Our research is focused on developing and utilising geochemical proxies to track environmental change in the oceans in time and space. Isotope and trace element records, extracted from the skeletons of marine calcifiers in particular (e.g. corals, sclerosponges, foraminifers, coralline algae) that can inhabit shallow waters to deep-sea environments, are used to determine how climate and anthropogenic processes have influenced our oceans over recent and geological timescales. Integral to this work, is studying biomineralisation processes, and how they influence the geochemical compositions.
Gechemical techniques commonly employed include boron isotopes and trace elements concentrations for reconstructing seawater pH, temperature, nutrient flux, carbonate ion and hence saturation state, in order to understand the processes of anthropogenic driven climate change and ocean acidification. The uranium-thorium disequilibrium dating technique is also used to analyse carbonates, which can provide absolute dates for samples ranging from >100,000 to several years in age. All geochemical preparation and mass spectrometry is undertaken in the state-of-the-art Advanced Geochemical Facility for Indian Ocean Research (see Facilities).
A range of biogenic archives underpin our research, which addresses present day issues of climate change and ocean acidification, water pollution, as well as understanding environmental changes over longer (geological) timescales, that latter providing key boundary-conditions essential to constraining ocean-atmosphere models. Our research projects are utilising a range of species of shallow water corals, sclerosponges, foraminifers, deep-sea corals, and coralline algae. Simulation of future ocean conditions to ‘ground-truth’ the responses of these biogeochemical archives to climate and environmental changes are being undertaken at the newly constructed Indian Ocean Marine Research Centre, Watermans Bay, located ~24 kms from the main UWA Crawley campus (see Facilities).
Shallow water coral reef environments are facing threats from both CO2 driven ocean warming as well as ocean acidification. State-of-the-art geochemical proxy studies of long-lived massive corals, sclerosponges, as well as foraminfera, are used to track long-term changes in temperature and carbonate chemistry (ie pH, carbonate ion) of reef-waters from a range of environments. These studies aim to identify and characterise both longer-term changes as well as extreme coral bleaching events to provide insights into coral recovery, as well as the frequency and longer-term impacts accompanying these events. Understanding the vulnerability of coral reef habitats that occur along Australia’s and especially Western Australia’s extensive coastline is of paramount interest.
Field monitoring of bleach-affected shallow water coral reef sites are being undertaken and experiments are being conducted to understand the controls and thresholds of coral bleaching of particular species, and thus the survival of coral reefs under extreme conditions. Coral reef environments include the tidally extreme tropical environment of the Kimberley down to the temperate reefs of southwestern Australia, where environments are moderated by the warm and southwards flowing Leeuwin Current.
The ecology and geochemistry of a variety of marine calcifiers across the Western Australian coast (Kimberley, Exmouth, Abrolhos Islands, Perth, and Albany) are being studied to understand the influence of climate change on the calcification process. In-situ field studies are complemented by controlled experiments within laboratory flumes and mesocosms, in the purpose-built Watermans facility north of Perth (see Facilities).
Biomineralisation studies also utilise state-of-the-art facilities, such as Secondary ion mass spectrometry (SIMS) for high spatial resolution analyses; optical and electron microscopy; X-ray micro-computed tomography (micro-CT) and confocal Raman imaging and Atomic Force Microscope (AFM) located UWA’s Centre for Microscopy, Characterisation and Analysis (CMCA).
Australia’s coastal zone contains some of the planets most spectacular and unique environments, with many such as the Great Barrier Reef being recognised as having World Heritage value. However, even those coastal environments, which had been previously considered as relatively pristine and isolated, such as Western Australia’s Ningaloo Reef and Kimberley region, face growing risks including those posed by large oil and gas infrastructural projects in the North West. Furthermore, all of Australia’s major capital cities are coastal, with nearshore waters being subject to a growing range of pollutants from ever-increasing urbanisation and industrialisation. To meet these expanding range of threats we are developing new classes of ‘naturally occurring’ proxies to monitor both event-based pollution and longer-term progressive increases of toxic chemical elements within the costal environments. This includes quantifying element-specific uptake rates of marine pollutants during biomineralisation of marine calcifiers in particular. The aim is to develop novel and robust approaches (including geochemical tracers/proxies) for assessing and monitoring anthropogenic pollution of shallow marine ecosystems, such as coral reefs and seagrass meadows.
Geochemical proxy records extracted from deep-water coral skeletons are being used track environmental changes in intermediate to deep waters in space and time. A wide range of geochemical tools (including U-Th, 14C, εNd, δ13C, δ15N, Li/Mg, B/Ca, Ba/Ca, U/Ca) are being used to understand ocean-climate interactions at local and regional scales between the southeast Indian Ocean (Perth Canyon) and Antarctica. The aim is to characterise changes in ocean circulation patterns, climate trends, and carbon flux during recent (anthopogenic and pre-industrial) times and through the last glacial-interglacial cycle (~30-15 ka), in order to understand the drivers and long-term responses in Earth’s ocean-climate system during periods of major climate change.