Water‐level fluctuations regulate the structure and functioning of natural lakes

Abstract

1. Despite becoming one of the main pressures on aquatic ecosystems globally, understanding of the ecological impacts of altered water-level regimes in lakes lags far behind that of other human disturbances (e.g. eutrophication, acidification). 2. We employed a multifaceted approach to explore the potential importance of water-level fluctuations (WLF) for the structure and functioning of littoral zones and multiple trait responses of primary producers and benthic consumers across a range of natural lakes. 3. We found that lakes with high WLF had significantly more coarse littoral substrata with less coverage of macrophyte vegetation in the shallows than in lakes with low WLF. Lakes with high WLF also had greater proportions of motile diatom species and omnivorous benthic invertebrates in shallow waters, altered taxonomic and trophic structure of benthic consumers and more homogeneous algal and benthic invertebrate assemblages. 4. Variation along the littoral depth gradient needs to be examined when assessing the impacts of hydrological pressures in lakes. We found that depth interacted with WLF in its effects on habitat structure and mediated the response of both producer and consumer benthic assemblages to WLF. 5. Our results indicate that amplified WLF significantly affect both the structure and functioning of lake ecosystems. Given the growing importance of WLF as an increasingly pervasive pressure on lake ecosystems worldwide, our findings have important implications for the conservation and management of global aquatic biodiversity. Inclusion of both biological traits and sampling along a depth gradient in existing and in future monitoring programmes could improve significantly the ability to detect and predict effects of altered patterns of WLF on lake ecosystems.

Rainfall and hydrological stability alter the impact of top predators on food web structure and function

“…One way in which rainfall may affect aquatic ecosystems is by influencing the dynamics of water level (Lake, ). Water fluctuations are known to have a large effect on the structure and functioning of aquatic habitats (Evtimova & Donohue, , ). Specifically, repeated drying and inundation cycles may represent a source of disturbance to aquatic communities (Vanschoenwinkel et al ., , ), constraining the set of species able to cope with such environmental conditions (Williams, ).…”

“…Specifically, repeated drying and inundation cycles may represent a source of disturbance to aquatic communities (Vanschoenwinkel et al ., , ), constraining the set of species able to cope with such environmental conditions (Williams, ). In accordance with this view, several studies demonstrate that hydrological disturbance may result in the dominance of stress‐tolerant species, as well as a decrease in species richness, in trophic diversity, in secondary production (Chase, ; Ledger et al ., , ; Evtimova & Donohue, , ) and either an increase (Chase, ; Vanschoenwinkel et al ., ) or decrease (Therriault & Kolasa, ; Evtimova & Donohue, , ) in the similarity among communities.…”

Habitat use and preference of adult perch (Perca fluviatilis L.) in a deep reservoir: variations with seasons, water levels and individuals

“…Habitat complexity changes with water level (WL), particularly in the littoral zone (Zohary & Ostrovsky, 2011). For instance, high WLF (frequent and wide) may engender coarser littoral substrate with less macrophyte coverage in the shallow zones of lakes (Evtimova & Donohue, 2016), which in turn reduce the productivity and biodiversity of these areas (Wetzel, 1990;Evtimova & Donohue, 2014). More specifically, studies have shown that WLF can affect various ecological aspects of fish species such as their growth, distribution and behaviour (e.g.…”

“…As WLF can modify the availability of the different littoral habitat types (Zohary & Ostrovsky, 2011;Evtimova & Donohue, 2016), we expected a shift of perch habitat preferences with WL. For example, when an habitat becomes very scarce, if perch keeps on frequently using it, then its preference will automatically raise; on the contrary, if perch switches to another habitat, its preference will decline for this scarce habitat and raise for the other.…”

The survival and behavioural responses of a near-shore chironomid and oligochaete to declining water levels and sandy substratum drying

“…Water-level fluctuations are the most important factor affecting the habitat of near-shore benthic fauna (Furey et al, 2004(Furey et al, , 2006Brauns et al, 2008;Poznańska et al, 2010;Evtimova & Donohue 2016). The fluctuations are caused by anthropogenic as well as natural disturbances, including disruption of natural river flows by dams (Nilsson & Berggren, 2000), extensive abstraction of water resources for human consumption and industrial use (Neff et al, 2000) and/ or fast urbanisation and reduction in riparian vegetation (Verdonschot et al, 2010).…”