Ecosystem Responses

Biogeochemical drivers of reef water carbon chemistry and effects of ocean acidification on aragonite saturation state (Ωa). Vectors indicate the shift of the benthic biological/biogeochemical processes from a present-day (solid) to an acidified (dashed) scenario at 27OC and 35PPT. Absolute vector lengths are hypothetical, but will vary with water depth, residence time, and the mix of primary producers and calcifiers (Source: Ken Anthony, AIMS)
Biogeochemical drivers of reef water carbon chemistry and effects of ocean acidification on aragonite saturation state (Ωa)

The physical and chemical environment strongly influences the biology of coastal and oceanic systems. Historically, however, there has been relatively little integrative work on the linkages between physics, chemistry and biology in Queensland’s marine ecosystems.

Various modes of climate variability affecting temperature, upwelling and shelf currents, plus long-term trends in ocean pH have been identified. The latter will potentially be very important in the future to organisms reliant upon calcification whereas temperature changes are critically important now for all poikilothermic organisms.

Thermal stress has been suggested to eliminate zooanthellate corals on a much shorter time scale than the ultimate threat from ocean acidification. Thus the marine community needs to collect data on the spatial and temporal variability of pCO2 and alkalinity of water on a complex carbonate shelf like the Great Barrier Reef (GBR) to better define the future risks from ocean acidification, but it should prioritise other variables that display significant variability over shorter time scales. 

Changes in temperature, upwelling, and shelf currents will be critical drivers of Queensland’s marine ecosystems over the next decade. There are many research questions appealing to different investigators and it is not possible to capture all of them here, so we illustrate the utility of ocean observations to understanding and predicting ecosystem responses through selected examples.

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

Productivity:

  • What is the risk of climate change to reef building corals?
  • How does carbonate chemistry vary in coral reef ecosystems?
  • What is the risk of ocean acidification to coastal and reef ecosystems?
  • Does the risk of ocean acidification vary between tropical and temperate zones?
  • How does the spatial variability in physical processes (currents, waves energy, mixing) influence and modulate the spatial variability of risk to benthic and pelagic communities associated with climate change (e.g. temperature induced bleaching, acidification)
  • What drives productivity hotspots on the continental shelf of Queensland?
  • How do external sources of nutrients change pelagic and benthic communities? (e.g. stinging jellyfish, Crown-of-thorns starfish)
  • Do deep seagrass meadows on the GBR shelf reflect upwelling history?

Distribution and Abundance:

  • What drives the northern limits of kelp forests in SEQ?
  • What are the environmental drivers of animal migrations?
  • What are the oceanographic correlates of nesting success of seabird colonies in the GBR?
  • How can we predict connectivity of populations in shelf ecosystems? (e.g. Crown-of-thorns outbreaks)
  • What is the impact of extreme weather on benthic communities along depth gradients?
  • How do environmental perturbations affect animal migrations?