## 3 Results
### A.Ionsa Testing and Evaluation  
For the copep cultures, parameters such as temperature, pH, oxygen, and salinity were also periodically monitored (Figure S9). The pH ranged from 7.37 to 7.69, and the salinity varied from 14.75 PSU to 15.83 PSU. The test organisms were cultured at a similar salinity (\(\pm\)3 PSU) for at least 7 days before the test, maintaining salinity levels between 14.75 PSU and 15.83 PSU. The light intensity was measured in five points (Figure S9), with values between 1259 and 2200 lux, and was constant throughout the experiment, falling within the protocol's stipulated range of up to 2200 lux. The box plot illustrates mortality trends across different toxicant concentrations, showing a stronger response at 48 h, with significant differences confirmed by the Kruskal-Wallis test and \(p\)-values \(<0.05\) for both time points, emphasizing the significant differences between the toxicant's dose- and time-dependent impact (Figure 2). In the control group, copep mortality remains consistently low over 24 and 48 h. At lower concentrations of 3,5-dichlorophenol (0.1 mg/L and 0.32 mg/L), mortality gradually rises, with minor time-dependent variations. At an intermediate concentration (1 mg/L), mortality increasesmore notably, particularly after 48 h, indicating a potential delayed or accumulative effect. At higher concentrations (3.2 mg/L and 10 mg/L), mortality reaches its maximum within both time frames (Figure 2). In the control group C (0.0), mortality is low, indicating that environmental factors likely did not cause significant death and validating the experiment (Figure 3). As the concentration increases, mortality gradually rises, with more pronounced effects at 48 h, suggesting time-dependent toxicity. At higher concentrations (3.2 and 10 mg/L), mortality reaches 100%, indicating that these concentrations are lethal to copepods within 24 h. (Figure 3). The error bars (SEM) reflect variability in the data, showing that while some variation exists, the trends are consistent and indicate dose-dependent mortality (Figure 3). This suggests that the substance is toxic to copepods in a concentration- and time-dependent manner. The LC50 graph illustrates the dose-response relationship for the reference toxicant affecting _A. tonsa_ (Figure 4). At very low concentrations (around 0.01 mg/L), the effect is minimal, below 20%, and as the concentration increases, particularly between 0.1 mg/L and 1 mg/L, the effect rises noticeably, reaching near maximal levels (close to 100%)  
Figure 3: Mean cumulative percent mortality of copepods with standard error of the mean (SEM). Figure 2: Box plot of copepods mortality per reference toxicant concentration and time exposure. around 10 mg/L. The LC50, where 50% of the maximal effect is observed, is 1.15 mg/L (Table 2). This graph demonstrates that low doses have minimal effects, moderate doses show increasing effects, and high doses achieve maximum effect  
Increasing concentrations of the toxicant result in progressively greater effects over time. The highest concentration (10 mg/L) caused maximal effect at 24 h, while lower concentrations show milder effects, with some increasing over time (e.g., 1 mg/L). The control group, as expected, shows a negligible effect (Figure 5). \begin{table}
\begin{tabular}{l c c} \hline \hline \multirow{2}{*}{**Species**} & \multicolumn{2}{c}{**3,5-dichlorophenol**} \\ \cline{2-3}  & **48 h LC50 (mg/L)** & **Concentration (mg/L) for 20\% to** \\  & **80\% Mortality** \\ \hline _Acartia tousa_—ISO [33] & 0.5–1.5 & 1.0 \\ \hline _Acartia tousa_—test value & 1.15 & 1.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Endpoint—48-h LC50. Figure 4: LC50 for the effect of reference toxicant (3,5-dichlorophenol) on _Acartia tousa_ (red square—LC50). Figure 5: Effect (%) of reference toxicant concentrations. Concentrations of 3.2 mg/L and 10 mg/L exhibited high effects across both time points (24 h and 48 h) showing a significant effect, with colors moving towards black, indicating 100% effect (Figure 6).