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Cover Story
China published ocean forecasting system for the 21st-Century Maritime Silk Road on December 10, 2018
Fangli Qiao, Guansuo Wang, Somkiat Khokiattiwong, Mohd Fadzil Akhir, Wenxi Zhu, Bin Xiao
2019, 38(1): 1-3. doi: 10.1007/s13131-019-1365-y
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Editorial
Introduction of the special issue on the 10th WESTPAC International Scientific Conference
Fangli Qiao, Si Tuan Vo, Wenxi Zhu
2019, 38(1): 4-4. doi: 10.1007/s13131-019-1364-z
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Seasonal prediction skills of FIO-ESM for North Pacific sea surface temperature and precipitation
Yiding ZHAO, Xunqiang YIN, Yajuan SONG, Fangli QIAO
2019, 38(1): 5-12. doi: 10.1007/s13131-019-1366-x
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The seasonal prediction of sea surface temperature (SST) and precipitation in the North Pacific based on the hindcast results of The First Institute of Oceanography Earth System Model (FIO-ESM) is assessed in this study. The Ensemble Adjusted Kalman Filter assimilation scheme is used to generate initial conditions, which are shown to be reliable by comparison with the observations. Based on this comparison, we analyze the FIO-ESM 6-month hindcast results starting from each month of 1993–2013. The model exhibits high SST prediction skills over most of the North Pacific for two seasons in advance. Furthermore, it remains skillful at long lead times for mid-latitudes. The reliable prediction of SST can transfer fairly well to precipitation prediction via air-sea interactions. The average skill of the North Pacific variability (NPV) index from 1 to 6 months lead is as high as 0.72 (0.55) when El Niño-Southern Oscillation and NPV are in phase (out of phase) at initial conditions. The prediction skill of the NPV index of FIO-ESM is improved by 11.6% (23.6%) over the Climate Forecast System, Version 2. For seasonal dependence, the skill of FIO-ESM is higher than the skill of persistence prediction in the later period of prediction.
Seasonal characteristics and forcing mechanisms of the surface Kuroshio branch intrusion into the South China Sea
Jingsong GUO, Zhixin ZHANG, Changshui XIA, Binghuo GUO
2019, 38(1): 13-21. doi: 10.1007/s13131-017-1132-x
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Using observational data of Argos satellite-tracked drifters from 1988 to 2012, we analyzed seasonal characteristics of the surface Kuroshio branch (KB) intrusion into the South China Sea (SCS). The analysis results are as follows. The surface KB originates from the southern Balintang Channel (BLTC) and Babuyan Channel (BBYC). It begins in late September, reaches peak strength in November–December, and declines at the end of March. The mean speed of drifters along the KB path during their traverse of the Luzon Strait (LS) was 43% faster than during the two days before entering the LS for the flow originating from the southern BLTC, but there was a 24% increase in speed for the flow from the BBYC. The observations show that in winter, monthly-mean sea-level anomalies (SLAs) were positive southwest of Taiwan Island and extended to the northern LS. The SLAs were negative northwest of Luzon Island and extended to the southern LS, which acted like a pump, forcing a part of Kuroshio water westward into the SCS. The condition under which the KB forms was solved by a set of simplified motion equations. The results indicate that whether the KB can form depends upon the sea-level gradient at the central LS and region to the west, as well as the location, speed and direction of Kuroshio surface water when it enters the LS.
Temperature variability caused by internal tides in the coastal waters of east coast of Peninsular Malaysia
Nur Hidayah ROSELI, Mohd Fadzil AKHIR
2019, 38(1): 22-31. doi: 10.1007/s13131-019-1367-9
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The effects of tidal currents (i.e., barotropic and internal tides) are important in the biogeochemistry of a coastal shelf sea. The high-frequency of currents and near-bottom temperatures collected in three consecutive southwest monsoon seasons (May, June, July and August of 2013 until 2015) is presented to reveal the role of the tidal currents to the temperature variability in the coastal shelf sea of the east coast of Peninsular Malaysia (ECPM), south of the South China Sea (SCS). The results of a spectral density and harmonic analysis demonstrate that the near-bottom temperature variability and the tidal currents are influenced by diurnal (O1 and K1) and semidiurnal (M2) tidal currents. The spectral density of residual currents (detided data) at 5, 10 and 16 m depth also shows significant peaks at the diurnal tidal frequency (K1) and small peaks at the semidiurnal tidal frequency (M2) indicating the existence of internal tides. The result of the horizontal kinetic energy (HKE) shows a strong intermittent energy of internal tides in the ECPM with the strongest energy is found at 16 m depth during a sporadic cooling event in June and July. A high horizontal cross-shore heat flux (16 m) also indicates strong intrusions of cooler water into the ECPM in June and July. During the short duration of cold pulse water observed in June and July, a cross-wavelet analysis also reveals the strong relationship between the near-bottom temperatures and the internal tidal currents at the diurnal tidal frequency. The intrusion of this cooler water is probably related to the monsoon-induced upwelling in June. It is loosely interpreted that the interaction between the strong barotropic tides and the steep slope in the central basin of the SCS under the stratified condition in southwest monsoon has generated these internal tides. The dissipation of internal tides from the slope area probably has driven the cold-upwelled water into the ECPM coastal shelf sea when the upwelling intensity is the highest in June and July.
The summertime circulation of the Bohai Sea simulated from a high-resolution wave-tide-circulation coupled model
Changshui XIA, Jingsong GUO, Guansuo WANG, Zhenhua CHEN, Xiaodi KUANG
2019, 38(1): 32-37. doi: 10.1007/s13131-018-1145-0
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The Bohai Sea is a shallow semi-enclosed inner sea with an average depth of 18 m and is located at the west of the northern Yellow Sea. The climatological circulation pattern in summer of the Bohai Sea is studied by using a wave-tide-circulation coupled model. The simulated temperature and the circulation agree with the observation well. The result shows that the circulation pattern of the Bohai Sea is jointly influenced by the tidal residual current, wind and baroclinic current. There exists an obvious density current along the temperature front from the west part of the Liaodong Bay to the offshore area of the Huanghe Estuary. In the Liaodong Bay there exists a clockwise gyre in the area north to the 40°N. While in the area south to the 40°N the circulation shows a two-gyre structure, the flow from the offshore area of the Huanghe Estuary to the Liaodong Bay splits into two branches in the area between 39°N and 40°N. The west branch turns into north-west and forms an anti-clockwise gyre with the south-westward density current off the west of the Liaodong Bay. The east branch turns to the east and forms a clockwise gyre with the flow along the east coast of the Liaodong Bay. The forming mechanism of the circulation is also discussed in this paper.
Exploring thermocline and water masses variability in southern South China Sea from the World Ocean Database (WOD)
Afifi Johari, Mohd Fadzil Akhir
2019, 38(1): 38-47. doi: 10.1007/s13131-019-1368-8
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Study about water characteristics (temperature and salinity) from the World Ocean Database (WOD) was conducted in the area of southern South China Sea (SSCS), covering the area of 0°–10°N, 100°–117°E. From inter-annual analysis, upper layer (10 m) and deep water temperature (50 m) increased from 1951 until 2014. Monthly averaged show that May recorded the highest upper layer temperature while January recorded the lowest. It was different for the deep water which recorded the highest value in September and lowest in February. Contour plot for upper layer temperature in the study area shows presence of thermal front of cold water at southern part of Vietnam tip especially during peak northeast season (December–January). The appearances of warm water were obviously seen during generating southwest monsoon (May–June). Thermocline study revealed the deepest isothermal layer depth (ILD) during peak northeast and southwest monsoon. Temperature threshold at shallow area reach more than 0.8°C during the transitional period. Water mass study described T-S profile based on particular region. Water mass during the southwest monsoon is typically well mixed compared to other seasons while strong separation according to location is very clear. During transitional period between northeast monsoon to southwest monsoon, the increasing of water temperature can be seen at Continental Shelf Water (CSW) which tend to be higher than 29°C and vice versa condition during transitional period between southwest monsoon to northeast monsoon. Dispersion of T-S profile can be seen during southwest monsoon inside Tropical Surface Water (TSW) where the salinity and temperature become higher than during northeast monsoon.
Dynamic of ENSO towards upwelling and thermal front zone in the east coast of Peninsular Malaysia
Nurul Rabitah DAUD, Mohd Fadzil AKHIR, Aidy M Muslim
2019, 38(1): 48-60. doi: 10.1007/s13131-019-1369-7
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The El Niño Southern Oscillation (ENSO) is a natural phenomenon that relates to the fluctuation of temperatures over the Pacific Ocean. The ENSO significantly affects the ocean dynamics including upwelling event and coastal front. A recent study discovered the seasonal upwelling in the east coast of Peninsular Malaysia (ECPM), which is significant to the fishery industry in this region. Thus, it is vital to have a better understanding of the influence of ENSO towards the coastal upwelling and thermal front in the ECPM. The sea surface temperature (SST) data achieved from moderate resolution imaging spectroradiometer (MODIS) aboard Aqua satellite are used in this study to observe the SST changes from 2005 to 2015. However, due to cloud cover issue, a reconstruction of data set is applied to MODIS data using the data interpolating empirical orthogonal function (DINEOF) to fill in the missing gap in the dataset based on spatial and temporal available data. Besides, a wavelet transformation analysis is done to determine the temperature fluctuation throughout the time series. The DINEOF results show the coastal upwelling in the ECPM develops in July and reaches its peak in August with a clear cold water patch off the coast. There is also a significant change of SST distribution during the El Niño years which weaken the coastal upwelling event along the ECPM. The wavelet transformation analysis shows the highest temperature fluctuation is in 2009–2010 which indicates the strongest El Niño throughout the time period. It is suggested that the El Niño is favourable for the stratification in water column thus it is weakening the upwelling and thermal frontal zone formation in ECPM waters.
The response of the upper ocean to tropical cyclone Viyaru over the Bay of Bengal
Mir Kashem, Md Kawser Ahmed, Fangli Qiao, M A E Akhter, K M Azam Chowdhury
2019, 38(1): 61-70. doi: 10.1007/s13131-019-1370-1
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Better forecast of tropical cyclone (TC) can help to reduce risk and enhance management. The TC forecast depends on the scientific understanding of oceanic processes, air-sea interaction and finally, the atmospheric process. The TC Viyaru is taken as an example, which is formed at the end of 11 May 2013 and sustains up to 17 May 2013 during pre-monsoon season. Argo data are used to investigate ocean response processes by comparing pre- and post-conditions of the TC. Eight oceanic parameters including the sea surface temperature (SST), the sea surface salinity (SSS), and the barrier layer thickness (BLT), the 26°C isotherm depth in the ocean (D26), the isothermal layer depth (ILD), the mixed layer depth (MLD), the tropical cyclone heat potential (TCHP) and the effective oceanic layer for cyclogenesis (EOLC) are chosen to evaluate the pre- and post-conditions of the TC along the track of Viyaru. The values of the SST, D26, BLT, TCHP and EOLC in the pre-cyclonic condition are higher than the post-cyclonic condition, while the SSS, ILD and MLD in the post-cyclonic condition are higher than the pre-cyclonic condition of the ocean due to strong cyclonic winds and subsurface upwelling. It is interesting that the strong intensity of the TC reduces less SST and vice versa. The satisfied real time Argo data is not available in the northern Bay of Bengal especially in the coastal region. A weather research and forecasting model is employed to hindcast the track of Viyaru, and the satellite data from the National Center Environmental Prediction are used to assess the hindcast.
Geochemistry and age of seamounts in the West Pacific: mantle processes and petrogenetic implications
Limei TANG, Yanhui DONG, Fengyou CHU, Ling CHEN, Weilin MA, Yonggang LIU
2019, 38(1): 71-77. doi: 10.1007/s13131-019-1371-0
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Research on seamounts provides some of the best constraints for understanding intraplate volcanism, and samples from seamounts reveal crucial evidence about the geochemical makeup of the oceanic mantle. There are still many seamounts in the West Pacific Seamount Province (WPSP) that have not been studied, meaning their ages and geochemistry remain unknown. A better understanding of these seamount trails and their evolutionary history, investigated with age and geochemistry data, will enable better understanding of the geological processes operating underneath the Pacific Ocean Plate. Here, new 40Ar/39Ar ages and trace element and Sr-Nd-Pb isotopic data for seven basalt rocks from four seamounts in the WPSP are provided. Chemically, these rocks are all Oceanic Island Alkali basalt (OIA type); analysis of olivine phenocrysts shows that the magmas experienced strong olivine fractionation and changed from olivine + plagioclase to olivine + plagioclase + clinopyroxene cotectic during their evolution. Rare earth element (REE) patterns and a spider diagram of the samples in this study show OIB (Ocean Island Basalt) like behavior. The range of 87Sr/86Sr values is from 0.704 60 to 0.706 24, the range of 206Pb/204Pb values is from 18.241 to 18.599, and the range of 143Nd/144Nd values is from 0.512 646 to 0.512 826; together, these values indicate magma sources ranging from EMI to EMII. Finally, new 40Ar/39Ar age data show that these seamounts formed at ~97 and ~106 Ma, indicating that some may have undergone the same formation processes as seamounts in the eastern part of the Magellan Seamount Trail, but other seamounts likely have different origins.
The biogenic silica variation and paleoproductivity evolution in the eastern Indian Ocean during the past 20 000 a
Yonghang XU, Liang WANG, Zhikun LAI, Xiaohui XU, Feng WANG, Shengfa LIU, Xuefa SHI, Rainer Arief TROA, Rina ZURAIDA, Eko TRIARSO, Marfasran HENDRIZAN
2019, 38(1): 78-84. doi: 10.1007/s13131-019-1372-z
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The biogenic silica of sediment samples from Core CJ01-185 which is collected from the eastern India Ocean off the Sunda Strait is analyzed to evaluate the impact of the opening of the Sunda Strait on a paleoproductivity evolution. The new results indicate that the biogenic silica mass values of Core CJ01-185 show the lowest 0.86% in the last glacial period, and reach its maxima of 1.89% in the late Holocene. Furthermore, the biogenic silica mass accumulation rate (MARBSi) values also vary with much higher during the late Holocene than during the last glaciation. The input of additional terrigenous materials from the Java Sea has enhanced the paleoproductivity and increased the biogenic silica mass and MARBSi values after the opening of the Sunda Strait. It is suggested that the paleoproductivity in the study area is mainly influenced by the southeast monsoon and upwelling before the opening of the Sunda Strait. However, the paleoproductivity is dominated by the terrigenous materials input other than by the southeast monsoon or upwelling in the Holocene.
Preliminary analysis of echolocation signals produced by fleeing Irrawaddy dolphins (Orcaella brevirostris)
Ying JIANG, Xuelei ZHANG, Zhiguo YANG, Saifullah Arifin JAAMAN, Qinzeng XU, Azmi Marzuki MUDA, Hairul Masrini MUHAMAD
2019, 38(1): 85-89. doi: 10.1007/s13131-019-1373-y
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In this study, echolocation signals were recorded from a wild Irrawaddy dolphin (Orcaella brevirostris) in shallow water in the Bay of Brunei. During sound recording, a small fishing boat engine startled a nearby Irrawaddy dolphin and began chasing it on two occasions. Variations in the acoustic parameters were detected. When the Irrawaddy dolphin was startled and chased, the sound pressure level, number of click trains per minute, pulse number, and average inter-pulse interval (PI) per click train were all affected. The PI increased and exhibited a slight downward trend during the chase. The increase in PI indicated an increase in the inspection distance as the dolphin escaped. Thus, Irrawaddy dolphins may adapt their echolocation signals to stand out from ambient noise in the wild and to improve their search efforts in potentially risky situations. Appropriate management of the burst noise around the dolphins is important.
A model for the transportation and distribution of jellyfish Rhopilema esculentum for stock enhancement in the Liaodong Bay, China
Liping Yin, Xiujuan SHAN, Chang ZHAO, Xianshi JIN, Guansuo WANG, Fangli QIAO
2019, 38(1): 90-101. doi: 10.1007/s13131-019-1374-x
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A numerical model for jellyfish Rhopilema esculentum stock enhancement is developed for the first time. The model is based on an operational ocean circulation-surface wave coupled forecasting system for the seas off China and adjacent areas and uses a Lagrangian particle-tracking scheme to track the trajectories of released jellyfish. The Jellyfish are modeled as particles with diel vertical migration and are passively drifted by the current and dispersion due to the sub-grid processes. A comparison between the simulation and survey results demonstrate that the model can capture the primary distribution patterns of the released jellyfish. The model results show that the ocean current and indirect wind impact are the main drivers controlling the jellyfish transport. A connectivity matrix between the release sites and fishing grounds indicates the top of the bay is better than the eastern and western coasts for jellyfish fishing. The matrix also shows that only 45% and 27% of the jellyfish released from Wafangdian (WFD) can enter the fishing ground in 2008 and 2010; thus, the site near WFD is not an advisable location for jellyfish release. A Lagrangian probability density function based on a nine-year tracing experiment validates the results and further provides a " climatology” distribution of the released jellyfish. Several experiments are conducted to examine the sensitivity of the model to random walk schemes and to release conditions. The model requires a random walk but is insensitive to the random walk scheme. The experiments with different habitat depths show that if the jellyfish are fixed on the bottom of the water, most of them will be transported to the center, or even out of the bay, by the bottom circulation.
Monitoring of coral communities in the inner Gulf of Thailand influenced by the elevated seawater temperature and flooding
Sittiporn PENGSAKUN, Thamasak YEEMIN, Makamas SUTTHACHEEP, Watchara SAMSUVAN, Wanlaya KLINTHONG, Charernmee CHAMCHOY
2019, 38(1): 102-111. doi: 10.1007/s13131-019-1376-8
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There were two severe coral bleaching events at Ko Khang Khao, the inner Gulf of Thailand, occurred during the prolonged period of the elevated sea surface temperature (SST) in 2010 and low salinity as well as turbidity due to heavy flooding in 2011. The bleaching index (BI) and mortality index (MI) are calculated to compare the susceptibilities of coral species in the two bleaching events. The BI and MI vary significantly among the study sites and bleaching events. The most susceptible corals during both bleaching events are Acropora millepora, Pocillopora damicornis and Pavona decussate, while the most resistant species were Galaxea fascicularis, Fungia fungites, Pavona frondifera, Oulastrea crispate, and Symphyllia recta. The corals Favia favus, Goniopora columna, Platygyra pini, Symphyllia agaricia were relatively more tolerant to high SST but they are relatively more susceptible to low salinity. Coral bleaching is a phenomenon that the dissociation stress of the symbiotic relationship between zooxanthellae and their cnidarian host results in the reduction in photosynthetic pigment concentration. Among stressors, both prolonged exposure of high SST and low salinity, above and below their thresholds, respectively. The long-term resilience of coral communities at Ko Khang Khao and other coral communities close to the mouth of large rivers may depend on the frequency and duration of the exposure on the elevated SST due to atmospheric heating and low salinity due to river flooding.
A study of coral reef resilience and implications of adaptive management and rehabilitation in Khanh Hoa Province, Vietnam
Si Tuan VO, Thai Tuyen HUA, Kim Hoang PHAN
2019, 38(1): 112-117. doi: 10.1007/s13131-019-1377-7
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The Province of Khanh Hoa, Vietnam, is located in the western South China Sea and boasts a shoreline of 385 km and many islands. Previous studies have indicated the extreme diversity and abundance of coral reefs in its waters as compared with other coastal provinces of Vietnam. A study on the resilience of coral reefs against increased surface water temperature and anthropogenic impact is conducted at 19 reef sites in 2015. At each site, a series of parameters (e.g., coral covers, genus diversity, and coral recruitment, substratum heterogeneity, depth, water exchange level, and sediment deposit and water temperature) are measured quantitatively or semi-quantitatively. The measured data are rated based on the relationship between the parameter values and coral susceptibility; the consideration that reef health reflects the biological capability to adapt to environmental changes and the recruitment potential if bleached; and positive or negative influences of physical factors in the mitigation of thermal stress and protecting corals from bleaching. A cumulative analysis enables researchers to divide the studied reefs into four categories based on varying levels of reef health to support resilience, recovery, and vulnerability in the case of increased water temperature. Relevant management interventions for each category and other supporting activities are suggested to enhance management effectiveness and to plan the rehabilitation of coral reefs for biodiversity conservation and touristic development, taking into account the involvement of related stakeholders.
Diseases and compromised health states of massive Porites spp. in the Gulf of Thailand and the Andaman Sea
Watchara SAMSUVAN, Thamasak YEEMIN, Makamas SUTTHACHEEP, Sittiporn PENGSAKUN, Juthamart PUTTHAYAKOOL, Monthaphat THUMMASAN
2019, 38(1): 118-127. doi: 10.1007/s13131-019-1378-6
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In this study, we assess coral health by detecting the severity of coral diseases and compromised health states on massive Porites. Field surveys are conducted at twenty-two sites covering the eastern, inner and western Gulf of Thailand as well as the Andaman Sea during 2010–2015. A total of nine coral diseases and signs of compromised health are observed in the waters of Thailand, consisting of pigmentation responses (pink lines, pink patches, pink spots and pink borers), white syndromes (white patches, white bands and ulcerative white spots), growth anomalies, and unusual bleaching patterns. The highest severity of all observed coral diseases and signs of compromised health are found at Ko Khang Khao in the inner Gulf of Thailand, while that observed in the Andaman Sea is relatively low. Composition of the diseases vary across the study sites. Four groups of study sites, in which there is an 80% similarity of diseases or signs of compromised health composition, are clustered and detected based on the Bray-Curtis similarity. The canonical analysis of principal coordinates reveal that most study sites in the Gulf of Thailand, especially the inner Gulf of Thailand, tend to show a high severity of the diseases. The association of disease severity and composition and the level of human impact are also detected. The study sites located near the shores and/or the areas with intensive tourism tend to have higher human impact, especially on poor water quality, which may be linked to the higher severity and composition of coral diseases and signs of compromised health in the Gulf of Thailand. Fish bites are also observed in many study sites. The severity of fish bites in the Gulf of Thailand is much lower compared to the Andaman Sea. Ko Rawi exhibits the highest severity, following by Ko Surin Nua and Ko Butang. The study sites within marine national park boundaries have a significantly higher severity of fish bites than those outside of the marine national park boundaries. This study suggests that higher coral diseases and signs of compromised health severity might be linked to anthropogenic disturbances on coral communities in the waters of Thailand.
Isolation, characterization and implications of the bacterial communities associated with established cultures of Chattonella marina (Raphidophyceae) and Skeletonema costatum (Bacillariophyceae)
Jian WANG, Zhaohui WANG, Jiangang ZHAO
2019, 38(1): 128-135. doi: 10.1007/s13131-019-1379-5
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Cultivable bacteria coexisting in the cultures of two microalgal species, Chattonella marina (Raphidophyceae) and Skeletonema costatum (diatom, Bacillariophyceae), which have been maintained in the laboratory for several years, were examined in this study. Forty-eight and thirty-four cultivable bacterial strains were isolated from different growth stages of C. marina and S. costatum cultures, respectively. A total of twelve unique bacterial phylotypes were isolated. These bacterial phylotypes belonged to Alphaproteobacteria, Gammaproteobacteria, Bacteroidetes, and Actinobacteria. Alphaproteobacteria predominated in phycospheres of both microalgae, and Rhodobacteraceae was the most common family. Bacterial phylotypes were more diversified in cultures of S. costatum than in those of C. marina. Bacterial concentrations increased remarkably after the late stationary phase of C. marina, which might account for the decline in algal cells. One phylotype of S. costatum-associated bacteria had inhibitory effects on Chaetoceros curvisetus (Bacillariophyceae). However, most bacterial phylotypes from cultures of C. marina showed significant inhibition of the growth of C. curvisetus. The results suggested that bacteria associated with C. marina might have some ecological roles in its competition with diatoms.
The origin of the suspended particulate matter in the seagrass meadow of tropical waters, an evidence of the stable isotope signatures
A’an Johan WAHYUDI, AFDAL
2019, 38(1): 136-143. doi: 10.1007/s13131-019-1380-z
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Suspended particulate matter (SPM) has been known as an important variable in the organic matter flow of coastal ecosystem. Half of burial carbon in seagrass meadows is contributed by allochthonous sources that compose the SPM such as phytoplankton, seagrass detritus, marine snow aggregates and terrestrially derived particles. Each composition of the SPM contributes different roles and is important to be identified, for instance, the exact contribution of seagrass detritus will be useful for determination of carbon export through the detritus form in seagrass meadows. Here, the SPM of seagrass meadows is studied in Bintan Island and the Selayar Archipelago. The aim of this research is to determine the source origin of the SPM using a stable isotope signature. In order to fulfill this aim, the objectives are defined as: (1) to specify the stable isotope signature (δ13C and δ15N) of the SPM, and (2) to determine the proportional distribution of the SPM’s prospectus sources. The result shows that the possibility of the source origin of the SPM includes a seagrass fraction (Enhalus acoroidesand Thalassia hemprichii), terrestrial C4 plant, macroalgae, and terrestrial C3 plant. The SPM lies between the marine- and terrigenous-end members. However, it seems that the SPM is more to be terrigenous-end and allochthonous. According to a Bayesian mixing model, the terrestrial C4 has the highest contribution of the SPM at all sites except Barugaia and Pasi Island in Selayar (i.e., the highest contribution of the SPM is from the detritus of E. acoroides). The second contribution has been contributed by either seagrass detritus (E. acoroides or Th. hemprichii) or terrestrial C3 plant. The finding of this study indicates that there is a strong influence of the terrigenous sources in the SPM of the seagrass meadows.
Assessment by microsatellite analysis of genetic diversity and population structure of Enhalus acoroides from the coast of Khanh Hoa Province, Vietnam
Xuan-Vy NGUYEN, Papenbrock JUTTA
2019, 38(1): 144-150. doi: 10.1007/s13131-019-1381-y
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Seagrass beds degraded significantly since the last century on both, global and local scale. The seagrass species Enhalus acoroides (Linnaeus f.) Royle is a common species found in almost all marine ecosystems including bays, lagoons and around offshore islands in tropical regions of the West Pacific. It was shown that genetic diversity is an essential indicator of the conditions of ecosystems. In the present study, microsatellite markers were used to assess the genetic diversity and population structure of six distinct seagrass beds along the coast of the Khanh Hoa Province, Vietnam. The results indicate that the genetic diversity of the populations in the open sea is higher than in the lagoon. Seagrass beds occurring in disturbed sites show reduced genetic diversity. The fixing index value (FST) depicts a relatively high genetic structure among populations. Structure analysis clusters the populations into open sea and lagoon populations and cluster analysis and AMOVA indicate a significant difference between the two groups. There are low but non-significant positive correlations between geographic and genetic distances. The different habitats of the open sea and the lagoon are probably responsible for forming two groups.
Response of size-fractionated phytoplankton to environmental factors near the Changjiang Estuary
Li LI, Jingyi CEN, Lei CUI, Songhui LU
2019, 38(1): 151-159. doi: 10.1007/s13131-018-1259-4
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Size-based partitioning of phytoplankton is a useful tool for monitoring key phytoplankton traits, and it provides a better understanding of phytoplankton dynamics. Our aim is to determine the variation in the different size classes of phytoplankton to the total phytoplankton biomass during the spring and autumn of 2010 and examine the relationship between phytoplankton size structure and environmental variables and zooplankton community structure near the Changjiang Estuary. In the spring, phytoplankton populations were predominantly consisted of nanophytoplankton throughout the study region. In the autumn, picophytoplankton and nanophytoplankton collectively dominated the phytoplankton community. A Pearson correlation analysis highlighted the role of temperature and trophic conditions on the contributions of nanophytoplankton and picophytoplankton. The grazing pressure exerted by mesozooplankton could have played an important role in determining the microphytoplankton community structure.
The impact of biotic and abiotic factors on the distribution of surface sediment dinoflagellate cyst assemblages on the Nanji Island in the East China Sea
Han GAO, Shengpao YOU, Xiangdong LEI, Yunpu XIAO, Haifeng GU, Mengmeng TONG
2019, 38(1): 160-171. doi: 10.1007/s13131-019-1375-9
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Abstract:
The dinoflagellate cyst assemblages on the Nanji Island in the East China Sea, are documented at the first time to construct a quantitative overview of the cyst bank from 2014 to 2015. Thirty-four morphotypes from six groups are identified and quantified at eight sampling sites around the island, including a high proportion of potentially toxigenic species (14%). Autotrophic dinocysts constitute 74% of the total cyst counts, which is relatively low (two to thirty-three per millilitre sediment) compared with previous studies in adjacent areas. Scrippsiella trochoidea and Protoperidinium avellanaare the most abundant autotrophic and heterotrophic species, respectively. A multivariate analysis is performed to assess associations between dinocysts and abiotic or biotic variables. Differentiation among seasons is evident in the detrended correspondence analysis (DCA) ordination plot, while a spatial pattern is not clearly revealed despite heterogeneity of the hydrodynamic conditions between sampling sites. Soluble reactive phosphate, the ratio of nitrogen to phosphorus concentrations and Karenia mikimotoi bloom are the three factors significantly (P<0.05) related to surface sediment cyst assemblage defined by the canonical correspondence analysis (CCA), highlighting the importance of nutrient regime to a dinocyst distribution in this area. Although attempts to address the origin of HAB events in recent years using seed banks have failed, knowledge can be valuable for further investigation of dinocyst dynamics and potential toxin threats on the Nanji Island.
Performances of conventional fusion methods evaluated for inland water body observation using GF-1 image
Yong DU, Xiaoyu ZHANG, Zhihua MAO, Jianyu CHEN
2019, 38(1): 172-179. doi: 10.1007/s13131-019-1382-x
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Abstract:
Satellite remote sensing of inland water body requires a high spatial resolution and a multiband narrow spectral resolution, which makes the fusion between panchromatic (PAN) and multi-spectral (MS) images particularly important. Taking the Daquekou section of the Qiantang River as an observation target, four conventional fusion methods widely accepted in satellite image processing, including pan sharpening (PS), principal component analysis (PCA), Gram-Schmidt (GS), and wavelet fusion (WF), are utilized to fuse MS and PAN images of GF-1. The results of subjective and objective evaluation methods application indicate that GS performs the best, followed by the PCA, the WF and the PS in the order of descending. The existence of a large area of the water body is a dominant factor impacting the fusion performance. Meanwhile, the ability of retaining spatial and spectral informations is an important factor affecting the fusion performance of different fusion methods. The fundamental difference of reflectivity information acquisition between water and land is the reason for the failure of conventional fusion methods for land observation such as the PS to be used in the presence of the large water body. It is suggested that the adoption of the conventional fusion methods in the observing water body as the main target should be taken with caution. The performances of the fusion methods need re-assessment when the large-scale water body is present in the remote sensing image or when the research aims for the water body observation.