Mapping ecosystem processes and function across shallow seascapes
Shallow subtropical and warm temperate east Australian coastal lagoons and estuaries were used as case studies to develop a system for assigning functional value to shallow seascapes. Nine habitat classes (Mangroves, Sands/ Muds with Large Burrowing Macrofauna, Stable Seagrass Communities, Ephemeral Seagrass Communities, Channels, Subtidal Shoals, Intertidal Shoals, Depositional Mud Basins, Permeable Sands) and ten ecosystem processes (gross benthic production, gross benthic respiration, net benthic production, net benthic respiration, benthic dissolved organic and inorganic nitrogen fluxes, denitrification, denitrification efficiency, N-fixation and secondary production) were used to assign functional values and construct the maps. These functional value maps of ecosystem processes and overall functional value were used to identify 'hot spots' that have high conservation value. Some habitats had a high overall functional value across all 4 systems (e.g. Stable Seagrass Communities), while other habitats had a high overall functional value in some systems and a low overall functional value in other (e.g. Channels). A case study from southern Moreton Bay was used to illustrate the application of the process functional value and overall functional maps. A comparison of these maps with a map of impact (decrease in light) associated with the discharge from a wastewater treatment facility showed that areas of highest impact coincide with open water benthic habitat of medium overall functional value. Areas of low impact were mostly in areas of highest overall functional value. Comparison of the map of impact with maps of the individual benthic processes showed that the functional value of net benthic production was medium in the high impact areas suggesting there may be some loss of net primary production from southern Moreton Bay associated with the wastewater discharges. This type of impact would not have been detected by standard environmental assessments. A multiple overlay of maps of the functional value of each benthic process, the overall benthic functional value and the potential impacts would improve our understanding, and assist with the management and conservation, of shallow coastal systems.
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Eyre, B. D., A. J. P. Ferguson, A. Webb, D. Maher and J. M. Oakes. 2011. Metabolism of different benthic habitats and their contribution to the carbon budget of a shallow oligotrophic sub-tropical coastal system (southern Moreton Bay, Australia). Biogeochemistry 102, 87-110.
Eyre, B. D. and Maher, D. 2011. Mapping ecosystem processes and function across shallow seascapes. Continental Shelf Research 31, S162-S172
Eyre, B. D. and Maher, D. 2010. Structure and function of warm temperate east Australian coastal lagoons: implications for natural and anthropogenic change. In: Kennish, M. J. and Paerl, H. W. (eds.). Coastal Lagoons: Critical habitats of environmental change. CRC Press. pp. 457-481..
Functional values of different ecosystem process for benthic habitats in southern Moreton Bay. The functional value was assigned based on the quantitative contribution of the habitat to the total ecosystem for a given process. Black = high functional value, dark grey = medium functional value, light grey = low functional value, no shading = nil functional value.
Example maps of the functional value of ecosystem processes - benthic denitrification in southern Moreton Bay.
Map of overall functional value of benthic habitats in Wallis Lake. Overall functional values calculated by assigning a score to the functional value for each processes for each habitat (high functional value =3, medium functional = 2, low functional =1, no functional value = zero) (see Figure 1) and then the individual scores were added (see Figure 1). These scores were ranked highest to lowest and assigned a gradient of colours from red for the highest overall functional value to green for the lowest overall functional value.