Issues

• Water Quality in Tasmanian Estuaries
• Discharges to Estuaries
• Algal Blooms

• Ecological Condition of Coastal, Estuarine and Marine Habitats
• Threatened Species and Communities
• Marine Pests and Diseases
• Marine and Estuarine Protected Areas

• Wild Fisheries
• Marine Farming

• Adapting Coastal Settlements to Climate Change

At a glance

The issue

Tasmania's estuaries and marine ecosystems are some of the most diverse on earth, with many of their member species not found anywhere else. The ecology of coastal, estuarine and marine environments is important for its own sake, as well as for its key role in providing for the health and well-being of the people of Tasmania. Tasmanians benefit in a number of ways from these environments. For example, we benefit through fishing resources, aquaculture, recreation, transport, and tourism. There have been attempts at valuing the services provided by ecosystems to the economy. For example, Costanza & Folke (1997) estimated the economic value of 17 ecosystem services for 16 biomes, or habitats. The values indicate that natural coastal environments, particularly those in estuaries, are easily among the most valuable on earth. These environments also help to define the Tasmanian sense of identity, both as an island State and an island people. Over a quarter of the area of the State of Tasmania is below the high water mark.

The richness of Tasmania's biodiversity owes much to the complex coastline, offshore islands and the convergence of oceanic currents-all of which provide a wide range of environments and ecological niches. The marine environment near Maria and Bruny Islands, and the Kent Group in Bass Strait, are areas which contain an especially high diversity of reef fish species. Hundreds of offshore islands of varying sizes and remoteness are dotted around Tasmania. They offer shelter to many species, both common and threatened.

However, the significant lack of knowledge in Tasmania about coastal, estuarine and marine ecology, and the condition of that ecology creates uncertainty about how to manage human impacts.

This 'At a glance' section provides and overview of the ecological condition of coastal, estuarine and marine habitats in Tasmania. More information and references are contained in the Ecological Condition of Coastal, Estuarine and Marine Habitats Issue Report. There are four indicators presented in the Indicators section of this Issue Report. A related issue is the Water Quality in Tasmanian Estuaries.

Related recommendations are Conservation and Management of Coastal and Marine Biodiversity and Integrated Management of Catchments, Coasts and Estuaries.

Favourable news

• Measured improvements in marine habitat condition have been documented in the Maria Island Reserve-the largest of the marine reserves around Tasmania other than the Macquarie Island Reserve (Edgar & Barrett 1999). In particular, over a period of 10 years starting, from the date of reserve declaration, changes included the following: biomass of rock lobsters (Jasus edwardsii) increased 10 times; the numbers of bastard trumpeter (Latridopsis forsteri) increased 100 times (partially due to a large recruitment event in 1994, which the reserve protected and maintained); and the mean size of abalone (Haliotis rubra) increased markedly, though small abalone decreased in numbers. Other significant ecological changes are also likely to occur and continue over longer time frames inside Marine Protected Areas. In New Zealand some changes only began to occur after 10 to 15 years - such as a decrease in urchin barrens (Shears & Babcock 2003).
   
• Statewide work measuring marine and coastal biodiversity through surveys of fish, invertebrates and plants of reef habitats has been undertaken by Edgar et. al. (1997). Much of the analysis of marine habitat and biodiversity is undertaken with reference to marine bioregions. These are areas of coast and marine waters that share similar environmental, physical and climatic conditions and contain characteristic ecosystems of plants and animals (see map). The number of species recorded from over 156 sites, indicates that species richness is highest around Maria Island and Bruny Island-in the Freycinet and Bruny bioregions respectively-particularly in fish and plants. Invertebrate species richness is consistently high around the eastern and northern coasts, and the Tasmanian portion of the Twofold Bioregion has an unusually high number of fish species.
   
• In 2000, a detailed and comprehensive sea floor habitat-mapping program-Seamap Tasmania- commenced. The first series of maps from this program reveal the extent of some habitats for the first time. For example, within the Bruny Bioregion almost every stretch of coast and bay contains different communities of plants and animals, which indicates very high ecosystem level diversity.
   
• A Statewide report on the type, condition and conservation significance of Tasmania's estuaries has provided the basis for improved understanding and management of Tasmania's estuaries. Edgar (et. al. 1999) defined 111 estuaries around Tasmania. Information gathered included catchment extent, catchment geology, rainfall, size of the estuary, seaward barrier characteristics, tidal regime, salinity levels and biological data. The estuaries were classified into nine groups, or types.
   
• Catchment condition is one of the key determinants of estuarine condition. The study by Edgar (et al. 1999), noted that 24 of the 90 Tasmanian mainland catchments were considered pristine, with little human impact within the catchment. Other catchments had varying levels of impact from moderate to severe (see 'Unfavourable news').
   

Unfavourable news

• Very little is known about the condition of coastal, estuarine and marine habitats, particularly those in marine waters deeper than 40 metres, such as sponge habitat.
   
• A small number of catchments in Tasmania are severely impacted by urban development and large-scale land clearance, and many others have been moderately affected by human impacts (Edgar et al. 1999). The highest levels of land clearance, population and urban development are found in catchments along the south-east, east and north coasts of Tasmania (see 'naturalness index' map).
   
• There are 10 new coastal, estuarine and marine animal species listed as threatened under the Tasmanian Threatened Species Protection Act 1995 since the last SoE Report in 1997. They are: spotted handfish, Port Davey skate, great white shark, live-bearing seastar, two unnamed seastars, Gunn's screw shell, Chappell Island tiger snake, sub-Antarctic fur seal and the Chevron looper moth.
   
• Results of monitoring the Maria Island Marine Protected Area suggest strongly that fishing impacts on the ecology of many of the marine reef environments located outside the Marine Protected Areas (Edgar & Barrett 1999).
   
• Catastrophic losses of shell (mollusc) species over the past 150 years in the shallow, sheltered estuarine waters of the south-east have been documented (Samson & Edgar 2001). Further work by the same authors suggests that while there are many factors at work-including siltation and pollution-the pattern of losses seems to correspond to the rise, and then collapse, of the oyster and scallop dredging industries. The losses were previously undetected, which highlights the risk of the 'sliding baseline syndrome' where changes that occur over generations are not noticed and the new environmental conditions are thought of as 'normal' (Dayton et al. 1998).
   
• Many species are restricted to long narrow bands that are highly vulnerable to local impacts. For example, seagrasses and giant kelp typically only occur in waters between 1 and 20 metres deep. A number of human activities are known to impact on the extent and overall 'health' of seagrass habitats. There is evidence of a strong relationship between decreased light levels and seagrass loss in many areas around the world (Walker & McComb 1992, Dennison et al. 1993). This happens because increased sediments in the water result in reduced water clarity and increased nutrient levels. As there is evidence for increased sediments and nutrients in coastal waters (see Water Quality in Tasmanian Estuaries), there is little doubt that some changes in seagrass extent and health have occurred throughout Tasmania. This is supported by the trends in the collected data which show that maximum seagrass loss occurs in areas closest to population centres where water quality is poorer (Rees 1993). Best estimates put the extent of Tasmania's seagrass at about 1,000 km² (Jordan pers. comm. 2003). However, given the lack of detailed measurements on the extent of change in seagrass habitats in Tasmania over an extended time frame (decades), there is considerable uncertainty of the extent of change due to natural variability compared to human induced impacts (see 'Uncertain news').
   
• In south-east Tasmania, Gouldthorpe (2000) found that drainage, road works and grazing have 'substantial and significant effects' on saltmarsh ecosystems with effects measured on soil moisture, conductivity, acidity, organic soil content, percentage of bare ground and invertebrate species composition.
   
• There are various examples of ecological changes that have wider implications for primary industry, such as the effects of an increase in sea urchin 'barrens' on rock lobster and abalone fishing. In addition, ecological changes can result in serious losses of both biodiversity and natural 'services'.
   

Uncertain news

• The ecological condition of coastal, estuarine and marine environments is subject to considerable uncertainty. Apart from a few commercial species, such as lobsters, abalone and scallops, virtually nothing is known of species taxonomy, ecology, distribution and habitat requirements (State Biodiversity Committee 2002).
   
• In Tasmania, there is no set of scientifically defined estuarine and marine ecosystems or habitats (Edgar 2001). This is partly because the webs of interactions are not yet adequately understood, but also because of the dynamic nature of the environment, where species themselves move between habitats during their life cycles. In addition, seasonal and interannular variations result in constant change.
   
• The lack of Statewide information on extent and condition of coastal, estuarine and marine ecosystems for one time frame means that trends through time are very difficult to perceive. The purpose of indicators is to report on trends through time, ideally using the time of European settlement as a 'baseline' or reference date. Preferably, repeated measurements are undertaken at a time scale relevant to the management of the environmental issue (Saunders et al. 1998). In the absence of such information there are considerable uncertainties, and therefore risks, associated with management decisions affecting habitats and ecosystem diversity in Tasmanian marine and coastal waters.
   
• Estimates of the extent of coastal saltmarsh habitat derived from TASVEG 2000 indicate that by far the most saltmarsh is found in the Boags and Freycinet Bioregions followed by Bruny and Flinders. No mapping is available for Franklin, Twofold and Macquarie Bioregions. The alternative data source-the LIST map layers-underestimates the amount of saltmarsh, reporting less than half that shown by TASVEG 2000. Currently, the condition of Tasmanian saltmarshes is not well known, with limited reports available.
   
• While information about the condition of parts of the onshore coastal environment has improved considerably with detailed vegetation and geomorphological mapping, large strips of the coast are not yet mapped to that standard.
   
• A recent estimate of the total extent of Giant Kelp (Macrocystis pyrifera) is between 7 and 10 square kilometres only (Edyvane 2003). This meets the IUCN criteria for consideration for listing as a critically endangered species. However, there is uncertainty about the significance of the plant's naturally dynamic and opportunistic growth habit in response to a relatively strong variation in environmental conditions.
   
• Damage to susceptible habitats, including seagrass, caused by physical impacts, such as anchor scour, marina infilling and jetty shading is recognised as a significant problem around Tasmania (Rees 1993; Jordan et al. 2002). Some areas have been identified as having been particularly affected (e.g. North West Bay, see photographs), but no quantitative studies currently exist to provide information on the extent of the damage. However, there is anecdotal information that this can be significant in some coastal habitats.
   

• Issue Report - continued in depth