Journal
ENVIRONMENTAL POLLUTION
Volume 296, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.envpol.2021.118770
Keywords
Daphnia; Freshwater; Life history; Road salt; Salinization
Categories
Funding
- National Natural Science Founda-tion of China [31730105]
- Priority Academic Program Devel-opment of Jiangsu Higher Education Institutions
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The salinization of freshwater systems is a common problem caused by human activities and climate change. It threatens freshwater biodiversity and resources, particularly affecting cladocerans at individual and population levels. Different-sized cladocerans have different sensitivities to salinization, with smaller species being more sensitive. Freshwater salinization may lead to the replacement of smaller, salt-intolerant cladocerans with larger, salt-tolerant ones, significantly impacting freshwater communities and ecosystems. Population levels of cladocerans are more susceptible to salinity stress than individual levels.
The salinization of the global freshwater system caused by various human activities and climate change has become a common problem threatening freshwater biodiversity and resources, which may affect a variety of species of cladocerans at individual and population levels. In order to comprehensively evaluate the impact of salinization on different-sized cladocerans at individual and population levels, we exposed two species of cladocerans with obvious body size difference, Daphnia magna and Moina macrocopa, to seven salinities (0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12 M), recorded individual life history traits and population growth dynamics, and used multiple mechanistic models to fit the data. At the individual level, the median effect concentration of survival time, total offspring per female, and number of broods of D. magna were significantly higher than those of M. macrocopa. At the population level, the decrease in carrying capacity of D. magna with increasing salinity was significantly less than that of M. macrocopa. At the same salinity treatment, the integrated biomarker response indexes value of M. macrocopa is higher than that of D. magna. Therefore, it was further inferred that the sensitivity of small-sized species M. macrocopa to salinity stress is significantly higher than that of big-sized species D. magna. Thus, freshwater salinization may result in the replacement of smaller salt-intolerant cladocerans with larger salt-tolerant cladocerans, which may have dramatic effects on freshwater communities and ecosystems. Additionally, the increase of salinity had a greater impact on the population level of D. magna and M. macrocopa than on the individual level, indicating that population level of cladocerans was more susceptible to salinity stress. Experiments only based on individuals may underestimate the ecologically related changes in populations and communities, thus understanding the impact of salinization on freshwater systems needs to consider multiple ecological levels.
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