The three-main vegetated coastal habitats – mangroves, tidal marshes, and seagrasses – play an important part in the marine carbon cycle and are therefore referred to as ‘blue carbon ecosystems’.
On a per unit area, blue carbon ecosystems have some of the highest soil/sediment carbon stocks on the planet. Blue carbon ecosystems also show the potential of high yearly carbon sequestration via deposition of photosynthetically fixed carbon in predominantly anoxic sediments where decomposition is slower than in soil systems. Therefore, blue carbon ecosystems may potentially have an important role in climate change mitigation.
In the Blue Carbon theme, we aim to improve the understanding of how the management of Blue Carbon in Australia’s coastal ecosystems can contribute to climate mitigation. To do this we work on projects that will reduce the uncertainty in regional estimates of carbon stock estimates, and uncertainties in estimates of potential carbon accumulation rates (in Australia). We further work on projects assessing the impacts of management activities in Australia’s vegetated coastal ecosystems by demonstrating and evaluating feasible on-ground activities for increasing carbon storage. Projects in the Blue Carbon theme fall in two categories.
The first category involves reducing uncertainties in estimates of blue carbon ecosystem carbon stock and carbon sequestration potential.
Project 1: Spatial variation in blue carbon stocks of temperate mangroves in SE Australia and the role of fine roots in down core carbon deposition
This project is assessing small-scale spatial variation in carbon stocks and carbon accumulation rates for temperate mangrove sites within Western Port, to determine what type of spatial sampling is necessary to represent a system’s carbon accumulation capacity and a system’s carbon stock. Currently, data on spatial variability in carbon stocks within one site or geographic location are non-existent or very limited in numbers (3 cores per system) – with some rare exceptions. This lack of data, especially on the processes behind spatial variation in carbon accumulation rates, really hinders assessment of the capacity of these systems to act as carbon sinks worldwide. Fine root growth and turnover is an important component of the carbon budget in mangrove ecosystem, but it is often not measured, and estimates rely on a very limited dataset. In this project, we are comparing traditional and novel methods to measure fine root growth and turnover in temperate mangroves stands of Western Port at high spatial and temporal resolution. Alongside these measurements, we are taking high-resolution carbon stock measurements (above ground biomass, below ground biomass and sediment carbon stock) of these currently understudied temperature mangrove ecosystems to inform sampling regimes for carbon projects.
Project 2: High resolution sediment organic matter composition analysis via Pyro-GCMS
High resolution organic matter composition analysis in sediment profiles of blue carbon ecosystems can shed insight on where the carbon stored in a sediment layer originated. This is an important and currently unresolved issue since only new carbon that has been fixed from the atmosphere via photosynthesis within a blue carbon ecosystem (autochthonous carbon) mitigates climate change. However, blue carbon ecosystems can also accumulate carbon from sources outside the ecosystem that has arrived via lateral transport (allochthonous carbon in sediment and organic matter). In this project, we are using high throughput Pyro-GCMS system to analyse newly collected and existing sediment cores for the composition of the stored carbon, and the change of the composition along the sediment recorded. This will help answer the question of where the carbon in the sediment originated from and at what point in time the carbon in the sediment becomes stable (recalcitrant). This project involves a collaborative team with members from Deakin University, Monash, University of Queensland, Southern Cross University and with CSIRO.
The second category is demonstrating and evaluating feasible on-ground activities for increasing blue carbon storage.
Restoring, rehabilitating and creating blue carbon ecosystems has the potential to sequester additional carbon from the atmosphere and therefore mitigate climate change. In this project we are collaborating with the Eco Engineering workgroup to test if nature based coastal defence solutions also have co-benefits for coastal blue carbon accumulation. We are monitoring changes in blue carbon ecosystem carbon stocks associated with two different eco engineering interventions to evaluate their blue carbon benefits.
Project 3: Planted mangroves and concrete pots
In this project we have designed 3D-printed concrete pots to plant mangroves. The pots are designed to attenuate wave energy while the mangroves establish and grow. Adult mangroves will then provide natural coastal protection against waves and stabilise the sediment. Given that this approach will either create new or restore existing blue carbon habitats we are evaluating how much additional carbon is stored in these systems because of project implementation.
This project is funded by DELWP’s Climate Change Innovation Grant. This project involves a large collaborative team of local and state government bodies, community engagement specialists and an industry partner.
Project 4: Mangroves and rock fillets
A common hybrid approach for coastal protection is the use of rock fillets (a line of rocks placed on top of each other) in front of natural or planted mangroves or saltmarsh. These rock fillets are used promote mangrove establishment and have been widely implemented in New South Wales, but there is little research in their blue-carbon co-benefits. In collaboration with NSW DPI and Southern Cross University, we are collecting data on one new rock fillet area, and using existing fillets to quantify their efficacy at accreting sediment, sediment carbon and biomass carbon.