Temporal variations in phytoplankton biomass over the past 150 years in the western Seto Inland Sea, Japan

2016 ◽  
Vol 73 (3) ◽  
pp. 309-320
Author(s):  
Narumi K. Tsugeki ◽  
Michinobu Kuwae ◽  
Yukinori Tani ◽  
Xinyu Guo ◽  
Koji Omori ◽  
...  
Author(s):  
A. L. Rice ◽  
D. S. M. Billett ◽  
J. Fry ◽  
A. W. G. John ◽  
R. S. Lampitt ◽  
...  

SynopsisEvidence has accumulated over the past twenty years to suggest that the deep-sea environment is not as constant as was at one time thought, but exhibits temporal variations related to the seasonally in the overlying surface waters. Recent results from deep-moored sediment traps suggest that this coupling is mediated through the sedimentation of organic material, while observations in the Porcupine Seabight indicate that in this region, at least, there is a major and rapid seasonal deposition of aggregated phytodetritus to the sea-floor at slope and abyssal depths.This paper summarises the results of the Porcupine Seabight studies over the past five years or so, using time-lapse sea-bed photography and microscopic, microbiological and chemical analyses of samples of phytodetritus and of the underlying sediment. The data are to some extent equivocal, but they suggest that the seasonal deposition is a regular and dramatic phenomenon and that the material undergoes relatively little degradation during its passage through the water column. The mechanisms leading to the aggregation of the phytodetritus have not been identified, and it is not yet known whether the phenomenon is geographically widespread nor whether it is of significance to the deep-living mid-water and benthic communities.


PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12365
Author(s):  
Xiang Li ◽  
Hui Lu ◽  
Zhaokang Zhang ◽  
Wei Xing

In China, historical documents have recorded large quantities of information related to natural disasters, and these disasters have had long-lasting effects on economic and social activities. Understanding the occurrence of the natural disasters and their spatio-temporal variation characters is crucial for sustainable of our society. Therefore, based on the collection and collation of historical documents, and adopting mathematical statistics, Kriging interpolation, correlation analysis and other methods, we systematically explored the meteorological disasters in Henan Province during the past two millennia in analyzing their spatio-temporal distribution characters and driving forces. The results demonstrate that there were five major types of meteorological disasters in Henan Province, including drought, flood, hails, low temperature and frost and insect pests, which presented obvious spatio-temporal variations and have occurred frequently during the past two millennia. According to the historical documents, the major meteorological disasters occurred 1,929 times in Henan from 221 BCE to 2000 CE. On the whole, the disaster frequency show that the occurrence cycle of the meteorological disasters has obvious changes, which mainly occurred in the middle and late stages during the past two millennia, especially after 1300 CE. Furthermore, we also find that the variation of meteorological disaster events is consistent with the variation of temperature in eastern China and the frequency of meteorological disaster increases in the cold period, but decreases in the warm period. In addition, there are obvious differences in the spatial distribution of the major meteorological disaster, which were mainly distributed in the northwest and southern part region of the Henan Province before 1911 CE. While after 1911 CE, the northern and southeastern parts were the meteorological disaster-prone areas in this region during this period. Spatial correlation analysis of each meteorological disaster before and after 1911 CE points out the droughts disaster frequency-occurring district has transferred in different periods, while the hail and low temperature and frost disasters just have a smaller transferred during these two periods. Conversely, the frequency-occurring districts of floods and insect pest disasters have no obviously transferred in different periods. These results can provide an important scientific basis for governmental decision makers and local people to prevent and mitigate meteorological disaster in the future.


Geology ◽  
2019 ◽  
Vol 48 (2) ◽  
pp. 159-163 ◽  
Author(s):  
Luc S. Doucet ◽  
Zheng-Xiang Li ◽  
Richard E. Ernst ◽  
Uwe Kirscher ◽  
Hamed Gamal El Dien ◽  
...  

Abstract The most dominant features in the present-day lower mantle are the two antipodal African and Pacific large low-shear-velocity provinces (LLSVPs). How and when these two structures formed, and whether they are fixed and long lived through Earth history or dynamic and linked to the supercontinent cycles, remain first-order geodynamic questions. Hotspots and large igneous provinces (LIPs) are mostly generated above LLSVPs, and it is widely accepted that the African LLSVP existed by at least ca. 200 Ma beneath the supercontinent Pangea. Whereas the continental LIP record has been used to decipher the spatial and temporal variations of plume activity under the continents, plume records of the oceanic realm before ca. 170 Ma are mostly missing due to oceanic subduction. Here, we present the first compilation of an Oceanic Large Igneous Provinces database (O-LIPdb), which represents the preserved oceanic LIP and oceanic island basalt occurrences preserved in ophiolites. Using this database, we are able to reconstruct and compare the record of mantle plume activity in both the continental and oceanic realms for the past 2 b.y., spanning three supercontinent cycles. Time-series analysis reveals hints of similar cyclicity of the plume activity in the continent and oceanic realms, both exhibiting a periodicity of ∼500 m.y. that is comparable to the supercontinent cycle, albeit with a slight phase delay. Our results argue for dynamic LLSVPs where the supercontinent cycle and global subduction geometry control the formation and locations of the plumes.


2012 ◽  
Vol 8 (S294) ◽  
pp. 85-86
Author(s):  
Susanta Kumar Bisoi ◽  
P. Janardhan

AbstractEmploying wavelet and Fourier methods, we investigate temporal variations of periodicities in the photospheric fields obtained from synoptic magnetograms of the National Solar Observatory at Kitt Peak (NSO/KP) spanning the years 1975-2009. A north-south asymmetry is noticed in the periodicities of photospheric fields in the latitude range, 45°-78°, when the data is grouped into fields prior to and after 1996. This asymmetry when coupled with the fact that both solar fields in the latitude range, 45°-78°, and the micro-turbulence levels in the inner heliosphere began declining ~ 1995-1996 suggests that active changes occurred in the underlying basic solar processes which eventually initiated, at the end of solar cycle 23, the build-up of the deepest solar minimum, in the past 100 years.


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