Tracking for Southern Ocean change: an integrated approach
using animal tracking, isotopes & biogeochemical modelling to simulate ecosystem variability
Understanding ecosystem responses to the rapid change currently occurring in the Southern Ocean, due to climate change and other stressors, is crucial. The capacity of organisms to adapt to rapid changes in the dynamics of biological cycles remains poorly known, so it is not adequately represented in current ecosystem and food web models.
Basic biological information is vital for quantifying and predicting whole ecosystem changes, but it is not available for species across all trophic levels in vast regions of the Southern Ocean. However, meso- and top predators like whales, seals and penguins are valuable ecological indicators of the status of lower trophic levels.
A major new frontier in marine isotope ecology lies in using isotope-enabled, global biogeochemical models to simulate isotopic compositions of key indicator species expected under differing, known movement behaviours. Isotopes cannot provide unambiguous information (influenced by location, diet, physiology), while tracking data gives location, but not diet/physiology. Combining the two approaches helps to infer movement ecology more holistically.
Since 2008, researchers from Australia (IMAS, AAD, UTS), South Africa (University of Pretoria), the UK (British Antarctic Survey, University of Southampton), the USA (NOAA AMLR) and France (CEBC) have joined forces to track female Antarctic fur seals (Arctocephalus gazella, Figure 1) from the Indian Ocean sector of Marion Island, Bird Island South Georgia, and the SW Atlantic sector of Cape Shirreff Antarctic Peninsula during the eight-month non-breeding season with miniature geolocation tags. The circumpolar study has revealed that these 35-50kg animals range up to 16000km across the Southern Ocean during the winter – from the ice edge to temperate latitudes.
This project is supported by the Australian Research Council and is filling a fundamental gap in our understanding of how biodiversity responds to environmental changes, such as anthropogenic pressures, climate change and natural variability. The project is achieving this using tracking and archival tissue dataset, gathered over 10 years, for a key Southern Ocean predator, the Antarctic fur seal (Figure 1). Through the application of novel biogeochemical modelling techniques based on this unprecedented and existing ten-year dataset, we are assessing how animal behaviour relates to physical habitats, prey availability and productivity in the Southern Ocean, and developing new and effective tools to monitor ecosystem change in remote oceanic environments.
Project aims:
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Calculate ocean-basin scale estimates of trophic position and food chain length in the Southern Ocean using archival tissues
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Quantify preferred foraging strategies and their stability, over decadal time scales, for a model, far-ranging, Southern Ocean marine predator (the Antarctic fur seal)
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Quantify heavy metal variability and ecosystem implications using novel bio-imaging techniques of archival tissues, and
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Assess the applicability of archival tissues as an integrated early warning signal for large-scale, Southern Ocean ecosystem change using biogeochemical simulation modelling.
