This section reports on our best understanding for each region of the status and trends of outbreaks of diseases, pests and introduced species (including pests listed in the National Introduced Marine Pest Information System—NIMPIS), and algal blooms in the region and their relationship with human activities. These are summarised at the national level in the assessment summary.
The south-west region is overall in very good condition in relation to pests, introduced species, algal blooms and outbreaks of disease that can cause ecological imbalances. However, pest species have been documented from a number of the ports across the region, and have caused significant ecological impacts in their local areas. A large number of introduced species are recognised across the region whose ecological significance is unknown. The herpes-like virus that has seriously affected the region in past decades (see Box 6.8) appears to have now declined, and there are no obvious ongoing impacts on pilchard populations. However, there is only limited knowledge of the impact of the previous virus outbreaks on bird populations and other species that may be ecologically dependent on the pilchards. Blooms of toxic and nuisance algae continue to be a problem in a number of the estuaries and inshore waters across the region, creating substantial changes, fish kills (deaths of a large number of fish over a short period) and associated ecological impacts. When they occur, algal blooms in this region can cover large areas (see Box 6.1).
The north-west region is also in very good condition overall in relation to pests, introduced species, algal blooms and outbreaks of disease. Only two pest species are known to have been established in this region, although many (likely hundreds) of species are introduced to the region as fouling on ship hulls. The intense level of shipping activity associated with the oil and gas sector in the region has probably made a big contribution to this problem. However, few data are available on the ecological impacts of such introductions and, for now, these effects are assumed to be neutral in terms of ecological function. There are natural algal blooms in this region, but only low levels of coastal and related development that are likely to be the source of nutrients for human-induced algal blooms of any significance. Poor catchment management in many parts of the region influences sediment and nutrient input (such as in floods), but there are no data on the relationship between catchment management and algal blooms in coastal waters. Issues associated with Lyngbya (a toxic alga) are noted near Broome, possibly associated with local groundwater, urban run-off and sewage management.
The north region is also in very good condition overall in relation to pests, introduced species, algal blooms and outbreaks of disease. One pest species (striped mussel) has been recorded in the region, but is now thought to have been largely eliminated. Monitoring of the high-risk areas (Darwin Harbour) has not detected further pest incursions. The region is also likely to have many introduced species, as in other areas of Australia, and for the same reasons (including shipping activity, the aquarium trade, tourism and petroleum industry infrastructure) There are few ecological data on impacts.
The east region overall is considered to be in good condition in relation to pests, introduced species, algal blooms and outbreaks of disease. Four species of pest have been recorded in the region, in and around the ports, shallow bays and estuaries. However, the region suffers from periodic outbreaks of crown-of-thorns starfish, and there are extensive algal bloom issues in Moreton Bay and other bays and shallow coastal northern waters, including outbreaks of Lyngbya. These shallow and inshore waters of the region are considered to be heavily impacted at times by algal blooms, and their condition is considered overall to be poor in this respect. When they occur, algal blooms in this region can cover large areas. The Pacific oyster (Crassostrea gigas, endemic to Japan) has been introduced to the region for oyster farming and has spread, with a significant ecological impact in the estuaries of the southern part of the region.
Pests and outbreaks of disease have had major impacts in the south-east region and, overall, the regionwide condition is poor with respect to pests, diseases, introduced species and algal blooms. The pests noted in the region (some of which are widespread and have major ecological impacts at times) include starfish (Asterias), sea urchins(Centrostephanus rodgersii), plankton (toxic dinoflagellates), algae (Undaria, Caulerpa), molluscs (Maoriocolpus), crustaceans (Carcinus) and worms (Sabella). Port Phillip Bay has been described as one of the most invaded marine ecosystems in the Southern Hemisphere, but there are others of equal note, including the Derwent estuary. Outbreaks of harmful native species are also pervasive, mainly toxic algal blooms. The zooplankton Noctiluca (a red form of ‘sea sparkle’, often responsible for ‘red tides’) has recently become very widespread and is dominant in many parts of the region, probably displacing other forms of native species. The drivers and consequences of this phenomenon are unknown, but are of ecological concern across the region. A severe outbreak of abalone viral ganglioneuritis has affected abalone in several parts of the region, with serious ecological consequences (Box 6.8, p. 428).