Changes in the swimming behavior of Temora turbinata (Copepoda, Calanoida) in response to sub-lethal concentrations of caffeine and triclosan

Abstract

Caffeine (CAF) and triclosan (TCS) are contaminants of emerging environmental concern due to their widespread presence in marine environments and their potential biological effects on non-target organisms. Despite growing efforts to assess the toxicity of CAF and TCS in aquatic organisms, knowledge of their impacts on marine zooplankton remains limited, particularly regarding physiological aspects such as swimming behavior, a key component of copepod ecology. As the most abundant group of zooplankton, copepods play a crucial role in pelagic food webs and biogeochemical carbon cycles. This study presents findings from microcosm experiments designed to evaluate the immediate effects of two sub-lethal concentrations of CAF and TCS on the three-dimensional swimming behavior of the marine calanoid copepod Temora turbinata. Using 3D horizontal optical system, we analyzed the displacement patterns and swimming speeds of adult T. turbinata individuals before, during, and after exposure to 50 µg L⁻¹ and 100 µg L⁻¹ concentrations of CAF and TCS. Results indicate that both CAF and TCS immediately affect copepod free-swimming behavior, with CAF exposure inducing hyperactivity and TCS exposure leading to hypoactivity. By addressing knowledge gaps concerning the effects of emerging contaminants on marine zooplankton, this study supports the use of copepod kinematics as a sensitive indicator of short-term responses to sub-lethal chemical exposure, providing a predictive tool for assessing contaminant effects on planktonic communities.