Algal Crusts Research Articles

Comparación temporal de la composición y zonación de organismos en el intermareal rocoso del Parque Nacional Isla del Coco, Pacífico de Costa Rica

Several biological and physical factors change the rocky shore communities. The desiccation time and the tolerance of the intertidal species produce the vertical zonation. In many studies around the world, a temporal change in this zonation is presented.In Costa Rica, only studies that include temporal trends were carried out in Punta Mala and Montezuma, Pacific coast in 80's. The rocky intertidal of the Cocos Island National Park, Costa Rica were surveyed photographically. The Chatham bay was sampled in three expeditions (January 2007, October 2007 and April 2008). Photos corresponding to 25x25cm quadrats were taken with the goal to determine diversity and composition differences in rocky shore organisms between sampling dates. The Wafer bay was sampled in January and October 2007. The intertidal of Chatham consists of basaltic rock, while Wafer has basaltic and ignimbrite boulders. The main difference between sites were the higher algae cover (erect-frondose forms) and number of organism bands at Chatham bay. Temporal change was not found in the total cover of sessile fauna and autotrophs. The barnacle Tetraclita stalactifera, that occurs above the algal fringe (lower intertidal), was the invertebrate with the highest coverage. The mobile fauna biodiversity presented no significant trend between sampled months. However, the identity of species, their cover and their abundance showed a moderate temporal change. In October 2007, when the sea surface temperature was 23 degrees C the infralittoral zone had an increase in green algae cover. The red algae (crust and erect-frondose forms) were dominant in January and April. The pulmonate limpet, Siphonaria gigas and a bacterial biofilm at mid littoral showed a negative association. The snails of the high littoral and the supralittoral zone showed a temporal change in their abundance, but with contrasting patterns between sites. The temporal variation in the assemblages increased from the supralittoral to the infralittoral possibly due to changes in the water temperature and climatic conditions, that could influence the intertidal zone during the high and low tide, respectively.

Nematodes as an Indicator of Biological Crust Development in the Tengger Desert, China

Nematode communities were investigated on bare soil, physical soil crusts, algal crusts, and moss crusts in Shapotou in the Tengger Desert, China. The objective of the present study is to examine whether nematode communities develop parallel to the biological crust succession. The abundance of nematodes, the proportion of predators, maturity index, the number of nematode taxa identified, and Shannon index were affected significantly by crust type. Bare soil, physical soil crusts, algal crusts, and moss crusts were also comprised of differing community composition as indicated by PRC analysis. These results indicate that nematode communities develop parallel to crust development during the assisted revegetation of migrating sand dunes. Therefore, nematodes could be an indicator of biological crust development in the Tengger Desert, China.

Drowning history of a Miocene carbonate platform (Zhujiang Formation, South China Sea)

The identification and interpretation of drowning events in the geologic record can aid significantly to the reconstruction of the depositional, tectonic and eustatic history of a study area and often improve reservoir and seal prediction in carbonate rocks. The differentiation between drowned platforms showing a record of continuous deepening and those with a record of exposure followed by rapid deepening remains, however, problematic. The Zhujiang carbonate platform (Liuhua 11-1 field, South China Sea) study shown here provides an example of an integrated approach combining high-resolution geochemistry, microfacies analyses and foraminiferal biostratigraphy in order to improve the reconstruction of environmental conditions prior, during and after platform demise and drowning. The Zhujiang carbonate platform displays the following vertical succession of four facies types i) skeletal grain facies with a miogypsinid/lepidocyclinid-dominated fauna deposited in a moderately deep (< 50 m), oligotrophic back-reef setting; ii) in situ corals in patch-reef facies in an oligotrophic lagoon (< 10 m); iii) rhodoid facies with in situ red algal crusts, dominated by Heterostegina sp. and spiroclypeids, possibly capped by a subaerial exposure surface. Well-rounded rhodoids representing a mesotrophic lagoon dominate the upper portions of the rhodoid facies; iv) pelagic marine shales of the Hanjiang Formation burying the carbonate platform after drowning. This facies succession, in combination with geochemical evidence suggests a deepening-upward trend. This trend might have been interrupted by transient subaerial exposure but no evidence for meteoric diagenesis was found at the drowning unconformity topping the carbonate platform. Instead, microfacies analyses suggest that platform demise may be related to progressive changes in environmental conditions, including increasing nutrient-levels and/or decreasing temperature up-core towards the drowning unconformity. These findings are of significance for those concerned with Miocene carbonate factories and, more specifically, the demise of carbonate platforms in general.

The effect of biological soil crusts of different successional stages and conditions on the germination of seeds of three desert plants

Biological soil crusts greatly affect soil surface properties, which, in turn, may alter seed germination of vascular plants. We investigated the effects of two types of biological soil crusts (moss crust and algal crust) at different ages on the seed germination of Bassia dasyphylla and Artemisia ordosica. We also investigated the effects of crust conditions (living crust and dead crust) on seed germination of B. dasyphylla, A. ordosica and Eragrostis poaeoides. The presence of both algal and moss crusts significantly enhanced the germination of B. dasyphylla and A. ordosica compared with uncrusted soil. Crust age had no significant effect on the germination of either B. dasyphylla or A. ordosica for both moss and algal crusts. Germination of B. dasyphylla differed significantly between moss and algal crusts, but germination of both A. ordosica and E. poaeoides did not. Germination of A. ordosica, E. poaeoides and B. dasyphylla was significantly higher on living algal crust than on dead crust and uncrusted soil, while living moss crust enhanced the germination of both A. ordosica and B. dasyphylla but had no significant effect on E. poaeoides.

Limestones as a paleobathymeter for reconstructing past seismic activities: Muroto-misaki, Shikoku, southwestern Japan

Muroto-misaki (Cape Muroto) is located at the southern tip of the eastern half of Shikoku, southwestern Japan and is ~ 100 km north of the Nankai Trough where the Philippine Sea Plate is being subducted beneath the Eurasian Plate. Therefore, the Muroto-misaki area has been seismically uplifted. Sedimentologic analyses were conducted on Holocene limestones that occur along the coast from Muroto-misaki to Meoto-iwa, located ~ 13 km north of the cape. The limestones are limited to less than 9.2 m in elevation. The limestones are up to 4.4 m in mean diameter, up to 0.5 m in thickness, and consist mainly of fossilized sessile organisms, including annelids, corals, bryozoans, encrusting foraminifers, barnacles, nongeniculate coralline algae, and, to a lesser extent, molluscs and peyssonneliacean algae. Acicular and equant cements are minor components. Acicular cements are found in semi-closed spaces between coralline algal crusts and their substrates. The modal composition of limestones was determined by a point-counting technique. Based on the biotic composition, the Holocene limestones can be classified into six types (Types I to VI). A comparison of the vertical distribution of these rock types with that of modern sessile organisms indicates that the top of Type I limestone, which is characterized by the occurrence of hermatypic corals, corresponds approximately to the mean low water springs when the limestones formed. A difference in the highest occurrence of Type I limestone between two sites may represent the variation in the total amount of uplift over the last 1000 to 1500 years, which resulted in an apparent northward decline of paleo-mean low water springs at a rate of ~ 10 cm/km. Therefore, the Holocene limestones are a good paleobathymeter to reconstruct past seismic activities in this area. This study shows that warm temperate carbonate deposits are as excellent recorders of geologic events, such as the timing and scale of repeated coseismic uplifts and elevation of sea levels, as those in the tropics.

Control of Lunar and Martian Dust—Experimental Insights from Artificial and Natural Cyanobacterial and Algal Crusts in the Desert of Inner Mongolia, China

Studies on the colonization of environmentally extreme ground surfaces were conducted in a Mars-like desert area of Inner Mongolia, People's Republic of China, with microalgae and cyanobacteria. We collected and mass-cultured cyanobacterial strains from these regions and investigated their ability to form desert crusts artificially. These crusts had the capacity to resist sand wind erosion after just 15 days of growth. Similar to the surface of some Chinese deserts, the surface of Mars is characterized by a layer of fine dust, which will challenge future human exploration activities, particularly in confined spaces that will include greenhouses and habitats. We discuss the use of such crusts for the local control of desert sands in enclosed spaces on Mars. These experiments suggest innovative new directions in the applied use of microbe-mineral interactions to advance the human exploration and settlement of space.

Nature and biological composition of the New Caledonian outer barrier reef slopes

The Grande Terre of New Caledonia is enclosed by one of the longest barrier reefs in the world. For the first time, the fore-reef slopes of this barrier reef have been sampled by dredging, from 40 to 320 m deep, in order to analyze their sedimentological and biological characteristics. The rocks and sediments can be divided into seven sedimentary facies: bindstones dominated by coralline algal crusts, bindstones dominated by foraminiferal crusts, bindstones dominated by bryozoan crusts, coral framestones, bindstones and interstratified packstones rich in skeletal debris, packstones/wackestones and grainstones rich in rock gravels. Radiocarbon dating performed on encrusting organisms (coralline algae and acervulinids) and corals provide ages relatively young. These ages confirm that the encrusting organisms are modern and the corals mainly dated of Holocene are reworked due to the instability of the fore-reef slopes, especially during storms. Because the biological assemblages are distributed according to a bathymetric range depending on light intensity, a model of distribution of modern encrusting calcareous organisms can be proposed from our observations and analyses. From the upper reef slopes to approximately 90 m, thick coralline algal crusts are dominant and distributed in three groups. Group C, the shallowest parts of the fore slopes, is mainly characterized by mastophorids ( Hydrolithon reinboldii, H. cf. munitum, Lithoporella melobesoides, Aethesolithon cf. problematicum, Neogoniolithon sp. and undetermined species) and lithophylloids ( Lithophyllum sp., L. pustulatum). Group B, composed of lithophylloids ( Lithophyllum sp., L. cf. kotschyanum, L. cf. moluccence, L. pustulatum), Mesophyllum sp. and Peyssonnelia sp. occurs from 15 to 40 m. Group A, rich in Mesophyllum sp., M. cf. mesomorphum, Peyssonnelia sp. and Sporolithon sp. is characteristic of deep reef slopes up to 90 m. Below approximately 90 m, when the light intensity decreases, the encrusting foraminifera acervulinids progressively replace the coralline algal crusts. Such a model is particularly useful to interpret and reconstruct the past Quaternary reef environments rich in crusts of coralline algae and/or foraminifera.

Biological soil crust development and its topsoil properties in the process of dune stabilization, Inner Mongolia, China

This study was undertaken at Horqin Sand Land, Inner Mongolia, Northern China. Field samples of biological soil crusts (BSCs) and underlying topsoil (0–5 cm under BSC) were taken in areas of different dune stabilization stages, and their physicochemical properties were analyzed, including particle size distribution, bulk density, organic matter, nitrogen, phosphorus, electrical conductivity (EC), pH, and CaCO3 content. The results revealed that semi-mobile dunes, semi-fixed dunes and fixed dunes had developed a physical crust, algae crust and moss crust, respectively. The thickness, hardness, water content, fine fraction and nutrient contents of BSCs were gradually increasing along the dune stabilization gradient. Meanwhile, BSC establishment and development enhanced the bulk density, silt and clay content, and nutrients of the topsoil under it, in an increasing tend from semi-mobile dune to fixed dune. Organic matter concentrations and other nutrients in the 0–5 cm topsoil layer under BSCs were significantly higher compared to unconsolidated soil (control). Moreover, there were strong significant positive correlations between topsoil and BSCs’ organic matter, total nitrogen, available nitrogen, available phosphorus, CaCO3, and <0.05 mm particle content, suggesting that BSCs have an influence on some of the properties of the underlying topsoil.

Assessing the use of U–Th methods to determine the age of cold-water calcareous algae

Calcitic crusts of calcareous red algae could be suitable material for age determination of raised marine deposits and palaeothermometry at annual to sub-annual resolution. We examined the potential of U–Th dating of cold-water calcareous algae by analysing fossil specimens (n=10) from Kapp Ekholm (Svalbard) and recent specimens from Norway (n=3) and Scotland (n=1). After initial measurements using α-spectrometry, thermal ionisation mass spectrometry (TIMS) was used to study the material in more detail. Recent specimens contain 0.19–1.55μgg−1 U, and the measured (234U/238U) activity ratios vary between 1.12 and 1.30. Fossil specimens contain 1–168μgg−1 U, and display variable and highly elevated initial (234U/238U) activity ratios. In general, the TIMS results show increasing (234U/238U) activity ratios and concentrations of U and Th with increasing stratigraphic age. From this it is evident that marine calcareous red algae contain U in-vivo and they experience substantial post-mortem uptake of U. We conclude that direct U–Th dating of fossil calcareous algae from raised marine deposits is not viable without further geochemical understanding of the in-vivo uptake and post-depositional pathways of U and Th in such deposits. Despite the convincing open-system behaviour of the material, comparison with previously published chronostratigraphy from the site shows that the calcareous algae generally yield ages that are too old. This is in contrast to the expected result based on simple continuous post-mortem U accumulation and calls for a complex model comprising migration of U and multi-component addition of Th (detrital/colloidal) to explain the observed trends.

Effects of Biological Soil Crust on Desert Insect Diversity: Evidence from the Tengger Desert of Northern China

Biological soil crusts are widespread in arid and semiarid regions. They are one of the major components of desert ecosystems, and their importance has been demonstrated by numerous researchers. However, little research has been carried out on the relationship between biological soil crusts and the diversity of desert insects. In this study, psammophilous Caragana korshinskii-Artemisia ordosica communities occurring on semifixed dunes and fixed dunes in the Shapotou region at the southeastern fringe of the Tengger desert are investigated. Observation sample plots and the survey quadrats were arranged in the vegetation areas with different types and coverage of biological soil crusts. The insects were surveyed in 10 m × 10 m quadrats and caught by a sampling frame and net-trap methods. The insect number was recorded and samples were collected for identification. The results show that as compared to the un-crusted vegetation area, the presence of biological soil crusts in the Tengger desert significantly increases the diversity and abundance of insect species. Diversity and abundance in the quadrats mainly covered by moss and lichen crusts are significantly higher than those in the quadrats mainly covered by cyanobacteria and algal crusts. The contribution of biological soil crusts to the diversity of insect species may be attributed to the stabilized soil surface providing suitable habitats and some food sources for the insects.

Fluorescence responses of photosynthesis to extremes of hyposalinity, freezing and desiccation in the intertidal crust Hildenbrandia rubra (Hildenbrandiales, Rhodophyta)

K.Y. Kim and D.J. Garbary. 2006. Fluorescence responses of photosynthesis to extremes of hyposalinity, freezing and desiccation in the intertidal crust Hildenbrandia rubra (Hildenbrandiales, Rhodophyta). Phycologia 45: 680–686. DOI: 10.2216/05-43.1A winter collection of the intertidal, red algal crust, Hildenbrandia rubra (Sommerfelt) Meneghini, was examined for tolerance of photosynthesis to extremes of temperature, salinity and desiccation. Pulse amplitude modulation fluorometry of chlorophyll a fluorescence was used to determine various photosynthetic parameters including effective quantum yield (ΦPSII) and relative electron transport rate (rETR). Thalli from the same collection were successively exposed to freezing, desiccation, hyposalinity and high temperature. Thus thalli over 13 days experienced temperature fluctuations from −17 to 27°C, from fully hydrated to extremely desiccated, from full seawater to 4 psu and back, all without any apparent long-term effects to the photosynthetic apparatus. There was no significant difference in ΦPSII between thalli at the beginning and end of the experiments. Algae showed a significant acclimation to low light in that immediately after collection thalli had optimum light intensity, Ik, in terms of rETR at 50 μmol photons m−2 s−1, whereas 24 h later maximal rETR was at about 20 μmol photons m−2 s−1. Hildenbrandia rubra is the most physiologically tolerant of any tested seaweed, and this helps explain its wide geographic and ecological range.

Relationships between the biomass of algal crusts in fields and their compressive strength

In the desert areas of China investigated by the authors, various biological crusts were predominately associated with three blue-green algal (cyanobacterial) species, Microcoleus vaginatus Gom., Phormidium tenue (Menegh.) Gom. and Scytonema javanicum (Kütz.) Born et Flah. Their biomass and their compressive strength were measured simultaneously in the field in this study. It was also found that the compressive strength of algal crusts was enhanced with the increasing of algal biomass from an undetectable level to a value as high as 9.6 mg g −1 dry soil. However, when the algal biomass decreased, the compressive strength did not descend immediately, but remained relatively steady. The higher the algal biomass became, the thicker were the algal crusts formed. Given the same biomass, the highest compressive strength of man-made algal crusts in fields was found at an algal ratio of 62.5% M. vaginatus, 31.25% P. tenue and 6.25% S. javanicum, and it reached 0.89 kg cm −2. When the biomass of the crusts increased above the value of 8.16 mg chl a g −1 dry soil, the compressive strength would not ascend easily. It indicated that the compressive strength of man-made algal crusts appeared temporarily saturated in the field.

Effects of biological soil crusts on emergence of desert vascular plants in North China

Biological soil crusts are a universal and common feature in arid and semi-arid regions and their appearance profoundly affects soil surface properties which may greatly change the seed dispersal, germination and establishment. To date, only a handful of experiments have exerted to investigate the effects of crusts on vascular plants and the conclusions from these studies are variable. In this study, we investigate the influences of two different crusts universally spreading in southeastern part of the Tengger Desert with four chronosequences (24, 41, 50 years old in artificial vegetation area and natural vegetation crusts) on vascular plants. Crusts were placed at three different sites to simulate different environmental factors (wind velocity and soil crust moisture), we set two soil moisture regimes for crusts to investigate how vascular plants respond under different moisture regimes in crusts. Emergence densities of vascular plants were significantly higher in moss crust than in algae crust. With the development of crusts, seed emergence increased in moss crust while decreased in algae crust. As for effects of moisture, our results showed that soil moisture had a significant effect on seed emergence in both types of crusts at all developing phases. Crusts with higher moisture had more seedlings than those with lower moisture. The above results indicated that the appearance of crusts changed the surface soil properties, which had greatly influenced the entrapment and lodgement of seeds in the study area, thus subsequently influence seed emergence through affecting natural factors.

Effects of Salt Stress on Carbohydrate Metabolism in Desert Soil Alga Microcoleus vaginatus Gom.

AbstractThe effects of salt stress on carbohydrate metabolism in Microcoleus vaginatus Gom., a cyanobacterium isolated from desert algal crusts, were investigated in the present study. Extracellular total carbohydrates and exopolysaccharides (EPS) in the culture medium produced by M. vaginatus increased significantly during the growth phase and reached a maximum during the stationary phase. The production of extracellular carbohydrates also significantly increased under higher salt concentrations, which was attributed to an increase in low molecular weight carbohydrates. In the presence of NaCl, the production of cellular total carbohydrates decreased and photosynthetic activity was impaired, whereas cellular reducing sugars, water‐soluble sugars and sucrose content and sucrose phosphate synthase activity increased, reaching a maximum in the presence of 200 mmol/L NaCl. These parameters were restored to original levels when the algae were transferred to a non‐saline medium. Sodium and K+ concentrations of stressed cells decreased significantly and H+‐ATPase activity increased after the addition of exogenous sucrose or EPS. The results suggest that EPS and sucrose are synthesized to maintain the cellular osmotic equilibrium between the intra‐ and extracellular environment, thus protecting algal cells from osmotic damage, which was attributed to the selective exclusion of cellular Na+ and K+ by H+‐ATPase.(Managing editor: Ping He)

Man-made desert algal crusts as affected by environmental factors in Inner Mongolia, China

Man-made desert algal crusts were constructed on a large scale (3000 m 2) in Inner Mongolia, China. Microcoleus vaginatus was mass cultivated and inoculated directly onto unconsolidated sand dune and irrigated by automatic sprinkling micro-irrigation facilities. The crusts were formed in a short time and could resist the erosion of winds and rainfalls 22 days after inoculation. The maximum biomass in the man-made algal crusts could also reach 35 μg Chl a/cm 2 of soil. Effects of environmental factors such as temperature, irrigation, rainfall and soil nutrients on algal biomass of man-made algal crusts were also studied. It was found that rainfalls and lower light intensity had significantly positive effects on the biomass of man-made algal crusts. The preliminary results suggested that man-made algal crusts could be formed rapidly, and thus it might be a new feasible alternative method for fixing unconsolidated sand.

Larger foraminiferal and coralline algal facies in an Upper Eocene storm-influenced, shallow-water carbonate platform (Colli Berici, north-eastern Italy)

Facies analysis of Priabonian shallow-water carbonate successions in the outcrops near Mossano (eastern Colli Berici, north-eastern Italy) and the subsequent integration of palaeoecological data have been used to produce a detailed palaeoenvironmental model. The facies distribution and the processes, which controlled the larger benthic foraminiferal and coralline algal assemblages in the study Priabonian storm-influenced, carbonate ramp, are discussed in detail. In the middle-ramp trough, cross-bedded small Nummulites and rhodolith packstones pass laterally into coralline algal crust wackestones. These rhodoliths exhibit two well-differentiated growth-phases: the first occurring during low-water energy periods, followed by a second developed during high-energy events during which they were reworked and partially destroyed. These facies pass laterally into orthophragminid rudstones and packstones characterised by orthophragminid tests and channel structures. The latter were formed by storm-induced return currents, which swept the middle-ramp creating distal middle-ramp channel structures. Further toward the distal part of the middle-ramp the return currents decreased in energy and discharged nutrients allowing the coralline crustose pavement to develop. This is characterised by rhodoliths typically discoidal in shape (up to 10 cm in diameter) with a loose inner arrangement consisting of encrusting-to-foliose growth-forms. The occurrence of the channel structures in orthophragminid rudstones and in the coralline crustose pavement appears to be unique in Upper Eocene carbonate ramp depositional systems. During the erosive events associated with the return currents, these shallow-water carbonates were unlithified or only weakly lithified and were, therefore, easily transported into deeper water ramp settings. The model suggests that the significant changes of the middle-ramp benthic communities with depth could have formed, at least in part, by offshore return currents, which played an important role in both controlling substrates and in supplying nutrients.

Ecological and environmental explanation of microbiotic crusts on sand dune scales in the Gurbantonggut Desert, Xinjiang

Abstract Results obtained from the field investigation and the analysis in laboratory show that many species of microbiotic crusts of lichens, mosses and algae develop extensively in the Gurbantonggut Desert, Xinjiang. The formation, species and distribution are closely related to the environmental conditions at the different positions of sand dunes. The animalcule crusts develop mainly on the mobile or semi-mobile sand surface of dune tops, the alga crusts develop mainly at the upper to middle parts of dune slopes, the lichen crusts develop at middle and lower parts of dune slopes, and the moss crusts are mainly distributed at the lower part of dune slopes and the interdune low-lands. The species, thickness and developing degree of microbiotic crusts increase from the upper part to the middle and lower parts of dune slopes and the interdune lowlands, and an obvious contrast between the microbiotic crusts and the different species of plant communities forms. The development and differentiation of microbio...

Primary production potential of non-geniculate coralline algae at Cape Evans, Ross Sea, Antarctica

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 294:131-140 (2005) - doi:10.3354/meps294131 Primary production potential of non-geniculate coralline algae at Cape Evans, Ross Sea, Antarctica Anne-Maree Schwarz1,3,*, Ian Hawes1,3, Neil Andrew2,4, Steve Mercer2,Vonda Cummings2, Simon Thrush1 1National Institute of Water and Atmospheric Research, PO Box 11-115, Hamilton, New Zealand2National Institute of Water and Atmospheric Research, PO Box 14-901, Wellington, New Zealand3Present address: The Worldfish Center, PO Box 77, Gizo, Solomon Islands4Present address: The Worldfish Center, PO Box 500 GPO 10670, Penang, Malaysia *Email: a.schwarz@cgiar.org ABSTRACT: The abundance and photosynthetic characteristics of non-geniculate coralline algae were determined at Cape Evans, McMurdo Sound (Ross Sea), Antarctica, during spring 2003. At the time, the site was covered by 2.5 m of sea-ice through which only 0.48% of incident irradiance was able to penetrate. Coralline algae covered 4 to 60% of the seafloor from water depths of 13 to 26 m. Coralline algal crusts showed light-saturated rates of photosynthesis from 9.4 to 20 mmol O2 m–2 thallus d–1 and dark respiration rates from 0.15 to 0.96 mmol O2 m–2 thallus d–1. The average irradiance at which the onset of light saturated photosynthesis occurred (Ek) was 3.2 µmol photons m–2 s–1, measured using oxygen micro-electrodes, and 2.9 µmol photons m–2 s–1, measured using pulse amplitude modulated (PAM) fluorometry techniques. Irradiance at depths of 15 to 20 m did not exceed 2 µmol photons m–2 s–1 during the study, but frequently exceeded the light compensation point for photosynthesis (Ec), estimated as 0.10 µmol photons m–2 s–1. The effective quantum yield (ΔF/Fm’) of Photosystem II, measured in situ over diel periods at depths of 16, 18 and 20 m, averaged 0.691 (SD = 0.003), 0.639 (SD = 0.005) and 0.632 (SD = 0.007), respectively. These values were indicative of minimal down-regulation of photosynthesis, and were consistent with the observation that irradiance never exceeded Ek. Laboratory investigations, showed that on transfer from ambient irradiance to 23.5 µmol photons m–2 s–1, a change of 2 orders of magnitude, the algae showed minimal photoinhibition and a small, but statistically significant increase in Ek and maximum electron transport rate. Coralline algae at Cape Evans are able to persist with net carbon accrual under ice, while being able to tolerate periods of higher irradiance during ice-free conditions. This contrasts to Phyllophora antarctica which is dependent on ice-free periods to achieve net production. KEY WORDS: Photosynthesis · Oxygen electrodes · Macroalgae · Phyllophora antarctica · Photoacclimation · Mesophyllum engelhartii · Synarthrophyton patena Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 294. Online publication date: June 09, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.

Seasonal synchrony of a green algal endophyte, Acrosiphonia (Codiolales), with its red algal hosts, Mastocarpus and Mazzaella (Gigartinales)

A.V. Sussmann, R. Scrosati and R.E. DeWreede. 2005. Seasonal synchrony of a green algal endophyte, Acrosiphonia (Codiolales), with its red algal hosts, Mastocarpus and Mazzaella (Gigartinales). Phycologia 44: 129–132.‘Codiolum’ and ‘chlorochytrium’ (both unicellular sporophyte phases of the filamentous green alga Acrosiphonia) are endophytic in the red algal crust ‘petrocelis’ (sporophyte of Mastocarpus papillatus) and in the bladed red alga Mazzaella splendens, respectively, in southern British Columbia, Canada. This study is the first to investigate experimentally the synchrony of host and endophyte seasonal abundance for any host–endophyte system. A correlation study of time series data on abundance indicated that in 1997 and 1998 seasonal synchrony occurred for both host–endophyte associations; this was predicted for interactions where the host is highly seasonal and the host–endophyte relationship is highly specific. We suggest that Acrosiphonia's sporophyte phase may have evolved to synchronize colonization with increasing host abundance, and synchronize reproductive phenology and host exit (as zoospores) with decreasing host abundance.

Crustose algal frameworks from the Eocene Alpine Foreland

Upper Eocene algal limestones of the Eastern Alpine Foreland in Austria contain three different types of crustose algal frameworks. These reveal several similarities with the present-day coralligene de plateau of the Mediterranean Sea, but the framework types differ in the crust-forming algal taxa, the sedimentary regime, and the environmental setting. (1) The coralline-coral frameworks develop from siliciclastic sediments and show a succession from coverstones to bindstone to cruststone. Initiation of this framework in a siliciclastic regime is only possible because of the occurrence of Neogoniolithon sp., a species that is able to grow on fine-grained soft substrate. The onset of a dense crustose framework was related to the reduced sediment input and the occurrence of Lithothamnion sp., which is able to form cruststones. (2) Pure coralline algal frameworks are restricted to cruststones dominated by both Lithothamnion sp. and Neogoniolithon sp. They formed on top of maerl megaripples during calm periods and shed crustose fragments towards depressions, which allowed framework progradation. (3) Peyssonneliacean dominated frameworks occur with intercalations of coralline algal crusts. They formed in muddy environments interpreted as protected depressions between maerl dunes. We found that crustose frameworks are controlled by three factors: (1) Sediment input. Low input favors the growth of frameworks, while coarser grained siliciclastics cause burial of initial algal crusts. Terrigenous mud influences water turbidity and thus favors the occurrence of peyssonneliacean algae. (2) Taxonomic composition. Framework formation requires the existence of crustose algal taxa, which are able to grow directly on fine-grained soft substrate ( Neogoniolithon sp., Polystrata alba), or to encrust and stabilize coarse-grained particles ( Lithothamnion sp.), and/or to form multiple successions of dense crusts ( Lithothamnion sp., P. alba). Phymatolithon sp. characteristically encrusts corals, but it does not contribute to the frameworks. Surprisingly, algae do never form protuberances within the frameworks, even if they show protuberant growth forms in maerl sediment. (3) Substrate stability as a function of substrate composition and hydrodynamic energy. Due to their occurrence on maerl bottoms and the lack of evidence for submarine hardgrounds, the settlement of crustose buildups requires low tidal current activity and/or wave agitation.