DOI: 10.5061/dryad.0zpc8676j
title: Are brackish water copepods susceptible to neonicotinoid pesticides? An experimental assessment across different salinity levels

description: Zooplankton are key organisms in aquatic food webs, but due to
 spatiotemporal salinity fluctuations, estuarine and brackish lakes support
 only a limited number of zooplankton species. The susceptibility of
 zooplankton to pesticide contamination, such as imidacloprid, is
 particularly important in these ecosystems, because there are fewer
 species to compensate for losses. However, whether zooplankton in brackish
 water are truly vulnerable to pesticide contamination is poorly examined.
 To address this uncertainty, we assessed the vulnerability of the calanoid
 copepod Sinocalanus tenellus, a dominant zooplankton in the brackish
 waters of East Asia, to imidacloprid under varying salinity conditions
 through individual and population-level experiments. The individual-level
 experiment revealed that both imidacloprid exposure and salinity changes
 had significant negative effects on the survival rate of S. tenellus.
 However, hazard assessments indicated that the risk posed by salinity
 changes was much greater than that posed by imidacloprid when pesticide
 concentrations were within ranges typically observed in natural habitats.
 In the population experiment, imidacloprid exposure had no significant
 effects on any ontogenetic stages, whereas even small salinity changes
 significantly affected juveniles of this species. These findings suggest
 that imidacloprid exposure has a much smaller impact on S. tenellus than
 salinity changes, except when imidacloprid contamination levels are higher
 than those typically found in nature. To accurately assess pesticide
 toxicity in brackish water ecosystems, environmental factors such as
 salinity must be considered as potential background influences.
description: # Are brackish water copepods susceptible to neonicotinoid pesticides? An
 experimental assessment across different salinity levels
 [https://doi.org/10.5061/dryad.0zpc8676j](https://doi.org/10.5061/dryad.0zpc8676j) ## Description of the data and file structure ### Files and variables #### File: Acute_toxicity.csv **Description:** Data set used for performing the Cox proportional hazards model and illustrating the Kaplan-Meier survival curves. ##### Variables * res: Mortality status of test organisms observed at each time point, where 1 means dead and 0 means alive. * con: Nominal concentration of imidacloprid in each experimental treatment (μg/L). * time: Elapsed time since the experiment started (hours). * salinity: Salinity of experimental water in each treatment (PSU). * sal_avr: Average salinity of the three sites (Lake Suigetsu, Lake Shinji, and Higashiyachi) * site: Sampling sites * sal_dev: Difference between experimental water salinity in each treatment (salinity) and average salinity at three sampling sites (sal_avr). #### File: community_bar.csv **Description:** Data set of the population experiment to visualize the abundance of each ontogenetic stage. ##### Variables * treatment: 12 experimental treatments (four imidacloprid concentration levels* three salinity levels) and initial condition. All treatments were triplicated. * abundance: Number of individuals for each ontogenetic stage at the beginning (for initial) and end (for other treatments) of the experiment (individuals). * stage: Ontogenetic stage of the test organism. #### File: community_lm.csv **Description:** Data set used for linear regression analysis for population experiment. ##### Variables * salinity: Salinity of experimental water in each treatment (PSU). * sal_sq: Square of the difference between the salinity at the sampling site (Higashiyachi: 7.9 PSU) and the experimental water salinity for each treatment. * pesticide: Nominal concentration of imidacloprid in each experimental treatment (μg/L). * abundance: Number of individuals of the test organism at the end of the experiment (individuals). * stage: Ontogenetic stage of the test organism. #### File: community_sem.csv **Description:** Data set used for path analysis of population experiment. ##### Variables * adult: Log (n+1)-transformed abundance of adult at the end of the experiment. * copepodid: Log (n+1)-transformed abundance of copepod stage at the end of the experiment. * nauplius: Log (n+1)-transformed abundance of nauplius stage at the end of the experiment. * log10_pes: Log10 (n+1)-transformed concentration of imidacloprid in each experimental treatment (μg/L). * sal_sq: Square of the difference between the salinity at the sampling site (Higashiyachi: 7.9 PSU) and the experimental water salinity for each treatment.