How will the key science questions be addressed?
Ocean chemistry - nutrients
How do variations in oceanic nutrient supply (such as through the upwelled Kangaroo Island cold pool) impact of phytoplankton communities?
What roles do canyons and gulfs play as a source of nutrients?
Conductivity Temperature Depth casts at each of the existing 6 monitored sites will be complemented by water sampling to analyse the nutrient concentration, suspended matter and phytoplankton biomass and communities. These data will be compared to the physical data obtained from the moorings in order to understand the impact of physical processes on the nutrients and plankton.
How are variations in primary productivity related to variations in oceanic nutrient supply and what are the lags of biological response?
The spatial and temporal variations in primary productivity will be examined via the data streams of 14C uptake (14C uptake allows the measurement of dissolved inorganic carbon incorporation into biomass, and is the benchmark against which all other techniques have traditionally been measured). These data will be obtained seasonally (February, May, July and November) to examine primary production during the upwelling season, with the decline of upwelling, during winter downwelling, and at the onset of the new upwelling season. Data will be collected at the National Reference Station mooring site, at the surface and 10 m below the deep chlorophyll maximum in order to target the two different water masses known to be present within the euphotic zone of this region.
What are the critical fluxes such as primary productivity and the related changes in phytoplankton communities, ocean-atmosphere fluxes and vertical fluxes?
In addition to the pCO2 mooring maintained at the National Reference Site site, data from 3 autonomous plankton recorders will be collected from the three continuously maintained moorings to assess primary and secondary productivity. These moorings are the National Reference Station, and the moorings off the Eyre Peninsula and at the mouth of Spencer Gulf. These moorings will also have temperature loggers so that the depth of the surface mixed layer can be monitored.
What is the temporal and spatial variability in secondary producers (e.g. zooplankton) on the coastal shelf? How this variability impacts on fish communities?
As stated above, 3 Autonomous Plankton Recorders will be collected from the three continuously maintained moorings to assess primary and secondary primary productivity. This will allow the assessment of the temporal and spatial variability of the plankton species (i.e. phytoplankton and zooplankton) larger than 270μm. These data will be compared to the physical data obtained from the moorings in order to understand the impact of physical processes on the nutrients and plankton. In addition, at each of the 6 monitored sites zooplankton species at 2 different depths (above and below the Deep Chlorophyll Maximum) will be sampled.
Ocean chemistry - carbon and acidification
What is the space-time dynamic of the trophic state of S.A. shelf waters, and do they act as a source or a sink of CO2?
We will assess the respiration and production rates of the planktonic community through dissolved oxygen consumption measurements. This will be conducted seasonally (in February, May, July and November) to examine respiration/production during the upwelling season, with the decline of upwelling, during winter downwelling, and at the onset of the new upwelling season. Using the above data, we can then assess the trophic status of the system, i.e. net autotrophic or net heterotrophic and convert this into data streams of a CO2 budget that will vary in space and time.
What are the key physical oceanographic features that underpin the distribution, key foraging locations, movements and migratory patterns of apex predators?
Conductivity Temperature Depth tags will be deployed on Australian sea lions to assist in monitoring the spatial and temporal extent of upwelling in the Eastern Great Australian Bight between November and May each season. The aim is to provide sustained observations over a ~7 month period across seven sites (analogous to XBT lines) between the Booney Coast and the heat of the Bight. Sea lion data will be augmented by deployments of instruments onto other apex predators (including short-finned mako and new Zealand fur seals), which can sample slope waters off the Eastern Great Australian Bight and near oceanic waters south to the Subtropical Front. Data will allow us to identify key regions of production and hot-spots of predator activity and to identify regions where strategic placement of existing observing platforms, such as fixed moorings or directed ship-based research, may be made. The approach of sustained observations using instrumented apex predators is part of the Animal Tagging and Monitoring southern seals as oceanographic samplers program.
How do foraging distributions and movements of different apex predator species respond to the spatial and temporal variability in boundary currents and upwelling intensity?
Bio-logging instruments (GPS tracking with temperature depth sensors) will be deployed on New Zealand fur seals and mako sharks throughout the year to collect information on the physical habitats they use. By deploying temperature-depth sensors we will be able to track changes in the physical environment used by these predators. We will compare data collected on the shelf from sea lion Conductivity Temperature Depth tags and other facilities (National Mooring Network, ocean gliders, Satellite Remote Sensing) to describe the dynamics of shelf and pelagic habitats available throughout the year and provide context for the switch in foraging locations. The strategy is to collect sustained observations of these key foraging grounds and oceanographic associations across multiple seasons and is part of the Animal Tagging and Monitoring southern seals as oceanographic samplers program.
What are the likely physical and biological implications of climate change on the spatial and temporal distribution of benthic and pelagic production, and how will this impact the foraging distributions and movements of apex predator populations?
Acoustic receivers will be used to investigate the residence time, movements, migratory routes and inter-connectivity between a range of different habitats of several predators (e.g., white sharks, whaler sharks, southern blue-fin tuna, mulloways, snappers, gulper sharks, and whitefin swell sharks) and how these change with varying oceanographic conditions monitored through the oceanographic moorings, gliders, apex predator Conductivity Temperature Depth tags, and coastal radar. Existing acoustic receivers will be combined with newly deployed receivers to link the oceanographic observations to the detections obtained from tagged animals. The already deployed receivers include receivers located at the entrance of the Gulfs (i.e. Neptune Islands), off the continental shelf edge southwest of Cape Wiles and off Glenelg Beach (Adelaide).
How does exploitation of the Bonney coast upwelling by great whales vary across years? How does visitation of the Bonney coast by pygmy blue whales fit with seasonal migrations along the eastern and western Australian coasts? Can the presence of whales or fish choruses known to occur along the shelf edge, be used as an indicator of productivity or vice/versa?
To address these questions we aim to maintain the current passive acoustic observatories to 2013 and beyond to gain a long time-series data set.
How does the breeding success and trends in abundance of apex predator populations respond to the spatial and temporal variability in boundary currents and upwelling intensity? What are the likely implications of climate change on the status, distribution and abundance of apex predator populations?
Apex predators are sensitive to changes in the distribution and abundance of their prey, which in turn respond to changes in the lower trophic levels and the physical environment. The observation strategy is to collect sustained observations of selected apex predator populations in response to oceanographic change, including climate change. This will be achieved by monitoring one land-breeding pelagic predator (New Zealand fur seal) and one land-breeding benthic predator (Australian sea lion). These observations are designed to provide indices of whole of ecosystem response to climate change and compliment the Monitoring of Apex Predators in the Southern Ocean program (MAPSO).
What are the impact of viral infaction and the subsequent lysis of marine microbes and other organisms? How does this impact the auatic food web and predators on the coastal shelf?
Determining the abundance and community composition of bacteria and viruses from the water samples obtained at each of the 6 monitored sites will help address these questions. The viral lysis as well as the micro-zooplankton grazing and the mortality of bacteria and phytoplankton populations will be assessed seasonally (in February, May, July and November). The seasonal survey will allow the examination of primary production during the upwelling season, with the decline of upwelling, during winter downwelling, and at the onset of the new upwelling season.