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Y M Chamberlain - One of the best experts on this subject based on the ideXlab platform.

D W Keats - One of the best experts on this subject based on the ideXlab platform.

  • effects of herbivore grazing on the physiognomy of the Coralline Alga spongites yendoi and on associated competitive interactions
    African Journal of Marine Science, 2008
    Co-Authors: Gavin W Maneveldt, D W Keats
    Abstract:

    The territorial gardening limpet Scutellastra cochlear occurs along the south and southern west coasts of South Africa, whereas one of its primary food items, the encrusting Coralline Alga Spongites yendoi , extends much farther north along the West Coast. A combined analysis of geographic variation in limpet grazing frequency and a limpet-manipulation experiment was used to study the interaction between the limpet and its Coralline food. The Coralline comprised most (c. 85%) of the limpet\'s diet whereas fleshy Algae from the limpet\'s garden comprised c. 7%. Grazing caused the thallus of the Coralline to be thin and smooth; in the absence of herbivory, or under low grazing frequencies, the crust became thick and highly protuberant. Grazing weakened the Coralline\'s interference (overgrowth) competitive ability and also reduced its fecundity. In spite of these two apparently negative impacts, the intimate herbivore–Coralline association between S. cochlear and S. yendoi showed characteristics of a facultative mutualism. Grazing by S. cochlear reduces the Coralline\'s thallus thickness and consequently increased its lateral margin extension rate. Thinner forms of the Coralline grew five times faster than thicker forms. An increased lateral growth results in the thinner form of the Coralline being very abundant on the south and southern west coasts, occupying as much as 79% of the substratum in the lower eulittoral zone. Thinner forms of S. yendoi were also less burrowed by boring organisms and more strongly attached than thicker forms of the Coralline. Grazing by S. cochlear has thus conferred the advantages of faster lateral growth (i.e. success at exploitation competition) and stronger attachment. The Coralline and fleshy Algae from the limpet\'s garden were equally high in organic content on a volume basis. This suggests that the crude food value per bite in the Coralline and fleshy Algae is comparable. This study has shown that incompletely overlapping distributions between strongly interacting species along a broad geographical gradient is not just a significant feature of the ecology of terrestrial, but also of marine ecosystems. Keywords: competition; Coralline; fecundity; growth; herbivory; morphology; Scutellastra cochlear; Spongites yendoi African Journal of Marine Science 2008, 30(3): 581–593

  • fine structure of deep layer sloughing and epithallial regeneration in lithophyllum neoatalayense corallinales rhodophyta
    Phycological Research, 1997
    Co-Authors: Curt M Pueschel, D W Keats
    Abstract:

    SUMMARY Transmission electron microscopic study of Lithophyllum neoatalayense Masaki demonstrated that this Alga used two mechanisms by which it sloughed cells from its surface. Epithallial filaments, produced by a layer of underlying initial cells, were two to four cells long. Terminal epithallial cells, those closest to the thallus surface, underwent senescence and shedding as previously described for other Coralline Algae. In addition, deep-layer sloughing occurred. During this process, which is known for only one other Coralline Alga, cell death occurred uniformly within a surface layer 40-50 μm thick. No pathogens or evidence of mechanical damage was detected. The zone of dead cells included the epithallial layer, the layer of initial cells, and some cortex cells beneath the initials. Pit plugs connecting living and dead cells at the edge of the necrotic zone were sealed by wall material deposited by the surviving cells, but cells within the necrotic zone showed no evidence of sealed pit plugs. The outermost surviving cells became new initial cells, which then divided to form new epithallial cells. Regeneration of the epithallial layer occurred before the thick layer of dead cells peeled away. The extensive deep shedding of both epithallial and initial cells in L. neoatalayense and the effectiveness of regeneration from cortex cells challenge the assumption that protection of initial cells is an important function of epithallial cells.

  • lithothamnion prolifer foslie a common non geniculate Coralline Alga rhodophyta corallinaceae from the tropical and subtropical indo pacific
    Botanica Marina, 1996
    Co-Authors: D W Keats, Robert S Steneck, R A Townsend, Michael A Borowitzka
    Abstract:

    A little-known, but ecologically important non-geniculate Coralline, LitIhothamnion prolifer, is recorded from a number of tropical Indo-Pacific sites, including Fiji, Australia, Kiribati and Indonesia. The species occurs primarily on vertical walls of caves and overhangs in Fiji and Australia, but was also found as rhodoliths in Kiribati. LitIhothamnion prolifer is characterized by the combination of characters which follow. The thallus is extremely glossy, smooth, and rosy coloured. Thalli usually produce complanate protuberances, but protuberances become terete when growing on well lit, horizontal substrata, when unattached, or when growing on loose substrata. Conceptacles occur mainly on the tips of protuberances, and tetra/bisporangial conceptacles are large (to 1300 µm external diameter, with chambers up to 1100 µm diameter). The tetra/bisporangial conceptacles are flush or only slightly raised, and often extensive and irregularly shaped (resembling small son). They lack a raised rim, and have flattened pore plates. The rosette cells surrounding the tetra/bisporang ial pore appear somewhat sunken below the surrounding roof cells in SEM, and the cells of filaments lining the pore canals of let tetra/bisporangial conceptacles do not differ from the cells of filaments making up the rest of the roof. Old conceptacles persist and become buried in the thallus, and are then usually completely filled in by irregularly arranged calcified cells.

  • 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
    Phycological Research, 1995
    Co-Authors: D W Keats
    Abstract:

    SUMMARY 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.

  • heydrichia groeneri sp nov a new species of crustose Coralline Alga rhodophyta sporolithaceae from south africa and namibia
    Phycologia, 1995
    Co-Authors: D W Keats, Y M Chamberlain
    Abstract:

    Heydrichia groeneri sp. nov., the second recorded species of the genus, is described from western Cape Province, South Africa, and southern Namibia. It is ascribed to the genus Heydrichia on the ba...

Federica Ragazzola - One of the best experts on this subject based on the ideXlab platform.

  • an intertidal life combined effects of acidification and winter heatwaves on a Coralline Alga ellisolandia elongata and its associated invertebrate community
    Marine Environmental Research, 2021
    Co-Authors: Federica Ragazzola, Regina Kolzenburg, Agnese Marchini, Mario Adani, Andrea Bordone, Alberto Castelli, Gabriella Cerrati, Joachim Langeneck, Carlotta Di Marzo
    Abstract:

    Abstract In coastal marine ecosystems Coralline Algae often create biogenic reefs. These calcareous Algal reefs affect their associated invertebrate communities via diurnal oscillations in photosynthesis, respiration and calcification processes. Little is known about how these biogenic reefs function and how they will be affected by climate change. We investigated the winter response of a Mediterranean intertidal biogenic reef, Ellissolandia elongata exposed in the laboratory to reduced pH conditions (i.e. ambient pH – 0.3, RCP 8.5) together with an extreme heatwave event (+1.4 °C for 15 days). Response variables considered both the Algal physiology (calcification and photosynthetic rates) and community structure of the associated invertebrates (at taxonomic and functional level). The combination of a reduced pH with a heatwave event caused Ellisolandia elongata to significantly increase photosynthetic activity. The high variability of calcification that occurred during simulated night time conditions, indicates that there is not a simple, linear relationship between these two and may indicate that it will be resilient to future conditions of climate change. In contrast, the associated fauna were particularly negatively affected by the heatwave event, which impoverished the communities as opportunistic taxa became dominant. Local increases in oxygen and pH driven by the Algae can buffer the microhabitat in the Algal fronds, thus favouring the survival of small invertebrates.

  • physiological response of the Coralline Alga corallina officinalis l to both predicted long term increases in temperature and short term heatwave events
    Marine Environmental Research, 2019
    Co-Authors: Francesco Rendina, Phil J Bouchet, Luca Appolloni, Giovanni Fulvio Russo, Roberto Sandulli, Regina Kolzenburg, Aditya Putra, Federica Ragazzola
    Abstract:

    Abstract Climate change is leading to an increase of mean sea surface temperatures and extreme heat events. There is an urgent need to better understand the capabilities of marine macroAlgae to adapt to these rapid changes. In this study, the responses of photosynthesis, respiration, and calcification to elevated temperature in a global warming scenario were investigated in the Coralline Alga Corallina officinalis. Algae were cultured for 7 weeks under 4 temperature treatments: (1) control under ambient-summer conditions (C, ~20 °C), (2) simulating a one-week heatwave of 1 °C (HW, Tcontrol+1 °C), (3) elevated temperature (+3, Tcontrol +3 °C), (4) combination of the two previous treatments (HW+3, T+3+1 °C). After exposure at T+3 (up to a Tmax of ~23 °C), respiration and photosynthesis increased significantly. After 5 weeks, calcification rates were higher at elevated temperatures (T+3 and THW+3) compared to Tcontrol, but at the end of the experiment (7 weeks) calcification decreased significantly at those temperatures beyond the thermal optimum (six-fold at T+3, and three-fold at THW+3, respectively). The same trend was noted for all the physiological processes, suggesting that a prolonged exposure to high temperatures (7 weeks up to T+3) negatively affect the physiology of C. officinalis, as a possible consequence of thermal stress. A one-week heatwave of +1 °C with respect to Tcontrol (at THW) did not affect respiration, photosynthesis, or calcification rates. Conversely, a heatwave of 1 °C, when combined with the 3 °C increase predicted by the end of the century (at THW+3), induced a reduction of physiological rates. Continued increases in both the intensity and frequency of heatwaves under anthropogenic climate change may lead to reduced growth and survival of primary producers such as C. officinalis.

  • Elemental variability in the Coralline Alga Lithophyllum yemenense as an archive of past climate in the Gulf of Aden (NW Indian Ocean)
    Journal of Phycology, 2017
    Co-Authors: Annalisa Caragnano, Daniela Basso, David Storz, Dorrit E. Jacob, Federica Ragazzola, Francesca Benzoni, Eric Dutrieux
    Abstract:

    This study presents the first Algal thallus (skeleton) archive of Asian monsoon strength and Red Sea influence in the Gulf of Aden. Mg/Ca, Li/Ca, and Ba/Ca were measured in Lithophyllum yemenense from Balhaf (Gulf of Aden) using laser ablation inductively coupled plasma mass spectrometry, and Mg/Ca ratio oscillation was used to reconstruct the chronology (34 y). Oscillations of element rates corresponding to the Algal growth between 1974 and 2008 were compared with recorded climate and oceanographic variability. During this period, sea surface temperatures (SST) in Balhaf recorded a warming trend of 0.55°C, corresponding to an increase in Mg and Li content in the Algal thallus of 2.1 mol-% and 1.87 μmol-%, respectively. Lithophyllum yemenense recorded decadal SST variability by Li/Ca, and the influence of the Pacific El-Nino Southern Oscillation on the NW Indian Ocean climate system by Ba/Ca. Additionally, Algal Mg/Ca, Li/Ca, and Ba/Ca showed strong and significant correlations with All Indian Rainfall in the decadal range indicating that these proxies can be useful for tracking variability in the Indian monsoon system, possibly due to changes of the surface wind system, with deep water upwelling in summer, and a distinct seasonality.

A Groener - One of the best experts on this subject based on the ideXlab platform.

Sophie Martin - One of the best experts on this subject based on the ideXlab platform.

  • Mineralogical response of the Mediterranean crustose Coralline Alga Lithophyllum cabiochae to near-future ocean acidification and warming
    Biogeosciences, 2016
    Co-Authors: M. C. Nash, Sophie Martin, Jean-pierre Gattuso
    Abstract:

    Abstract. Red calcareous Coralline Algae are thought to be among the organisms most vulnerable to ocean acidification due to the high solubility of their magnesium calcite skeleton. Although skeletal mineralogy is proposed to change as CO2 and temperature continue to rise, there is currently very little information available on the response of Coralline Algal carbonate mineralogy to near-future changes in pCO2 and temperature. Here we present results from a 1-year controlled laboratory experiment to test mineralogical responses to pCO2 and temperature in the Mediterranean crustose Coralline Alga (CCA) Lithophyllum cabiochae. Our results show that Mg incorporation is mainly constrained by temperature (+1 mol % MgCO3 for an increase of 3 °C), and there was no response to pCO2. This suggests that L. cabiochae thalli have the ability to buffer their calcifying medium against ocean acidification, thereby enabling them to continue to deposit magnesium calcite with a significant mol % MgCO3 under elevated pCO2. Analyses of CCA dissolution chips showed a decrease in Mg content after 1 year for all treatments, but this was affected neither by pCO2 nor by temperature. Our findings suggest that biological processes exert a strong control on calcification on magnesium calcite and that CCA may be more resilient under rising CO2 than previously thought. However, previously demonstrated increased skeletal dissolution with ocean acidification will still have major consequences for the stability and maintenance of Mediterranean coralligenous habitats.

  • physiological responses of three temperate Coralline Algae from contrasting habitats to near future ocean acidification
    Journal of Experimental Marine Biology and Ecology, 2013
    Co-Authors: Fanny Noisette, Hronn Egilsdottir, Dominique Davoult, Sophie Martin
    Abstract:

    Coralline Algae are major calcifiers of significant ecological importance in marine habitats but are among the most sensitive calcifying organisms to ocean acidification. The elevated pCO2 effects were examined in three Coralline Algal species living in contrasting habitats from intertidal to subtidal zones on the north-western coast of Brittany, France: (i) Corallina elongata, a branched Alga found in tidal rock pools, (ii) Lithophyllum incrustans, a crustose Coralline Alga from the low intertidal zone, and (iii) Lithothamnion corallioides (maerl), a free-living form inhabiting the subtidal zone. Metabolic rates were assessed on specimens grown for one month at varying pCO2: 380 (current pCO2), 550, 750 and 1000 μatm (elevated pCO2). There was no pCO2 effect on gross production in C. elongata and L. incrustans but L. incrustans respiration strongly increased with elevated pCO2. L. corallioides gross production slightly increased at 1000 μatm, while respiration remained unaffected. Calcification rates decreased with pCO2 in L. incrustans (both in the light and dark) and L. corallioides (only in the light), while C. elongata calcification was unaffected. This was consistent with the lower skeletal mMg/Ca ratio of C. elongata (0.17) relative to the two other species (0.20). L. incrustans had a higher occurrence of bleaching that increased with increasing pCO2. pCO2 could indirectly impact this Coralline species physiology making them more sensitive to other stresses such as diseases or pathogens. These results underlined that the physiological response of Coralline Algae to near-future ocean acidification is species-specific and that species experiencing naturally strong pH variations were not necessarily more resistant to elevated pCO2 than species from more stable environment.

  • One-year experiment on the physiological response of the Mediterranean crustose Coralline Alga, Lithophyllum cabiochae, to elevated pCO2 and temperature
    Ecology and Evolution, 2013
    Co-Authors: Sophie Martin, S. Cohu, Céline Vignot, Guillaume Zimmerman, Jean-pierre Gattuso
    Abstract:

    The response of respiration, photosynthesis, and calcification to elevated pCO2 and temperature was investigated in isolation and in combination in the Mediterranean crustose Coralline Alga Lithophyllum cabiochae. Algae were maintained in aquaria during 1 year at near-ambient conditions of irradiance, at ambient or elevated temperature (+3°C), and at ambient (ca. 400 μatm) or elevated pCO2 (ca. 700 μatm). Respiration, photosynthesis, and net calcification showed a strong seasonal pattern following the seasonal variations of temperature and irradiance, with higher rates in summer than in winter. Respiration was unaffected by pCO2 but showed a general trend of increase at elevated temperature at all seasons, except in summer under elevated pCO2. Conversely, photosynthesis was strongly affected by pCO2 with a decline under elevated pCO2 in summer, autumn, and winter. In particular, photosynthetic efficiency was reduced under elevated pCO2. Net calcification showed different responses depending on the season. In summer, net calcification increased with rising temperature under ambient pCO2 but decreased with rising temperature under elevated pCO2. Surprisingly, the highest rates in summer were found under elevated pCO2 and ambient temperature. In autumn, winter, and spring, net calcification exhibited a positive or no response at elevated temperature but was unaffected by pCO2. The rate of calcification of L. cabiochae was thus maintained or even enhanced under increased pCO2. However, there is likely a trade-off with other physiological processes. For example, photosynthesis declines in response to increased pCO2 under ambient irradiance. The present study reports only on the physiological response of healthy specimens to ocean warming and acidification, however, these environmental changes may affect the vulnerability of Coralline Algae to other stresses such as pathogens and necroses that can cause major dissolution, which would have critical consequence for the sustainability of coralligenous habitats and the budgets of carbon and calcium carbonate in coastal Mediterranean ecosystems.

  • Photosynthesis, respiration and calcification in the Mediterranean crustose Coralline Alga Lithophyllum cabiochae (Corallinales, Rhodophyta)
    European Journal of Phycology, 2013
    Co-Authors: Sophie Martin, Amelie Charnoz, Jean-pierre Gattuso
    Abstract:

    Primary production and calcification responses to irradiance were investigated in Lithophyllum cabiochae, a crustose Coralline Alga from Mediterranean coralligenous communities, collected at c. 25m depth in the Bay of Villefranche. Algae were maintained in aquaria at temperature and irradiance levels close to in situ conditions. Physiological measurements were performed using incubation chambers in the dark and in the light at different irradiance levels within the range of those measured in situ. Both photosynthesis and calcification rates in L. cabiochae were strongly related to irradiance. Dark respiration averaged 0.20.3 mu molcm(2) thallus h(1) in terms of both O-2 consumption and CO2 release and maximal gross photosynthesis averaged 1.0 mu molcm(2) h(1) in terms of both O-2 production and CO2 uptake. Mean rate of net calcification was 0.1 mu mol CaCO3 cm(2) h(1) in the dark and reached 0.4 mu mol CaCO3 cm(2) h(1) in the light. Diel net and gross organic C productions were estimated to be 3 and 7 mu molC cm(2) thallus d(1,) respectively. Diel net inorganic C production was estimated to be 3 mu mol CaCO3 cm(2) thallus d(1). Despite the low light conditions experienced by the Algae at c. 25m depth, L. cabiochae can be considered as a major contributor to primary productivity and calcium carbonate deposition, making coralligenous communities a major carbon and carbonate producer in the Mediterranean Sea.

  • Effects of pCO(2) on physiology and skeletal mineralogy in a tidal pool Coralline Alga Corallina elongata
    Marine Biology, 2013
    Co-Authors: Hronn Egilsdottir, Jon Olafsson, Fanny Noisette, Laure M-l J. Noël, Sophie Martin
    Abstract:

    Marine organisms inhabiting environments where pCO(2)/pH varies naturally are suggested to be relatively resilient to future ocean acidification. To test this hypothesis, the effect of elevated pCO(2) was investigated in the articulated Coralline red Alga Corallina elongata from an intertidal rock pool on the north coast of Brittany (France), where pCO(2) naturally varied daily between 70 and 1000 mu atm. Metabolism was measured on Algae in the laboratory after they had been grown for 3 weeks at pCO(2) concentrations of 380, 550, 750 and 1000 mu atm. Net and gross primary production, respiration and calcification rates were assessed by measurements of oxygen and total alkalinity fluxes using incubation chambers in the light and dark. Calcite mol % Mg/Ca (mMg/Ca) was analysed in the tips, branches and basal parts of the fronds, as well as in new skeletal structures produced by the Algae in the different pCO(2) treatments. Respiration, gross primary production and calcification in light and dark were not significantly affected by increased pCO(2). Algae grown under elevated pCO(2) (550, 750 and 1000 mu atm) formed fewer new structures and produced calcite with a lower mMg/Ca ratio relative to those grown under 380 mu atm. This study supports the assumption that C. elongata from a tidal pool, where pCO(2) fluctuates over diel and seasonal cycles, is relatively robust to elevated pCO(2) compared to other recently investigated Coralline Algae.