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1.
Sea surface temperatures and coral reef bleaching off La Parguera, Puerto Rico (northeastern Caribbean Sea) 总被引:6,自引:0,他引:6
A. Winter R. S. Appeldoorn A. Bruckner E. H. Williams Jr. C. Goenaga 《Coral reefs (Online)》1998,17(4):377-382
Much recent attention has been given to coral reef bleaching because of its widespread occurrence, damage to reefs, and possible
connection to global change. There is still debate about the relationship between temperature and widespread bleaching. We
compared coral reef bleaching at La Parguera, Puerto Rico to a 30-y (1966–1995) record of sea surface temperature (SST) at
the same location. The last eight years of the La Parguera SST record have all had greater than average maximum temperatures;
over the past 30 y maximum summer temperature has increased 0.7 °C. Coral reef bleaching has been particularly frequent since
the middle 1980s. The years 1969, 1987, 1990, and 1995 were especially noteworthy for the severity of bleaching in Puerto
Rico. Seven different annual temperature indices were devised to determine the extent to which they could predict severe coral
bleaching episodes. Three of these, maximum daily SST, days >29.5 °C, and days >30 °C predict correctly the four years with
severe bleaching. A log-log linear relationship was found between SST and the number of days in a given year above that SST
at which severe coral beaching was observed. However, the intra-annual relationship between temperature and the incidence
of bleaching suggests that no one simple predictor of the onset of coral bleaching within a year may be applicable.
Accepted: 17 March 1998 相似文献
2.
Richard J. Pruell Bryan K. Taplin Jonathan D. Karr 《Environmental Biology of Fishes》2012,93(1):61-71
Isotopic ratios of fish otoliths have been used in numerous studies as natural tags or markers to aid in the study of connectivity
among fish populations. We investigated the use of spatial and temporal changes in the stable carbon and oxygen isotope ratios
of otoliths to differentiate juvenile habitats of winter flounder (Pseudopleuronectes americanus). Young-of-the-year (YOY) juvenile winter flounder were collected annually over a three-year period from 18 stations along
the coast of Rhode Island, USA. Sagittal otoliths were removed from fish and analyzed for stable carbon (13C/12C or δ13C) and oxygen (18O/16O or δ18O) isotope ratios using continuous flow isotope ratio mass spectrometry. Differences in isotope ratios were observed among
stations and along salinity gradients in the Narragansett Bay estuary and an estuarine river system (Narrow River). Overall,
the isotope ratio patterns observed among stations were consistent over the three sampling years; however, differences were
noted in isotope ratios and the magnitude of the isotope ratio gradients among years. Significant positive correlations were
noted between salinity and δ13C for two of the three years. For each of the three years sampled there was a highly significant positive correlation (2002,
r = 0.93, P < 0.01; 2003, r = 0.85, P < 0.01; 2004, r = 0.97, P < 0.01) between δ18O and the salinity of the collection site. Also, there was a significant negative correlation between the number of months
of above average river flow and δ18O for the three sampling years (r = 0.99, P < 0.05). These findings suggest that yearly changes in the volume of freshwater inputs to these estuarine habitats may be
related to the differences observed in otolith δ18O isotope ratios. Because of these year-to-year differences, sampling of each cohort may be necessary in order to use this
isotopic technique for winter flounder connectivity studies. 相似文献
3.
Interseasonal comparison of CO2 concentrations, isotopic composition, and carbon dynamics in an Amazonian rainforest (French Guiana) 总被引:2,自引:0,他引:2
Canopy CO2 concentrations in a tropical rainforest in French Guiana were measured continuously for 5 days during the 1994 dry season
and the 1995 wet season. Carbon dioxide concentrations ([CO2]) throughout the canopy (0.02–38 m) showed a distinct daily pattern, were well-stratified and decreased with increasing height
into the canopy. During both seasons, daytime [CO2] in the upper and middle canopy decreased on average 7–10 μmol mol−1 below tropospheric baseline values measured at Barbados. Within the main part of the canopy (≥ 0.7 m), [CO2] did not differ between the wet and dry seasons. In contrast, [CO2] below 0.7 m were generally higher during the dry season, resulting in larger [CO2] gradients. Supporting this observation, soil CO2 efflux was on average higher during the dry season than during the wet season, either due to diffusive limitations and/or
to oxygen deficiency of root and microbial respiration. Soil respiration rates decreased by 40% after strong rain events,
resulting in a rapid decrease in canopy [CO2] immediately above the forest floor of about 50␣μmol mol−1. Temporal and spatial variations in [CO2]canopy were reflected in changes of δ13Ccanopy and δ18Ocanopy values. Tight relationships were observed between δ13C and δ18O of canopy CO2 during both seasons (r
2 > 0.86). The most depleted δ13Ccanopy and δ18Ocanopy values were measured immediately above the forest floor (δ13C = −16.4‰; δ18O = 39.1‰ SMOW). Gradients in the isotope ratios of CO2 between the top of the canopy and the forest floor ranged between 2.0‰ and 6.3‰ for δ13C, and between 1.0‰ and 3.5‰ for δ18O. The δ13Cleaf and calculated c
i/c
a of foliage at three different positions were similar for the dry and wet seasons indicating that the canopy maintained a
constant ratio of photosynthesis to stomatal conductance. About 20% of the differences in δ13Cleaf within the canopy was accounted for by source air effects, the remaining 80% must be due to changes in c
i/c
a. Plotting 1/[CO2] vs. the corresponding δ13C ratios resulted in very tight, linear relationships (r
2 = 0.99), with no significant differences between the two seasons, suggesting negligible seasonal variability in turbulent
mixing relative to ecosystem gas exchange. The intercepts of these relationships that should be indicative of the δ13C of respired sources were close to the measured δ13C of soil respired CO2 and to the δ13C of litter and soil organic matter. Estimates of carbon isotope discrimination of the entire ecosystem, Δe, were calculated as 20.3‰ during the dry season and as 20.5‰ during the wet season.
Received: 3 March 1996 / Accepted: 19 October 1996 相似文献
4.
Eduard A. Titlyanov Serguei I. Kiyashko Tamara V. Titlyanova John A. Raven 《Aquatic Ecology》2010,44(1):13-21
Studies were performed of the carbon and nitrogen stable isotope (δ13C and δ15N) composition (δ13C and δ15N) of the corals Porites cylindrica and P. lutea (5 years after damaging the colonies by the bleaching events) and of epilithic algae settled onto damaged areas of coral
colonies. Coral polyps and three epilithic algal communities (‘red algal turf, green algal turf and red calcified crusts’)
were sampled along the boundary between communities of coral polyps and algal colonizers from differently illuminated habitats
from 2 to 90% of incident surface photosynthetically active radiation (PAR0). It was found that communities with a predominance of red algae significantly differed from communities with a predominance
of green algae in δ13C but not in δ15N values. An influence of habitat irradiance was found only for communities of coral polyps for δ13C and δ15N values: under bright light (70–90% PAR0) polyp tissues of both coral species were significantly enriched in heavy carbon isotopes and insignificantly in nitrogen
isotopes (δ13C values difference ~4‰) relative to tissues of corals under lower light 15–50% PAR0. On the basis of these results we assumed that differences in light intensities in the habitat ranging from 15 to 90% PAR0 do not influence on accessibility of the main carbon and nitrogen sources for corals and algae, and exchange by these elements
between organisms. We also assumed that the relative enrichment in the heavy carbon isotopes of coral tissues in high light
is a result of decreased isotope fractionation (or the absence of fractionation in photosynthesis of their zooxanthellae). 相似文献
5.
This study explores the giant oyster Hyotissa hyotis as a novel environmental archive in tropical reef environments of the Indo-Pacific. The species is a typical accessory component
in coral reefs, can reach sizes of tens of centimetres, and dates back to the Late Pleistocene. Here, a 70.2-mm-long oxygen
and carbon isotope transect through the shell of a specimen collected at Safaga Bay, northern Red Sea, in May 1996, is presented.
The transect runs perpendicularly to the foliate and vesicular layers of the inner ostracum near the ligament area of the
oyster. The measured δ18O and δ13C records show sinusoidal fluctuations, which are independent of shell microstructure. The δ13C fluctuations exhibit the same wavelength as the δ18O fluctuations but are phase shifted. The δ18O record reflects the sea surface temperature variations from 1957 until 1996, possibly additionally influenced by the local
evaporation. Due to locally enhanced evaporation in the semi-enclosed Safaga Bay, the δ18Oseawater value is estimated at 2.17‰, i.e., 0.3–0.8‰ higher than published open surface water δ18O values (1.36–1.85‰) from the region. The mean water temperature deviates by only 0.4°C from the expected value, and the
minimum and maximum values are 0.5°C lower and 2.9°C higher, respectively. When comparing the mean monthly values, however,
the sea surface temperature discrepancy between reconstructed and global grid datasets is always <1.0°C. The δ13C signal is weakly negatively correlated with regional chlorophyll a concentration and with the sunshine duration, which may
reflect changes in the bivalve’s respiration. The study emphasises the palaeogeographic context in isotope studies based on
fossils, because coastal embayments might not reflect open-water oceanographic conditions. 相似文献
6.
Christina E. Reynolds-Henne Matthias Saurer Rolf T. W. Siegwolf 《Trees - Structure and Function》2009,23(4):801-811
Stable isotopic ratios integrate ecosystem variability while reflecting change in both environmental and biological processes.
At sites, where climate does not strongly limit tree growth, co-occurring trees may display large discrepancies in stable
oxygen isotopic ratios (δ18O) due to the interplay between biological processes (competition for light and nutrients, individual tree physiology, etc.)
and climate. For a better quantification of the isotope variability within and among trees, the climatic and/or individual
tree effects on seasonal δ18O variations in precipitation, soil water, leaf water and leaf organic material (whole leaf, cellulose and starch) and annual
δ18O variations in tree-ring cellulose for Fagus sylvatica (Fs), Quercus robur (Qr), Carpinus betulus (Cb) and Pinus sylvestris (Ps) were studied in a mature temperate forest in Switzerland, using a mixed linear regression model technique. Furthermore,
the influence of environmental factors on δ18O was assessed by means of three common isotope fractionation models. Our statistical analysis showed that except for Ps,
a greater portion of δ18O variance in leaf compounds can be explained by individual tree effects, compared to temperature. Concerning tree-ring cellulose,
only Fs and Ps show a significant temperature signal (maximum 12% of the variance explained), while the individual tree effect
significantly explains δ18O for all species for a period of 38 years. Large species differences resulted in a limited ability of the isotope fractionation
models to predict measured values. Overall, we conclude that in a diverse mixed forest stand, individual tree responses reduce
the potential extraction of a temperature signal from δ18O. 相似文献
7.
Evidence is presented that at least 60% of the 184 species of scleractinian corals found on reefs surrounding the Houtman Abrolhos Islands (Western Australia) participate in a late summer mass spawning. These populations are thus reproductively active, despite most species being at the extreme southern limit of their latitudinal range (28° 29°S). In the present study, coral mass spawning occurred in the same month on both temperate (Houtman-Abrolhos) and tropical (Ningaloo) reefs of Western Australia, despite more than two months difference in the timing of seasonal temperture minima between the two regions. This concurrence in the month of spawning suggests that temperature does not operate as a simple direct proximate cue for seasonal spawning synchrony in these populations. Seasonal variation in photoperiod may provide a similar and more reliable signal in the two regions, and thus might be more likely to synchronize the seasonal reproductive rhythms of these corals. Also there is overlap in the nights of mass spawning on the Houtman Abrolhos and tropical reefs of Western Australia, despite significant differences in tidal phase and amplitude between the two regions. This indicates that tidal cycle does not synchronize with the night(s) of spawning on these reefs. Spawning is more likely to be synchronised by lunar cycles. The co-occurrence of the mass spawning with spring tides in Houtman Abrolhos coral populations may be evidence of a genetic legacy inherited from northern, tropical ancestors. Micro-tidal regimes in the Houtman Abrolhos region may have exerted insufficient selective pressure to counteract this legacy. 相似文献
8.
Tom C. L. Bridge Renata Ferrari Mitch Bryson Renae Hovey Will F. Figueira Stefan B. Williams Oscar Pizarro Alastair R. Harborne Maria Byrne 《PloS one》2014,9(11)
High-latitude reefs support unique ecological communities occurring at the biogeographic boundaries between tropical and temperate marine ecosystems. Due to their lower ambient temperatures, they are regarded as potential refugia for tropical species shifting poleward due to rising sea temperatures. However, acute warming events can cause rapid shifts in the composition of high-latitude reef communities, including range contractions of temperate macroalgae and bleaching-induced mortality in corals. While bleaching has been reported on numerous high-latitude reefs, post-bleaching trajectories of benthic communities are poorly described. Consequently, the longer-term effects of thermal anomalies on high-latitude reefs are difficult to predict. Here, we use an autonomous underwater vehicle to conduct repeated surveys of three 625 m2 plots on a coral-dominated high-latitude reef in the Houtman Abrolhos Islands, Western Australia, over a four-year period spanning a large-magnitude thermal anomaly. Quantification of benthic communities revealed high coral cover (>70%, comprising three main morphospecies) prior to the bleaching event. Plating Montipora was most susceptible to bleaching, but in the plot where it was most abundant, coral cover did not change significantly because of post-bleaching increases in branching Acropora. In the other two plots, coral cover decreased while macroalgal cover increased markedly. Overall, coral cover declined from 73% to 59% over the course of the study, while macroalgal cover increased from 11% to 24%. The significant differences in impacts and post-bleaching trajectories among plots underline the importance of understanding the underlying causes of such variation to improve predictions of how climate change will affect reefs, especially at high-latitudes. 相似文献
9.
Corals escape bleaching in regions that recently and historically experienced frequent thermal stress 总被引:1,自引:0,他引:1
D. M. Thompson R. van Woesik 《Proceedings. Biological sciences / The Royal Society》2009,276(1669):2893-2901
The response of coral-reef ecosystems to contemporary thermal stress may be in part a consequence of recent or historical sea-surface temperature (SST) variability. To test this hypothesis, we examined whether: (i) there was a relationship between the historical frequency of SST variability and stress experienced during the most recent thermal-stress events (in 1998 and 2005–2006) and (ii) coral reefs that historically experienced frequent thermal anomalies were less likely to experience coral bleaching during these recent thermal-stress events. Examination of nine detrended coral δ18O and Sr/Ca anomaly records revealed a high- (5.7-year) and low-frequency (>54-year) mode of SST variability. There was a positive relationship between the historical frequency of SST anomalies and recent thermal stress; sites historically dominated by the high-frequency mode experienced greater thermal stress than other sites during both events, and showed extensive coral bleaching in 1998. Nonetheless, in 2005–2006, corals at sites dominated by high-frequency variability showed reduced bleaching, despite experiencing high thermal stress. This bleaching resistance was most likely a consequence of rapid directional selection that followed the extreme thermal event of 1998. However, the benefits of regional resistance could come at the considerable cost of shifts in coral species composition. 相似文献
10.
Isotopic characteristics of typhonic rainwater: typhoons no. 13 (1993) and no. 6 (1996) 总被引:2,自引:0,他引:2
The stable isotope ratios of hydrogen and oxygen were measured for rainwater samples from Typhoon No. 13, which struck Japan
on September 1993, and Typhoon No. 6, which passed in July 1996. Rainwater was collected every hour over 2- to 3-day periods
at Beppu, Japan (33°16′N, 131°29′E), which lies on or close to the typhoon routes. The deuterium excess parameters (δD – 8
·δ18O) of the rainwaters vary over wide ranges from 19.22 to 1.52 for Typhoon No. 13, 1993, and from 6.02 to −8.10 for Typhoon
No. 6, 1996, respectively. Rainwaters with higher d-values precipitated in the forward parts of the typhoons. This is ascribed
to the possibility that the water vapors supplied by the bottom air currents from the front (rear) of the typhoons may be
originally formed by rapid (gentle) evaporation of seawater. Symmetrical patterns of spatial δD and δ18O distributions within the typhoon precipitations, as estimated from the variations in the isotope ratios of the typhoon rainwaters,
should appear from a continuous isotopic fractionation of water vapors with the bottom air currents converging toward the
typhoon center. The weighted means of δD and δ18O of the typhoon precipitations are more negative than those of ordinary rainfall, suggesting that an isotopic influence of
typhoon precipitation on surface waters, e.g., river, stream, lake, and spring waters, may be important.
Received: January 22, 2000 / Accepted: March 24, 2000 相似文献
11.
Concentration and isotopic composition (δ13C and δ18O) of ambient CO2 and water vapour were determined within a Quercus petraea canopy, Northumberland, UK. From continuous measurements made across a 36-h period from three heights within the forest canopy,
we generated mixing lines (Keeling plots) for δa
13CO2, δa C18O16O and δa H2
18O, to derive the isotopic composition of the signal being released from forest to atmosphere. These were compared directly
with measurements of different respective pools within the forest system, i.e. δ13C of organic matter input for δa
13CO2, δ18O of exchangeable water for δa C18O16O and transpired water vapour for δa H2
18O. [CO2] and δa
13CO2 showed strong coupling, where the released CO2 was, on average, 4 per mil enriched compared to the organic matter of plant material in the system, suggesting either fractionation
of organic material before eventual release as soil-respired CO2, or temporal differences in ecosystem discrimination. δa C18O16O was less well coupled to [CO2], probably due to the heterogeneity and transient nature of water pools (soil, leaf and moss) within the forest. Similarly,
δa H2
18O was less coupled to [H2O], again reflecting the transient nature of water transpired to the forest, seen as uncoupling during times of large changes
in vapour pressure deficit. The δ18O of transpired water vapour, inferred from both mixing lines at the canopy scale and direct measurement at the leaf level,
approximated that of source water, confirming that an isotopic steady state held for the forest integrated over the daily
cycle. This demonstrates that isotopic coupling of CO2 and water vapour within a forest canopy will depend on absolute differences in the isotopic composition of the respective
pools involved in exchange and on the stability of each of these pools with time.
Received: 21 March 1998 / Accepted: 10 December 1998 相似文献
12.
P. J. Edmunds 《Coral reefs (Online)》2000,19(1):69-74
To determine what happens to scleractinian corals that have been killed by black band disease (BBD), massive corals with
BBD were monitored for 11 years on a shallow reef (<10 m depth) in St. John, US Virgin Islands. Small quadrats (0.039 m2) were used to compare the rates of scleractinian recruitment to the skeletons of corals killed by either BBD or physical
disturbance (Hurricane Hugo 1989). Coral recruitment was also quantified on the adjacent fringing reef using larger quadrats
(0.25 m2) to detect possible biases associated with using small, permanent quadrats to assess recruitment to BBD-killed corals. Of
28 tagged colonies with BBD in 1988, 43% were lost to Hurricane Hugo in 1989, 7% were lost to unknown causes between 1991
and 1992, and 14 were monitored annually for 11 years; of these, 71% were dead and still in their original growth position
in 1998. Between 1988 and 1997, corals recruited to the BBD-killed surfaces at a rate of 1.1 ± 0.3 recruits · 0.039 m−2 · decade−1 (mean ± SE, n = 14), although mortality reduced the density to 0.3 ± 0.2 recruits · 0.039 m−2 by 1997. The rate of recruitment and the taxonomic composition of the coral recruits to BBD-killed corals were indistinguishable
statistically from those to corals killed by Hurricane Hugo. This demonstrates that BBD creates space that is functionally
the same as other dead coral surfaces in providing a substratum for coral recruitment. However, because coral recruits are
dispersed widely, clumped in distribution and temporally variable in density on the fringing reef as a whole, it is unlikely
that they will be found on monitored coral colonies that have been killed by BBD. While this hypothesis is consistent with
the higher density of recruits on the fringing reef compared with BBD-killed corals, further studies are required to investigate
alternative explanations such as the role of substratum age in favoring recruitment to surfaces other than those killed recently
by BBD.
Accepted: 26 August 1999 相似文献
13.
Background
Coral reefs face increasing pressures particularly when on the edge of their distributions. The Houtman Abrolhos Islands (Abrolhos) are the southernmost coral reef system in the Indian Ocean, and one of the highest latitude reefs in the world. These reefs have a unique mix of tropical and temperate marine fauna and flora and support 184 species of coral, dominated by Acropora species. A significant La Niña event during 2011 produced anomalous conditions of increased temperature along the whole Western Australian coastline, producing the first-recorded widespread bleaching of corals at the Abrolhos.Methodology/ Principal Findings
We examined long term trends in the marine climate at the Abrolhos using historical sea surface temperature data (HadISST data set) from 1900–2011. In addition in situ water temperature data for the Abrolhos (from data loggers installed in 2008, across four island groups) were used to determine temperature exposure profiles. Coupled with the results of coral cover surveys conducted annually since 2007; we calculated bleaching thresholds for monitoring sites across the four Abrolhos groups.Conclusions/ Significance
In situ temperature data revealed maximum daily water temperatures reached 29.54°C in March 2011 which is 4.2°C above mean maximum daily temperatures (2008–2010). The level of bleaching varied across sites with an average of ∼12% of corals bleached. Mortality was high, with a mean ∼50% following the 2011 bleaching event. Prior to 2011, summer temperatures reached a mean (across all monitoring sites) of 25.1°C for 2.5 days. However, in 2011 temperatures reached a mean of 28.1°C for 3.3 days. Longer term trends (1900–2011) showed mean annual sea surface temperatures increase by 0.01°C per annum. Long-term temperature data along with short-term peaks in 2011, outline the potential for corals to be exposed to more frequent bleaching risk with consequences for this high latitude coral reef system at the edge of its distribution. 相似文献14.
The use of the sclerochronology and geochemistry of a New Caledonian (South West Pacific) giant clam Hippopus hippopus shell as markers of environmental changes has been investigated. Growth increment thickness and δ18O ratios were measured on 4 years of shell growth of a modern specimen. During the last year, this giant clam was placed in
a tank equipped for high-frequency environmental monitoring. Because shell is secreted in isotopic equilibrium with the seawater,
the palaeo-sea surface temperature (SST) equation obtained faithfully reproduces the seasonal SST amplitudes. Growth increment
thickness changes are seasonal and, for more than 50%, governed by the SST changes. The transplantation from the in situ site
to the tank and reproduction events reduces the strength of growth and SST relationships. Nevertheless, growth increment thickness
measurements can give information on average, minimal and maximal past SST in diagenetically altered shells. A peculiar growth
event characterized by a short, drastic and significant decrease has been identified and attributed to an intense upwelling
event. This study further highlights the use of giant clam shell δ18O as a SST proxy but also demonstrates that H. hippopus growth increment thickness changes provide useful information on past environmental settings and on exceptional events, for
example, intense upwellings. 相似文献
15.
Differential water resource use by herbaceous and woody plant life-forms in a shortgrass steppe community 总被引:11,自引:0,他引:11
We conducted a study to test the predictions of Walter's two-layer model in the shortgrass steppe of northeastern Colorado.
The model suggests that grasses and woody plants use water resources from different layers of the soil profile. Four plant
removal treatments were applied in the spring of 1996 within a plant community codominated by Atriplex canescens (a C4 shrub) and Bouteloua gracilis (a C4 grass). During the subsequent growing season, soil water content was monitored to a depth of 180 cm. In addition, stem and
leaf tissue of Atriplex, Bouteloua and the streamside tree Populus sargentii were collected monthly during the growing seasons of 1995 and 1996 for analysis of the δ18O value of plant stem water (for comparison with potential water sources) and the δ13C value of leaves (as an indicator of plant water status). Selective removal of shrubs did not significantly increase water
storage at any depth in the measured soil profile. Selective removal of the herbaceous understory (mainly grasses) increased
water storage in the top 60 cm of the soil. Some of this water gradually percolated to lower layers, where it was utilized
by the shrubs. Based on stem water δ18O values, grasses were exclusively using spring and summer rain extracted from the uppermost soil layers. In contrast, trees
were exclusively using groundwater, and the consistent δ13C values of tree leaves over the course of the summer indicated no seasonal changes in gas exchange and therefore minimal
water stress in this life-form. Based on anecdotal rooting-depth information and initial measurements of stem water δ18O, shrubs may have also had access to groundwater. However, their overall δ18O values indicated that they mainly used water from spring and summer precipitation events, extracted from subsurface soil
layers. These findings indicate that the diversity of life-forms found in this shortgrass steppe community may be a function
of the spatial partitioning of soil water resources, and their differential use by grasses, shrubs, and trees. Consequently,
our findings support the two-layer model in a broad sense, but indicate a relatively flexible strategy of water acquisition
by shrubs.
Received: 23 December 1997 / Accepted: 16 September 1998 相似文献
16.
J. M. Guehl A. M. Domenach M. Bereau T. S. Barigah H. Casabianca A. Ferhi J. Garbaye 《Oecologia》1998,116(3):316-330
Functional aspects of biodiversity were investigated in a lowland tropical rainforest in French Guyana (5°2′N, annual precipitation
2200 mm). We assessed leaf δ15N as a presumptive indicator of symbiotic N2 fixation, and leaf and wood cellulose δ13C as an indicator of leaf intrinsic water-use efficiency (CO2 assimilation rate/leaf conductance for water vapour) in dominant trees of 21 species selected for their representativeness
in the forest cover, their ecological strategy (pioneers or late successional stage species, shade tolerance) or their potential
ability for N2 fixation. Similar measurements were made in trees of native species growing in a nearby plantation after severe perturbation
(clear cutting, mechanical soil disturbance). Bulk soil δ15N was spatially quite uniform in the forest (range 3–5‰), whereas average leaf δ15N ranged from −0.3‰ to 3.5‰ in the different species. Three species only, Diplotropis purpurea, Recordoxylon speciosum (Fabaceae), and Sclerolobium melinonii (Caesalpiniaceae), had root bacterial nodules, which was also associated with leaf N concentrations higher than 20 mg g−1. Although nodulated trees displayed significantly lower leaf δ15N values than non-nodulated trees, leaf δ15N did not prove a straightforward indicator of symbiotic fixation, since there was a clear overlap of δ15N values for nodulated and non-nodulated species at the lower end of the δ15N range. Perturbation did not markedly affect the difference δ15Nsoil − δ15Nleaf, and thus the isotopic data provide no evidence of an alteration in the different N acquisition patterns. Extremely large
interspecific differences in sunlit leaf δ13C were observed in the forest (average values from −31.4 to −26.7‰), corresponding to intrinsic water-use efficiencies (ratio
CO2 assimilation rate/leaf conductance for water vapour) varying over a threefold range. Wood cellulose δ13C was positively related to total leaf δ13C, the former values being 2–3‰ higher than the latter ones. Leaf δ13C was not related to leaf δ15N at either intraspecific or interspecific levels. δ13C of sunlit leaves was highest in shade hemitolerant emergent species and was lower in heliophilic, but also in shade-tolerant
species. For a given species, leaf δ13C did not differ between the pristine forest and the disturbed plantation conditions. Our results are not in accord with the
concept of existence of functional types of species characterized by common suites of traits underlying niche differentiation;
rather, they support the hypothesis that each trait leads to a separate grouping of species.
Received: 18 August 1997 / Accepted: 14 April 1998 相似文献
17.
S. Jupiter G. Marion M. Henderson V. Schrameyer M. McCulloch O. Hoegh-Guldberg 《Coral reefs (Online)》2008,27(4):887-903
Coral core records, combined with measurements of coral community structure, were used to assess the long-term impact of multiple
environmental stressors on reef assemblages along an environmental gradient. Multiple proxies (luminescent lines, Ba/Ca, δ15N) that reflect different environmental conditions (freshwater discharge, sediment delivery to the nearshore, nutrient availability
and transformations) were measured in Porites coral cores collected from nearshore reefs at increasing distance from the intensively agricultural region of Mackay (Queensland,
Australia). The corals provide a record (1968–2002) of the frequency and intensity of exposure to terrestrial runoff and fertilizer-derived
nitrogen and were used to assess how the present-day coral community composition may have been influenced by flood-related
disturbance. Reefs closest to the mainland (5–32 km offshore) were characterized by low hard coral cover (≤10%), with no significant
differences among locations. Distinct annual luminescent lines and elevated Ba/Ca values (4.98 ± 0.63 μmol mol−1; mean ± SD) in the most inshore corals (Round Top Island; 5 km offshore) indicated chronic, sub-annual exposure to freshwater
and resuspended terrestrial sediment that may have historically prevented reef formation. By contrast, corals from Keswick
Island (32 km offshore) indicated episodic, high-magnitude exposure to Pioneer River discharge during extreme flood events
(e.g., 1974, 1991), with strongly luminescent lines and substantially enriched coral skeletal δ15N (12–14‰). The reef assemblages at Keswick and St. Bees islands were categorically different from all other locations, with
high fleshy macroalgal cover (80.1 ± 7.2% and 62.7 ± 7.1%, respective mean ± SE) overgrowing dead reef matrix. Coral records
from Scawfell Island (51 km offshore) indicated little exposure to Pioneer catchment influence: all locations from Scawfell
and further offshore had total hard and soft coral cover comparable to largely undisturbed nearshore to middle shelf reefs
of the southern Great Barrier Reef. 相似文献
18.
Dr. Bruce W. Fouke Dr. C. J. Beets Dr. William J. Meyers Dr. Gilbert N. Hanson Dr. Allan J. Melillo 《Facies》1996,35(1):293-320
Summary The Seroe Domi Formation is a 350 m-thick sequence of Neogene marine limestones and silicilastic sandstones cropping out on
the leeward coast of Cura?ao, Netherlands Antilles. Integrated analyses of lithofacies, biostratigraphy, geochemistry and
Sr isotope model age analyses indicate that Seroe Domi Formation has experienced three major episodes of limestone diagenesis
and dolomitization (Dolomites I, I′, and II) that have taken place after successive Mio-Plio-Pleistocene depositional and
subaerial exposure events (Subunits 1, 2, and 3).
Subunit 1, the lowermost 30 to 100 m of the Seroe Domi Formation, is composed of interbedded coralgal grainstone gravity flows,
pelagic wackestones, and allochthonous blocks deposited in Middle Miocene deep-water (>500 m) fore-reef and carbonate slope
environments. Subunit 2, the uppermost 250 m of the Seroe Domi Formation, consists of coralgal packstones with basement-derived
siliciclastic sands that were deposted in shallowing fore-reef to reef-front environments during the Late Miocene to Pliocene.
Subunit 3 siliciclastic sandstones were deposited during the Early Pleistocene within erosional cavities in the Subunit 2
limestones, and are overlain by Late Pleistocene Quaternary Limestone Terraces.
The petrography, distribution and geochemistry of Dolomites I, I′ and II indicate that they were precipitated from seawater-freshwater
mixing zone fluid environments. Dolomite rhombs and meteoric calcite cements within biomolds illustrate that the host Seroe
Domi Formation limestones were subaerially exposed prior to each dolomitization event. Dolomite I (δ18O = +1.04 to +2.46% PDB; δ13C = −2.55 to −6.79 PDB;87Sr/86Sr=0.708866 to 0.708915; Zn=0 ppm; Cu=0 ppm) was precipitated from mixtures of seawater with isotopically-depleted freshwater
during the late Middle Miocene. Dolomite I′ (δ18O = +2.08 to +3.55 PDB, δ13C = −1.53 to 1.69 PDB,87Sr/86Sr=0.708981−0.709030; Zn=0 ppm; Cu=0 ppm) was also precipitated from mixtures of seawater with isotopically-depleted freshwater,
but during late Late Miocene. In contrast, Dolomite II (δ18O = +2.69 to +3.51 PDB; δ13C = −0.34 to +1.53 PDB;87Sr/86Sr=0.708954 to 0.709088; Zn=20 ppm; Cu=20 ppm) precipitated from late Early Pliocene mixtures of seawater with isotopically-depleted
freshwater that had derived Zn, Cu, and less-radiogenic Sr from basalts comprising the Cura?ao basement. 相似文献
19.
Keirith A. Snyder Robert Monnar Simon R. Poulson Peter Hartsough Franco Biondi 《Trees - Structure and Function》2010,24(3):585-595
Diurnal fluctuations of leaf water isotope ratios (δ18O and δD) were measured for Jeffrey (Pinus jeffreyi Balf.) and lodgepole (Pinus contorta Douglas ex Louden) pine. Two trees per species were sampled every few hours on 15–16 October 2005 and 19–20 June 2006. Diurnal
gas exchange was measured during the summer sampling. In fall 2005, leaf water δ18O ranged from 0.7 to 9.0‰, and leaf water δD ranged from −70 to −50‰. In summer 2006, leaf water δ18O ranged from 7.7 to 20.7‰, and leaf water δD ranged from −61 to −24‰. Diurnal variation of leaf water isotope values typically
reached a maximum in early afternoon, began decreasing around midnight, and reached a minimum in mid-morning. Both periods
showed a high degree of enrichment relative to source water, with leaf water–source water enrichments ranging up to 37.8‰
for δ18O, and up to 95‰ for δD. Leaf water enrichment varied by season with summer enrichment being greater than fall enrichment.
A steady-state model (i.e., modified Craig–Gordon modeling) for leaf water isotope compositions did not provide a good fit
to measured values of leaf water. In summer, a non-steady state model provided a better fit to the measured data than the
steady-state model. Our findings demonstrate substantial leaf water enrichment above source water and diurnal variations in
the isotopic composition of leaf water, which has application to understanding short-term variability of atmospheric gases
(water vapor, CO2, O2), climate studies based on the isotopic composition of tree rings, and ecosystem water fluxes. 相似文献
20.
The stable oxygen isotope (δ
18O) composition of Austrocedrus chilensis (D. Don) Endl. (Cupressaceae) tree rings potentially provide retrospective views of changes in environment and climate in the semi-arid lands of Patagonia. We report the development of the first annually resolved δ
18O tree-ring chronology obtained from natural forests of the foothills of the northwestern Patagonian Andes. The isotope record spans between 1890 and 1994 AD. We explore the probable links between this record and the climate of the region. Air temperatures during summer conditions are significantly, but not strongly, inversely correlated with annual δ
18O values from Austrocedrus tree rings. The strongest correlations are between the southern oscillation index (SOI) and the tree rings. The existence of millennial-age Austrocedrus trees in northern Patagonia provides interesting possibilities for examining these climate-related isotopic signals over most of the last 1,000 years. 相似文献