Mapping ecosystem processes and function across shallow seascapes

Shallow sub-tropical 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 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.