Where
The north and northwest networks of Australian Marine Parks.
Who
Johnathon Kool and Scott Nichol, Geoscience Australia.
When
2015
Why
The ocean is a dynamic and highly interconnected ecosystem within which mobile organisms can be transported great distances. This is especially the case for the larval stage of marine biota, which can be carried hundreds to thousands of kilometres by ocean currents. Understanding the sources, pathways and destinations of marine larvae is the study of population connectivity. Connectivity is important because it allows us to identify and map regions of the ocean that have the potential to exchange biota and estimate the rates of those exchanges. For marine managers, this can be used to evaluate the potential for invasive species to spread, assess the relative importance of marine parks as source and destination areas, and understand marine parks at the system-wide scale.
How
This study developed a four-dimensional (3D x time) numerical model to simulate the dispersal of marine larvae, and applied this model to the commonwealth waters of north and northwest Australia. The model uses oceanography, bathymetry, habitat and species data to simulate the movement, collision, settlement and mortality behaviour of larvae in the water column. It represents the first fully 4-dimensional model with the capacity to generate connectivity data for semi-continuous marine environments at a continent scale. To build the model, the relevant oceanographic, physical and biological parameters of the north and northwest marine regions were used. The output connectivity data was analysed using a variety of spatial analysis and statistical techniques to determine characteristics such as dispersal trends, source and sink locations, key connectivity pathways, variability in connectivity strength and key connections that exert the greatest influence on the populations.
What did we learn?
Relatively stable connections were identified between Arafura, Kimberley, Argo-Rowley Terrace and Gascoyne marine parks. These connections can be viewed as marine equivalents of terrestrial corridors, and warrant further consideration as conservation targets. Additionally, the Abrolhos, Montebello, Arafura, Arnhem, Wessel, Limmen and West Cape York marine parks were identified as regions that dispersed much more larvae than they received, making them important source areas critical to the maintenance of biodiversity in other adjacent and connected regions.
Key connectivity pathways were mapped between several marine parks, with Oceanic Shoals, Joseph-Bonaparte Gulf, Arafura and Arnhem emerging as dominant regions in terms of their influence on surrounding populations. Linkages between Argo-Rowley Terrace, Kimberley and Oceanic Shoals were also identified as important, and demonstrate the importance of viewing these parks as part of a regional ecosystem.
What next?
It is always important to verify the accuracy of models with observation data. The modelling results from this connectivity study are best tested through strategic field sampling within and outside the marine parks of the north and northwest regions. With this will come an improved understanding of biodiversity patterns and an opportunity to further refine the model.
Related data and publications
Johnathan, K.T., & Nichol, S.L. (2015) Four-dimensional connectivity modelling with application to Australia's north and northwest marine environments. Environmental modelling and software 65, 67-78.
For more information please contact marinescience@environment.gov.au.