Adelie penguin diet composition, preliminary analyses of whole lavaged samples, 1991 - 2017.
The fundamental long-term objective of the seabird component of the Palmer LTER (PAL) has been to identify and understand the mechanistic processes that regulate the mean fitness (population growth rate) of regional penguin populations. Two hypotheses have guided this research, with one suggesting t...
| Main Authors: | , |
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| Format: | Dataset |
| Language: | English |
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Environmental Data Initiative
2020
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| Online Access: | https://dx.doi.org/10.6073/pasta/32b2d306e9817212a9ad54d56f6d91d7 https://portal.edirepository.org/nis/mapbrowse?packageid=knb-lter-pal.89.7 |
| Summary: | The fundamental long-term objective of the seabird component of the Palmer LTER (PAL) has been to identify and understand the mechanistic processes that regulate the mean fitness (population growth rate) of regional penguin populations. Two hypotheses have guided this research, with one suggesting that population mean fitness is best explained by changes in regional krill biomass, and the other proposing that long-term changes in sea ice affects mean fitness by tipping the balance in favor of one species over another in accordance with species-specific evolved life history affinities to sea ice. Although these hypotheses are not mutually exclusive, current evidence in the PAL region tends to favor the latter over the former. Since the inception of PAL, Adélie penguin populations have effectively collapsed, while those of gentoo and chinstrap penguins have increased dramatically, trends that are spatially and temporally coherent with decreasing regional sea ice duration. Adélie penguins are an ice-obligate polar species whose life history is intimately linked to the presence of sea ice, while chinstrap and gentoo penguins are ice-intolerant species whose life histories evolved in the sub-Antarctic, where sea ice is a less permanent feature of the marine ecosystem. In contrast, although krill constitute the most important component of the summer diets by mass of these three penguin species, changes in PAL krill abundances have exhibited no long-term trends, and thus fail to explain the divergent patterns in penguin populations evident in our time series. Adélie penguin diet samples obtained in the field (see HEADER) are initially drained and weighed and returned to laboratories for further processing. This includes resuspension of the samples in fresh water to release fish otoliths, squid beaks and other prey hard parts, and then draining to a consistency that facilitates separating the diet samples into subsamples of primary and secondary prey components. Primary prey components include krill and fish, and secondary prey components include octopus, squid amphipods, mysid shrimp, limpets and small clams. Each prey component is weighed (total weight) and, if possible, sorted according to species for further analyses. Variability in diets within and between seasons is strongly linked to variability in the marine environment such as the presence or absence of sea ice and the timing and persistence of phytoplankton blooms, and thus affects a host of Adélie penguin life history parameters. |
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