil. Initially we tested the hypothesis that post-WLF limnological conditions and biomass of macrophytes increase or decrease, depending on the variable or species. We monitored a 4 × 50 m permanent plot, in four expeditions per period (pre- or post-WLF), assessing species biomass and 10 limnological variables. We utilized 0.25 × 0.25 m quadrats for biomass. Once the effect of WLF in limnological variables and species biomass was confirmed, we utilized Canonical Correspondence Analysis to understand the relationship between limnological variables and species biomass. The abundant and/or dominant species in pre-WLF of R1 ( Pistia stratiotes, Eichhornia crassipes and Salvinia auriculata) and R2 (Paspalidium geminatum and S. auriculata) reduced their biomass post-WLF and were correlated with temperature, total phosphorous and nitrate. The reduced biomass of P. stratiotes, E. crassipes and S. auriculata in post-WLF widened resource availability, allowing coexistence of species. Therefore, we suggest that the change of limnological conditions in post-WLF in artificial lakes acts only as a moderator factor of the interspecific interaction (especially coexistence), without direct relation between these conditions and species biomass.
Highlights
The present understanding of the ecology of aquatic ecosystems does not yet allow to delineate structuring of macrophyte communities in environments periodically influenced by water level fluctuations (WLF), such as artificial lakes (Zohary and Ostrovsky, 2011; Cunha-Santino et al, 2016; Moura Júnior et al, 2016)
We confirmed the hypothesis that one WLF causes changes in the limnological conditions and species biomass of aquatic macrophytes
Water temperature is a variable directly related with the production of aquatic plant organic matter (Bottino et al, 2013)
Summary
The present understanding of the ecology of aquatic ecosystems does not yet allow to delineate structuring of macrophyte communities in environments periodically influenced by water level fluctuations (WLF), such as artificial lakes (Zohary and Ostrovsky, 2011; Cunha-Santino et al, 2016; Moura Júnior et al, 2016). Most specialists on aquatic macrophytes believe that the specificities of the water abiotic conditions after WLF determine the capacity of plant biomass production (Lacoul and Freedman, 2006; Henry-Silva et al, 2008; Zohary and Ostrovsky, 2011; Bottino et al, 2013) Some biotic variables such as interespecific competition and coexistence are relevant factors in the structuring of communities (Van Gerven et al, 2015; Moura Júnior et al, 2016) or biomass of aquatic macrophytes (Camargo and Florentino, 2000; Byun et al, 2017) in environment under variation of WLF
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