Co-exposure to UV radiation and crude oil increases acute embryotoxicity and sublethal malformations in the early life stages of Atlantic haddock (Melanogrammus aeglefinus).

Crude oil causes severe abnormalities in developing fish. Photomodification of constituents in crude oil increases its toxicity several fold. We report on the effect of crude oil, in combination with ultraviolet (UV) radiation, on Atlantic haddock (Melanogrammus aeglefinus) embryos. Accumulation of crude oil on the eggshell makes haddock embryos particularly susceptible to exposure. At high latitudes, they can be exposed to UV radiation many hours a day. Haddock embryos were exposed to crude oil (5-300 µg oil/L nominal loading concentrations) for three days in the presence and absence of UV radiation (290-400 nm). UV radiation partly degraded the eggs' outer membrane resulting in less accumulation of oil droplets in the treatment with highest oil concentration (300 µg oil/L). The co-exposure treatments resulted in acute toxicity, manifested by massive tissue necrosis and subsequent mortality, reducing LC50 at hatching stage by 60 % to 0.24 µg totPAH/L compared to 0.62 µg totPAH/L in crude oil only. In the treatment with nominal low oil concentrations (5-30 µg oil/L), only co-exposure to UV led to sublethal morphological heart defects. Including phototoxicity as a parameter in risk assessments of accidental oil spills is recommended.

Effects of Exposure to Low Concentrations of Oil on the Expression of Cytochrome P4501a and Routine Swimming Speed of Atlantic Haddock (Melanogrammus aeglefinus) Larvae In Situ.

Exposure to environmentally relevant concentrations of oil could impact survival of fish larvae in situ through subtle effects on larval behavior. During the larval period, Atlantic haddock (Melanogrammus aeglefinus) are transported toward nursery grounds by ocean currents and active swimming, which can modify their drift route. Haddock larvae are sensitive to dispersed oil; however, whether exposure to oil during development impacts the ability of haddock larvae to swim in situ is unknown. Here, we exposed Atlantic haddock embryos to 10 and 80 µg oil/L (0.1 and 0.8 µg ∑PAH/L) of crude oil for 8 days and used a novel approach to measure its effect on the larval swimming behavior in situ. We assessed the swimming behavior of 138 haddock larvae in situ, in the North Sea, using a transparent drifting chamber. Expression of cytochrome P4501a (cyp1a) was also measured. Exposure to 10 and 80 µg oil/L significantly reduced the average in situ routine swimming speed by 30-40% compared to the controls. Expression of cyp1a was significantly higher in both exposed groups. This study reports key information for improving oil spill risk assessment models and presents a novel approach to study sublethal effects of pollutants on fish larvae in situ.

Impact of magnetic fields generated by AC/DC submarine power cables on the behavior of juvenile European lobster (Homarus gammarus).

The number of submarine power cables using either direct or alternating current is expected to increase drastically in coming decades. Data concerning the impact of magnetic fields generated by these cables on marine invertebrates are scarce. In this context, the aim of this study was to explore the potential impact of anthropogenic static and time-varying magnetic fields on the behavior of recently settled juvenile European lobsters (Homarus gammarus) using two different behavioral assays. Day-light conditions were used to stimulate the sheltering behavior and facilitate the video tracking. We showed that juvenile lobsters did not exhibit any change of behavior when submitted to an artificial magnetic field gradient (maximum intensity of 200 µT) compared to non-exposed lobsters in the ambient magnetic field. Additionally, no influence was noted on either the lobsters' ability to find shelter or modified their exploratory behavior after one week of exposure to anthropogenic magnetic fields (225 ±â€¯5 µT) which remained similar to those observed in control individuals. It appears that static and time-varying anthropogenic magnetic fields, at these intensities, do not significantly impact the behavior of juvenile European lobsters in daylight conditions. Nevertheless, to form a complete picture for this biological model, further studies are needed on the other life stages as they may respond differently.

Exposure to teflubenzuron negatively impacts exploratory behavior, learning and activity of juvenile European lobster (Homarus gammarus).

Infestations with salmon lice, a parasitic copepod, is a major problem in the salmon farming industry. Teflubenzuron is an in-feed pharmaceutical applied to control lice outbreaks; the standard medication is 10 mg per kg fish per day for seven days. Surveys reveal that teflubenzuron accumulates and persists in the sediment around fish farms and causes deformities and mortality in juvenile European lobster (Homarus gammarus), a species commonly found in the vicinity of salmon farms in Norway. To date, there is no information on sub-lethal effects of teflubenzuron on, for example, behavior. We conducted an experiment to assess possible difference in the shelter seeking behavior of teflubenzuron-exposed (N = 19) vs. not exposed (N = 19) H. gammarus juveniles. The teflubenzuron-exposed juveniles had been given very low concentrations, 1.7 µg per pellet twice per week for 113 days prior to this experiment. The concentration of teflubenzuron was estimated to be less than 1 ng/g lobster when they were tested in the behavior experiment. Animals were placed in a lane with a shelter at one end. Once a lobster had found and entered the shelter, they were repeatedly displaced back to the opposite end of the lane, for a total of 3 repeated runs per animal. Three of the exposed juveniles failed to settle in the shelter, and the remaining teflubenzuron-exposed animals took significantly more time to explore the environment and to find and recognize shelter. Furthermore, exposed lobsters also exhibited slower walking speed compared to the controls. These results demonstrate that teflubenzuron significantly reduces exploratory behavior, learning and activity of juvenile H. gammarus. Thus, exposure to teflubenzuron could increase predation mortality of juvenile lobsters in the wild.

Effect of sub-lethal exposure to ultraviolet radiation on the escape performance of Atlantic cod larvae (Gadus morhua).

UNLABELLED: The amount of ultraviolet (UV) radiation reaching the earth's surface has increased due to depletion of the ozone layer. Several studies have reported that UV radiation reduces survival of fish larvae. However, indirect and sub-lethal impacts of UV radiation on fish behavior have been given little consideration. We observed the escape performance of larval cod (24 dph, SL: 7.6±0.2 mm; 29 dph, SL: 8.2±0.3 mm) that had been exposed to sub-lethal levels of UV radiation vs. unexposed controls. Two predators were used (in separate experiments): two-spotted goby (Gobiusculus flavescens; a suction predator) and lion's mane jellyfish (Cyanea capillata; a "passive" ambush predator). Ten cod larvae were observed in the presence of a predator for 20 minutes using a digital video camera. Trials were replicated 4 times for goby and 5 times for jellyfish. Escape rate (total number of escapes/total number of attacks ×100), escape distance and the number of larvae remaining at the end of the experiment were measured. In the experiment with gobies, in the UV-treated larvae, both escape rate and escape distance (36%, 38±7.5 mm respectively) were significantly lower than those of control larvae (75%, 69±4.7 mm respectively). There was a significant difference in survival as well (UV: 35%, CONTROL: 63%). No apparent escape response was observed, and survival rate was not significantly different, between treatments (UV: 66%, CONTROL: 74%) in the experiment with jellyfish. We conclude that the effect and impact of exposure to sub-lethal levels of UV radiation on the escape performance of cod larvae depends on the type of predator. Our results also suggest that prediction of UV impacts on fish larvae based only on direct effects are underestimations.