Ecosystem Reponses

Regional nutrients: Analysis of all CSIRO surface (0m) data for silicate (top panel), nitrate (middle panel) and phosphate (bottom panel). Concentrations (µM) are given on the major contours.
Regional nutrients: Analysis of all CSIRO surface (0m) data for silicate (top panel), nitrate (middle panel) and phosphate (bottom panel). Concentrations (µM) are given on the major contours.

Ecosystem change is anticipated via climate change impacts on temperature, the hydrological cycle, and ocean circulation, and the influences of these changes on biogeochemical properties such as nutrient delivery and oxygen levels. Attention to the role of boundary currents and the overturning circulation provides a unifying approach for the assessment of what are likely to be diverse and complex impacts.

The two major poleward flowing boundary currents around Australia, the East Australian Current and the Leeuwin Current, play a vital role in regulating the productivity of pelagic and benthic ecosystems. The warm boundary currents are generally nutrient poor with only patchy upwelling, leading to marine systems of low productivity. Tropical and subtropical species can exist in relatively high latitudes, especially as the East Australian Current has increased in strength over the past 60 years. Another key area for the south east Australia region is the Southern Ocean. Changes in Southern Ocean circulation can be thought of as sensitive early indicators of global climate changes, which also affect the Southern Ocean ecosystem. 

The following high-level science questions will guide the Southeast Australia IMOS observing strategy in this area:

Productivity:

  • What is the role of the EAC and eddies on primary production in the south east region?
  • Does tide or wind driven upwelling increase the productivity of the south east region?
  • What mechanism determines the location of the SubTropical Front and how does this impact on South East Australia ecology. 
  • What controls the temporal variation in biogeochemical fluxes and how they respond to climate variability? 
  • How will the biotic changes impact on carbon uptake and sequestration? 
  • How will components of the ecosystems respond to variation physical processes including global change? 

    • Microbial/Phytoplankton
    • Zooplankton
    • Nekton
    • Benthic communities
    • Commercial fish stocks

Biodiversity:

  • What is the relationship between biodiversity, structure, function, and stability of marine ecosystems? 
  • What is the distribution and condition of marine habitats within Bass Strait? 
  • What are the characteristics of canyon heads that support greater biodiversity?
  • Does Bass Strait have ‘hotspots’ of biodiversity? The region to the south and east of King Island also appears to be an area of interest in August and September for dwarf minke whales and likely other predators and fish species- Why?
  • Are “Pelagic biodiversity hotspots” and “seafloor biodiversity hotspots” collocated with key ecological features [KEFS]?

Distribution and abundance:

  • What are the long term impacts of climate variability on benthic ecology? 

    • What determines the spatial and temporal variation in C. rodgersii and of M. pyrifera?  

  • How interconnected are our populations of mobile species? 
  • There is increasing interest in spatial management for both fisheries and conservation management yet we do not have a clear picture of the movement dynamics of most species and hence the efficacy of such management. In particular the management of endangered species requires more information on spatial dynamics.