A close look at late carboniferous algal mounds: Schulterkofel,Carnic Alps,Austria

Summary During the uppermost Carboniferous and lowermost Permian algal mounds were formed in inner shelf settings of the Carnic Alps (Austria/Italy). A specific mound type, characterized by the dominance of the dasyclad green alga Anthracoporella was studied in detail with regard to geometry, relationship between mound and intermound rocks, composition of the sediment, biota and diagenetic criteria. The two meter-sized mounds studied, occur within depositional sequences of transgressive systems tracts in the Lower Pseudoschwagerina Limestones (uppermost Gzhelian) at the flank of the Schulterkofel. The mounds consist of an Anthracoporella core facies with a spongecrust boundstone facies at the base and at the top. The massive limestones of the Anthracoporella core facies exhibit abundant algal tufts and bushes, frequently in life position. The limestones of the intermound facies represented by thin-bedded bioclastic wackestones and packstones with abundant phylloid algae underlie and overlie the mounds. Intercalations of intermound beds within the mound facies indicate sporadic disruption of mound growth. Onlapping of intermound beds on steep mound flanks indicate rapid stabilization and lithification of mound flanks and the existence of a positive paleorelief. Asymmetrical shape of the mounds may be current controlled. Mound and intermound biota differ in the prevailing algae but are relatively similar with regard to associated foraminifera. Conspicuous differences concern bioerosion and biogenic encrustations. Bothare, high in intermound areas but low in the Anthracoporella core facies. The mounds show no ecological zonation. The mounds grew by in-place accumulation of disintegrated algal material and trapped bioclastic material between erect algal thalli. The comparison of the various Anthracoporella mounds demonstrates that almost each mound had ist own history. Establishing a general model for these mounds is a hazardous venture.     

Biostratigraphic subdivision and correlation of Uppermost Carboniferous/Lower Permian sediments in the Southern Alps: Fusulinoidean and condont faunas from the Carnic Alps (Austria/Italy), Karavanke Mountains (Slovenia), and Southern Urals (Russia)

Summary In order to establish a refined biostratigraphic subdivision and correlation of the Uppermost Carboniferous/Lower Permian deposits of the Southern Alps (Carnic Alps, Karavanke Mountains; Austria/Italy/Slovenia), two major microfossil groups (fusulinoideans, conodonts) were investigated within the same sample. The fusulinoidean species diversity (71 species, including five new species and three new subspecies) and generic composition were reviewed and complemented. Additionally, the data on fusulinoidean assemblages were supplemented by co-occurring conodont faunas (seven species). Accompanying studies on material from the type sections of the Southern Urals (Russia) were made to improve the biostratigraphic correlation with the Russian standard zonation and to discuss paleobiogeographical aspects of the faunal associations. An integrated microfacies analysis of the sampled material in the Southern Alps serves to evaluate the relationships between certain genera and specific microfacies types. The fusulinoidean fauna of the Lower “Pseudoschwagerina” Limestone is of late Gzhelian age. The Carboniferous/Permian boundary is close to the base of the Grenzland Formation, which covers the entire Asselian and a part of the Sakmarian. The Upper “Pseudoschwagerina” Limestone and Trogkofel Limestone are Lake Sakmarian to Artinskian. The studies sequences in the Karavanke Mountains. formerly known as “carbonate and clastic Trogkofel beds”, correlate to the Lower “Pseudoschwagerina” Limestone, respectively with parts of the Grenzland Formation. Due to the lithologic differences, new formation names (Dolzanova Soteska Fm., Born Fm.) were introduced for the so-called “Trogkofel” Limestone along the Dolzanova Soteska. Whereas late Gzhelian/Asselian fusulinoidean faunas of the Southern Alps correspond to the Southern Uralian faunas to a large extent, Sakmarian and Artinskian faunas reveal an increasing divergence in species and genus composition. Climatic as well as geographic barriers may have prevennted the dispersal of Paleotethyan taxa into the Southern Urals. Biostratigraphic correlation of Sakmarian to Artinskian deposits is therefore possible only on the basis of the sparse conodont faunas.     

Permian bryozoans of the NW-tethys

Summary Permian bryozoan faunas from the Lower Permian sequences of the Carnic Alps (UpperPseudoschwagerina Formation and Trogkofel Formation) and from some other Permian units of the NW-Tethys (Sicily, Tunisia) include cystoporid, trepostomid, fenestellid, rhabdomesid, and timanodictyid taxa. Fenestellids and cystoporids species dominate. The Lower Permian bryozoan fauna of the Carnic Alps displays close relations to faunas of Sakmarian-Artinskian age of the Russian Platform and Pamir as well as of the Lower Permian of Australia. Bryozoans from Permian sequences of Sicily and Tunisia display relations to the Permian faunas of Indonesia and Australia.     

The schulterkofel section in the Carnic Alps,Austria: Implications for the carboniferous-permian boundary

Summary The upper part of the LowerPseudoschwagerina Limestone (Rattendorf Group), outcropping on the northwestern flank of Schulterkofel Mountain, Carnic Alps (Austria) is described with special emphasis on fusulinid microfossils and facies. This fusulinid-rich section offers an ideal opportunity for biostratigraphy in defining the Permo-Carboniferous boundary in this region. The LowerPseudoschwagerina Limestone is composed of shallow-marine limestones with intercalated thin siltstone and sandstone beds. Fusulinid limestones are represented by two types of wackestones, both containing large quantities of smaller foraminifers. Fusulinid grainstones are rare. Limestones rich in fusulinids were found only within the bedded limestone facies in beds both below and especially above siliciclastic intercalations. This may indicate that the best living conditions for fusulinids existed immediately before and especially after the climax of a regressive phase (sea-level lowstand). The fusulinid limestones were deposited within a protected, shallow-marine shelf environment with normal salinity. Pseudoschwagerinid fusulinids appear in the upper part of the LowerPseudoschwagerina Limestone, in samples SK 107d (undeterminable species) and SK 108, i.e. between 92 m and 93 m above the base of the section within a bedded limestone immediately above the uppermost clastic intercalation. The fusulinid fauna is represented by about 30 species belonging to only a few genera. Species ofTriticites andRugosofusulina dominate, whereas those ofDaixina, Rugosochusenella andPseudofusulina are rare. A characteristic feature of the fauna is the strong similarity with fusulinid faunas described from Russia as well as from Middle and East Asia. Some of the described fusulinids are new for the Carnic Alps. The first appearance ofPseudoschwagerina andOccidentoschwagerina (Occidentoschwagerina alpina Zone) in the upper part of the LowerPseudoschwagerina Limestone in the Schulterkofel section defines the position of the Carboniferous-Permian boundary.     

Biostratigraphical correlation of late carboniferous (Kasimovian) sections in the Carnic Alps (Austria/Italy): Integrated paleontological data, facies, and discussion

Summary The fusulinacean faunal content of the Bombaso Fm. and lower part of the Auernig Group (Carnic Alps, Austria/Italy) is reviewed and completed by data on conodonts and algae. Four different faunal associations can be distinguished within this stratigraphic interval. The beginning of the postvariscan sedimentation in the investigated sections is diachronous, shifting in age from early Kasimovian (Krevyakinian) at Zollner Lake and Mt. Auernig, early to middle Kasimovian at Cima Val di Puartis to late Kasimovian (Dorogomilovian) at Mt. Ro?kofel. The sections analyzed consist of shallow-marine sediments, which differ in microfacies of limestones and partly in biotic assemblages. They are geographically isolated and could not be traced laterally for lithologic correlation in the field. The biostratigraphic correlation with the faunas of the stratotype sections in the Moscow Basin is hindered by the searceness of fusulinaceans in the critical levels, especially in the lowermost Kasimovian, and differences in the species composition. A biostratigraphic correlation of the Bombaso Fm. and basal part of the Auernig Group with the Peski Fm. (Myachkovian) of the Moscow Basin, as suggested byDavydov & Krainer (1999), is not confirmed by our results. Due to our taxonomic reinterpretation of the oldest fauna (Protriticites aff.permirus with distinct mural pores and largeBeedeina (Pseudotriticites) asiaticus) a lowermost Kasimovian (Lower Krevyakinian) age is more probable. This correlation is supported by the co-occurring conodont fauna, which is suggested to belong to the zone of “Streptognathodus subexcelsus”. This biozone reaches from the topmost Peski Fm. to the Suvorovo Fm. (Lower Krevyakinian) in the Moscow Basin, and may be correlated with the uppermost Desmoinesian of the Midcontinent North America. Fusulinaceans and conodonts of the overlying strata at Zollner Lake and from the sections at Cima Val di Puartis and Mt. Auernig most probably correspond to the upper Krevyakinian/lowermost Khamovnikian of the Russian platform (Lower Missourian of the Midcontinent North America). The algal associations (Dvinella, Beresella, Herakella) from these lowermost strata are unique for the Carnic Alps. Their stratigraphic range points to Moscovian-Kasimovian as well, and fits with the fusulinacean and conodont data. Sediments of the N?lbling Group (=“untere kalkreiche Schichtgruppe”) have their correlative levels in the upper Khamovnikian, but reach higher into the Dorogomilovian. More reliable correlations are possible with the fusulinacean faunas of the Cantabrian Mts. and Central Asia, based on the coincidence of several species. A revised biostratigraphic correlation with the different remote basins of the Paleotethyan realm and the Russian Platform is given, based on own data and recent results by the members of the SCCS Working group to define a GSSP close to the Moscovian/Kasimovian boundary. The sequence-stratigraphic scheme, the systematics, and the biostratigraphic correlation ofDavydov & Krainer (1999) are discussed.     

Anthracoporella mounds in the Late Carboniferous Auernig Group,Carnic Alps (Austria)

Summary A heretofore undocumented example of skeletal mounds formed by the dasycladacean algaAnthracoporella spectabilis is described from mixed carbonate-clastic cycles (Auernig cyclothems) of the Late Carboniferous (Gzhelian) Auernig Group of the central Carnic Alps in southern Austria. The massive mound facies forms biostromal reef mounds that are up to several m thick and extend laterally over more than 100 m. The mound facies is developed in the middle of bedded limestones, which are up to 16 m thick. These limestones formed during relative sea-level highstands when clastic influx was near zero. The mound facies is characterized by well developed baffler and binder guilds and does not show any horizontal or vertical zonation. Within the massive mound faciesAnthracoporella is frequently found in growth position forming bafflestones and wackestones composed of abundantAnthracoporella skeletons which toppled in situ or drifted slightly.Anthracoporella grew in such profusion that it dominated the available sea bottom living space, forming ‘algal meadows’ which acted as efficient sediment producers and bafflers. BecauseAnthracoporella could not provide a substantial reef framework, and could not withstand high water turbulence, the biostromal skeletal mounds accumulated in shallow, quiet water below the active wave base in water depths less than 30 m. The massive mound facies is under- and overlain by, and laterally grades into bedded, fossiliferous limestones of the intermound facies, composed mainly of different types of wackestones and packstones. Individual beds containAnthracoporella andArchaeolithophyllum missouriense in growth position, forming “micromounds’. Two stages of mound formation are recognized: (1) the stabilization stage when bioclastic wackestones accumulated, and (2) the skeletal mound stage when the sea-bottom was colonized byAnthracoporella and other members of the baffler and binder guilds, formingAnthracoporella bafflestones and wackestones of the mound facies. A slight drop in sea-level led to the termination of the mound growth and accumulation of organic debris, particularly calcareous algae, fusulinids, crinoids and bryozoans, forming well bedded limestones, which overlie the mound facies     

Reefal and mud mound facies development in the Lower Devonian La Vid Group at the Colle outcrops (León province, Cantabrian Zone, NW Spain)

In the locality of Colle (Cantabrian Zone, NW Spain), the upper part of the Valporquero Shale Formation (Emsian, La Vid Group) contains an interval of shales and marlstones (barren, greenish-grey shales and fossiliferous, greenish-grey or reddish shales/marlstones) with beds and packages of homogeneous and cross-bedded skeletal limestones. Metre-scale mud mounds and coral biostromes occur encased in the fossiliferous reddish and greenish-grey shale/marlstones, respectively, with the coral biostromes overlying conspicuous skeletal limestone bodies. These rocks were deposited on a carbonate ramp, ranging from above storm wave base for the cross-bedded skeletal limestones to below the storm wave base for the remaining deposits, organic buildups included. The vertical stacking of these facies and the occurrence of the two types of buildups are interpreted to reflect the interplay among several (possibly 4th and 5th) orders of relative sea-level variations, during a 3rd-order highstand. Coral biostromes occur in early 5th-order transgressive system tracts developed within late 4th-order highstand, and are interpreted to have thrived on a stable granular substrate (skeletal limestones) in non-turbid waters, being later aborted by the onset of muddy sedimentation. Biostrome features suggest that they developed under environmental conditions essentially different from those related to the sedimentation of their granular substrate. Mud mounds occur in 5th-order transgressive and early highstand system tracts tied to early 4th-order sea-level rise. Field relationships suggest that mud mounds grew coevally with muddy sedimentation, with high-frequency variations in carbonate vs. terrigenous mud sedimentation influencing their development.An erratum to this article can be found at     

Effects of competition and herbivory on interactions between a hard coral and a brown alga

Despite widespread acceptance of the negative effects of macroalgae on corals, very few studies have experimentally tested the competitive nature of the interaction, and most have ignored the potential effects of corals on algae. We report the effects of herbivory and competition on the growth of the branching scleractinian coral Porites cylindrica Dana and the creeping foliose brown alga Lobophora variegata (Lamouroux) Womersley, on an inshore fringing reef of the central Great Barrier Reef. L. variegata overgrows branches of P. cylindrica from the base up, forming a distinct boundary between the alga and the coral tissue. The experiment used exclusion cages to test for effects of herbivores, and removal of algae and coral tissue, at their interaction boundary, to test for inhibition of the competitors by each other. Comparisons of coral branches with the algae present or removed showed that the presence and overgrowth of the alga caused significant coral tissue mortality. Comparisons of branches with coral tissue unmanipulated or damaged showed that the coral inhibited the overgrowth by L. variegata, but that the algae were markedly superior competitors. Importantly, reduced herbivory resulted in faster algal growth and consequent overgrowth and mortality of coral tissue, demonstrating the critical importance of herbivory to the outcome of the competitive interaction.     

Attached vermiform gastropods in Carboniferous marginal marine stromatolites and biostromes

Tubiform fossils conventionally referred to Serpula cf. advena Salter and species of Spirorbis Lamarck from the British Lower Limestone Shales and Border Group (Lower Carboniferous) are re-examined. They occur in peritidal carbonate environments of schizohaline aspect. These fossils superficially resemble calcareous polychaete tubes but have skeletal characters, including molluscan wall structure, numerous internal septa, and protoconch, which indicate that they represent a new group of substrate-attached, disjunctly coiled gastropods. They resemble archaeogastropods in internal morphology of the skeleton but show parallels in external form and occurrence with the extant Vermetidae. There are two principal modes of occurrence: (1) erect tubes forming intertidal biostromes associated with non-skeletal algal laminites, and (2) prostrate discoidal tubes encrusting subtidal skeletal stromatolites or occasionally forming larger irregular bioherms. These biostromes and bioherms are comparable in structure to Recent vermetid reef developments.     

Late Devonian - Early Carboniferous vertebrate microremains from the Carnic Alps, northern Italy

Vertebrate microremains from the Late Devonian-Early Carboniferous of the Carnic Alps are predominantly chondrichthyan, with minor placoderm and actinopterygian remains. The faunas are sparse and, with very few exceptions, occur only in conodont-rich pelagic limestones (Pramosio Limestone) representative of the palmatolepid-bispathodid conodont biofacies. Phoebodont and jalodont chondrichthyans, also reflecting open-ocean environments, predominated during the Famennian, and eventually symmoriids seem to predominate during the Early Carboniferous. The presence of Siamodus in this assemblage gives a new locality for this genus known from few regions in the world and allows confirming its stratigraphical range (limpidus Zone) and its relation to deep-water environments. The Late Devonian vertebrate faunas are tropical and cosmopolitan, having much in common with coeval taxa from the North-Gondwanan margins and Asian terranes. Composition of the vertebrate faunas is consistent with the Carnic Alps terrane having occupied a position intermediate between Gondwana and Laurussia, as hypothesized by various authors, but because of sparsity of the taxa represented and the pronounced cosmopolitan nature of both the conodont and vertebrate faunas, the data are not compelling.     

Paleobiogeographic significance of a new ozawainelloid fusulinid Pseudoacutella partoazari n. sp., from the Asselian (lowermost Permian) of Gaduk (Central Alborz,Iran)

The uppermost Carboniferous–Lower Permian Dorud Group that crops out at the Gaduk section of Central Alborz is over 44 m thick and includes thick sequences of conglomerate, quartzarenite, calcareous sandstone, oncolitic fusulinid limestone, sandy limestone, sandstone and shale. The Toyeh, Emarat and Shah Zeid formations of this Group were dated as latest Gzhelian to Early Sakmarian. A review of the Asselian fusulinids and smaller foraminifers of Iran emphasizes (1) how the foraminiferal assemblages of Alborz and central Iran differ; (2) why non-Pseudofusulina cannot be a nomen substitutum to Pseudofusulina (even if this latter was often misinterpreted in the Tethyan regions). A new smaller fusulinid Pseudoacutella partoazari n. sp. is described from the Emarat Formation (Asselian) that crops out in the Gaduk area. The palaeobiogeographic significance of Pseudoacutella is discussed, because this genus, which was cosmopolitan from Late Bashkirian to Moscovian, became rare in the Upper Pennsylvanian of the USA and the Carnic Alps, and then, very rare in Lower Permian of Texas, Arizona and Iran.     

Host-parasite relationship of the geoduck Panopea abbreviata and the green alga Coccomyxa parasitica in the Argentinean Patagonian coast

The association of the geoduck Panopea abbreviata and the green alga Coccomyxa parasitica is described. The identity of the green alga was confirmed by molecular studies; the alga was found within the hemocytes that infiltrate the connective tissue of the geoduck siphons. Cytological characteristics of hemocytes were not altered by algal infection; very often the algae were seen enveloped by a digestive vacuole within the hemocyte cytoplasm, evidencing diverse degrees of resorption. Connective cells of siphons were rarely infected by C. parasitica. The mean prevalence of C. parasitica was higher (82%) in San Matías Gulf (42°00′S, 65°05′W) than in San José Gulf (45%) (40°32′S, 64°02′W); except for spring, when the two locations showed no differences in prevalences (80%). Independently of location, season and host size, infected geoducks showed lower condition index values than uninfected ones. Regarding other bivalve species, only one specimen of the razor clam Ensis macha was found infected, and none of the oysters Ostrea puelchana and Pododesmus rudis and scallop Aequipecten tehuelchus was parasitized by the green alga.     

Analysis of Late Jurassic to Early Cretaceous algal debris-facies of the Plassen carbonate platform in the Northern Calcareous Alps (Germany,Austria) and in the Kurbnesh area of the Mirdita zone (Albania): a tool to reconstruct tectonics and palaeogeography of eroded platforms

A characteristic microfacies of the Late Jurassic to Early Cretaceous allodapic Barmstein Limestone of the Northern Calcareous Alps are clasts of wackestones with numerous fragments of calcareous algae (“algal debris-facies”). According to dasycladale palaeocoenoses, several subtypes comprising different associations can be distinguished. One association is characterized by the debris of an unknown large dasycladalean alga reported as dasycladalean alga indet. sp. 1 from different localities in the Northern Calcareous Alps, typically forming a monospecific assemblage. Another microfacies type contains star-like calcitic bodies tentatively referred to the morphospecies Coptocampylodon pantici Ljubović-Obradović and Radoičić, originally described as being from the Turonian of NW-Serbia. Other Coptocampylodon-like bodies represent the calcified tufts of the laterals of Selliporella neocomiensis (Radoičić). The occurrence of Coptocampylodon pantici-like microfossils in the Late Tithonian to Early Berriasian, shows that obviously different species of dasycladaleans display identical to similar shaped tufts of laterals in transverse sections when becoming fragmented. Coptocampylodon pantici Ljubović-Obradović and Radoičić was observed only from different occurrences of Barmstein Limestone, but not from the autochthonous platform carbonates of the Plassen carbonate platform. The Coptocampylodon algal debris-facies is also reported from the Late Jurassic of Albania, Mirdita zone. Occurrences of different types of algal debris-facies in components of mass-flow deposits can be used as a tool to reconstruct eroded carbonate platforms and tectonics, as demonstrated in the Northern Calcareous Alps and the Albanides. Finally, the general occurrences of algal debris-facies in both settings—intra-Tethyan mostly isolated platforms (Alps, Albanides) vs. extended epeiric platforms (Middle East)—are compared and discussed.     

Feeding rates of common Antarctic gammarid amphipods on ecologically important sympatric macroalgae

Single species feeding trials employing both fresh algal tissues and alginate food pellets containing dried finely ground algal tissues were conducted to examine the relative palatability of sympatric Antarctic macroalgae (three brown and five red macroalgal species) to three common herbivorous gammarid amphipods (Prostebbingia gracilis Chevreux, Gondogeneia antarctica (Chevreux) Thurston, and Metaleptamphopus pectinatus Chevreux). In fresh algal tissue bioassays, both the amphipods P. gracilis and G. antarctica consumed significantly greater amounts of the red alga Palmaria decipiens over all other seven species of macroalgae. The amphipod M. pectinatus failed to consume measurable quantities of fresh thalli of any macroalgae and therefore is likely to feed on other resources. In food pellet bioassays, the consumption rates of amphipods fed with eight different species of macroalgae were compared with consumption rates on a highly palatable control green alga. Alginate pellets containing finely ground tissues of P. decipiens were consistently the most palatable of any of the macroalgae to P. gracilis and G. antarctica, while pellets containing the brown algae Desmarestia menziesii, D. anceps and the red alga Plocamium cartilagineum were not consumed by any of the three amphipod species. Regression analysis indicated that feeding rates of the amphipods P. gracilis and G. antarctica on alginate food pellets were not significantly correlated with known species-specific parameters of macroalgal nutritional quality (%N, %C, C:N ratio, soluble protein, soluble carbohydrate, and lipid). Therefore, differences in amphipod macroalgal palatability are most likely related to other factors including physical and/or chemical deterrents.     

Spatial associations among palatable and unpalatable macroalgae: A test of associational resistance with a herbivorous amphipod

Associational resistance is the process by which plants may gain protection from spatial associations with neighbouring plants. We tested whether association with an unpalatable alga, Dictyopteris acrostichoides, affects the abundance and colonisation behaviour of the herbivorous amphipod Peramphithoe parmerong on its preferred host alga Sargassum linearifolium. Despite predictions, natural densities on S. linearifolium when surrounded by D. acrostichoides were higher than on isolated individuals of S. linearifolium. Colonisation experiments in the laboratory and the field tested the hypotheses that the observed variation in field abundance with algal neighbourhood was due to variation in the size of habitat patches, physical obstruction of host finding by D. acrostichoides and variation in the relative abundance of S. linearifolium and D. acrostichoides. None of these possible mechanisms was found to significantly alter rates of amphipod colonisation on the scales of individuals selecting among algal pieces in the laboratory or among habitat patches in the field. The failure of colonisation processes to explain observed variation in natural amphipod densities suggests that post-colonisation processes such as survival or emigration may vary with the spatial associations among algae.     

Lageniastrum macrosporae (fossil Volvocales, Lageniastraceae nov. fam.), an endophyte in megaspores from the Carboniferous of the French Massif Central

Sublagenicula nuda lycophyte megaspores from the upper Visean of central France frequently host a colonial green alga as an endophyte. This association was first recorded more than 100 years ago by the French paleobotanist B. Renault, who introduced the name Lageniastrum macrosporae for the alga. However, the biological significance of the discovery was not fully assessed until recently. The L. macrosporae-S. nuda association represents the oldest compelling fossil evidence for algal endophytes in land plants, and the only example to date of an alga residing in the interior of spores of vascular cryptogams. Here we present a detailed re-evaluation and photographic documentation of the surviving original specimens from the Visean of Combres/Lay and Esnost. Moreover, a newly discovered specimen from the Stephanian of central France represents the first record of this association from the Upper Carboniferous. An emended diagnosis for L. macrosporae Renault, 1896 is provided, and a lectotype and paralectotype are designated. Although L. macrosporae displays a striking suite of morphological characters found in members of the extant chlorophyte family Volvocaceae (especially the genus Volvox), the peculiar biology of the fossil necessitates establishment of a new family, for which the name Lageniastraceae is proposed. Considerations of the adaptive advantages for the alga of occupying the interior of megaspores are offered. These include the possible effectiveness of the spores in protection during periods of desiccation and against plankton-feeding animals, and use of the spores as potential vectors for dispersal from one isolated body of water to another by spore-feeding animals.     

Organismal defenses versus environmentally mediated protection from herbivores: Unraveling the puzzling case of Desmarestia viridis (Phaeophyta)

The role of anti-herbivore organismal defenses in algae-herbivore interaction is frequently investigated without taking into account the potential role of environmental factors in mediating the interaction. Here we reexamine the interaction between the highly acidic, brown alga Desmarestia viridis and the green sea urchin, Strongylocentrotus droebachiensis, by incorporating a previously overlooked facet, the effect of changes in the wave environment on the ability of the urchin to establish contact with the alga. Factorial experiments in a wave tank (presence versus absence of waves; real versus mimic algae) showed that the aggregation of urchins on D. viridis was more than 2-fold greater in the absence than in the presence of waves. Similar numbers of urchins made contact with natural and mimic D. viridis plants, both with and without waves, indicating that any external release of chemicals (acid) from the alga had no perceptible repulsive effect on the urchin. The ability of the urchins to climb onto D. viridis increased markedly when urchin density attained a critical level. These results were consistent with field observations that urchins readily attack D. viridis under conditions of low wave action but do not under conditions of moderate wave action. We conclude (1) that the chemical makeup of D. viridis alone is neither necessary nor sufficient to limit contacts by the urchins and that (2) wave action is a major factor explaining the survival of D. viridis on urchin barrens, because waves limit the movements of the urchins towards the alga. We recommend that studies addressing marine algal defenses against herbivores be more comprehensive and examine interactions between algal traits, the physical environment, and the abundance and behavioral repertoire of herbivores.     

Evidence for a facultative mutualist nutritional relationship between the green coccoid alga Bracteacoccus sp. (Chlorophyceae) and the zoosporic fungus Rhizidium phycophilum (Chytridiomycota)

Symbiotic interactions between fungi and photosynthetic partners are common among derived fungal lineages. The only fungal-phototroph interactions thus far reported from the early diverging zoosporic fungi are parasitic in nature. Rhizidium phycophilum is a terrestrial, saprotrophic chytrid, which appears to be able to enter a facultative mutualism with a coccoid green alga in the absence of refractory organic material, such as pollen and chitin. Liquid and solid culturing methods were used in a series of differential fitness experiments in conjunction with microscopic analyses to characterize the interaction between R. phycophilum and the alga. The alga in this partnership is identified as a member of the genus Bracteacoccus. Under certain culturing conditions, algal cells grown in coculture with R. phycophilum were shown to grow larger and more prolifically than when cultured axenically under the same conditions. Additionally, dialysis experiments demonstrate that R. phycophilum does not parasitize Bracteacoccus sp., and can be cultured in media infused with unknown algal exudates. Rhizidium phycophilum and Bracteacoccus sp. represent the first facultative positive interaction between a zoosporic fungus and a photoautotroph and may prove a tractable system for modelling interactions between early fungi and plants.     

Trace-fossils and minor discontinuities in a marl limestone rhythmite, Lower-Middle Kimmeridgian, southern Spain

In a fine-grained Lower to Middle Kimmeridgian marly limestone rhythmite succession, with scarce benthos, fluctuations in ecological and depositional conditions that affected the substrate are detected by analysing trace-fossil assemblages. The dominant grey mudstones with Chondrites and Planolites superimposed on lumpy matrix sediments indicate both late colonisation of dysaerobic mixed layers and the completeness of the stratigraphic record. Major disruptions in rhythmic deposition and substrate colonisation are recorded at the base of thick intercalations of marls in sedimentary packages that were related to tectonic instability. Minor disruptions affected only the deposition of the overlying limestone beds. The trace-fossils reveal changes in the ecological and depositional conditions affecting the substrate during deposition of monotonous marly limestone rhythmites at levels of resolution higher than biostratigraphic, ecostratigraphic and taphonomic resolution. This research demonstrates the application of trace-fossil analysis to approach stratigraphic completeness (maturation) in homogeneous marly limestone rhythmites     

A new species of Isoperla (Insecta,Plecoptera) from the Karawanken,with considerations on the Southern Limestone Alps as centers of endemism

A new species of the genus Isoperla (Plecoptera, Perlodidae), belonging to the oxylepis species-group is described, and the male mating call is characterized. Its range falls within a small region of the Southern Limestone Alps which is well known to be one endemism-centre of aquatic insects.