Spatial and temporal patterns of temperature,alkalinity, dissolved oxygen and conductivity in an oligo-mesotrophic,deep-storage reservoir in central Texas

Impoundment behavior was determined for alkalinity, temperature, dissolved oxygen, and conductivity from stations located along the length of a bottom-draining, oligo-mesotrophic, hardwater, deep-storage reservoir located in central Texas. The epilimnion deepened the length of the reservoir throughout the summer as a result of drawdown. Bicarbonate alkalinity and conductivity exhibited both longitudinal and vertical stratification. Alkalinity and conductivity in the epilimnion decreased from the riverine reach downreservoir to the dam. This longitudinal progression was attributed to inflow and photosynthetically induced epilimnetic decalcification.Hypolimnetic anoxic conditions first occurred in the sedimentation zone in the upreservoir and riverine reaches and then developed in a downreservoir pattern as summer progressed as a result of drawdown. Alkalinity and conductivity in the hypolimnion increased during anoxic conditions and consequently increased in a downreservoir progression.     

Disease hotspots or hot species? Infection dynamics in multi‐host metacommunities controlled by species identity,not source location

Pathogen persistence in host communities is influenced by processes operating at the individual host to landscape‐level scale, but isolating the relative contributions of these processes is challenging. We developed theory to partition the influence of host species, habitat patches and landscape connectivity on pathogen persistence within metacommunities of hosts and pathogens. We used this framework to quantify the contributions of host species composition and habitat patch identity on the persistence of an amphibian pathogen across the landscape. By sampling over 11 000 hosts of six amphibian species, we found that a single host species could maintain the pathogen in 91% of observed metacommunities. Moreover, this dominant maintenance species contributed, on average, twice as much to landscape‐level pathogen persistence compared to the most influential source patch in a metacommunity. Our analysis demonstrates substantial inequality in how species and patches contribute to pathogen persistence, with important implications for targeted disease management.     

三峡库区消落带4种适生植物根际与非根际土壤养分与酶活性特征研究

三峡库区消落带植被修复过程中,物种的更替对库区土壤的地球化学循环产生潜在影响。以三峡库区忠县石宝寨汝溪河消落带植被修复示范基地165-170 m海拔段人工种植狗牙根、牛鞭草、落羽杉以及立柳根际与非根际土为试验对象,探究其根际与非根际土壤的养分含量及酶活性差异,以阐明不同物种的生长适应性及其根际养分利用策略,比较不同物种对库区土壤的营养改良作用。结果表明：（1）三峡库区消落带4种适生植物根系活动导致根际与非根际土壤养分因子以及土壤酶活性产生差异,不同物种的栽植均在一定程度上使库区土壤营养条件得以改善;（2）碳、氮两种元素在4种适生植物根际土壤中发生不同程度的富集,但磷素与钾素在不同物种根际与非根际土壤之间的变化不一致;（3）蔗糖酶、脲酶以及酸性磷酸酶在4种适生植物根际土中均表现出一定程度的根际正效应（R/S>1）,且狗牙根对3种土壤酶的根际活化效果最为明显,其根际效应分别高达2.39、1.89和2.7;（4）在植物根系的调控下,根际土中有机质与氮素、磷素以及钾素的相关性更为显著,而非根际土壤中,仅钾素与有效氮、有效磷呈显著负相关,其余各土壤养分因子之间均无显著相关性;（5）与落羽杉和立柳两木本植物相比,狗牙根与牛鞭草两草本植物根际具有更为合理的养分调节模式,对库区土壤的改良效果更好。     

南水北调中线水源区丹江口市域景观格局变化及氮磷净化能力

丹江口库区是南水北调中线工程重要水源地,通过探究库区景观格局变化与氮磷净化能力,对未来景观规划和生态系统功能提升提供科学依据。在县域尺度上以丹江口市为研究区,运用景观格局指数和InVEST模型研究2003—2018年库区景观格局和氮磷净化能力,并利用Pearson相关分析和RDA分析法探讨二者之间的关系,分析引起氮磷净化能力变化的因素。结果表明:在斑块类型上,水域面积和林地面积不断增加,耕地和园地面积逐渐减少,建设用地面积整体上呈增长趋势;在景观水平上,景观形状指数不断减少,蔓延度指数和聚集度指数整体呈增长趋势,形状复杂程度降低,景观聚集程度提升,散布与并列指数增加了5.58,香农多样性指数变幅较小,各斑块类型趋于规则,呈均衡趋势分布。2003年、2008年、2013年和2018年氮磷净化能力呈持续增强趋势,其中TN输出总量分别为899.224、801.481、776.979、672.149 t, TP输出总量分别为77.308、69.921、68.163、60.802 t, 15年间TN、TP的净化能力分别增强了25.3%和21.4%;对氮磷净化能力重要性等级划分表明,极重要、高度重要区主要分布于库区、河流两岸和林地区域。利用Pearson相关分析和RDA分析法表明,在斑块类型上林地与氮磷的输出呈显著负相关,耕地、园地和建设用地与氮磷输出量呈正相关;在景观水平上氮磷输出量与景观形状指数呈显著正相关,和散布与并列指数表现出显著负相关,与蔓延度指数、聚集度指数呈负相关。因此,可在库区氮磷输出量较高的地区种植喜氮喜磷植物,通过调节景观格局结构,合理规划土地利用,增加林地面积,建设河岸植被缓冲带充分滞缓径流等一系列措施,充分保障库区水源水质安全。     

丹江口水库淅川库区大气氮湿沉降特征

大气氮沉降是除河流输入外水库水体重要的外源氮输入途径。以丹江口水库淅川库区为研究区,于2018年11月至2019年10月在库区周边设置了6个采样点,采集并分析了库区大气氮湿沉降样品,探讨氮湿沉降的时空分布特征以及对水库水体外源氮输入的贡献。研究结果表明,研究区大气氮湿沉降量为24.21 kg hm^-2 a^-1,其中氨氮占比（47.45％）为最大,有机氮占比（36.34％）次之,硝氮占比（16.21％）最小。硝氮湿沉降量在空间上表现出显著差异性。氨氮、有机氮湿沉降量的季节差异显著,氨氮是以夏季最高,秋季次之,冬季最低,而有机氮是以秋季最高,夏季次之,冬季最低。氨氮、硝氮、有机氮湿沉降量之间存在显著相关性,氨氮、有机氮湿沉降量与降水量之间存在显著相关性。总氮、氨氮湿沉降量分别为1321.98 t/a和627.34 t/a,分别占河流总氮、氨氮入库量的10.82％、34.85％。研究结果可为探索有针对性的库区水体氮污染控制途径提供重要理论基础。     

巴尔通体在滇西南蝙蝠中高度流行并具有丰富的遗传变异特征

蝙蝠是很多病原微生物的自然宿主, 全球多项研究表明蝙蝠是巴尔通体(Bartonella species)的主要宿主。为了解滇西南地区蝙蝠中巴尔通体的流行特征, 我们于2015-2017年间在云南省4个地区应用网捕法捕获蝙蝠3种305只。经种类鉴定后采集肝脾组织, 提取核酸, 通过TaqMan实时荧光定量PCR方法检测巴尔通体的tmRNA基因ssrA, 并进行测序鉴定和系统发育分析。结果发现172只蝙蝠检出该基因, 总感染率为56.4%; 其中临沧、西双版纳、保山和瑞丽4个采样点的蝙蝠感染率分别为50.0% (22/44)、61.7% (29/47)、62.1% (18/29)和55.7% (103/185)。中菊头蝠(Rhinolophus affinis)、小菊头蝠(R. blythi)和棕果蝠(Rousettus leschenaultii)的感染率分别为50.0% (22/44)、62.1% (18/29)和56.9% (132/232), 差异没有统计学意义(χ² = 1.135, P = 0.567), 表明巴尔通体在云南当地的蝙蝠种群中高度流行。定量PCR扩增产物2次扩增后测序获得37个巴尔通体ssrA序列, 属于10个系统发育分支, 其中1个为伊丽莎白巴尔通体(B. elizabethae)、特利波契巴尔通体(B. tribocorum)和克拉斯诺夫巴尔通体(B. krasnovii)的近缘种。其余序列与已知巴尔通体距离较远, 与亚洲、欧洲和美洲等其他地域来源于蝙蝠的巴尔通体近缘。遗传多样性分析显示, ssrA基因的核苷酸多样性指数(π)为0.11381 ± 0.00928, 基因型多样性指数(Hd)为0.985 ± 0.010, 形成29个基因型(单倍型), 说明云南蝙蝠巴尔通体具有丰富的遗传多样性。通过对本研究标本与全球相关序列的系统发育网络重建, 分析全球蝙蝠巴尔通体的地理和宿主分布特征, 可以看出巴尔通体与蝙蝠之间存在显著的宿主特异性关联。因此可初步确定蝙蝠-巴尔通体具有协同进化特征, 同时受到地理隔离的影响。     

Exploring human-animal host interactions and emergence of COVID-19: Evolutionary and ecological dynamics

The novel coronavirus disease (COVID-19) that emerged in December 2019 had caused substantial morbidity and mortality at the global level within few months. It affected economies, stopped travel, and isolated individuals and populations around the world. Wildlife, especially bats, serve as reservoirs of coronaviruses from which the variant Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) emerged that causes COVID-19. In this review, we describe the current knowledge on COVID-19 and the significance of wildlife hosts in its emergence. Mammalian and avian coronaviruses have diverse host ranges with distinct lineages of coronaviruses. Recombination and reassortments occur more frequently in mixed-animal markets where diverse viral genotypes intermingle. Human coronaviruses have evolved through gene gains and losses primarily in interfaces where wildlife and humans come in frequent contact. There is a gap in our understanding of bats as reservoirs of coronaviruses and there is a misconception that bats periodically transmit coronaviruses to humans. Future research should investigate bat viral diversity and loads at interfaces between humans and bats. Furthermore, there is an urgent need to evaluate viral strains circulating in mixed animal markets, where the coronaviruses circulated before becoming adapted to humans. We propose and discuss a management intervention plan for COVID-19 and raise questions on the suitability of current containment plans. We anticipate that more virulent coronaviruses could emerge unless proper measures are taken to limit interactions between diverse wildlife and humans in wild animal markets.     

La Stazione Bio-Fenologica al Cavallino (Venezia)

Abstract

From March 1988 to April 1989 a survey was carried out on the phytoplankton of Lake Bidighinzu, a hypertrophic reservoir in Northern Sardinia. The purpose of this work was to assess the general limnological conditions of the reservoir after a diversion of the urban and industrial wastes. The dynamics of chlorophyll a, and the structure and composition of the phytoplankton density and of its biomass in the study period were determined. Moreover the found trends for trasparency, temperature, conductivity, alkalinity, pH, dissolved oxygen, reactive and total phosphorus, nitrate, nitrite, ammonium nitrogen, and reactive silica are reported. The effect of water aeration on the dynamics of the other parameters is discussed.     

A comparison of bats and rodents as reservoirs of zoonotic viruses: are bats special?

Bats are the natural reservoirs of a number of high-impact viral zoonoses. We present a quantitative analysis to address the hypothesis that bats are unique in their propensity to host zoonotic viruses based on a comparison with rodents, another important host order. We found that bats indeed host more zoonotic viruses per species than rodents, and we identified life-history and ecological factors that promote zoonotic viral richness. More zoonotic viruses are hosted by species whose distributions overlap with a greater number of other species in the same taxonomic order (sympatry). Specifically in bats, there was evidence for increased zoonotic viral richness in species with smaller litters (one young), greater longevity and more litters per year. Furthermore, our results point to a new hypothesis to explain in part why bats host more zoonotic viruses per species: the stronger effect of sympatry in bats and more viruses shared between bat species suggests that interspecific transmission is more prevalent among bats than among rodents. Although bats host more zoonotic viruses per species, the total number of zoonotic viruses identified in bats (61) was lower than in rodents (68), a result of there being approximately twice the number of rodent species as bat species. Therefore, rodents should still be a serious concern as reservoirs of emerging viruses. These findings shed light on disease emergence and perpetuation mechanisms and may help lead to a predictive framework for identifying future emerging infectious virus reservoirs.