Laboratory study of the nonlinear transformation of irregular waves over a mild slope   总被引：1，自引：0，他引：1  

于博  马玉祥  马小舟  董国海 《中国海洋工程》2014,28(4):489-500

This paper considers the nonlinear transformation of irregular waves propagating over a mild slope （1：40）. Two cases of irregular waves, which are mechanically generated based on JONSWAP spectra, are used for this purpose. The results indicate that the wave heights obey the Rayleigh distribution at the offshore location; however, in the shoaling region, the heights of the largest waves are underestimated by the theoretical distributions. In the surf zone, the wave heights can be approximated by the composite Weibull distribution. In addition, the nonlinear phase coupling within the irregular waves is investigated by the wavelet-based bicoherence. The bicoherence spectra reflect that the number of frequency modes participating in the phase coupling increases with the decreasing water depth, as does the degree of phase coupling. After the incipient breaking, even though the degree of phase coupling decreases, a great number of higher harmonic wave modes are also involved in nonlinear interactions. Moreover, the summed bicoherence indicates that the frequency mode related to the strongest local nonlinear interactions shifts to higher harmonics with the decreasing water depth.  相似文献   

Fragmentation Patterns in Land Reform Settlements in the Brazilian Amazon     

Chuyuan Wang 《社会与自然资源》2014,27(7):742-758

Direct action land reform (DALR) and settlement formation are new drivers of deforestation in the Brazilian Amazon. However, until now no research has paid attention to fragmentation patterns and the social processes that lead to them. This article analyzes two types of settlements, spontaneous and social movement organization-led settlements. The study uses neutral landscape models (NLMs) to compare simulated landscapes with the real fragmentation patterns found in DALR settlements. In sequence, the article uses landscape metrics to analyze the temporal and spatial dynamics of fragmentation patterns in these two types of DALR settlements. Results showed that there are significant differences between real landscape patterns and simulated landscapes using NLMs. In other words, human interferences did play a significant role in shaping deforestation patches in DALR settlements. Our metric results revealed a process in which deforestation patch mean area, shape complexity, and physical connectedness increase over time.  相似文献   

Kelp gulls prey on the eyes of juvenile Cape fur seals in Namibia     

AJ Gallagher  ER Staaterman  N Dreyer 《African Journal of Marine Science》2015,37(3):411-414

The kelp gull Larus dominicanus is an abundant and highly successful avian predator and scavenger that breeds along the coastline in the Southern Hemisphere, ranging from Antarctica to the tropics. On account of its dietary breadth, wide-ranging foraging strategies, and acclimation to modified landscapes, this species has received considerable attention within the seabird literature over the past 40 years. Furthermore, owing to its ready habituation to human-dominated environments, the species has been used as a bio-indicator of habitat modification. Here we describe new predatory behaviours of the kelp gull on a larger-bodied sympatric mammal species, the Cape fur seal Arctocephalus pusillus pusillus, along the coast of Namibia, and discuss our findings as they relate to food web dynamics and behavioural plasticity.  相似文献   

Intraguild predation and partial consumption of blue sharks Prionace glauca by Cape fur seals Arctocephalus pusillus pusillus     

C Fallows  N Hammerschlag 《African Journal of Marine Science》2015,37(1):125-128

The top-down effects of predators on ecosystem structure and dynamics have been studied increasingly. However, the nature and consequence of trophic interactions between upper-trophic-level predators have received considerably less attention. This is especially the case in marine systems due to the inherent challenges of studying highly mobile marine species. Here we describe the first documentation of asymmetrical intraguild predation by a pinniped predator on a mid-sized predatory shark. The report is based on direct observations in South African waters, in which free-swimming blue sharks Prionace glauca were captured and partially consumed by Cape fur seals Arctocephalus pusillus pusillus. These observations are important not just for understanding the interactions between these two species but more broadly for their implications in understanding the trophic ecology of pinnipeds, many populations of which have increased while numerous shark populations have declined.  相似文献   

Habitat use patterns of the invasive red lionfish Pterois volitans: a comparison between mangrove and reef systems in San Salvador,Bahamas          下载免费PDF全文

Catalina Pimiento  James C. Nifong  Margaret E. Hunter  Eric Monaco  Brian R. Silliman 《Marine Ecology》2015,36(1):28-37

The Indo‐Pacific red lionfish Pterois volitans is widespread both in its native and its non‐native habitats. The rapid invasion of this top predator has had a marked negative effect on fish populations in the Western Atlantic and the Caribbean. It is now well documented that lionfish are invading many tropical and sub‐tropical habitats. However, there are fewer data available on the change in lionfish abundance over time and the variation of body size and diet across habitats. A recent study in San Salvador, Bahamas, found body size differences between individuals from mangrove and reef systems. That study further suggested that ontogenetic investigation of habitat use patterns could help clarify whether lionfish are using the mangrove areas of San Salvador as nurseries. The aim of the present study is to determine temporal trends in lionfish relative abundance in mangrove and reef systems in San Salvador, and to further assess whether there is evidence suggesting an ontogenetic shift from mangroves to reef areas. Accordingly, we collected lionfish from mangrove and reef habitats and calculated catch per unit effort (a proxy for relative abundance), compared body size distributions across these two systems, and employed a combination of stable isotope, stomach content, and genetic analyses of prey, to evaluate differences in lionfish trophic interactions and habitat use patterns. Our results show that populations may have increased in San Salvador during the last 4 years, and that there is a strong similarity in body size between habitats, stark differences in prey items, and no apparent overlap in the use of habitat and/or food resources. These results suggest that there is not evidence an for ontogenetic shift from mangroves to reefs, and support other studies that propose lionfish are opportunistic forages with little movement across habitats.  相似文献   

The ocean and climate change policy     

Grantly Galland  Ellycia Harrould-Kolieb  Dorothée Herr 《Climate Policy》2013,13(6):764-771

The ocean plays a major role in regulating Earth's climate system, and is highly vulnerable to climate change, but continues to receive little attention in the ongoing policymaking designed to mitigate and adapt to global climate change. There are numerous ways to consider the ocean more significantly when developing these policies, several of which offer the co-benefits of biodiversity protection and support of marine-dependent human communities. When developing forward-thinking climate change policy, it is important to understand the ways that the ocean contributes to global climate and to fully inventory the services that the ocean provides to humans. Without more inclusive consideration of the ocean in climate policy, at all levels of governance, policy makers risk weaker than necessary mitigation and adaptation strategies.  相似文献   

非静压水波模型研究综述     

马玉祥  艾丛芳  董国海 《海洋与湖沼》2022,53(4):813-821

水波数值模拟一直是水利、海岸、海洋工程和物理海洋等学科关注的重要研究领域之一。在诸多的水波模型之中,非静压水波模型以其计算精度和效率较为平衡的特点受到青睐。非静压水波模型经过近三十年的发展,为科学研究、工程设计分析和海洋资源开发等提供了重要的技术手段。然而,如何开发更为高效的非静压模型,拓宽模型的应用领域一直是研究的主要研究方向。文章综述了非静压模型概念的提出以及数值开发的难点,介绍了非静压模型在波浪传播演化和波浪与结构物相互作用这两方面的应用进展,将有助于研究者了解非静压水波模型的研究和应用现状。  相似文献   

Foraging Behavior, Direct Interference and Habitat Use in Three Species of Flamingos (Phoenicopterus Chilensis, Phoenicoparrus Andinus and Phoenicoparrus Jamesi) in Mar Chiquita Lagoon, Córdoba, Argentina     

Lucila CASTRO  Ricardo TORRES 《《地质学报》英文版》2014,88(Z1):63-64

正The Laguna Mar Chiquita,located northeast of the province of Córdoba in Argentina,is the only non-Andean place where three flamingo species regularly coexist in the southern part of South America.Two of these species,  相似文献   

亚洲地区的流域—海岸相互作用：APN近期研究动态   总被引：1，自引：0，他引：1  

高抒 《地球科学进展》2006,21(7):680-686

在亚洲地区,不同流域的海岸带所接受的淡水、沉积物、营养物质和污染物质入海通量有着很大的差异。入海通量的特征受到流域人类活动的强烈影响,如水坝建设和化肥的大量施用。气候和海平面的变化也起了一定的作用。流域—海岸相互作用的特点是,入海物质通量的变化将导致流域、河口以及邻近水域的地貌、环境和生态系统的改变。在流域—海岸系统不断变化的情况下,为了改进流域—海岸系统开发的管理策略,应进行以下调查和研究工作：①在现场监测和观察的基础上,定量地描述上述变化;②了解引起上述变化的过程和机制;③发展预测未来变化的趋势和幅度的新方法、新技术;④将所获结果应用于流域—海岸系统的开发和管理实践。为了确定本研究领域今后10年的资助方向,APN (Asian Pacific Network for Global Change Research)召集了相关的学术研讨会。按照APN的部署,笔者负责完成了“流域—海岸相互作用”领域的研究课题建议,本文是这份文件的简要总结。  相似文献   

地幔橄榄岩捕掳体中尖晶石筛状边的成因     

胡森林  罗丹  陈立辉 《岩石学报》2017,33(1):69-80

山东的无棣大山和栖霞方山是两个以霞石岩为主的新生代火山,含有大量的地幔橄榄岩捕掳体,橄榄岩捕掳体中的尖晶石常见黑色反应边。在BSE图像上,这些反应边根据结构的不同又可以进一步分为两种:筛状边和均一边。有时两种反应边在同一颗尖晶石中共存并相互过渡。尖晶石捕掳晶和捕掳体中与寄主岩直接接触的尖晶石常发育均一边;发育筛状边的尖晶石则一般不直接与寄主岩接触,但位于捕掳体的边缘。尖晶石的筛状边呈多孔状,为富Cr尖晶石或铬铁矿。筛状边成分上与核部(Cr_2O_3=7.52%~36.75%,Cr#=7.80~44.20,Mg#=44.70~74.48)区别明显,具有高的Cr_2O_3含量(23.42%~65.96%)、Cr#值(78.97~92.49)以及低的Mg#值(17.22~43.02)。另外,筛状边相对其核部(TiO 2=0.00%~0.53%,MnO=0.04%~0.35%)还显示偏高的TiO 2(0.20%~3.60%)和MnO(0.29%~1.93%)。在筛状边附近存在富Al_2O_3(8.00%~17.57%)和MgO(17.89%~26.02%)的玻璃。尖晶石的均一边无孔洞但多发育裂理,成分上与核部突变,并以富TiO 2(20.90%~6.64%)和FeO T(70.79%~53.92%)为特征,最外部为钛磁铁矿。均一边具有明显的成分分带,表现为由内至外TiO 2、FeO T含量逐渐增高,Al_2O_3(0.04%~16.34%)、Cr_2O_3(0.77%~25.69%)和MgO(0.50%~7.16%)含量逐渐降低。尖晶石的两种反应边与寄主岩密切的空间关系说明其成因与寄主岩浆有关。虽然尖晶石筛状边的Cr#值(79.0~92.5)明显高于核部(7.8~44.2),但是其相对核部偏高的TiO 2和MnO含量,以及显著降低的Mg#值均与单纯的部分熔融趋势不吻合。根据尖晶石两种反应边的结构特征、成分特征和相互的空间关系,我们认为筛状边与均一边是岩浆与尖晶石反应不同阶段的产物。当橄榄岩捕掳体被岩浆捕获后,由于成分上的不均衡两者之间将发生溶解反应。反应过程中,尖晶石中不同元素向熔体迁移的速率区别明显,其中Cr是最难熔的元素也是迁移最慢的元素。在反应的初始阶段,由于易溶组份Al、Mg等元素随熔体迁出,尖晶石发育筛状边,并同时伴随Cr#值的显著升高和Mg#值的显著降低。此时,寄主岩浆中的Ti、Mn等元素也部分扩散进入筛状边中的残留尖晶石。如果熔体足够多,反应得以持续进行,筛状边中的Cr最终也将被熔体带走。在反应产生的混合熔体中金属氧化物最早达到饱和并结晶。随着反应的持续进行,结晶出的矿物将继续生长、变粗,并相互连接,直至孔洞消失形成均一边。同时伴随着矿物的不断结晶,溶解界面上的熔体成分也不断变化,从而使均一边具有明显的成分分带。在橄榄岩捕掳体内部,由于渗进捕掳体中的岩浆有限,渗透岩浆与尖晶石之间的反应多限于早期阶段,反应产物为筛状边。在捕掳体边缘,与寄主岩浆直接接触的尖晶石由于参与反应的岩浆量足够多,因此一般产生反应的终端产物———均一边。  相似文献