Lithostructural controls in Douala-Buea Region landscape(SW Cameroon margin): Insights from morphometric analysis

The Douala-Buea Region(DBR;4°-5°N,9°-10°30’E),a portion of the southern Cameroon passive margin,developed on the Proterozoic granito-gneissic basement and the Cretaceous to Recent volcanosedimentary cover,was explored in order to evaluate the lithology and tectonics controls on its landscape usingthequalitativeandquantitative geomorphological analyses based on 30 m resolution Digital Elevation Models(DEM)and field evidences.This area displays an uneven and complex landscape differentiated into four morphological units:Douala,Nkondjock,Kumba and Buea Units.The Douala Unit corresponds to the Coastal Plain and is extended on the Douala-Kribi/Camposedimentarybasin.The Nkondjock Unit represents a middle plateau developed on a Proterozoic granito-gneissic basement.The Kumba Unit matches with the southernmost volcanic Western Cameroon High Plateau.The Buea Unit corresponds to the Mount Cameroon stratovolcano.The relief analysis through mountain-front sinuosity(Smf,1.19–1.43)and relative relief ratio(Rr,0.10–2.31)vary from one unit to another.The drainage network analysis including drainage patterns,stepped longitudinalriverprofiles,theassociated morphometric indexes,notably the concavity index(IC,0.56–0.88),deviation(D,267–2912 m),basin asymmetry factor(A_F,6.37–42.12),hypsometric integral(HI,0.10–0.29),valley floor width to valley height ratio(V_f,0.36–2.75),elongation ratio(R_e,0.30–0.50),watershed slope(S,6.88–88.88)and stream length gradient index(SL,0–3332)vary from one basin to another too.These results also show the heterogeneous and uneven DBR landscape controlled by its lithology and active tectonics.The drainage system reveals concave to concavo-convex longitudinal river profile shapes with knick points,asymmetric basins,and fault reactivations,and highlights the tectonics activity that used to occur through the time and their control on the morphology.Together,they document the lithostructural controls on the DBR landscape evolution,extendable in the whole SW Cameroon margin.     

Comprehensive analysis of glacier recession(2000-2020) in the Nun-Kun Group of Glaciers,Northwestern Himalaya

Himalayan glaciers are shrinking rapidly, especially after 2000. Glacier shrinkage, however, shows a differential pattern in space and time, emphasizing the need to monitor and assess glacier changes at a larger scale. In this study, changes of 48 glaciers situated around the twin peaks of the Nun and Kun mountains in the northwestern Himalaya, hereafter referred to as Nun-Kun Group of Glaciers(NKGG), were investigated using Landsat satellite data during 2000-2020. Changes in glacier area, snout...     

Ring-morphostructures of the Amur-Songhua-Huanghe lineament (eastern margin of Asia)

1GIGANTICRING-MORPHOSTRUCTURESOFAMUR-SONGHUA-HUANGHELINEAMENT(ASHL)Thereareaseriesofgiganticring-morphostructure(RM)alongthemarginofcontinentwithdiameterfrom1-2to3-4thousandkilometers.ASHLcrossthenextmega-RMontheeasternmarginofAsia:Amur,Korean,EastChinaandtheSeaofOkhotsk.TheAmurmega-RMismorethan2500kmindiameterandcoversthewholebasinoftheAmurRiveraswellasseriesofsmallbasinsconnectedwiththeSeasofOkhotskandJapan.Theconformaldistributionofthe“steps”ofthicknessear…     

Empirical Analysis of City Contact in Zhujiang （Pearl） River Delta,China

In traditional urban geography, city contact research is a classic study element in city research. In general, researchers use the traditional gravity model to characterize the contacts that exist between two cities. The traditional gravity model assumes ideal condi- tions, but these preconditions and their results often do not exist in realistic conditions. Thus, we used a modified gravity model to char- acterize the city contacts within a specific region. This model considers factors such as intercity complementarities, government inter- vention, and the diversity of the transportation infrastructure which is characterized as the transportation distance instead of the tradi- tional Euclidean distance. We applied this model to an empirical study of city contact in the Zhujiang （Pearl） River Delta （PRD） of China. The regression results indicated that the modified gravity model could measure city contact more accurately and comprehen- sively than the traditional gravity model, i.e., it yielded a higher adjusted R2 value （0.379） than the traditional gravity model result （0.259）. Our study also suggests that, in addition to urban-regional and metropolitan development, the complementarities of the basic functions of cities at the administrative and market levels, as well as the corporeal and immaterial levels, play very significant roles in the characterization of city contact. Given the complexity of city contact, it will be necessary to consider more relevant influential fac- tors in the modified gravity model to characterize the features of city contact in the future.     

Crustal structure revealed by a deep seismic sounding profile of Baijing-Gaoming-Jinwan in the Pearl River Delta

The Pearl River Estuary area, located in the middle part of the southern China coastal seismic belt, has long been considered a potential source of strong earthquakes above magnitude 7.0. To scientifically assess the potential strong earthquake risk in this area, a three-dimensional artificial seismic sounding experiment, consisting of a receiving array and seabed seismograph, was performed to reveal the deep crustal structure in this region. We used artificial ship-borne air-gun excitation shots as sources, and fixed and mobile stations as receivers to record seismic data from May to August 2015. This paper presents results along a line from the western side of the Pearl River Estuary to the western side of the Baijing-Gaoming-Jinwan profile. A two-dimensional velocity structure was constructed using seismic travel-time tomography. The inversion results show that the Moho depth is 27 km in the coastal area and 30 km in the northwest of the Pearl River Estuary area, indicating that the crust thins from land to sea. Two structural discontinuities and multiple low-velocity anomalies appear in the crustal section. Inside both discontinuity zones, a low-velocity layer, with a minimum velocity of 6.05 km s~(-1), exists at a depth of about 15 km, and another, with a minimum velocity of 6.37 km s~(-1), exists at a depth of about 21.5 km between the middle and lower crust. These low velocities suggest that the discontinuities may consist of partly molten material. Earthquakes with magnitudes higher than 5.0 occurred in the low-velocity layer along the profile. The deep Kaiping-Enping fault, rooted in the crust, may be one of the most important channels for deep material upwelling and is related to tectonic movement since the Cretaceous in the Pearl River Delta tectonic rift basin.     

Intraspecific morphometric diversity of barramundi (Lates calcariferBloch, 1790) in the waters of southern Bangladesh

A total of 160 barramundi's(Lates calcarifer Bloch,1790)sampled from four rivers(Tentulia,Balaswar,Bakkhali,and Andarmanik)along the southern coastal region of Bangladesh were investigated in terms of morphometric characters to reveal the intraspecific variation.Twenty-five morphometric measurements were extracted using the conventional method and subjected to multivariate analyses(i.e.,principal component analysis(PCA),discriminate function analysis(DFA),cluster analysis(CA))to distinguish individuals from different rivers.The result demonstrated that twenty-two out of 2 5 measurements was statistically significant(Univariate ANOVA)among all four populations.PCA analy sis of morphometric characters resulted in two principal components,PC I and PCII which accounted for 79.25%and 4.28%of the total data variance.PC I-PC Ⅱ plot explained 83.5 3%of total variance differentiated the population of L.calcarifer into two groups.Discriminate analysis correctly classified about 88.1%of the examined fish into the four areas.The UPGMA dendrogram showed that Bakkhali populations were the most morphologically different populations in comparison to other populations,while Andarmanik and Balaswar populations were very close to each other.The strong morphometric variation between Bakkhali and Tentulia,Andarmanik and Balaswar was observed in the present study,suggested the evidence of the separate stock population of barramundi in these locations,which might require distinct stock management strategies for resource sustainability in the waters of southern Bangladesh.However,if these findings are supported by further molecular markers and geometric morphometry,this would be a strong indication of different stocks of this population in the four rivers of southern Bangladesh.     

The effect of salinity on Fucus ceranoides (Ochrophyta,Phaeophyceae) in the Mondego River (Portugal)

Algae(and their extracts) are increasingly important for pharmaceutical applications due to the diversity of useful compounds they contain. The genus Fucus contains one of the most studied species,Fucus vesiculosus. The species F. ceranoides differs from the others of the genus by presenting longitudinal air-vesicles and a capacity to survive at low salinities. It is an alga that inhabits the Mondego River estuary(Portugal), at the southern limit of its distribution, and can serve as a role model to understand the effect of a salt gradient on the production of bioactive compounds. We assessed the phenolic content and antioxidant activity of different F. ceranoides extracts(e.g. methanolic, aqueous and polysaccharide) prepared from samples harvested from two different zones to evaluate if the adaptation of F. ceranoides to different salinity levels influenced its chemical composition. The antioxidant activity of the extracts was determined using 1,2-diphenyl-picrylhydrazyl(DPPH) and 2.2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS)radicals. These assays demonstrated that the methanolic extract of lyophilized F. ceranoides that grew at low salinities was the most bioactive, i.e. DPPH(IC_(50)=50.39 μg/mL) and ABTS(TEAC=2.42). The total phenolic content(Folin-Ciocalteu method) and the methanolic extract of the lyophilized F. ceranoides collected from a low salinity habitat exhibited the highest phenolic content(PGE=49.48 μg/mg of lyophilized extract)amongst those sampled. Thin layer chromatography(TLC) and Fourier transform infrared spectroscopy(FTIR) were used for the identification of compounds in the extracts. This characterization allowed confirmation that the various extracts contained almost the same compounds but with notable quantitative differences. Based on these results, we conclude that there were differences in the quantity of the compounds due to the effect of salinity. The drying methods used were also found to have influenced the quality of the extracted compounds.     

Metabolic and phylogenetic profile of bacterial community in Guishan coastal water (Pearl River Estuary), South China Sea

Characteristics of a microbial community are important as they indicate the status of aquatic ecosystems. In the present study, the metabolic and phylogenetic profile of the bacterioplankton community in Guishan coastal water(Pearl River Estuary), South China Sea, at 12 sites(S1–S12) were explored by community-level physiological profiling(CLPP) with BIOLOG Eco-plate and denaturing gradient gel electrophoresis(DGGE). Our results showed that the core mariculture area(S6, S7 and S8) and the sites associating with human activity and sewage discharge(S11 and S12) had higher microbial metabolic capability and bacterial community diversity than others(S1–5, S9–10). Especially, the diversity index of S11 and S12 calculated from both CLPP and DGGE data(H 3.2) was higher than that of others as sewage discharge may increase water nitrogen and phosphorus nutrient. The bacterial community structure of S6, S8, S11 and S12 was greatly influenced by total phosphorous, salinity and total nitrogen. Based on DGGE fingerprinting, proteobacteria, especially γ- and α-proteobacteria, were found dominant at all sites. In conclusion, the aquaculture area and wharf had high microbial metabolic capability. The structure and composition of bacterial community were closely related to the level of phosphorus, salinity and nitrogen.     

Assessment of trophic status in Changjiang （Yangtze） River estuary

The integrated methodology for the assessment of estuarine trophic status (ASSETS), which was extended and refined from the United States National Estuarine Eutrophication Assessment (NEEA), is a multi-parameter assessment system and has been widely used in eutrophication assessment in estuarine and coastal waters. The ASSETS was applied to evaluate the trophic status of the Changjiang (Yangtze) River estuary, one of the largest estuaries in the world. The following main results were obtained: (i) The estuarine export potential is "moderate susceptibility" due to the "moderate" dilution potential and "moderate" flushing potential; (ii) The overall human influence (OHI) index classified the impact of nutrients in the system as "high" due to the high level of nutrient discharge by the river which channels anthropogenic impacts in the catchments to the estuarine system; (iii) The overall eutrophic condition (OEC) in the estuary was classified into the "high" category due to frequent occurrence of nuisance and toxic algal blooms in the mixing and seawater zones; (iv) Since the nutrient loadings (e.g., DIN) in the river is expected to continue to increase in the near future following the population increase and rapid economic growth throughout the drainage basin, the nutrient-related symptoms in the estuary are likely to substantially worsen, which leads to the "worsen high" category for the definition of future outlook (DFO). The combinations of the three components (i.e., OHI, OEC, and DFO) lead to an overall grade as "bad" for the trophic status in the Changjiang River estuary.     

Climatic variations in the coastal zone — Comparison between the Po River delta (Adriatic Sea,Italy) and the Huanghe River delta (Bohai Sea,China)

The aim of this work is to research the influence of natural climatic changes on the evolution of the coastal zone in modern times and the possible implication of human activities on the configuration of the present coastline. Comparison of data of two very far and different areas, the Po River delta, Adriatic Sea and the Huanghe River delta, Bohai Sea, reveals the planetary diffusion of climatic fluctuations and their effects on coastal evolution. Contribution No. 820 from the Marine Geology Institute, C. N. R., Italy. Contribution No.2207 from the Institute of Oceanology, Academia Sinica. Project supported by the National Natural Science Foundation of China.     

印度尼西亚苏门答腊岛浅成低温热液型金(银)矿产资源总量预测

苏门答腊岛位于印度尼西亚西缘，是环太平洋成矿带的重要组成部分，拥有丰富的铜、金、铅、锌等金属矿产资源，对其资源总量进行评价可以为国家"一带一路"战略决策提供基础数据。在对该区进行野外调查和1:100万低密度地球化学调查的基础上，分析了小比例尺尺度下浅成低温热液型金（银）矿床的地质特征、关键控矿因素和找矿标志，构建了该类金（银）矿床的预测模型；认为该区NW向苏门答腊大断裂及其次级断裂与新生代岛弧岩浆岩具有密切的时空耦合关系，该断裂系统和新生代岩浆岩共同控制浅成低温热液型金（银）矿床的产出；已知金（银）矿床点和1:100万低密度地球化学异常可以作为快速圈定研究区有利找矿地段的标志；并据此圈定成矿远景区5个，其中A级成矿远景区3处，B级成矿远景区2处；然后，利用通用密度模型预测了不同概率下的各远景区未知矿床数，并运用蒙特卡罗模拟预测了苏门答腊岛浅成低温热液型金（银）矿产在不同概率下的金（银）资源量。      

松辽盆地东南缘西丁家地区营城组沉积相分析

松辽盆地东南缘深层沉积相研究程度较浅,以西丁家地区营城组为例,利用岩心观察描述结果,结合测井、地震资料,以及区域构造演化和沉积相分析结果,研究松辽盆地东南缘深层地层沉积相.结果表明:营城组(K1y)主要发育扇三角洲、辫状河三角洲、湖底扇和湖泊4种相类型,其中辫状河三角洲相和湖泊相最为发育;西丁家地区营城组主要表现为"广盆浅水"沉积特征,西南陡坡带发育扇三角洲沉积体系,北部斜坡带发育辫状河三角洲沉积体系,垂向上地层叠加样式表现为由进积向加积演变.该研究结论对西丁家地区深层地层下一步勘探开发及资源评价具有指导意义.     

Late Pleistocene environmental information on the Diexi paleo-dammed lake of the upper Minjiang River in the eastern margin of the Tibetan Plateau,China

In 1999, Diexi paleo-dammed lake(2349 m a.s.l.) was discovered around Diexi town along the Minjiang River in Sichuan province. Diexi is located where the eastern edge of the Tibetan Plateau and the Sichuan Basin meet. The dammed lake was formed during the Last Glacial Maximum of the Late Pleistocene(~30,000 years ago) and began to empty about 15,000 years ago. The lacustrine sediments(up to 240 m thick) preserve abundant paleoenvironment information. In this paper, a mass of oxygen isotopes and 14 C dating from drilled cores are analyzed and discussed. The δ18 O curve on the paleo climate from this section is comparable with the coeval paleo climatic curves of ice cores and karsts in China and others. Furthermore, the physical model testing has confirmed that the disturbed zones in the core are caused by strong earthquakes occurred at least 10 times, which implies strong crustal deformation, as an important driving force, affecting climate change. This study provides a new window to observe East Asian monsoon formation, paleoenvironmental evolution and the global climate change.     

Simulated circulations off the Changjiang （Yangtze） River mouthin spring and autumn

The circulations off the Changjiang mouth in May and November were simulatedby a three dimension numerical model with monthly averaged parameters of dynamic factors in this paper. The area covers the East China Sea (ECS), Yellow Sea and Bohai Sea. Simulated results show that the circulation off the Changjiang mouth in spring and autumn is mainly the Changjiang runoff and Taiwan Warm Current (TWC). The Changjlang discharge is much larger in May than in November, and the wind is westward in May, and southward in November offthe Changjiang mouth. The runoff in May branches in three parts, one eastward flows, the other two flow northward and southward along the Subei and Zhejiang coast respectively. The Changjiang diluted water expands eastward off the mouth, and forms a strong salinity front near the mouth. Surface circulation in autumn is similar to that in winter, the runoff southward flows along the coast, and the northward flowing TWC becomes weaker compared to that in spring and summer. The bottom circulations in May and November are mainly the runoff near the mouth and the TWC off the mouth, and the runoff and TWC are greater in May than in November.     

黄河（山东段）悬河稳定性评价

通过黄河（山东段）悬河稳定性影响因素分析,各河段都有决口失稳的可能。该文从区域地壳稳定性、堤基稳定性、河道稳定性3个方面,采用模糊数学综合评判法进行悬河稳定性评价,对河段可能出现的失稳或决口险点及其可能造成的危害性进行分析和预测,初步确定了10处地质险段。     

Nutrients in seawater and interstitial water of the sediments in the Huanghe River estuarine area (November)

The investigation shows that the concentrations of nutrients are high in estuarine and coastal waters and low in offshore waters. The concentration of nitrate in estuaries is controlled through a physical mixing process and is also affected by biotic activity. The annual transport of total inorganic nitrogen and dissolved phosphate-phosphorus from the Huanghe River water to the sea is about 8.45 ×10⁴ and 1.45×10³ tons respectively. The distributions of inorganic nitrogen and silicate in interstitial water of surface sediments are similar to those in surface and bottom seawater. Their contents in interstitial water are 227–552 μmol/l (average375) for ammonia, 0.31–9.0 μmol/l (average 1.6) for nitrite, 0–41 μmol/l (average6.0) for nitrate, and 41–139 μmol/l (average 77) for silicate. The average concentrations of phosphate in the surveyed area are 0.64 μmol/l for seawater and 1.2 μmol/l for interstitial water. A cycle of phosphate in the estuary is also suggested in this paper. Contribution No. 1434 from Institute of Oceanology, Academia Sinica.     

Simulating the responses of a low-trophic ecosystem in the East China Sea to decadal changes in nutrient load from the Changjiang(Yangtze) River

Using a three-dimensional coupled biophysical model,we simulated the responses of a lowtrophic ecosystem in the East China Sea(ECS)to long-term changes in nutrient load from the Changjiang(Yangtze)River over the period of 1960–2005.Two major factors aff ected changes in nutrient load:changes in river discharge and the concentration of nutrients in the river water.Increasing or decreasing Changjiang discharge induced different responses in the concentrations of nutrients,phytoplankton,and detritus in the ECS.Changes in dissolved inorganic nitrogen(DIN),silicate(SIL),phytoplankton,and detritus could be identified over a large area of the ECS shelf,but changes in dissolved inorganic phosphate(DIP)were limited to a small area close to the river mouth.The high DIN:DIP and SIL:DIP ratios in the river water were likely associated with the diff erent responses in DIN,DIP,and SIL.As DIP is a candidate limiting nutrient,perturbations in DIP resulting from changes in the Changjiang discharge are quickly consumed through primary production.It is interesting that an increase in the Changjiang discharge did not always lead to an increase in phytoplankton levels in the ECS.Phytoplankton decreases could be found in some areas close to the river mouth.A likely cause of the reduction in phytoplankton was a change in the hydrodynamic field associated with the river plume,although the present model is not suitable for examining the possibility in detail.Increases in DIN and DIP concentrations in the river water primarily led to increases in DIN,DIP,phytoplankton,and detritus levels in the ECS,whereas decreases in the SIL concentration in river water led to lower SIL concentrations in the ECS,indicating that SIL is not a limiting nutrient for photosynthesis,based on our model results from 1960 to 2005.In both of the above-mentioned cases,the sediment accumulation rate of detritus exhibited a large spatial variation near the river mouth,suggesting that core sample data should be carefully interpreted.     

黄河下游(山东段)主要生态环境地质问题及对策

在收集分析大量最新资料基础上,阐述了黄河下游(山东段)存在的水质污染、地下水资源短缺,以及地面沉降、地裂缝、地面塌陷、砂土液化、土壤盐渍化、黄河堤防河道稳定性等主要生态环境地质问题,并提出了区内主要生态环境地质问题的防治对策,这对黄河下游(山东段)国土资源开发、防灾、黄河"治黄"与防洪减灾、地质生态环境保护及管理等,具有较高的参考价值。     

Life history pattern of mosquitofish Gambusia holbrooki (Girard, 1859) in the Tajan River (Southern Caspian Sea to Iran)

Investigation of the ecology of introduced species in new habitats can allow determinations of the degree, direction, and rate of evolutionary change. The introduction of Gambusia holbrooki in the southern Caspian Sea presents such a situation. We evaluated the life history traits of mosquitofish in the Tajan River basin. A total of 744 G. holbrooki specimens were collected between January and December 2008. The maximum observed ages are 0+ years for males and 1+ years for females. Both sexes grew allometrically (negative for males: b=2.442 and positive for females: b=3.232). The overall sex ratio is unbalanced and dominated by females. GSI values suggest that this population of G. holbrooki matures between February–July. The highest mean GSI value is 1.80 for males and 15.97 for females in May. Egg diameter ranges from 1.00 to 3.00 mm with a mean value of 2.098 mm. Absolute fecundity varied from 7 to 57 eggs. Both ova diameter and absolute fecundity were positively correlated to fish size (length and weight). Fecundity relative to total weight fluctuated from 34.44 to 582.64 eggs/g, and to total length from 2.33 to 12.95 eggs/cm. Both were negatively correlated with female size. The characteristics of this population are important with respect to life history of the species.     

The distribution and variation of elements in sediments off the Huanghe (Yellow) River mouth

Surface sediment samples collected off the Huanghe (Yellow) River mouth during the period 2007–2009 were analyzed for major and trace element concentrations. Concentrations of 16 elements were measured using X-ray fluorescence spectrometry. Results demonstrate that sediment grain size is the dominant factor controlling the spatial variations of elemental concentrations. Correlation and cluster analyses allowed classification of the study area into four geochemical regions: Regions I and III are characterized by high concentrations of Al₂O₃, Fe₂O₃, MgO, Na₂O, K₂O, Cr, Cu, Mn, Ni, Pb, V, and Zn, and contain fine-grained sediments with mean grain size (M _z)<22 μm; and; Regions II and IV contain mostly coarse-grained sediments, and are characterized by high concentrations of SiO₂, Na₂O, and Zr. The sediment entering the sea from the Huanghe River and its tributaries is enriched in Ca. Thus, the Ca/Al ratio was used as an indicator of the proportion of sediments in the study area that originated from the Huanghe River. Ca/Al ratios decrease from Regions I and II (located in the nearshore zone of the Huanghe River delta) to Regions III and IV (distributed in the offshore zone of the northern Huanghe River delta, southern and southeastern Laizhou Bay area).