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1.
Colony size is an important life-history characteristic of corals and changes in colony size will have significant effects
on coral populations. This study summarizes ∼21,000 haphazard colony size measurements of 26 common coral taxa (mostly coral
genera) collected annually between 1992 and 2006 in seven Kenyan reef lagoons. There was a major coral bleaching and mortality
event in early 1998 and all seven reefs were affected. The seven locations include two long-protected Marine National Parks
(Malindi and Watamu), one relatively recently established park (Mombasa), and four unprotected locations (Vipingo, Kanamai,
Ras Iwatine, and Diani). They span about 150 km and represent three distinct fishery management regimes: old protected (OP),
newly protected (NP), and unprotected (UP). Seventeen taxa had statistically significant different sizes for comparisons of
the management regimes, with only one genus, Pavona, having larger sizes in the unprotected reefs. The size of eight coral genera showed a significant time and management interaction,
and size frequency differences that existed in management areas prior to 1998 were further increased after the bleaching event.
Time alone was a significant factor for eleven genera, and in all cases colonies were smaller after 1998. For most taxa, colony
size distributions were significantly skewed and had right-tailed distributions. After 1998, the right-tailed distributions
of Acropora, Hydnophora, and Montipora were significantly reduced. Most taxa had peaky distributions and only Acropora experienced a statistically significant change from peaky to flat. The mean sizes of taxa were not related to their mortality
across 1998, which indicates that the size effect was within rather than between taxa. Astreopora and Platygyra were well-sampled taxa that did not show an effect of management, but had reduced median sizes across 1998. Consequently,
no taxa were tolerant of both fishing and bleaching disturbances and the combined effect was to reduce the size of all corals. 相似文献
2.
Ross J. Jones 《Marine Biology》2008,154(1):65-80
Coral bleaching events are often associated with higher levels of coral mortality but when this occurs in the chronology of
individual bleaching events is poorly documented. Knowing when mortality occurs is important for understanding molecular mechanisms
and the putative adaptive significance of the response (the Adaptive Bleaching Hypothesis). In a detailed study of a coral
bleaching event on the Great Barrier Reef, involving weekly and twice weekly repetitive observations of >200 individually
marked corals over an 18 month period (∼16,000 observations), it is shown that bleaching in Acropora latistella, A. subulata and Turbinaria mesenterina was an acute, rapid response, occurring within days of a peak in seawater temperatures exceeding previously described thresholds.
Subsurface light levels, measured over the duration of the event, were not anomalous. Full bleaching (i.e. whole colonies
turning bone-white) and partial bleaching (white patches) was observed in the Acropora spp. whilst the T. mesenterina colonies typically paled to a light brown colour. Algal densities in bleached corals were 10–30% of those of normally pigmented
corals (∼2.5 × 106 algae per cm2), and in this instance bleaching was clearly a sudden, isolated, stress event and not an extreme low-point in the seasonal
fluctuation of the density of symbiotic algae. Bleached corals were associated with high levels of partial and whole-colony
mortality, but mortality was exclusively limited to the two Acropora spp. Importantly, most of this mortality was recorded in surveys conducted 1 and 2 weeks after bleaching was first observed,
and for A. latistella as little as 1 week after bleaching was first observed. This suggests that in this particular bleaching event, for the Acropora species, that bleaching and mortality were intimately linked: this in turn suggests it was a pathological phenomenon. The
study highlights a problem in the adaptive bleaching hypothesis, whereby significant levels of mortality can occur in a bleaching
event before any chance for subsequent recombination of the host-symbiont unit. It is argued that in order to further evaluate
the significance of bleaching as a potentially adaptive mechanism, bleaching-induced and bleaching-related mortality have
to be fully considered. It is necessary to incorporate the cost (in terms of mortality) of a bleaching event, the recurring
cost of reverting to the original, mortal, stress–prone combination after the event, and the higher cost associated with forming
a maladaptive combination. 相似文献
3.
Carlos Ruiz Sebastián Kerry J. Sink Timothy R. McClanahan Donald A. Cowan 《Marine Biology》2009,156(10):2049-2062
The high-latitude coral communities of southern Africa suffered minimal impacts during past mass bleaching events. Recent
reports indicate an increase in bleaching frequency during the last decade, yet the actual levels of thermal stress and contributing
factors in these bleaching events, and the degree of acclimatisation or adaptation on these reefs are poorly understood. During
the 2005 warm-water anomaly in the southern Indian Ocean we conducted bleaching surveys and collected samples for genotyping
of the algal symbiont communities at 21 sites in southern Mozambique and South Africa. Coral bleaching reached unprecedented
levels and was negatively correlated with both latitude and water depths. Stylophora pistillata and Montipora were the most susceptible taxa, whereas three common branching corals had significantly different bleaching responses (Stylophora > Acropora > Pocillopora). Temperature records indicated that localised strong upwelling events coupled with persistent above-average seawater temperatures
may result in accumulated thermal stress leading to bleaching. Symbiodinium in 139 scleractinian corals belonged almost exclusively to clade C, with clade D symbionts present in only 3% of the colonies. Two atypical C subclades were present in Stylophora and Pocillopora colonies and these were more abundant in shallow than deeper sites. Taxon-specific differences in bleaching responses were
unrelated to different clades of algal symbionts and suggest that Symbiodinium C subtypes with diverse thermal tolerance, coupled with acclimatisation and morphology of the host colony influence the bleaching
response. Additionally, the predominance of putatively thermal-sensitive Symbiodinium in southern African corals may reflect a limited experience of bleaching and emphasises the vulnerability of these reefs
to moderate levels of thermal stress. 相似文献
4.
Extreme tidal events are one of the most predictable natural disturbances in marine benthic habitats and are important determinants
of zonation patterns in intertidal benthic communities. On coral reefs, spring low tides are recurrent disturbances, but are
rarely reported to cause mass mortality. However, in years when extremely low tides coincide with high noon irradiances, they
have the potential to cause widespread damage. Here, we report on such an event on a fringing coral reef in the central Great
Barrier Reef (Australia) in September 2005. Visual surveys of colony mortality and bleaching status of more than 13,000 corals
at 14 reef sites indicated that most coral taxa at wave-protected sites were severely affected by the event. Between 40 and
75% of colonies in the major coral taxa (Acropora, Porites, Faviidae, Mussidae and Pocilloporidae) were either bleached or suffered partial mortality. In contrast, corals at wave-exposed
sites were largely unaffected (<1% of the corals were bleached), as periodic washing by waves prevented desiccation. Surveys
along a 1–9 m depth gradient indicated that high coral mortality was confined to the tidal zone. However, 20–30% of faviid
colonies were bleached throughout the depth range, suggesting that the increase in benthic irradiances during extreme low
tides caused light stress in deeper water. Analyses of an 8-year dataset of tidal records for the area indicated that the
combination of extended periods of aerial exposure and high irradiances occurs during May–September in most years, but that
the event in September 2005 was the most severe. We argue that extreme low-tide, high-irradiance events are important structuring
forces of intertidal coral reef communities, and can be as damaging as thermal stress events. Importantly, they occur at a
time of year when risks from thermal stress, cyclones and monsoon-associated river run-off are minimal. 相似文献
5.
Bleaching of corals results from the loss of their symbiotic algae (zooxanthellae) and/or pigments. The supply of photoassimilates provided by the zooxanthellae to the coral declines during bleaching and reduces the ability to activate energy-costly processes such as maintenance, growth and reproduction. In the present study we compared the competitive outcomes, expressed as overgrowth and changes in colony sizes of Oculina patagonica (an encrusting Mediterranean stony coral) and the bryozoan Watersipora sp., growing in contact with each other, during and between bleaching events. Year-round observations of tagged colonies showed alternating competitive outcomes: O. patagonica wins over Watersipora sp. between bleaching events, but loses during bleaching events. Using the 14C-point-labeling technique on coral tissue, we examined intra-colonial translocation of photosynthetic products from the point-tissue labeling towards interaction zones. In non-bleached O. patagonica, competition resulted in preferentially oriented translocation of 14C products to the interaction zone located up to 8 cm away from the tissue-labeling site. Sites opposite the interaction zone received significantly less labeled photoassimilates compared to the interaction zone. In bleached colonies (40-85% bleached surface area), such translocation did not occur, probably explaining the failure to compete with the encrusting neighbor Watersipora sp. Our findings demonstrate the importance of colonial integration and resource orientation for the competitive superiority of O. patagonica. 相似文献
6.
The distribution of molluscan assemblages and their postmortem fate on coral reefs in the Gulf of Aqaba (northern Red Sea) 总被引:1,自引:0,他引:1
Molluscan assemblages were studied on fringing reefs (reef flats, Millepora-fringing reefs, fringing reefs with massive corals) and fore-reef hard substrata (coral patches, coral carpets and small
patch reefs) in the Gulf of Aqaba at water depths ranging from the intertidal to 26 m. A total of 1,665 molluscan individuals
from 51 taxa was counted on 44 transects, which covered 220 m2 at eight diving sites. The most important molluscs in the assemblage
were the parasitic gastropod Coralliophila neritoidea, the encrusting gastropod Dendropoma maxima and the coral-associated bivalve Pedum spondyloideum. The dead assemblage, in contrast, was dominated by encrusting bivalves (Ostreoidea, Chamoidea, Spondylidae) and the coral-predating
gastropod Drupella cornus. Distinct molluscan assemblages inhabit each of the three fringing reef-habitats and most of the important depth-related
community changes occurred within the uppermost 5 m. In contrast, the three deeper fore-reef habitats are characterized by
a more uniform molluscan composition. Molluscan assemblages were more dependent on substrata and their coral associations
than on water depth. Comparisons with other published studies indicate that reefoidal hard substrata in the northern Red Sea
are largely characterized by similar species-abundance patterns. The minor differences to other Red Sea studies probably reflect
the northern, isolated position of the Gulf of Aqaba, the lack of certain molluscan habitats, and the differential impact
of anthropogenic influences. Strong differences between living and dead assemblages in Aqaba are similar to those observed
in other regions and are due to distinct biases in the dead assemblage. Molluscs closely associated with living corals (mostly
bivalves and Dendropoma) can easily be overgrown after death and are thus undetectable in visual censuses. Some gastropod taxa are preferentially
transported into surrounding soft-substrata postmortem or redistributed by hermit crabs. Such complex relationships between
ecology and taphonomy are crucial in evaluating the quality of the molluscan fossil record in coral reef environments. The
comparison of our results with literature data documents an increase in coral predators during the last two decades in the
northern Red Sea. Due to the greater mollusc biodiversity in the shallower Aqaba reef habitats, damage to this coral reef
zone would have the greatest impact on the overall mollusc community. 相似文献
7.
Jessica Haapkylä Adrian S. Seymour Orit Barneah Itzchak Brickner Sebastian Hennige David Suggett David Smith 《Marine Biology》2009,156(5):1021-1027
This is the first quantitative study on the prevalence of epizoic Waminoa sp. acoel worms and their association with corals in the Wakatobi Marine National Park (WMNP), South-East Sulawesi, Indonesia.
Three replicate transects were laid on the reef crest, flat and slope at six sites in 2006 and eight sites in 2007. Four of
the sites were common in both years. In total 69 transects were surveyed in 2006, and 87 transects in 2007. A total of 4.8%
of all observed hard corals were associated with acoel worms in 2006 and 2.6% of hard and soft corals in 2007. Acoels were
present on 16 and 21 of the coral taxa studied in 2006 and 2007 respectively. The worms were strongly associated with the
azooxanthellate coral Tubastrea spp. and were rare or absent on the most abundant coral genera Montipora and Porites. The mean number of corals having acoels was highest on reef slopes, whereas acoels were virtually absent on reef flats. Corals
that had a high and a medium cover of worms were more common in 2007 than in 2006. No significant trend in the adaptation
of the zooxanthellae of Waminoa sp. to different depths at different sites was revealed. The impact of the worm on the coral is unknown, but high numbers
may have a shading effect and a negative impact on the coral’s photophysiology. This acoel merits more study of its life cycle,
its photophysiology, and its impact on its host corals.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
Coral bleaching (the loss of symbiotic dinoflagellates from reef-building corals) is most frequently caused by high-light and temperature conditions. We exposed the explants of the hermatypic coral Stylophora pistillata to four combinations of light and temperature in late spring and also in late summer. During mid-summer, two NOAA bleaching warnings were issued for Heron Island reef (Southern Great Barrier Reef, Australia) when sea temperature exceeded the NOAA bleaching threshold, and a ‘mild’ (in terms of the whole coral community) bleaching event occurred, resulting in widespread S. pistillata bleaching and mortality. Symbiotic dinoflagellate biomass decreased by more than half from late spring to late summer (from 2.5×106 to 0.8×106 dinoflagellates cm2 coral tissue), and those dinoflagellates that remained after summer became photoinhibited more readily (dark-adapted F
V : F
M decreased to (0.3 compared with 0.4 in spring), and died in greater numbers (up to 17% dinoflagellate mortality compared with 5% in the spring) when exposed to artificially elevated light and temperature. Adding exogenous antioxidants (d-mannitol and l-ascorbic acid) to the water surrounding the coral had no clear effect on either photoinhibition or symbiont mortality. These data show that light and temperature stress cause mortality of the dinoflagellate symbionts within the coral, and that susceptibility to light and temperature stress is strongly related to coral condition. Photoinhibitory mechanisms are clearly involved, and will increase through a positive feedback mechanism: symbiont loss promotes further symbiont loss as the light microenvironment becomes progressively harsher. 相似文献
9.
We assessed whether published observations of the ecology of encrusting coralline algae (Rhodophyta) from tropical and temperate
coasts could be used to predict patterns and responses on a polar coast where such knowledge does not exist. On subtidal rocky
coasts near Casey, East Antarctica, we detected a strong positive association of understorey encrusting coralline algae with
canopies formed by the endemic alga Himantothallus grandifolius. The experimental removal of H. grandifolius caused corallines to bleach from red to pink/white concomitant with a decline in their photosynthetic activity. The magnitude
of this decline (mean ± SE = 56.85±8.43%) was remarkably similar to that observed on temperate coasts (45.98±5.91%). Positive
effects of nutrient enrichment of the surrounding water, hypothesized to alleviate the negative effects of canopy loss on
encrusting corallines, were not detected. Removing H. grandifolius increased the intensity of photosynthetically active radiation and ultra-violet radiation reaching the substratum by three
orders of magnitude, providing the basis for models invoking enhanced irradiance as the primary cause of the negative effects
of canopy loss. Striking similarities among our results and those from tropical and temperate coasts suggest that responses
of encrusting corallines to loss of canopies may have predictive properties across large distances and environmental gradients
(tropical–temperate–polar). 相似文献
10.
Symbiont specificity and bleaching susceptibility among soft corals in the 1998 Great Barrier Reef mass coral bleaching event 总被引:1,自引:0,他引:1
Considerable variability in bleaching was observed within and among soft coral taxa in the order Alcyonacea (Octocorallia:
Cnidaria) on the central Great Barrier Reef (GBR, latitude 18.2°–19.0°S, longitude 146.4°–147.3°E) during the 1998 mass coral
bleaching event. In April 1998, during a period of high sea surface temperatures, tissue samples were taken from bleached
and unbleached colonies representative of 17 soft coral genera. The genetic identities of intracellular dinoflagellates (Symbiodinium spp.) in these samples were analyzed using PCR-denaturing gradient gel electrophoresis fingerprinting analysis of the internal
transcribed spacer regions 1 and 2. Alcyonaceans from the GBR exhibited a high level of symbiont specificity for Symbiodinium types mostly in clade C. A rare clade D type (D3) was associated only with Clavularia koellikeri, while Nephthea sp. hosted symbionts in clade B (B1n and B36). Homogenous Symbiodinium clade populations were detected in all but one colony. Colonies that appeared bleached possessed symbiont types that were
genetically indistinguishable from those in nonbleached conspecifics. These data suggest that parameters other than the resident
endosymbionts such as host identity and colony acclimatization are important in determining bleaching susceptibility among
soft corals.
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 184-m cargo ship "Bunga Teratai Satu" ran aground on Sudbury Reef, within the Great Barrier Reef Marine Park, on 2 November 2000. Although no cargo or fuel was lost, the ship remained aground for 12 days and a large quantity of antifoulant paint containing tributyltin (TBT), zinc, and copper was scraped from the hull during the grounding and subsequent refloating operation. This resulted in extensive contamination of the reef sediments for up to 250 m surrounding the grounding site. Two laboratory-based experiments assessed the impact of contaminated sediments on the survival of both newly settled corals of Acropora microphthalma and branchlets of A. formosa. Newly settled corals exposed to sediments containing 8.0 mg kg–1 TBT, 72 mg kg–1 Cu, and 92 mg kg–1 Zn or greater suffered significantly higher mortality after 72 h, compared to control or low-concentration treatments. Coral recruits exposed to 40 mg kg–1 TBT (Sn), 306 mg kg–1 Cu, and 403 mg kg–1 Zn were all killed within 38 h. Branchlets from adult corals exposed to sediments with a high concentration of contaminants (TBT 160 mg kg–1, Cu 1,180 mg kg–1, and Zn 1,570 mg kg–1) suffered significant mortality (38%), whereas branchlets placed in treatments with lower levels of contaminants suffered no mortality. Visual bleaching of the branchlets was observed at high contaminant levels, but an overall reduction in the symbiotic zooxanthellae populations was not observed in surviving corals. The photosynthetic yields of light-adapted zooxanthellae remained constant in live branchlets, indicating that the TBT-contaminated sediment may be more toxic to the host than the symbiont. Our results show that antifoulant contamination at ship-grounding sites has the potential to cause major mortality of resident coral communities and can have a negative impact on the recovery of adult populations.Communicated by P.W. Sammarco, Chauvin 相似文献
12.
Sebastian J. Hennige Michael P. McGinley Andréa G. Grottoli Mark E. Warner 《Marine Biology》2011,158(11):2515-2526
It is speculated that differences in coral bleaching susceptibility may be influenced by the genotype of in hospite Symbiodinium and their differential responses to bleaching stressors. Photoinhibition of photosystem II (PSII), damage to the D1 (psbA)
PSII reaction centre protein and production of reactive oxygen species by in hospite Symbiodinium are likely precursors of coral bleaching. In order to assess whether photorepair rates of in hospite Symbiodinium underlie the bleaching susceptibility of their hosts, photoinhibition (net and gross), photoprotection and photorepair rates
were assessed in a bleaching-‘tolerant’ coral (P. astreoides) and a bleaching-‘sensitive’ coral (M. faveolata) using non-invasive fluorometric techniques and by blocking de novo synthesis of psbA. Previous studies using such techniques
have demonstrated that in vitro Symbiodinium types ‘sensitive’ to bleaching stressors had reduced rates of photorepair relative to ‘tolerant’ Symbiodinum types. Our measurements demonstrated that Symbiodinium in the more bleaching tolerant P. astreoides had higher photorepair rates than Symbiodinium in M. faveolata. Higher repair rates in P. astreoides resulted in lower net photoinhibition relative to M. faveolata, where both corals exhibited similar susceptibility to photodamage (gross photoinhibition). Photoprotective mechanisms were
observed in both corals; M. faveolata exhibited higher antennae-bed quenching than P. astreoides at low-light intensities, but at and above light-saturating intensities, which are different for each coral species, P. astreoides displayed more efficient non-photochemical quenching (Stern–Volmer quenching) of chlorophyll fluorescence than M. faveolata. Increased NPQ by P. astreoides at E/E
k ≥ 1 was not driven by antennae-bed quenching. The ability of in hospite Symbiodinium in P. astreoides to mitigate the effects of photoinhibition under high light conditions compared with Symbiodinium in M. faveolata, and their high repair capacity following photoinhibition, may be a key factor to consider in future bleaching studies and
may underlie the relative bleaching tolerance of P. astreoides compared to M. faveolata. 相似文献
13.
Climate change is a major threat to coral reef ecosystems worldwide. A key determinant of the fate of reef corals in a warming
climate is their capacity to tolerate increasing thermal stress. Here, an increase in thermal tolerance is demonstrated for
three major coral genera (Acropora, Pocillopora and Porites) following the extensive mass bleaching event that occurred on the Great Barrier Reef (Australia) in 1998. During the subsequent
and more severe thermal stress event in 2002, bleaching severity was 30–100% lower than predicted from the relationship between
severity and thermal stress in 1998, despite higher solar irradiances during the 2002 thermal event. Coral genera most susceptible
to thermal stress (Pocillopora and Acropora) showed the greatest increase in tolerance. Although bleaching was severe in 1998, whole-colony mortality was low at most
study sites. Therefore, observed increases in thermal tolerance cannot be explained by selective mortality alone, suggesting
a capacity for acclimatization or adaptation. Although the vulnerability of coral reefs remains largely dependent on the rate
and extent of climate change, such increase in thermal tolerance may delay the onset of mass coral mortalities in time for
the implementation of low-emission scenarios and effective management. 相似文献
14.
Distribution of deep-water gorgonian corals in relation to benthic habitat features in the Northeast Channel (Atlantic Canada) 总被引:2,自引:0,他引:2
The distribution and abundance of deep-water gorgonian corals were investigated along 52 transects at 183–498 m depth in the Northeast Channel, between Georges Bank and Browns Bank in the northwest Atlantic, using a remotely operated vehicle and a towed video-camera system. Three species (Paragorgia arborea, Primnoa resedaeformis, and Acanthogorgia armata) were observed. Primnoa occurred on 35 transects below 196 m depth, with highest local abundance in stands of 104 colonies per 100 m2. Paragorgia was present on 21 transects deeper than 235 m, with highest local abundance of 49 colonies per 100 m2. Acanthogorgia was observed at only four transects between 231 m and 364 m, with a local maximum abundance of 199 colonies per 100 m2. The maximum abundance averaged for whole transects was 19.2 and 6.2 colonies per 100 m2 for Primnoa and Paragorgia, respectively. The corals were more common in the outer part of the channel along the shelf break and slope than on the shelf in the inner part. All three species showed a patchy distribution with no signs of competitive exclusion at any spatial scale. Transects with high abundance of corals were characterised by depths greater than 400 m, maximum temperatures less than 9.2°C, and a relatively high percentage coverage of cobble and boulder (more than 19% and 6%, respectively). High temperatures probably control the upper depth limit of the corals, and Primnoa seems to tolerate slightly higher temperatures than Paragorgia. Abundance of both species was negatively correlated with average temperature and positively with cobbles. Together, temperature, percentage cobble and salinity accounted for 38% of the variance of Primnoa. The comparable figure for Paragorgia was 15%. The observed distribution indicated that the abundance of coral is controlled by additional factors such as larger-scaled topographic features governing the current regimes and thus also the supply of food and larvae.Communicated by R. J. Thompson, St. Johns 相似文献
15.
Nayuta Yamashita Kathryn E. Stoner Pablo Riba-Hernández Nathaniel J. Dominy Peter W. Lucas 《Behavioral ecology and sociobiology》2005,58(6):618-629
The intensity of available light is important in determining how well a diurnal animal can distinguish color. Primates with different types of color vision may exhibit behaviors that maximize visual contrast during critical activities such as feeding. We hypothesized that (1) trichromatic taxa will feed in a wide range of light conditions because color constancy permits stabilized color appearance across changes in illumination, and (2) that taxa with a high proportion of dichromatic individuals will tend to feed at higher light levels to increase color contrast. We recorded light levels during feeding bouts of seven primate taxa with varying degrees of color vision: the dichromatic Lemur catta, two polymorphic species, Propithecus v. verreauxi and Ateles geoffroyi, and the routine trichromats, Alouatta palliata, Colobus guereza, Piliocolobus badius, and Cercopithecus ascanius. Results were equivocal for our hypotheses. While routinely trichromatic taxa used varying light levels, the pattern of results did not differ from the dichromatic Lemur catta. However, polymorphic taxa not only sought the highest light, but females, which are the only individuals in polymorphic taxa that can be trichromatic, fed in higher light levels than males when eating non-green foods. This result is consistent with selection operating to maintain a balanced polymorphism in these taxa, though the connection between light levels and color vision type for the females is unclear. Our results further suggest that trichromatic vision may afford a selective advantage because it permits foraging under a greater range of light levels. 相似文献
16.
Dynamics of a coral reef community at Tiao-Shi Reef, southern Taiwan were studied using permanent transects to examine coral
recovery and successive cascades to collapse stage resulting from chronic anthropogenic impacts and typhoons. Three distinct
zones were recognized within a relatively small study area (250 m across) formerly dominated by large stands of branching
Acropora corals. The first zone still retains the dominance of branching Acropora corals, although they show a significant decreasing tendency. The second zone exhibits recovery with a significant increase
in branching Montipora stellata, which is recruited and grows faster than branching Acropora corals. The third zone is occupied by anemone, Condylactis sp., and demonstrates a stable phase of coral deterioration without recovery. Such differences in coral reef community dynamics
within a small spatial scale illustrate mosaic dynamics which have resulted from degradation of the water quality, patchy
mortality of large branching Acropora thickets caused by typhoons, the rapid asexual fragmentation and growth of M. stellata making it a successful colonizer, and occupation by anemone, Condylactis sp., together with unstable remnants of dead Acropora rubbles have not allowed coral recruits to survive. 相似文献
17.
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
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.
Three common species of Hawaiian reef corals, Pocillopora damicornis (L.), Montipora verrucosa (Lamarck) and Fungia scutaria Lamarck, were grown in a temperature-regulated, continuous-flow sea water system. The skeletal growth optimum occurred near 26°C, coinciding with the natural summer ambient temperature in Hawaii, and was lowest at 21° to 22°C, representing Hawaiian winter ambient. Levels of approximately 32°C produced mortality within days. Prolonged exposure to temperatures of approximately 30°C eventually caused loss of photosynthetic pigment, increased mortality, and reduced calcification. Corals lived only 1 to 2 weeks at 18°C. The corals showed greater initial resistance at the lower lethal limit, but ultimately low temperature was more deleterious than high temperature. Results suggest that a decrease in the natural water temperature of Hawaiian reefs would be more harmful to corals than a temperature increase of the same magnitude.Contribution No. 504 of the Hawaii Institute of Marine Biology. 相似文献
20.
Loss of zooxanthellae (dinoflagellate Symbiodinium) from corals will sometimes lead to mass mortality of corals. To detect and quantify Symbiodinium released from corals, we developed a zooxanthellae “trap” and a quantitative PCR (qPCR) system with Symbiodinium clades A–F-specific primer sets. The trap was attached to a branch or the surface of several wild stony corals, and the water
samples within the traps, including released Symbiodinium, were subjected to qPCR. All tested corals released clade C Symbiodinium at estimates of ~5,900 cells h−1 cm−2 of coral surface. Although all tested Pocillopora eydouxi harboured both clades C and D, some of these colonies released only clade C or released a lesser amount of clade D than that
in the tissues. Our Symbiodinium quantification system revealed that wild hermatypic corals constantly release Symbiodinium to the environment. Our result suggests that some corals may discharge certain clades of Symbiodinium alternatively. 相似文献