Community structure of a rhodolith bed from cold ... - CSIRO Publishing

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Australian Journal of Botany, 2008, 56, 437–450

Community structure of a rhodolith bed from cold-temperate waters (southern Australia) A. S. HarveyA,C and F. L. BirdB A

Department of Botany, La Trobe University, Bundoora, Vic. 3086, Australia. Department of Zoology, La Trobe University, Bundoora, Vic. 3086, Australia. C Corresponding author. Email: [email protected]. B

Abstract. Rhodolith beds are aggregations of free-living non-geniculate coralline red algae (Corallinales, Rhodophyta), with a high biodiversity of associated organisms. This is the first detailed study of a rhodolith-bed community from the coldtemperate waters of southern Australia. This bed, located at 1–4-m depth in Western Port, Victoria, is composed of four rhodolith-forming species (Hydrolithon rupestre (Foslie) Penrose, Lithothamnion superpositum Foslie, Mesophyllum engelhartii (Foslie) Adey and Neogoniolithon brassica-florida (Harvey) Setchell & Mason). M. engelhartii has a foliose growth form and the other three species have fruticose growth forms. Detailed descriptions are provided for all species, allowing reliable identification. Comparisons with other rhodolith beds and reported rhodolith-forming species, both in Australia and worldwide, are also provided. The invertebrate cryptofaunal community was quantified for two rhodolithforming species. The density of cryptofauna inhabiting foliose and fruticose rhodolith growth forms did not differ significantly and neither did abundance of individual phyla. Mean density of fauna was 0.4 invertebrates cm–3, the majority of which were polychaete worms. Comparisons of fauna associated with other rhodolith beds are also provided. A study of the vitality of the rhodolith bed showed dead rhodoliths are more abundant than live rhodoliths. Possible reasons for reduced bed vitality are explored.

Introduction Rhodoliths are unattached marine structures composed mostly (>50%) of non-geniculate coralline red algae (Corallinales, Rhodophyta) (Steneck 1986). Rhodolith or maerl beds are aggregations of rhodoliths at varying densities occurring on muddy, sandy or pebbly bottoms (Birkett et al. 1998). Beds can be found in the open ocean, wave-exposed coastlines, bays, sounds or estuaries where wave motion or currents are high enough to prevent burial by sediments (Steneck 1986; Foster 2001). Rhodolith beds are common and distributed worldwide. They are known from the tropics, as far north as British Columbia and Alaska (Konar et al. 2006) and as far south as New Zealand (see Foster 2001 for detailed review). Beds are ecologically and commercially important benthic algal communities. They often contain a high biodiversity of associated organisms and as a result are considered areas of high scientific and conservation value. Worldwide, beds are currently threatened by increasing sedimentation, pollution and other types of human activities (Birkett et al. 1998). As a result some beds in Europe (Council of the European Communities 1992) and New Zealand (Department of Conservation 1998) have been formally protected in special areas or under special directives. Rhodolith beds are spatially complex habitats, usually with a high biodiversity of associated fauna and flora, some of which may be rare or confined to rhodolith habitats (Birkett et al. 1998, p. 23). Rhodoliths provide a hard, multifaceted substratum to which invertebrates attach, hide within or burrow into. CSIRO 2008

Crustaceans, polychaetes and molluscs are the main macrobenthic faunal elements known to occur in rhodolith beds (Birkett et al. 1998, p. 112; De Grave et al. 2000; Hinojosa-Arango and Riosmena-Rodríguez 2004; Figueiredo et al. 2007); however, few studies have investigated the relationship between rhodolith species or growth forms and their associated cryptofauna. One study in Mexico (HinojosaArango and Riosmena-Rodríguez 2004) found that the abundance and richness of associated fauna was dependent on the coralline species forming the rhodoliths. Published information on rhodolith beds in Australia is sparse. Rhodolith beds are known to occur off Western Australia (Abrolhos Islands (James et al. 1999), Rottnest Island (Kendrick and Brearley 1997), the Recherché Islands/ Esperance Bay (Mathis et al. 2005; Goldberg and Kendrick 2005; Goldberg 2006), Great Australian Bight (Foster 2001; James et al. 2001)), South Australia (Port MacDonnell/Cape Northumberland (Woelkerling 1996c)) and Queensland (One Tree Reef and Fraser Island (Lund et al. 2000; Foster 2001)). Apart from isolated records of single rhodoliths (Woelkerling 1996a), until recently, there were no confirmed rhodolith beds in Victorian waters. The first author discovered the Western Port bed in 2004, while a Parks Victoria–Coastal CRC mapping partnership found a second much deeper bed in the Point Addis Marine Park in 2005. In order to protect and manage rhodolith beds effectively, it is first necessary to understand the species and interactions present in these complex marine 10.1071/BT07186

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ecosystems. The coralline red algae comprising the Western Port rhodolith bed are studied for the first time and the associated invertebrate cryptofaunal community examined. These results allow comparisons with other rhodolith beds in Australia and elsewhere and provide a basis for future ecological studies. The primary aims of the present study are to (1) provide a detailed account of the rhodolith-forming species in the bed, including species descriptions, rhodolith density, species composition and vitality, and (2) analyse the cryptofaunal community in the Western Port bed, and compare the faunas of two different rhodolith species with different growth forms. Materials and methods Study site Western Port is a large embayment, ~30 km in diameter, on the central southern coast of Victoria, Australia (Fig. 1). French Island is situated in the centre of the bay and Phillip Island delimits the southern boundary (Fig. 2). The Western Port rhodolith bed is located at 38300 30.000 S and 145220 41.400 E (~1.5 km north-east of Newhaven or 1.5 km north of San Remo) (Fig. 2). Preliminary surveys of the bed revealed it covers an area at least 1 km2, situated close to and including the main shipping channel. The bed ranges from 1 to 4 m deep on a broken rhodolith, sand and shell bottom. Outside the rhodolith bed the bottom type changes to mud or shelly sand. Preliminary data showed that canopy cover varied across the bed and included areas with either (1) no canopy cover, (2) patchy algal canopy cover or (3) dense seagrass canopy cover. Cover and depth varied between transects. Transect A consisted of no canopy cover intermixed with areas of patchy algal cover. Transect B consisted of no canopy cover intermixed with areas of dense seagrass (Halophila) cover. Transect B was 1 m deeper than Transect A. Rhodolith species composition Species composition of the rhodolith bed was quantified along two 20-m transects, 50 m apart at 3–4-m water depth. All surface rhodoliths were collected from five quadrats (25 25 cm) spaced 4 m apart along each transect. Each quadrat sample was bagged individually and all rhodoliths were air-dried for subsequent identification.

A. S. Harvey and F. L. Bird

As coralline algal identification is extremely time consuming it was not feasible to embed, section and identify every rhodolith collected from each quadrat. Instead rhodoliths were examined under a dissecting microscope and segregated into the six major groups mainly on the basis of (1) thallus (live or dead), (2) growth form (foliose or fruticose) and (3) size and shape of reproductive structures. Samples of each group were identified to species level where possible, after sectioning and detailed analysis of the internal structures. For analysis, dead rhodoliths were separated into two groups: dead with encrusting coralline alga Lithophyllum pustulatum (Lamouroux) Foslie and dead with unknown or no encrusting algae. Rhodolith identification Rhodolith specimens were prepared for identification by removing small pieces of fertile material and decalcifying in 0.6 M HNO3, then rinsing with distilled water, staining for 25–30 min in 5% aqueous KMnO4, dehydrating through 30, 60, 90, and 100% ethanol at 30-min intervals, and leaving overnight in ‘LR White’ resin (London Resin Co., Reading, Berkshire, England). After 12 h, the material was embedded in LR White by placing in plastic ‘boats’ filled with fresh resin, covered with plastic coverslips to exclude oxygen during resin hardening and placed in an oven at 70C for ~4 h. Permanent slides were prepared by cutting 6–12-mm-thick sections with a microtome and steel knife; these were placed serially on slides, cleared in ‘Histo-Clear’ (National Diagnostics, Atlanta Georgia) and mounted in ‘Eukitt’ (O.Kindler, Freiburg, Federal Republic of Germany). Slides were dried overnight on a hot plate with coverslips, weighted down by brass blocks. Species identifications were based on a comparison of vegetative and reproductive features with previously published data from Australia (Womersley 1996; Harvey et al. 2003a, 2006) and elsewhere. Growth form terminology follows Woelkerling et al. (1993). Coralline collections and permanent slides are deposited at LTB (Department of Botany, La Trobe University, Bundoora, Melbourne) and will eventually be transferred to the MEL (National Herbarium of Victoria, Royal

Figs 1–2. Location maps. Fig. 1. Map showing the location of Western Port, Victoria, Australia. Fig. 2. Map showing the location of the Western Port rhodolith bed.

Rhodolith-bed community structure from southern Australia


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Botanic Gardens, Melbourne). Herbarium abbreviations follow Holmgren et al. (1990). Cryptofaunal abundance The invertebrate community living on or burrowing within individual rhodoliths (cryptofauna) was quantified for two rhodolith species (Neogoniolithon brassica-florida (Harvey) Setchell & Mason and Mesophyllum engelhartii (?) (Foslie) Adey). N. brassica-florida has a fruticose form and Mesophyllum engelhartii (?) has a foliose form, so the invertebrate community was compared between rhodolith species as well as growth form. Twelve of the largest rhodoliths of each species were collected along a 60-m transect (pooled data from three 20-m transects). Rhodoliths were individually bagged and transferred to jars filled with ethanol : glycerol : water (1 : 7 : 2) for subsequent dissection. In the laboratory, the greatest diameter of each rhodolith was measured before it was broken apart with small chisels and tweezers. M. engelhartii (?) ranged in size from 35 to 92 mm, whereas N. brassica-florida ranged from 45 to 62 mm in greatest diameter. All cryptofauna were removed and identified to family level according to Beesley et al. (2000) and Wilson et al. (2003). As both N. brassica-florida and M. engelhartii are roughly spherical in shape, the volume of each rhodolith was calculated and invertebrate density was scaled to 1 cm3. This allowed comparisons between species and with results of other published studies. Data analysis Data were analysed with SPSS Version 13.0. All data were checked for homogeneity of variances and normality, and transformed by using natural log. Total density of rhodoliths and relative density of live and dead rhodoliths (vitality) were compared between the two transects by 2-way ANOVA. Density of each invertebrate phylum was compared between the two rhodolith species/growth forms by Student’s t-tests. Results The Western Port rhodolith bed was composed of five common non-geniculate coralline species, including four rhodolithforming species (Fig. 3) plus an additional encrusting species found growing over old or dead rhodoliths. Three species had fruticose growth forms and detailed descriptions are provided for all species, allowing reliable identification. Although the majority of the rhodoliths possessed conceptacles, these were usually old or empty. Taxonomic descriptions and comments follow. Hydrolithon rupestre (Foslie) Penrose, genus Hydrolithon. In ‘The marine benthic flora of southern Australia—Part IIIB. Gracilariales, Rhodymeniales, Corallinales and Bonnemaisoniales’. (Ed. HBS Womersley) (Australian Biological Resources Study: Canberra) p. 265 (1996) (as H. rupestris) (Figs 3B, 4–7) Description Free-living rhodolith, growth form ‘blunt’ fruticose (central nucleus not usually visible through the blunt branches) (Fig. 3B). Thallus >10 cells high when reproductively mature,

Fig. 3. Rhodolith growth forms. Ruler scale in mm. (A) Foliose growth form of Mesophyllum engelhartii (?) (LTB 18089/7). (B) ‘Blunt’ fruticose growth form of Hydrolithon rupestre. Note blunt branches completely hide the central nucleus (LTB 18086/2). (C) ‘Open’ fruticose growth form of Lithothamnion superpositum. Note central nucleus (arrows) visible through the open branches. (LTB 18087/8). (D) Fruticose growth form of Neogoniolithon brassica-florida. Note protruding pointed structures (arrows), which are the uniporate conceptacles (LTB 18081).

lacking conspicuous ventral or central layer of palisade cells (Fig. 4), lacking common horizontal rows of trichocytes, adjacent filaments joined by cell fusions (Fig. 5). Zonately divided tetrasporangia in tiny uniporate conceptacles (Figs 6, 7), tetrasporangial pore canals lined by cells orientated more-orless perpendicular to the roof surface and not protruding laterally into the pore canal (Fig. 7). Tetrasporangial conceptacles containing two or more upright sporangia situated across chamber floor, lacking a central columella (Fig. 7). Chambers 101–136 mm in diameter. Comments Hydrolithon belongs to the family Corallinaceae, subfamily Mastophoroideae. For further details and diagnostic characters of this species, see Penrose (1996a) and Harvey et al. (2006). Lithothamnion superpositum Foslie, Det Kongelige Norske Videnskabers Selskabs Skrifter 1899 (5): 8 (1900) (Figs 3C, 8–12) Description Free-living rhodolith, growth form ‘open’ fruticose (central nucleus usually visible through the ‘open’ branches) (Fig. 3C). Internal construction monomerous, epithallial cells flared (Fig. 10), subepithallial initials as long or longer than the cells immediately subtending them, adjacent filaments joined by cell fusions. Zonately divided tetrasporangia in multiporate conceptacles (Figs 8, 9), tetrasporangial roofs pitted with depressions (Fig. 8), resulting from the disintegration of

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Figs 4–7. Hydrolithon rupestre. Vegetative features and tetrasporangial conceptacles. Fig. 4. Section through reproductively mature thallus >10 cells high, lacking conspicuous ventral or central layer of palisade cells (LTB 18090/3). Scale bar = 90 mm. Fig. 5. Section showing adjacent filaments joined by cell fusions (arrows) (LTB 18090/3). Scale bar = 3 mm. Fig. 6. Surface view showing tiny non-protruding uniporate conceptacles on the thallus surface (arrow) (LTB 18090/3). Scale bar = 200 mm. Fig. 7. Section through mature conceptacle showing pore-canal cells (p) orientated more-or-less perpendicular to the roof surface, tetrasporangia (T) occurring across chamber floor, containing four zonately arranged spores (1–4) (LTB 18090/3). Scale bar = 10 mm.

uppermost cells in the filaments surrounding the pore canal (Figs 11, 12). Comments Lithothamnion belongs to the family Hapalidiaceae, subfamily Melobesioideae. For further details and diagnostic characters of this species, see Woelkerling (1996a, as L. indicum), Keats et al. (2000) and Harvey et al. (2003a). Mesophyllum engelhartii (Foslie) Adey, Det Kongelige Norske Videnskabers Selskabs Skrifter 1970: 23 (1970) (Figs 3A, 13–15) Description Growth form foliose, free-living rhodolith (Fig. 3A). Internal construction monomerous (Fig. 14), epithallial cells rounded or flattened but not flared (Fig. 15), subepithallial initials as long or longer than the cells immediately subtending, adjacent filaments joined by cell fusions (Fig. 14). Zonately divided tetrasporangia in multiporate conceptacles (Figs 13–15), cells lining pore

canals similar in size and shape to other cells in tetrasporangial conceptacle roof (Fig. 15). Gametangial conceptacles not found. Comments Mesophyllum engelhartii and Synarthrophyton patena (Hooker & Harvey in Harvey) Townsend both possess multiporate tetrasporangial conceptacles, with pore-canal cells in size and shape similar to other cells in the conceptacle roof (Woelkerling 1996a, pp. 195, 209). M. engelhartii differs from S. patena only by the presence of simple/unbranched spermatangia in male conceptacles (compared with dendroid/branched spermatangia in male conceptacles in S. patena) (Woelkerling 1996a). Despite concerted efforts, no male conceptacles were found and we could not unequivocally identify these plants to species. The foliose growth form, however, suggest these collections are more likely M. engelhartii than S. patena, and we have tentatively identified these collections as M. engelhartii (?), pending further information on male conceptacles. Mesophyllum and Synarthrophyton belong to the family Hapalidiaceae, subfamily Melobesioideae. For further details and diagnostic



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Figs 8–12. Lithothamnion superpositum. Vegetative features and tetrasporangial conceptacles. Fig. 8. Surface view of multiporate conceptacle showing characteristic depressions in the pore-plate (arrow), resulting from the disintegration of filaments surrounding the pores (LTB 18086). Scale bar = 250 mm. Fig. 9. Section through mature conceptacle showing tetrasporangia containing zonately arranged spores (1–4) (LTB18086). Scale bar = 30 mm. Fig. 10. Section through the thallus showing flared epithallial cells (arrows) (LTB18072). Scale bar = 5 mm. Fig. 11. Scanning electron microscopic surface view of conceptacle pore-plate showing pore (p) surrounded by disintegrating rosette cells (arrows) (LTB18087/4). Scale bar = 5 mm. Fig. 12. Section through multiporate conceptacle roof showing disintegrating uppermost cells (arrows) in filaments lining the pore canal (p) (LTB18086). Scale bar = 10 mm.

characters of these species, see Chamberlain and Keats (1995), Woelkerling (1996a) and Harvey et al. (2003a, 2005). Neogoniolithon brassica-florida (Harvey) Setchell & Mason, Proceedings of the National Academy of Sciences, Washington 29: 91 (1943) (Figs 3D, 16–19) Description Free-living rhodolith, growth form fruticose, with large protruding, pointed uniporate conceptacles (Fig. 3D). Thallus lacking a conspicuous ventral or central layer of palisade cells (Fig. 16), adjacent filaments joined by cell fusions (Fig. 17). Tetrasporangia in large uniporate conceptacles (Figs 18, 19), tetrasporangial pore canals lined by cells orientated more or less parallel to the roof surface and protruding laterally into the pore canal (Fig. 19). Comments Neogoniolithon brassica-florida has very large protruding conceptacles (Fig. 18) and can often be recognised in the field by the presence of these conspicuous reproductive structures (Penrose 1996b). Although mostly old or empty conceptacles were found in the rhodolith bed, the size of the conceptacles (520– 780 mm), conceptacle morphology and vegetative features rule out all other known Australian species. Neogoniolithon belongs

to the family Corallinaceae, subfamily Mastophoroideae. For further details and diagnostic characters of this species, see Penrose (1996b) and Harvey et al. (2006). Lithophyllum pustulatum (Lamouroux) Foslie, Wissenschaftliche Meeresuntersuchungen 7 (1): 8 (1904) (Figs 20–24) Description Attached plant, growth form encrusting, (following contours of underlying rhodolith/substrate) (Fig. 20). Adjacent filaments joined by secondary pit-connections (Fig. 21). Tetrasporangia in uniporate conceptacles (Figs 22–24). Tetrasporangial pore canals lined by cells that may project into the canal but do not completely occlude the pore canal (Figs 22, 24). Floors of tetrasporangial conceptacle chambers usually situated 1–3 cell layers below surrounding thallus surface (Fig. 22). Thallus lacking numerous overlapping layers and terraced appearance in surface view. Comments This species usually forms thin (0.05–2.5 mm thick) encrusting to layered plants in southern Australia (Woelkerling 1996b). In the Western Port bed, it was commonly found encrusting/ overgrowing old or dead rhodoliths, sometimes almost

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Figs 13–15. Mesophyllum engelhartii (?). Vegetative features and tetrasporangial conceptacles. Fig. 13. Surface view showing numerous multiporate tetrasporangial conceptacles (arrows) on the thallus surface (LTB 18086). Scale bar = 590 mm. Fig. 14. Section through an old multiporate conceptacle showing cell fusion (arrow-F), tetrasporangia and pores in the conceptacle roof (arrows) (LTB18076). Scale bar = 50 mm. Fig. 15. Enlarged section through multiporate conceptacle roof showing pore plugs (p) blocking pore canals and rounded epithallial cell (e). Note that cells lining the pore canal (arrow-p) are similar in size and shape to other roof cells (arrow-r) (LTB18076). Scale bar = 10 mm.

completely covering the old thallus (Fig. 20). Lithophyllum belongs to the family Corallinaceae, subfamily Lithophylloideae. For further details and diagnostic characters of this species, see Woelkerling and Campbell (1992), Woelkerling (1996b) and Harvey et al. (2005). Rhodolith density, vitality and species composition Density of rhodoliths did not differ significantly between transects (Table 1). Mean density was 506 160 rhodoliths per square metre of seafloor (total includes live and dead rhodoliths). Significantly more dead than live rhodoliths, however, were present in the surface layer of the Western Port bed (Table 1, Fig. 25), with live rhodoliths ranging from 15 to 37% (Fig. 26). If dead rhodoliths with encrusting Lithophyllum pustulatum are included, the percentage of rhodoliths with live growth or overgrowth increases to 40–52% (Fig. 26). There was also a significant interaction between the effects of vitality and transect, which can be explained by the differences in relative density of live and dead rhodoliths between transects (Table 1, Fig. 25).

Species composition varied considerably between transects. The only species of live rhodolith collected from Transect A was Neogoniolithon brassica-florida (37%), whereas all four species of live rhodolith (N. brassica-florida (7%), Hydrolithon rupestre (3%), Mesophyllum engelhartii (?) (3%) and L. superpositum (3%)) were found along Transect B (Fig. 26). The encrusting coralline alga L. pustulatum was present in both transects. Cryptofaunal abundance Mean density of cryptofauna in the Western Port bed was 0.4 0.09 individuals cm–3. Polychaete worms (Annelida) dominated the cryptofauna (Fig. 27) and comprised 89% of the community. Molluscs (predominately bivalves) were the next most abundant group (Fig. 27), but contributed only 8% to the cryptofauna. The polychaete family Terebellidae dominated the annelid fauna associated with both forms of rhodolith (Table 2), and comprised 53% of the annelid community. The density of cryptofauna (all phyla combined) inhabiting foliose and fruticose forms did not differ significantly and neither did density of individual phyla (Fig. 27, Table 3).



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Figs 16–19. Neogoniolithon brassica-florida. Vegetative features and tetrasporangial conceptacles. Fig. 16. Section showing thallus lacking conspicuous ventral or central layer of palisade cells (LTB 18086/4). Scale bar = 200 mm. Fig. 17. Section showing adjacent filaments joined by cell fusions (arrows) (LTB 18086/4). Scale bar = 10 mm. Fig. 18. Surface view showing characteristic large, protruding, pointed uniporate conceptacles on the thallus surface (LTB 18086/4). Scale bar = 400 mm. Fig. 19. Section through conceptacle showing remains of old tetrasporangia (arrow) and pore canal lined by cells orientated more or less parallel to the roof surface and protruding laterally into the pore canal (LTB18088/3). Scale bar = 10 mm.

Discussion Rhodolith-forming genera and species Of the 26 currently recognised genera of non-geniculate coralline red algae (Harvey et al. 2003b), at least eight contain species that commonly form rhodoliths (Harvey and Woelkerling 2007). These eight genera represent all three Corallinales families, i.e. Hapalidiaceae (Lithothamnion, Phymatolithon, Mesophyllum), Corallinaceae (Hydrolithon, Neogoniolithon, Lithophyllum, Spongites) and Sporolithaceae (Sporolithon). The Western Port bed comprises four rhodolith-forming genera from the following two families: Hapalidiaceae (Lithothamnion, Mesophyllum?) and Corallinaceae (Neogoniolithon, Hydrolithon). At the species level, at least 40 non-geniculate corallines are recorded to form rhodoliths. Identification of rhodoliths to species level, however, remains problematic. On a world scale, detailed study of type material and taxonomic studies of existing and newly discovered rhodolith beds are warranted before the ‘true’ number of rhodolith-forming species can be known (Harvey and Woelkerling 2007).

Hydrolithon rupestre is widespread in southern Australia, occurring from Western Australia eastwards to New South Wales (Penrose 1996a, p. 266). This species has not previously been reported to form rhodoliths in Australia or elsewhere. Four other species of Hydrolithon are recorded to form rhodoliths worldwide (Table 4). Lithothamnion superpositum is only known from Victoria in southern Australia (Woelkerling 1996a, as L. indicum). All known southern Australian plants are rhodoliths (single specimens from Corner Inlet, Port Phillip Heads and Western Port, Victoria) (Woelkerling 1996a), although the species has been found as attached plants in south-eastern Australia (Harvey et al. 2003a). Outside Australia the species has been reported as rhodolith-forming in Tanzania (Oliveira et al. 2005). Thirteen other species of Lithothamnion are recorded to form rhodoliths worldwide (Table 5). In southern Australia, Mesophyllum engelhartii is common and widespread (Woelkerling 1996a), occurring from Western Australia eastwards to Victoria, and Tasmania. The species has not previously been reported to form rhodoliths in Australia but is

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Figs 20–24. Lithophyllum pustulatum. Morphology, vegetative features and tetrasporangial conceptacles. Fig. 20. Encrusting growth form of L. pustulatum, overgrowing and almost completely covering an old lumpy rhodolith (LTB 18082/3). Scale bar = 5 mm. Fig. 21. Section through the thallus showing secondary pit-connection (arrow) joining cells of adjacent filaments (LTB18072). Scale bar = 10 mm. Fig. 22. Section through the thallus showing L. pustulatum (L.) overgrowing host rhodolith (H) (LTB 18076). Scale bar = 100 mm. Fig. 23. Surface view showing small protruding uniporate conceptacles (arrow) on the thallus surface (LTB 18082/2). Scale bar = 1 mm. Fig. 24. Section through old conceptacle showing tetrasporangia. Note tetrasporangium in the pore canal, apparently exiting the conceptacle (LTB18082). Scale bar = 40 mm.

known to form fruticose rhodoliths in the Gulf of California (Yabur-Pacheco and Riosmena-Rodríguez 2006). Four other species of Mesophyllum are recorded to form rhodoliths worldwide (Table 6). Neogoniolithon brassica-florida occurs commonly throughout southern Australia from Western Australia eastwards to Victoria (Penrose 1996b, p. 283). The species has previously been reported to form rhodoliths in southern Australia (Penrose 1996b, p. 281), the Mediterranean (Mannino et al. 2002) and Tanzania (Oliveira et al. 2005). Three other species of

Neogoniolithon are recorded to form rhodoliths worldwide (Table 7). Lithophyllum pustulatum is widespread in southern Australia, occurring from Western Australia through to New South Wales, including Tasmania (Woelkerling 1996b, p. 229). In southern Australia, plants are comparatively thin, mostly