Intra-habitat heterogeneity of microbial food web structure under the regime of eutrophication and sediment resuspension in the large subtropical shallow Lake Taihu, China

Planktonic microbial community structure and classical food web were investigated in the large shallow eutrophic Lake Taihu (2338 km(2), mean depth 1.9 m) located in subtropical Southeast China. The water column of the lake was sampled biweekly at two sites located 22 km apart over a period of twelve month. Site 1 is under the regime of heavy eutrophication while Site 2 is governed by wind-driven sediment resuspension. Within-lake comparison indicates that phosphorus enrichment resulted in increased abundance of microbial components. However, the coupling between total phosphorus and abundance of microbial components was different between the two sites. Much stronger coupling was observed at Site 1 than at Site 2. The weak coupling at Site 2 was mainly caused by strong sediment resuspension, which limited growth of phytoplankton and, consequently, growth of bacterioplankton and other microbial components. High percentages of attached bacteria, which were strongly correlated with the biomass of phytoplankton, especially Microcystis spp., were found at Site 1 during summer and early autumn, but no such correlation was observed at Site 2. This potentially leads to differences in carbon flow through microbial food web at different locations. Overall, significant heterogeneity of microbial food web structure between the two sites was observed. Site-specific differences in nutrient enrichment (i.e. nitrogen and phosphorus) and sediment resuspension were identified as driving forces of the observed intra-habitat differences in food web structure.

板北断块油藏储层均质特征与剩余油分布研究

With the growing development and perfection of reservoir describing technology, its research achievements have played an increasingly important role in old oilfields in recent years. Reservoir description quantitatively describes, characterizes and predicts every kind of reservoir characters in 3D space. The paper takes Banbei block reservoir as an object, studies the reservoir characters and residual oil distributing characteristics of gravity flow genetic reservoir, and definitudes potential adjustment direction of reservoir development. Main achievements are gained as follows. Through fine correlation of strati graphic sequence, the classification of layers and single sands of main payzones in Banbei block is ascertained, the classifying methods of sedimentary unit in gravity flow reservoir characterized with picked cyclical marker bed are formed. On the basis of comprehensive logging evaluation, depositional characters of Banbei block are studied, and classifying methods of sedimentary microfacies in gravity flow reservoir are described. The sedimentary background of main oil layers in Banbei block is open lake with shallow water, and belongs to lacustrine underwater gravity flow- lacustrine phase depositional system. Main microfacies types are underwater water course^ water course side-wing, underwater floodplain, between two water courses, and lacustrine mud, etc. Reservoir sands mainly are underwater water course sands. Influenced by distributing characters of gravity flow underwater water course, sand shapes in plane mainly are stripe, finger-shape, tongue-shape. Sand distribution shows obvious split property. Sands overlap each other. According to comprehensive analysis of lithologic data, logging parameters, and dynamic production data, the researching threads and methods of reservoir heterogeneous characters are perfected. The depositional characters of gravity flow underwater water course in Banbei block determine its high reservoir heterogeneity. Macroscopic heterogeneity is studied in many aspects such as the scale of layers, the scale of single sands, in-situ scale, the distribution of interlayer types, the interlayer scale, and heterogeneity in plane. Thus, heterogeneous characters of reservoir are thoroughly analyzed. Through microscopic research of reservoir, the types of porous structure and related parameters are determined. According to the analysis of dynamic production data, the reaction and inner influential factors of reservoir heterogeneity in waterflood development are further revealed. Started with the concept and classifying methods of flow unit, clustering classification which can better meet the requirements of production is formed. The flow unit of Banbei block can be classified into four types. According to comprehensive evaluation, the first and second type of flow unit have better percolating capability and reserving capability. Research thread of 3D model-building and reservoir numerical simulation combined as an integral is adopted. The types and characters of residual oil distribution are determined. Residual oil of Banbei block mainly distributes in the boundary of sands, near the faults, areas with non-perfect injection-production well pattern , undeveloped sands, vertically poor developed layers. On the basis of comprehensive reservoir study, the threads and methods of improving development effect towards reservoir with high water cut, high recovery percent, serious heterogeneity are ascertained. The whole waterflood development effect of Banbei block reservoir is good. Although its water cut and recovery percent is relatively high, there is still some potential to develop. According to depositional characters of gravity flow and actual production situation? effective means of further improving development level are as follows. We should drill new wells in every kind of areas abounding with residual oil, implement comprehensive measures such as increasing liquid discharge, cyclic waterflood, changing fluid direction when injection-production well pattern is perfected, improve water quality, enhance displacement efficiency in flooding.

Explicit representation of subgrid heterogeneity in a GCM land-surface scheme

Essery, R L H, Best, M J, Betts, R A, Cox, P M & Taylor, C M, Explicit representation of subgrid heterogeneity in a GCM land-surface scheme. Journal of Hydrometeorology 4, pp 530-543 (2003).

A Phylogenetic Mixture Model for Detecting Pattern-Heterogeneity in Gene Sequence or Character-State Data

Mark Pagel, Andrew Meade (2004). A phylogenetic mixture model for detecting pattern-heterogeneity in gene sequence or character-state data. Systematic Biology, 53(4), 571-581. RAE2008

Cost Heterogeneity and the Potential Savings from Market-Based Policies

Policy makers and analysts are often faced with situations where it is unclear whether market-based instruments hold real promise of reducing costs, relative to conventional uniform standards. We develop analytic expressions that can be employed with modest amounts of information to estimate the potential cost savings associated with market-based policies, with an application to the environmental policy realm. These simple formulae can identify instruments that merit more detailed investigation. We illustrate the use of these results with an application to nitrogen oxides control by electric utilities in the United States.

Suppression of conformational heterogeneity at a protein-protein interface.

Staphylococcal protein A (SpA) is an important virulence factor from Staphylococcus aureus responsible for the bacterium's evasion of the host immune system. SpA includes five small three-helix-bundle domains that can each bind with high affinity to many host proteins such as antibodies. The interaction between a SpA domain and the Fc fragment of IgG was partially elucidated previously in the crystal structure 1FC2. Although informative, the previous structure was not properly folded and left many substantial questions unanswered, such as a detailed description of the tertiary structure of SpA domains in complex with Fc and the structural changes that take place upon binding. Here we report the 2.3-Å structure of a fully folded SpA domain in complex with Fc. Our structure indicates that there are extensive structural rearrangements necessary for binding Fc, including a general reduction in SpA conformational heterogeneity, freezing out of polyrotameric interfacial residues, and displacement of a SpA side chain by an Fc side chain in a molecular-recognition pocket. Such a loss of conformational heterogeneity upon formation of the protein-protein interface may occur when SpA binds its multiple binding partners. Suppression of conformational heterogeneity may be an important structural paradigm in functionally plastic proteins.

Spatial Heterogeneity and Genetic Variation in the Copepod Neocalanus Cristatus Along Two Transects in the North Pacific Sampled By the Continuous Plankton Recorder

We present a macrogeographic study of spatial heterogeneity in an important subarctic Pacific copepod and describe the first genetic analysis of population structure using Continuous Plankton Recorder (CPR) samples. Samples of Neocalanus cristatus were collected at a constant depth of similar to 7 m from two CPR tow-routes, (i) an east-west similar to 6500-km transect from Vancouver Island, Canada to Hokkaido Island, Japan, and (ii) a north-south transect of similar to 2250 km from Anchorage, Alaska to Tacoma, Washington. Analysis of these samples revealed three features of the biology of N. cristatus. First, N. cristatus undergoes small-scale diel vertical migration that is larger among stages CV- adult (3-6 times more abundant at 7 m at night), than stages CI-CIV (only 2-4 times higher at night). Secondly, while there were no regions where N. cristatus did not appear, each transect sampled a few large-scale macrogeographic patches. Thirdly, an analysis of molecular variation, using a partial sequence of the N. cristatus cytochrome oxidase I gene, revealed that 7.3% (P < 0.0001) of the total genetic variation among N. cristatus sampled from macrogeographic patches by the CPR could be explained by spatial heterogeneity. We suggest that spatial heterogeneity at macrogeographic scales may be important in plankton evolution.

Temporal and spatial variation in the Nazaré Canyon (Western Iberian margin): Inter-annual and canyon heterogeneity effects on meiofauna biomass and diversity

The Nazaré Canyon on the Portuguese Margin (NE Atlantic) was sampled during spring-summer for three consecutive years (2005–2007), permitting the first inter-annual study of the meiofaunal communities at the Iberian Margin at two abyssal depths (~3500 m and ~4400 m). Using new and already published data, the meiofauna standing stocks (abundance and biomass) and nematode structural and functional diversity were investigated in relation to the sediment biogeochemistry (e.g. organic carbon, nitrogen, chlorophyll a, phaeopigments) and grain size. A conspicuous increase in sand content from 2005 to 2006 and decrease of phytodetritus at both sites, suggested the occurrence of one or more physical disturbance events. Nematode standing stocks and trophic diversity decreased after these events, seemingly followed by a recovery/recolonisation period in 2007, which was strongly correlated with an increase in the quantity and bioavailability of phytodetrital organic matter supplied. Changes in meiofauna assemblages, however, also differed between stations, likely because of the contrasting hydrodynamic and food supply conditions. Higher meiofauna and nematode abundances, biomass and trophic complexity were found at the shallowest canyon station, where the quantity, quality and bioavailability of food material were higher than at the deeper site. The present results suggest that even though inter-annual variations in the sedimentary environment can regulate the meiofauna in the abyssal Nazaré Canyon, heterogeneity between sampling locations in the canyon were more pronounced.

Heterogeneity of impacts of high CO2 on the North Western European Shelf

The increase in atmospheric CO2 is a dual threat to the marine environment: from one side it drives climate change, leading to modifications in water temperature, circulation patterns and stratification intensity; on the other side it causes a decrease in marine pH (ocean acidification, or OA) due to the increase in dissolved CO2. Assessing the combined impact of climate change and OA on marine ecosystems is a challenging task. The response of the ecosystem to a single driver can be highly variable and remains still uncertain; additionally the interaction between these can be either synergistic or antagonistic. In this work we use the coupled oceanographic–ecosystem model POLCOMS-ERSEM driven by climate forcing to study the interaction between climate change and OA. We focus in particular on carbonate chemistry, primary and secondary production. The model has been run in three different configurations in order to assess separately the impacts of climate change on net primary production and of OA on the carbonate chemistry, which have been strongly supported by scientific literature, from the impact of biological feedbacks of OA on the ecosystem, whose uncertainty still has to be well constrained. The global mean of the projected decrease of pH at the end of the century is about 0.27 pH units, but the model shows significant interaction among the drivers and high variability in the temporal and spatial response. As a result of this high variability, critical tipping point can be locally and/or temporally reached: e.g. undersaturation with respect to aragonite is projected to occur in the deeper part of the central North Sea during summer. Impacts of climate change and of OA on primary and secondary production may have similar magnitude, compensating in some area and exacerbating in others.