Does artificial drawdown affect zooplankton structure in shallow lakes? A short-term study in a tropical reservoir

Abstract

Water level fluctuation by artificial drawdown is one management activity that has the potential to control macrophyte growth, but there is little knowledge of how this operational procedure affects other biotic components of the ecosystem. This study investigated zooplankton dynamics in response to artificial drawdown over a short timeframe (13 days) in a Brazilian reservoir, by examining the impact on zooplankton communities in two shallow lakes (Lake Pedra Branca-LPB, and Guaritá-LG) connected to a reservoir (Salto Grande) that undergo sudden and remarkable fluctuations in their water levels. Zooplankton communities were sampled in both lakes before (pre-drawdown), during (low water), and after (post-drawdown) the artificial drawdown procedure. In LPB, drawdown resulted in an increase in zooplankton density, and temporarily changed the community in association with an increase in water conductivity and presence of non-planktonic organisms during the low water phase. In LG, drawdown had no significant effect on zooplankton community between the phases before and during the drawdown event. The results from this study suggest that artificial drawdown over a short timeframe in reservoir systems do not negatively affect the overall density, richness, and diversity of zooplankton communities in marginal shallow lakes.

Water‐level drawdowns can improve surface water quality and alleviate bottom hypoxia in shallow, eutrophic water bodies

“…In contrast, the abundances of cyclopoids and calanoids increased after the water‐level drawdowns. This result is consistent with previous findings in shallow lakes (Chaparro et al, 2011; Havens et al, 2007; Portinho & Nogueira, 2017). Cyclopoids can feed efficiently on cyanobacteria, and by breaking down cyanobacterial colonies and filaments into smaller pieces, they can suppress cyanobacterial blooms (Urrutia‐Cordero et al, 2015).…”

“…Even in the absence of submerged macrophytes, however, water-level drawdown can modify stratification and mixing regimes, promote reoxygenation of bottom waters (Baldwin et al, 2008;da Costa et al, 2016;Naselli-Flores & Barone, 2005;Noges & Noges, 1999), and reduce the abundance of phytoplankton and cyanobacteria (da Costa et al, 2016;Lehman et al, 2009;Noges et al, 2003;Serruya & Pollingher, 1977;Teferi et al, 2014). It has also been reported that water-level drawdown can increase periphyton abundance and the hatching of cladoceran resting eggs (Chaparro et al, 2011;Noges & Noges, 1999;Portinho & Nogueira, 2017;Rodusky, 2010). These biological changes may indirectly help to improve water quality.…”

eDNA of zooplankton reveals the ecological community thresholds for key environmental factors in the Baiyangdian Lake aquatic ecosystem

“…Zooplankton are sensitive to changes in the environment, and their community structure will be affected by changes in water temperature, pH, and other environmental factors. This sensitivity is conducive to the evaluation of environmental water quality, and thus zooplankton are often used as indicators in environmental monitoring [2][3][4][5][6]. In aquatic ecosystems, species are usually identified by traditional morphological methods.…”