Charophytes (2009) Volume 1 (2), 55–60 Published May 2009 Chara canescens (Characeae, Charophyceae) in the Southern Hemisphere Michelle T. Casanova1 and J.M. Nicol2 1 Royal Botanic Gardens Melbourne, Birdwood Ave, South Yarra, Vic. 3141, Australia, and 273 Casanova Rd, Westmere Vic. 3351, Australia 2 Inland Waters and Catchment Ecology Program, South Australian Research and Development Institute (Aquatic Sciences), PO Box 120 Henley Beach SA 5022, Australia corresponding author: amcnova@netconnect.com.au M.T. Casanova and J.M. Nicol 2009. Chara canescens (Characeae, Charophyceae) in the Southern Hemisphere. Charophytes 1: 55–60. During a survey for charophytes in South Australia, and a seed bank study to determine macrophyte responses to coastal lake management, specimens of Chara canescens Desv. and Lois. in Lois. were collected. The species is distinctive with a haplostichous corticated axis and branchlets, two rows of stipulodes (diplostephanous) at the base of the branchlet whorls, spine cells in groups (fasciculate) on the axis and verticillate bract cells. To date only female plants have been found, which is consistent with the widespread occurrence of parthenogenetic populations of C. canescens in the Northern Hemisphere. This is the only example of Chara subgenus Chara section Desvauxia R.D. Wood known from the Southern Hemisphere. Chara canescens is listed as a rare and threatened species in the United Kingdom and Europe. The mechanism of dispersal of this species is thought to be via migrating waterbirds from Siberia, Mongolia and northern China. Given the occurrence of C. canescens in southern Australia, we speculate that other Northern Hemisphere species might be found in habitats favoured by migratory birds. Further, we speculate that dispersal via shore-birds could be a mechanism by which Lamprothamnium was transported to the Northern Hemisphere. Environmental changes that affect the migration of waterbirds between the Northern and Southern Hemisphere could impact on the maintenance of biodiversity in wetlands in both places. Keywords: Lake George; South Australia; dispersal; biodiversity; waterbirds; rare species INTRODUCTION MATERIALS AND METHODS Charophytes are submerged water plants with a distinctive morphology. They are the closest living relatives to the ancestors of land plants (Karol et al. 2001), but despite their long fossil history and physical fragility they are often abundant and diverse in Australian wetlands. Charophytes are also important in nutrient cycling (Kufel and Kufel 2002; Rodrigo and Alonso-Guillén 2008) and provide food for water birds (Baily et al. 2008), habitat for invertebrates, and maintain water clarity (Casanova et al. 2003; Van den Burg et al. 2004; Scheffer and van Nees 2007). Charophyte abundance often decreases when water quality declines and water bodies become eutrophic (Blindow 1992; Steinhardt and Selig 2007). In fact, loss of charophyte dominated communities is an indicator of ecological decline (Selig et al. 2007). Charophytes are not always identified to species in Australia, mostly because of difficult keys and erroneous taxonomic treatments (see review by Casanova 2005), but this is changing, and recent treatments and surveys have recorded up to 30 species of Chara and c. 50 species of Nitella (Casanova 2005, García and Chivas 2006; Casanova 2009). Although specimens have been collected in Australia for more than 200 years, surveys can result in the discovery of new species (García 1998; García and Casanova 2003; Casanova and Karol 2008) and in this case, the collection of a species well-known in the Northern Hemisphere (Corillion 1957; Moore 1986; Langangen 1993; Küster et al. 2005) but hitherto unrecorded in the Southern Hemisphere. Sites in South Australia were surveyed for charophytes in regular vegetation surveys and seed bank studies. Vegetation surveys consisted of collection of submerged plants by hand or via grapnel (from deep sites). Plants were rinsed free of adhering material and either pressed or preserved in 70% alcohol. Living and preserved plants were examined with the aid of Zeiss microscopes and digital images were obtained by taking photographs with a camera through the microscope eyepiece or via a trinocular head. Oospores were examined with the aid of scanning electron microscopy following the methods of Casanova (2005). Line drawings were produced using Paint-Shop Pro. Seed bank methods Sediment containing Chara canescens oospores was collected from the northern lake of Lake George (37˚28.869’S, 139˚58.036’) on the 28th of February 2007 as part of a study investigating the sediment seed bank of the system. Lake George is a shallow coastal lagoon near the township of Beachport in South Australia. Salinity in the system ranged from hypersaline (39000 mgL-1) in summer and early autumn of 1976 to brackish (611 mgL-1) during the winter of 1982 with annual water-level fluctuations often in excess of 1.5 m (Ye et al. 2002). Recently large areas of the lake margins have dried annually and salinity has exceeded 40000 mgL -1. The sediment was transported to South Australian Aquatic Sciences Centre, dried at 40˚C to a constant weight and stored at room temperature in a paper bag. Samples were flooded with fresh water to a depth of 10 cm in 4 L plastic containers (200 × 200 × 120 mm) on the 31st of May 2007. Salinity in 55 Charophytes Vol. 1 (2), (2009) the samples containing Chara canescens oospores ranged from 1.50 ̶ 5.16‰ TDS. Chara canescens germinated and was observed after 11 weeks of inundation and plants were grown to a stage when oospores were present to enable it to be identified. Specimens were pressed and are deposited in the National Herbarium of Victoria (MEL) and the State Herbarium of South Australia (AD). RESULTS Two specimens were identified as Chara canescens using keys in Wood (1965), Moore (1986) and with reference to illustrations in Imahori and Wood (1965), and the type description provided by van Raam (2006). Chara canescens Desvaux and Loiseleur in J.L.A. Loiseleur Deslongchamps, 1810. Notice sur les plantes a ajouter a la flore de France (Flora Gallica); avec quelques corrections et observations. Paris, p 139. Synonym: Chara crinita Wallroth. Description of Australian material Plants female, up to 15 cm high, without calcium carbonate deposition on the thallus. Axes to 400 μm in diameter (Fig. 1a), often appearing thicker because of the abundant spine cells, 1  corticate (haplostichous, Fig. 1c, d). Spine cells in groups of 1–3 (fasciculate) 1–1.5 mm long, longer than the axis is wide (Fig. 1b, c). Branchlets 8–10 in a whorl, to 5 cm long; 6–7 cells, 5 of them corticated, the end segment ecorticate and sometimes 2 cells long (Fig. 1e). Stipulodes in two well-developed rows below the branchlets, twice as many as branchlets in each row, the upper row as long or longer than the basal branchlet cell (Fig 1b). Bract cells up to 2  as long as the oogonia, equally developed internally and externally (Fig. 1f). Bracteoles, 2, to 700 µm long, as long as, or longer than mature oogonia (Fig. 1g). A bractlet present in place of the antheridium (Fig. 1f). Gametangia at the lowest 3 branchlet nodes (Fig. 1f). Oogonia (measured dry) to 680 µm long, 320 μm wide, coronula 66 μm high, cells upright and appressed (Fig. 1g). Oospores black, 490 μm long, 300 μm wide (Fig. 1h), 10–12 striae and a single, pentagonal basal cell impression, oospore wall smooth to finely granulate (Fig. 1i). No antheridia seen. This species has a thin stem, but the presence of long and abundant spine cells in groups on the axial cortex can give the appearance of a thicker stem. Because only oosporangial plants have been found despite thorough searching, the Australian representatives of this species are apparently parthenogenetic (a condition recorded for populations in northern Europe (Ernst 1921) and America (Allen 1951)). The haplostichous cortex on axis and branchlets, diplostephanous stipulodes and fasciculate spine cells distinguish C. canescens from all other species in Australia. Specimens: South Australia: Quarry pond, Mt Monster Conservation Park, M.T. Casanova r020, 27-x-2007, MEL. Lake George seed bank culture, J.M. Nicol, 25-x-2007, MEL, AD, r025. Europe: coll? Date?. MEL, p069. 56 Distribution The British Isles (Bryant et al. 2002), France (Corillion 1957; Verhoeven 1975), Spain (Alvarez-Cobelos et al. 2001; Cirujano et al. 2008), the Baltic Sea (Appelgren and Mattila 2005), Sweden (Eriksson et al. 2004), Germany (Selig et al. 2007; Korsch et al. 2008), Spitsbergen (Langangen 1979; 2000), China (Han and Lu 1994), British Colombia, Canada (Allen 1951), maritime states of eastern USA (Allen, 1882) and Newfoundland (Mann and Nambudiri 1995; Mann et al. 1999). Bisexual populations occur in Austria, Hungary and the Caspian Sea (Küster et al. 2005). In Australia: south-east of South Australia, two localities. Ecology Plant associations: In Australia C. canescens has been associated with Lamprothamnium succinctum (A. Braun in Asch.) R.D. Wood and Ruppia tuberosa Davis and Toml. in coastal, saline Lake George, and with Tolypella sp. and Chara leptopitys subsp. subebracteata Nordst. at Mt Monster quarry. In the Northern Hemisphere it is found in brackish to saline habitats with other salinity-tolerant charophytes including Lamprothamnium papulosum (Wallr.) J. Groves, Chara aspera Deth. ex Willd., Chara baltica Bruz., Tolypella glomerata Desv. in Lois. and T. nidifica (O. Müll.) A. Braun and is a component of sea-grass (Ruppia cirrosa (Petagna) Grande and Zostera marina L.) dominated communities (Verhoeven 1975; Boegle et al. 2007; Selig et al. 2007; Mann et al. 1999). Life history and physiology: Chara canescens grows at depths of 0.5–1.5 m in permanent (Mann et al. 1999, Steinhardt and Selig 2007) and temporary (Bonis and Grillas 2002) maritime wetlands with sandy substrata and a high pH (Moore 1986). The corticated, spinose thallus of C. canescens is resistant to grazing by amphipods (Mann et al. 1999). Both a high light requirement and resistance to herbivory have been suggested as explanations for the shallow distribution of C. canescens. It is occasionally found in inland freshwater wetlands (Moore 1986) and quarry ponds (Stewart and Church 1992). Populations form a persistent seed bank in the sediment (Bonis et al. 1993; Steinhardt and Selig 2007). Sporelings germinate in oxygenated sediments (Bonis et al. 1993). Plant abundance is negatively correlated to sediment phosphorus concentrations (Selig et al. 2007), i.e. where phosphorus concentrations are high, abundance is low. Mechanical disturbance (i.e. in the presence of marinas) appears to negatively affect plant distribution (Eriksson et al. 2004). Reproduction occurs late in the season (Bonis and Grillas 2002) so short flooding times in temporary wetlands negatively affect reproductive success. Increasing salinity has been correlated with increased reproductive effort in C. canescens (Bonis et al. 1993). The photosynthetic efficiency differs for male and female plants, with female plants being more efficient in light acclimation, and all plants tolerating high light intensities without photoinhibition (Küster et al. 2005). Casanova & Nicol: Chara canescens in Australia a e b c f d h g i Figure 1. Chara canescens Desv. and Lois. in Lois. Specimen: Mt Monster, South Australia, M.T. Casanova r020, 27-x-2007, MEL. (a) Whole plant showing narrow, spinose axes and whorls of branchlets at the nodes. Scale bar = 1cm. (b) Axis node showing a single whorl of corticated branchlets subtended by two whorls of stipulodes (uppers as long as the first branchlet cell, lowers somewhat shorter). Scale bar = 500 µm. (c) Axis cortication showing haplostichous cortex and spine cells in groups of three. Scale bar = 500 µm. (d) Cross-section of an axis internode showing the central internodal cell surrounded by 8 cortical cells (i.e. the same as the number of branchlets in the adjacent whorl = haplostichous cortex). Scale bar = 500 µm. (e) Whole branchlet of 6 cells, oogonia present on the lowest three branchlet nodes. Scale bar = 500 µm. (f) Mature oogonium on a branchlet node with verticillate bract cells, bracteoles and bractlet. Scale bar = 500 µm. (g) Oogonium showing coronula of five upright, appressed cells. Scale bar = 500 µm. (h) Scanning electron micrograph of a mature oospore (490 µm long  300 µm wide) with 11–12 striae. Scale bar = 100 µm. (i) Basal view of oospore showing pentagonal basal cell impression on the oospore and relatively smooth surface. Scale bar = 50 µm. 57 Charophytes Vol. 1 (2), (2009) DISCUSSION The collections reported here constitute a new record of Chara canescens in Australia and the first record of this species, and this section of Chara, in the Southern Hemisphere. The distribution of C. canescens has now been recorded on the continents of Europe, Africa (along the Mediterranean coast), Asia, North America and Australia. There are several charophytes that have a cosmopolitan (or nearly so) distribution, most notably the common species Chara globularis Thuill. and Nitella hyalina Ag. These two species are tolerant of a range of environmental conditions including salinity, eutrophication, ephemerality (Casanova 2004; Casanova and Karol 2008) and occur at a range of depths and pH (García and Chivas 2004). They have a relatively continuous distribution all over the world, absent only from isolated islands (Wood 1965). In contrast, C. canescens has narrower ecological preferences and consists of widespread but isolated populations, and is considered rare and threatened over some of its range (Stewart and Church 1992; Krauss 1997). Thus the occurrence of C. canescens so far outside its previously recorded distribution is of note. There are two possible explanations for the occurrence of C. canescens in Australia: (1) it is a recent immigrant, possibly assisted by humans and (2) it was always here, but was not collected in the past. Both these hypotheses are valid. Many Northern Hemisphere species have been introduced into Australia in the last 200 years. However, despite the potential for humans to act as vectors of charophytes there is evidence of only a single of human-assisted introduction of a charophyte species (Proctor 1980). As well, although a large number of terrestrial and aquatic species have been introduced to Australia, the majority have been purposeful introductions for agriculture or amenity (gardens, fish tanks). It is possible, but unlikely, that C. canescens was introduced in this way. The alternative hypothesis is that C. canescens has been always been here, but was undetected in South Australia due to few thorough cryptogamic surveys and the lack of general expertise or interest in charophyte identification. The historical presence of C. canescens in Lake George could be tested via its occurrence in dated sediment cores. Chara canescens probably evolved in the Northern Hemisphere because its dioecious counterparts (i.e. nonparthenogenetic female and male plants) are found only in Europe (Küster et al. 2005). Outside the core distribution of the dioecious populations it acts as a monoecious species because, as a parthenogenetic female, only one individual or one oospore is required for invasion of a new habitat. This is in line with the conjectures of Proctor (1980) in relation to the biogeography of charophytes, and could be tested by comparing the genetic makeup of different populations of C. canescens. The most likely vectors for C. canescens are waterbirds that migrate from the Northern Hemisphere (Alaska, Siberia, Mongolia and northern China) to the Southern Hemisphere annually (Morcombe 2000; Nebel et al. 2008). Waterbirds have been shown to carry oospores in their 58 digestive tract for days, if not weeks (Proctor 1962), and although the probability that a single spore would survive the distance is low, the annual migration of tens of thousands of birds (Nebel et al. 2008) for probably tens of thousands of years means that the cumulative low probability is close to a certainty over time. The occurrence of C. canescens in Australia could therefore have implications for biogeography of other charophytes. Taking the speculation further, several charophyte species are known to occur with C. canescens including C. aspera, C. baltica, Lamprothamnium papulosum and Tolypella glomerata. Until Wood’s (1972) revision of Australian Characeae, all the Australian specimens of Lamprothamnium were identified as L. macropogon (A. Braun) I.L. Ophel (Ophel 1947) or L. succinctum (Daily 1969). Wood (1972) amalgamated all the Australian taxa with the Northern Hemisphere L. papulosum. Recent treatments (van Raam 1995; García and Chivas 2004; García and Chivas 2006) have listed all Australian specimens as L. macropogon, L. succinctum, L. heraldii A. García and Casanova, L. williamsii A. García and Chivas or L. sp. nov. Given that C. canescens occurs in Australia it is very possible, even likely, that L. papulosum does too. A thorough review of the genus Lamprothamnium should reveal whether this is so. Similarly, if C. canescens was dispersed to Australia via migrating waterbirds it cannot be assumed that other Northern Hemisphere charophyte species (e.g. Tolypella nidifica, T. glomerata) do not occur in Australia. The potential for distribution of charophytes from Australia to the Northern Hemisphere also exists. If the genus Lamprothamnium evolved in the Southern Hemisphere, as has been suggested (García and Casanova 2003), then a possible mechanism exists for its transport to habitats in Asia (and thence elsewhere in the Northern Hemisphere). The possibility for dispersal and the coincidence of similar habitats reinforces the idea that similar processes are important in ecosystem integrity and maintenance of biodiversity world-wide. Although the previous discussion is purely speculative, the hypotheses introduced (that C. canescens has been in Lake George for more than 200 years; that C. canescens in Australia originated in parts of the Northern Hemisphere from which waterbirds regularly migrate; that Lamprothamnium papulosum occurs in Australia) can be tested. It also reinforces the idea that the geographic focus of individual charophyte researchers should sometimes be much wider than it usually is (Mann et al. 1999). The migration stop-over sites and seasonal habitats of waterbirds in Australia, New Zealand and countries in the Northern Hemisphere are protected under a series of International Agreements (Japan-Australia Migratory Bird Agreement, China-Australia Migratory Bird Agreement and Republic of Korea-Australia Migratory Bird Agreement). However, the recent pace of development in China and over-exploitation of rivers in Australia has put some of these habitats at risk (Nebel et al. 2008). The occurrence of C. Casanova & Nicol: Chara canescens in Australia canescens in Australia could provide further evidence of the importance of these global patterns of wildlife movement and reinforces the need for international conservation agreements. ACKNOWLEDGEMENTS This work was undertaken while MTC was employed under an Australian Biological Resources Study grant. The assistance of Dr Simon Crawford with scanning electron microscopy is appreciated. REFERENCES Allen GO (1951) Notes on charophytes from British Colombia. Proceedings of the Linnean Society of London 162:48–152. Allen TF (1882) Development of the cortex in Chara. Bulletin of the Torrey Botanical Club 9:37–47. Alvarez–Cobelas M, Cirujano S & Sanchez-Carrillo S (2001) Hydrological and botanical man-made changes in the Spanish wetland of Las Tablas de Daimiel. Biological Conservation 97:89–98. Appelgren K & Mattila J (2005) Variation in vegetation in shallow bays of the northern Baltic Sea. Aquatic Botany 83:1–13. Baily M, Petrie SA & Badzinsky SS (2008) Diet of Mute Swans in Lower Great Lakes coastal marshes. Journal of Wildlife Management 72:726–732. Blindow I (1992) Decline of charophytes during eutrophication: comparison with angiosperms. Freshwater Biology 28:9–14. Boegle MG, Schneider S, Mannschreck B & Melzer A (2007) Differentiation of Chara intermedia and C. baltica compared to C. hispida based on morphology and amplified fragment length polymorphism. Hydrobiologia 586:155– 166. Bonis A & Grillas P (2002) Deposition, germination and spatio–temproral patterns of charophyte propagule banks: a review. Aquatic Botany 72:235–248. Bonis A, Grillas P, van Wijck C & Lepart J (1993) The effect of salinity on the reproduction of coastal submerged macrophytes in experimental communities. Journal of Vegetation Science 4:461–468. Bryant JA, Stewart NF & Stace CA (2002) A checklist of Characeae of the British Isles. Watsonia 24:203–208. Casanova MT (2004) ‘A census of submerged plants of the Angas River and Tookayerta Creek Catchments’. Consultants report. (River Murray Catchment Management Board, Strathalbyn) Casanova MT (2005) An overview of Chara in Australia (Characeae, Charophyta). Australian Systematic Botany 18: 25–39. Casanova MT (2009) An overview of Nitella in Australia (Characeae, Charophyta). Australian Systematic Botany 22: in press. Casanova MT& Karol KG (2008) Monoecious Nitella species from south–eastern mainland Australia including Nitella paludigena sp. nov. Australian Systematic Botany 21:201–216. Casanova, MT, de Winton MD & Clayton JS (2003) Do charophytes clear turbid water? Verhandlungen Internationale Vereiningung für Theroretische und Angewandte Limnologie 26:1440–1443. Cirujano S, Cambra J, Sánchez Castillo A, Meco A, & Flor Arnau N (2008) Flora ibérica Algas continentales. Carófitos (Characeae). Real Jardín Botánico de Madrid, Spain. Corillion R (1957) Les charophycées de France et d’Europe Occidentale. Bulletin de la Société Scientifique de Bretangne 32:1–471. Daily FK (1969) A Lamprothamnium succinctum with imperfect cortex. Bulletin of the Torrey Botanical Club 96:656–660. Eriksson BK, Sandström A, Isæus M, Schreiber H & Karås P (2004) Effects of boating activities on on Aquatic vegetation in the Stockholm archipelago, Baltic Sea. Estuarine, Coastal and Shelf Science 61:339–349. Ernst A (1921) Die Nachkommenschaft aus amphimiktisch und apogam estanded Sporen von Chara crinita. Zeitschrift für induktive Abstammungs und Vererbungslehre 25:185–197. García A (1998) Nitella ignescens sp. nov. and N. ungula sp. nov. (Charales, Charophyta) from Australia. Phycologia 37:53–59. García A & Casanova MT (2003) Lamprothamnium heraldii sp. nov. (Charales, Charophyta) from Australia: the first dioecious representative of the genus. Phycologia 42:622– 628. García A & Chivas AR (2004) Quaternary and extant euryhaline Lamprothamnium Groves (Charales) from Australia: gyrogonite morphology and paleolimnoligical significance. Journal of Paleolimnology 31:321–341. García A & Chivas AR (2006) Diversity and ecology of extant and Quaternary Australian charophytes (Charales). Cryptogamie, Algologie, 27:323–340. Han F & Li Y (1994) Flora Algarum Sinicarum Aquae Dulcis Tomus 3: Charophyta. Science Press, Beijing, P.R.China. 267pp. Imahori K & Wood RD (1965) ‘Iconograph of the Characeae’. Volume 2 in Wood RD and Imahori K A Revision of the Characeae. Cramer, Weinheim. Karol KG, McCourt RM, Cimino MT & Delwiche CF (2001). The closest living relatives of land plants. Science 294:2351–2353. Korsch H, Raabe U & van de Weyer K (2008) Verbeitungskarten der Characeen Deutschlands. Rostocker Meeresbiologische Beitrage 19:57–108. Krauss W (1997) Charales (Charophyceae). Susswasserflora von Mitteleuropa. Band 18. Gustav Fischer. Jena, 202pp. [In German] Kufel L & Kufel I (2002) Chara beds acting as nutrient sinks in shallow lakes – a review. Aquatic Botany 72:249– 260. Küster A, Schaible R & Schubert H (2005) Sex–specific light acclimation in Chara canescens (Charophyta). Aquatic Botany 83:129–140. 59 Charophytes Vol. 1 (2), (2009) Langangen A (1993) Some morphological and ecological observations on Chara canescens (Charophyta). Cryptogamie, Algologie 14:215–220. Langangen A (2000) Charophytes from the warm springs of Svalbard. Polar Research 19:143–153. Mann H & Nambudiri (2005) Charophytes of insular Newfoundland II. Chara evoluta and Chara canescens. Canadian Field-Naturalist 119:26–37. Mann H, Proctor VW & Taylor AS (1999) Towards a biogeography of North American Charophytes. Australian Journal of Botany 47:445–458. Moore JA (1986) Charophytes of Great Britain and Ireland. BSBI handbook No. 5. Botanical Society of the British Isles, London. 141 pp. Morcombe M (2000) Field guide to birds of Australia. Steve Parish Publishing Pty Ltd, Archerfield, Qld, Australia. 448 pp. Nebel S, Porter JL & Kingsford RT (2008) Long-term trends of shore-bird populations in eastern Australia and impacts of freshwater extraction. Biological Conservation 141:971– 980. Ophel IL (1947) Notes on the genera Lychnothamnus and Lamprothamnium (Characeae). Transactions of the Royal Society of South Australia 71:318–323. Proctor VW (1962) Viability of Chara oospores taken from migratory water birds. Ecology 45:656–658. Proctor VW (1980) Historical biogeography of Chara (Charophyta): an appraisal of the Braun–Wood classification plus a falsifiable alternative for future consideration. Journal of Phycology 16: 218–233. Rodrigo MA & Alonso-Guillén JL (2008) In situ nitrate uptake rates in two Chara species. Charophytes 1: 49–54. Scheffer M & van den Nees EH (2007) Shallow lakes theory revisited: various alternative regimes driven by climate, nutrients, depth and lake size. Hydrobiologia 584:455–466. 60 Selig U, Eggert A, Schories D, Schubert M, Blümel C & Schubert H (2007) Ecological classification of macroalgae and angiosperm communities of inner coastal waters in the southern Baltic Sea. Ecological Indicators 7:665–678. Steinhardt T & Selig U (2007) Spatial distribution patterns and relationship between recent vegetation and diaspore bank of a brackish coastal lagoon on the southern Baltic Sea. Estuarine, Coastal and Shelf Science 74:205–214. Stewart NF & Church JM (1992) Red Data Books of Great Britain and Ireland: Stoneworts. Joint Nature Conservation Committee, Peterborough, UK. Van den Burg M, Coops H & Simons J (2004) Propagule bank buildup of Chara aspera and its significance for colonization of a shallow lake. Hydrobiologia 462:9–17. van Raam JC (1995) The Characeae of Tasmania. Cramer, Berlin. van Raam JC (2006) Database Characeae and Bibliography of the Characeae. Charaboek@hotmail.com, ‘s–Gravesandelaan 32, NL 1222 TA Hilversum, The Netherlands. Verhoeven JTA (1975) Ruppia communities in the Camargue, France. Distribution and structure in relation to salinity and salinity fluctuations. Aquatic Botany 1:217– 241. Wood RD (1965) ‘Monograph of the Characeae’. Volume 1 in Wood RD and Imahori KI A Revision of the Characeae. Cramer, Weinheim. Wood RD (1972) Characeae of Australia. Cramer Lehre. Ye Q, Short D, de Jong M, Jones K, & Fleer D. (2002) ‘Monitoring the recovery of fish stock and overall ecological health of Lake George’. Report for the Lake George Management Committee. (South Australian Research and Development Institute, Aquatic Sciences). Manuscript submitted 7 November 2008; accepted 10 March 2009. Associate Editor M.J. Beilby.