Biology subjects

Routledge, J.

Publications and source records attributed to Routledge, J..

3 recordsLinked to original sources

bioRxiv2022

Unprecedented shift in Canadian High Arctic polar bear food web unsettles four millennia of stability

Stable carbon ({delta}13C) and nitrogen ({delta}15N) isotope analysis was conducted on modern and archaeological polar bear bone collagen from the Canadian Arctic Archipelago to investigate potential changes in polar bear foraging ecology over four-millennia. Polar bear{delta} 13C values showed a significant decline in the modern samples relative to all archaeological time-bins, indicating a disruption in the sources of production that support the food web, occurring after the Industrial Revolution. The trophic structure, indicated through{delta} 15N, remained unaltered throughout all time periods. The lower{delta} 13C observed in the modern samples indicates a change in the relative importance of pelagic (supported by open-water phytoplankton) over sympagic (supported by sea ice-associated algae) primary production. The consistency in polar bear{delta} 13C through the late Holocene includes climatic shifts such as the Medieval Warm Period (MWP, A.D. 950-1250) and the early stages of the Little Ice Age (LIA, A.D. 1300-1850). These findings suggest that polar bears inhabit a food web that is more pelagic and less sympagic today than it was through the Late Holocene. We suggest that modern, anthropogenic warming has already affected food web structure in the Canadian Arctic Archipelago when modern data are contextualized with a deep time perspective. Research HighlightsO_LIModern polar bear bone collagen{delta} 13C suggests recent decline in ice associated prey. C_LIO_LIArchaeological polar bear bone collagen suggests food web stability for millennia. C_LIO_LINo change in sea-ice association through the Medieval Warm Period and Little Ice Age. C_LIO_LIRecent isotopic shifts are unusual relative to the stability of ancient samples. C_LIO_LIModern Arctic warming has isotopically observable impacts that past events did not. C_LI OR Significance StatementThe lack of behavioral plasticity of both polar bears and their principal prey, ringed seals, make these species particularly vulnerable to declining sea ice. While the Lancaster Sound food web has demonstrated stability through past climate fluctuations, the speed and magnitude of ongoing changes in the Arctic has had an observable effect on the source of primary production. Given that past climate fluctuations are referenced as an argument to minimize the importance of modern anthropogenic warming, it is important to take opportunities to position contemporary climate change relative to the archaeological record. Here we present a unique illustration of the effects of past and present warming on polar bear diet and the marine food web in the Canadian Arctic Archipelago.

ecology↗

bioRxiv2022

Sex and size matter: foraging ecology of offshore harbour porpoises in waters around Greenland

Individuals of different sex or age can vary in their resource use due to differences in behaviour, life history, energetic need, or size. Harbour porpoises are small cetaceans that rely on a constant prey supply to survive. Here, we use bone collagen carbon ({delta}13C) and nitrogen ({delta}15N) isotope compositions to elucidate sex and size differences in the foraging ecology of harbour porpoises from West Greenland. In this region, populations have a unique offshore, deep-water ecology. Female harbour porpoises are larger than males and we find that females have a higher trophic level than males, and {delta}15N positively correlates with size for females only. This indicates that size may matter in the ability of females to handle larger prey and/or dive deeper to catch higher trophic level prey. These results suggest that females, which also feed their calves, may be under different ecological constraints than males. We also analysed the harbour porpoise data with comparable stable isotope data from Greenland populations of belugas and narwhals. Consistent with their small body size, and a diet consisting primarily of capelin, we find that harbour porpoises have a lower trophic level than belugas and narwhals. Furthermore, harbour porpoises have the largest ecological niche of the three species, which is in accordance with tagging studies indicating they have a wide range in shelf and deep offshore waters of the sub-arctic and North Atlantic.

ecology↗

bioRxiv2021

Combining δ13C and δ15N from bone and dentine in marine mammal palaeoecological research: insights from toothed whales

Stable carbon ({delta}13C) and nitrogen ({delta}15N) isotope compositions of bone and dentine collagen extracted from museum specimens have been widely used to study the paleoecology of past populations. Due to possible systematic differences in stable isotope values between bone and dentine, dentine values need to be transformed into bone-collagen equivalent using a correction factor to allow comparisons between the two collagen sources. Here, we provide correction factors to transform dentine{delta} 13C and{delta} 15N values into bone-collagen equivalent for two toothed whales: narwhal and beluga. We sampled bone and tooth dentine from the skulls of 11 narwhals and 26 belugas. In narwhals, dentine was sampled from tusk and embedded tooth; in beluga, dentine was sampled from tooth.{delta} 13C and{delta} 15N were measured and intraindividual bone and dentine isotopic compositions were used to calculate correction factors for each species. We detected differences in{delta} 13C and{delta} 15N. In narwhals, we found (i) lower average{delta} 13C and{delta} 15N in bone compared with dentine; (ii) no difference in dentine{delta} 13C between tusk and embedded tooth. For belugas, we also detected lower{delta} 13C and{delta} 15N in bone compared with tooth dentine. The correction factors provided by the study enable the combined analysis of stable isotope data from bone and dentine in these species.

ecology↗