中国新疆塔里木盆地上奥陶统良里塔格组的钙藻化石

钙藻是可以发生生物钙化作用形成钙质"骨骼"的分属多个门类的藻类的俗称。钙藻最早出现于寒武纪,奥陶纪发生第一次辐射演化。本文系统讨论了绿藻门绒枝藻目(Dasycladales)、羽藻目钙扇藻科(Udoteaceae)的科和属级分类标准和红藻门珊瑚藻科、管孔藻科(Solenoporaceae)属级分类标准及其中各属分类中存在的问题。塔里木盆地晚奥陶世在塔中—巴楚台地和塔北台地发育了一套礁滩相良里塔格组碳酸盐岩,其中含有丰富的钙藻化石。本文系统描述了来自塔里木盆地塔中、巴楚、塔北地区取心井上奥陶统良里塔格组岩层中的钙藻化石11个属15个种。包括绿藻门绒枝藻目西莱特藻科(Seletonellaceae)的Dasyporella,Kazakhstanelia,Vermiporella,Aphroporella,Arthroporella,绿藻门的羽藻目Bryopsidales(siphonales)的钙扇藻科的Dimor phosiphon,Palaeo porella,红藻门珊瑚藻目(Corallinales)的管孔藻科的Solenopora,Parachaetetes及Corallinales incertus familiae的Petro-phyton,以及分类位置不明的Monili porella。其中绒枝藻Ajakmalajsoria被视作Kazakhstanelia的同义名。     

珊瑚礁生态系统中珊瑚藻的生态作用研究进展

珊瑚藻是海洋红藻中的大型钙化藻类,全球分布623种,中国现有记录共77种。随着生态科学研究的广泛展开,人们越来越认识到,珊瑚藻在海洋生态系统中,尤其在维持珊瑚礁生态系统的生物多样性及生态功能中发挥着重要作用。目前,科研人员对有关珊瑚藻的初级生产力、钙化作用以及在诱导底栖无脊椎动物幼虫的附着与变态等方面已有多方面的研究和探索。然而,有关珊瑚藻生态功能的深层次机理问题有待进一步深入研究。文章着重围绕目前珊瑚藻研究中的一些热点问题,从近年来珊瑚藻在珊瑚礁生态系统中的生态功能方面的研究概况进行综述,以期加深人们对珊瑚藻的认识,并促进对珊瑚藻生态功能的进一步深入研究。     

钙质红藻化石的主要类群特征及演化

钙质红藻是指可以发生生物钙化作用在其细胞壁上沉淀碳酸钙的红藻。钙质红藻可以保存为化石,是红藻古生物研究中的重要类群,具有重要的生态意义,但以往的研究对钙质红藻类群的系统分类及地史分布缺乏清晰认识。本文详细综述了钙质红藻化石的系统分类,归属于红藻门(Rhodophyta)红藻纲(Rhodophyceae)的4个目7个科,分别为珊瑚藻亚纲(Corallinophycidae)珊瑚藻目(Corallinales)的珊瑚藻科(Corallinaceae)、石叶藻科(Lithophyllaceae)、宽珊藻科(Mastophoraceae)和管孔藻科(Solenoporaceae),混石藻目(Hapalidiales)的混石藻科(Hapalidiaceae),孢石藻目(Sporolithales)的孢石藻科(Sporolithaceae)以及真红藻亚纲(Florideophycidae)耳壳藻目(Peyssonneliales)的耳壳藻科(Peyssonneliaceae)。最早的钙质红藻为管孔藻科,出现于中奥陶世,于中新世灭绝。珊瑚藻科最早出现于晚志留世并于白垩纪辐射演化至今,其他科均于白垩纪...     

西沙群岛永乐环礁琛科2井的珊瑚藻组成及其水深指示意义

本文对中国南海西沙群岛琛科2井中新世以来的珊瑚藻组成进行了初步研究,共识别出3科4亚科11属,包括石叶藻亚科石叶藻属(Lithophyllum)和蟹手藻属(Amphiroa);宽珊藻亚科似绵藻属(Spongites)、新角石藻属(Neogoniolithon)和石孔藻属(Lithoporella);珊瑚藻亚科让氏藻属(Jania)和珊瑚藻属(Corallina),无节珊瑚藻亚科中叶藻属(Mesophyllum)、奇石藻属(Aethesolithon)和石枝藻属(Lithothamnion);孢石藻亚科孢石藻属(Sporolithon)。并得出以下认识:(1)珊瑚藻类群,指示浅水环境;无节珊瑚藻类群,指示深水环境;宽珊藻类群,指示最浅水环境;石叶藻类群,指示浅水环境。(2)琛科2井自下而上分为7个组合:让氏藻属-珊瑚藻属-石孔藻属组合;奇石藻属组合;中叶藻属-石枝藻属组合;似绵藻属组合;石枝藻属组合;中叶藻属-石叶藻属组合;石孔藻属-石叶藻属组合。(3)878.21 m的珊瑚礁碳酸盐岩心,以309.00-312.00 m为界,分为两个大沉积旋回。第一个沉积旋回珊瑚藻组合经历了具关节的珊瑚藻属-让氏藻属-石孔藻属组合,奇石藻属组合,石枝藻属-中叶藻属组合,似绵藻属组合的变化,反映了水体由浅加深,到最后又变浅的过程;第二个沉积旋回珊瑚藻组合出现了似绵藻藻属组合,石枝藻组合,中叶藻属-石叶藻属-石孔藻属组合,石叶藻属组合的变化,反映了水体由浅加深再变浅的珊瑚藻组合的相应变化。     

河北张家口下花园青白口系下马岭组"红藻石"的发现

红藻石由红藻形成。绝大部分红藻石与珊瑚藻有关。珊瑚藻形成的红藻石发育于中新生代,早古生代有管孔藻形成的红藻石。本文记录了发现于下花园地区的新元古代青白口系下马岭组四段的红藻石。这类红藻石的中心部分被沥青充填。通过薄片观察发现沥青饼的周围硅化部分存在两类红藻四分孢子囊：一类四分孢子囊包埋于球状构造内,另一类四分孢子囊包埋于叶片状构造内。     

西伯利亚地台早寒武世钙藻的发育特征

西伯利亚地台的新元古代到早寒武世间的钙藻化石特别丰富,为研究钙藻化石的发育历史提供了模式。在几次演化事件背景下记录了演化的两次转折,其中一个是藻类的普遍钙化,还有一个是Botomian晚期到Toyonian早期之间在西伯利亚地台缺失钙藻化石记录,而在其它地区包括西伯利亚地台的边缘(Altay—Sayan地区),钙藻的丰度却达到了最大。     

福建宁化泉下黄龙组的四射珊瑚动物群*

福建宁化泉下出露的晚石炭世碳酸盐地层以黄龙组最为发育,富含珊瑚、(竹蜓)类等化石。1983年秋,笔者等详细测制了该剖面,并逐层采集化石。经室内系统研究,共获四射珊瑚27属59种,包括2新属6新种。根据它们在地层中的分布规律,笔者建立了2个珊瑚组合,即下部Yinophyllum组合和上部Protoivanovia-Arachnastraea组合,后者可进一步划分为2个亚组合。如此丰富的四射珊瑚动物群在我国同期地层中尚不多见,这一四射珊瑚动物群的发现,对全面了解我国这一时期四射珊瑚动物群的总体面貌,对黄龙组的划分、对比都有较大的意义。本文描述的珊瑚化石均采自福建宁化泉上镇泉下石灰窑边,化石鉴定得到赵嘉明副研究员的帮助,化石照片由胡尚卿及解小健摄制,谨此一并致谢。     

伞藻

伞藻属(Acetabularia)是广泛分布于亚热带和热带海岸的单细胞绿藻,它生长在贝壳、珊瑚碎片或其他藻类之上,植物体钙化,成熟的植物体一般有几厘米高,某些大形种可达10厘米以上,较小的种有几毫米高。欧洲人称伞藻为“美人鱼的酒杯”或“美人鱼的阳伞”。在我国的广东和广西沿海、海南岛和西沙群岛等地有伞藻(A.caliculus)、棒形伞藻(A.clavata)等。     

DNA条形码在淡水红藻中的应用评价——基于串珠藻科植物

研究采用4种DNA序列, 分析了各片段序列特征以及在串珠藻科植物中种属水平的鉴定能力, 包括线粒体COI-5P、cox2-3 spacer序列, 以及叶绿体rbcL、UPA序列。结果表明, COI-5P、cox2-3 spacer、UPA以及rbcL序列的PCR扩增成功率分别为96%、100%、96%和98%。其中, COI-5P、cox2-3 spacer和UPA的片段大小符合标准DNA条形码的判定标准, 即片段大小在300—800 bp, 能够通过单对引物双向测序获得。系统发育分析的结果显示, 这4种DNA片段在串珠藻属植物的鉴定中能够鉴定大部分的种类, 但COI-5P、cox2-3 spacer以及rbcL序列均不能将两种中国特有种洪洞串珠藻B. hongdongense和长柄串珠藻B. longipedicellatum与弧形串珠藻B. arcuatum分开。在种水平的鉴定中, UPA基因的种间差异最大, 显示了较好的分离效果, 在串珠藻科植物的鉴定中可以作为一个标准的DNA条形码。     

有关刺丝胞动物分类和古生代珊瑚起源及其亲缘关系研究的最新进展

国际最新研究表明,刺丝胞动物门包括水螅,钵水母和珊瑚3个纲,古生代的床板珊瑚和皱纹珊瑚以及中,新生代的石珊瑚是珊瑚纲中最主要的3个月,分别出现于早奥陶世,中奥陶世和中三叠世,它们在地层的划分,对比和古地理环境的解释方面都起着非常重要的作用,寒武纪发现的所谓“珊瑚”化石,大部分不是珊瑚,而应归属于藻类,海绵和苔藓虫,只有其中的一部分可能是珊瑚或刺丝胞,但它们并不属于真正的皱纹珊瑚或床板珊瑚,皱纹珊瑚不是起源于寒武纪的这些所谓的“珊瑚化石”,而可能是起源于一种具有骨骼的单体海葵,奥陶纪和二叠纪都曾先后出现类似于石珊瑚的化石,但它们并不是中三叠世石珊瑚直接的祖先,石珊瑚也不是起源于皱纹珊瑚而可能是起源于一种或多种带骨骼的海葵,古生代的珊瑚化石是研究生物灭绝,复苏事件最理想的生物门类之一,奥陶纪末的O／S和晚泥盆地的F／F这两次灭绝事件使许多珊瑚分类单元惨遭浩劫,而二叠纪末的P／T灭绝事件则使全部古生代的皱纹珊瑚和床板珊瑚消亡。     

RE-ASSESSMENT OF THE TYPE COLLECTIONS OF CORALLINALEAN GENERA (CORALLINALES, RHODOPHYTA) DESCRIBED BY V. P. MASLOV

Abstract:  From 1935 to 1962 Maslov published two monographs and several other papers on the taxonomy of fossil calcareous algae of diverse ages from the large geographical area of the former USSR. Among many other taxa, he described five new genera ( Solenophyllum , Palaeophyllum , Mesolithon , Bicorium and Tomilithon , as a subgenus of Parachaetetes Deninger) which he attributed to the Corallinaceae, and the new genus Karpathia , which he included in the Squamariaceae. Type material of these taxa, except for Mesolithon , is housed in the Geological Institute of the Russian Academy of Sciences, Moscow. Re-examination of the genus types from a modern perspective of coralline algal taxonomy shows that Karpathia is a validly published genus of corallinaceans (subfamily Mastophoroideae) to which several Cenozoic fossil species can be assigned. In contrast, the holotype of P. elegans , the type species of Palaeophyllum , cannot be assigned to any subfamily within the Corallinaceae and its preserved features are inadequate for confidently delimiting a separate genus. Solenophyllum is a valid genus in which Palaeozoic representatives of Corallinales formerly attributed to Parachaetetes Deninger can be included. Tomilithon is considered a younger heterotypic synonym of Solenophyllum . The algal nature of the bioclasts in the type of Bicorium is uncertain.     

Taxonomic and biostratigraphical re-assessments of Subterraniphyllum Elliott (Corallinales, Rhodophyta)

A taxonomic and biostratigraphical re‐assessment of Subterraniphyllum Elliott (Corallinales, Rhodophyta) is presented. Results from studies of the type collection and of newly collected material from north‐eastern Italy and northern Slovenia have shown that this taxon is not a geniculate coralline red alga as originally suggested by Elliott and most subsequent authors. Vegetatively, Subterraniphyllum most closely resembles certain living members of the Corallinales; however, the phenetic and phylogenetic relationships of Subterraniphyllum to other Corallinales cannot be determined with greater certainty. The exclusion of Subterraniphyllum from any group of Corallinaceae with genicula is based on unequivocal evidence that branch formation does not involve the occurrence of genicula. Subterraniphyllum seems to be restricted to the Oligocene. Reports of occurrences in Upper Eocene and Lower Miocene sediments cannot be substantiated. Subterraniphyllum, however, cannot be considered a useful stratigraphical marker until further data on its occurrence in well‐dated carbonate sequences are acquired. This study illustrates the problems associated with placing fossil coralline algal specimens into geniculate genera without the preservation of relevant morphological characters. This is especially true in the absence of the careful assessment of fossil material with respect to current taxonomic concepts of geniculate coralline genera, all of which are based on studies of living species. According to the current concepts for geniculate coralline genera, the placing of fossil specimens into geniculate genera without appropriate evidence must be avoided by grouping all potentially geniculate fragments under the informal group ‘Geniculate sensu lato’. Furthermore, for all those many fossil specimens where unequivocal evidence is not present, it is possible to utilize ‘form genera’ based on characters that are normally preserved. This leads to creating a consistent, workable system of applying names to most fossil corallines so that they can be reliably used in relation to stratigraphical and palaeoecological studies.     

MOLECULAR SYSTEMATICS OF THE XANTHOPHYCEAE

The Corallinales includes ca. 40 genera of calcified red seaweeds. Species are of two distinct morphotypes; those that possess genicula (uncalcified nodes) and those that lack genicula. Most nongeniculate species take the form of crusts. The presence (or absence) of genicula, secondary pit connections, and tetrasporangial conceptacle features have traditionally been used as key characters for delimiting coralline subfamilies. In this study, nuclear encoded 18S and 26S r RNA gene sequences were determined and used to reexamine relationships among coralline taxa. Separate and combined phylogenetic analyses of these data yielded similar trees in which four major lineages are resolved. Heydrichia and Sporolithon (Sporolithaceae) are positioned at the base of the tree and appear to be distantly related to other species examined. Within the Corallinaceae, the nongeniculate Melobesioideae is resolved as a monophyletic group. All members of this subfamily produce mutiporate tetraspoangial conceptacles. The Corallinoideae, which are characterized by unizonate genicula, are resolved as sister to a clade containing species placed in the Lithophylloideae, Mastophoroideae and Metagoniolithoideae. The molecular data indicate that geniculate and nongeniculate species characterized by the presence of secondary pit connections are closely related. For example, both data sets robustly support a sister taxon relationship between Amphiroa and Titanoderma. Our results indicate that: 1) all taxa in which secondary pit connections are present should be referred to the Lithophylloideae and, 2) genicula are nonhomologous structures that are independently derived in Amphiroa, Lithothrix, Metagoniolithon and the last common ancestor of the Corallinoideae.     

CHOREONEMA (CORALLINALES, RHODOPHYTA): 18S rDNA PHYLOGENY AND RESURRECTION OF THE HAPALIDIACEAE FOR THE SUBFAMILIES CHOREONEMATOIDEAE, AUSTROLITHOIDEAE, AND MELOBESIOIDEAE

Phylogenetic analyses of 18S rDNA gene data for Choreonema thuretii (Corallinales, Rhodophyta) and available data for other coralline red algae indicated that Choreonema belongs to the same lineage as other taxa of Corallinales possessing tetra/bisporangial conceptacles with multiporate plates. These results, when integrated with extant morphological/anatomical data, ultrastructural data, and taxonomic data led to the conclusion that all taxa of Corallinales possessing multiporate conceptacles belong to a distinct family, the Hapalidiaceae. Recognition of the Hapalidiaceae as a distinct family was supported both phylogenetically and phenetically. The Hapalidiaceae includes those taxa of Corallinales whose tetrasporangia produce zonately arranged spores and whose tetra/bisporangia are borne in conceptacles, produce apical plugs, and develop beneath multiporate plates. The Hapalidiaceae includes the subfamilies Choreonematoideae, Melobesioideae, and Austrolithoideae, formerly placed in the Corallinaceae sensu lato . The Choreonematoideae lack cell connections between adjacent vegetative filaments and have a multiporate plate that is acellular at maturity, consisting only of a calcium carbonate matrix. The Austrolithoideae and Melobesioideae both have cellular pore plates; taxa of Melobesioideae have cell fusions between cells of adjacent vegetative filaments, whereas taxa of Austrolithoideae lack cellular connections between adjacent vegetative filaments. Inclusion of the Austrolithoideae in the Hapalidiaceae was based entirely on morphological/anatomical evidence; molecular evidence currently is lacking. Relevant historical and nomenclatural data are included.     

PHYLOGENY AND CLASSIFICATION OF REEF‐BUILDING CORALLINE ALGAE (CORALLINALES,RHODOPHYTA)

The Corallinales includes ca. 40 genera of calcified red seaweeds. Species are of two distinct morphotypes; those that possess genicula (uncalcified nodes) and those that lack genicula. Most nongeniculate species take the form of crusts. The presence (or absence) of genicula, secondary pit connections, and tetrasporangial conceptacle features have traditionally been used as key characters for delimiting coralline subfamilies. In this study, nuclear encoded 18S and 26S rRNA gene sequences were determined and used to reexamine relationships among coralline taxa. Separate and combined phylogenetic analyses of these data yielded similar trees in which four major lineages are resolved. Heydrichia and Sporolithon (Sporolithaceae) are positioned at the base of the tree and appear to be distantly related to other species examined. Within the Corallinaceae, the nongeniculate Melobesioideae is resolved as a monophyletic group. All members of this subfamily produce mutiporate tetraspoangial conceptacles. The Corallinoideae, which are characterized by unizonate genicula, are resolved as sister to a clade containing species placed in the Lithophylloideae, Mastophoroideae and Metagoniolithoideae. The molecular data indicate that geniculate and nongeniculate species characterized by the presence of secondary pit connections are closely related. For example, both data sets robustly support a sister taxon relationship between Amphiroa and Titanoderma. Our results indicate that: 1) all taxa in which secondary pit connections are present should be referred to the Lithophylloideae and, 2) genicula are nonhomologous structures that are independently derived in Amphiroa, Lithothrix, Metagoniolithon and the last common ancestor of the Corallinoideae.     

Lithophyllum cuneatum sp. nov. (Corallinaceae, Rhodophyta), a new species of non-geniculate coralline alga semi-endophytic in Hydrolithon onkodes and Neogoniolithon sp. from Fiji, South Pacific

A new species of semi-endophytic coralline alga, Lithophyllum cuneatum (Corallinaceae: Lithophylloideae), is described from Fiji. The species is characterized by a wedge-like thallus that is partially buried in the thallus of the host coralline, Hydrolithon onkodes (Heydrich) Penrose et Woelkerling or occasionally Neogoniolithon sp., and that appears at the surface of the host as a small pustule that is usually paler in color than the host. The thallus consists of erect filaments that are derived from a single cell. The basal cell, when visible, is non-palisade, and areas of bistratose margin are absent. Cells of contiguous erect filaments are joined by secondary pit connections. Epithallial cells are present in 2–3 layers, and individual trichocytes are common. Gametangial plants are dioecious. Male conceptacles have simple spermatangial systems that are confined to the floors of their elliptical chambers. Carposporangial conceptacles contain 5–8 celled gonimoblast filaments that are borne at the margin of a more-or-less discoid fusion cell, and so occupy the periphery of the elliptical conceptacle chambers. Tetrasporangial conceptacles are uniporate, with roofs formed from peripheral filaments, and chambers lack a central columella of sterile filaments. Despite its semi-endophytic nature, haustorial cells are absent, and plastids and pigmentation are present.     

Microfacies analysis and palaeoenvironmental interpretation of Lower Oligocene, shallow-water carbonates (Gornji Grad Beds, Slovenia)

Summary The microfacies and palaeoenvironment of Lower Oligocene carbonates of the Gornji Gradbeds from Slovenia are investigated. These beds form part of a transgressive succession overlying both terrigenous sediments (sand-stones and conglomerates) and marine carbonates of Eocene age as well as transgressing directly over Triassic lime-stones. They are followed by foraminiferal rich marls. The carbonates were investigated using multivariate statistical techniques on point counts of thin sections. They are dominated by poorly sorted biogenic rudstones with pack-/wackestone matrix; pack- and grainstones are subordinate. The biogenic components of the carbonates are dominated by coralline red algae (9 genera with 11 species), corals, small benthic, large benthic, and encrusting foraminifera as well as bivalves. Gastropods, bryozoans, brachiopods, echinoderms, serpulids, and green algae are subordinate. The well preserved components allow details pertaining to taxonomy, growth-forms and taphonomic features to be observed. The following carbonate facies are distinguished: 1) nummulitic, 2) bivalve, 3) foraminiferal—coralline algal, 4) grainstone, 5) coralline alga, 6) coralline algal—coral, and 7) coral facies. All the carbonate facies represent fully marine conditions within the photic zone. They are interpreted with respect to substrate composition and stability, water turbulence, terrigenous input and light.     

Responses of crustose corallines to epiphyte and canopy cover

Although a dense cover of epiphytes is generally considered to be harmful for some coralline algae (Corallinaceae, Rhodophyta), crustose corallines in the littoral zone seem to be preserved from bleaching when covered by canopy plants and epiphytes during summer. This study aimed to test the responses of coralline crusts to epiphytes and canopy algae and their interaction with grazing limpets. Growth rates and color changes were followed in two crust species in areas with or without canopy algae in the Isle of Man, British Isles. Limpets were excluded, to allow epiphytes to grow upon crusts. Responses were measured both on pieces of crusts upon acrylic plates and on crusts growing naturally on the shore. Fucus canopy and epiphytic Enteromorpha significantly influenced the crusts' growth, depending on season. Epiphytes reduced the light levels beneath by up to 78%, more than the canopy algae (62%). Crusts exposed outside the canopy bleached in summer, but gradually restored their color once they were covered by epiphytes. The fast-growing Phymatolithon lenormandii (Aresch.) Adey recovered its coloration more quickly than the slow-growing P. purpureum (P. et H. Crouan) Woelkerling et Irvine. However, neither crust species could restore its color when epiphytes were reduced by grazing limpets, Patella vulgata L. Bleaching did not kill the crusts, but seemed to interfere with crusts' growth. Restoration of pigmentation was quantified for the first time on bleached coralline crusts. Epiphyte and canopy algae were experimentally shown to be beneficial, probably by providing shade and also protecting crusts from desiccation.     

ANALYSIS OF ANCIENT DNA FROM FOSSIL CORALLINES (CORALLINALES,RHODOPHYTA)1

The field of molecular paleontology has recently made significant contributions to anthropology and biology. Hundreds of ancient DNA studies have been published, but none has targeted fossil coralline algae. Using regions of the SSU gene, we analyzed rDNA from fossil coralline algae of varying ages and states of preservation from Spain, Papua New Guinea (PNG), and the Great Barrier Reef (GBR). Specimens from PNG, GBR, and some localities from Spain did not contain endogenous ancient DNA. Reproducible sequence data were obtained from specimens ～550 years old from near Cadiz, Spain, and from rocky‐shore deposits in Carboneras, Almeria Province of Spain (～78,000 years before present [YBP]). Based on BLAST searches and a phylogenetic analysis of sequences, an undescribed coralline alga belonging to the Melobesioideae was discovered in the Carboneras material as well as the following coralline genera: Jania, Lithophyllum, Lithothamnion, Mesophyllum, and Phymatolithon. DNA from fleshy brown and red macroalgae was also discovered in the specimens from Carboneras. The coralline algae identified using molecular techniques were in agreement with those based on morphological methods. The identified taxa are common in the present‐day southeastern Spain littoral zone. Amino acid racemization, concentration ratios, and specific concentrations failed to show a correlation between biomolecular preservation and PCR amplification success. Results suggest that molecular investigations on fossil algae, although limited by technical difficulties, are feasible. Validity of our results was established using authentication criteria and a self‐critical approach to compliance.     

Phylomineralogy of the Coralline red algae: Correlation of skeletal mineralogy with molecular phylogeny

The coralline algae in the orders Corallinales and Sporolithales (subclass Corallinophycidae), with their high degree of mineralogical variability, pose a challenge to projections regarding mineralogy and response to ocean acidification. Here we relate skeletal carbonate mineralogy to a well-established phylogenetic framework and draw inferences about the effects of future changes in sea-water chemistry on these calcified red algae. A collection of 191 coralline algal specimens from New Zealand, representing 13 genera and 28 species, included members of three families: Corallinaceae, Hapalidiaceae, and Sporolithaceae. While most skeletal specimens were entirely calcitic (range: 73–100 wt.% calcite, mean 97 wt.% calcite, std dev = 5, n = 172), a considerable number contained at least some aragonite. Mg in calcite ranged from 10.5 to 16.4 wt.% MgCO₃, with a mean of 13.1 wt.% MgCO₃ (std dev = 1.1, n = 172). The genera Mesophyllum and Lithophyllum were especially variable. Growth habit, too, was related to mineralogy: geniculate coralline algae do not generally contain any aragonite. Mg content varied among coralline families: the Corallinaceae had the highest Mg content, followed by the Sporolithaceae and the Hapalidiaceae. Despite the significant differences among families, variation and overlap prevent the use of carbonate mineralogy as a taxonomic character in the coralline algae. Latitude (as a proxy for water temperature) had only a slight relationship to Mg content in coralline algae, contrary to trends observed in other biomineralising taxa. Temperate magnesium calcites, like those produced by coralline algae, are particularly vulnerable to ocean acidification. Changes in biomineralisation or species distribution may occur over the next few decades, particularly to species producing high-Mg calcite, as pH and CO₂ dynamics change in coastal temperate oceans.