Interspecies and spatial diversity in the symbiotic zooxanthellae density in corals from northern South China Sea and its relationship to coral reef bleaching

Coral reef bleaching is usually characterized by expulsion of symbiotic zooxanthellae, loss of zooxanthellae pigmentation, or both. We collected 128 samples comprising 39 species of 21 genera of reef-building corals from Luhuitou and Xiaodonghai in Sanya of Hainan Island and Daya Bay of Guangdong Province, respectively, and analyzed the symbiotic zooxanthellae population density. The results show that： （1） the symbiotic zooxanthella density varies from 0.67×10^6 to 8.48×10^6 cell/cm^2, displaying significant interspecies variability, with branch corals usually having relatively less zooxanthellae （ranging from 0.67×10^6 to 2.47×10^6 cell/cm^2） than massive species （from 1.0×10^6 to 8.48×10^6 cell/cm^2）; （2） corals inhabiting within 4 m water depth have higher levels of symbiotic zooxanthellae than those living at the bottom （-7 m depth） of the reef area; （3） there is no discernable difference in the zooxanthellae density between corals from relatively high latitude Daya Bay （-22°N） and those from relatively low latitude Sanya （-18°N） at comparable sea surface temperatures （SST）; （4） in partially-bleached corals, the density of zooxanthellae shows the following order： healthy-looking part〉 semi-bleached part 〉 bleached part. Based on the above results, we suggest that （1） the zooxanthellae density difference between branching and massive coral species is the main cause that branching corals are more vulnerable to bleaching than massive corals. For example, symbiotic zooxanthellae levels are low in branching Acropora and Pocillopora corals and thus these corals are more susceptible to bleaching and mortality; （2） symbiotic zooxanthellae density can also be affected by environmental conditions, such as sediment loads, diving-related turbidity, and aquaculture-related nitrate and phosphate input, and their increase may reduce symbiotic zooxanthellae density in corals.     

Effects of temperature,hypoxia, ammonia and nitrate on the bleaching among three coral species

Coral bleaching, which is defined as the loss of colour in corals due to the loss of their symbiotic algae (commonly called zooxanthellae) or pigments or both, is occurring globally at increasing rates, and its harm becomes more and more serious during these two decades. The significance of these bleaching events to the health of coral reef ecosystems is extreme, as bleached corals exhibited high mortality, reduced fecundity and productivity and increased susceptibility to diseases. This decreased coral fitness is easily to lead to reef degradation and ultimately to the breakdown of the coral reef ecosystems. Recently, the reasons leading to coral bleaching are thought to be as follows: too high or too low temperature, excess ultraviolet exposure, heavy metal pollution, cyanide poison and seasonal cycle. To date there has been little knowledge of whether mariculture can result in coral bleaching and which substance has the worst effect on corals. And no research was conducted on the effect of hypoxia on corals. To address these questions, effects of tem- perature, hypoxia, ammonia and nitrate on bleaching of three coral species were studied through examination of morphology and the measurement of the number of symbiotic algae of three coral species Acropora nobilis, Palythoa sp. and Alveopora verrilliana. Results showed that increase in temperature and decrease in dissolved oxygen could lead to increasing number of symbiotic algae and more serious bleaching. In addition, the concentration of 0.001 mmol/L ammonia or nitrate could increase significantly the expulsion of the symbiotic algae of the three coral species. Except for Acropora nobilis, the numbers of symbiotic algae of other two corals did not significantly increase with the increasing concentration of ammonia and nitrate. Furthermore, different hosts have different stress susceptibilities on coral bleaching.     

Sea surface temperature variations recorded on coralline Sr／Ca ratios during Mid-Late Holocene in Leizhou Peninsula

High-resolution Sr/Ca ratios of two Porites corals from Leizhou Peninsula were measured using inductively coupled plasma atomic spectrometry (ICP-AES). TIMS U-Th dating reveals that the life-spans of the two corals are 489-500 AD and 539-530 BC, respectively. Monthly sea surface temperatures (SSTs) during these two periods can be reconstructed from their skeletal Sr/Ca ratios. The results reveal that SSTs during 539-530 BC were roughly the same as those during 1990-2000 AD in this area, indicating a relative warm climate period. However, the period of 489-500 AD was significantly cooler, with annual mean SST, the 10-a average of minimum monthly winter SSTs and the 10-a average of maximum monthly summer SSTs being about 2, 2.9 and 1℃ lower than that in the 1990s, respectively. Such climate patterns agree well with the phenological results recorded in the historic documents in other areas of China.     

Twenty-five years of change in scleractinian coral communities of Daya Bay （northern South China Sea） and its response to the 2008 AD extreme cold climate event

Coral reefs worldwide are becoming increasingly and detrimentally impacted upon by a variety of factors including significant climate changes, such as global warming and increased El Nino-Southern Oscillation activity. Generally, the persistence of coral reefs, especially at low-latitudes, is governed, in part, by sea surface temperatures not exceeding the critical limit （-30℃） at which mass mortality can occur. Thus, it is thought that corals living at high-latitudes （i.e., currently cooler sea surface temperatures） will likely respond more favourably to hypothesized future temperature increases than corals living at low-latitudes （i.e., currently warmer sea surface temperatures）. Consequently, high-latitude coral communities may have the potential to act as regions of refugia for many coral species in the face of potential future global warming. The Daya Bay （22°31′--22°50′N）, northern South China Sea, contains several high-latitude non-reefal coral communities and represents one of the most northerly distributions of scleractinian corals within the region. Significantly, Daya Bay has experienced dramatic warming in both air and sea surface temperatures throughout the past 50 years. In this paper, we analyze 25 years of change in the Daya Bay coral communities, based both on historic surveys and our latest 2006--2008 regional ecological surveys. Our results suggest that, contrary to predictions, there have been significant declines in coral cover within the Daya Bay during the past 25 years （i.e., 76.6% coral cover in 1983/1984 to only 15.3% coral cover by 2008）. Such changes also reflect a significant shift in the most abundant coral species, from Acropora pruinosa to Favites abdita. Most of the modern coral communities became established between 15 and 30 years ago, corresponding to a period of increased winter sea surface temperature. However, very few colonies have become established within the last 15 years, despite a more intense period of warming. By taking into account additional factors, we hypothesize that direct anthropogenic impacts, rather than climatic events, have both restricted the development, and drove the decline, of Daya Bay coral communities in the last 15 years. The Daya Bay has also been subjected to occasional extreme cold events during the past 50 years, with the most recent occurring in early 2008 （13 January-13 February）. During the 2008 cold event, the lowest air temperature reaches only 6.6℃, and the mean sea surface temperature for February fall to 〈 14℃, including six continuous days at 12.3℃. Significantly, the sea surface temperatures fall below the hypothesized critical lower temperature threshold （-13℃） that commonly leads to mass mortality in scleractinian coral communities. Surprisingly, our coral community surveys, conducted both before （August 2007） and after （late February 2008） the extreme 2008 cold event, demonstrate that the Daya Bay coral ecosystems are barely impacted upon during the cold period. Those observations suggest that the Daya Bay scleractinian coral communities have developed adaptations to low sea surface temperatures. Overall, our data support the hypothesis that high-latitude coral communities, such as Daya Bay, have the potential to act as areas of refugia for scleractinian corals in the advent of potential future global warming.     

Estimate of carbonate production by scleractinian corals at Luhuitou fringing reef, Sanya, China

Carbonate production by scleractinian corals not only maintains coral reef growth, but also represents an important source of atmospheric carbon dioxide. In this paper the carbonate production by scler-actinian corals at Luhuitou fringing reef, Sanya, Hainan Island, China, is investigated with an ecological census-based method. Averaged carbonate production is 1.16 ± 0.55 kg·m-2·a-1 and 3.52 ± 1.32 kg·m-2·a-1 on the reef flat and reef slope, respectively, depending on the composition and distribution of cor...     

Coral bleaching: thermal adaptation in reef coral symbionts

Many corals bleach as a result of increased seawater temperature, which causes them to lose their vital symbiotic algae (Symbiodinium spp.) - unless these symbioses are able to adapt to global warming, bleaching threatens coral reefs worldwide. Here I show that some corals have adapted to higher temperatures, at least in part, by hosting specifically adapted Symbiodinium. If other coral species can host these or similar Symbiodinium taxa, they might adapt to warmer habitats relatively easily.     

涠洲岛西局部造礁石珊瑚盖度和大小频率分布

本研究通过分析珊瑚大小频率分布，探讨涠洲岛西局部造礁石珊瑚群落结构特点和种群动态，以了解珊瑚的生活史和所经历的变化。所分析的珊瑚大小数据来自2021年2月24-26日开展的涠洲岛西珊瑚礁的造礁石珊瑚样带调查，利用对数转换将珊瑚大小变换为珊瑚迭代，然后作直方图对珊瑚大小频率分布加以分析。分析结果表明，片状的牡丹珊瑚属Pavona和块状的滨珊瑚属Porites、角蜂巢珊瑚属Favites、盘星珊瑚属Dipsastraea等在涠洲岛西局部珊瑚群落中占优势(珊瑚面积和珊瑚个数)。对数转换的大小频率分布呈正态分布，偏斜不明显，变异系数小于0.5,表明这些珊瑚目前处于正常的自然补充、生长和死亡过程。涠洲岛西局部造礁石珊瑚盖度降低，主要是因为个体大的枝状珊瑚锐减。     

Timing of Holocene sea-level highstands by mass spectrometric U-series ages of a coral reef from Leizhou Peninsula, South China Sea

Systematic mass spectrometric 230Th ages are reported for a Porites coral reef terrace from Dengloujiao,Leizhou Peninsula, South China Sea. Seven episodes of coral growth were recognized in this terrace: 7125±96, 6764±29,5826±37, 5006±54, 2543±24, 1915±15, and 1513±22 calendar years before present (cal. aBP). 50% of the coral age population fall between 7200 and 6600 cal. aBP, marking post-glacial stabdization of global sea level. Considering the facts that ( i ) Dengloujiao reef fiat was measured at 1.6-2.5m above modern tidal datum plane; (ii) modern Porites corals in the South China Sea are living at least ～1 m below the modern tidal datum plane; (iii) the top 20-30 cm of the reef was eroded; and (iv) crustal subsidence in the region since mid-Holocene was negligible, we conclude that the above age groups record at least two major periods (7200-5000 and 2500-1500 cal. aBP) of high sea-level at least 2.9-3.8 m above the present-day level.     

A practical artificial diet for the diamondback moth

A new artificial diet for the diamondback moth,Plutella Xylostella (L), had been selected out successfully. The diet contained the following constituents: soybean powder, wheat germ, wheat bran powder, brewer's yeast and other constituents. So far, the diamondback moth had been reared on this artificial diet for 25 generations and still mantained its normal biological characteristics. Under 25±1 C and 60%–75%RH with 12 h PH, the results of rearing the diamondback moth on the diet as follows: egg hatch, 81.3%–94.7%; survival from eggs to pupae, 55.0%–76.7%; pupal survival, 79.7%–100%; adult emergence, 80%–100%; fecundity 94.7–144. 4 eggs/♀; pupal weight, 90.4–110.8 mg/20 pupae; average days to adult: ♀, 10.2; ♂ 13.1. The diet is not only simpler on the constituents but also have better rearing results and more rearing generations. Li Guanghong: born in June 1965, Ph.D. graduate student. Current research interest is in entomo logical physiology Supported by the State Eighth Five-Year-Plan     

Predicted recurrences of mass coral mortality in the Indian Ocean

In 1998, more than 90% of shallow corals were killed on most Indian Ocean reefs. High sea surface temperature (SST) was a primary cause, acting directly or by interacting with other factors. Mean SSTs have been forecast to rise above the 1998 values in a few decades; however, forecast SSTs rarely flow seamlessly from historical data, or may show erroneous seasonal oscillations, precluding an accurate prediction of when lethal SSTs will recur. Differential acclimation by corals in different places complicates this further. Here I scale forecast SSTs at 33 Indian Ocean sites where most shallow corals died in 1998 (ref. 1) to identify geographical patterns in the timing of probable repeat occurrences. Reefs located 10-15 degrees south will be affected every 5 years by 2010-2025. North and south from this, dates recede in a pattern not directly related to present SSTs; paradoxically, some of the warmest sites may be affected last. Temperatures lethal to corals vary in this region by 6 degrees C, and acclimation of a modest 2 degrees C by corals could prolong their survival by nearly 100 years.     

Heterotrophic plasticity and resilience in bleached corals

Mass coral bleaching events caused by elevated seawater temperatures have resulted in extensive coral mortality throughout the tropics over the past few decades. With continued global warming, bleaching events are predicted to increase in frequency and severity, causing up to 60% coral mortality globally within the next few decades. Although some corals are able to recover and to survive bleaching, the mechanisms underlying such resilience are poorly understood. Here we show that the coral host has a significant role in recovery and resilience. Bleached and recovering Montipora capitata (branching) corals met more than 100% of their daily metabolic energy requirements by markedly increasing their feeding rates and CHAR (per cent contribution of heterotrophically acquired carbon to daily animal respiration), whereas Porites compressa (branching) and Porites lobata (mounding) corals did not. These findings suggest that coral species with high-CHAR capability during bleaching and recovery, irrespective of morphology, will be more resilient to bleaching events over the long term, could become the dominant coral species on reefs, and may help to safeguard affected reefs from potential local and global extinction.     

Genome organization and phylogenetic tree analysis of Garlic virus E, a new member of genus Allexivirus

The complete sequence of an Allexivirus isolated from garlic plants in Yuhang City, Zhejiang Province, China had been determined. The single-strand, positive RNA genome was 8451 nucleotides in length excluding poly(A) tail. The genome organization of this virus was similar to that of the other Allexiviruses but only with 62.8%–64.8% nucleotide acid identities. The amino acid sequences of proteins encoded by ORF1-6 shared 67.6%–78.5%, 55.4%–66.2%, 56.7%–66.4%,40.3%–55.6%,66.3%–79.7%and 52.2%–68.8% identities with those of the others respectively. The homology range between it and the other Allexiviruses was similar to that between the other distinct species in this genus. A more comprehensive comparison using all available CP amino acid sequences showed that it shared only 63.9%–79.8% amino acids identical with the others. Therefore, it had been considered as a new member of the genus, named as garlic virus E (GarV-E). Phylogenetic analysis confirmed GarV-E as a distinct member and the correct names and classification of some members of genus Allexivirus were also discussed.     

Coral community changes in response to a high sedimentation event: A case study in southern Hainan Island

A high sedimentation event caused by dredging and dumping of sediment was recorded on Xiaodonghai Reef in Yulin Bay,southern Hainan Island,China.Significantly high sedimentation and constant light shading were observed during the sediment dumping event(SD Event).Using long-term video transects,we quantified coral community changes and responses to the SD Event between 2008 and 2010.The SD Event caused severe coral mortality on Xiaodonghai Reef at a depth of 6 m,while corals at 3 m were less affected.Total live coral cover at 6 m decreased from 54.3% to 14.8%,and Diploastrea heliopora replaced Galaxea fascicularis as the dominant coral species at 6 and 9 m.The density of juvenile corals also declined after the SD Event,especially for the genera Galaxea and Platygyra.However,the density of juvenile Porites and Pocillopora spp.slightly increased.Monitoring for 11 months after the SD Event indicated no recovery of coral communities on Xiaodonghai Reef.Long-term video transect data also revealed that mean live coral cover dramatically declined,from 30.5% in 2008 to 9% in 2010,while the dominant corals in Yulin Bay shifted to more tolerant coral species,such as massive Porites spp.and D.heliopora.The rapid coral community degradation in Yulin Bay between 2008 and 2010 was probably caused by high sediment deposition resulting from intensive dredging and land-clearing activities.These results highlight the necessity for an integrated watershed management to control sediment deposition on near-shore coral reefs.     

Coastal acidification in summer bottom oxygen-depleted waters in northwestern-northern Bohai Sea from June to August in 2011

Dissolved oxygen(DO) and pH in the central part of the Bohai Sea were surveyed in late June and late August,2011.During the June cruise,the bottom DO was in the range of 215-290 μmol-O2 kg-1(i.e.85%-115% of the saturation level),and the bottom pH was in the range of 7.82-8.04 on the total-hydrogen-ion scale.In August,however,both the bottom DO and the pH had significantly declined in the northwestern-northern near-shore areas,where the water depth was no more than 35 m.The lowest bottom DO was 100-110 μmol-O2 kg-1(only 44%-47% of the June DO values) in the northern near-shore area,where the bottom pH was 7.64-7.68 on the total-hydrogen-ion scale(0.16-0.20 units lower than the June pH value).The largest decreases in DO and in pH were observed in the northwestern near-shore bottom waters,corresponding to declines of 170 μmol-O2 kg-1(as high as 59% of the June DO value) and 0.29 pH units,respectively.The greatest pH decline of 0.29 pH units meant that the total-hydrogen-ion concentration doubled in the bottom waters from June to August.Based on field measurements of bottom DO/pH combined with a simplified model simulation,we suggest that respiration/remineralization-derived CO2 increased the acidity in the bottom oxygen-depleted waters of northwestern-northern near-shore areas in the Bohai Sea as a result of coastal red tides and/or marine aquaculture.This aquatic chemistry is suggested to be partially responsible for scallop-breeding failures in the northwestern Bohai Sea in summer 2011.     

Coral mucus functions as an energy carrier and particle trap in the reef ecosystem

Zooxanthellae, endosymbiotic algae of reef-building corals, substantially contribute to the high gross primary production of coral reefs, but corals exude up to half of the carbon assimilated by their zooxanthellae as mucus. Here we show that released coral mucus efficiently traps organic matter from the water column and rapidly carries energy and nutrients to the reef lagoon sediment, which acts as a biocatalytic mineralizing filter. In the Great Barrier Reef, the dominant genus of hard corals, Acropora, exudes up to 4.8 litres of mucus per square metre of reef area per day. Between 56% and 80% of this mucus dissolves in the reef water, which is filtered through the lagoon sands. Here, coral mucus is degraded at a turnover rate of at least 7% per hour. Detached undissolved mucus traps suspended particles, increasing its initial organic carbon and nitrogen content by three orders of magnitude within 2 h. Tidal currents concentrate these mucus aggregates into the lagoon, where they rapidly settle. Coral mucus provides light energy harvested by the zooxanthellae and trapped particles to the heterotrophic reef community, thereby establishing a recycling loop that supports benthic life, while reducing loss of energy and nutrients from the reef ecosystem.     

The model of hydrocarbon generation and evolution for coal and macerals in the Tuha Basin

By means of Py-GC,¹³c NMR and fluorescent analysis, the properties of hydrocarbon generation of rnacerals are determined, and the evolution model of hydrocarbon generation is established for macerals and coal of the Tuha Basin. There are two stages of oil generation for the coal of the Tuha Basin, whoseR° values are 0.40 %–0.80 % and 0.90 %–1.20 % respectively.     

Sea surface temperature records of core ZY2 from the central mud area in the South Yellow Sea during last 6200 years and related effect of the Yellow Sea Warm Current

Sea surface temperature (SST) records in the South Yellow Sea during the last 6200 years are reconstructed by the unsaturation index of long-chain alkenones (K 37 U ’) in sediment core ZY2 from the central mud area.The SST records varied between 14.1 and 16.5°C (15.6°C on average),with 3 phases:(1) A high SST phase at 6.2-5.9 cal ka BP;(2) A low and intensely fluctuating SST phase at 5.9-2.3 cal ka BP;and (3) A high and stable SST phase since 2.3 cal ka BP.Variation of the SST records is similar to intensity of the Kuroshio Current (KC),and corresponds well in time to global cold climate events.However,the amplitude of the SST response to cooling events was significantly different in different phases.The SST response to global cooling event was weak while the KC was strong;and the SST response was strong while the KC was weak.The difference in amplitude of the SST response is possibly caused by the modulation effect of the Yellow Sea Warm Current which acts as a shelf branch of the KC and a compensating current induced by the East Asia winter monsoon.The warm waters brought by the Yellow Sea Warm Current cushion the SST decrease induced by climate cooling,and both the Kuroshio and East Asian winter monsoon play important roles in the modulation mechanism.The SST records display a periodicity of 1482 years.The same period was found in the KC records,indicating that variation of the SST records in the central South Yellow Sea is strongly affected by KC intensity.The same period was also found in Greenland ice cores and North Atlantic and Arabian Sea sediment cores,showing a regional response of marine environmental variability in the East China Seas to that in the global oceans.     

Origin of middle Miocene leucogranites and rhyolites on the Tibetan Plateau: Constraints on the timing of crustal thickening and uplift of its northern boundary

Leucogranites play a significant role in understanding crustal thickening, melting within continental collisional belts, and plateau uplift. Field investigations show that Miocene igneous rocks from the Hoh Xil Lake area mainly consist of two-mica leucogranites and rhyolites. We studied the Bukadaban two-mica leucogranites and the Kekao Lake, Malanshan and Hudongliang rhyolites by zircon U-Pb, muscovite and sanidine 40Ar/39Ar geochronology, and whole-rock geochemical and Sr-Nd isotopic analysis. Results yielded crystallization and cooling ages for the Bukadaban leucogranites of 9.7±0.2 and 6.88±0.19 Ma, respectively. Extrusive ages of the Kekao Lake and Malanshan rhyolites are 14.5±0.8 and 9.37±0.30 Ma, respectively. All rocks are enriched in SiO2 (70.99%-73.59%), Al2O3 (14.39%-15.25%) and K2O (3.78%-5.50%) but depleted in Fe2O3 (0.58%-1.56%), MgO (0.11%- 0.44%) and CaO (0.59%-1.19%). The rocks are strongly peraluminous (A/CNK=1.11?1.21) S-type granites characterized by negative Eu anomalies (δ Eu=0.18-0.39). In also considering their Sr-Nd isotopic compositions (87Sr/86Sri=0.7124 to 0.7143; δ Nd (9 Ma) =-5.5 to -7.1), we propose that these igneous rocks were generated through dehydration melting of muscovite in the thickened middle or lower crust of northern Tibet. Melting was probably triggered by localized E-W stretching decompression in the horse tails of Kunlun sinistral strike-slip faults. Reactivation of the Kunlun strike-slip faults, accompanied by emplacement of leucogranite and eruption of rhyolite in the Hoh Xil Lake area, indicates that large-scale crustal shortening and thickening in northern Tibet mainly occurred before 15 Ma. In addition, these findings suggest that the northern Tibetan Plateau attained its present elevation (~5000 m) at least 15 Ma ago.     

Treatment efficiency of integrated vertical-flow constructed wetland for saline wastewater

The integrated vertical-flow constructed wetland(IVCW) was simulated with three suits of designed experiment columns planted with Kandelia candel.Units A,B and C were irrigated with sewage of different salinity(A:10‰ B:20‰,C:30‰),respectively.The removal rates of dissolved organic carbon(DOC),NH3-N and NO3--N dropped 90.4%-48.6%,80.2%-40.3% and 84.8%-60.9%,respectively,when salinity increases from 10‰ to 30‰.The removal rate of TP increased 14%-31.2%,oppositely.A 20-day inflow salinity drastic change shock affective trial was done on units D and E.Unit D was used as a control and irrigated with saline sewage(20‰).Unit E was irrigated with sewage with low salinity(5‰) as a salinity drastic change shock on the third and fourth days.DOC,NH3-N and NO3--N removal efficiency of unit E showed a three-stage process of change,"rapidly decrease,increase beyond the normal standard,and then back to the normal standard".TP removal value was negative during the 2-day shock period.     

A competitive dual-label time-resolved fluoroimmunoassay for the simultaneous determination of chloramphenicol and ractopamine in swine tissue

A novel dual-label time-resolved fluoroimmunoassay method was developed for the simultaneous determination of chloramphenicol (CAP) and ractopamine (RAC) residues in 18 swine tissue samples, using anti-CAP and anti-RAC monoclonal antibodies labeled with europium (Eu³⁺) and samarium (Sm³⁺), respectively. The detection limits for CAP and RAC were 0.06 and 0.25 ng/g. The recovery from swine muscle samples was 102%–121% for CAP at spiking levels of 0.1–5 ng/g, and 69.8%–85.8% for RAC at spiking levels of 1–10 ng/g. The results obtained from the swine tissue samples using this method showed good agreement with those obtained using ELISA and GC-MS, with correlation coefficients (R) between 0.92–0.98.