937 resultados para Anuran assemblages
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The evolutionary relationships of species of Danio and the monophyly and phylogenetic placement of the genus within the family Cyprinidae and subfamily Rasborinae provide fundamentally important phyloinformatics necessary for direct evaluations of an array of pertinent questions in modern comparative biology. Although the genus Danio is not one of the most diverse within the family, Danio rerio is one of the most important model species in biology. Many investigations have used this species or presumed close relatives to address specific questions that have lasting impact on the hypothesis and theory of development in vertebrates. Largely lacking from this approach has been a holistic picture of the exact phylogenetic or evolutionary relationships of this species and its close relatives. One thing that has been learned over the previous century is that many organismal attributes (e.g., developmental pathways, ecologies, behaviors, speciation) are historically constrained and their origins and functions are best explained via a phylogenetic approach. Herein, we provide a molecular evaluation of the phylogenetic placement of the model species Danio rerio within the genus Danio and among hypothesized closely related species and genera. Our analysis is derived from data using two nuclear genes (RAG1, rhodopsin) and five mitochondrial genes (ND4, ND4L, ND5, COI, cyt b) evaluated using parsimony, maximum likelihood, and Bayesian analyses. The family Cyprinidae is resolved as monophyletic but the subfamily Rasborinae (priority over Danioinae) is an unnatural assemblage. Danio is identified as a monophyletic group sister to a clade inclusive of the genera Chela, Microrasbora, Devario, and Inlecypris, not Devario nor Esomus as hypothesized in previous studies. Danio rerio is sister to D. kyathit among the species of Danio evaluated in this analysis. Microrasbora and Rasbora are non-monophyletic assemblages; however, Boraras is monophyletic.
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Benthic diatom communities were sampled monthly from May 2004 to May 2005 at four different sites in the littoral zone of Lake Donghu, a shallow eutrophic lake of China. The seasonal patterns of the total abundance, which were lowest in summer and highest in spring, were found at all sites. Total densities of diatom assemblages were significantly higher at hyper-eutrophic sites than at moderately eutrophic sites. Melosira varians was the most abundant species and dominant contributor to total abundance at all sites during spring, autumn and winter, whereas Achnanthes exigua dominated benthic diatom assemblages at the site with the highest nutrient concentrations during the summer. Achnanthes lanceolata var. dubia, Gomphonema parvulum, Navicula similis, Navicula verecunda and Nitzschia amphibia were generally observed at all sites throughout the year and were dominant at higher-nutrient sites. The abundance of ambient nutrients was probably responsible for the spatial variation in biomass, composition and diversity of benthic diatom assemblages, and lake water temperature was the major factor that controlled seasonal distribution.
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The benthic community structure in Baoan Lake was examined in relation to lake water physicochemical characteristics and biological parameters. Seventy macroinvertebrate taxa were identified, and mollusks constituted the dominant group and accounted for more than 80% of the total abundance. Assemblages were composed mainly of scrapers (81.5%) and collector-gatherers (roughly 10%). Three plant variables (richness, total cover, and total biomass) were strongly correlated with the faunal gradient (p<0.05). Other predicator variables were Cl-, SiO2, and chemical oxygen demand. Because of the importance of macrophytes in structuring benthic assemblage in this lentic system, the spatial heterogeneity of macrophytes also influenced the pattern of macroinvertebrates. Seven lake regions were uniquely characterized according to primary macrophyte composition and biomass. There were significant differences for macroinvertebrate taxa richness, abundance, and biodiversity among the seven macrophyte regions.
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Surveys of macroinvertebrates were carried out in the Xiangxi River system during July of 2001. Among the 121 taxa collected, Ephemeroptera, Trichoptera, and Diptera dominated (41.7, 26.0, and 24.5% of the total relative abundance, respectively). Two-way indictor species analysis and detrended correspondence analysis divided the 49 sites into four groups based on species composition and relative abundance. Canonical correspondence analysis indicated that elevation, SiO2, pH, conductivity, hardness, and NO2-N were significant environmental factors affecting the distribution of macroinvertebrates.
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Phytoplankton assemblages in the subtrophical oligotrophic Lake Fuxian, the second deepest lake in China, were investigated monthly from September 2002 to August 2003. A total of 113 species belonging to seven phyla were identified, among them, a filamentous green alga, Mougeotia sp., dominated almost throughout the study period and comprised most of the total phytoplankton biomass. Mougeotia sp. has made a substantial development during the past decades: it was absent in 1957, only occasionally present in 1983, increased substantially in 1993, and became predominant in 2002-2003. It is likely that natural invasion of the Taihu Lake noodlefish (Neosalanx taihuensis) has led to a change of dominant herbivorous zooplankton from small to large calanoid, which has increased grazing pressure on small edible algae, and thus has indirectly favored the development of the inedible filamentous Mougeotia sp.
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Ecological survey of macrozoobenthos assemblages was carried out at 32 sites in the East Dongting Nature Reserve, located in the northern region of the East Dongting Lake in the middle basin of the Yangtze River, China. All total 51 taxa including 18 oligochaetes, 15 mollusks, 14 insects and four other animals were recorded. Mollusks composed the dominant group and accounted for more than 70% of the total abundance. Assemblages were composed mainly of scrapers (66.7%) and collector-gatherers (nearly 20%), and to a lesser extent collector-filterers (roughly 12%), predators (ca. 7%), and shredders (ca. 6%). Two-way indicator species analysis, detrended correspondence, and canonical correspondence analysis (CCA) were employed to identify the relationships between macrozoobenthos assemblages and environmental variables. Thirty-two sites were separated into four site groups based on composition and relative abundance of benthic macroinvertebrates. CCA detected that water depth, pH, conductivity, SiO2, total nitrogen, total phosphorus, alkalinity, hardness, and Ca2+, were significant environmental factors influencing the pattern of macozoobenthos. In this minimal subset, water depth, pH, alkalinity and hardness were the most influential variables.
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从空间、时间、食物3个方面研究了若尔盖湿地3种两栖类的种间竞争,运用生态位理论探讨了3种两栖类利用环境资源的能力以及它们之间的共存模式,研究了3种两栖类年周期食性,并考察了畜牧业对3种两栖类食性及食物竞争格局的影响;此外,还通过实验室研究对2种两栖类幼体的种间竞争策略进行了考察。主要结果如下: 1、两栖类的空间资源利用状况:在3种两栖类成体生态位宽度的比较中,岷山蟾蜍(Bufo minshanicus)成体在牧场性质(0.41)、牛粪数量(0.42)、植被盖度(0.20)、地表温度(0.50)、地表湿度(0.51) 5个维度上的生态位宽度最窄;而倭蛙(Nanorana pleskei)成体在牛粪数量(0.81)、植被高度(0.63)、植被盖度(0.47)、小水体距离(0.68) 4个维度上的生态位宽度最宽。在3种两栖类亚成体生态位宽度的比较中,岷山蟾蜍亚成体在牧场性质(0.66)、牛粪数量(0.58)、植被高度(0.64)、小水体距离(0.51)、地表湿度(0.79) 5个维度的上生态位宽度最宽;倭蛙亚成体在牧场性质(0.39)、牛粪数量(0.30)、地表温度(0.18)、地表湿度(0.33) 4个维度上的生态位宽度最窄。高原林蛙(Rana kukunoris)在地表温度(成体:0.62;亚成体:0.56)、地表湿度(成体:0.84;亚成体:0.60)两个维度上具有较大的生态位宽度值,而在小水体距离维度上(成体:0.27;亚成体:0.14)的生态位宽度值则很小。比较3种无尾两栖类在不同生长阶段(成体、亚成体)的生态位宽度,发现高原林蛙和倭蛙的亚成体对栖息环境的要求更高。3种两栖类空间资源利用的相似程度很高,高原林蛙与倭蛙之间的生态重叠度(0.87)较之它与岷山蟾蜍(0.81)的生态位重叠度更大。 2、两栖类的日活动节律:高原林蛙成体、亚成体、岷山蟾蜍亚成体活动的最低气温为0℃、2℃、8℃;岷山蟾蜍和高原林蛙亚成体出现的数量与气温成极显著的正相关(r=0.797, p<0.001;r=0.794, p<0.001),高原林蛙成体出现的数量与气温有一定相关性(r=0.456, p<0.05);晴天时两栖类的活动性明显高于阴天(p<0.001);多云转晴天气,高原林蛙和岷山蟾蜍亚成体出现两次日活动高峰,分别为中午12:30左右和下午15:30~16:30之间;多云天气,高原林蛙和岷山蟾蜍亚成体出现两次日活动高峰,分别为9:30~10:30之间和15:30~16:30之间。 3、两栖类的食物资源利用状况:春、秋两季,高原林蛙最主要的食物是蜉金龟科(Aphodiidae)昆虫,相对重要性指数(IRI)最高(春季:35.28%,秋季:28.57%),其次为昆虫的幼虫,以及双翅目的毛蚊科(Bibionidae)、蝇科(Muscidae)、丽蝇科(Calliphoridae)昆虫,秋季,蝗虫是高原林蛙食物组成中的重要部分;岷山蟾蜍最主要的食物是蚂蚁(IRI,春季:85.54%,秋季:49.70%),其次为蜉金龟科、象甲科(Curculionidae)、步甲科(Carabidae)、粪金龟科(Geotrupidae) 等鞘翅目昆虫;倭蛙春季的最主要食物也是蜉金龟科昆虫(IRI,春季:13.41%),其次为蚂蚁、毛蚊科昆虫、昆虫的幼虫以及狼蛛科(Lycosidae)。3种两栖类中,倭蛙的食性生态位宽度相对较宽(0.43),而岷山蟾蜍(0.09)和高原林蛙(0.22)的生态位宽度较窄,与春季相比,两栖类在秋季的食谱更宽。以利用食物种类为标准,春季高原林蛙与倭蛙的生态位重叠度(0.40)比它与岷山蟾蜍的生态位重叠度(0.33)更大。 4、畜牧业对两栖类食性及食物竞争格局的影响:以藏牦牛粪为食物或寄居场所的昆虫,如蜉金龟科、粪金龟科、毛蚊科、蝇科、丽蝇科昆虫和某些昆虫幼虫,是3种两栖类食物谱中最主要的组成部分,蜉金龟科昆虫在高原林蛙食谱中的比例更高,高原林蛙可能从畜牧业发展中获得更多的好处,使之在食物竞争方面处于优势地位。与无放牧样地相比,在有放牧样地的中,两栖类食谱中的蜉金龟科昆虫数量更多(有放牧:31.94%;无放牧:21.32%)、出现频率更高(有放牧:76.38%;无放牧:44%)。然而在不同样地上(有放牧/无放牧),两栖类的食物组成无显著性差异(P=0.188),两栖类的数量(P=0.075)、肥满度(P=0.537)均没有显著差别。 5、两栖类幼体的竞争策略:实验室条件下,通过活动性水平,变态时的体重、增长率和完成变态所需时间考察自然条件下常同水塘分布的中华蟾蜍(Bufo gargarizans)和高原林蛙蝌蚪的竞争策略。结果表明:中华蟾蜍蝌蚪在不同食物资源条件下,所选择的生存策略可能不同,即食物资源充足时,增加活动性获取更多食物,食物资源有限时,降低活动性且提前完成变态;与中华蟾蜍蝌蚪相比,在食物资源有限时高原林蛙蝌蚪获取食物能力可能更强。 This paper presented the study of competition of three amphibians (Rana kukunoris, Nanorana pleskei, Bufo minshanicus) based on spatial, temporal and dietary scales in Zoige wetland. We measured coexistence patterns of three amphibians and analyzed their ability of exploiting resource. Effects of grazing on the diet composition and diet competition of amphibians were analyzed by their diet composition during spring and autumn. Furthermore, we examined the competitive ability of larval common frogs (Rana kukunoris)and common toads(Bufo gargarizans) in a laboratory experiment, and analyzed their competitive strategies respectively. The results were as follows: 1 .The status of using spatial resource Niche breadths of B. minshanicus adults on 5 dimensional axes including character of pasture(0.41), number of yaks dung(0.42), vegetation coverage(0.20), temperature (0.50)and humidity(0.51) of ground surface were narrower than adults of R. kukunoris and N. pleskei. Niche breadths of B. minshanicus subadults were broader than R.kukunoris subadults and N.pleskei subadults on 5 dimensional axes including character of pasture (0.66), number of yaks dung (0.58), vegetation height (0.64), distance to small waterbodies (0.51), humidity of ground surface (0.79). Niche breadths of N. pleskei subadults were the narrowest in three anurans subadults on 4 dimensional axes including character of pasture (0.39), number of yaks dung (0.30), temperature (0.18) and humidity (0.33) of ground surface, niche breadths of N. pleskei adults were the broadest in three anurans adults on 4 dimensional axes including number of yaks dung (0.81), vegetation height (0.63) and coverage(0.47), distance to small waterbodies(0.68).Comparatively, niche breadths of R. kukunoris were broader on the two microclimate factors including temperature(adults:0.62;subadults:0.56) and humidity (adults:0.84;subadults:0.60)of ground surface, but was narrow on distance to small waterbodies(adults:0.27;subadults:0.14). Strategies for using habitat resource of adults and subadults of the three species anuran were different. Generally, subadults of R. kukunoris and N. pleskei needs better habitat condition. It was quite similar that three anurans exploited spatial resource, Niche overlap between R. kukunoris and N. pleskei (0.87) was greater than that between R. kukunoris and B.minshanicus(0.81). 2.Daily activity rhythm R. kukunoris audlts were active when air temperatures were as low as 0℃, R. kukunoris subadults were active at 2℃, B.minshanicus subaudlts were active at 8℃. Positive correlation was found between activities of amphibians and air temperature, Subadults of R.kukunoris, (r=0.797, p<0.001), Subadults,of,B.minshanicus, (r=0.794, p<0.001), andbadults,of,R.kukunoris(r=0.456, p<0.05).Amphibians were more active during sunny days than cloudy days. In cloudy turning into sunny, R. kukunoris and B.minshanicus subadults had two active peak: at noon about 12:30 and 15:30~16:30 pm; in cloudy, R. kukunoris and B.minshanicus subadult had two active peak too : 9:30~10:30am,15:30~16:30pm. 3.Diet analysis Aphodiidae was the most commonly consumed food item by R. kukunoris based on index of relative importance (IRI) during spring (35.28%) and autumn (28.57%) in Zogie wetland. Besides Aphodiidae, larval insect, dipterans such as Bibionidae, Muscidae, Calliphoridae also were important food item for R. kukunoris, in autumn, locust was one of important food item for R. kukunoris. The most important food item for B.minshanicus during spring (IRI:85.54%) and autumn (IRI:49.70%) was ants, following, was coleopterans, such as Aphodiidae, dung beetle. Aphodiidae (IRI:13.41%) were the most important consumed food item by N. pleskei during spring too, following, was ants and Bibionidae. Dietary breadth of N. pleskei (0.43) were greater than R. kukunoris (0.22) and B. minshanicus (0.09). As a whole, Dietary breadth of amphibians during aurumn were greater than spring. Based on prey item, dietary overlap between R. kukunoris and N. pleskei (0.40) was greater than that between R. kukunoris and B.minshanicus (0.33) during spring. 4.Effects of grazing on the diet composition and diet competition of amphibians Amphibians are an important part of the pasture ecosystems as prey and predator. In Zogie wetland, major diet of amphibians was closely associated with dung of yaks, for example, Aphodiidae, Bibionidae, Muscidae, dung beetle. Dung of yaks was major diet and habitat of these insects. Proportion of Aphodiidae was higher in diet composition of R. kukunoris than N. pleskei and B.minshanicus, with development of pasturage, R. kukunoris may have a diet competitive advantage over N. pleskei and B.minshanicus. Number of Aphodiidae in diet composition of amphibians was higher in samples with grazing (31.94%) than in those without grazing (21.32%). Occurrence Frequency of Aphodiidae in diet composition of amphibians was higher in samples with grazing (76.38%) than in those without grazing (44%). However, There was not significantly different on diet composition (P=0.188), and number (P=0.075) and the relative fatness (P=0.537) of amphibians between grazing samples and without grazing. 5.Competitive strategies of amphibian larvae I examined the competitive ability of larval toads (Bufo gargarizans) and frogs (Rana kukunoris) which co-occur in the nature pond by activity level, the growth rate and mass at metamorphosis and larval period in a laboratory experiment. The results suggest: In laborary, B.gargarizans adapted himself to different food level by changing activity. At high food level, B. gargarizans increased activity to gain more diet. At low food level, B. gargarizans decreased activity and achieved early metamorphosis. When food resource was limit, R. kukunoris could gain more food than B. gargarizans.
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Dinoflagellate cyst records were analysed from four sediment cores from the inner Oslofjord. The cores covered the pre-industrial period, and the most important period of human population growth associated with industrial development of the region, from the mid-1800s to the present, including the reported development of cultural eutrophication. Comparisons between the cyst records and the known history of eutrophication suggest cyst signals that should prove useful for tracing the development of eutrophication. The eutrophication signal consisted of a doubling of total cyst concentration, and a marked increase in one species in particular,Lingulodinium machaerophorum(from <5 to around 50% of the assemblages) with increased eutrophication. In the core considered most representative of general water quality in the inner fjord, these trends reversed back to pre-industrial levels during the 1980s and 1990s when improved sewage treatment took effect.
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Variation in dinoflagellate cyst assemblages through the last approximately 300 years was studied in two sediment cores, one from the heavily polluted Frierfjord, and one from the adjoining, relatively unpolluted Brevikfjord, in order to docu1ent possible dinoflagellate responses to pollution. Changes in the cyst-flora were compared with historical information on the development of industry and also with geochemistry of the sediments, reflecting aspects of pollution. In the Frierfjord core, increasing pollution was accompanied by a decrease in cyst concentration, possibly reflecting reduced production, at least of dinoflagellates, and a shift toward more heterotrophic species, possibly reflecting reduced light penetration in the euphotic zone, or increased production of prey for the heterotrophs. These trends seem to have reversed as pollution decreased after about 1975, suggesting that cyst assemblages contain signals that may prove useful for tracing the development of pollution. Cyst assemblages in the Brevikfjord core only showed minor changes.
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During the Last Glacial Maximum, ice sheets covered large areas in northern latitudes, and global temperatures were significantly lower than today. But few direct estimates exist of the volume of the ice sheets, or the timing and rates of change during their advance and retreat. Here we analyze four distinct sediment facies in the shallow, tectonically stable Bonaparte Gulf, Australia - each of which is characteristic of a distinct range in sea level - to estimate the maximum volume of land-based ice during the last glaciation and the timing of the initial melting phase. We use faunal assemblages and preservation status of the sediments to distinguish open marine, shallow marine, marginal marine and brackish conditions, and estimate the timing and the mass of the ice sheets using radiocarbon dating and glacio-hydroisostatic modelling. Our results indicate that from at least 22,000 to 19,000 (calendar) years before present, land-based ice volume was at its maximum, exceeding today's grounded ice sheets by 52.5 x 10 exp 6 cu km. A rapid decrease in ice volume by about 10 percent within a few hundred years terminated the Last Glacial Maximum at 19,000 +/- 250 years.
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采用孢粉分析和 1 4 C测年法 ,通过花粉植被化模拟技术 ,研究了延安地区全新世的孢粉组合特征及其古植被的演替历史。全新世时期延安地区的气候变化在全球和中国区域气候的格局下 ,也呈现出早、中、晚三个气候阶段 ,中期 (75 0 0~ 45 0 0 a)为气候最佳期 ,与之相对应的植被演替也分为三个阶段 :中期植被为松、桦、栎、漆为主具亚热带成分的暖温带落叶阔叶林 ,早期和晚期的气候较干冷 ,乔木花粉的含量减少 ,呈现以松、栎为主的暖温带针阔叶混交林
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Species in Liangzi Lake were clustered into four trophic groups: Hemiramphus kurumeus and Hemiculter bleekeri bleekeri fed predominantly on terrestrial insects; Carassius auratus auratus and Abbottina rivularis on non-animal food; Hypseleotris swinhonis, Ctenogobius giurinus, Pseudorasbora parva and Toxabramis swinhonis on cladocerans or copepods; Culterichthys erythropterus on decapod shrimps. Gut length, mouth width, mouth height, gill raker length and gill raker spacing, varied widely among species. With the exception of three species pairs (H. swinhonis, C. glurinus; C. erythropterus, H. kurumeus; T. swinhonis, H. bleekeri bleekeri), principal components analysis of morphological variables revealed over-dispersion of species. Canonical correspondence analysis of dietary and morphological data revealed five significant dietary-morphological correlations. The first three roots explained > 85% of the total variance. The first root reflected mainly the relationship of gut length to non-animal feud, with an increase in gut length associated with an increase in non-animal food. The second root was influenced strongly by the relationship of the gill raker spacing to consumption of copepods, with an increase in gill raker spacing associated positively with copepods in the diet. The third root was influenced by the relationship of mouth gape to consumption of fish and decapod shrimps, with an increase in mouth gape associated with more fish and decapod shrimps in the diet. These significant dietary-morphological relationships supported the eco-morphological hypotheses that fish morphology influence food use, and morphological variation is important in determining ecological segregation of co-existing fish species. (C) 2001 The Fisheries Society of the British Isles.
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Radiolarian distribution in surface sediments of 104 stations from northern and central South China Sea show that the abundance and diversity of radiolarians increase with the water depth and are related to radiolarian concentrations from the water column, diminished terrigenous input, variability in calcareous shell content and the rate of silica and carbonate dissolution in the deep sea. According to the appearances of individual species in surface sediments at particular depths, seven faunal boundaries distribution are recognized at water depths of 100, 450, 650, 1000, 1200, 1400 and 2500 m. Four radiolarian assemblages in the sediments were identified by applying clustering procedures. Geographic distributions of these four assemblages coincide with present-day hydrologic features of the surface waters in this area.
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The ecological characteristics of the deep-sea amoA-encoding archaea (AEA) are largely unsolved. Our aim was to study the diversity, structure and distribution of the AEA community in the sediments of the tropical West Pacific Continental Margin, to develop a general view of the AEA biogeography in the deep-sea extreme environment. Archaeal amoA clone libraries were constructed. Diverse and novel amoA sequences were identified, with the Bohol Sea, Bashi Strait and Sibuyan Sea harbouring the highest and the Bicol Shelf the lowest AEA diversity. Phylogenetic and statistical analyses illustrate a heterogeneous distribution of the AEA community, probably caused by the differential distribution of the terrestrial or estuarine AEA in the various sampling sites. The deep-sea sedimentary environments potentially harbour diverse and novel AEA in the tropical West Pacific Continental Margin. The stations in the Philippine inland seas (including station 3043) may represent AEA assemblages with various terrestrial influences and the stations connected directly to the open Philippine Sea may represent marine environment-dominant AEA assemblages. Our study indicates the potential importance of geological and climatic events in the transport of terrestrial micro-organisms to the deep-sea sedimentary environments, almost totally neglected previously.
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Bacterial surface colonization is a universal adaptation strategy in aquatic environments. However, neither the identities of early colonizers nor the temporal changes in surface assemblages are well understood. To determine the identities of the most common bacterial primary colonizers and to assess the succession process, if any, of the bacterial assemblages during early stages of surface colonization in coastal water of the West Pacific Ocean, nonnutritive inert materials (glass, Plexiglas, and polyvinyl chloride) were employed as test surfaces and incubated in seawater off the Qingdao coast in the spring of 2005 for 24 and 72 h. Phylogenetic analysis of the 16S rRNA gene sequences amplified from the recovered surface-colonizing microbiota indicated that diverse bacteria colonized the submerged surfaces. Multivariate statistical cluster analyses indicated that the succession of early surface-colonizing bacterial assemblages followed sequential steps on all types of test surfaces. The Rhodobacterales, especially the marine Roseobacter clade members, formed the most common and dominant primary surface-colonizing bacterial group. Our current data, along with previous studies of the Atlantic coast, indicate that the Rhodobacterales bacteria are the dominant and ubiquitous primary surface colonizers in temperate coastal waters of the world and that microbial surface colonization follows a succession sequence. A conceptual model is proposed based on these findings, which may have important implications for understanding the structure, dynamics, and function of marine biofilms and for developing strategies to harness or control surface-associated microbial communities.