Papers by Pascale Tremblay
AGE, 2015
The manner and extent to which voice amplitude and frequency control mechanisms change with age i... more The manner and extent to which voice amplitude and frequency control mechanisms change with age is not well understood. The related question of whether the assessment of one's own voice evolves with age, concomitant with the acoustical changes that the voice undergoes, also remains unanswered. In the present study, we characterized the aging of voice production mechanisms (amplitude, frequency), compared the aging voice in different experimental contexts (vowel utterance, connected speech) and examined the relationship between voice self-assessment and age-related voice acoustical changes. Eighty healthy adults (20 to 75 years old) participated in the study, which involved computation of several acoustical measures of voice (including measures of fundamental frequency, voice amplitude, and stability) as well as self-assessments of voice. Because depression is frequent in older adults, depression and anxiety scores were also measured. As was expected, analyses revealed age effects on most acoustical measures. However, there was no interaction between age and the ability to produce high/low voice amplitude/frequency, suggesting that voice amplitude and frequency control mechanisms are preserved in aging. Multiple mediation analyses demonstrated that the relationship between age and voice self-assessment was moderated by depression and anxiety scores. Taken together, these results reveal that while voice production undergoes important changes throughout aging, the ability to increase/decrease the amplitude and frequency of voice are preserved, at least within the age range studied, and that depression and anxiety scores have a stronger impact on perceived voice quality than acoustical changes themselves.
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Biogeosciences Discussions, 2013
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The Journal of experimental biology, Jan 26, 2015
Reef-building corals form symbioses with dinoflagellates from the diverse genus Symbiodinium. Thi... more Reef-building corals form symbioses with dinoflagellates from the diverse genus Symbiodinium. This symbiotic association has developed adaptations to acquire and share nutrients, which are essential for its survival and growth in nutrient-poor tropical waters. The host is thus able to prey on a wide range of organic food sources (heterotrophic nutrition) while the symbionts acquire most of the inorganic nutrients (autotrophic nutrition). Nutrient fluxes between the two partners remain however unclear, especially concerning heterotrophically-acquired carbon (C) and nitrogen (N). We combined physiological measurements and pulse-chase isotopic labeling of heterotrophic C and N as well as autotrophic C to track nutrient fluxes in two coral species, Stylophora pistillata and Turbinaria reniformis, in symbiosis with Symbiodinium clades A, and C-D respectively. We showed a rapid acquisition, exchange and a long-term retention of heterotrophic nutrients within the symbiosis, whereas autotro...
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Journal of the Marine Biological Association of the United Kingdom, 2011
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Journal of Experimental Biology, 2012
Corals live in symbiosis with dinoflagellates of the genus Symbiodinum. These dinoflagellates tra... more Corals live in symbiosis with dinoflagellates of the genus Symbiodinum. These dinoflagellates translocate a large part of the photosynthetically fixed carbon to the host, which in turn uses it for its own needs. Assessing the carbon budget in coral tissue is a central question in reef studies that still vexes ecophysiologists. The amount of carbon fixed by the symbiotic association can be determined by measuring the rate of photosynthesis, but the amount of carbon translocated by the symbionts to the host and the fate of this carbon are more difficult to assess. In the present study, we propose a novel approach to calculate the budget of autotrophic carbon in the tissue of scleractinian corals, based on a new model and measurements made with the stable isotope (13)C. Colonies of the scleractinian coral Stylophora pistillata were incubated in H(13)CO (-)(3)-enriched seawater, after which the fate of (13)C was followed in the symbionts, the coral tissue and the released particulate organic carbon (i.e. mucus). Results obtained showed that after 15 min, ca. 60% of the carbon fixed was already translocated to the host, and after 48 h, this value reached 78%. However, ca. 48% of the photosynthetically fixed carbon was respired by the symbiotic association, and 28% was released as dissolved organic carbon. This is different from other coral species, where <1% of the total organic carbon released is from newly fixed carbon. Only 23% of the initially fixed carbon was retained in the symbionts and coral tissue after 48 h. Results show that our (13)C-based model could successfully trace the carbon flow from the symbionts to the host, and the photosynthetically acquired carbon lost from the symbiotic association.
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PLoS ONE, 2012
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Marine Ecology Progress Series, 2011
ABSTRACT
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Marine Ecology Progress Series, 2012
ABSTRACT We assessed pico- and nanoplankton grazing rates as well as dissolved free amino acid (D... more ABSTRACT We assessed pico- and nanoplankton grazing rates as well as dissolved free amino acid (DFAA) uptake rates by the symbiotic coral Stylophora pistillata exposed to thermal and photo stress with concomitant bleaching. The aim was to determine whether these types of food sources could maintain the daily energetic requirements of this coral species. Moreover, the total organic carbon (TOC) flux was measured to quantify bulk C loss or gain. Under control conditions (27 degrees C and 200 mu mol photons m(-2) s(-1)), autotrophic C acquisition covered more than 90% of the respiratory needs of non-bleached corals. Another 10.6% of the respiratory needs were covered by pico- and nanoplankton grazing. Net TOC flux rates were negative, indicating substantial TOC uptake by the corals. After the stress (31 degrees C and 300 mu mol photons m(-2) s(-1)), the contribution of autotrophic C to the respiratory demand decreased to 64% in bleached corals. Pico- and nanoplankton grazing covered only 2 and 7% of the respiratory needs during and after the stress, respectively. These findings demonstrate a substantial stress-induced impact on auto- and heterotrophic capacities for energy acquisition in this species. Although no significant change occurred in the DFAA uptake rates, a significant change in the TOC flux direction was observed, which resulted in TOC net release. Consequently, autotrophy and heterotrophy were less efficient in sustaining the respiratory needs of bleaching and bleached S. pistillata, suggesting that this coral species, and possibly other related species, can be severely endangered by reoccurring and wide-spread bleaching events.
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Coral Reefs, 2014
ABSTRACT Reef-building corals live in symbiosis with dinoflagellates that translocate a large pro... more ABSTRACT Reef-building corals live in symbiosis with dinoflagellates that translocate a large proportion of their photosynthetically fixed carbon compounds to their coral host for its own metabolism. The carbon budget and translocation rate, however, vary depending on environmental conditions, coral host species, and symbiont clade. To quantify variability in carbon translocation in response to environmental conditions, this study assessed the effect of two different irradiance levels (120 and 250 μmol photons m−2 s−1) and feeding regimes (fed with Artemia salina nauplii and unfed) on the carbon budget of the tropical coral Stylophora pistillata. For this purpose, H13CO3−-enriched seawater was used to trace the conversion of photosynthetic carbon into symbiont and coral biomass and excrete particulate organic carbon. Results showed that carbon translocation (ca. 78 %) and utilization were similar under both irradiance levels for unfed colonies. In contrast, carbon utilization by fed colonies was dependent on the growth irradiance. Under low irradiance, heterotrophy was accompanied by lower carbon translocation (71 %), higher host and symbiont biomass, and higher calcification rates. Under high irradiance, heterotrophy was accompanied by higher rates of photosynthesis, respiration, and carbon translocation (90 %) as well as higher host biomass. Hence, levels of resource sharing within coral–dinoflagellate symbioses depend critically on environmental conditions.
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Biogeosciences, 2013
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Nature Methods, 2014
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Papers by Pascale Tremblay