淮河流域板桥水库大型底栖动物群落结构及水质生物学评价

为了解板桥水库大型底栖动物群落结构动态特征并对其水质进行生物学评价,在该水库设置15个采样点,于2014年1—11月按季节进行调查.结果表明: 在板桥水库采集到大型底栖动物17种,隶属于3门4纲5科,其中摇蚊幼虫8种、寡毛类4种、软体动物5种.铜锈环棱螺、河蚬、苏氏尾鳃蚓、粗腹摇蚊和雕翅摇蚊为现阶段板桥水库的重要物种.大型底栖动物密度、生物量和多样性指数存在空间和时间差异性.ANOSIM分析显示,大型底栖动物群落结构在不同区域和季节间均存在显著差异,其主要贡献物种为雕翅摇蚊、粗腹摇蚊和苏氏尾鳃蚓.经丰度 生物量比较曲线(ABC曲线)分析,板桥水库大型底栖动物群落稳定,结合物种多样性指数、生物学污染指数(BPI)和Hilsenhoff生物指数(BI)评价结果,板桥水库的水质处于轻度污染水平.     

不同营养类型水库大型底栖动物的群落结构特征及其水质评价

2006～2007年对湖北省4座不同营养类型水库的大型底栖动物群落结构和多样性进行周年研究,并进行了水质评价.共采集到底栖动物39种,其中寡毛类14种、水生昆虫19种、软体动物6种.以金沙河的底栖动物种类最多,达24种,其次为徐家河19种,道观河和桃园河各10种.4座水库优势种类各异,金沙河为多毛管水蚓(Aulodrilus pluriseta)、隐摇蚊(Cryptochironomus sp.)、多足摇蚊(Polypedilum sp.);徐家河为瑞士水丝蚓(Limnodrilus helveticus)、前突摇蚊(Procladius sp.);桃园河为多毛管水蚓(Aulodrilus pluriseta)、长跗摇蚊(Tanytarsus sp.);水质污染比较严重的道观河水库优势种类为霍甫水丝蚓(Limnodrilus hoffmeisteri)、大红德永摇蚊(Tokunagayusurika akamusi).各库底栖动物年平均密度和生物量分别为:金沙河316 8ind · m-2,1294.3mg · m-2 ;道观河318.2ind · m-2,430.7mg · m-2 ;徐家河330.3ind · m-2,517.4mg · m-2;桃园河209ind · m-2,325 3mg · m-2 .TN、TP、COD平均含量变幅分别为0.392～1.018、0.011～0.042、3.505～9.166mg · L-1;采用理化分析、Goodnight-Whitley指数、Shannon-Wiener指数、Margalef指数、Simpson指数、Pielou均匀度指数对水库的水质进行了综合评价,结果表明:金沙河水库属中营养型;徐家河和桃园河属中-富营养型;道观河水库属富营养型.对水库主要的物理化学因子与寡毛类、水生昆虫、软体动物密度,以及各类底栖动物之间进行矩阵分析,发现水生昆虫与水深呈负相关关系,随着水深的增加,其密度和种类下降,水深超过10m,下降的幅度更明显;寡毛类有从属于TN和TP含量的趋势, TP变化对底栖动物的影响更大;寡毛类、水生昆虫、软体动物三者之间无相关性.     

南腊河底栖动物多样性与环境因子的关系

亚洲热带河流维系着高水平的生物多样性以及众多的特有物种。南腊河是澜沧江的一条重要支流,位于西双版纳州勐腊县境内,处于热带和亚热带交错区。为了了解南腊河大型底栖动物的群落特征、空间分布格局及关键驱动力,于2015年7月对其全流域进行了调查。共采集底栖动物96种,隶属于5门7纲50科,包含水生昆虫74种,软体动物8种,寡毛类9种,蛭类3种,涡虫、线虫各一种;全流域优势物种是霍甫水丝蚓(16.76%)、短脉纹石蛾(10.60%)、梯形多足摇蚊(10.27%)、河蚬(5.01%)、铜锈环棱螺(4.74%)和似宽基蜉(4.26%);从上游到下游,物种丰富度、密度、Margalef指数和Shannon指数均明显降低;群落组成则呈现蜉蝣目、毛翅目等类群逐渐减少,寡毛类、摇蚊幼虫、软体动物逐渐增加的趋势。典范对应分析(CCA)表明,南腊河大型底栖动物的分布主要受水深和底质类型等环境因子以及PCNM1-4、PCNM10和PCNM14等不同尺度空间因子的驱动。变差分解分析显示,空间因子对南腊河底栖动物群落结构的解释率高于环境因子。本研究可为亚洲热带河流底栖动物的分布特征及生物多样性的保护提供一定的参考。     

长荡湖大型底栖动物群落结构及水质生物学评价

2011年6月—2012年5月,对长荡湖大型底栖动物群落进行了逐月调查,并利用生物指数对水质进行生物学评价。结果表明:共采集到底栖动物28种,其中摇蚊科幼虫10种,水栖寡毛类7种,软体动物5种,其他类6种;铜锈环棱螺(Bellamya aeruginosa)、霍甫水丝蚓(Limnodrilus hoffmeisteri)、中国长足摇蚊(Tanypus chinensis)、多巴小摇蚊(Microchironomus tabarui)、苏氏尾鳃蚓(Branchiura sowerbyi)和半折摇蚊(Chironomus semireductus)是现阶段长荡湖底栖动物的优势种;长荡湖10个监测点底栖动物年均密度为769 ind·m-2,年均生物量为74.89 g·m-2,并呈现出明显的空间变化;生物量较密度空间差异更大,生物量高值主要出现在湖泊四周的监测点,而在湖心开阔水域较低;Wright指数、Goodnight-Whitley指数、BPI指数及Shannon指数表明长荡湖水体处于轻-中度污染状态。     

洱海流域湖泊大型底栖动物群落结构及空间分布

2009年5月对洱海及其流域内的海西海、茈碧湖和西湖3个小型湖泊进行底栖动物群落结构调查,以期阐明该流域湖泊底栖动物群落结构现状及其与水环境因子关系.结果表明:洱海底栖动物密度为1556ind·m-2,生物量8.9g·m-2.主要以摇蚊、霍甫水丝蚓和萝卜螺为密度优势种,相对丰度分别为43.5%、39.5%和8.6%;生物量优势种为刻纹蚬、萝卜螺和摇蚊.GIS插值显示,洱海北部密度最高,中部沿岸区生物量最高,南部密度和生物量均较低,Shannon多样性指数以湖岸区较高.其余3个湖泊以线虫、摇蚊科、颤蚓科和幽蚊科为主,其中以茈碧湖的密度和生物量最高(260.8ind·m-2和1.14g·M-2).CCA分析表明:洱海底栖动物主要受水体TP和Ca2+浓度的影响,贡献率分别为34%和27%;西湖与洱海群落组成最相似,主要由水体中较高的TN含量引起.对比历史数据可知,洱海寡毛类和摇蚊科比例继续增加,表明湖泊有机污染进一步加重.     

滆湖底栖动物群落的时空变化及水质生物学评价

2009年5月-2010年2月对滆湖底栖动物群落进行了调查,并根据底栖动物群落结构对水质进行了生物学评价。结果表明:采集到底栖动物共35种,隶属于3门25属;优势种类为中国长足摇蚊(Tanypus chinensis)、霍甫水丝蚓(Limnodrilus hoffmeisteri)、苏氏尾鳃蚓(Branchiura sowerbyi)、克拉泊水丝蚓(L.claparedeianus)、中华河蚓(Rhyacodrilussinicus);滆湖底栖动物的年均密度为374.1ind·m-2,寡毛类对密度的贡献最大,占年均密度的77.4%,最大密度出现在夏季,春季最低,St14年均密度高于其他站点;滆湖底栖动物的年均生物量为17.78g·m-2,软体动物对生物量的贡献最大,占年均生物量的97.4%,夏季生物量最大,冬季最低,St14年均生物量明显高于其他各个站点;底栖动物的密度和生物量随季节变化明显,密度的季节变化表现为夏季>秋季>春季>冬季,生物量变化表现为夏季>春季>秋季>冬季;Shannon-Wiener多样性指数值(H’)、Margalef多样性指数值(D)、Pielou均匀度指数值(J)和BI指数值表明滆湖水体处于中度到重度污染状态。     

新疆额尔齐斯河大型底栖动物的群落结构及水质生物学评价

新疆额尔齐斯河是中国唯一流入北冰洋的河流,整个流域有着极为丰富的底栖动物资源。2012年7月、8月、10月与2013年5月分别对额尔齐斯河干流、5条主要支流以及附属水库的大型底栖动物群落结构特征进行了调查。结果表明:共采集大型底栖动物117种,其中水生昆虫106种(90.6%),软体动物6种(5.1%),寡毛类3种(2.6%),其他大型底栖动物2种(1.7%);优势种主要为似动蜉(Cinygmula sp.)、四节蜉(Baetis sp.)、直突摇蚊(Orthocladius sp.)、蜉蝣科(Ephemeridae sp.)、多足摇蚊(Polypedilum sp.)、摇蚊(Apedilum sp.)、霍甫水丝蚓(Limnodrilus hoffmeisteri)、短脉纹石娥(Cheumatopsyche sp.)、小蜉(Ephemerella sp.)、寡角摇蚊(Diamesa sp.);大型底栖动物的密度(P=0.558)与生物量(P=0.464)季节性差异不显著,年平均密度与生物量分别为519.05 ind·m-2、3.30g·m-2,大型底栖动物密度存在明显的空间差异,整体上上游(604.53 ind·m-2)高于下游(447.82 ind·m-2);大型底栖动物年平均Margalef指数、Shannon指数、Simpson指数、Pielou指数分别为1.12、0.53、0.65、0.52;聚类分析显示,多样性指数较低的185团北湾、布尔津河口、盐池、小635采样点聚为一类,其余各点聚为一类;利用科级生物指数(FBI)、Beck指数、Chandler生物记分制(CS)以及BMWP指数评价额尔齐斯河各段水质,整体上水质属轻度污染;Spearman相关性分析显示,水生昆虫的分布与水体透明度呈显著正相关,而寡毛类的分布与盐度、电导率和矿化度呈显著正相关,与电阻呈显著负相关,软体动物的分布与环境因子的关系不显著。     

高原深水湖泊抚仙湖大型底栖动物群落结构及多样性

云南抚仙湖是我国典型的高原深水湖泊,20世纪80年代以来,随着人类活动的加剧,其水体营养水平不断提高,生态系统发生了显著变化。为揭示该湖底栖动物的群落特征及其对生态系统变化的响应,2005年正7月对大型底栖动物群落进行了调查。在抚仙湖18个断面110个样点中共采集大型底栖动物19属27种,大型底栖动物出现率为97.3％,平均密度为855ind．／m^2,平均生物量为58．01g／m^2。在密度组成上软体动物（50．3％）〉摇蚊幼虫（32-3％）〉寡毛类（17．4％）,优势种为花纹前突摇蚊（Procladius choreus）、长角涵螺（Alocinma tongicornis）和方形环棱螺（Bellamya quadrata）,三者共占总密度的51．4％。寡毛类和摇蚊幼虫全湖性分布,而软体动物主要分布在沿岸区,各类群优势种均呈聚集分布。底栖动物在沿岸区生物量显著大于湖心区（P〈0．01）,但两者之间密度差异不显著（P〉0．05）;南区和北区之间的密度（P〉0．05）和生物量（P〉0．05）差异均不显著。相关分析表明,表层沉积物总有机碳、底层水体溶解氧是影响底栖动物密度分布的关键理化因子,而底层水体溶解氧是影响底栖动物生物量分布的关键理化因子。抚仙湖大型底栖动物群落的Pielou均匀度指数、Margalef丰富度指数、Simpson优势度指数、Shannon-Wiener多样性指数及改进的Shannon-Wiener多样性指数分别为0．74、2．88、0．87、2．40和20．84。沿岸区底栖动物多样性明显高于湖心区,主要是由于沿岸区分布有各种沉水植物,提高了底栖动物生境的异质性。与1980年调查结果相比,抚仙湖底栖动物多样性呈上升趋势,这与水体营养水平不断提高,沉水植物分布面积扩大有关。     

徐州城市河流和湖泊的大型底栖动物群落结构及影响因子分析

对徐州市京杭运河市区段和市区湖泊云龙湖进行了大型底栖动物群落结构及影响因子的比较研究。结果显示:城市河流和湖泊生态系统中, 大型底栖动物种类较少、群落结构相对简单, 其中城市河流大型底栖动物的组成主要为水栖寡毛类和软体动物, 城市湖泊大型底栖动物主要组成为水栖寡毛类和摇蚊幼虫。除Margalef 物种丰富度指数外, 河流与湖泊的其他群落指数相差不大。聚类分析将两类生态系统中的大型底栖动物群落明显分为两组。CCA 结果显示云龙湖大型底栖动物群落的主要影响因子是pH 和溶解氧, 京杭运河徐州市区段大型底栖动物群落的主要影响因子是总磷和化学需氧量。     

浙江分水江水库大型底栖动物群落结构及水质评价

2008年11月-2009年10月,在浙江桐庐分水江水库设置7个站点对大型底栖动物进行逐月调查.结果表明:调查共采集到37种底栖动物,主要由寡毛纲和摇蚊科物种组成.春、夏、秋季优势种均为霍甫水丝蚓,冬季优势种为羽摇蚊.直接收集者在物种数量、密度和生物量上均占绝对优势.群落年均密度和年均生物量分别为(488.0±48.8) ind·m-2和(1.86±0.49) g·m-2.底栖动物密度在站点间无明显差异但存在显著的季节变化,呈现春季＞夏季＞冬季＞秋季的趋势,生物量在站点、季节间均无显著差异.水温和水深是影响底栖动物时空分布的主要因子.Shannon多样性指数和Goodnight-Whitley指数不适合用于该水库的水质评价,其他指数综合显示分水江水库属于轻度污染.     

浙江渔山列岛岩礁潮间带大型底栖动物次级生产力

为揭示渔山列岛潮间带大型底栖动物现状,2009年3月至2010年1月在渔山列岛潮间带布设5条断面进行了4个季节的调查取样.利用Brey的经验公式计算了调查海区大型底栖动物栖息密度、生物量、次级生产力和P/B值.结果表明:该潮间带大型底栖动物平均栖息密度为1419.5ind.m-2,以去灰干质量(AFDM)计,平均生物量为565.53g.m-2,平均次级生产力为285.58g.m-2.a-1,P/B值为0.51.潮间带次级生产力受大型软体动物和甲壳类影响明显,5个关键生物种(条纹隔贻贝、偏顶蛤、覆瓦小蛇螺、日本笠藤壶和鳞笠藤壶)对次级生产力的贡献为84.0%.研究海域P/B值低于其他海域,说明该海域大型底栖动物世代更替速度较慢,群落结构较稳定.     

广东省6座水库及其入库河流底栖动物调查与综合评价

2010年8月对广东省6座水库及其入库河流的大型底栖无脊椎动物群落进行采样调查,并分别利用Goodnight-Whitley指数和BPI指数对水库及入库河流的水质进行评估。结果表明,水库共检出底栖动物13种,优势种为霍甫水丝蚓(Limnodrilus hoffmeisteri)、苏氏尾鳃蚓(Branchiura sowerbyi)和八斑多足摇蚊(Polypedilum masudai),种类丰富度变动范围为2～5种,平均密度为277ind/m²,变动范围160～480ind/m²。入库河流的种类丰富度和密度均高于水库,共检出底栖动物28种,优势种为苏氏尾鳃蚓、霍甫水丝蚓、花翅前突摇蚊(Procladius choreus)和河蚬(Corbicula fluminea),种类丰富度变动范围为2～7种,底栖动物平均密度为382ind/m²,变动范围192～816ind/m²。水质评价结果表明,6座水库的水质状况总体良好,但入库河流均受到不同程度的污染,污染较为严重的黄岗河和黄羌河,其水库汤溪水库和公平水库也产生了污染。     

Ungulate damage to safflower in Utah

In Utah, farmers are concerned that ungulates are damaging safflower (Carthamus tinctorius) fields. We examined elk (Cervus elaphus) and mule deer (Odocoileus hemionus) damage to safflower production in San Juan County, Utah during 2009 and 2010. We collected data on damaged safflower plants within 28 fields, totaling 1,581 ha (13 fields totaling 963 ha during 2009; 15 fields totaling 618 ha during 2010). We compared 3 methods to assess yield losses: ungulate-proof exclosures, adjacent plant compensation method, and counting the number of damaged plants in 50-m transects (safflower count method). Exclosures were of limited use because they could not be erected until farmers stopped cultivating their fields. Hence, this method did not account for ungulate damage to young plants. The adjacent plant compensation method assessed yields within 1 m of a randomly selected damaged plant to account for any compensatory growth of neighboring plants, but this method proved inaccurate because ungulate herbivory was concentrated so that a browsed plant was often surrounded by other browsed plants so no compensatory growth by surrounding plants occurred. The most accurate method was the safflower count method, which determined the number of damaged plants within a field and then multiplied this number by the decrease in yield from an average damaged plant. We used this method to examine 981,000 plants for damage. Deer and elk damaged or killed 7.2% of safflower plants during 2009 and 1.4% of plants during 2010. Overall yield reduction was 2.9% during 2009 and 0.6% in 2010. The value of safflower loss within all surveyed fields in 2009 was $9,023 for a loss of $9.42/ha. The loss of value within surveyed fields in 2010 was $2,330, or $3.77/ha. The best model for predicting ungulate damage during 2009 included distance to a canyon and the percent of a field bordered by a fallow field, whereas the best model for 2010 included distance to a canyon and the percent of a field bordered by a wheat field. We surveyed safflower farmers during the spring of 2010 to compare perceived losses in their fields during 2009 to those measured that same year. Farmers believed that damage by deer and elk reduced their yields by 20% with most damage caused by elk ( = 12% by elk, 7% by deer, 1% by other wildlife). On average, perceptions of damage were 5.2 times greater than the actual levels we measured during 2009. This was not surprising because farmers usually surveyed their field from the field's edge where ungulate damage was concentrated. © 2012 The Wildlife Society.     

Abundance of Diadema antillarum (Echinodermata: Echinoidea) in the coasts of Venezuela

Diadema antillarum is a shallow-water sea-urchin from the tropical Atlantic whose populations almost disappeared in 1983-84 because of widespread mortalities which reached 87-100 %. In Venezuela, urchin population densities before the mortality event were comparable to those of other Caribbean regions; however, later abundancies remain unknown. The objectives of this study were to evaluate the recent densities of certain D. antillarum populations along the Venezuelan coasts and compare the densities at the Parque Nacional Mochima before and after the mortality. At each location urchin densities were determined by means of transects using 1 m2-quadrats as sampling units. The highest mean densities were observed at the sites on the central coast: Ensenada de Oricao, 0.28 ind/m2 (2002) and 1.05 ind/m2 (2003), and Chichiriviche de la Costa, 0.84 ind/m2 (2002) and 0.74 ind/m2 (2003). In Mochima, the mean density before the mortality for D. antillarum oscillated between 0.28 and 4 ind/m2, after the mortality event the mean density varied between 0.15 ind/m2 (2000) and 0.47 ind/m2 (2000). The populations of D. antillarum studied at Parque Nacional Morrocoy and Refugio de Fauna Silvestre Cuare showed highest densities at Playuela (0.43 ind/m2) and Cayo Sur (0.95 ind/m2) respectively, whereas other sites showed densities below 0.1 ind/m2. The density registered at Playuela in 2003 is lower than that reported before the mortality event (0.58-3.64 ind/m2). The density for Parque Nacional Archipiélago de Los Roques, specifically for the Arrecife de Herradura remained constant between 2002 and 2003 with values between 0.22-0.23 ind/m2 respectively. To conclude, the sea urchin abundancies observed at most of the Venezuelan coastal sites that we studied were higher than those reported for other areas of the northern Caribbean, even though the values have not yet returned to those preceding the 1984 mass-mortality event, due to the slow recovery of the populations.     

Population ecology of Acacia tortilis in the semi-arid region of the Sudan

Abstract. The population ecology of Acacia tortilis, one of the important woody species in the arid and semi-arid regions of northern Africa, was studied in the Sudan: Ten sample plots were established and all individuals in the plots were mapped and their basal diameter, stem height, crown height and cover measured annually for three years. Individuals were grouped into different height-classes, ‘life-forms’: trees >1.65 m, shrubs > 0.65 m and < 1.65 m, saplings < 0.65 m and seedlings (saplings less than one year old). The population density was 510 ind./ ha in 1985, 432 ind. / ha in 1986 and 218 ind. / ha in 1987. The life-form distribution of the population showed clear differences between plots and years. Mortality in Acacia tortilis, expressed as loss in individuals per year, amounted to 167 ind. / ha / yr. Drought and lethal cutting were found to be the main mortality factors. The population declined by 15.3 % from 1985 to 1986 and by 49.5 % from 1986 to 1987. Natality (recruitment), expressed as number of newly established saplings, was 13 ind. / ha / yr. Recruitment is apparently discontinuous and bound to years with a relatively high precipitation.     

Asteroidea, Echinoidea y Holothuroidea in shallow bottoms of Bahía de Loreto, Baja California Sur, Mexico

To evaluate echinoderm distribution, abundance and density a double 50 m transect, with a side observation range of 2.5 m was used at each of 11 stations (bimonthly samplings, Aug. 1997-Febr. 1998). In Bahía de Loreto the Phylum Echinodermata consists of 26 taxa. The greatest mean abundance by transect and mean densities in order of importance for Echinoidea were: Echinometra vanbrunti (94.1 +/- 52.9 ind, 0.25 ind/m2), Centrostephanus coronatus (38.15 +/- 9.15 ind, 0.06 ind/m2), Tripneustes depressus (28.68 +/- 6.86 ind, 0.039 ind/m2), Eucidaris thouarsii (10.66 +/- 3.37 ind, 0.025 ind/m2) and Diadema mexicanum (11.75 +/- 4.92 ind, 0.023 ind/m2); for Asteroidea were: Phataria unifascialis, Mithrodia bradleyi and Acanthaster planci. Asteroidea was the dominant class with 12 species, followed by Echinoidea with ten and Holothuroidea was represented by four species.     

Arthropod community associated with the canopy of Attalea phalerata Mart. (Arecaceae) during the flood period of the Pantanal of Poconé, Mato Grosso, Brazil

Six trees of the palm species Attalea phalerata Mart. were sampled during high water (aquatic phase) of the Pantanal of Mato Grosso (February 2001), by canopy fogging. The composition, structure, and biomass of the arthropod community associated with their canopies were analysed, as well as the influence the flood pulse renders on it. Each tree was fogged once, followed by three consecutive collections. A total of 63,657 arthropods (643.0 +/-; 259.87 ind./m(2)) were collected, representing 25 orders in the classes Insecta, Arachnida, Diplopoda and Crustacea. The dominant groups were Acari (40.0%; 257.2 +/- 116.50 ind./m(2)), Coleoptera (12.0%; 77.5 +/- 64.93 ind./m(2)), Psocoptera (9.2%; 59.0 +/- 38.00 ind./m(2)), Diptera (8.4%; 54.1 +/- 18.72 ind./m(2)), Collembola (8.3%; 53.4 +/- 26.24 ind./m(2)) and Hymenoptera (7.9%; 50.6 +/- 21.40 ind./m(2)), the latter mostly represented by Formicidae (49.2%). Arthropod biomass amounted to 8.86 g dry weight and 0.18 mg/m(2). Coleoptera, Blattodea, Orthoptera, Araneae and Hymenoptera were the most representative taxa. The hydrological regime (flood pulse), as well as seasonality, appear to strongly affect the composition and structure of this canopy community.     

珠江口大型底栖动物的群落结构及影响因子研究

2008年8月至2009年5月, 调查了珠江口水域大型底栖动物季节分布以及与环境的关系, 结果表明:共鉴定出大型底栖动物34种, 多毛类和软体动物是该水域大型底栖动物的主要类群;大型底栖动物的密度和生物量以春季最高, 分别为759ind/m2和5.03g/m2,秋季则最低,分别为274ind/m2和2.34/g/m2.食底泥者是珠江口大型底栖动物最主要的功能摄食类群。研究区大型底栖动物的物种多样性指数(H′)、物种均匀度指数(J′)和物种丰富度指数(D)差异均不显著。典型对应分析表明:夏季锌、铜、铅、磷酸盐和透明度等5个因子与珠江口大型底栖动物群落相关性显著;秋季为铵氮;冬季和春季则分别为透明度和温度。       

Comparison of gastropod mollusc (Apogastropoda: Hydrobiidae) habitats in two crater lakes in Nicaragua

The aquatic gastropod mollusc, Pyrgophorus coronatus, may perform an important role in the transmission of an emergent ocular pathology among fishes in Lake Apoyo, Nicaragua. This disease emerged after an introduction of tilapia (Oreochromis niloticus) and the subsequent loss of Chara sp. beds in the lake. We compared the mollusc population densities in three habitats (sandy/muddy substrates, rocks, and Chara vegetation) at varying depths (1.5, 10, 20, and 30 m) in two volcanic crater lakes in Nicaragua: Lake Apoyo and Lake Xiloa. where lower numbers of affected fishes were found and tilapia has not been introduced. Duplicate samples at 1.5 m depth were taken in each habitat monthly for a year, and triplicate samples for bathymetric analysis of snail populations were performed during August, 2005. Samples of fixed surface area were filtered in a 0.4 cm size screen and live snails were counted from each sample. The preferred snail habitat in both lakes, Chara beds, was vastly reduced in Lake Apoyo via consumption by introduced Nile tilapia (Oreochromis niloticus). Structureless sandy substrates (mean +/- standard error 3.1+/-1.3 ind/m2) had lower population densities than other habitats in Lake Xiloa (rocks 590.9+/-185.3 ind/m2; vegetation 3 686.5+/-698.2 ind/m2; ANOVA 1, p<0.01 in both cases) but this difference was attenuated in Lake Apoyo (sand 384.4+/-111.1 ind/m2; rocks 1 480.4+/-384.8 ind/m2: 0.0 1相似文献   

The effect of season and light intensity on the core interthreshold zone

The hypothesis tested in the present study is a seasonal difference in the core interthreshold zone (CIZ), as we suggested in an earlier study that individual awareness of heat may change the CIZ due to thermoregulatory behavior. A series of human experiments were carried out in a climatic chamber in January and August of 2009 and January of 2010. The air temperature in the chamber was controlled at 20-24°C. Subjects wore a water-perfused suit that was perfused with 25°C water at a rate of 600 cc/min. They exercised on an ergometer at 50% of their maximum work rate for 10-15 min until their sweating rate increased and then remained seated without exercise until oxygen uptake increased. Subjects' rectal temperature and skin temperatures at four sites were monitored by thermistors. The sweating rate was measured at the forehead with a sweat rate monitor (SKD 4000, Skinos Co.). Oxygen uptake was monitored with a gas analyzer (Respiromonitor RM-300i, Minato Med. Science Co.). In the 2009 winter experiment, 5 male subjects were exposed to lighting of 36 cd/m(2)/1,050 lx, and in the 2009 summer and 2010 winter experiments, 10 male subjects were exposed to lighting of 18 cd/m2/510 lx. The results showed that the CIZ of 0.69±0.29°C (n=22, data from 2005-2007 experiments) at 36 cd/m(2) and that of 0.37±0.17°C (n=10) at 18 cd/m(2) in summer were greater than the CIZ of 0.37±0.13°C (n=5) at 36 cd/m(2) and that of 0.18±0.17°C (n=10) at 18 cd/m(2) in winter, and thus demonstrated a seasonal difference in the CIZ as well as an effect of lighting conditions on the CIZ.