Interactive effects of nutrients and salinity on zooplankton in subtropical plateau lakes with contrasting water depth

Abstract

Both eutrophication and salinization are growing global environmental problems in freshwater ecosystems, threatening the water quality and various aquatic organisms. However, little is known about their interactive effects on theses stressors and the role of lake depth on these interactions. We used field surveys to compared zooplankton assemblages over four seasons in eight Yunnan Plateau lakes with different trophic states, salinization levels, and water depths. The results showed that: 1) the species number (S), density (DZoop), and biomass (BZoop) of zooplankton exhibited strong seasonal dynamics, being overall higher in the warm seasons. 2) Data collected over four seasons and summer data both revealed highly significant positive relationships of S, DZoop, and BZoop with total nitrogen (TN), total phosphorus (TP), and phytoplankton chlorophyll a (Chl a). 3) S, DZoop, and BZoop displayed a unimodal relationship with salinity, peaking at 400–1000 μS/cm (conductivity, to reflect salinity). 4) The two large-sized taxa (cladocerans and copepods) generally increased at low-moderate levels of TN, TP, Chl a, and Cond and was constant or decreased at high levels. The average body mass (biomass/density) of crustaceans decreased with increasing TN, TP, Chl a, and conductivity. Our findings indicate that zooplankton may be more vulnerable in deep lakes than in shallow lakes when exposed to conductivity stress even under mesotrophic conditions, and the overall decrease in size in zooplankton assemblages under the combined stress of eutrophication and salinization may result in a lowered grazing effect on phytoplankton.

Temporal variation and spatial factors affecting zooplankton communities in freshwater rock pools

“…This can be attributed to the replenishment of nutrients due to increased rainfall, thereby enhancing the availability of resources (Abrantes et al, 2006). This increased availability of resources in the postrainy period compared to drier periods (Yang et al, 2023) likely promotes the growth and reproduction of zooplankton in wet periods (Bonecker et al, 2001;Lansac-Tôha et al, 2009). While it is widely accepted that temperature, pH, and salinity shape zooplankton communities in freshwater environments as they vary over time, our findings did not demonstrate any impact of such seasonality on species richness and evenness.…”

“…In contrast, for temporary water bodies, even if environmental variables change considerably through time, the changes in water availability are even more drastic, as those pools have a large drought propensity. Consequently, the seasonal variation in water availability might have direct and indirect effects on interspecific competition and predation intensity, altering species composition (Pearman, 1995;Govaert et al, 2021;Yang et al, 2023;Castilho-Noll et al, 2023). Moreover, given that the spatial distance did not affect species composition in pools, it is likely that dispersal is not limited in the studied system.…”

Sublethal impacts of different road salts on a freshwater macrophyte: Altered productivity, acclimation, and lag effects

“…Therefore, stability in macrophyte beds under stressful conditions would be beneficial for the ecosystem as a whole. In addition, increased salinity often occurs with other stressors to cause synergistic effects in many aquatic taxa (Coldsnow & Relyea, 2021; Hintz & Relyea, 2019; Kaushal et al, 2019; Stoler et al, 2018; Yang et al, 2023), which highlights the need to examine this question in freshwater macrophytes.…”

Effect of land use and environmental variables on phytoplankton community structure in high-elevation river, upper Yangtze river, China

“…Under the combined pressure of nutrients and salinity, the size of zooplankton community can change the grazing effect on planktonic algae, and may adversely affect the community structure and abundance of planktonic algae (Yang et al, 2023). There is a significant correlation between zooplankton density and phytoplankton density in the Tibet section of Lantsang, and phytoplankton can affect zooplankton density through upward regulation (Du et al, 2022).…”