Acute toxicity of glyphosate on various life stages of calanoid copepod, Pseudodiaptomus annandalei

Abstract

Copepods are one of the most important primary producers and biodiversity indicators. They are also highly susceptible to various toxicants. In this study, glyphosate (Roundup®), a widely used herbicide was used to investigate the toxicity effect on calanoid copepods, Pseudodiaptomus annandalei, focused on their nauplius, copepodid, and adult stages. Different concentrations of glyphosate (i.e. 0 - as control, 0.05, 0.1, 0.4, 1.6, 6.4 and 25.6 mg/L) were used to elucidate the tolerance level of P. annandalei. The survival rate of copepod was recorded at the intervals of 24, 48, 72 and 96 h after glyphosate exposure. The analysis was performed using probit test to determine the sub-lethal concentrations. Our results revealed that LC50 of the nauplius stage was recorded as 3.47, 3.02, 1.86 and 1.10 mg/L at 24, 48, 72 and 96 h, respectively. Higher LC50 values were recorded at 4.36 mg/L for 24 h, 3.09 mg/L for 48 h, 2.00 mg/L for 72 h, and 1.12 mg/L for 96 h at the copepodid stage. Generally, adult copepods showed a higher level of tolerance to glyphosate among all stages, whereby at this stage LC50 values were recorded as 11.70 mg/L for 24 h,10.23 mg/L for 48 h, 7.41 mg/L for 72 h, and 3.61 mg/L for 96 h, respectively. Our results indicated that prolong exposure time of glyphosate could increase the susceptibility of P. annandalei to the herbicide. Nauplii are the most sensitive group among all. This study showed that glyphosate could post significant eco-toxicological impact to the non-targeted organism.