G.A.M. Scott, T.J. Entwisle, T.W. May & G.N. Stevens
Environment Australia, May 1997
ISBN 0 6422 1399 2
Timothy J. Entwisle
Algae grow almost anywhere there is water, no matter how transient. They are most abundant and diverse in oceans, lakes, ponds, streams and other wetlands, but they also colonise bark, leaves, rocks, soil, snow and even animals. In all habitats they are important primary producers. Phytoplankton is the basis of food chains in fresh- and salt-water and is therefore of crucial significance in the biosphere as the principal C-fixing and oxygenating agent. In soil crusts, algae are major N-fixing components and, with lichens and bryophytes, important in colonising and binding the substrate. Throughout the environment, algae provide food and habitat for a range of organisms.
Cultures of non-marine algae are already an important source of B-carotene (and other pigments), glycerol, lipids and some vitamins, and there is great potential for the production of antibiotics and pharmaceuticals. Algae are an important food source in the culture of freshwater fish and crustaceans. In rice fields, blue green algae improve soil fertility through N-fixation, and in sewage treatment algae can enhance the oxidation process. Further exploitation of non-marine algae is anticipated and it is important that the available genetic diversity is maintained.
The non-marine algal flora of Australia has a unique character, including as it does many endemic and distinctive taxa. Each new habitat or region that is sampled reveals more surprises for Australian phycologists (algal specialists). Unfortunately, algal habitat is being destroyed or altered at a far greater rate than species are being discovered. Australian wetlands, ranging from lakes and rivers to swamps and ponds, are seldom safe havens for algae.
This overview of the conservation of non-marine algae comes at a critical time. Habitat, particularly aquatic systems, must be better managed, and our efforts at understanding the diversity and ecology of Australia's intriguing algal flora need a strong boost.
Australian inland waters were little explored scientifically for algae until the 1960s (Wetherly & Williams in Luther & Rzóska 1971), so there are few long-term data on the inland algae. Any conservation of algal species or communities has been fortuitous. In Victoria, for example, Crown water frontage reserves encompass almost the entire coastline, nearly 1000 rivers and creeks, and more than 250 lakes (about 22 000 km of river; an area of some 87 000 ha.). Some 15–20% of lake fringes and 30–40% of major rivers have been sold. Of course, the reserves have been cleared, grazed and generally altered. The squatting invasion of Australian land hinged around unrestricted access to water resources (Clark 1989 for Victoria). Squatters 'judiciously improved waterholes' (Clark 1989): stream beds were dredged, simple weirs constructed and surface run-off captured before it entered streams.
Grand schemes were devised with little consideration of the native flora and fauna (e.g. converting Lake Corangamite into a freshwater lake; an 800 km channel from the Wimmera River to Portland; Clark 1989). Thankfully, most were not implemented, but clearly inland waters were considered for exploitation. Swamp drainage for housing and farming, for example, is an important part of our heritage and continues today. In Tasmania, by 1980 most large natural wetlands and waterbodies had been drowned, and almost all large rivers modified for hydro-electricity (Kirkpatrick & Tyler in McComb & Lake 1988).
Gold mining required water races and many minor dams, and streams were diverted so that their beds could be worked for gold (Clark 1989). Alluvial digging modified streams by excavating, and surface mining resulted in loss of topsoil into waterbodies. Timber was harvested to construct races and valley slopes were stripped. Water-wheels and sluicing for larger mines further damaged streams. After such disturbances, streams in auriferous regions are likely to be nothing like they were 150 years ago.
Other early impacts on aquatic habitats included salt harvesting, secondary industry (e.g. water driven flour-mills, scouring and cleaning wool, energy sources), water recreation, flood controls, waste disposal and transportation, and salination through rising water tables (Clarke 1989).
Historical aspects of the collection and study of non-marine algae in Australia can be found in Ling & Tyler (1986), Tyler & Wickham (1988), Entwisle (1990b) and Entwisle (1993). The legacy is extremely patchy in terms of the groups of algae studied as well as the areas and habitats sampled. The algal flora of non-marine Australia is only partly documented, and the abundance and conservation status of most taxa are based on conjecture. There is little history of algal conservation.
Project Aqua and other listings
In 1971, 20 lakes were listed in Project Aqua ('an international effort to conserve as scientific reference localities a number of natural waters scattered throughout the world', Bayly & Williams 1973) as worthy of conservation. These lakes included a range of algal communities but were certainly not chosen to provide the best representation of algal species in Australia. There has been no follow-up survey work and no monitoring of changes to catchment use (e.g. water regime, grazing) so this listing is unlikely to have much conservation value.
The Australian National Parks & Wildlife Service compiled a list of Australian wetlands for inclusion in the Convention on Wetlands of International Importance, 1971 (Ramsar Convention). This convention was designed primarily as a way of conserving water fowl habitat, but wetlands can be included on the basis of their rare or threatened fauna or flora (Michaelis & O'Brien in McComb & Lake 1988, pp. 167–177). Whether such a listing assists the conservation of any biota is yet to be determined. Other listings exist, such as the Register of National Estate (under the Australian Heritage Commission Act 1975), but without fundamental information on algal diversity and ecology such listings conserve important algal communities only by chance.
This system conserves some inland algae by default. It was developed in Victoria based on the Wild and Scenic Rivers concept used in the United States of America (Victoria, Land Conservation Council 1989). The aims of the Heritage River Program are to:
- protect those rivers and streams that essentially remain in their natural state;
- ensure that rivers and streams of special scenic, recreational, cultural, and conservation value are maintained in at least their present condition; and
- ensure that representative examples of all stream types in the State are protected.
The program applies to both public and private land. There is a range of categories to allow for managing waterways of recreational, scenic, conservational or cultural importance. Nearly all references to the flora concern riparian vegetation-trees, herbs and so on. Sites of botanical importance include mainly riparian species or some aquatic vascular plants. Nevertheless, given the appropriate information, a scheme like the Victorian one could presumably accommodate the conservation of aquatic algae. As far as I am aware, no other State has such a program.
Almost no direct legislature or research has been directed towards the conservation of freshwater algae in Australia and we must look overseas for ideas and guidance:
'… contamination of water resources continues to increase in much of the world. There is some evidence of improvement in industrial countries. Overall, monitoring of water quality is inadequate and control measures are weak' (World Resources Institute 1990).
In The Netherlands, for example, there has been a decline and degradation of formerly algal-rich waters, even in protected nature reserves (Heimans 1969). In the United Kingdom, the high profile Nature Conservancy Council has shown little interest in freshwater algae (B.A.Whitton, pers. comm.), but a least the notion of conservation of microbes and smaller plants is gaining ground in Britain (Boon et al. 1992). In 1991, the charophyte Lamprothamnium papulosum became the first non-vascular plant to be given legal protection in Britain (Moore 1991). This coastal species is now under consideration for listing as a protected species in Appendix I of the Berne Convention, which includes the countries of Scandinavia and the European Economic Community.
Throughout Europe, the recognition of Sites of Special Scientific Interest (SSSI) has been used to alert the public to important habitats. There are no associated restrictions on use but it is up to the owners and users of the land to bear in mind the value of such sites. Such a system relies on education rather than regulations, and it could be compared to the Land for Wildlife system in Victoria. To date, algae have not been considered in the selection of SSSIs. Occasionally, however, algae get a passing mention when sites of significance are considered. Malham Tarn, the only upland marl (lime-bearing soil) lake in Britain, is described by Fryer (1991) in a 'Classic Sites' series in the journal Biologist. Cladophora balls, produced by algal filaments rolling into up to cricket-ball-sized spheres, are restricted to alkaline, usually marine and brackish water. They are mentioned as one of the intriguing biological aspects of this so-called 'classic site'. There is also mention of a flagellate called Ochromonas malhamensis.
In Germany, freshwater algae have recently been treated as part of the flora worthy of conservation. Historical analyses of inland floristic records indicate 'drastic impoverishment in the red algal vegetation' following changes in river flow, current velocity and eutrophication and pollution (Friedrich et al. 1985). As is the case in Australia, however, 'known records often reflect rather the activity of interested persons than the reality' (Friedrich et al. 1985). A similar pattern, and qualification, holds for other freshwater algal groups in Germany (Gutowski & Geissler 1987). A Rote Liste of German plants includes charophytes, brown algae and red algae, all macroscopic algae from freshwater. The list of red and brown algae includes all known German freshwater members of these groups (Freidrich et al. 1984; Geissler 1988) and a similar list exists for the Berlin area (Geissler & Gerloff 1982). Geissler and co-workers (e.g. Weddingen & Geissler 1980) continue to decry the lack of good taxonomic distributional, frequency and ecological data for freshwater algae and the resulting difficulty in making meaningful estimates of losses to the algal flora in Germany.
4.3.1 Taxonomic scope
Over 2800 species (and a further 1300 infraspecific taxa) of algae have been reported from inland (non-coastal) Australia (Day et al. 1995). Taxonomic revisions will certainly show that many of these names are unnecessary (i.e. they refer to the same taxon), but conversely, the number of undiscovered taxa could be equally high. Worldwide, there are something like 27 000 described species of algae; maybe half of these occur in inland waters.
General accounts for the identification of non-marine algae are available for only some groups of algae and often for only limited areas. The following are useful starting points for those trying to identify field collections: Baker (1991, 1992) for common toxic blue-green algae; Ling & Tyler (1986) for microalgae in northern Australia; Entwisle (1990a, 1994) for macroalgae in south-eastern Australian streams; Wood (1972) for Charophytes; and Foged (1978) for diatoms of eastern Australia. References to more specialist literature can be found in the above accounts. A checklist of all names of freshwater algae reported from Australia (Day et al. 1995) is now available, but it is a comprehensive listing rather than a census. It is a useful starting point for checking apparently new records but is not nomenclaturally or taxonomically up-to-date (nor was it meant to be). Tim Entwisle, Jason Sonneman and Simon Lewis are preparing a colour photographic guide to the 'conspicuous' genera of freshwater algae in Australia (available early 1997). Dr Peter Tyler and colleagues are preparing an illustrated book on the freshwater algae, as well as an interactive key. Such publications will assist the discovery and documentation of our non-marine algal flora.
Although it is known that some taxa are definitely uncommon because of widespread sampling for the taxon and/or the distinctiveness of the taxon, good distributional data are available for very few species.
As an example, of the 364 taxa of macroscopic algae reported from inland waters in Australia, 70% have been reported from a single locality (and collected only once), 13% from two localities and only 17% from more than two localities. To interpret these figures, the following qualification needs to be borne in mind: when any group of macroalgae has been comprehensively revised (only two genera to date), most early records are found to be misidentifications or result from too narrow a species concept (most names are now considered to be synonyms of more widely distributed taxa). On the other hand, work on the freshwater red algae in recent years (including examination of European type material), indicates that more taxa are endemic than was indicated in earlier papers on this group (e.g. Entwisle 1989b). In addition, although some Australian taxa may appear morphologically very similar to European taxa, it is possible that 'comparative iconography' (sensu Ling and Tyler 1986) is too coarse a technique to unravel the relationships between Antipodean and European algae. The status of most of the 250 or so names of macroscopic algae reported from a single locality cannot be assessed until more collecting has been done (to get good distributional data) and extensive taxonomic research validates the various records (where possible). From a scientific point of view, it would seem advisable to treat all records at face value until proven otherwise. Where conflict arises with values of a habitat other than scientific, the reliability of the name can be assessed on the basis of current information and specialist collecting in the area.
For reasons of practicability, 1950 has been chosen here as the starting date for listing taxa as rare, threatened or endangered. This eliminates many unvouchered (records not represented by a good quality specimen in a reputable herbarium) and poorly described taxa of early this century. Undoubtedly some of these warrant protection (recent studies have shown that workers such as Playfair were capable of being very astute observers), but to list them all would make the list even less workable. As it is, most taxa listed have been described from single collections from single localities as part of limited sampling of isolated areas. Few studies have attempted to collect widely and survey the range of particular species.
4.3.2. Provisional lists of rare or threatened non-marine algae in Australia
Given that some 70% of freshwater algae are likely to be recorded from one locality only, the vast majority of species could be considered (naively) to be rare. Therefore, two lists are provided in Appendix B: the first includes those few taxa that are known to belong to categories X, E, V or P in the ANZECC system; the second includes those taxa that are poorly known at this stage. The second list includes taxa reported to be rare or restricted in distribution in recent years. Since the year 1950 has been chosen as a convenient starting date to exclude poorly-known taxa, the list is undoubtedly misleading in terms of number of species. The list is presented as a starting point for discussion and, in general, overseas literature has not been consulted to check whether some taxa have since been recorded. Similarly, not all references to the taxa in Australia are cited.
4.4.1 Aquatic algae
Paerl (1982) and Reynolds (1984) provided good reviews of the factors limiting algal growth in freshwater. For a local perspective on the processes that affect aquatic biota in general see McComb & Lake (1988, 1990) and Whigham et al. (1993). Such information should be consulted if a potentially threatening process has been identified. McComb & Lake (1988), in particular, is an excellent resource for regional information on threatening processes and future needs.
Modifications and 'improvements'
(see also Lake 1987)
Dams built to supply potable water, to irrigate pasture or crops, to control river flooding or to provide hydroelectric power, alter the flow and flood regime of all waterways downstream. Artificial lakes will have different limnological characteristics (e.g. depth, water mixing, temperature, salinity) from the natural lakes of the area. Such lakes and dams alter the frequency and amplitude of water fluctuations downstream: e.g. small lakes near Gordon River have been adversely affected by the Gordon River dam (Kirkpatrick & Tyler in McComb & Lake 1988, pp. 9–10). Impoundment of water is also a major factor leading to blue-green algal blooms. Most Australian surface waters are artificial, often with high inorganic turbidity, and, due to our climate, become stratified in summer (i.e. layers of warm water above cooler layers). These conditions are ideal for surface scums of bloom-forming algae. Such scums must alter the community structure of the entire waterbody and thus threaten the viability of some algal species.
Floods are important in regulating the growth of certain species and in particular in controlling the growth of algal weed species (e.g. Entwisle 1989c). They probably also contribute to the overall availability of nutrients. In some systems, flooding can lead to the development of temperature-stratified lakes which can alter algal diversity (Tyler 1981). When dams are built, or rivers regulated, the timing and quantity of water release and the flow modifications can be adjusted to 'benefit' the aquatic ecosystem. Reservoirs may also help conserve some species if the reservoir catchment is well-managed. Parting Creek (Tas.), for example, is a reservoir colonised by endemic algae from nearby coastal lagoons.
Some algae are adapted to particular flow rates in streams: flowing water may be required for the exchange of gases, nutrients and waste products, but always balanced with the ability of the alga to remain attached to the substratum in swift-flowing water. Different species have different requirements. Changes to flow rates may alter biotic parts of the habitat, e.g. if inundation increases, the flowering plant Typha will increase in abundance (the effect of this on algae is not known).
Canals linking different drainage systems may lead to genetic integration of previously separated populations, and different sorts of competition. Such river 'improvement' is not common in Australia. Drainage of wetlands, however, is widespread and can cause a major loss of aquatic habitat favourable for aquatic algae. In northern Queensland, for example, some 20% of wetlands were drained and/or filled between 1983 and 1991.
Pollution and eutrophication
(see also Bayly & Williams 1973)
Aquatic habitats worldwide have been polluted by humans for hundreds of years. The Netherlands provide a text-book example of the impoverishment of an algal flora in a range of forest and moorland pools since the turn of century. The causes of the dramatic reduction in community diversity were and still are: eutrophication and pollution due to surrounding arable land and pasture, and acidification and oligotrophication of some sites due to air pollution (acid rain can have complex effect on desmids; Coesel et al. 1978, fig. 4). Such changes have occurred worldwide but have been seldom documented. Even when water quality improves, aquatic biota do not necessarily return to their original diversity and community structure (e.g. Dandenong Creek, Vic., where invertebrate communities have not recovered in line with water quality). Habitat structure and flow rates must be also considered.
Sewage outflow or seepage into streams alters the water quality unless it has undergone tertiary treatment (removal of solids – primary treatment, degradable organic wastes – secondary treatment, and nutrients and other contaminants – tertiary treatment). The impact of such outflows depends on the size of the receiving water body, its retention rate and the rate of sewage inflow. Eutrophication may also come from a range of less obvious sources, e.g. the build-up of gull or duck droppings (guanotrophy) in recreational areas; aerial ash from industrial areas forming microscopic balls of slag in pools and lakes etc.
Pollutants that may affect algal diversity and abundance include inert materials (e.g. coal dust, wood pulp) which may alter the available substratum and light; inorganic poisons such as copper, lead and acids which are poisonous to some aquatic life; and organic trade residues which vary in their impact depending on the rate of breakdown and the breakdown products.
Organic poisons such as herbicides and pesticides may enter waterbodies from run-off or be wind-borne. Such poisons may either kill algae directly, or alter the ecosystem by killing other plants and animals and thus have an impact on algal species. Pesticides alter the plant/animal balance, and fertilisers enhance the growth of weed species. Toxic algal blooms are one product of this mix (although blooms have been regular occurrences in many of our older reservoirs, particularly when water levels are low). Sugar cane production leads to high water turbidity and frequent algal blooms (hence is detrimental to the native algal flora). Non-poisonous salts, e.g. brine wastes from oil extraction, can also alter the species composition of a water body.
Hot water from power stations or manufacturing plants is a threat to many native species. Most algae tolerate only a limited range of temperatures, and any difference in water temperature between input water and the stream or lake water could alter the structure of the aquatic community.
As yet there are no nuclear power plants in Australia, but radioactive waste may be important near mining areas in northern Australia. Biota can accumulate radioactive elements at a much higher level than the surrounding water.
Catchment land use
Degradation of water quality and/or quantity upstream will affect all downstream habitats to a greater or lesser extent. This has become clear in recent years with the blue-green algal blooms in the Darling River.
Urbanisation usually leads to a deterioration in water quality and marked changes to water quantity, and hence the algal flora. Interestingly, a study of the Yarra River outside Melbourne revealed that nearly all species found in protected catchments upstream were also present in the semi-urbanised stretches (Entwisle 1989b). On the other hand, there were differences in the abundance of taxa, and some patches were far more depauperate in species (and with more weed species). Urbanisation can affect aquatic communities in a number of inter-related ways, making generalisations difficult.
Clearing land and applying fertilisers and pesticides has altered the aquatic habitat of most catchments in Australia. Land clearing near streams alters the amount of light reaching the water and its temperature. It also alters the amount of silt entering the water (affecting light penetration as well as nutrient content). Intensive grazing by introduced or native animals has compounded the effect through animals muddying water, defecating near banks and trampling habitat. The increased turbidity can favour blue-green algal dominance because most of the weedy (bloom-forming) blue-greens float to the surface while other algae suffer from light deprivation. Feral animals have had an impact on wetlands in northern Australia, altering vegetation structure around water bodies, eroding banks, and allowing salt water intrusion.
Run-off patterns are generally altered by grazing and land clearing, usually resulting in more extreme fluctuations in water level (the opposite effect of modifications, except where these result in irregular massive flooding when water overtops the weir wall). Drought tolerance of algae is extremely variable and depends on the species concerned. Some algae produce resistant spores; others may survive many months of desiccation in the vegetative phase; many soon die if deprived of water (e.g. Brook & Williamson 1990).
Farm dams have provided aquatic habitat for algae where previously there was none. They provide stepping stones for the spread of algal species, but generally the common or weedy taxa (i.e. those that dominate a community to the exclusion of other, often rarer taxa). Maintaining 'good' farm dams is essential and is in need of scientific study. Initial observations suggest that extensive macrophyte (aquatic flowering plants) growth helps to maintain a diverse array of algal species.
The effects of forestry on aquatic algae have been little studied. In one catchment studied in Australia (Entwisle 1989b), there is circumstantial evidence to suggest that even the most stringent forestry practices alter the macroalgal communities in streams, with weedy species introduced and some indigenous species lost. After 5–10 years, indigenous species were found to return but the presumed weeds were not dislodged. The application of fertiliser following logging would certainly alter the algal composition of streams draining the catchment.
The salinity of water bodies in southern Australia is of great concern. The colonisation of 'typical brackish-saline diatom communities' in streams and rivers well beyond the sites of marine influence in south-western Australia attests to its effect on native algal communities. Conversely, the desalination of salt-stratified lakes in south-western Tasmania has resulted in the loss of some algae (Croome & Tyler 1988). This resulted from damming the Gordon River upstream for hydroelectric power.
Introduced fish, e.g. Salmo trutta (Trout), Cyprinus carpio (Carp) and Misgurnus anguillicaudatis (Oriental Weatherloach) alter aquatic habitat. Trout have been shown to limit the range of a Tasmanian shrimp which would in turn affect the aquatic flora. Carp can muddy water and increase mixing, thus destroying the conditions favourable to desmids. In the mid-seventies, lagoons in the Upper Gunbower area in Victoria were once rich desmid habitats (i.e. the water was clear or coffee-coloured with humus). By the end of that decade, the waters were clouded by carp and only flagellates were found. The long-term effect of carp and weatherloach on the native algal flora has not been assessed.
The spread of weedy plant species – algal or otherwise – acts, as it does on all natural communities, by reducing diversity and so threatening any restricted populations. Examples of community-destroying weeds are Salvinia molesta (Salvinia), Brachiara mutica (Para Grass), and Eichhornia crassipes (Water Hyacinth). Green algae such as Cladophora and Stigeoclonium and any blue-greens forming blooms almost certainly replace more diverse native communities. Whether such algae are native or introduced is unlikely to ever be known.
Terrestrial (riparian) weeds such as Rubber Vine (Cryptostegia grandiflora) in Queensland can alter light regimes by shading a stream. Mimosa pigra (Giant Sensitive Tree) is a serious weed problem in the wetlands of northern Australia, where, in altering the vegetative community structure and therefore light and water levels, it affects algal growth.
Algal blooms must have a negative impact on other algal taxa through light and nutrient competition (as well as secondary effects following death of the algae). Impoundments and high nutrient levels will generally favour such blooms (as discussed above).
4.4.2. Terrestrial algae
Threats to terrestrial algae will be similar to those for lichens and bryophytes, although changes that alter the biomass or species composition of other non-vascular plants may not have the same effect on algae. As an example, the application of a range of herbicides to soil has been shown to cause total suppression of algal growth, although fungicides do not seem to affect algae (Wegener et al. 1985).
4.5.1 Habitats well-conserved
Any acidic, coloured, non-eutrophic waters are good for phytoplankton diversity, and many are well-conserved in State and national reserves. The Western Australian Environment Protection Authority has a policy to conserve wetlands, e.g. on the Swan Coastal Plain, and other States have similar declared aims. Some of the richest known phycological sites (in terms of new species or total numbers of species) are in National Parks (e.g. Fraser Island dune lakes, coastal lagoons within south-western Tasmania World Heritage area, billabongs in Alligator River Region of Kakadu National Park) (Tyler & Wickham 1988). But the value of National Park and World Heritage status to freshwater algae is dubious when the history of Lake Pedder in Tasmania is considered.
The following are examples of well-conserved algal habitats outside National Parks and World Heritage areas:
- Yan Yean Reservoir (Vic.): Although artificial, this water body was colonised in the early days from natural lakes nearby (most of which are now gone), and most species reported in 1905 are still there. Reservoirs are often good refuges for freshwater algae and may be worthy of conservation management. If carefully managed, they can be safe havens for algae, but managers must be aware of and able to deal with threats to water quality and habitat.
- Upper Yarra, Maroondah and O'Shaughnessy reservoir tributaries (Vic.): These catchments provide excellent habitats for macroalgae and the catchments are well protected.
- Barren Grounds Game Reserve (N.S.W.): This reserve includes streams supporting a healthy and intriguing macroalgal community. It seems well protected.
- Water storages in Snowy Mountains Hydroelectricity Scheme (N.S.W.): Although artificial, these water bodies mostly support a diverse range of algal species.
- Parting Creek (Tas.): A habitat good for microalgal diversity but with absolutely no conservation status. Luckily it has been well managed to date.
- Lakes of the Picton Massif (Tas.): This region includes habitats good for microalgal diversity and apparently is well conserved.
- Swamps and lagoons around Darwin (N.T.): These water bodies appear to have a similar flora to the rich Alligator River localities sampled by Ling & Tyler (1986). Currently they are not under threat.
4.5.2. Habitats under threat or lost
McComb & Lake (1988) included information on the wetlands of each State and Territory that are under threat or not adequately conserved. This book should be consulted for specific localities.
In spite of the above examples, all aquatic habitats outside protected catchments or reserves are potentially threatened. In Tasmania, the only State where algal values have had any real weight, the following sites outside National Parks are important algal habitats: lagoons in the south-east Cape, all those along the south and south-west corner, those near Strahan, some near St Helens, those at the south end of Lake St Clair, and the meromictic lakes of the lower Gordon River (Kirkpatrick & Tyler in McComb & Lake 1988). Habitats within National Parks are not always well conserved. Lake Pedder once contained a number of species restricted to mountain lakes in Tasmania. Distrophic waters (high organic material, low oxygen, usually acidic and usually with poor species diversity) such as those of Lake Pedder are not common outside Tasmania and this habitat favours many intriguing phytoflagellates and red algae. It would be instructive to compare samples collected before the flooding with modern day collections.
Many other aquatic habitats in Australia must be considered poorly conserved but data are lacking on their algal communities. Inland natural aquatic habitats (e.g. Dalhousie Springs in central Australia) are poorly studied and therefore potentially under threat. Lowland rivers, lakes and ponds have suffered most from human impact, whether through pasture improvement or urban development (natural reserves tend to be in mountainous areas and mainly include only the headwaters of streams). Undoubtedly, algal species have been lost from such habitats. Drainage, clearing and altering the hydrological regime have changed or altered a large proportion of wetlands worldwide. Many aquatic habitats are therefore under severe threat.
4.5.3. Important habitats for species diversity (ANZECC Critical Habitat)
All available evidence suggests that the survival of many of Australia's endemic algae depends on the maintenance of native catchments or of reservoirs in native catchments. The following habitats are those known by the author to be important, but the list should by no means be considered definitive. Any native catchment should a priori be considered critical habitat.
- Coastal lagoons: These can support a large variety of rare, uniquely Australian algae. Rich habitats are found in south-western Tasmania, some Bass Strait islands (where agriculture has intruded) and Fraser Is. (Qld). Coastal lagoons near Peterborough (Vic.) and in the Bay of Islands reserve (Vic.) have some elements of this flora. Dr Peter Tyler has published widely on the outstanding values of coastal lagoons (see e.g. Bowling et al. 1992, Tyler 1992).
- Pristine acidic streams: These support a diverse macroalgal flora but are susceptible to modification, eutrophication and river engineering.
- Coloured (humic) lakes: These desmid-rich habitats are uncommon in most of Australia.
- (Naturally) alkaline streams: Such habitats are uncommon in Australia. They are species-poor but because of restricted occurrence may support rare taxa.
- Freshwater billabongs & lagoons: e.g. Alligator River system in Northern Territory. These are rich microalgal habitats, particularly for desmids. Their limnology is poorly understood and any change in flooding regime may alter algal flora.
- Reservoirs: Well-established reservoirs with protected catchments provide ideal habitat for many microalgae, particularly desmids. Such catchments have world-wide value given the paucity of such systems overseas.
4.5.4. Other algal habitats
Most of these habitats have been excluded from the above list only because of the absence of any algal studies.
- Saline lakes & marshes: e.g. Basalt Plains of Victoria. Species-poor but with distinctive flora.
- Eutrophic streams: Species-poor, but sometimes native taxa remain and, because of shortage of oligotrophic streams in some areas, they may represent the last fragments of a previously wide distribution.
- Lowland rivers: Very few in pristine state; understudied.
- Freshwater stratified lakes: Studied in Tasmania; more floristic work needed.
- Colourless lakes: More floristic work needed.
- Freshwater ponds (ephemeral): Little studied.
- Eutrophic lakes: Such habitats may maintain some species of naturally alkaline waters.
- Thermal springs: Only one thermal spring has been studied in any detail, resulting in a few interesting algal discoveries.
- Freshwater bogs & marsh: Rich desmid habitats (e.g. in Sphagnum).
- Tree holes & hollows, pitcher plants, etc.: Not studied.
- Puddles & rock pools: Little studied.
- Farm dams: May allow taxa to extend their 'natural' range.
- Soil: e.g. cryptogam mats in dry country. Species composition mostly unknown, but of great economic importance. The unpublished work of Parbery (1970) is a rare example of algal studies in such a habitat.
- Rock surfaces: Not studied.
- Rock (internal): e.g. Australian Antarctic Territory where some algae live within rocks.
- Tree trunks & branches: e.g. Trentepohlia and related species which have a very similar habit to lichenised fungi.
- Leaves: Some algae penetrate into leaves (particularly in wet forest).
- Animals: Certain species grow within fur, etc. on outside of animals; little studied in Australia.
- Lichens: The photosynthetic portion of lichenised fungi. Usually few species of algae involved but not studied in Australia.
- Snow: Species-poor but limited habitat in Australia.
4.6.1. Impediments to improved conservation
It should be stressed that the impediment to conservation is not, in the first instance, lack of legislation. In Victoria, for example, a freshwater alga can be nominated under the Flora and Fauna Guarantee Act 1988 and would have an equally good chance of being listed if it met the same criteria as vascular plants; the same is true of Western Australia under the Wildlife Conservation Act 1950. Unfortunately, we do not know enough about any Victorian (or Western Australian) taxon to propose listing. It is lack of knowledge that impedes conservation efforts through legislation. The following list reflects this view: although the items are prioritised, many are interconnected and all might be considered equally important.
- Lack of trained personnel. The outlook is bleak. Only two freshwater algal taxonomists have ongoing positions. An active research group is studying estuarine and marine diatoms in W.A. and it is possible that freshwater diatoms may receive some attention in future years. All other research on inland algae is focused on their weed potential. Deakin University, Warrnambool, and the Royal Botanic Gardens, Melbourne, are currently the foci for freshwater algal systematics research, but in the longer term the study of microalgae could be classified as Endangered. The one 'permanent' specialist will retire within 5 years and then freshwater microalgal taxonomists are at risk of becoming extinct in Australia. The study of macroalgae could be classified as Vulnerable, with one specialist spending a maximum of 25% of his time on freshwater algal research. Students and collectors are sporadic, and future progress in this field may be exceedingly precarious.
- There has been no checklist or census of non-marine (aquatic, terrestrial & aerial; saline, brackish & freshwater; macro- and micro-algae; benthic and planktonic) algae from Australia. This impediment has been partly rectified by the bibliographic checklist of Day et al. (1995).
- Few distributional data are available.
- Historical changes are hard to assess and there have been few detailed long-term studies (but see Tyler and Wickham 1988). Herbarium material of many taxa is difficult or impossible to classify and species concepts cannot be evaluated. In general, herbarium holdings are poor (see Appendix A).
- There has been no long-term sampling of habitats to look at loss of species and to elucidate the full algal flora. Apparent rarity can be influenced by the sampling technique and timing. For example, in 1969 Micrasterias jenneri was found in great abundance in a surface plankton tow of a lake in the Mount Kosciusko region (Powling 1970). Other desmids species were also common. A similar tow in the same lake the following year included no desmid cells at all. Powling (pers. comm.) has hypothesised that high winds in the first year churned up the water and pushed the relatively large, flat M. jenneri near the surface (the same would be true to a less extent for the other desmids). Under less windy conditions (as in the following year) the desmids settle on the bottom of the lake, below the level sampled by a surface plankton tow. Spatial fluctuations may also occur. In a south-eastern Queensland study of macro-invertebrate communities, the species composition varied between tributaries within the same catchment. Few similar studies have been carried out for algae but such information is vital for adequate conservation.
- The taxonomic uniqueness of many reported taxa is unclear. That is, uniqueness is difficult to assess: of 530 taxa reported from a catchment in the Northern Territory, 66 were considered new to science or could not be identified. Most of the reported species were reputedly cosmopolitan.
- There is a lack of published conservation status information for most species.
- No adequate culture collections of non-marine algae exist in Australia. Some collections exist in universities and CSIRO but their holdings fluctuate with the interest of researchers and there is no listing of what is available. Ex situ conservation by means of extensive culture collections would be a practical adjunct to habitat conservation. Such collections not only maintain germplasm, they also provide an additional resource for identification and research (for methods suitable for storing algal germplasm, see Jong 1989).
- Little research has focused on how algal communities function in inland waters and how they are affected by change. Work in the Yarra River catchment in Victoria has shown that native species may return after severe disturbance, but some algal weeds will remain (Entwisle 1990a). The community structure is altered, and returning habitats to their 'natural' state is unlikely to be wholly successful, although it may help to conserve individual taxa and such research should be encouraged.
- Urban and rural development has dramatically reduced habitat. In all countries (e.g. United Kingdom; Whitton 1974), small ponds and streams in lowland areas have been drastically reduced or altered. Algae of such habitats may well have become extinct. In Australia also, few lowland rivers, streams and lakes remain in a near-natural state (e.g. areas such as the volcanic plains in Victoria have few remaining native aquatic habitats).
- 'Inclusion [of a wetland] in a reserve or other protective zone does not ensure an appropriate water supply, which may be affected by often-distant activities in the catchment' (Pressey & Harris in McComb & Lake 1988, p. 49). Integrated catchment management is essential for the conservation of any aquatic organisms.
4.6.2. Methods of conservation
Any alteration to the quality and quantity of water bodies will alter the composition of the inhabiting algal flora. Successful conservation must rely on appropriate catchment management. In most cases, 'natural' water regimes (including regular or irregular flooding and drying) should be maintained, and input of water of a different quality (e.g. polluted or saline) should be minimised. A fully protected catchment (where natural terrestrial vegetation clothes all parts of the basin) would provide ideal conservation of native flora.
To conserve a flora poorly documented and poorly understood (in terms of ecology), research management should:
- concentrate on the habitats of the elite group of species that are well known (i.e. their commonness or rarity is better understood), and/or
- investigate and locate new taxa to gain a better understanding of the composition of our non-marine algal flora and its requirements.
The first approach will stimulate interest and provide tangible results for managers, the second is necessary for any serious attempt at conserving our native algal flora. Both avenues should be explored. One reviewer considered option (i) to be of higher priority since just about all known endemics are restricted in distribution and such (restricted) sites are easier to conserve than vast tracts. Also, most known sites are already in National Parks or World Heritage Areas. Given that agriculture and urbanisation destroy the 'elite' flora, there is an urgency to conserve the communities we know about. The reviewer did accept the value of option (ii) and suggested that it should be a parallel path, with a particular focus on what we already know (e.g. the search for algae in rich coastal lagoons could be widened to Gippsland, Vic., and Cape York, Qld). Sites can also be chosen based on comparable studies of rotifers and protozoa: it appears that 'what is good for endemic algae is good for other aquatic biota'.
4.6.3. Future priorities for research and management
Current management and conservation programs for wetlands and rivers may incidentally conserve algal diversity but there are some critical priorities for research and management. They have been grouped in priority order, but a mix of various approaches is recommended.
- All wetlands and waterbodies outside the national and state reserve system are vulnerable and as many as possible should be protected either by legislation or at least by some sort of 'awareness program': e.g. Sites of Special Scientific Interest, Land for Wildlife or the Heritage River schemes of Victoria.
- Leave sizeable buffer zones of natural vegetation around water bodies to protect aquatic systems from agricultural and forestry in catchment. Research is needed to determine an adequate size.
- Limit modifications and channel engineering in streams and rivers wherever possible.
- Train and employ freshwater algal taxonomists/identifiers. It will be extremely difficult to find suitably trained staff for the survey work proposed below since algal identification is a relatively specialised field and requires access to and ability to use high-power microscopes. It is unlikely that even a minor demand could be met by our current resources. In 3–6 years there is the very real possibility that only one research group in Australia will be concentrating on floristic and/or taxonomic research on the inland algae. This remaining group is likely to be below the critical mass needed for effective, long-term research. This is a critical situation.
- Before altering catchment management in any way, the algae of the streams, lakes, ponds and terrain should be surveyed. In particular, dams and forest clearing are likely to have major impacts on non-marine algae. It is true that surveys will inevitably turn up a few new records of species due to paucity of previous collecting, but apparent rareness should be a sufficient reason for at least re-examining management proposals and should precipitate further sampling for the organism in nearby areas.
- Building on point 5, we should include surveys of neighbouring or similar catchments in all impact surveys to assess conservation status of taxa. For example, consider the Macquarie University millipede, where work was halted on digging a new lake when an apparently new millipede was discovered. Following a survey of nearby similar systems, new populations of the taxon were found and the lake development could go ahead without threatening the viability of the species.
- Plan and begin long-term monitoring (e.g. 50-year plans). Proof of changes in species composition in natural waters over several decades is rare (Hickel 1975). Itemising phytoplankton in any water body or region can be difficult, and the species encountered will depend on sampling, concentrating and preserving methods, frequency of sampling, and the conscientiousness and experience of the systematist (Hickel 1975). Essentially, the longer a sample is examined and the more frequently the water sampled, the more species are found. Note that some algae will be overlooked because of the minimum weave of plankton nets used. Internationally, the only places where long-term records are kept are where there is a freshwater institute of some kind (e.g. Constance, Plon, Windermere). Two alternatives are: i) periodic surveys at long time intervals (e.g. Yan Yean, Vic.; Tyler & Wickham 1988), or ii) Palaeolimnological studies, which would be limited mostly to siliceous algae (e.g. diatoms, chrysophytes).
- Restrict the spread of weed species that displace native algae: e.g. do not release heated water which may enhance the spread of algal weeds such as Compsopogon or Pithophora.
- Include an algal component in all limnological research (e.g. Yarra River timber harvesting trials) and, in particular, in the classification of streams and wetlands (the recent rash of reports has, from lack of information, ignored the algae of inland waters). Support must be given to survey and ecological work to find out what are the limiting factors (temporal and spatial) for algal species and communities. However, point 4 must be attended to first.
- Prepare a list of habitats that are well conserved and use them as yard-sticks: e.g. Yan Yean Reservoir, an icon in freshwater phycology (as is one of its inhabitants Micrasterias hardyi). Some work has been started in this area by Tyler and co-workers.
- Maintain checklists of Australian species and monitor new collections. Also devise mapping schemes to help better understand national distributions. This is dependent upon point 4.
- Support the production of floras and monographs of all groups of algae. Perhaps initial support could be for collection and preliminary documentation (not necessarily detailed taxonomic work but at least 'quick and dirty' surveys) from a wide range of inland localities; in particular, Western Australia and the streams of the eastern ranges. This is dependent upon point 4.
- Support ecological, habitat and dispersal studies of important species. In particular, we must assess their vulnerability and ability to withstand change. It is difficult to obtain funding for such studies because of the popularity of weed and pollution studies for non-marine algae. Such studies must be included as part of identifying those species and communities that are threatened-a stated component of the Endangered Species Program.
- Support genetic studies (e.g. La Trobe University Centre for Conservation Genetics) and international comparisons (e.g. examination of living and preserved collections overseas). Genetics are important for two major reasons: a knowledge of the evolutionary relationships of the organisms can play an integral part in maintaining true biodiversity, and understanding the genetic diversity of extent populations is essential for the future management of any threatened species. International comparisons allow us to assess the true rareness of a taxon as well as understand more about its 'evolutionary uniqueness'.
- Include conservation status in taxonomic and ecological accounts of algae.
- Prepare a list of water bodies that represents the minimum number needed to conserve the maximum number of species. Use Critical Flora Analysis, if possible including Taxic Diversity Indices-but data are seldom available (see Vane-Wright et al. 1991).
- Increase public awareness of non-marine algae by emphasising their place in the overall ecosystem. Non-vascular plants are vital to the maintenance of the earth's ecosystems and biosphere, e.g.
- in regard to global change, where depletion of the ozone layer leads to UV-B radiation rising, which affects general metabolism, photosynthetic energy production and nitrogen fixation and assimilation in many algal species (Worrest & Häder 1989, fide Roper 1991). This will affect the entire ecosystem and a higher diversity of micro-organisms will increase the chances of counteracting such changes.
- in terrestrial environments, increased atmospheric CO2 is expected to increase the rate of photosynthesis and ultimately plant litter. This will influence the composition and activities of terrestrial non-vascular plants.
- Publicise the microscopic beauty of algae and their role as part of our native flora rather than as biological indicators or as weedy and bloom-forming menaces.
- Publicise useful chemicals in algae (e.g. β-carotene in Dunaliella) and the diversity of biochemical lines (about 14 compared with a single line in flowering plants). Vascular plants are far less diverse in both their biochemistry and overall plant diversity.
- Consider community-based groups as a means of monitoring populations or of extending distribution data. The 'Serpentine-Jarradale Water Watchers' is such a group in W.A. who have collected water quality data for a catchment south of Perth. They have also co-ordinated primary school groups to assist them. Water samples were either analysed by the group (with simple assays) or sent to State chemical laboratories. Algal monitoring may be more difficult to establish, but the benefits would be substantial.
- Make cryptogam information available for people visiting reserves (e.g. for Barren Grounds Bird Reserve).
- Organise collecting trips, e.g. a discovery trip to south-western Tasmania, entering by boat from Lake Pedder and following streams into Frankland Range to rediscover Psilosiphon (Little Besom) and Batrachospermum diatyches (Unfortunate Horse-hair) while exploring streams and pools for new species.
- Devise common names where these do not exist (use localities, if restricted in distribution: e.g. the Warburton Water-gel). A reviewer was a little sceptical of this idea and provided a few examples: e.g. Staurastrum artiscon would be the 'Lesser, 15-Armed, 3-Spine-tipped, Slender Sinused, Artichotre'. The reviewer does have a valid point.
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