Microstructural and compositional variation in pacu and piranha teeth related to diet specialization (Teleostei: Serrasalmidae).

In any vertebrate group, tooth shape is known to fit with a biological function related to diet. However, little is known about the relationships between diet and tooth microstructure and composition in teleost fishes. In this work, we describe the external morphology, internal microstructure and elemental composition of the oral teeth of three representative species of the family Serrasalmidae having different feeding habits (herbivorous vs. omnivorous vs. carnivorous). We used backscattered-electron imaging and low vacuum environmental scanning electron microscope to compare the organization and mineralization of tooth layers as well as energy dispersive X-ray microanalysis and Raman microspectrometry to investigate the elemental composition, Ca/P ratio and mineralogy of the most superficial layers. Oral teeth of each serrasalmid species have the same internal organization based on five distinctive layers (i.e. pulp, dentine, inner enameloid, outer enameloid and cuticle) but the general tooth morphology is different according to diet. Microstructural and compositional variation of the cuticle and iron-enrichment of superficial layers were highlighted between herbivorous and carnivorous species. Iron is more concentrated in teeth of the herbivorous species where it is associated with a thicker cuticle explaining the more intense red-pigmentation of the cutting edges of oral teeth. The iron-enrichment is interpreted as a substitution of Ca by Fe in the hydroxyapatite. These traits are discussed in the light of the evolutionary history of the family. Further considerations and hypotheses about the formation and origin of the mineralized tooth layers and especially the iron-rich superficial layers in teleost fishes are suggested.

Evaluation of meso- and microplastic ingestion by the northern fulmar through a non-lethal sampling method.

An increasing number of organisms from the polar regions are reported contaminated by plastic. Rarely a non-killing sampling method is used. In this study we wanted to assess plastic levels using stomach flushing and evaluate the method suitability for further research and monitoring. The stomach of 22 fulmars from Bjørnøya, Svalbard, were flushed with water in the field. On return to the laboratory, the regurgitated content was digested using potassium hydroxide. The extracted plastics were visually characterised and analysed with spectroscopy. Only three birds had plastics in their stomach, totaling 36 particles, most of them microplastics (< 5 mm). The plastic burdens are much lower than previously reported in Svalbard. The stomach flushing is assumed not to allow the collection of the gizzard content. This is a major limitation as most of the plastics accumulate in the fulmar's gizzard. However, the method is still useful for studies investigating plastic ingestion dynamics, allowing to sample the same individuals over time.

First record of plastic debris in the stomach of a hooded seal pup from the Greenland Sea.

Plastic debris is globally found around the world and the remote Arctic is no exception. Arctic true seals are sentinel species of marine pollution and represent the link between marine food webs and Arctic apex predators like polar bears and humans. With regard to true seals, ingested macroplastics have never been reported in an Arctic species. We harvested 10 harp seals Pagophilus groenlandicus and 8 hooded seals Cystophora cristata from the breeding grounds in the pack ice of the Greenland Sea. The digestive tract was inspected exclusively for the presence of macroplastics (>5 mm). Two pieces of single-use plastic were found in the stomach of a weaned hooded seal pup. This study indicates that young Arctic marine predators may ingest macroplastics, and therefore may be at risk during their early stages of life due to human caused plastic pollution even in the remote Arctic pack ice.

Anthropogenic particles in sediment from an Arctic fjord.

The research on plastic pollution is increasing worldwide but little is known about the contamination levels in the Arctic by microplastics and other anthropogenic particles (APs) such as dyed fibres. In this study, two different sampling designs were developed to collect 68 sediment subsamples in five locations in a remote Arctic fjord, Kongsfjorden, northwest of Svalbard. Those five stations composed a transect from a sewage outlet recently installed close to the northernmost settlement, Ny-Ålesund, to an offshore site. Plastics and other APs were extracted by density separation and analysed by both Raman and Fourier Transform Infrared spectroscopy. Among the 37 APs found, 19 were microplastics. The others were classified as APs due to the presence of a dye or another additive. On average, 0.33 AP 100 g-1 were found in the surface sediment and their sizes ranged between 0.10 and 6.31 mm. The site most polluted by APs was located at the mouth of the fjord while the less polluted ones were the offshore and the outlet sites. We believe that currents in the fjord have carried APs towards the mouth of the fjord where an eddy could retain APs which might sink the seafloor due to various reasons (ingestion & packaging, fouling-induced changes in buoyancy). In the cores, several different APs were found down to a depth of 12 cm. These APs may have been present in the sediments for decades or been transported deeper by biota. Here we provided data on plastic but also on other anthropogenic particles from a remote fjord in Svalbard.