Growth,feeding and ecological roles of the mixotrophic and heterotrophic dinoflagellates in marine planktonic food webs

Planktonic mixotrophic and heterotrophic dinoflagellates are ubiquitous protists and often abundant in marine environments. Recently many phototrophic dinoflagellate species have been revealed to be mixotrophic organisms and also it is suggested that most dinoflagellates may be mixotrophic or heterotrophic protists. The mixotrophic and heterotrophic dinoflagellates are able to feed on diverse prey items including bacteria, picoeukaryotes, nanoflagellates, diatoms, other dinoflagellates, heterotrophic protists, and metazoans due to their diverse feeding mechanisms. In turn they are ingested by many kinds of predators. Thus, the roles of the dinoflagellates in marine planktonic food webs are very diverse. The present paper reviewed the kind of prey which mixotrophic and heterotrophic dinoflagellates are able to feed on, feeding mechanisms, growth and ingestion rates of dinoflagellates, grazing impact by dinoflagellate predators on natural prey populations, predators on dinoflagellates, and red tides dominated by dinoflagellates. Based on this information, we suggested a new marine planktonic food web focusing on mixotrophic and heterotrophic dinoflagellates and provided an insight on the roles of dinoflagellates in the food web.     

Origin of the metamorphosed clasts in the CV3 carbonaceous chondrite breccias of Graves Nunataks 06101, Vigarano,Roberts Massif 04143, and Yamato‐86009

We observed metamorphosed clasts in the CV3 chondrite breccias Graves Nunataks 06101, Vigarano, Roberts Massif 04143, and Yamato‐86009. These clasts are coarse‐grained polymineralic rocks composed of Ca‐bearing ferroan olivine (Fa_24–40, up to 0.6 wt% CaO), diopside (Fs_7–12Wo_44–50), plagioclase (An_52–75), Cr‐spinel (Cr/[Cr + Al] = 0.4, Fe/[Fe + Mg] = 0.7), sulfide and rare grains of Fe‐Ni metal, phosphate, and Ca‐poor pyroxene (Fs₂₄Wo₄). Most clasts have triple junctions between silicate grains. The rare earth element (REE) abundances are high in diopside (REE ~3.80–13.83 × CI) and plagioclase (Eu ~12.31–14.67 × CI) but are low in olivine (REE ~0.01–1.44 × CI) and spinel (REE ~0.25–0.49 × CI). These REE abundances are different from those of metamorphosed chondrites, primitive achondrites, and achondrites, suggesting that the clasts are not fragments of these meteorites. Similar mineralogical characteristics of the clasts with those in the Mokoia and Yamato‐86009 breccias (Jogo et al. 2012 ) suggest that the clasts observed in this study would also form inside the CV3 chondrite parent body. Thermal modeling suggests that in order to reach the metamorphosed temperatures of the clasts of >800 °C, the clast parent body should have accreted by ~2.5–2.6 Ma after CAIs formation. The consistency of the accretion age of the clast parent body and the CV3 chondrule formation age suggests that the clasts and CV3 chondrites could be originated from the same parent body with a peak temperature of 800–1100 °C. If the body has a peak temperature of >1100 °C, the accretion age of the body becomes older than the CV3 chondrule formation age and multiple CV3 parent bodies are likely.     

Validation of a chrysophyte stomatocyst‐based cold‐season climate reconstruction from high‐Alpine Lake Silvaplana,Switzerland

For the reliable assessment of past climate variability, quantitative reconstructions of seasonal temperatures are required. Currently, reconstructions of cold‐season temperatures are scarce, because most biological proxies are biased towards the growing season. Here we test the potential of chrysophyte stomatocysts (or simply ‘cysts’; siliceous resting stages of the golden‐brown algae) as a proxy for cold‐season temperature. Climate reconstructions based on biological proxies are commonly constructed using transfer functions derived from calibration in space. However, the performance of these reconstructions is rarely tested by direct comparison with meteorological data due to limitations of sample resolution or chronological control. We compare a cyst‐based near‐annual reconstruction of ‘date of spring mixing’ from the varved sediments of Lake Silvaplana (Swiss Alps) spanning AD 1870–2004 with climate variables from the same period measured at the lake shore. The high correlation between cyst‐based ‘date of spring mixing’ and cold‐season temperature demonstrates the ability of chrysophyte cysts to archive cold‐season temperature variability. Lake eutrophication, which was extensive during the last 50 years, had no obvious effect on the cyst‐based reconstruction. This study underlines the high potential of chrysophyte cysts as a quantitative proxy for cold‐season climate reconstructions. Copyright © 2011 John Wiley & Sons, Ltd.     

Hydrological effects of climate change,groundwater withdrawal,and land use in a small Korean watershed

The effects of variability in climate and watershed (groundwater withdrawal and land use) on dry‐weather streamflows were investigated using SWAT (Soil and Water Assessment Tool). The equation to predict the total runoff (TR) using climate data was derived from simulation results for 30 years by multiple regression analysis. These may be used to estimate effects of various climate variations (precipitation during the dry period, precipitation during the previous wet period, solar radiation, and maximum temperature). For example, if daily average maximum temperature increases by 3 °C, TR during the dry period will decrease by 27·9%. Similarly, groundwater withdrawals strongly affect streamflow during the dry period. However, land use changes (increasing urbanization) within the forested watershed do not appear to significantly affect TR during the dry period. Finally, a combined equation was derived that describes the relationships between the TR during the dry period and the climate, groundwater withdrawal and urban area proportion in a small monsoon watershed. This equation will be effective to predict the water availability during the dry periods in the future since it is closely related to changes of temperature, precipitation, solar radiation, urban area ratio, and groundwater withdrawal quantity. Copyright © 2007 John Wiley & Sons, Ltd.     

Transport and retention of Escherichia coli in a mixture of quartz,Al‐coated and Fe‐coated sands

Transport and retention of Escherichia coli through the mixture of quartz, Al‐coated and Fe‐coated sands was examined using column experiments to investigate the effect of geochemical heterogeneity on bacteria transport. The first set of the experiments was performed in quartz, Al‐coated and Fe‐coated sand mixtures (coated sand: 0, 5, 10, 25, 50, 100%) to examine the influence of positively‐charged sand grains on bacteria transport. The second experiments were carried out to observe the impact of pH (range 6·74–8·21) on bacteria transport in the mixture of quartz 50% and Fe‐coated sand 50%. The third experiments were conducted to analyse the effect of ionic strength (0, 50, 100, 200 mM) on bacteria transport in the mixture of quartz 50% and Al‐coated sand 50%. The first experiments show that bacterial mass recoveries were in the range of 3·6–43·4%, decreasing nonlinearly as the content of Al‐ and Fe‐coated sands increased. In the second experiments, the bacterial mass recoveries were in the range of 35·5–79·2%, increasing linearly as the solution pH increased. In the third experiments, the mass recovery was 3·4% at 0 mM. As the ionic strength increased to 50mM, the mass recovery decreased to 0%. When the ionic strength increased further to 100 and 200 mM, no bacterial mass was recovered as in the case of 50 mM. It indicates that in the mixed medium of quartz 50% and Al‐coated sand 50% both positive (increment of bacterial adhesion) and negative (decrement) effects of ionic strength may be counterbalanced, minimizing the impact of ionic strength on the bacterial adhesion. This study helps to understand the role of metal oxides and solution chemistry in the transport of bacteria in geochemically heterogeneous media Copyright © 2008 John Wiley & Sons, Ltd.     

Orbital‐ and millennial‐scale paleoceanographic changes in the north‐eastern Japan Basin,East Sea/Japan Sea during the late Quaternary

Two gravity sediment cores (GH99‐1239 and GH99‐1246) obtained from the north‐eastern Japan Basin in the East Sea/Japan Sea were analyzed for the orbital‐ and millennial‐scale paleoceanographic changes. Chronostratigraphically, core GH99‐1239 represents a continuous sedimentary record since 32 ka, based on correlation of distinct lithological markers (i.e. dark layer or TL layer) with those in core GH98‐1232 collected nearby. For core GH99‐1246, the age model is constructed through correlation of lightness (L*) values and tephra (Aso‐4 and Toya) layers with those in the well‐dated Oki Ridge core (MD01‐2407), indicating about 134 ka of sedimentation since the latest Marine Isotope Stage (MIS) 6. New geochemical data from both cores corroborate orbital‐scale paleoceanographic variation, such that surface‐water productivity, represented by biogenic opal and total organic carbon (TOC) contents, increased during MIS 1 and MIS 5; CaCO₃ contents do not show such distinct glacial–interglacial cycles, but were influenced by dissolution and preservation rather than foraminiferal production. During the glacial periods when sea ice was prevalent, surface‐water productivity was low, and bottom‐water conditions became anoxic, as indicated by high total sulfur (TS) contents and high Mo concentrations. The geochemical data further document millennial‐scale paleoceanographic variability, corresponding to a series of thin TL layers in response to Dansgaard–Oeschger cycles but irrespective of the glacial or interglacial periods. In particular, thin TL layers formed during MIS 3 are characterized by less TOC (about 1%) and TS (about 0.4%) contents and lower Mo (about 5 p.p.m.) concentration, whereas those during MIS 4 and MIS 5 exhibit more TOC (up to 4%) and TS (up to 5%) contents and higher Mo (up to 120 p.p.m.) concentration. Such a discrepancy is attributed to different degree of surface‐water productivity and of bottom‐water oxygenation, which is closely related to the sea level position and extent of ventilation. Flux of the East China Sea Coastal Water controlled by millennial‐scale paleoclimatic events is the most critical factor in deciding the properties of TL layers in the north‐eastern Japan Basin. Our results strongly confirm that TL layers in the Japan Basin also validate the unique feature of basin‐wide paleoceanographic signals in the East Sea/Japan Sea. Copyright © 2011 John Wiley & Sons, Ltd.     

High-resolution numerical simulation of the Pacific Ocean

The present study developed Pacific Ocean models from the Research Institute for Applied Mechanics Ocean Model (RIAMOM) with very high horizontal (1/6° and 1/12°) and vertical (70 levels) resolutions. The hydrographic features of the simulations show good agreement with observed climatological features. Solution differences between the 1/6° and 1/12° models are small for general features of various physical components, but large for eddy fields and the strengths of western boundary currents and their extensions. However, the two high-resolution models show realistic climatological features of Pacific Ocean circulation patterns. Volume transports through major straits in the northwestern Pacific Ocean were also simulated and compared with previous observational results.     

从UB-2孔硅藻记录看末次冰期至早全新世日本海古海洋环境

日本海南部郁陵海盆的UB-2孔沉积物硅藻记录,反映了11000—28000aBP该区古海洋和古气候的变化。对比日本海和格陵兰冰芯(GRIP)δ18O数据,UB-2孔硅藻暖水种比率及淡水—海滨种含量变化清楚地记录了氧同位素3期(MIS3)、末次盛冰期(LGM)、波令—阿勒罗德暖期(B/A)以及新仙女木冷事件(YD)等古气候事件。淡水—海滨种硅藻含量在末次盛冰期阶段明显升高及暖水种数量的显著减少,表明此时日本海为低温、低盐的古海洋环境,这可归因于气候变冷、海平面下降造成的日本海当时相对封闭的海洋环境。自15200aBP起,Paraliasulcata含量逐渐上升,这可能与海平面上升引起的古环境变化有关,可以作为对马海峡开启的标志。全球气候变化引起的海平面变化是该区域古气候变化的主要控制因素。     

Precambrian crustal evolution in Rangrim Massif,Korean Peninsula

Petrological, chronological and geotectonic geological analysis of Precambrian metamorphic rock in Korean Peninsula shows that the remnants （ 〉3.4 Ga） of continental nuclei crust were formed in the Paleoarchean in the Rangrim Massif. In the massif, the main formation ages of continental crust range from 3.2 Ga to 2.5 Ga, its important growing period was 2.8 - 2. 5 Ga. The subsequent expansion period of the Rangrim Massif was 2. 4 - 2. 2 Ga. The division events occurred in 1.85 Ga and in the Late Paleoproterozoic-Early Mesoproterozoic, respectively. Since then the massif was relatively stable. However, the last division of the Rangrim Massif occurred at 793 Ma.