Understanding the impact of noise on marine fauna at the population level requires knowledge about the vulnerability of different life-stages. Here we provide the first evidence that noise exposure during larval development produces body malformations in marine invertebrates. Scallop larvae exposed to playbacks of seismic pulses showed significant developmental delays and 46% developed body abnormalities. Similar effects were observed in all independent samples exposed to noise while no malformations were found in the control groups (4881 larvae examined). Malformations appeared in the D-veliger larval phase, perhaps due to the cumulative exposure attained by this stage or to a greater vulnerability of D-veliger to sound-mediated physiological or mechanical stress. Such strong impacts suggest that abnormalities and growth delays may also result from lower sound levels or discrete exposures during the D-stage, increasing the potential for routinely-occurring anthropogenic noise sources to affect recruitment of wild scallop larvae in natural stocks.

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An experiment was conducted to determine if a blindfolded echolocating dolphin modified its biosonar signals depending on the targets it was investigating in a target shape discrimination task. Biosonar signals were measured with a specially designed bite-plate apparatus with a dowel extending from the bite plate to support the hydrophone. The detected signals were digitized and stored on a modified SoundTrap (Ocean Instrument New Zealand) attached to the dowel. The dolphin engaged in a matching-to-sample task: he first examined a sample target and then swam to a different area of the pool to examine three alternative targets, one of which matched the sample. The animal’s task was to point to the matched target. The characteristic of each emitted signal was determined by calculating the peak frequency, center frequency, rms bandwidth, and rms duration. A specific target set was used for each session of 15-18 trials; some sets were unfamiliar to the dolphin. Considerable amount of variations in the signal parameters were observed across trials and sessions, but our statistical analyses suggested the variations were not based on target identity, thereby leading us to conclude that the clicks emitted by the dolphin did not differ with the target set.

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