Quantitative fatty acid signature analysis reveals a high level of dietary specialization in killer whales across the North Atlantic

Quantifying the diet composition of apex marine predators such as killer whales (Orcinus orca) is critical to assessing their food web impacts. Yet, with few exceptions, the feeding ecology of these apex predators remains poorly understood. Here, we use our newly validated quantitative fatty acid signature analysis (QFASA) approach on nearly 200 killer whales and over 900 potential prey to model their diets across the 5000 km span of the North Atlantic. Diet estimates show that killer whales mainly consume other whales in the western North Atlantic (Canadian Arctic, Eastern Canada), seals in the mid-North Atlantic (Greenland), and fish in the eastern North Atlantic (Iceland, Faroe Islands, Norway). Nonetheless, diet estimates also varied widely among individuals within most regions. This level of inter-individual feeding variation should be considered for future ecological studies focusing on killer whales in the North Atlantic and other oceans. These estimates reveal remarkable population- and individual-level variation in the trophic ecology of these killer whales, which can help to assess how their predation impacts community and ecosystem dynamics in changing North Atlantic marine ecosystems. This new approach provides researchers with an invaluable tool to study the feeding ecology of oceanic top predators

Comparative analysis of persistent organic pollutants in free-ranging grey and harbour seals from Scotland: Influence of habitat, diet, and sex

editorial reviewed14. Life below wate

PERSISTENT ORGANIC POLLUTANTS IN HUMPBACK WHALES FROM THE SOUTHERN HEMISPHERE: INFLUENCE OF GENDER, STOCK AND TROPHIC ECOLOGY

Humpback whales, Megaptera novaeangliae, from the southern hemisphere undergo large scale seasonal migrations between their summer feeding grounds near Antarctica and their winter reproductive grounds in the subtropical to tropical regions. However, population structure data in the southern hemisphere is scarce. The aim of this study was to get information on stocks structure in the Southern hemisphere using chemical tracers; stable isotopes and persistent organic pollutants (POPs) concentrations in Humpback whales from two stocks: stock C1 breeding off Mozambique and stock G breeding off Ecuador. Material and methods: Skin and blubber biopsies of humpback whales from Ecuador (2014-2015, n= 60) and Mozambique (2017, n=89) were sampled. δ13C and δ15N values were analyzed in skin. POPs were analyzed in the blubber: polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCPs) including dichlorodiphenyltrichloroethane and its metabolites (DDXs), hexachlorobenzene (HCB), lindane (HCHs), chlordanes (CHLs) and methoxylated PBDEs (MeO-PBDEs). Gender was determined genetically (see Das et al. 2017 for detail in methodology). Results: Low δ13C and δ15N values in skin reflected their diet focused mainly on low trophic level prey species, such as krill from Antarctica, Euphausia superba. One group in the Mozambique stock had higher δ15N values. Gender did not account for this variation. Other driving factors could be the metabolic state, the age, the geographic δ15N variations in feeding grounds, or a more opportunistic diet in Antarctica that includes small fish. The isotopic niches from Mozambique and Ecuador did not overlap indicating that the two populations exploit different resources. The differences in δ13C (p-value < 0.01) between the two populations suggested a different geographic source of primary productivity meaning the whales do not feed in the same area. However, female humpback whales in Ecuador had significant lower δ15N (p-value < 0.01) and δ13C (p-value < 0.01) values than males maybe suggesting different feeding habits between males and females within this population. POPs were measured in humpback whales in the order of HCB > DDXs > CHLs > PCBs > HCHs > PBDEs > MeO-PBDEs. HCB (mean: 66.5 ng/lw in Mozambique and 36.5 ng/lw in Ecuador) and DDXs (mean: 8 ng/lw in Mozambique and 24 ng/lw in Ecuador) were the predominant compounds in all humpback whale samples. Significantly higher concentrations of HCB were found in whales from Mozambique (p-value < 0.01). Significantly higher concentrations in DDXs (p-value < 0.01) and HCH (p-value < 0.01) were found in whales from Ecuador. Among DDT compounds, p,p’-DDE was the major pollutant, reflecting its long-term accumulation in humpback whales. Levels in POPs were in accordance with other studies from the southern hemisphere and were in each case lower in the southern hemisphere than in the Northern hemisphere. Pollutants were not correlated with δ15N, lipid content in the blubber or time. However, males had significantly higher HCB (p-value < 0.05), PCBs (p-value < 0.01) and CHLs (p-value < 0.01) concentrations than females. Conclusions: While gender seems to be the main reason for POP variation, the feeding zones also need to be considered as a factor of POPs variation. Further investigations are required to assess exposure of southern humpback whales throughout their feeding zones

Humpback whales (Megaptera novaeangliae) breeding off Mozambique and Ecuador show geographic variation of persistent organic pollutants and isotopic niches

Humpback whales (Megaptera novaeangliae) from the Southern Hemisphere carry information on persistent organic pollutants (POPs) from their feeding zones in Antarctica to their breeding grounds, making this species a sentinel of contaminants accumulation in the Southern Ocean. This study aimed to evaluate driving factors, namely feeding areas, trophic level, and sex, affecting POP concentrations in the blubber of humpback whales breeding off Mozambique and off Ecuador. Biopsies of free-ranging humpback whales including blubber and skin were collected in 2014 and 2015 from Ecuador (n = 59) and in 2017 from Mozambique (n = 89). In both populations, HCB was the major contaminant followed by DDTs > CHLs > PCBs > HCHs > PBDEs. POP concentrations were significantly higher in males compared to females. HCB, DDTs, HCHs and PBDEs were significantly different between whales from the Mozambique population and the Ecuador population. Sex and feeding habits were important driving factors accounting for POP concentrations in Ecuador whales. The whales from our study had some of the lowest POP concentrations measured for humpback whales in the world. These whales fed predominantly on krill as reflected from the low δ13C and δ15N values measured in the skin. However, the isotopic niches of whales from Mozambique and Ecuador did not overlap indicating that the two populations are feeding in different areas of the Southern Ocean.EXPOSURE OF HUMPBACK WHALES FROM THE SOUTHERN HEMISPHERE TO PERSISTENT ORGANIC POLLUTANTS: INFLUENCE OF THEIR ISOTOPIC NICHE, SEX AND AGE DETERMINED BY EPIGENETIC