首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Increasing ocean temperature has become one of the major concerns in recent times with reports of various related ecological impacts becoming commonplace. One of the more notable is the increased frequency of mass coral bleaching worldwide. This study focuses on the Coral Triangle region and utilizes the National Oceanic and Atmospheric Administration-Coral Reef Watch (NOAA-CRW) satellite-derived sea surface temperature (SST) and Degree Heating Weeks (DHW) products to investigate changes in the thermal regime of the Coral Triangle waters between 1985 and 2006. Results show an upward trend in SST during this period with an average rate of 0.2°C/decade. However, warming within this region is not uniform, and the waters of the northern and eastern parts of the Coral Triangle are warming fastest. Areas in the eastern part have experienced more thermal stress events, and these stress events appear to be more likely during a La Niña.  相似文献   

2.
Changes in the abundance and distribution of individual species have been widely documented in Britain and other countries in recent decades, but little has been done to determine changes in community composition over broad geographic areas. Here, we studied species turnover in 51 butterfly assemblages in Britain since 1976, examining extinction and colonisation events together with variation in the abundances of the species. We showed that the species turnover that occurred over 20 years in Britain was associated with colonisation and extinction events and also with variability in the abundance of the species. These changes in community composition differed according to the habitat requirements of the species and their previous distributions, being more evident for habitat specialists and for southerly distributed species. Colonising species often became abundant components of the communities they joined, although this was more evident for generalist than for specialist species. The abundance of species following their arrival, increased with time since colonisation. Species turnover associated with southerly species expanding northwards is consistent with being a response to climate change. The results suggest that climate- and habitat-driven changes in the identity and abundance of species within communities are widespread, and probably ubiquitous. Similar changes are likely to be occurring in other groups of organisms that are similarly undertaking major range shifts associated with climate change.  相似文献   

3.
4.
Marine phytoplankton fuel the oceanic biotic chain, determine the carbon sequestration levels, and are crucial for the global carbon cycle and climate change. In the present study, we show a near-two-decadal (2002–2022) spatiotemporal distribution of global phytoplankton abundance, proxy as dominant phytoplankton taxonomic groups (PTGs), with a newly developed remote sensing model. Globally, six chief PTGs, namely chlorophytes (~26%), diatoms (~24%), haptophytes (~15%), cryptophytes (~10%), cyanobacteria (~8%), and dinoflagellates (~3%), explain most of the variation (~86%) in phytoplankton assemblages. Spatially, diatoms generally dominate high latitudes, marginal seas, and coastal upwelling zones, whereas chlorophytes and haptophytes control the open oceans. Satellite observations reveal a gentle multi-annual trend of the PTGs in the major oceans, indicative of roughly “unchanged” conditions on the total biomass or compositions of the phytoplankton community. Jointly, “changed” status applies to a short-term (seasonal) timescale: (1) Fluctuations of PTGs exhibit different amplitudes among different subregions, together with a general rule-more intense vibration in the Northern Hemisphere and polar oceans than other zones; (2) diatoms and haptophytes vary more dramatically than other PTGs in a global-scale scope. These findings provide a clear picture of the global phytoplankton community composition and can improve our understanding of their state and further analysis of marine biological processes.  相似文献   

5.
BackgroundCorpus uteri cancer has become the fourth most common female cancer in Europe. In Estonia, the prevalence of obesity is increasing, and corpus uteri cancer survival has been relatively low. The aim of the study was to evaluate incidence, mortality and survival trends of corpus uteri cancer in Estonia by age, stage and histological subtypes with an emphasis on surgical treatment.MethodsEstonian Cancer Registry data on incident cases of corpus uteri cancer were used to examine incidence trends (1995–2016) and calculate relative survival ratios (RSR) (1996–2016). Cases were classified by morphology and FIGO stage. Causes of Death Registry data were used to analyse corrected mortality (1995–2017).ResultsA total of 4281 cases were diagnosed in 1996–2016. A significant increase was seen in age-standardized incidence from 2009, while mortality remained stable throughout the study period. Significant increases were observed for type I cancers and age groups ≥65 years. Overall age-standardized 5-year RSR improved from 70% in 1996–2002 to 78% in 2010–2016. Survival increased for type I cancers, all age groups and all stages (significantly for stage IV). The proportion of surgically treated cases increased significantly from 85% to 89%, with the largest increases seen in older age groups and later stages.DiscussionThe rising corpus uteri cancer incidence in Estonia is driven by the type I cancer trend. Survival gain for later stages and older age groups likely reflected more frequent surgical treatment. To reduce mortality, further efforts are necessary to ensure appropriate care for all patients.  相似文献   

6.
What do animal signals mean? This is a central question in studies on animal communication. Research into the semantics of animal signals began in 1980, with evidence that alarm calls of a non-human primate designated predators as external referents. These studies have challenged the historical assumption that such referential signaling is a unique feature of human language and produced a paradigm shift in animal communication research. Over the past two decades, an increasing number of field studies have revealed similar complexity in anti-predator communication of birds. The acoustic structures of avian alarm calls show a high degree of variation in pitch, duration, shape, and repetition rate. In addition to such distinct and graded variations, several birds combine discrete types of notes or calls into higher complex sequences. These variations in alarm calls are typically associated with the predator’s attributes, such as predator type and distance, and receivers respond to them with appropriate anti-predator behaviors. Although alarm calls of several bird species, as well as those of monkeys, appear to denote predator attributes, almost nothing is known about the cognitive processes that underlie the production and perception of these signals. In this review, I explore the existing evidence for referential signaling in birds and highlight the importance of the cognitive approach to animal communication research. I hope this review will promote further investigations of alarm-calling behavior in birds and will help enhance our understanding of the ecology and evolution of semantic communication.  相似文献   

7.
The fish assemblage of the Mondego estuary was studied from June 2003 to May 2004. Five areas with different environmental conditions were sampled monthly, using a 2 m beam trawl (5 mm mesh size at the cod end). To complement information, sampling was also performed, seasonally, using a 7 m otter trawl with a 10 mm mesh size. Thirty-two species were identified. Dicentrarchus labrax, Pomatoschistus microps, Pomatoschistus minutus, Solea solea, Platichthys flesus and Diplodus vulgaris were the most abundant species. Marine juvenile migrants had the highest number of species, thirteen, followed by estuarine residents with eight species. Marine species that use the estuary as nursery grounds were the most abundant in terms of density and biomass. In spring and summer, juveniles occur in the upper, oligohaline areas, but afterwards, in autumn and winter, they tend to disperse to the middle and lower areas, with higher marine influence. Comparing the results obtained in this study with those reported in the early 1990’s, a marked decrease in species richness can be noticed, which is probably due to anthropogenic factors, namely an increase in depth of the main channel and intense euthrophication processes in the middle and upper areas.  相似文献   

8.
9.
泸沽湖是中国西南重要的水鸟越冬地和旅游风景区,开展泸沽湖越冬水鸟群落组成现状调查并进行历史变化分析,对指导泸沽湖水鸟及其栖息地保护和管理具有重要意义。2013年10月至2014年2月(12月除外),逐月对泸沽湖全湖及其西北方向的竹地海湿地(距离泸沽湖约500 m,面积约0.4 km2)越冬水鸟进行调查。泸沽湖共记录到水鸟27种,观察的最大个体总数约为22 600只,符合国际重要湿地标准。泸沽湖越冬水鸟群落的主要优势物种为骨顶鸡(Fulica atra),其最大观察数约为10 300只。竹地海湿地共记录到水鸟16种,观察到的最大个体总数约为3 600只,其中赤麻鸭(Tadorna ferruginea)约为2 700只;鉴于竹地海湿地亦为水鸟聚集的栖息地,建议将其划入泸沽湖自然保护区加以保护。对比1992年的调查数据,发现泸沽湖及其附近竹地海湿地越冬水鸟的物种丰富度(species richness)可能有所下降,由原来的33种下降到现在的30种,但个体总数量相对稳定。多种涉禽和喜浅水活动的钻水鸭类(dabbling ducks)消失,可能与湖岸区旅游活动的持续进行有关;泸沽湖曾经的主要优势物种赤嘴潜鸭(Netta rufina)种群数量大幅下降,暗示泸沽湖生态系统可能已发生变化。泸沽湖旅游业进一步发展的同时,保护好现存的浅水栖息地将是泸沽湖水鸟多样性不再继续下降的关键。  相似文献   

10.
11.
Habitat selection is a complex process, and animals may change their habitat selection over time. However, we have a poor understanding of temporal variation in habitat selection of endangered giant pandas (Ailuropoda melanoleuca), which has limited the development of conservation strategies for them. This study examined giant panda habitat selection in three stages of the past two decades (2001–2002, 2011–2012, and 2019–2020) in the Daxiangling Mountains, southwestern China. We applied the resource selection function to estimate the probability of species occurrence with five limiting habitat factors, i.e., elevation, slope, aspect, tree diameter at breast height, and bamboo cover. We found that giant pandas consistently selected for south- and west-facing slopes with mid-elevations and large trees in the three stages. However, there were shifts back-and-forth in the choice between higher and lower elevations and between higher and lower bamboo cover across the three stages. We suggest that the giant panda habitat selection had important consequences for gaining the high availability of palatable bamboo and good shelters. The back-and-forth shifts might be the result of changes in the type, spatial distribution, and intensity of human disturbance. Our study provides insights for improving our understanding and approaches for quantifying temporal variation in habitat selection in giant pandas and other species, suggesting that adaptive conservation and management in response to changing environments is needed.  相似文献   

12.
正The year of 2018 marks China's 40th anniversary of the reform and opening up. Coincidently, this year is also the 40th anniversary of Genetics Society of China (GSC), one of the largest academic organizations in China. In October of 1978, GSC was formally established in Nanjing, ushering a new era of genetics research in China, and its mission is to promote genetics research and education.Genetics focuses on the study of genes, genetic variations, and heredity in living organisms. It has permeated every field of  相似文献   

13.
Recent changes in climate have led to significant shifts in phenology, with many studies demonstrating advanced phenology in response to warming temperatures. The rate of temperature change is especially high in the Arctic, but this is also where we have relatively little data on phenological changes and the processes driving these changes. In order to understand how Arctic plant species are likely to respond to future changes in climate, we monitored flowering phenology in response to both experimental and ambient warming for four widespread species in two habitat types over 21 years. We additionally used long‐term environmental records to disentangle the effects of temperature increase and changes in snowmelt date on phenological patterns. While flowering occurred earlier in response to experimental warming, plants in unmanipulated plots showed no change or a delay in flowering over the 21‐year period, despite more than 1 °C of ambient warming during that time. This counterintuitive result was likely due to significantly delayed snowmelt over the study period (0.05–0.2 days/yr) due to increased winter snowfall. The timing of snowmelt was a strong driver of flowering phenology for all species – especially for early‐flowering species – while spring temperature was significantly related to flowering time only for later‐flowering species. Despite significantly delayed flowering phenology, the timing of seed maturation showed no significant change over time, suggesting that warmer temperatures may promote more rapid seed development. The results of this study highlight the importance of understanding the specific environmental cues that drive species’ phenological responses as well as the complex interactions between temperature and precipitation when forecasting phenology over the coming decades. As demonstrated here, the effects of altered snowmelt patterns can counter the effects of warmer temperatures, even to the point of generating phenological responses opposite to those predicted by warming alone.  相似文献   

14.
甘肃安西极旱荒漠国家级自然保护区目前已进行了三次综合科学考察(以下简称科考): 第一次1988-1989年、第二次2002-2003年、第三次2012-2013年。在三次科考20多年的时间跨度中, 脊椎动物各类群物种多样性发生了一定的变化: 鱼类增加了2种, 减少了3种土著种; 两栖爬行类种类一直保持稳定; 保护区三次科考记录的151种鸟类中, 有55.63%(84种)一直稳定分布。因气候变暖, 鸟类区系中东洋界比例增加, 有明显的分布区向西扩散的物种成分, 同时也有从新疆向东扩散的种类以及高原扩散来的成分。20年间分布减少的29种鸟类中, 主要为夏候鸟(41.37%)和旅鸟(48.28%), 这些鸟类的分布消失随机性很大。哺乳类的分布相对比较稳定, 第三次科考没有调查到的6种哺乳类应该是由于调查方法造成的。新增的小五趾跳鼠(Allactaga elater)是甘肃省啮齿类的一个新记录, 表明该物种分布区有向东南扩散的趋势。  相似文献   

15.
The dynamics of the infection of the European eel Anguilla anguilla L. by the Asian nematode Anguillicola crassus Kuwahara, Niimi and Itagaki, 1974 (i.e. anguillicolosis) was monitored over 2 decades in an oligohaline canal in southern France (Camargue, Mediterranean coast). Since the first mention of the parasite in this canal in 1985, which was also the first record in France, prevalence of pre-adult and adult forms has risen from 32 to 73%. However, during the last 7 yr (1997 to 2003), prevalence seems to have stabilized around values of 60 to 70% and parasite load, though inter-annual variation is substantial, shows no sign of increase (intensity for the last 5 yr: min. = 3.70, max. = 9.66, mean = 6.01). Our results thus confirm the dynamic pattern observed elsewhere in Europe, i.e. a rapid spread following the introduction of the parasite in a water system and then stabilization around ceiling levels. We review possible mechanisms that may explain such a leveling off in the infection spread. We particularly document the possibility that repetitive infections may render the infected organ, i.e. the swimbladder, unsuitable for further A. crassus establishment. In support of this hypothesis, we showed that the infection rate is lower among eels with severely damaged swimbladders.  相似文献   

16.
Over the past two decades, eco-engineering has been recognized as an important restoration approach to promote vegetation regrowth and greenness in a widespread rocky desertification land of southwest China. However, it remains unclear of recovery patterns and dominating drivers in different types of karst landforms. Here we use multi-satellite archives based on Google Earth Engine (GEE) to reveal the rapid greening process although encountered severe drought, especially in Karst Peak-Cluster Depression (+0.0035y−1) and Karst Trough Valley (+0.0035y−1) influenced by subtropical monsoon climate and afforestation endeavor, while degradation happened recently at non-karst areas of west highland in Karst Fault Basin (−0.0043y−1 since 2006) and Karst Plateau (−0.0039y−1 since 2014) influenced by decreasing rainfall. Afforestation project and sloping land conversion program is found to play crucial part in explaining a large part of the greening trend in Peak-Cluster Depression and Trough Valley but not in other landforms, suggesting that geomorphic heterogeneity should be further considered in restoration implementation and vegetation assessment, in conjunction with climate change and anthropogenic factors. Our study provides a helpful perspective for karst conservation priorities of various rocky desertification region ecosystems.  相似文献   

17.
18.
Limnology - In Lake Biwa, the largest lake in Japan, external pollutant loads have decreased since the 1980s, leading to improved water quality, such as reduction in biochemical oxygen demand (BOD)...  相似文献   

19.
20.
A chimeric protein called Wallerian degeneration slow (WldS) was first discovered in a spontaneous mutant strain of mice that exhibited delayed Wallerian degeneration. This provides a useful tool in elucidating the mechanisms of axon degeneration. Over-expression of WldS attenuates the axon degeneration that is associated with several neurodegenerative disease models, suggesting a new logic for developing a potential protective strategy. At molecular level, although WldS is a fusion protein, the nicotinamide mononucleotide adenylyl transferase 1 (Nmnat1) is required and sufficient for the protective effects of WldS, indicating a critical role of NAD biosynthesis and perhaps energy metabolism in axon degeneration. These findings challenge the proposed model in which axon degeneration is operated by an active programmed process and thus may have important implication in understanding the mechanisms of neurodegeneration. In this review, we will summarize these recent findings and discuss their relevance to the mechanisms of axon degeneration.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号