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1.
In this study, juvenile colonies of massive Porites spp. (a combination of P. lutea and P. lobata) from the lagoon of Moorea (W 149°50′, S 17°30′) were damaged and exposed to contrasting conditions of temperature and flow
to evaluate how damage and abiotic conditions interact to affect growth, physiological performance, and recovery. The experiment
was conducted in April and May 2008 and consisted of two treatments in which corals were either undamaged (controls) or damaged
through gouging of tissue and skeleton in a discrete spot mimicking the effects of corallivorous fishes that utilize an excavating
feeding mode. The two groups of corals were incubated for 10 days in microcosms that crossed levels of temperature (26.7 and
29.6°C) and flow (6 and 21 cm s−1), and the response assessed as overall colony growth (change in weight), dark-adapted quantum yield of PSII (F
v/F
m), and healing of the gouged areas. The influence of damage on growth was affected by temperature, but not by flow. When averaged
across flow treatments, damage promoted growth by 25% at 26.7°C, but caused a 25% inhibition at 29.6°C. The damage also affected
F
v/F
m in a pattern that differed between flow speeds, with a 10% reduction at 6 cm s−1, but a 4% increase at 21 cm s−1. Regardless of damage, F
v/F
m at 21 cm s−1 was 11% lower at 26.7°C than at 29.6°C, but was unaffected by temperature at 6 cm s−1. The lesions declined in area at similar rates (4–5% day−1) under all conditions, although the tissue within them regained a normal appearance most rapidly at 26.7°C and 6 cm s−1. These findings show that the response of poritid corals to sub-lethal damage is dependent partly on abiotic conditions,
and they are consistent with the hypothesis that following damage, calcification and photosynthesis can compete for metabolites
necessary for repair, with the outcome affected by flow-mediated mass transfer. These results may shed light upon the ways
in which poritid corals respond to biting by certain corallivorous fishes. 相似文献
2.
Peter J. Edmunds 《Marine Biology》2008,154(1):153-162
Tropical reef corals are well known for their sensitivity to rising temperature, yet surprisingly little is known of the mechanisms
through which temperature acts on intact coral colonies. One such mechanism recently has been suggested by the association
between the growth of juvenile corals and seawater temperature in the Caribbean, which suggests that temperature causes a
transition between isometric and allometric growth scaling in warmer versus cooler years, respectively (Edmunds in Proc R
Soc B 273:2275–2281, 2006). Here, this correlative association is tested experimentally for a cause-and-effect relationship. During April and May 2006,
juvenile colonies (8–35 mm diameter) of massive Porites spp. from Moorea, French Polynesia, were incubated at warm (27.8°C) and cool (25.7°C) temperatures for 15 days, and their
response assessed through the scaling of growth (change in weight) with colony size. The results reveal that the scaling of
colony-specific growth (mg colony−1 day−1) was unaffected by temperature, although growth absolutely was greater at the cool compared to the warm temperature, regardless
of colony size. This outcome was caused by contrasting scaling relationships for area-specific growth (mg cm−2 day−1) that were negatively allometric under warm conditions, but independent of size under cool conditions. In April 2007, a 22
days field experiment confirmed that the scaling of area-specific growth in juvenile Porites spp. is negatively allometric at a warm temperature of 29.5°C. Based on strong allometry for tissue thickness, biomass, and
Symbiodinium density in freshly collected Porites spp., it is hypothesized that the temperature-dependency of growth scaling in these small corals is mediated by the interaction
of temperature with biomass. 相似文献
3.
Peter J. Edmunds 《Marine Biology》2012,159(10):2149-2160
I tested the hypothesis that high pCO2 (76.6 Pa and 87.2 Pa vs. 42.9 Pa) has no effect on the metabolism of juvenile massive Porites spp. after 11 days at 28 °C and 545 μmol quanta m−2 s−1. The response was assessed as aerobic dark respiration, skeletal weight (i.e., calcification), biomass, and chlorophyll fluorescence. Corals were collected from the shallow (3–4 m) back reef of Moorea, French Polynesia (17°28.614′S, 149°48.917′W), and experiments conducted during April and May 2011. An increase in pCO2 to 76.6 Pa had no effect on any dependent variable, but 87.2 Pa pCO2 reduced area-normalized (but not biomass-normalized) respiration 36 %, as well as maximum photochemical efficiency (F v/F m) of open RCIIs and effective photochemical efficiency of RCIIs in actinic light (∆F/); neither biomass, calcification, nor the energy expenditure coincident with calcification (J g−1) was effected. These results do not support the hypothesis that high pCO2 reduces coral calcification through increased metabolic costs and, instead, suggest that high pCO2 causes metabolic depression and photochemical impairment similar to that associated with bleaching. Evidence of a pCO2 threshold between 76.6 and 87.2 Pa for inhibitory effects on respiration and photochemistry deserves further attention as it might signal the presence of unpredictable effects of rising pCO2. 相似文献
4.
Peter J. Edmunds 《Marine Biology》2014,161(7):1531-1542
With coral reefs impacted by climate change, attention is turning to the extent to which scleractinian corals can acclimatize to new physical conditions. The implicit assumption that acclimatization is beneficial has not been tested for scleractinians, although it has been investigated in other systems and has been referred to as the beneficial acclimation hypothesis (BAH). This study tests this hypothesis for scleractinians in experiments on massive Porites spp. from Moorea, French Polynesia (17° 28.564S, 149° 49.018 W). Corals were acclimated for 15–21 days to three temperatures within the range experienced in the collection habitat and then transferred to each of the same temperatures for a treatment period of 14–15 days. The response of the holobiont was measured as growth, the response of the Symbiodinium populations as maximum photochemical efficiency of open reaction centers II (F v/F m). An ANOVA with polynomial contrasts was used to distinguish among the BAH, three alternative hypotheses and a null hypothesis describing the consequences of acclimation. In the first experiment (2009), massive Porites spp. were unresponsive to temperature. In the second experiment (2013), the BAH was not supported, but growth of the holobiont conformed to the “hotter is better” (HIB) hypothesis; the response of Symbiodinium populations conformed to developmental buffering. These results suggest that acclimation by massive Porites spp. to temperatures experienced routinely in the natural environment does not have clear beneficial value for growth or photochemical efficiency (i.e., BAH was not supported), but they reveal that acclimation to increased temperature can have value in responding to a variety of subsequent temperatures (i.e., support for HIB). 相似文献
5.
The effects of light exposure on the photosynthetic activity of kleptoplasts were studied in the sacoglossan mollusc Elysia viridis. The photosynthetic activity of ingested chloroplasts was assessed in vivo by non-destructively measuring photophysiological
parameters using pulse amplitude modulation (PAM) fluorometry. Animals kept under starvation were exposed to two contrasting
light conditions, 30 μmol photons m−2 s−1 (low light, LL), and 140 μmol photons m−2 s−1 (high light, HL), and changes in photosynthetic activity were monitored by measuring the maximum quantum yield of photosystem
II (PSII), F
v/F
m, the minimum fluorescence, F
o, related to chlorophyll a content, and by measuring rapid light-response curves (RLC) of relative electron transport rate (rETR). RLCs were characterised
by the initial slope of the curve, αRLC, related to efficiency of light capture, and the maximum rETR level, rETRm,RLC, determined by the carbon-fixation metabolism. Starvation induced the decrease of all photophysiological parameters. However,
the retention of photosynthetic activity (number of days for F
v/F
m > 0), as well as the rate and the patterns of its decrease over time, varied markedly with light exposure. Under HL conditions,
a rapid, exponential decrease was observed for F
v/F
m, αRLC and rETRm,RLC, F
o not showing any consistent trend of variation, and retention times ranged between 6 and 15 days. These results suggested
that the retention of chloroplast functionality is limited by photoinactivation of PSII reaction center protein D1. In contrast,
under LL conditions, a slower decrease in all parameters was found, with retention times varying from 15 to 57 days. F
v/F
m, αRLC and rETRm,RLC exhibited a bi-phasic pattern composed by a long phase of slow decrease in values followed by a rapid decline, whilst F
o decayed exponentially. These results were interpreted as resulting from lower rates of D1 photoinactivation under low light
and from the gradual decrease in carbon provided by photosynthesis due to reduction of functional photosynthetic units. 相似文献
6.
Short-term effects of temperature and irradiance on oxygenic photosynthesis and O2 consumption in a hypersaline cyanobacterial mat were investigated with O2 microsensors in a laboratory. The effect of temperature on O2 fluxes across the mat–water interface was studied in the dark and at a saturating high surface irradiance (2162 μmol photons
m−2 s−1) in the temperature range from 15 to 45 °C. Areal rates of dark O2 consumption increased almost linearly with temperature. The apparent activation energy of 18 kJ mol−1 and the corresponding Q
10 value (25 to 35 °C) of 1.3 indicated a relative low temperature dependence of dark O2 consumption due to mass transfer limitations imposed by the diffusive boundary layer at all temperatures. Areal rates of
net photosynthesis increased with temperature up to 40 °C and exhibited a Q
10 value (20 to 30 °C) of 2.8. Both O2 dynamics and rates of gross photosynthesis at the mat surface increased with temperature up to 40 °C, with the most pronounced
increase of gross photosynthesis at the mat surface between 25 and 35 °C (Q
10 of 3.1). In another mat sample, measurements at increasing surface irradiances (0 to 2319 μmol photons m−2 s−1) were performed at 25, 33 (the in situ temperature) and 40 °C. At all temperatures, areal rates of gross photosynthesis saturated
with no significant reduction due to photoinhibition at high irradiances. The initial slope and the onset of saturation (E
k = 148 to 185 μmol photons m−2 s−1) estimated from P versus E
d curves showed no clear trend with temperature, while maximal photosynthesis increased with temperature. Gross photosynthesis
was stimulated by temperature at each irradiance except at the lowest irradiance of 54 μmol photons m−2 s−1, where oxygenic gross photosynthesis and also the thickness of the photic zone was significantly reduced at 40 °C. The compensation
irradiance increased with temperature, from 32 μmol photons m−2 s−1 at 25 °C to 77 μmol photons m−2 s−1 at 40 °C, due to increased rates of O2 consumption relative to gross photosynthesis. Areal rates of O2 consumption in the illuminated mat were higher than dark O2 consumption at corresponding temperatures, due to an increasing O2 consumption in the photic zone with increasing irradiance. Both light and temperature enhanced the internal O2 cycling within hypersaline cyanobacterial mats.
Received: 30 November 1999 / Accepted: 11 April 2000 相似文献
7.
Response of zooxanthellae in symbiosis with the Mediterranean corals Cladocora caespitosa and Oculina patagonica to elevated temperatures 总被引:1,自引:0,他引:1
Riccardo Rodolfo-Metalpa Cécile Richard Denis Allemand Carlo Nike Bianchi Carla Morri Christine Ferrier-Pagès 《Marine Biology》2006,150(1):45-55
Scleractinian symbiotic corals living in the Ligurian Sea (NW Mediterranean Sea) have experienced warm summers during the last decade, with temperatures rapidly increasing, within a few days, to 3–4°C above the mean value of 24°C. The effect of elevated temperatures on the photosynthetic efficiency of zooxanthellae in symbiosis with temperate corals has not been well investigated. In this study, the corals, Cladocora caespitosa and Oculina patagonica were collected in the Ligurian Sea (44°N, 9°E), maintained during 2 weeks at the mean summer temperature of 24°C and then exposed during 48 h to temperatures of 24 (control), 27, 29 and 32°C. Chlorophyll (chl) fluorescence parameters [F
v/F
m, electron transport rate (ETR), non-photochemical quenching (NPQ)] were measured using pulse amplitude modulated (PAM) fluorimetry before, during the thermal increase, and after 1 and 7 days of recovery (corals maintained at 24°C). Zooxanthellae showed a broad tolerance to temperature increase, since their density remained unchanged and there was no significant reduction in their maximum quantum yield (F
v/F
m) or ETR up to 29°C. This temperature corresponded to a 5°C increase compared to the mean summer temperature (24°C) in the Ligurian Sea. At 32°C, there was a significant decrease in chl contents for both corals. This decrease was due to a reduction in the chl/zooxanthellae content. For C. caespitosa, there was also a decrease in ETRmax, not associated with a change in F
v/F
m or in the non-photochemical quenching (NPQ); for O. patagonica, both ETRmax and F
v/F
m significantly decreased, and NPQmax showed a significant increase. Damages to the photosystem II appeared to be reversible in both corals, since F
v/F
m values returned to normal after 1 day at 24°C. Zooxanthellae in symbiosis with the Mediterranean corals investigated can therefore be considered as resistant to short-term increases in temperature, even well above the maximum temperatures experienced by these corals in summer. 相似文献
8.
Helen S. Findlay Michael A. Kendall John I. Spicer Stephen Widdicombe 《Marine Biology》2010,157(4):725-735
Ocean acidification and global warming are occurring concomitantly, yet few studies have investigated how organisms will respond
to increases in both temperature and CO2. Intertidal microcosms were used to examine growth, shell mineralogy and survival of two intertidal barnacle post-larvae,
Semibalanus balanoides and Elminius modestus, at two temperatures (14 and 19°C) and two CO2 concentrations (380 and 1,000 ppm), fed with a mixed diatom-flagellate diet at 15,000 cells ml−1 with flow rate of 10 ml−1 min−1. Control growth rates, using operculum diameter, were 14 ± 8 μm day−1 and 6 ± 2 μm day−1 for S. balanoides and E. modestus, respectively. Subtle, but significant decreases in E. modestus growth rate were observed in high CO2 but there were no impacts on shell calcium content and survival by either elevated temperature or CO2. S. balanoides exhibited no clear alterations in growth rate but did show a large reduction in shell calcium content and survival under
elevated temperature and CO2. These results suggest that a decrease by 0.4 pH(NBS) units alone would not be sufficient to directly impact the survival of barnacles during the first month post-settlement.
However, in conjunction with a 4–5°C increase in temperature, it appears that significant changes to the biology of these
organisms will ensue. 相似文献
9.
Glenn Lurman Till Blaser Miles Lamare Koh-Siang Tan Hans Poertner Lloyd S. Peck Simon A. Morley 《Marine Biology》2010,157(8):1705-1712
Temperature and mitochondrial plasticity are well studied in fishes, but little is known about this relationship in invertebrates.
The effects of habitat temperature on mitochondrial ultrastructure were examined in three con-familial limpets from the Antarctic
(Nacella concinna), New Zealand (Cellana ornata), and Singapore (Cellana radiata). The effects of seasonal changes in temperature were also examined in winter and summer C. ornata. Stereological methods showed that limpet pedal myocytes were 1–2 orders of magnitude smaller in diameter (≈3.5 μm) than
in vertebrates, and that the diameter did not vary as a function of temperature. Mitochondrial volume density (Vv(mt,f)) was approximately 2–4 times higher in N. concinna (0.024) than in the other species (0.01 and 0.006), which were not significantly different from each other. Mitochondrial
cristae surface density (Sv(im,mt)) was significantly lower in summer C. ornata (24.1 ± 0.50 μm2 μm−3) than both winter C. ornata (32.3 ± 0.95 μm2 μm−3) and N. concinna (34.3 ± 4.43 μm2 μm−3). The surface area of mitochondrial cristae per unit fibre volume was significantly higher in N. concinna, due largely to the greater mitochondrial volume density. These results and previous studies indicate that mitochondrial
proliferation in the cold is a common, but not universal response by different species from different thermal habitats. Seasonal
temperature decreases on the other hand, leading preferentially to an increase in cristae surface density. Stereological measures
also showed that energetic reserves, i.e. lipid droplets and glycogen in the pedal muscle changed greatly with season and
species. This was most likely related to gametogenesis and spawning. 相似文献
10.
Colonial photosynthetic marine organisms often exhibit morphological phenotypic plasticity. Where such plasticity leads to
an improved balance between rates of photosynthesis and maintenance costs, it is likely to have adaptive significance. To
explore whether such phenotypic plasticity leads to more favourable within-colony irradiance for reef-building branching corals,
this relationship was investigated for two coral species Acropora humilis and Stylophora pistillata, along a depth gradient representing light habitats ranging from 500 to 25 μmol photons m−2 s−1, during 2006 at Heron Island, Great Barrier Reef (23.44°S, 151.91°E). In the present study changes in flow-modulated mass
transfer co-varied with light as a function of depth. In low-light (deep) habitats, branch spacing (colony openness) in A. humilis and S. pistillata was 40–50% greater than for conspecifics in high-light environments. Also, branches of A. humilis in deep water were 40–60% shorter than in shallow water. Phenotypic changes in these two variables lead to steeper within-colony
light attenuation resulting in 38% higher mean internal irradiance (at the tissue surface) in deep colonies compared to shallow
colonies. The pattern of branch spacing was similar for S. pistillata, but this species displayed an alternate strategy with respect to branch length: shade adapted deep and cave colonies developed
longer and thinner branches, allowing access to higher mass transfer and irradiance. Corals in cave habitats allowed 20% more
irradiance compared to colonies found in the deep, and had a 47% greater proportion of irradiance compared to colonies in
the shallow high-light environment. Such phenotypic regulation of internal light levels on branch surfaces partly explains
the broad light niches of many branching coral species.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
11.
The diatom Cylindrotheca closterium was exposed to transient light- and osmotic conditions as occur during its tidal emersion. The objective was to analyze how
this simulated emersion contributes to the production of active oxygen species (AOS) and via this, to oxidative cell damage.
Light- and salinity conditions were varied in factorial combination: low light (no UVB) or high light (unweighted UVB-dose
rates of respectively 0.01; 0.07; 0.24; 1.03 W m−2) at normal (30 psu) or high salinity (60 psu). UVB (0.01–0.24 W m−2) and high salinity had a significant, negative effect on the photosynthetic efficiencies ΔF/F
m’ (steady-state quantum yield) and F
v/F
m (maximum yield). UVB at 1.03 W m−2 (15 kJ m−2 d−1) almost arrested electron transport. At ecologically relevant UVB levels, i.e. below 0.24 W m−2 (≈3.4 kJ m−2 d−1) with UVB:PAR<0.4:100 (PAR photosynthetically active radiation) only dynamic photoinhibition was observed (protection via
heat dissipation). Non-photochemical quenching was positively correlated with the de-epoxidation of diadinoxanthin (DD) to
diatoxanthin (DT). A decreasing ratio DT/(DD+DT) after 4 h of UVB at >0.07 W m−2 and at 60 psu indicated a reversal of the diatom xanthophyll cycle (diminished photoprotection) which may be caused by an
enhanced AOS production. Oxidative stress and -damage to C. closterium cells were assessed applying fluorescent indicator dyes, via confocal microscopy and quantitative image analysis. AOS production
rates (cellular DCF fluorescence) were stimulated by UV, and were ~50% higher at 60 psu. AOS production decreased with an
increasing pre-exposure (0–4 h) to normal UVB (0.24 W m−2), which indicated a stimulation of the antioxidative defence. Non-protein thiols (indicator CMF) and glutathione pools (HPLC-analyzed)
decreased with UVB-dose rates (0.01–0.24 W m−2), most likely due to AOS-mediated thiol oxidation. Hypersalinity (60 psu) and UVB (0.01–0.24 W m−2) caused membrane depolarization (dye DIBAC4(3)) and phospholipid hydrolysis (phospholipase A2 dye: bis-BODIPY FL-C11-PC). AOS production may have diminished the membrane polarity, and peroxidized the membrane lipids (HPLC-analyzed malondialdehyde)
which enhanced PLA2 activity. The dyes indicated an increased oxidative (lipid) damage at a 15% inhibition of photosynthesis in this diatom,
at UVB levels and salinities that can be expected in situ during its periodic tidal emersion. 相似文献
12.
In situ seagrass photosynthesis measured using a submersible, pulse-amplitude modulated fluorometer 总被引:8,自引:0,他引:8
Assessments of photosynthetic activity in marine plants can now be made in situ using a newly developed, submersible, pulse-amplitude
modulated (PAM) fluorometer: Diving-PAM. PAM fluorometry provides a measure of chlorophyll a fluorescence using rapid-light curves in which the electron-transport rate can be determined for plants exposed to ambient
light conditions. This technique was used to compare the photosynthetic responses of seagrasses near Rottnest Island, Western
Australia. Several fluorescence parameters were measured as a function of time of day and water depth; electron-transport
rate (ETR), quantum yield, photochemical quenching and non-photochemical quenching and Photosystem II (PSII) photochemical
efficiency (F
v
:F
m
ratio) were measured. Results indicate that recent light-history plays a crucial role in seagrass photosynthetic responses.
Maximum ETR of Posidonia australis, Amphibolis antarctica and Halophila ovalis is influenced by the irradiance during the diurnal cycle, with low rates at dawn and dusk (<10 μmol electron m−2 s−1), highest rates in late morning (40 to 60 μmol electron m−2 s−1) and a mid-day depression. Maximum ETR and PSII photochemical efficiency varied widely between seagrass species and were
not correlated. A comparison of photochemical to non-photochemical quenching indicated that seagrasses in shallow water receiving
high light have a high capacity for non-photochemical quenching (e.g. light protection) compared to seagrasses in deep water.
These results indicate that in situ measurements of photosynthesis will provide new insights into the mechanisms and adaptive
responses of marine plants.
Received: 26 May 1997 / Accepted: 27 May 1998 相似文献
13.
Effect of temperature fluctuations and food supply on the growth and metabolism of juvenile sea scallops (Placopecten magellanicus) 总被引:1,自引:0,他引:1
On the eastern shore of Nova Scotia late summer atmospheric systems cause upwelling of shelf water; the associated temperature
variations of 10 °C with a 6 to 8 d period are comparable in magnitude to the seasonal variation. A laboratory study was undertaken
to assess the effects of these temperature fluctuations on sea scallop (Placopecten magellanicus) growth and metabolism. In a factorial design, scallops were subjected to constant (10 °C) or a variable (6 to 15 °C) 8 d
temperature cycle, and either a low (seston in filtered seawater) or high (seston supplemented with cultured phytoplankton)
food diet. During the 48 d experiment scallop mortality was low and growth positive in all treatments. Shell and total tissue
growth rate did not differ between temperature treatments, but growth in the high food treatments was 40 to 50% higher than
in the low food treatments. However, soft tissue (excluding adductor) growth did show a temperature treatment effect; growth
rates were significantly higher in the fluctuating temperature treatment, due in part to greater gonad development. Weight-standardized
rates of scallop oxygen consumption (V
sO2 , μmol O2 g−1 h−1) were 20 to 25% higher in high food than in low food treatments, consistent with the expected increase in respiration due
to the higher growth rates. Scallop metabolism did not acclimate to the fluctuating temperature cycle; V
sO2 and ammonium excretion (V
sNH+
4, μmol O2 g−1 h−1) remained dependent on ambient temperature throughout the experiment. V
sNH+
4 Q10 (2.77) was higher than V
sO2 Q10 (2.01) which was reflected in a decrease in the O:N ratio at 15 °C, indicating a shift toward increased protein catabolism
and a stressed state. At 10 °C, V
sO2 and V
sNH+
4 in the variable temperature treatments were 15 to 18% lower than in the constant temperature treatments, a difference that
was not detected in growth measurements. Results demonstrate that the metabolism of Placopecten magellanicus, unlike some bivalve species, is tightly coupled to fluctuations in ambient temperature. Although an absence of compensatory
acclimation had a minimal effect on growth in this study, if high temperatures were combined with low food conditions a reduction
in scallop production could result.
Received: 23 June 1998 / Accepted: 8 February 1999 相似文献
14.
Microsensor studies of photosynthesis and respiration in the symbiotic foraminifer Orbulina universa 总被引:1,自引:0,他引:1
Oxygen and pH microelectrodes were used to investigate the microenvironment of the planktonic foraminifer Orbulina universa and its dinoflagellate endosymbionts. A diffusive boundary layer surrounds the foraminiferal shell and limits the O2 and proton transport from the shell to the ambient seawater and vice versa. Due to symbiont photosynthesis, high O2 concentrations of up to 206% air saturation and a pH of up to 8.8, i.e. 0.5 pH units above ambient seawater, were measured
at the shell surface of the foraminifer at saturating irradiances. The respiration of the host–symbiont system in darkness
decreased the O2 concentration at the shell surface to <70% of the oxygen content in the surrounding air-saturated water. The pH at the shell
surface dropped to 7.9 in darkness. We measured a mean gross photosynthetic rate of 8.5 ± 4.0 nmol O2 h−1 foraminifer−1. The net photosynthesis averaged 5.3 ± 2.7 nmol O2 h−1. In the light, the calculated respiration rates reached 3.9 ± 1.9 nmol O2 h−1, whereas the dark respiration rates were significantly lower (1.7 ± 0.7 nmol O2 h−1). Experimental light–dark cycles demonstrated a very dynamic response of the symbionts to changing light conditions. Gross
photosynthesis versus scalar irradiance curves (P vs E
o curves) showed light saturation irradiances (E
k) of 75 and 137 μmol photons m−2 s−1 in two O. universa specimens, respectively. No inhibition of photosynthesis was observed at irradiance levels up to 700 μmol photons m−2 s−1. The light compensation point of the symbiotic association was 50 μmol photons m−2 s−1. Radial profile measurements of scalar irradiance (E
o) inside the foraminifera showed a slight increase at the shell surface up to 105% of the incident irradiance (E
d).
Received: 26 January 1998 / Accepted: 11 April 1998 相似文献
15.
Rates of progression and transmission of black band disease (BBD) on the staghorn coral, Acropora muricata, were compared between months for seasonal in situ studies and between temperature treatments in experimental aquaria manipulations
at Lizard Island on the Great Barrier Reef (GBR). In situ field experiments demonstrated that BBD progressed along branches
approximately twice as fast (1.7–2.4 times) during the austral summer month of January (0.99 ± 0.04 cm/day) than in the cooler
months of July (0.58 ± 0.04 cm/day) and May (0.41 ± 0.07 cm/day). Transmission of BBD between colonies was also accelerated
in warmer months, with signs of infection becoming visible 1.2 days earlier in January compared to May. The greater seawater
temperatures by ∼2 to 3°C and light intensities by up to 650 μE/m2/s in January, suggest that rates of progression and transmission of BBD are linked to one or both of these parameters. Manipulative
experiments in summer provide corroborative evidence that elevated temperatures increase rates of BBD progression, with the
disease progressing 1.3 times more rapidly in the 32°C elevated temperature treatment than in the 30°C ambient treatment (1.17 ± 0.06 cm/day
versus 0.92 ± 0.07 cm/day; F
2,6 = 7.66, P = 0.022). In contrast, although a trend for greatest BBD progression was measured in elevated temperature treatments of 29°C
(0.46 ± 0.07 cm/day) and 31°C (0.52 ± 0.06 cm/day) in winter, these rates did not differ significantly (F
3,7 = 1.72, P = 0.249) from those measured for the ambient 27°C treatment (0.37 ± 0.06 cm/day) or the field controls (0.41 ± 0.09 cm/day).
The lower rates of BBD progression in the 31°C winter treatment (0.52 ± 0.06 cm/day) than in the 30°C (0.92 ± 0.07 cm/day)
summer treatment, may have been a response to 28-fold decreased light irradiance in the former, suggesting that high irradiance
in combination with elevated temperatures may promote progression of BBD. Results from this study indicate that the impact
of elevated temperature on BBD progression is complex with a combination of environmental factors including temperature and
light playing key roles in progression and transmission of the disease. 相似文献
16.
Andrew McMinn Andrew Pankowskii Chris Ashworth Ranjeet Bhagooli Peter Ralph Ken Ryan 《Marine Biology》2010,157(6):1345-1356
Primary production at Antarctic coastal sites is contributed from sea ice algae, phytoplankton and benthic algae. Oxygen microelectrodes
were used to estimate sea ice and benthic primary production at several sites around Casey, a coastal area in eastern Antarctica.
Maximum oxygen export from sea ice was 0.95 mmol O2 m−2 h−1 (~11.7 mg C m−2 h−1) while from the sediment it was 6.08 mmol O2 m−2 h−1 (~70.8 mg C m−2 h−1). When the ice was present O2 export from the benthos was either low or negative. Sea ice algae assimilation rates were up to 3.77 mg C (mg Chl-a)−1 h−1 while those from the benthos were up to 1.53 mg C (mg Chl-a)−1 h−1. The contribution of the major components of primary productivity was assessed using fluorometric techniques. When the ice
was present approximately 55–65% of total daily primary production occurred in the sea ice with the remainder unequally partitioned
between the sediment and the water column. When the ice was absent, the benthos contributed nearly 90% of the primary production. 相似文献
17.
In situ measurements of seagrass photosynthesis in relation to inorganic carbon (Ci) availability, increased pH and an inhibitor
of extracellular carbonic anhydrase were made using an underwater pulse amplitude modulated (PAM) fluorometer. By combining
the instrument with a specially designed Perspex chamber, we were able to alter the water surrounding a leaf without removing
it from the growing plant. Responses to Ci within the chamber showed that subtidal plants of the seagrasses Cymodocea serrulata and Halophila ovalis had photosynthetic rates that were limited by the ambient Ci concentration depending on the irradiance that was available
during short-term photosynthesis–irradiance trials. Relative electron transport rates (RETRs) at light saturation (up to 500 μ
mol photons m−2 s−1) increased by 66–100% when the Ci concentration was increased from ca. 2.2 to 6.2 mM. On the other hand, intertidal plants
of the same species exhibited a much lesser limitation of photosynthesis by Ci at any irradiance (up to 1500 μ mol photons
m−2 s−1). Both species were able to use HCO−
3 efficiently, and there was stronger evidence for direct uptake of HCO−
3 rather than extracellular dehydration of HCO−
3 to CO2 prior to Ci uptake. Subtidally, H. ovalis and C. serrulata grew to 10 and 12 m, respectively, where ambient irradiances were approximately 16 and 11% of those at the surface. Maximum
RETRs (at light saturation) were lower for these deep-growing plants than for the intertidally growing ones. For both species,
the onset of light saturation of photosynthesis (E
k) occurred at approximately 100 μ mol photons m−2 s−1 for the deep water populations, which was four and two times lower than for the shallow populations of C. serrulata and H. ovalis, respectively. This, and the differences in maximal photosynthetic rates (RETR
max), reflects an acclimation of the deep-growing populations to the lower light environment. The results presented here show
that photosynthesis, as measured in situ, was limited by the availability of Ci for the deeper growing plants in Zanzibar,
while the intertidally growing plants photosynthesised at close to Ci saturation. The latter result is contrary to previous
conclusions regarding Ci limitations for these intertidal plants, and, in general, our findings highlight the need for performing
similar experiments in situ rather than under laboratory conditions.
Received: 4 April 2000 / Accepted: 31 August 2000 相似文献
18.
This study examined the response of a coral holobiont to thermal stress when the bacterial community was treated with antibiotics. Colonies of Pocillopora damicornis were exposed to broad and narrow-spectrum antibiotics targeting coral-associated α and γ-Proteobacteria. Corals were gradually heated from the control temperature of 26 to 31 °C, and measurements were made of host, zooxanthellar and microbial condition. Antibiotics artificially reduced the abundance and activity of bacteria, but had minimal effect on zooxanthellae photosynthetic efficiency or host tissue protein content. Heated corals without antibiotics showed significant declines in F V /F M , typical of thermal stress. However, heated corals treated with antibiotics showed severe tissue loss in addition to a decline in F V /F M . This study demonstrated that a disruption to the microbial consortium diminished the resilience of the holobiont. Corals exposed to antibiotics under control temperature did not bleach, suggesting that temperature may be an important factor influencing the activity, diversity and ecological function of the holobiont bacterial community. 相似文献
19.
In situ measurements of photosynthetic irradiance responses of two Red Sea sponges growing under dim light conditions 总被引:6,自引:0,他引:6
Photosynthetic responses to irradiance by the photosymbionts of the two Red Sea sponges Theonella swinhoei (Gray) and Clionavastifica (Hancock) growing under dim light conditions were measured in situ (in September 1997) using a newly developed underwater
pulse amplitude modulated (PAM) fluorometer. Relative rates of photosynthetic electron transport (ETR) were calculated as
the effective quantum yield of photosystem II (Y ) multiplied with the photosynthetic photon flux (PPF). Photosynthesis versus irradiance (P-I ) curves, obtained within minutes, showed that individual specimens of both sponges, growing under very low light conditions,
feature lower light saturation points as well as lower maximal ETRs than individuals growing under higher light. Evaluations
of such curves using low irradiances of the actinic light source (20 to 130 μmol photons m−2 s−1) showed a general decrease in Y, with a shoulder from the lowest irradiance applied till 20 to 30 μmol photons m−2 s−1. Point measurements yielded ETRs close to what could be estimated from the P-I curves. These point measurements also revealed good correlations between the diurnally changing ambient irradiances (1 to
50 μmol photons m−2 s−1) and average ETR values for both species. Further analysis showed that although Y values varied considerably between the different point measurements, they did not decrease significantly with light under
these very low irradiances. Therefore, PPF rather than Y seems to determine the in situ diel photosynthetic performance at the low ambient irradiances experienced by these sponges.
Received: 22 November 1997 / Accepted: 8 April 1998 相似文献
20.
Yinian Zhu Xuehong Zhang Honghu Zeng Huili Liu Na He Meifang Qian 《Environmental Chemistry Letters》2011,9(3):339-345
Svabite is a secondary arsenate mineral, calcium fluoride arsenate [Ca5(AsO4)3F], in the apatite group of phosphates. Its dissolution and subsequent release of aqueous species play an important role in
the cycling of arsenic and fluoride in the environment, but the thermodynamic and kinetic properties of svabite dissolution
have never been investigated. In the present study, svabite was prepared by precipitation and characterized by various techniques,
and then dissolution of synthetic svabite was studied at 25, 35 and 45°C in a series of batch experiments. In addition, the
aqueous concentrations from the batch dissolution were used to calculate the solubility product and free energy of formation
of svabite. The results of the X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy
analyses indicated that the synthetic, microcrystalline svabite with apatite structure used in the experiments has not changed
after dissolution. For the dissolution of svabite [Ca5(AsO4)3F] in ultrapure water, F− ions were initially found to dissolve preferentially when compared with calcium and arsenate. Preferential dissolution of
arsenate when compared with that of calcium was also observed. Dissolution of svabite in aqueous medium appeared to be always
non-stoichiometric at the beginning, but when a dissolution equilibrium or steady state was reached at 25 and 35°C, the solid
dissolved almost stoichiometrically. The release of calcium, arsenic and fluoride to solution increased with decreasing temperature.
The mean K
sp
value was calculated for Ca5(AsO4)3F of 10−39.21 (10−39.18 ~ 10−39.24) at 25°C; the free energy of formation ΔG
f
o
[Ca5(AsO4)3F] was −5210.46 kJ/mol. 相似文献