coastal and marine natural values of the kimberley - wwf - Australia

30. Coastal and Marine Natural Values of the Kimberley5.KEY COASTALAND MARINEECOSYSTEMDRIVERS5.1 ECOSYSTEM PROCESSESAND BIODIVERSITYThe terrestrial environment of theKimberley is linked to the coastal andmarine environment downstream. Therelatively pristine natural environmentextending along most of the Dampierlandand Northern Kimberley coastline(McKenzie et al., 2003) temperscatchment inflow, particularly during wetseason cyclones. Wetlands, forested riversand mangroves are critical to the steadycontrol of nutrients entering the marinesystem (see section 6.6) and responsiblefor sustaining primary productivity ofseagrass and benthic algae.As with virtually all ecological systems,limited availability of nutrients underpinsdiversity and species richness.Marine species nevertheless dependon local concentration of resources inthe environment, to persist. If availableresources were diluted evenly in seawater,most complex organisms would be unableto meet their energy budget to find foodand reproduce. It is the concentration ofresources and gradients of availability(Ballance et al., 1997) that create mosaicsof high and low value for differentspecies and communities.Primary producers such as seagrass,macroalgae and phytoplankton are thebasis of the food chain for herbivoresand detritivores that in turn feed morecomplex organisms higher up thefood chain. Both primary producersand consumers are dependent on aconcentration of resources, whether it benutrients from catchment run-off (in thecase of seagrass) or plankton prey forflying fish, which in turn feed Boobies.The patchiness of marine ecosystemsis essential for areas of high preyavailability and population regulationeven amongst roaming ocean speciessuch as seabirds, turtles, cetaceans andmarine fish. This mosaic is created by theinfluence of numerous physical processesat different spatial scales. Ultimately, toregulate a population at a given level,a minimum proportion of any species’population needs to find access to enoughfood at critical times of year to produceenough surviving offspring and balanceout annual mortality.Key drivers for the marine ecosystem areboth primary production and the physicalprocesses that concentrate resourcesto become ‘available’ for exploitationby marine biota. The spatial quality,availability and location of resourcepatches is what regulates populations at‘carrying capacity’.It is important to note that the locationwhere food becomes available is moreoften than not, located away fromsources of primary productivity. Twodimensionalmapping of bioregions basedon seabed ecology will overlook this. Itis also important to consider seasonalvariation, as the pressure on species andcommunities alters substantially.5.2 PRIMARY PRODUCTIONAlong the shores of the Kimberley,the predominant primary producersare mangroves, seagrass, macroalgae,sediment microalgae and phytoplanktonand corals. Each of these componentscontribute matter and energy to theecosystem in different ways. Theproductivity and total production ofthese components in the Kimberley isunknown. Mangroves contribute organicmatter to the system through leaf matter,but this input is likely to be very minorcompared to other primary producers,such as seagrass. This is despite the factthat mangroves are very important forcarbon storage.