Tsunami is a serious marine disaster,and accurate tsunami prediction is of great significance to marine engineering and the safety of people's lives and property.In this paper,based on 1-dimensional convolutional neural network(CONV1D),the evolution model of tsunami-like hydrodynamic characteristics of reef topography is constructed.By inputting observed values of wave heights resembling tsunami waves,the water inundation time series curves for specified locations on islands and reefs are generated.This achieves a prediction from one time series to another,serving the purpose of marine disaster prevention.The results indicate that the average relative error in predicting the arrival time of tsunami-like waves is 0.71%,and the average relative error in predicting maximum water levels is 6.99%.The hydrodynamic characteristics of island and reef terrains resembling tsunami waves obtained through CONV1D exhibit a strong alignment with numerical results.
Organic carbon burial is an important part of carbon cycle,but there are few studies on organic carbon in coral reef sediments,which affects the accurate assessment of coral reef carbon cycle.In this paper,the modern surface sediments from the outer slope of the Yongle Atoll,Xisha Islands,South China Sea,were analyzed for their total organic carbon(TOC)content,total nitrogen(TN)content,organic carbon isotope(δ13C)value,as well as sediment grain size,chlorophyll content and other indicators.The ecological condition of the outer slope of the Yongle Atoll reef is relatively good,and has the potential to represent the organic carbon characteristics in sediments of healthy coral reef ecosystems.The results showed that:1)the TOC content in the sediments from the outer slope of Yongle Atoll reef ranged from 0.71 to 1.66 mg·g-1,with an average of(1.23±0.31)mg·g-1;the TN content ranged from 0.12 to 0.28 mg·g-1,with an average of(0.20±0.05)mg·g-1.2)the C/N ratio ranged from 6.16 to 7.59,with an average of(6.75±0.34);δ13C values ranged from-17.49‰ to-15.85‰,with an average of(-16.61±0.49)‰,indicating that the organic carbon in the sediments was predominant of marine autochthonous origin and mainly from benthic plants.3)Organic carbon content was negatively correlated with water depth and positively correlated with chlorophyll a content and pheophytin content,indicating that primary productivity controlled by benthic plants was the main source of organic carbon content on the outer slope of the reef.Combined with the vertical accumulation rate of the outer reef slope sediments of the Pacific Ocean since the Holocene(2～5mm·a-1),it is inferred that the organic carbon burial flux of the outer slope of the Yongle Atoll is between 3～8g·m-2·a-1.The present study provides new information for evaluating the contribution of coral reefs in the South China Sea to the carbon cycle.
In this study,based on the field survey data of the Guangxi Shankou National Mangrove Ecological and Natural Reserve(hereinafter referred to as the Shankou Mangrove Reserve)in 2022,six time-phase remote sensing images during 1987-2021 were selected,and an object-oriented image classification method was used to analyze the status of the land-use and land-cover change(LUCC)and to calculate the landscape pattern index(LPI)based on the LUCC.This study combined LPI with LUCC to focus on exploring the wetland change process and its important influencing factors in the Guangxi Shankou Mangrove Reserve.There has been a continuous transition between land types over the past 35 years,including cultivated land continued to decrease,and Spartina alterniflora and aquaculture ponds increased,with Spartina alterniflora mainly encroaching on the former coastal mudflats,and aquaculture ponds mainly converted from forested land and cultivated land.In terms of landscape,landscape fragmentation increased,connectivity decreased,landscape shape became more complex,and landform succession became more frequent;Based on Pearson's correlation analysis,there were highly significant or significant correlations between land use change and landscape indices for coastal mudflats,mizuna mudflats,and aquaculture ponds.Significant land use changes have occurred in the Shankou Mangrove Reserve over the past 35 years,with invasive species(Spartina alterniflora)and anthropogenic disturbances(aquaculture ponds)being the main factors influencing changes in mangrove wetlands in the area,and the main contributors to the continued increase in landscape fragmentation.This study reveals the influencing factors of regional landscape changes,which can provide a theoretical basis for the environmental management and protection of typical mangrove ecosystems.
为获得具有较好抑制植物病原菌活性的化合物,对一株海洋链霉菌Streptomyces sporoverrucosus 33510的化学成分及活性进行了研究。使用高效液相色谱（high performance liquid chromatography, HPLC）、半制备液相色谱（semi-pre HPLC）、柱色谱（colume chromatography, CC）、薄层色谱（thin layer chromatography, TLC）和重结晶等分析及分离技术对该菌株的发酵产物进行了分离纯化。采用核磁共振（nuclear megnetic resonance,NMR）、质谱（mass spectra,MS）、旋光（optical rotatory dispersion,ORD）等波谱学方法对得到的化合物进行结构鉴定。通过滤纸片法对化合物进行抑菌活性检测。从33510菌株的发酵产物中共分离得到10个化合物,分别为:cyclo（D-Pro-D-Leu）（1）、bisphenol A （2）、methylp-hydroxyphenylacetate （3）、N-phenethylacetamide（4）、3-indole-methylethanoate（5）、dibutyl phthalate（6）、cyclo（D-Pro-L-Leu）（7）、cyclo（D-Pro-L-Ile）（8）、cyclo（L-Pro-L-Phe）（9）和cyclo（L-Leu-L-Val）（10）。除化合物5和9外,其他8个化合物均为首次从该菌种中分离得到。抑菌结果表明,抑菌摩尔浓度为0.19mmol·L -1 时,化合物2对板栗疫病菌（Cryphonectria parasitica）的抑制效果为高敏（抑菌直径为20mm）。
Quantifying eddy mixing in the ocean is a hot and tough problem in the area of physical oceanography.Based on the theory of effective diffusivity,the present study investigated the stirring effects of geostrophic turbulence that led to stretching,distorting,deforming,and folding of tracer contours.These changes are then related to the efficiency of turbulent mixing.Results show that under the stirring effect of geostrophic turbulence,the length of tracer contour can be quickly elongated and fine-scale tracer filaments and fronts are also generated.This fractal elongation of tracer contour,about 10～20 times longer than the original length,is the dominant contributor to the mixing efficiency,whereas the gradient enhancement associated with filament and front generations only plays a secondary role.On the other hand,fine-scale features are smoothed out by small-scale diffusivity which eventually suppresses the increase of contour length and the generation of tracer filaments.This imposes an upper bound of the mixing efficiency when the stirring and smoothing effects are in a dynamical balance.Through a'box-counting'method,the fractal dimension of tracer contour is also found between 1.4～1.6,indicating a geometric dimension lies somewhere between 1D and 2D.Due to the limitation of data resolution,contour length and thus mixing efficiency may be underestimated.Finally,the present study made an empirical relation between the fractal dimension and mixing efficiency,providing an opportunity for estimating mixing efficiency through a well-developed pattern recognition technique in remote sensing,and a new way of diagnosing ocean mixing and its parameterization.
