Decreased feeding rates of the copepod Acartia tonsa when exposed to playback harbor traffic noise

Abstract

IntroductionCopepods present the largest and most diverse group of zooplankton and their feeding behavior can affect top-down and bottom-up processes. Thus, how efficient feeding is executed determines the abundance of copepods’ prey and their predators and, with that, carbon transfer and storage in ecosystems. The rise of anthropogenic underwater noise from shipping, oil exploration and exploitation, wind farm construction and operation, and more, is increasingly changing the marine acoustic environment. This acoustic pollution can have detrimental effects on biological life. Studies on this topic increasingly indicate that anthropogenic underwater noise adversely affects primary producers, marine mammals, fish, and invertebrates. However, little data exist on the effects of anthropogenic underwater noise on the feeding behavior of zooplankton.MethodsHere, we investigated the ingestion and clearance rates of the copepod Acartia tonsa on a motile phytoplankton as a function of prey density under ambient aquarium sound conditions and, when exposed to playback, harbor traffic noise.ResultsWe measured significantly decreased ingestion rates and clearance rates of A. tonsa when exposed to harbor noise compared to ambient conditions. The negative impact of noise on the ingestion rates was found at all given phytoplankton cell densities between 1k to 10k cells ml−1. Clearance rates were fitted to the Rogers random predator equation which revealed significantly decreased capture rates on phytoplankton under the exposure of harbor noise while handling times remained the same in both sound treatments.DiscussionOur results call for follow-up studies to focus on noise driven community-effects in field experiments to confirm laboratory results and to predict the outcome of a changing world with multiple stressors. Further, the underlying mechanism on how noise affects the feeding behavior of copepods is still unknown. Noise may distract copepods or mask hydromechanical cues of the prey. Noise may also adversely affect copepod physiology or morphology that would lead to changes in the feeding behavior. All potential mechanisms need to be investigated rigorously in future experiments.

Chronic broadband noise increases the fitness of a freshwater zooplankton

“…It might be that continuous stimulation of the mechanoreceptors made D. magna less able to perceive their surroundings, resulting in lower mobility. Although we did not assess food intake, D. magna were fed ad libitum so reduced mobility probably did not result in reduced energy input, showed for copepods exposed to noise (Kühn et al, 2023), as it could be in natural populations (Read et al, 2014). Consequently, if we consider that energy input was preserved, then the energy saved from mobility might have been reallocated to tissue maintenance and reproduction, explaining the higher fitness.…”

“…Short-term exposures (less than four days) to air gun (intense acute noise, 150-180 dB SEL Re 1 μPa) result in the mortality of several marine species (McCauley et al, 2017) and negative effects on copepod physiology and development (Fields et al, 2019; Vereide et al, 2023). Short exposures to less intense motorboat noise (i.e., few days exposure at 126 dB RMS Re 1 μPa) do not affect the behaviour of the water flea Daphnia magna (Sabet et al, 2015, 2019; Rojas, Prosnier, et al, 2023) but decrease copepod feeding rate (Kühn et al, 2023) and rotifer fecundity (Aspirault et al, 2023). For short-lived organisms, noise exposure can easily last a substantial part of the lifespan or even exceed it.…”

“…Considering the successive boat passages as a succession of acute stressors, whilst being not exactly the same, nautical activity could be classified as a chronic intermittent stress (Ladewig, 2000). If the impact of noise is dose-dependent (Tyack & Thomas, 2019), for instance through the simulation of mechanoreceptors, then a continuous exposure to noise such as near water catchment systems or in aquatic husbandries could be more impactful than nautical activity (intermittent noise (Prosnier, Rojas, et al, 2023; Vereide et al, 2023)) and one-day exposure (acute noise (Fields et al, 2019; Kühn et al, 2023)). To test this hypothesis, we did a laboratory experiment where we exposed D. magna to continuous broadband noise for their entire life (about one month, from birth to death).…”

No evidence for an effect of chronic boat noise on the fitness of reared water fleas

“…For instance, Gassie et al (1993) found that marine copepods ( Acartia fossae ) can detect water vibrations, and Buskey et al (2002) showed that vibrations can lead to acceleration in individuals of Acartia spp .. Marine zooplankton (e.g., copepods) exposed to acute airguns show a reduction of survival (McCauley et al, 2017; Fields et al, 2019; Vereide et al, 2023). Copepods also show reduced foraging rate during boat noise exposure (Kühn et al, 2023). Chaoborus flavicans larvae, an important predator of zooplankton, show more body rotations, interpreted as an anti-predatory behaviour, when exposed to boat noise for the first time (Rojas et al, 2021).…”

“…Copepods also show reduced foraging rate during boat noise exposure (Kühn et al, 2023). Chaoborus flavicans larvae, an important predator of zooplankton, show more body rotations, interpreted as an anti-predatory behaviour, when exposed to boat noise for the first time (Rojas et al, 2021).…”