Food web dynamics in the Scotia Sea in summer: A stable isotope study

摘要: The pelagic food web of the Scotia Sea was studied by analysing natural abundances nitrogen and carbon stable isotopes primary producers consumers, sampled from seasonal ice edge in south to Antarctic Polar Front north. analysis covered, within a single mid-summer period, particulate organic matter (POM) 38 taxa, ranging suspension feeding copepods salps omnivorous euphausiids, fish higher, land-based predators including fur seals, penguins flying birds. Spatial variation δ15N POM correlated well with nutrient availability productivity. Latitudinal differences δ13C were closely linked variations temperature, nutrients productivity depending on frontal region sampled. This translated equivalent (although smaller) regional among higher trophic levels. positions species based isotope values broadly agreed previously published dietary data three important exceptions. First, carnivorous amphipod Themisto gaudichaudii had anomalously low values. Second, Euphausia superba that also surprisingly low, considering abundant literature suggesting its omnivory. Third, copepod Rhincalanus gigas, considered feeder, unexpectedly high rather more keeping feeding. consumer ranged 1.2‰ (min.) measured Salpa thompsoni (designated here as level (TL) 2 across all regions) 15.2‰ (max.) white-chinned petrels (Procellaria aequinoctialis, calculated TL5 relative TL2 salps). Excluding seabirds, resulting chain length 3.7 TL (above at TL1) lower than most other Southern Ocean temperate marine ecosystems. majority (60%) vertebrate occupied only 1–1.5 levels above herbivorous feeders such krill. indicates existence classic short POM–suspension feeder–vertebrate predator. However presence 4 alternative pathways, for example involving myctophid or carrion, some wide-ranging which breed South Georgia feed outside region. conclusion is supported first continuum between krill, fish, secondly several low-krill northern Sea, latitudinal structure length.