Cyanobacteria and associated
ENVIRONMENT: ECOLOGY AND GLOBAL CHANGE
Plate 1:
Fig. 1. Zonation ofOTIcoastal area. Zone 1 is covered by water. Zone II brown hue.
Zone III yellow white hue. ZoneIVgrey hue.
Fig. 2. Zone lIa, consolidated reef crest.
Fig. 3. Edge of brake of a consoJidated piece of coral carbonate. The green band (alTow) consists ofOsireobium quekellii, the orange band ofPleclOnema lerebrans.
Fig. 4.Kyrlhulrix dalmalica. Scale bar equals 30~m.
Fig. 5.Herpyzonerna inlermedia. Scale bar equals 30 j..lm.
Fig. 6.Scylonema endolithicurn. Scale bar equals 30 j..lm.
See color plates at the end of the volume.
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CYANOBACTERIA AND ASSOOATED MICROORGANISMS (ONE TREE ISLAND, AUSTRALIA)
Sampling and processing
From each area, samples (6-8 replicates) of coral rubble and shell frag-ments were taken.
The samples were fixed in 3% Formaldehyde with seawater. Epilithic algae were carefully removed from the surface. PERENYI-solution (30 ml 0.5% chromic acid; 40 ml 10% nitric acid; 30 ml 90% ethanol) was used to dissolve the carbonate and extract the microendoliths for taxonomic identifi-cation under a dissecting microscope. Additionally, boring galleries in shells of each zone became apparent by using a cast embedding technique. The three dimensional resin-casts of the boring traces were investigated under the SEM and compared to the endolithic algae.
ResuUs
Zone 1 is inhabited by the endolithic cyanobacteria Mastigocoleus tes-tarum (Plate Il, Figs 7, 8) and Plectonema terebrans. The genus Solentiais represented by one species (Plate Il, Fig. 1), the genus Hyellaby at least 3 species (Plate Il, Fig. 2). Associating endolithic species are the chlorophytes Phaeophila dendroidesand/orEugomontia sacculata.
Zone Il is colonized by Mastigocoleus testarum, Plectonema terebrans, Hormathonema violaceo-nigrum and Hormathonema luteo-brunneum (both Plate 2, Figs 3, 4), one species of the genusSolentia(same as zone 1) and one species of the genusEntophysalis,probablyEntophysalis deusta(Plate Il, Fig. 4, arrow). No chlorophytes were found to bore into carbonates from zone II.
Zone lia is mainly inhabited by Hyella balani, Plectonema terebrans, Herpyzonema intermedia(Plate l, Fig. 5),Kyrthutrix dalmatica(Plate l, Fig. 4), Hormathonema violaceo-nigrum and Hormathonema luteo-brunneum, one species of the genus Solentia (different from zones 1 and Il),Mastigocoleus testarumandScytonema endolithicum(Plate l, Fig. 6). In the deeper parts of the consolidated reef crest-carbonates, the green alga Ostreobium quekettii forms green bands (Plate l, Fig. 3, arrow).
Samples from Zone III contain only a few inhabitants: Four species of the genusHyella, Mastigocoleus testarum andHormathonema violaceo-nigrum are regularly found.
No marine euendolithic algae were found to colonize the island (zone IV).
The epilithic cyanobacterium Calothrix(Plate Il, Figs 5, 6) was found to be equally distributed over all zones. It is the dominant epilith frequently found next to small filamentous algae and the coraBine red algaHydrolithon in the upper subtidal and chroococcal cyanobacteria in the higher situated zones. A taxonomical identification of the epiliths other than Calothrix and Hydrolithonwas not attempted.
DISCUSSION
Cribb (1973) investigated the algal vegetation of the Great Barrier Reef.
For Low Isles Reef he defined 4 zones of algal inhabitance. First the Ento-physalis deusta-band for the intertidal, followed by the subtidal zones. The
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ENVIRONMENT: ECOLOGY AND GLOBAL CHANGE
Plate II:
Fig. 1. GenusSo/entia. Seale bar equals50 /lm. - Fig. 2. Genlis Hye//a. Seale bar equaJs50 /lm. - Fig. 3. GenusHormathonel11a. Seale bar equals la/lm. - Fig. 4.
Genera Hormathonema and Entophysalis (arrow). Seale bar equals 50 /lm. -Fig. 5. Genus Ca/othrix. Seale bar eqllals 50 !lm. - Fig. 6. Calothrix crustacea.
Arrow poinls al lerminal heleroeyst. Seale bar equals 50 !lm. - Fig. 7. Mastigo-co/eus testarum. Seale bar equals la/lm. - Fig. 8.Mastigoco/eus testarum. Arrow points al inlercalar heterocyst. Seale bar equals50/lm.
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Lithothamnion-band, the fieshy algal-band and the Seaward platform. Proba-bly because Cribb followed suggestions for the revision of the cyanobacteria, published by Drouet & Daily (1956) his description of the intertidal micro-community did not go into further detail. In their system valid genera with microendolithic species like Hyel!a, Honnathonema or Solentia were grouped together in the single genus Entophysalis. At present the taxonomical inde-pendence of most of the genera and species, united by Drouet& Daily (1956), has been proven by many authors, using morphological methods as weIl as RNA or DNA sequencing.
The only other microendoliths, mentioned by Cribb (1973) are Ostreobium reineckii Bornet and the rock penetrating root of Acctabularia moebii. Today Ostreobium reineckii is considered synonymous with Ostreobium quekettii Bornet& Flahault (Lukas 1973), which was found to form green bands in the consolidated reef carbonates from zone lIa (Plate1,Fig. 3).
Radtke et al. (1997) published on microendolithic zonation of intertidal areas in atlantic and pacifie coastal regions. Tab. 1 compares their findings in atlantic notch carbonates to the results of this study. Although the zones are not entirely corresponding, the algal distribution is very weIl comparable. The transition in species composition from the subtidal zone to the supratidal spray zone is as pronounced in the Atlantic as in samples from
on.
Thegreen algae occur only in the lower submerged zones while the spray zone is Table1.Distribution of microendolithic species in atlantic (Lee Stocking Island,
Bahamas) and pacifie (One Tree Island, Australia) coastal regions.
Zones:AtianticlPacific 1 2 3 4 1 Il lIa III IV
Entophysalis x
Herpyzonema intermedia x x x
Hyellasp. x x x x x
Hyella balani x
Hormathonema violaceo-nigrum x x x x x
Hormatlzonema luteo-brunneum x x x x
Kyrthutrix dalmatica x
Mastigocoleus testarum x x x x x x x
Plectonema terebrans x x x x X
Scytonema endolithicum x x x
Solentiasp. x x x x x x
Plzaeophila/Eugomontia x
Ostreobium queketlii x x x
Conchocelisstages x x x
In arabic numbers zones defined byRADTIŒet al., 1997. In roman numbers zones of this study. Dominant species are presented in bold borders.
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ENVIRONMENT: ECOLOGY AND GLOBAL CHANGE
dominated by specialized cyanobacteria, namely of the genera Hormatho-nema, Scytonema and Hyella.The absence ofMastigocoleus testarum in the atlantic supratidal zone corresponds to the general finding, that this micro-endolithic species is less abundant in the Atlantic (Gektidis, 1997a; Vogel et al., 1996). No explanation can be given for the totallack ofboring red alga in the
on
carbonates.The gradient of humidity cao be viewed as the main control factor for the species composition in the intertidal (see also Schneider, 1976). The zones directly refiect the different ability of the microendolithic species to manage with the declining frequency of moistening towards the island zone. The dif-ferent capability of the microorganisms to produce shielding pigments against the very high irradiance levels constitutes another control factor. In the end this leads to the different colored zones observed on One Tree Island's shores.
Numerous authors have described the high preservation potential of micro-borings and their morphological constancy (i.e. Vogel et al., 1995). The occurrence of specific microendoliths and their constitution of distinct zones in coastal areas is therefore a potential tool for the reconstruction of ancient shorelines. Radtkeet al. (1997) mention the possible use of microborings for the determination of ancient sea levels. Bromley& Asgaard (1993) conclude from the analysis of Pliocene ichnofacies from Rhodes, Greece, that tiring of bioerosion traces in carbonate substrates can serve as an indicator of ancient sea level changes, i.e. rapid transgression. However precondition for the pre-servation of the different tiers is a rapid burial of the ichnofacies. In my opin-ion the preservatopin-ion potential of such changes in general rate very low. The succeding microendolithic community after a sea level change will erase the traces of the older with the combined force of microerosion and grazing (see Schneider& Torunski, 1983 and Gektidis, 1997b for the impact of grazing).
Only the highest sea level will remain recognizable by the originally pre-served microborings since no successors will erase them or coyer them under a new tier of microborings. The picture presented by Bromley & Asgaard (1993) will remain an exception, representing rapid burial and sedimentation conditions at the time of the changing sea level.
Mastigocoleus testarum was found to be the dominant endolith in ail zones. This alga is a heterocystous cyanobacterium (Plate II, Fig. 8) and therefore a potential nitrogen fixing organism. Larkumet al. (1988) investi-gated nitrogen fixation on One Tree Island and found low rates of fixation on the reef crest and the beach rock. The highest rates were measured on the reef fiat and attributed to Scytonema hofmannii and Calothrix crustacea, both epilithic cyanobacteria. Therefore it can be concluded that either Mas-tigocoleus testarum plays a minor role in nitrogen fixation or has just recently started to dominate the intertidal carbonate zone of
on.
Larkum etal. (1988) do not mention this species. Cribb (1973) has positive proof of Mastigocoleus but he did not conduct his research on OTI. A separate study on the potency of nitrogen fixation ofMastigocoleus testarumwould help to answer this question.
132 Bulletin de l'Institut océanographique, Monaco, n° spécial 19 (1999)
CYANOBACTERIA AND ASSOCIATED MICROORGANISMS (ONE TREE ISLAND, AUSTRALIA)
ACKNOWLEDGEMENTS
This study took place during two stays on
on
that focused on the ENCORE project. My involvement in this project during my PhD work would have not been possible without my supervisor Prof. Dr. Vogel and Dr. Kiene. Financial support through the DFG grant to Prof. Dr. Vogel DFG-Vo 90/14 and NOAA grant CMRC-94-24 to Dr. Kiene are gratefully acknowledged. A revision of the manuscript by Prof. Dr. Vogel and Dr. Glaub certainly improved the text.1 would also like to thank the
on
staff and fellow researchers 1 met on the island for the inspiring sunset discussions.REFERENCES
BROMLEY R.G., ASGAARD U., 1993. - Two bioerosion ichnofabrics produced by early and late burial associated with sea-level change. - Geol. Rundsch., 82,276-280.
CRIBB AB., 1973. - The algae of the Great Barrier Reefs. - In: Jones O.A, Endean R. (eds), Biology and Geology of Coral Reefs, Academic Press Inc, New York, London, Il, Biology, 1,47-75.
DROUET F., DAILY W.A, 1956. - A revision of the coccoid Myxophyceae. - Butler Univ. Bot. Stud., 10,218 p.
GEKTIDIS M., 1997a. - Vorkommen, Okologie und Taxonomie von Mikrobohrorgan-ismen in ausgewiihlten Riffbereichen um die Inseln Lee Stocking Island, Bahamas, und One Tree Island Australien. - Ph. D.-Thesis, unpubl. Johann Wolfgang Goethe Universitat, Frankfurt-am-Main, 276 p.
GEKTIDIS M., 1997b. - Microbioerosion in Bahamian ooids. - In: Betzler
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Hüss-ner H. (eds), Vogel-Festschrift Cour. Forsch.-Inst., Senckenberg, Frankfurt-am-Main, 201, 109-121.LARKuM AW.D., KENNEDY I.R., MULLER W., 1988. - Nitrogen fixation on a coral reef. -Marine Biology, 8,143-155.
LUKAsK., 1973. - Taxonomy and ecology of the endolithic microflora of reef corals with a review of the literature on endolithic microphytes. - Ph. D.-thesis, unpubl., University of Rhode Island, Kingston, Rhode Island, 159 p.
RADTKE G., LE CAMPION-ALSUMARD T., GOLUBIC S., 1997. - Microbial assemblages involved in tropical coastal bioerosion: an AtlanticPacific comparison. -Proc 8th Int. Coral Reef Symp., Panama, 2, 1825-1830.
SCHNEIDERl,TORUNSKI H., 1983. - Biokarst on limestone coasts, morphogenesis and sediment production. - PSZNI Mar. Ecol., 4, 45-63.
SCHNEIDERl, 1976. - Biological and Inorganic Factors in the destruction of lîme-stone coasts. - Contr. Sedimentology, 6, 1-112.
VOGELK.,BUNDSCHUH M., GLAUB 1., HOFMANNK.,RADTKE G., SCHMIDT H., 1995.
- Hard substrate ichnocoenoses and their relations to light intensity and marine bathymetry. - Neues Jahrbuch für Geologie und Paliiontologie, Abhandlungen, 195,49-61.
VOGEL K., KIENE W., GEKTIDIS M., RADTKE G., 1996. - Scientific results from investigation of microbial borers and bioerosion in reef environments. - In: Reit-ner J., Neuweiler F., Gunkel F. (eds), Global and regional controls on biogenic sedimentation.I.Reef evolution. Gottinger Arbeiten zur Geologie und Paliionto-logie, G6ttingen, Sb2, 139-143.
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