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1.
The zooxanthellate octocoral Sinularia flexibilis is a producer of potential pharmaceutically important metabolites such as antimicrobial and cytotoxic substances. Controlled
rearing of the coral, as an alternative for commercial exploitation of these compounds, requires the study of species-specific
growth requirements. In this study, phototrophic vs. heterotrophic daily energy demands of S. flexibilis was investigated through light and Artemia feeding trials in the laboratory. Rate of photosynthetic oxygen by zooxanthellae in light (≈200 μmol quanta m−2 s−1) was measured for the coral colonies with and without feeding on Artemia nauplii. Respiratory oxygen was measured in the dark, again with and without Artemia nauplii. Photosynthesis–irradiance curve at light intensities of 0, 50, 100, 200, and 400 μmol quanta m−2 s−1 showed an increase in photosynthetic oxygen production up to a light intensity between 100 and 200 μmol quanta m−2 s−1. The photosynthesis to respiration ratio (P/R > 1) confirmed phototrophy of S. flexibilis. Both fed and non-fed colonies in the light showed high carbon contribution by zooxanthellae to animal (host) respiration
values of 111–127%. Carbon energy equivalents allocated to the coral growth averaged 6–12% of total photosynthesis energy
(mg C g
−
1 buoyant weight day
−
1) and about 0.02% of the total daily radiant energy. “Light utilization efficiency (ε)” estimated an average ε value of 75%
12 h
−
1 for coral practical energetics. This study shows that besides a fundamental role of phototrophy vs. heterotrophy in daily
energy budget of S. flexibilis, an efficient fraction of irradiance is converted to useable energy. 相似文献
2.
Margarita Elena Rentería-Cano Laura Sánchez-Velasco Evgueni Shumilin Miguel F. Lavín Jaime Gómez-Gutiérrez 《Biological trace element research》2011,142(3):848-864
We report the distribution of major and trace element concentrations in epipelagic zooplankton collected in the Northern Gulf
of California in August 2003. The Bray–Curtis index defined three element assemblages in zooplankton: (1) major metals, which
included only two elements, Na (3.6–17.0%) and Ca (1.0–4.8%). Na had its highest concentrations in the shallow tidally mixed
Upper Gulf, where high salinity, temperature, and zooplankton biomass (dominated by copepods) prevailed. Ca showed its highest
concentrations south of Ballenas Channel, characterized by tidal mixing and convergence-induced upwelling, indicated by low
sea-surface temperature, salinity, and zooplankton biomass; (2) Six biological essential elements, like Fe (80–9,100 mg kg−1) and Zn (20–2,570 mg kg−1), were detected in high concentrations in zooplankton collected near Guaymas Basin, which had high surface temperature and
chlorophyll a concentrations. (3) Metals of terrigenous origin, such as Sc (0.01–1.4 mg kg−1) and Th (0.03–2.3 mg kg−1), and redox-sensitive metals, like Co (3–23.8 mg kg−1); this was the assemblage with the largest number of elements (15). Both types of elements of assemblage 3 had maximum concentrations
in the cyclonic eddy that dominates the summer circulation in the Northern region. We concluded that sediment resuspension
by tidal mixing in the Upper Gulf, upwelling south of Ballenas Channel, and the cyclonic eddy were key oceanographic features
that affected the element concentrations of epipelagic zooplankton in the Northern Gulf of California. Oceanographic mechanisms
such as these may contribute to element incorporation in marine organisms in other seas. 相似文献
3.
M. S. Naumann A. Haas U. Struck C. Mayr M. el-Zibdah C. Wild 《Coral reefs (Online)》2010,29(3):649-659
Particulate organic matter (POM) and dissolved organic carbon (DOC) release by six dominant hermatypic coral genera (Acropora, Fungia, Goniastrea, Millepora, Pocillopora and Stylophora) were measured under undisturbed conditions by laboratory incubations during four seasonal expeditions to the Northern Red
Sea. In addition, the influence of environmental factors (water temperature, light availability and ambient inorganic nutrient
concentrations) was evaluated. Particulate organic carbon (POC) and particulate nitrogen (PN) release were always detectable
and genus-specific, with Stylophora releasing most POM (6.5 mg POC and 0.5 mg PN m−2 coral surface area h−1) during all seasons. The fire coral Millepora released significantly less POM (0.3 mg POC and 0.04 mg PN m−2 coral surface area h−1) than all investigated anthozoan genera. The average POC:PN ratio of POM released by all coral genera was 12 ± 1, indicating
high carbon/low nitrogen content of coral-derived organic matter. POM release showed little seasonal variation, but average
values of POC and PN release rates correlated with water temperature, light availability and ambient nitrate concentrations.
DOC net release and elevated DOC:POC ratios were detectable for Acropora, Goniastrea and Millepora, revealing maximum values for Acropora (30.7 mg DOC m−2 coral surface area h−1), whilst predominant DOC uptake was observed for Pocillopora, Fungia and Stylophora. Depth-mediated light availability influenced DOC fluxes of Acropora and Fungia, while fluctuations in water temperature and ambient inorganic nutrient concentrations showed no correlation. These comprehensive
data provide an important basis for the understanding of coral reef organic matter dynamics and relevant environmental factors. 相似文献
4.
This study describes relatively high recruitment of Montastraea annularis complex (hereafter, MAC) on the shallow reefs (≤9 m depth) along 4 km of the south coast of St. John that have been censused
for 16 years. Before 2008, the density of juvenile MAC along this stretch of coast was <0.068 colonies m−2 (and often <0.032 colonies m−2), but in 2008 it increased to 0.152 colonies m−2 and remained at 0.116 colonies m−2 in 2009. These densities were driven by only 7–9 colonies year−1, but against the long-term context of weak recruitment and declining cover of this taxon, the densities are notable. In 2009,
the spatial extent of the surveys was expanded to 47 km, along the north, east, and south coasts of St. John. This larger
effort demonstrated that MAC recruitment was localized to the initial 4 km surveyed; outside this area, the mean density was
0.010 juvenile colonies m−2. These results demonstrate that MAC is still capable of recruitment at rates similar to those of the 1970s, but the highly
limited spatio-temporal extent of the effect is unlikely to appreciably alter the declining population trajectories of this
taxon. 相似文献
5.
Interactions between predators and prey organisms are of fundamental importance to ecological communities. While the ecological
impact that grazing predators can have in terrestrial and temperate marine systems are well established, the importance of
coral grazers on tropical reefs has rarely been considered. In this study, we estimate the biomass of coral tissue consumed
by four prominent species of corallivorous butterflyfishes. Sub-adult butterflyfishes (60–70 mm, 6–11 g) remove between 0.6
and 0.9 g of live coral tissue per day, while larger adults (>110 mm, ~40–50 g) remove between 1.5 and 3 g of coral tissue
each day. These individual consumption rates correspond to the population of coral-feeding butterflyfishes at three exposed
reef crest habitats at Lizard Island, Great Barrier Reef, consuming between 14.6 g (±2.0) and 19.6 g (±3.9) .200 m−2 day−1 of coral tissue. When standardised to the biomass of butterflyfishes present, a combined reefwide removal rate of 4.2 g (±1.2)
of coral tissue is consumed per 200 m−2 kg−1 of coral-feeding butterflyfishes. The quantity of coral tissue removed by these predators is considerably larger than previously
expected and indicates that coral grazers are likely to play an important role in the transfer of energy fixed by corals to
higher consumers. Chronic coral consumption by butterflyfishes is expected to exact a large energetic cost upon prey corals
and contribute to an increased rate of coral loss on reefs already threatened by anthropogenic pressure and ongoing climate
change. 相似文献
6.
Mohammad K. Khalesi H. H. Beeftink R. H. Wijffels 《Marine biotechnology (New York, N.Y.)》2009,11(4):488-494
The branching zooxanthellate soft coral Sinularia flexibillis releases antimicrobial and toxic compounds with potential pharmaceutical importance. As photosynthesis by the symbiotic algae
is vital to the host, the light-dependency of the coral, including its specific growth rate (μ day−1) and the physiological response to a range of light intensities (10–1,000 μmol quanta m−2 s−1) was studied for 12 weeks. Although a range of irradiances from 100 to 400 μmol quanta m−2 s−1 was favorable for S. flexibilis, based on chlorophyll content, a light intensity around 100 μmol quanta m−2 s−1 was found to be optimal. The contents of both zooxanthellae and chlorophyll a were highest at 100 μmol quanta m−2 s−1. The specific budding rate showed almost the same pattern as the specific growth rate. The concentration of the terpene flexibilide,
produced by this species, increased at high light intensities (200–600 μmol quanta m−2 s−1). 相似文献
7.
Chlorophyll-a (chl-a) and carotenoid pigments of the zooxanthellate octocoral Sinularia flexibilis were analyzed using high performance liquid chromatography following exposure to three light intensities for over 30 days.
From the coral fragments located at different light intensities, a total carotenoid of >41 μg g−1 dry weight, including peridinin, xanthophylls (likely diadinoxanthin + diatoxanthin), and chl-a as the most abundant pigments, with minor contents of astaxantin and β-carotene were detected. The whole content of chl-a weighed 5 μg g−1 dry weight in all coral colonies. Chl-a and carotenoids contributed 11.2% and 88.2%, respectively, to all pigments detected, and together accounted for 99.4% of
the total pigments present. The highest contents of carotenoids and chl-a was observed in the coral grafts placed in an irradiance of 100 μmol quanta m−2 s−1; they showed lower ratios of total carotenoids: chl-a compared to those exposed to 400 μmol quanta m−2 s−1 after >30 days of incubation. The ratios of peridinin and xanthophylls with respect to chl-a from the colonies at 400 μmol quanta m−2 s−1 were approximately double those observed at irradiances of 100 and 200 μmol quanta m−2 s−1. Partial quantification of pigments in this study showed that the carotenoids of S. flexibilis showed a decrease at irradiances above 100 μmol quanta m−2 s−1, with the exception of an increase in β-carotene at 200 μmol quanta m−2 s−1. 相似文献
8.
The effects of nutrient enrichment on the release of dissolved organic carbon and nitrogen (DOC and DON, respectively) from
the coral Montipora digitata were investigated in the laboratory. Nitrate (NO3
−) and phosphate (PO4
3−) were supplied to the aquarium to get the final concentrations of 10 and 0.5 μmol l−1, respectively, and the corals were incubated for 8 days. The release rate of DON per unit coral surface area significantly
decreased after the nutrient enrichment, while the release rate of DOC was constant. Because the chlorophyll a (chl a) content of zooxanthellae per unit surface area increased, the release rate of DOC significantly decreased when normalized
to unit chl a. These results suggested that the incorporation of NO3
− and PO4
3− stimulated the synthesis of new cellular components in the coral colonies and consequently, reduced extracellular release
of DOC and DON. Actually, significant increase in N and P contents relative to C content was observed in the coral’s tissue
after the nutrient enrichment. The present study has concluded that inorganic nutrient enrichment not only affects coral-algal
metabolism inside the colony but also affects a microbial community around the coral because the organic matter released from
corals functions as energy carrier in the coral reef ecosystem. 相似文献
9.
Satoshi Suzuki Kazushige Furuya Tadashi Kawai Ichiro Takeuchi 《Journal of applied phycology》2008,20(5):833-844
Recent studies on global climate change report that increase in seawater temperature leads to coastal ecosystem change, including
coral bleaching in the tropic. In order to assess the effect of increased seawater temperature on a temperate coastal ecosystem,
we studied the inter-annual variation in productivity of Laminaria japonica using long-term oceanographic observations for the Uwa Sea, southern Japan. The annual productivity estimates for L. japonica were 2.7 ± 2.5 (mean ± SD) kg wet wt. m−1 (length of rope) (2003/2004), 1.0 ± 0.6 kg wet wt. m−1 (2004/2005) and 12.1 ± 12.5 kg wet wt. m−1 (2005/2006). Our previous study using the same methodology at the same locality reported that the productivity was estimated
for the 2001/2002 (33.3 ± 15.2 kg wet wt. m−1) and 2002/2003 (34.0 ± 8.7 kg wet wt. m−1) seasons. Productivity in 2003/2004 and 2004/2005 was significantly lower than in years 2001/2002, 2002/2003 and 2005/2006.
A comparison of oceanographic conditions among the 5 years revealed the presence of threshold seawater temperature effects.
When the average seawater temperature during the first 45 days of each experiment exceeded 15.5°C, productivity was reduced
to about 10 % of that in cooler years. Moreover the analysis of growth and erosion rates indicates that when the seawater
temperature was over 17.5°C, erosion rate exceeded growth rate. Thus, an increase of seawater temperature of just 1°C during
winter drastically reduces the productivity of L. japonica in the Uwa Sea. 相似文献
10.
Understanding environmental drivers of black band disease (BBD), a virulent disease affecting corals worldwide, is critical
to managing coral populations. Field monitoring studies have implicated seasonally elevated temperature and light as drivers
of annual BBD outbreaks on the Great Barrier Reef, but do not distinguish their relative impacts. Here, we compare progression
of BBD lesions on Montipora hispida among three controlled temperature (28.0, 29.0, 30.5°C) and two controlled light treatments (170, 440 μmol m−2 s−1) within normal seasonal ranges at the site. BBD progression rates were greatest (5.2 mm d−1) in the 30.5°C/high-light treatment and least (3.2 mm d−1) in the 28°C/low-light treatment. High light significantly enhanced BBD progression, whereas increases in disease progression
under high temperatures were not statistically significant, identifying the greater role of light in driving BBD dynamics
within the temperature range examined. Greater BBD progression during daytime compared with nighttime (by 2.2–3.6-fold across
temperature and light treatments) corroborates our conclusion that light is the pre-eminent factor driving BBD progression
at typical summer temperatures. Decreased photochemical efficiency of algal endosymbionts in the high-temperature/high-light
treatments suggests that compromised health of the coral holobiont contributes to enhanced disease progression, highlighting
the complexity of disease dynamics in host–pathogen systems responding to environmental changes. 相似文献
11.
V. S. Kuwahara R. Nakajima B. H. R. Othman M. R. M. Kushairi T. Toda 《Coral reefs (Online)》2010,29(3):693-704
Biologically diverse coral-reef ecosystems are both directly and indirectly susceptible to changes in the spectral ultraviolet
radiation (UVR) distribution. The purpose of this study was to (1) measure the variability of UVR and photosynthetically active
radiation (PAR) penetration in the water above coral reefs around the Malaysian peninsula, (2) measure the variability and
distribution of UVR-specific biogeochemical factors, and (3) determine the impact of biogeochemical variability as it affects
the UVR:PAR ratio. Downwelling UVR and PAR irradiance and bio-optically derived biogeochemical factors were measured at 14
coral survey stations around the Malaysian peninsula from August 10–29, 2007. The West Coast was characterized by relatively
shallow mean 10% UV-B (320 nm) penetration (1.68 ± 1.12 m), high chlorophyll (3.00 ± 4.72 μg l−1), high chromophoric dissolved organic matter (CDOM; 6.61 ± 3.31 ppb), high particulate organic carbon (POC; 190.65 ± 97.99 mg m−3), and low dissolved organic carbon (DOC; 1.34 ± 0.65 mg m−3). By contrast, the East Coast was characterized by relatively deep mean 10% UV-B penetration (5.03 ± 2.19 m), low chlorophyll
(0.34 ± 0.22 μg l−1), low CDOM (1.45 ± 0.44 ppb), low POC (103.21 ± 37.93 mg m−3), and relatively high DOC (1.91 ± 1.03 mg m−3). The UVR:PAR ratio was relatively higher on the East Coast relative to the West Coast, suggesting variable concentrations
of UVR-specific absorbing components. At all sites, UVR attenuation coefficients showed significant correlations with CDOM,
but were spatially dependent with regard to chlorophyll a, POC, and DOC. The results suggest that bio-optically significant CDOM and DOC factors are uncoupled in coral-reef communities
of Malaysia. Furthermore, the results support prior studies that show chromophorically active concentrations of DOM and POC
are significantly altering the amount of UVR penetration above coral reefs and may be notable factors in regulating intricate
biogeochemical cycles around benthic coral communities in Malaysia. 相似文献
12.
The abundance of lesions from fish bites on corals was quantified at nine shallow reefs in the main Hawaiian Islands. There
were on average 117 bite scars m−2 on Pocillopora meandrina tissue from the barred filefish Cantherhines dumerilii, 69 bites m−2 on Porites compressa tissue, and 4 bites m−2 on Porites lobata tissue from the spotted puffer Arothron meleagris. Across sites, the frequency of A. meleagris bites on P. compressa per unit area of living coral cover declined exponentially with increasing coral cover. P. compressa nubbins in two size classes (1–2 cm and 4–5 cm) were transplanted onto six study reefs. Nubbins in the small size class were
entirely removed by bites from A. meleagris, while nubbins ≥4 cm were only partially consumed, leaving them able to recover. At sites with abundant P. compressa, predation had little effect on transplanted nubbins; at sites where P. compressa comprised less than 5% of living cover, all nubbins were preyed upon. A. meleagris bite lesions on P. compressa were monitored through time and fully recovered in 42 ± 4 days. A model of the risk of over-predation (a second predation
event before the first is healed) decreased exponentially with increasing coral cover and increased linearly with increasing
lesion healing time. The increased risk of over-predation at low coral cover could indicate an Allee effect limiting the recovery
of coral populations if coral cover is substantially reduced by natural or anthropogenic disturbances. 相似文献
13.
R. P. Stone 《Coral reefs (Online)》2006,25(2):229-238
The first in situ exploration of Aleutian Island coral habitat was completed in 2002 to determine the distribution of corals, to examine fine-scale associations between targeted fish species and corals, and to investigate the interaction between the areas’ diverse fisheries and coral habitat. Corals, mostly gorgonians and hydrocorals, were present on all 25 seafloor transects and at depths between 27 and 363 m, but were most abundant between 100 and 200 m depth. Mean coral abundance (1.23 colonies m−2) far exceeded that reported for other high-latitude ecosystems and high-density coral gardens (3.85 colonies m−2) were observed at seven locations. Slope and offshore pinnacle habitats characterized by exposed bedrock, boulders, and cobbles generally supported the highest abundances of coral and fish. Overall, 85% of the economically important fish species observed on transects were associated with corals and other emergent epifauna. Disturbance to the seafloor from bottom-contact fishing gear was evident on 88% of the transects, and approximately 39% of the total area of the seafloor observed had been disturbed. Since cold-water corals appear to be a ubiquitous feature of seafloor habitats in the Aleutian Islands, fisheries managers face clear challenges integrating coral conservation into an ecosystem approach to fisheries management. 相似文献
14.
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
15.
Acid-sensitive outwardly rectifying anion channels (ASOR) have been described in several mammalian cell types. The present
whole-cell patch-clamp study elucidated whether those channels are expressed in erythrocytes. To this end whole-cell recordings
were made in human erythrocytes from healthy donors treated with low pH and high osmotic pressure. When the pipette solution
had a reduced Cl− concentration, treatment of the cells with Cl−-containing normal and hyperosmotic (addition of sucrose and polyethelene glycol 1000 [PEG-1000] to the Ringer) media with
low pH significantly increased the conductance of the cells at positive voltages. Channel activity was highest in the PEG-1000
media (95 and 300 mM PEG-1000, pH 4.5 and 4.3, respectively) where the current–voltage curves demonstrated strong outward
rectification and reversed at −40 mV. Substitution of the Cl−-containing medium with Cl−-free medium resulted in a decrease of the conductance at hyperpolarizing voltages, a shift in reversal potential (to 0 mV) and loss of outward rectification. The chloride currents were inhibited by chloride channels blockers DIDS and NPPB (IC50 for both was ~1 mM) but not with niflumic acid and amiloride. The observations reveal expression of ASOR in erythrocytes. 相似文献
16.
Tolerance of environmental variables differs between corals and their dinoflagellate symbionts (Symbiodinium spp.), controlling the holobiont’s (host and symbiont combined) resilience to environmental stress. However, the ecological
role that environmental variables play in holobiont distribution remains poorly understood. We compared the drivers of symbiont
and coral species distributions at Palmyra Atoll, a location with a range of reef environments from low to high sediment concentrations
(1–52 g dry weight m−2 day−1). We observed uniform holobiont partnerships across the atoll (e.g. Montipora spp. with Symbiodinium type C15 at all sites). Multivariate analysis revealed that field-based estimates of settling sediment predominantly explained
the spatial variation of coral species among sites (P < 0.01). However, none of the environmental variables measured (sedimentation, temperature, chlorophyll concentration, salinity)
affected symbiont distribution. The discord between environmental variables and symbiont distributions suggests that the symbionts
are physiologically tolerant of the variable environmental regime across this location and that the distribution of different
host–symbiont combinations present is largely dependent on coral rather than Symbiodinium physiology. The data highlight the importance of host tolerance to environmental stressors, which should be considered simultaneously
with symbiont sensitivity when considering the impact of variations in environmental conditions on coral communities. 相似文献
17.
Motomi Genkai-Kato Miyuki Onishi Hideyuki Doi Kentaro Nozaki Kenji Yoshino Hitoshi Miyasaka Koji Omori 《Ecological Research》2008,23(6):1025-1032
We investigated the photosynthesis–light intensity (P–I) relationships of phytoplankton collected from a sublittoral sand
bank in the Seto Inland Sea, Japan, under different temperature conditions. In spite of low chlorophyll a concentration (<3 mg m−3), phytoplankton had considerably high photosynthetic potential (>10 mg C (mg chl a)−1 h−1) in the study area. Based on the P–I relationships, we conducted numerical simulation of areal primary production using published
data on water temperature, chlorophyll a concentration, and irradiance. The areal primary production ranged between 159 and 187 g C m−2 year−1. This production was within the range of typical values reported previously in deeper areas of the Seto Inland Sea. The productivity
in the sand bank area was discussed in relation to water current, allochthonous resource input, and fisheries. 相似文献
18.
Lamia Trabelsi Hatem Ben Ouada Hassen Bacha Mohamed Ghoul 《Journal of applied phycology》2009,21(4):405-412
The effects of light intensity and temperature on Arthrospira platensis growth and production of extracellular polymeric substances (EPS) in batch culture were evaluated using a three-level, full-factorial
design and response surface methodology. Three levels were tested for each parameter (temperature: 30, 35, 40°C; light intensity:
50, 115, 180 μmol photons m−2 s−1). Both growth and EPS production are influenced mainly by the temperature factor but the interaction term temperature*light
intensity also had a significant effect. In addition, conditions optimising EPS production are different from those optimising
growth. The highest growth rate (0.414 ± 0.003 day−1) was found at the lowest temperature (30°C) and highest light intensity (180 μmol photons m−2 s−1) tested, no optima were detectable within the given test range. Obviously, optima for growth must be at a temperature lower
than 30°C and a light intensity higher than 180 μmol photons m−2 s−1. For EPS production, light intensity had a positive linear effect (optimum obviously higher than 180 μmol photons m−2 s−1), but for the temperature parameter a maximum effect was detectable at 35°C. 相似文献
19.
Visual censuses of coral reef fishes in Nha Trang Bay Marine Protected Area (MPA) were conducted during September–October
2005. Nha Trang Bay MPA is relatively rich in reef fishes compared to other areas in Vietnam and the Pacific Ocean outside
the ‘Coral Triangle,’ consistent with its biogeographic location in the western South China Sea. A total of 266 species of
40 families of coral reef fishes formed five distinct assemblages. Spatial variations in distribution and structure of the
assemblages were associated with eight significant biological and physical variables which were cover of living hard corals,
encrusting corals, branching corals, Acropora, Millepora, Montipora, depth and distance from the coast of the mainland. The six factors in front are likely related to provision of shelter and
nutrition, while the distance factor is likely to represent a gradient in disturbance and impacts from various mainland sources
including sedimentation and pollution discharge from nearby rivers. Local species richness ranged from 35 to 70 species 500 m−2 (mean: 51 ± 2 SE) for reef flat stations and from 23 to 68 species 500 m−2 (mean: 48 ± 4 SE) for reef slope stations. Total species richness at each site averaged 76 species (±4 SE), ranging from
56 to 110 species, dominated by wrasses, damselfishes, butterflyfishes, parrotfishes, surgeonfishes, groupers and goatfishes.
Density of total fishes at each station ranged from 348 to 1,444 individuals 500 m−2 (mean: 722 ± 302 SE) for the reef flat stations and from 252 to 929 individuals 500 m−2 (mean: 536 ± 215.7 SE) for the reef slope stations. Overall mean density at each site averaged 628.9 (±238.4 SE) individuals
500 m−2. The highly protected sites supported higher mean density of fishes per site (ranged: 904.5–1,213 individuals 500 m−2 for Hon Mun and 1,167.5 individuals 500 m−2 for Hon Cau) compared to other sites (<800 individuals 500 m−2). Of the families included in the census, densities were dominated throughout the MPA by damselfishes and wrasses. Many target
species, particularly groupers, snappers and emperors, were rare or absent and the low abundance of big fishes was consistent
with over-harvesting. Similarly a low density of butterfly fishes and angelfishes is likely related to the supply for marine
aquaria in Vietnam and overseas. This study provides an important baseline against which the success of present and future
MPA management initiatives may be assessed. 相似文献
20.
Permafrost soils are a significant global store of carbon (C) with the potential to become a large C source to the atmosphere.
Climate change is causing permafrost to thaw, which can affect primary production and decomposition, therefore affecting ecosystem
C balance. To understand future responses of permafrost soils to climate change, we inventoried current soil C stocks, investigated
∆14C, C:N, δ13C, and δ15N depth profiles, modeled soil C accumulation rates, and calculated decadal net ecosystem production (NEP) in subarctic tundra
soils undergoing minimal, moderate, and extensive permafrost thaw near Eight Mile Lake (EML) in Healy, Alaska. We modeled
decadal and millennial soil C inputs, decomposition constants, and C accumulation rates by plotting cumulative C inventories
against C ages based on radiocarbon dating of surface and deep soils, respectively. Soil C stocks at EML were substantial,
over 50 kg C m−2 in the top meter, and did not differ much among sites. Carbon to nitrogen ratio, δ13C, and δ15N depth profiles indicated most of the decomposition occurred within the organic soil horizon and practically ceased in deeper,
frozen horizons. The average C accumulation rate for EML surface soils was 25.8 g C m−2 y−1 and the rate for the deep soil accumulation was 2.3 g C m−2 y−1, indicating these systems have been C sinks throughout the Holocene. Decadal net ecosystem production averaged 14.4 g C m−2 y−1. However, the shape of decadal C accumulation curves, combined with recent annual NEP measurements, indicates soil C accumulation
has halted and the ecosystem may be becoming a C source. Thus, the net impact of climate warming on tundra ecosystem C balance
includes not only becoming a C source but also the loss of C uptake capacity these systems have provided over the past ten
thousand years. 相似文献