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Simple Summary: This study is the first to assess the presence of micro-litter ingested by four species of marine mammals and two species of sea turtles, found stranded along the coastline of Samos Island, north-eastern Aegean Sea, Greece. Litter particles, identified as microplastics, were ubiquitous throughout all the digestive tracts analysed. This study suggests there is widespread microplastic contamination in marine megafauna in the study area, and proposes a method of standardisation to facilitate comparisons. This study is the first to assess the occurrence of micro-litter ingested by marine megafauna in the north-eastern Aegean Sea. A total of 25 specimens from four species of marine mammals, including dolphins and monk seals, and two species of sea turtles, found stranded along the coastline of Samos Island, Greece, were selected for the analysis. Litter particles, identified as microplastics (MPs), were ubiquitous throughout all sections of the gastrointestinal tract (oesophagus, stomach and intestine) in all specimens. Overall, the MPs most frequently found were black fibres 0.21–0.50 mm in size. These results provide insight into the extent of micro-litter ingestion and contamination in marine vertebrates. Here we propose a method of standardisation to establish a baseline for marine taxa in this region of the Mediterranean Sea, where knowledge of the topic is still lacking. [ABSTRACT FROM AUTHOR]

In the presence of vessels, dolphins have been found to change their habitat, behavior, group composition and whistle repertoire. The modification of the whistle parameters is generally considered to be a response to the engine noise. Little is known about the impact of the physical presence of vessels on dolphin acoustics. Whistle parameters of the coastal and oceanic ecotypes of common bottlenose dolphins in La Paz Bay, Mexico, were measured after the approach of the research vessel and its engine shutdown. Recordings of 10 min were made immediately after turning off the engine. For analysis, these recordings were divided from minute 0 to minute 5, and from minute 5:01 to minute 10. The whistles of the oceanic ecotype showed higher maximum, minimum and peak frequency in the second time interval compared to the first one. The whistle rate decreased in the second time interval. The whistles of the coastal ecotype showed no difference between the two time intervals. The physical presence of the research vessel could have induced a change in the whistle parameters of the oceanic dolphins until habituation to the vessel disturbance. The oceanic ecotype could increase the whistle rate and decrease the whistle frequencies to maintain acoustic contact more frequently and for longer distances. The coastal ecotype, showing no significant changes in the whistle parameters, could be more habituated to the presence of vessels and display a higher tolerance. [ABSTRACT FROM AUTHOR]

Vessel traffic is one of the major sources of underwater anthropogenic noise. Dolphins can modify their vocal repertoire, especially whistles, in presence of vessels to facilitate their communication. Acoustic data were collected (sampling rate 96 kHz) in La Paz Bay, Gulf of California, Mexico. Whistle rate and parameters of the coastal and oceanic ecotypes of common bottlenose dolphins (Tursiops truncatus) were measured in absence of vessels and in presence of moving small vessels (size 5–10 m). The peak noise difference was calculated between the two frequency bands dominated by the whistles (2000–20,000 Hz) and the small vessel (500–2000 Hz). In presence of vessels the oceanic ecotype decreased whistle frequencies while the coastal ecotype increased them. Both ecotypes raised whistle frequencies with the decreasing of the peak noise difference. The differences in habitat and group structure could have driven the two ecotypes to react in a different way to the vessel presence. [ABSTRACT FROM AUTHOR]