Anthropogenic chemical cues can alter the swimming behaviour of juvenile stages of a temperate fish

UV filter occurrence in beach water of the Mediterranean coast - A field survey over 2 years in Palavas-les-Flots, France

OBJECTIVE

A 2-year sampling campaign was realized on French Mediterranean beach (Palavas-les-Flots Hérault) in order to measure the concentration of UV filters released from the sunscreen used by bathers. Multiple factors suspected of playing determining roles in the UV filter pattern in water were explored, such as the seasonal and daily time evolutions, or the vertical and horizontal distributions, and they were regarded through the UV filter characteristics.

METHODS

The beach was monitored during periods of high and low tourist attendance, typically before, during and after the summer peak. The beachgoers attendance was counted. Bathing water was sampled distinctly from the bulk column and from the top surface layer, testing different sampling tools. Sediments and mussels were also sampled and analysed as potential UV filter sinks. Three organic UV filters (octocrylene OCR, avobenzone BMDBM and octyl methoxycinnamate OMC) and one mineral (titanium dioxide TiO2 ) were studied here as representatives of the current cosmetic market.

RESULTS

Summer peak attendance on the beach was confirmed associated with peak levels of UV filter concentration in the bathing water, even more pronounced during a heat wave period. This relation was also observed at day scale with an afternoon peak, suggesting a rapid evolution of the UV filter pattern in water. Contrasted fates were measured between the four studied UV filters, that could be mainly explained by their respective characteristics, i.e. particulate or dissolved, hydrophilic or lipophilic, lifetime. Generally, this resulted in a concentration ranking TiO2  > OCR > OMC > BMDBM, ranging from 0.5 to 500 μg/L. The most lipophilic and recalcitrant OCR was found most vertically differentiated and over concentrated in the top surface layer of water. Finally, a large horizontal heterogeneity was also observed in the UV filter concentration pattern, raising the need for sample replicates that cover a significant area.

CONCLUSION

This work fulfils some knowledge gaps on the issue of UV filter release in coastal environments, not only by providing original field data and methodological recommendations but also importantly in the comparison made of organic and mineral UV filters, which are often considered separately and rarely evaluated at the same time.

Avoidance behaviour and toxicological impact of sunscreens in the teleost Chelon auratus

There is increasing evidence that sunscreen, more specifically the organic ultra-violet filters (O-UVFs), are toxic for aquatic organisms. In the present study, we simulated an environmental sunscreen exposure on the teleost fish, Chelon auratus. The first objective was to assess their spatial avoidance of environmental concentrations of sunscreen products (i.e. a few μg.L-1 of O-UVFs). Our results showed that the fish did not avoid the contaminated area. Therefore, the second objective was to evaluate the toxicological impacts of such pollutants after 35 days exposure to concentrations of a few μg.L-1 of O-UVFs. At the individual level, O-UVFs increased the hepatosomatic index which could suggest pathological alterations of the liver or the initiation of the detoxification processes. At the cellular level, a significant increase of malondialdehyde was measured in the muscle of fish exposed to O-UVFs which suggests a failure of antioxidant defences and/or an excess of reactive oxygen species.

Effects of oxybenzone on zebrafish behavior and cognition

The increased ultraviolet (UV) radiation on the Earth's surface increased the need for UV filters products. One of the most used is oxybenzone, which is indiscriminately released in the environment. Oxybenzone's ecotoxicological effects on physiology have been investigated because of the bioaccumulation and action as an endocrine disruptor. However, little is known about its effects on behavior or cognition. In this study, we approach the effects of short-term oxybenzone exposure on locomotion, anxiety-like, social behavior, and short-term memory in zebrafish (Danio rerio). Adult zebrafish were exposed to oxybenzone 10, 100 and 1000 μg L^-1 for 15 days and then tested (novel tank, shoal preference, mirror test, and T-maze with novelty). Fish exposed to oxybenzone showed reduced locomotion, decreased anxiety-like behavior, less time near/interacting with the shoal, fewer interactions with the mirror image, and decreased exploration of the novel arm in the T-maze test. These results suggest that oxybenzone affects perception, increases risk-taking, impairs proper aggressive response, and jeopardizes the animals' ability to retain information. These results reinforce the risk posed by products discarded into the aquatic ecosystems, especially those with underestimated toxic potential.

Swimming Activity of Gilthead Seabream (Sparus aurata) in Swim-Tunnels: Accelerations, Oxygen Consumption and Body Motion

Acoustic transmitters equipped with accelerometer sensors are considered a useful tool to study swimming activity, including energetics and movement patterns, of fish species in aquaculture and in nature. However, given the novelty of this technique, further laboratory-derived calibrations are needed to assess the characteristics and settings of accelerometer acoustic transmitters for different species and specific environmental conditions. In this study, we compared accelerometer acoustic transmitter outputs with swimming performance and body motion of gilthead seabream (Sparus aurata L.) in swim-tunnels at different flow speeds, which allowed us to characterize the swimming activity of this fish species of high aquaculture interest. Tag implantation in the abdominal cavity had no significant effects on swimming performance and body motion parameters. Accelerations, cost of transport and variations on head orientation (angle with respect to flow direction) were negatively related to flow speed in the tunnel, whereas oxygen consumption and frequencies of tail-beat and head movements increased with flow speed. These results show that accelerometer acoustic transmitters mainly recorded deviations from sustained swimming in the tunnel, due to spontaneous and explorative swimming at the lowest speeds or intermittent burst and coast actions to cope with water flow. In conclusion, accelerometer acoustic transmitters applied in this study provided a proxy for unsustained swimming activity, but did not contemplate the high-energy cost spent by gilthead seabream on sustained swimming, and therefore, it did not provide a proxy for general activity. Despite this limitation, accelerometer acoustic transmitters provide valuable insight in swim patterns and therefore may be a good strategy for advancing our understanding of fish swimming behavior in aquaculture, allowing for rapid detection of changes in species-specific behavioral patterns considered indicators of fish welfare status, and assisting in the refinement of best management practices.

Fipronil and 2,4-D effects on tropical fish: Could avoidance response be explained by changes in swimming behavior and neurotransmission impairments?

Brazil is the largest producer of sugarcane, a crop largely dependent on chemical control for its maintenance. The insecticide fipronil and herbicide 2,4-D stand out among the most commonly used pesticides and, therefore, environmental consequences are a matter of concern. The present study aimed to investigate the toxicity mechanisms of Regent® 800 WG (a.i. fipronil) and DMA® 806 BR (a.i. 2,4-D) pesticides using forced and non-forced exposures through an integrative approach: firstly, to assess whether contamination by fipronil and 2,4-D can trigger the avoidance behavior of the fish Danio rerio (zebrafish) and Hyphessobrycon eques (serpae tetra or mato-grosso). Additionally, the effects on fish were analyzed considering the swimming behavior together with a biomarker of neurotoxicity, the activity of acetylcholinesterase (AChE). In avoidance tests with pesticide gradients, D. rerio avoided the highest concentrations of the two compounds and H. eques avoided only the highest concentration of 2,4-D. The swimming behavior (distance moved) was reduced and AChE was inhibited when D. rerio was exposed to fipronil. The 2,4-D affected the swimming (maximum speed) of H. eques, but AChE was not altered. Avoidance response seemed not to have been affected by possible effects of contaminants on swimming behavior and Ache activity. This study showed the importance of knowing the avoidance capacity, swimming behavior and neurotoxic effects of pesticides on fish in an integrated and realistic context of exposure in environments contaminated with pesticides and can be useful as ecologically relevant tools for ecological risk assessment.

Not Only Toxic but Repellent: What Can Organisms' Responses Tell Us about Contamination and What Are the Ecological Consequences When They Flee from an Environment?

The ability of aquatic organisms to sense the surrounding environment chemically and interpret such signals correctly is crucial for their ecological niche and survival. Although it is an oversimplification of the ecological interactions, we could consider that a significant part of the decisions taken by organisms are, to some extent, chemically driven. Accordingly, chemical contamination might interfere in the way organisms behave and interact with the environment. Just as any environmental factor, contamination can make a habitat less attractive or even unsuitable to accommodate life, conditioning to some degree the decision of organisms to stay in, or move from, an ecosystem. If we consider that contamination is not always spatially homogeneous and that many organisms can avoid it, the ability of contaminants to repel organisms should also be of concern. Thus, in this critical review, we have discussed the dual role of contamination: toxicity (disruption of the physiological and behavioral homeostasis) vs. repellency (contamination-driven changes in spatial distribution/habitat selection). The discussion is centered on methodologies (forced exposure against non-forced multi-compartmented exposure systems) and conceptual improvements (individual stress due to the toxic effects caused by a continuous exposure against contamination-driven spatial distribution). Finally, we propose an approach in which Stress and Landscape Ecology could be integrated with each other to improve our understanding of the threat contaminants represent to aquatic ecosystems.

Repellency and mortality effects of sunscreens on the shrimp Palaemon varians: Toxicity dependent on exposure method

Contamination by sunscreens has become a serious environmental problem due to the increasing use of these products in coastal regions. Their complex chemical composition supposes an input of different chemical compounds capable of producing toxic effects and repelling organisms. The aim of the current study was to experimentally check the repellency of three commercial sunscreens [A (lotion), B (gel) and C (milk spray)] by assessing the escape (displacement towards areas with lower sunscreen levels) of the estuarine shrimp Palaemon varians exposed (4 h) to a gradient (0-300 mg/L) of the sunscreens in a heterogeneous non-forced exposure scenario. Additionally, mortality and immobility (72 h) were checked in a traditional forced exposure scenario. Considering that the toxicity of sunscreens is a little controversial regarding their chemical availability in the medium, two different methods of sunscreen solubilisation were tested: complete homogenization and direct immersion. Very low mortality was observed in the highest concentration of sunscreens A and C applied by direct immersion; however, for sunscreen B, the main effect was the loss of motility when homogenization was applied. Repellency was evidenced for two sunscreens (A and B) applied by direct immersion. The homogenization in the medium seemed to lower the degree of repellency of the sunscreens, probably linked to the higher viscosity in the medium, preventing the motility of shrimps. By integrating both short-term responses (avoidance and mortality/immobility), the PID (population immediate decline) calculated showed that avoidance might be the main factor responsible for the reduction of the population at the local scale.

Does the previous exposure to copper alter the pattern of avoidance by zebrafish in a copper gradient scenario? Hypothesis of time-delayed avoidance due to pre-acclimation

The traditional ecotoxicity assays (forced exposure) tend to use organisms that are cultured under controlled conditions or that come from undisturbed ecosystems, with no (or negligible) previous contact with contamination. The same occurs in the non-forced approach, in which organisms are exposed to a contamination gradient and can move between different concentrations choosing the less toxic one. Considering that organisms inhabiting contaminated ecosystems tend to be gradually exposed to contamination, an abrupt exposure from uncontaminated conditions to a contaminated environment might present two problems: lack of ecological relevance to a scenario where the contamination occurs gradually and a magnification of the toxicity due to the sudden change in the environmental conditions. Therefore, a key question should be addressed: might a previous exposure to contamination reduce the organisms' perception of the danger of a contaminant (hypothesis of time-delayed avoidance due to pre-acclimation-TDADP), altering their avoidance response pattern? We tested the avoidance of zebrafish (Danio rerio: ±2 months old) populations when exposed to a copper gradient (0-400 μg/L). The populations differed according to the period (24 h and 7 and 30 days) in which they were acclimated to copper (ca. 400 μg/L). The avoidance in the 2 h experiments changed as a consequence of the acclimation period. In the population that was not previously acclimated, 40% of the fish moved to the less contaminated compartment and only 6.7% stayed in the most contaminated one; for the other populations those values were, respectively, 31 and 11% (24 h-acclimation), 28 and 26% (7 day-acclimation) and 19 and 27% (30 day-acclimation). An abrupt exposure to a contaminant might overestimate the response if this is analyzed in the short-term. When the avoidance tests were prolonged to 24 h, the avoidance tended to reach similar values to those of the non-acclimated population, thus supporting our TDADP hypothesis.

Massive coastal tourism influx to the Mediterranean Sea: The environmental risk of sunscreens

The Mediterranean region is, by far, the leading tourism destination in the world, receiving more than 330 million tourists in 2016. This tourism is undertaken mostly for seaside holidays, and during the summer season concentrates between 46% and 69% of the total international arrivals; this is equivalent to a density of 2.9 tourists per meter of Mediterranean coast, or double this number taking into account the local/permanent population in addition. Previous studies have reported not only the presence of sunscreen in the various environmental compartments (water, sediments and biota) of the Mediterranean Sea (MS) and other regions, but also show that sunscreen products are toxic for marine biota and are accumulated and biomagnificated. Here, we highlight that the environmental risk of these chemicals is likely to be exacerbated in the MS due to the massive influx of tourists and its densely populated coasts, the basin's limited exchanges with the ocean, the high residence time of surface waters, and its oligotrophic waters.

Density differences between water masses preclude laminar flow in two-current choice flumes

Two-current choice flumes are used to measure preference and avoidance behaviour in response to chemical cues in aquatic animals. If used correctly, they produce two parallel, non-overlapping, laminar water currents in which the animal can move freely and choose between the two currents. As climate change is affecting water temperature, and altered precipitation patterns are changing water salinity, two-current choice flumes are increasingly being used to test the choice between water currents of different temperatures and salinities. This inevitably means that water currents of different densities are being used simultaneously in the flume. Here, we investigated the tolerance range for density differences due to temperature and salinity in five common flume designs. Through dye tests and stepwise modifications of temperatures and salinities we determined the limits for laminar and non-overlapping flows. We also developed an automated method for quantifying the overlap precisely and objectively. The tolerance for density differences between the water currents where laminar and non-overlapping flows were maintained was surprisingly low, withstanding  ± 0.5 °C temperature differences, and ± 0.1 PSU salinity differences, i.e. a maximum density difference of 0.28 gL^-1. Above these very narrow limits we found a range where the flumes showed partly overlapping, stratified water currents that preclude easy determination of cue preference. We conclude that two-current choice flumes are not suitable for testing the behavioural choices of aquatic animals using water currents of anything other than minor differences in temperature and/or salinity.

Spatial avoidance as a response to contamination by aquatic organisms in nonforced, multicompartmented exposure systems: A complementary approach to the behavioral response

The idea that the hazard of contaminants is exclusively related to their toxic effects does not consider the fact that some organisms can avoid contamination, preventing toxicity. Although inferences about avoidance are made in most behavioral ecotoxicology studies, assessment of the real spatial displacement (organisms moving toward another habitat to escape contamination) is difficult due to the type of exposure (confined and mandatory) used in the bioassays: a forced exposure approach. A complementary approach using nonforced exposure systems to assess how contaminants affect the spatial distribution of organisms in a bicompartmented (toxic or nontoxic) environment has long been described. Recently, this nonforced approach has been developed to include a multi compartmented system in which different samples can be simultaneously tested. The aim of the present review was to describe the importance of the nonforced, multicompartmented exposure approach to simulate a gradient or patches of contamination, to describe the 2 main exposure systems, and to highlight the ecological relevance of including spatial avoidance and habitat preference in ecotoxicological studies. The multicompartmentalization of the system makes it possible to simulate more complex scenarios and therefore include new ecological concepts in bioassays. We also contrasted spatial avoidance in the nonforced exposure systems with the behavioral endpoints measured under other exposure systems. Finally, we showed that the nonforced, multicompartmented exposure approach makes it possible 1) to improve environmental risk assessments by adding the dispersion pattern of organisms in a multihabitat scenario, and 2) to integrate ecological concepts such as recolonization of recovering habitats, loss of habitat connectivity, habitat fragmentation, and contamination-driven metapopulation, which have received limited attention in ecotoxicological studies. Environ Toxicol Chem 2019;38:312-320. © 2018 SETAC.