Microscale investigations of microbial communities in coastal surficial sediments

The upper millimeters of sediments are considered major locations of microbial colonization and activity. The goal of our study was to investigate variations of microbial communities in the uppermost sediment layers of the coastal Baltic Sea with emphasis on the complex interplay between microbiology and physico‐chemical sediment properties. We selected a high‐resolution methodological approach that combined the cryolanding sampling technique (spatial resolution of 250 μm) with microsensor‐, spectrophotometric and microscopic analyses. While the oxygen penetration depths in dark conditions ranged from 1.4 mm to 2.6 mm during the study period, this zone expanded by about 1 mm in light and could be divided into three micro‐horizons: (i) an upper zone with a high net O₂ production, (ii) an intermediate zone with increased O₂ consumption on account of light‐stimulated respiration and (iii) a lower zone with lower O₂ consumption. Time‐series experiments revealed a rapid response of the benthic microbial community to altered light intensities. In May and July, the net O₂ budget in the porewater of sediments was positive within 35 and 22 min after illumination, respectively, whereas in June O₂ production exceeded O₂ consumption after 112 min. The thickness of the O₂ production and O₂ consumption micro‐zones decreased from May to July coinciding with an increase in temperature. In May, sites of enhanced O₂ consumption were closely associated with subsurface maxima of microbial numbers and enzymatic activities indicating a tight coupling between photoautotrophic and heterotrophic processes between 1‐ and 2‐mm depth. In June and July, the microbial abundance and enzymatic activity hardly varied with depth. Spatial and temporal microheterogeneity of microbial distribution and activity in O₂ gradients was seen as a reflection of the complex interplay between microbiology and physico‐chemical sediment properties.     

塔里木河下游丛枝菌根植物的侵染

通过对塔里木河下游自然和人工植物群落中的15种主要建群种植物根系菌根的定殖状况的调查及对菌根侵染部位、菌根中的泡囊、丛枝和菌丝的观察,其结果显示:其中11种植物可被AM真菌侵染,占所调查植物种总数的73.33%,野生乡土植物表现出较高的菌根侵染率和侵染强度,其中有84.62%的植物为菌根植物,且乔木、多年生草本和灌木类植物全部为菌根植物,一年生草本植物未见AM真菌侵染;人工引入种蓼科的泡果沙拐枣(Calligonum junceum)和藜科的梭梭柴(Haloxylon ammodendron)均未见有AM真菌侵染。丛枝菌根真菌侵染率、侵染强度与植物所属的科属关系较密切,也与真菌群落所处时空环境及土壤深度有关。     

旅游屏蔽区的城市空间拓展研究--以临潼为例

旅游地的屏蔽效应是当前学术界研究的热点。以临潼为实例,对这一典型旅游屏蔽区发展的障碍因素进行分析,在此基础上探讨了其空间拓展理念,并且从城市空间格局完善、景观安全格局营造、景观房产等角度界定其拓展方向。最后探讨了该案例的拓展意义、关键突破点与现实意义。     

A practical device for evaluating periphyton colonization dynamics in tropical shallow wetlands

Here, we have presented a field device for sampling periphyton in lentic systems, with a tropical lowland wetland in Colombia as the model system. The periphyton sampler (PS) is composed of a central soft iron pole to which rectangular woody boxes and glass slides are attached to lateral iron axes, which can be distributed at different depths. Our PS can be used to evaluate changes in the richness and density of algal communities at different scales as well as in water quality studies.     

Land Use Change in New Spain: A Three-Dimensional Historical GIS Analysis

The introduction of European livestock into the New World resulted in extensive land use changes. Studying the spatiality of these changes as they actually transpired in a three-dimensional landscape can enhance our knowledge of the environmental transformations that accompanied colonization. This article focuses on a case study area in New Spain, roughly equivalent to present-day Mexico, wherein forty-seven sheep ranches were established through viceregal land grants between 1535 and 1610. An integration of fieldwork, textual analysis of land grants, and imagery analysis enables these ranches to be mapped in a three-dimensional geographic information system (GIS) environment. Once mapped in a GIS, the spatial statistics of each ranch's elevation, slope, and aspect (slope orientation) can be calculated to identify spatio-temporal patterns of land use change. These spatio-temporal patterns can be interpreted within the highly localized contexts of land granting to amplify our understanding of human–environment interaction in New Spain. This article's key findings are that grantees harbored a persistent preference for south-facing land; ranches clustered most heavily on isolated elevations; viceregal ordinances were effective at keeping livestock away from low-lying, agriculturally productive zones; and, as a consequence of native population decline and forced native resettlements, the midelevations experienced a land use change from semiterraced agriculture to ranching. These results offer a fresh perspective on the local-scale processes of land use change that resulted from the European colonization of the New World.     

Colonization and Probiotic Effect of Metschnikowia sp. C14 in the Intestine of Juvenile Sea Cucumber,Apostichopus japonicus

Viable cell count was used to determine whether Metschnikowia sp.C14 can colonize the intestine of juvenile sea cucumber Apostichopus japonicus.Sea cucumber individuals were divided into two groups,which were fed the control diet for 38 days or the C14-supplemented diet at 105 cells g−1 diet for 28 days,then the control diet from day 29 to day 38.The number of C14 cells in the intestine of sea cucumber fed the C14-supplemented diet significantly increased from day 7 to day 28,and decreased from day 29 to day 38.Sea cucumber fed with the diet containing C14 showed a significant increase in trypsin activity and lipase activity from day 21 to day 33 compared with the control.Feeding C14 significantly improved the phagocytic activity and respiratory burst in coelomocytes from day 21 to day 35 and from day 14 to day 38,respectively.In addition,there was an obvious enhancement in lysozyme activity(from day 21 to day 38 or day 33),phenoloxidase activity(from day 21 to day 28)and total nitric oxide synthase activity(from day 14 to day 38)in coelomic fluid supernatant and/or coelomocyte cell lysate supernatant compared with the control.There were significant positive correlations between the number of C14 cells colonizing the intestine and trypsin activity of the intestine,lysozyme activity of the coelomic fluid supernatant and coelomocyte lysate supernatant from sea cucumber.These data suggested that the number of C14 cells should be maintained at 105 cfu(colony-forming units)g−1 intestine material for the maximum benefit.     

Weathered IXTOC I oil effects on estuarine benthos

The impact of weathered IXTOC I oil on experimental benthic communities colonized in the laboratory and in situ was observed. Test systems containing clean sand and receiving seawater from Aransas Pass Inlet were placed in the laboratory while similar systems were placed on the seafloor. All of these test systems were allowed to colonize for 8 weeks by settlement of planktonic larvae. Weathered IXTOC I oil was added to randomly selected laboratory and in situ replicate compartments within the test systems and these were then exposed to flowing seawater in the laboratory for an additional 4 weeks. Observations of the structure and biomass of the communities at the end of the 12-week period indicated no significant effects on the laboratory colonized communities. However, total density was significantly affected in the in situ colonized systems as was species composition. Although not significant, total biomass was substantially reduced by oiling. Eh measurements of sediments showed that the oil reduced the depth of the oxygenated layer approximately half. This reduction may reduce subsurface benthic production and alter processes such as nutrient regeneration.     

Adaptive Ecology, Growth Strategies and the Global Bloom Expansion of Dinoflagellates

Dinoflagellates exhibit unique differences from diatoms in their adaptive ecologies that may be favoring their increasingly successful exploitation of coastal waters and global bloom expansion. Dinoflagellates behave as annual species, bloom soloists, are ecophysiologically diverse and habitat specialists, whereas diatoms behave as perennial species, guild members and are habitat cosmopolites. Diatoms have a relatively uniform bloom strategy based on species-rich pools and exhibit limited habitat specialization. Dinoflagellates have multiple life-form strategies consistent with their diverse habitat specializations, but rely on impoverished bloom species pools. Niche structure and dinoflagellate competition for niche space are considered. The “open niche period” formulated originally for Narragansett Bay is extrapolated as a general bloom paradigm. It is suggested that successful niche occupancy leading to blooms involves adaptive strategies at three heirarchic taxonomic elements: phylogenetic, generic and species-specific, and in that sequence. Transoceanic expatriation of emigrant species leading to indigenous status and blooms requires completion of a three-stage colonization process. Anthropogenic seedings are not, in themselves, bloom stimulation events; they are only the first phase of a multiple-step process. The organismal and niche features required for a hidden flora member to become a bloom species are considered, and the interplay between niche structure, habitat carrying capacity, colonization requirements and stochasticity as factors in the changing global bloom behavior of dinoflagellates discussed. The question is posed whether traditional perspectives of phytoplankton behavior apply completely to dinoflagellates. This revised version was published online in August 2006 with corrections to the Cover Date.     

Primitivism and the other. History of art and cultural geography

The article advocates an articulation of cultural geography and art history, and in this perspective focuses on the analysis of the primitivist movement and particularly on Gauguin's work and personal itinerary. Primitivism introduced artefacts of ‘primitive’ people into the history of Western art and signalled a change in the relationship between the West and the ‘Other’ and ‘Elsewhere’. This reversal of values has a major geographical dimension. Primitivism manifests the contradiction-rife colonial ideology, but can also challenge colonization. Tourism, which is, in the case of Tahiti, directly linked to Gauguin and to his myth, inherited a lot from primitivism, in terms of hopes and ambiguities. Conversely, primitivism casts light on geographical features of these places, instituted as ‘Elsewheres‘ by the West, and visited, even transformed by painters, colonizers and tourists. This revised version was published online in July 2006 with corrections to the Cover Date.