Modelling Wetland Bird Response to Water Level Changes in the Lake Ontario – St. Lawrence River Hydrosystem

Lake Ontario and St. Lawrence River (LOSL) wetland bird abundance and diversity are greatly influenced by lake and river hydrology. Our study used an interdisciplinary ecosystem approach, blending avian and plant ecology, ecohydraulic, statistical ecology and modelling to evaluate potential impacts of water level fluctuations on indicator species representative of the wetland breeding bird assemblages in the entire LOSL freshwater system. Multi-year (2000–2003) bird surveys captured bird distribution and density in wetland habitats under varying degrees of water inandation, depth and fluctuation. Analyses revealed strong associations between estimated breeding pair densities and plant communities, water depth, and degree of water level fluctuation during the breeding season for a suite of wetland bird species using marsh, wet meadow, shrub swamp and treed swamp habitats. These quantitative associations were used to develop wetland bird performance indicators for use in a LOSL water regulation review study. Several bird species also nest at or near the water surface and are thus vulnerable to nest flooding or stranding. Changes to the seasonal hydrology of Lake Ontario and St. Lawrence River that result in an increased frequency or magnitude of these nest failure events may have a significant impact on regional population sustainability. Long term nest record databases were analyzed to create nesting flooding and stranding probability equations based on water level increases and decreases during the breeding season. These species-specific nesting relationships were incorporated into a reproduction index.Many breeding bird species were strongly associated with specific wetland plant communities. Predicted habitat suitability, as measured by estimated breeding pair density, can also change significantly within a specific wetland plant community based solely on changes in water depth during the breeding season. Three indicator species, Black Tern, Least Bittern and Virginia Rail were selected as key environmental performance indicators for alternate regulation plan comparisons.Water regulation criteria should be such that the long term diversity and abundance of wetland plant communities and frequency of spring flooding in marsh habitats during breeding are not reduced. Magnitude and frequency of water level change during the nesting season (May–July) can also adversely impact reproductive success of many wetland bird species. As such, regulation criteria that increase the seasonal magnitude and frequency of water level change may be detrimental to the long term viability of certain regional breeding bird populations.     

Development of a Grassland Integrity Index Based on Breeding Bird Assemblages

We utilized landscape and breeding bird assemblage data from three Breeding Bird Survey (BBS) routes sampled from 1965–1995 to develop and test a grassland integrity index (GII) in a mixed-grass prairie area of Oklahoma. The overall study region is extensively fragmented from long-term agricultural activity, and native habitat remnants have been degraded by recent encroachment of woody vegetation, namely eastern redcedar (Juniperus virginiana L.). The 50 individual bird survey points along the BBS routes, known as stops, were used as sample sites. Our process first focused on developing a grassland disturbance index (GDI) as a measure of cumulative landscape disturbances for these sites. The GDI was based on five key landscape variables identified in an earlier species-level study of long-term avian community dynamics: total tree, shrub, and herbaceous vegetation cover indices, overall mean landscape patch size, and grassland patch core size. The GII was then developed based on breeding bird assemblage data. Assemblages were based on commonly used response guilds reflective of five avian life history parameters: foraging mode/location, nesting location, habitat specificity, migratory pattern, and dietary guild. We tested the response of 78 candidate assemblage metrics to the GDI, and eliminated those with no or poor response or with high correlations (redundant), resulting in 13 metrics for use in the final index. Individual metric scores were scaled to fall between 0 and 10, and the cumulative index to range from 0 to 100. Although broader application and refinement are possible, the avian-based GII has an advantage over labor-intensive, habitat-based monitoring in that the GII is derived from readily available long-term BBS data. Therefore, the GII shows promise as an inexpensive tool that could easily be applied over other areas to monitor changes in regional grassland conditions.     

A Zooplankton-N:P-Ratio Indicator for Lakes

We develop the conceptual and empirical basis for a multi-level ecosystem indicator for lakes. The ratio of total N to total P in lake water is influenced or regulated by a variety of ecosystem processes operating at several organizational levels and spatial scales: atmospheric, terrestrial watershed, lake water, and aquatic community. The character of the pelagic zooplankton assemblage is shown to be well correlated with lake water N:P ratio, with species assemblages arrayed along the N:P gradient in accordance with resource supply theory. Features of specific zooplankton assemblages or deviations from expected assemblages can provide information useful for lake managers, such as the efficiency of pollutant transfer and biomagnification of toxins, loss of cool-water refuge areas, degree of zooplanktivory and food web simplification related to changes in fisheries, and assemblage changes due to anthropogenic acidification. Evaluation of the influence of watershed land use, forest cover and vegetation type, atmospheric deposition, and basin hydrology on the supply of N and P to lake ecosystems provides a means to couple changes in the terrestrial environment to potential changes in aquatic ecosystems. Deviations of lake water N:P values from expected values based on analysis of watershed and lake basin characteristics, including values inferred from appropriate diatom microfossil deposits, can provide an independent validation and baseline reference for assessing the extent and type of disturbance. Therefore, the N:P ratio of lake water can serve as a potentially useful and inexpensively obtained proxy measure for assessing changes or shifts in the biological and nutrient status of lakes.     

Effects of geomorphology, habitat, and spatial location on fish assemblages in a watershed in Ohio, USA

In this paper, we evaluate relationships between in-stream habitat, water chemistry, spatial distribution within a predominantly agricultural Midwestern watershed and geomorphic features and fish assemblage attributes and abundances. Our specific objectives were to: (1) identify and quantify key environmental variables at reach and system wide (watershed) scales; and (2) evaluate the relative influence of those environmental factors in structuring and explaining fish assemblage attributes at reach scales to help prioritize stream monitoring efforts and better incorporate all factors that influence aquatic biology in watershed management programs. The original combined data set consisted of 31 variables measured at 32 sites, which was reduced to 9 variables through correlation and linear regression analysis: stream order, percent wooded riparian zone, drainage area, in-stream cover quality, substrate quality, gradient, cross-sectional area, width of the flood prone area, and average substrate size. Canonical correspondence analysis (CCA) and variance partitioning were used to relate environmental variables to fish species abundance and assemblage attributes. Fish assemblages and abundances were explained best by stream size, gradient, substrate size and quality, and percent wooded riparian zone. Further data are needed to investigate why water chemistry variables had insignificant relationships with IBI scores. Results suggest that more quantifiable variables and consideration of spatial location of a stream reach within a watershed system should be standard data incorporated into stream monitoring programs to identify impairments that, while biologically limiting, are not fully captured or elucidated using current bioassessment methods.     

Benthic foraminifera from polluted marine environment of Sulaibikhat Bay (Kuwait)

Quantitative analyses of recent benthic foraminiferal assemblages (living and dead) were carried out on the surface sediments of Sulaibikhat Bay. Marked contrast in foraminiferal assemblages between the shallow tidal mudflats and the deep tidal channel and their relation to the extent of pollution were observed. Cluster analysis of quantitative data on the distribution of foraminiferal tests revealed three assemblages that depend mainly on the intensity of pollution; (1) a highly polluted tidal flat assemblage, (2) normal (or less polluted) mud flat assemblage and, (3) tidal channel and subtidal assemblage. The highly polluted assemblage characterized by a drop in species densities (< 100 tests/20 cm(3) sediment) but with high average diversity (5.8 Yule-Simpson Index). The microfauna of the less polluted flat displays relatively lower diversity (4.6) but high density of tests (47.2% of the total picked tests). The most abundant species of this assemblage is Ammonia tepida, displays its maximum density in this assemblage. Ammonia tepida drops in density from 17.12% to 3.07% in the polluted assemblage. Tidal channel foraminiferal assemblages should normally display lower diversities than those of tidal flats, because tidal current in the channels tend to wash away most nutrient materials. However, this is not the case of the present study area which could be due to environmental setting of the Sulaibikhat Bay in which tidal currents bring in exceptionally high amounts of nutrients from Shatt Al-Arab Estuary and in which the tidal flats are strongly and adversely polluted.     

Macroinvertebrate Assemblages on Woody Debris and Their Relations with Environmental Variables in the Lower Sacramento and San Joaquin River Drainages, California

Data from 25 sites were used to evaluate associations between macroinvertebrate assemblages on large woody debris (snags) and environmental variables in the lower San Joaquin and Sacramento River drainages in California as part of the U.S. Geological Survey's National Water Quality Assessment Program. Samples were collected from 1993 to 1995 in the San Joaquin River drainage and in 1996 and 1997 in the Sacramento River drainage. Macroinvertebrate taxa were aggregated to the family (or higher) level of taxonomic organization, resulting in 39 taxa for analyses. Only the 31 most common taxa were used for two-way indicator species analysis (TWINSPAN) and canonical correspondence analysis (CCA). TWINSPAN analysis defined four groups of snag samples on the basis of macroinvertebrate assemblages. Analysis of variance identified differences in environmental and biotic characteristics among the groups. These results combined with the results of CCA indicated that mean dominant substrate type, gradient, specific conductance, water temperature, percentage of the basin in agricultural land use, percentage of the basin in combined agricultural and urban land uses, and elevation were important factors in explaining assemblage structure. Macroinvertebrate assemblages on snags may be useful in family level bioassessments of environmental conditions in valley floor habitats.     

Visitor impact on rocky shore communities of Qeshm Island, the Persian Gulf, Iran

The influence of visitors on macroinvertebrates of rocky intertidal shores was investigated in southern coasts of the Qeshm Island, the Persian Gulf, Iran. Qeshm Island located at the Strait of Hormuz, with an area of 1,491 km², is the largest island in the region. This island consists of a number of important natural habitat types including creeks, mangroves, corals, and sandy, muddy, and rocky shores that accommodate diverse marine flora and fauna communities. Two rocky shores were selected at the touristic beaches being visited regularly, and further two control locations selected at pristine shores. Intertidal macroinvertebrates were collected from six microhabitats including rock platforms, cobbles, boulders, crevices, sea walls, and rock pools during two different periods representing high and low tourist seasons. Species richness, density, and assemblage structure in heavily visited shores were compared with that of control locations. Striped barnacles (Balanus amphitrite) were present on platforms of all locations, thus the changes in their size were used as the obvious contrast associated with visitor’s impact. A total of 70 macroinvertebrate species from 11 phyla were recorded. Significant differences were detected in taxonomic richness, density, and assemblage structure of macroinvertebrates between heavily visited and pristine shores, suggesting that macroinvertebrates were adversely affected by visitors’ impact at heavily visited shores. The test of changes in species richness, density, and assemblage structure from high to low seasons yielded mixed results. The significant changes in density and assemblage structure from high to low seasons were only observed in one heavily visited shore. A significant reduction in size of striped barnacles was observed only in one heavily visited shore. The opportunistic or fugitive species (e.g., small macroalgae and barnacles) were dominant macroinvertebrates on heavily visited shores indicating early succession stage. The results presented here showed that macroinvertebrates were adversely affected by human activities in subtropical rocky shore.     

The potential and limitations of linking biological monitoring data and restoration needs of urbanized waterways: a case study

The implementation of effective strategies to mitigate the impacts of urbanization on waterways represents a major global challenge. Monitoring data plays an important role in the formulation of these strategies. Using monitoring and historical data compiled from around an urban area (Baltimore, USA), this paper is an assessment of the potential and limitations of the use of fish assemblage monitoring data in watershed restoration. A discriminant analysis between assemblages from urban and reference sites was used to determine faunal components which have been reduced or eliminated from Baltimore area waterways. This analysis produced a strong discrimination between fish assemblages from urban and reference sites. Species primarily associated with reference sites varied taxonomically and ecologically, were generally classified as pollution intolerant, and were native. Species associated with urbanized sites were also native, varied taxonomically and ecologically, and were mixed in pollution tolerance. One factor linking most species associated with reference sites was spawning mode (lithophilic). Spawning habitat limitations may be the mechanism through which these species have been reduced in the urbanized faunas. While this presents a strong general hypothesis, information regarding the specific habitat requirements and responses to urbanization of these species is limited. This represents a limitation to producing effective restoration strategies based on exact goals and targets. Without these, determining the type and number of restoration activities required to restore ecological communities remains problematic.     

Assessing the Response of Estuarine Intertidal Assemblages to Urbanised Catchment Discharge

Measurement of intertidal rock assemblages was investigated as a potential biological indicator to provide a quantitative estimate of the impact of urbanised catchment discharge on the estuaries of Sydney, Australia, from 1995 to 1999. Based on the presence and characteristics of adjacent human activities, sampling locations were categorised as: Bush; Urban; Urban with Sewer Overflows; and Industry with Sewer Overflows. In Sydney Harbour, variation in assemblage structure was measured between most impact categories, however differences between impact categories were not consistent for each year. Nevertheless, in years of above average rainfall (1998–1999), reference assemblages adjacent to national parks and distant from urbanisation were different to all other putatively impacted assemblages. Variability within assemblages was least at reference locations in each year and greatest at locations adjacent to stormwater canals and sewer overflows, particularly in 1998–1999. Variation in assemblage structure in Sydney estuaries was most strongly correlated with chlorophyll – a concentrations. Univariate analysis also identified highly significant differences for a number of factors, however, interactions between year, impact categories and location for numerous analyses, confounded the differentiation between impact categories. The results suggest that intertidal rock assemblages in Sydney Harbour and surrounding estuaries appear to be responding to the quality and quantity of discharge from urbanised catchments and, furthermore, that assemblages are more suitable than individual taxa to indicate the difference between Bush and anthropogenically disturbed estuarine locations.     

Characterizing lentic freshwater fish assemblages using multiple sampling methods

Characterizing fish assemblages in lentic ecosystems is difficult, and multiple sampling methods are almost always necessary to gain reliable estimates of indices such as species richness. However, most research focused on lentic fish sampling methodology has targeted recreationally important species, and little to no information is available regarding the influence of multiple methods and timing (i.e., temporal variation) on characterizing entire fish assemblages. Therefore, six lakes and impoundments (48–1,557 ha surface area) were sampled seasonally with seven gear types to evaluate the combined influence of sampling methods and timing on the number of species and individuals sampled. Probabilities of detection for species indicated strong selectivities and seasonal trends that provide guidance on optimal seasons to use gears when targeting multiple species. The evaluation of species richness and number of individuals sampled using multiple gear combinations demonstrated that appreciable benefits over relatively few gears (e.g., to four) used in optimal seasons were not present. Specifically, over 90 % of the species encountered with all gear types and season combinations (N?=?19) from six lakes and reservoirs were sampled with nighttime boat electrofishing in the fall and benthic trawling, modified-fyke, and mini-fyke netting during the summer. Our results indicated that the characterization of lentic fish assemblages was highly influenced by the selection of sampling gears and seasons, but did not appear to be influenced by waterbody type (i.e., natural lake, impoundment). The standardization of data collected with multiple methods and seasons to account for bias is imperative to monitoring of lentic ecosystems and will provide researchers with increased reliability in their interpretations and decisions made using information on lentic fish assemblages.     

Maryland Biological Stream Survey: Development of a Fish Index of Biotic Integrity

As a step towards determining the extent of degradation in non-tidal streams, a multi-metric Index of Biotic Integrity (IBI) based on fish assemblages was developed for the Maryland Biological Stream Survey (MBSS). The MBSS is a probability-based statewide sampling program designed to assess the status of biological resources and to evaluate the effects of anthropogenic activities. We used data from 419 MBSS sites sampled in 1994-95 to develop the IBI. Two distinct geographic strata, corresponding with ecoregional and physiographic boundaries, were identified via cluster analysis and multivariate analysis of variance (MANOVA) as supporting distinctly different species groups. Reference conditions were based on minimally degraded sites. We quantitatively evaluated the ability of various attributes of the fish assemblage (candidate metrics) to discriminate between these reference sites and sites known to be degraded, using statistical tests and classification efficiency. Provisional formulations of the IBI were selected for each region based on high classification efficiency and broad representation of fish assemblage attributes. Fish IBI scores for 1995 MBSS sites spanned a wide range of biological conditions, from good to very poor. Over all six basins sampled in 1995, half of the stream miles fell into the range of good to fair. Roughly 25% of stream miles showed some degradation. The IBI will be used in conjunction with physical and chemical data to answer critical questions about the health of Maryland streams and the relative impacts of human-induced stresses on the state's aquatic systems.     

Assessing the wildlife habitat value of New England salt marshes: II. Model testing and validation

We tested a previously described model to assess the wildlife habitat value of New England salt marshes by comparing modeled habitat values and scores with bird abundance and species richness at sixteen salt marshes in Narragansett Bay, Rhode Island USA. As a group, wildlife habitat value assessment scores for the marshes ranged from 307-509, or 31-67% of the maximum attainable score. We recorded 6 species of wading birds (Ardeidae; herons, egrets, and bitterns) at the sites during biweekly survey. Species richness (r (2)=0.24, F=4.53, p=0.05) and abundance (r (2)=0.26, F=5.00, p=0.04) of wading birds significantly increased with increasing assessment score. We optimized our assessment model for wading birds by using Akaike information criteria (AIC) to compare a series of models comprised of specific components and categories of our model that best reflect their habitat use. The model incorporating pre-classification, wading bird habitat categories, and natural land surrounding the sites was substantially supported by AIC analysis as the best model. The abundance of wading birds significantly increased with increasing assessment scores generated with the optimized model (r (2)=0.48, F=12.5, p=0.003), demonstrating that optimizing models can be helpful in improving the accuracy of the assessment for a given species or species assemblage. In addition to validating the assessment model, our results show that in spite of their urban setting our study marshes provide substantial wildlife habitat value. This suggests that even small wetlands in highly urbanized coastal settings can provide important wildlife habitat value if key habitat attributes (e.g., natural buffers, habitat heterogeneity) are present.     

Relation of Environmental Characteristics to Fish Assemblages in the Upper French Broad River Basin, North Carolina

Fish assemblages at 16 sites in the upper French Broad River basin, North Carolina were related to environmental characteristics using detrended correspondence analysis, principal components analysis, and linear regression. The primary gradient affecting sites in this basin was related to agricultural influence, characterized by high levels of agricultural land cover, nitrate plus nitrite, sulfate, specific conductance, and sediment. Agricultural influence on the fish assemblage was represented as a trophic shift from specialized insectivores to generalized insectivores and an herbivore. A secondary influence on variation among sites was related to urban land cover, population density, increased concentrations of metals, and soil erodibility. This primarily urban gradient was characterized by an increase in the number of native and introduced fish species, particularly sunfish and omnivores species, and a decline in the percent of piscivores. These results support the identification of indicators for different environmental influences, which can improve the ability of resource managers to diagnose impairment in this basin and in similar basins.     

Benthic macrofaunal assemblages of the San Francisco Estuary and Delta, USA

The spatial and temporal distribution of macrobenthic assemblages in the San Francisco Estuary and Sacramento–San Joaquin River Delta were identified using hierarchical cluster analysis of 501 samples collected between 1994 and 2008. Five benthic assemblages were identified that were distributed primarily along the salinity gradient: (1) a polyhaline assemblage that inhabits the Central Bay, (2) a mesohaline assemblage that inhabits South Bay and San Pablo Bay, (3) a low-diversity oligohaline assemblage primarily in Suisun Bay, (4) a low-diversity sand assemblage that occurs at various locations throughout the Estuary, and (5) a tidal freshwater assemblage in the Delta. Most sites were classified within the same assemblage in different seasons and years, but a few sites switched assemblage designations in response to seasonal changes in salinity from freshwater inflows.     

Benthic foraminiferal assemblages as pollution proxies in the northern coast of Gabes Gulf,Tunisia

A study of chemical and sedimentological parameters integrated with benthic foraminifera investigation was conducted along the northern coast of Gabes Gulf. Thirty-two samples were studied and a total of 68 benthic foraminiferal species were identified. Heavy metals enrichment factors and total hydrocarbon concentrations showed both metal and petrogenic pollution related mainly to phosphogypsum, sewage, and fishing activities. Statistical analysis (bivariate correlation and hierarchical cluster analysis) show a possible control of these pollutants on density, diversity, as well as the taxonomic composition of the benthic foraminiferal assemblages. The extent to which the population was found less dense and less diversified corresponded to the degree to which the sediment was contaminated. In these contaminated sites, an increase in relative abundance of opportunistic species such Ammonia tepida and Haynesina germanica was found. Far from pollution, foraminiferal assemblages are dominated by species characteristic of Mediterranean shallow water (Ammonia beccarii, Ammonia parkinsoniana, Elphidium crispum, Elphidium williamsoni, Elphidium advenum, Peneroplis planatus, Peneroplis pertesus).     

Bird Species Assemblages as Indicators of Biological Integrity in Great Basin Rangeland

The study evaluates the potential for bird species assemblages to serve as indicators of biological integrity of rangelands in the Great Basin in much the same way that fish and invertebrate assemblages have been used as indicators in aquatic environments. Our approach was to identify metrics of the bird community using relatively simple sampling methods that reflect the degree of rangeland degradation and are consistent over a variety of vegetation types and geographic areas. We conducted the study in three range types (i.e., potential natural plant community types) in each of two widely separated areas of the Great Basin: south-eastern Idaho (sagebrush steppe range types) and west-central Utah (salt-desert shrub range types). Sites were selected in each range type to represent three levels of grazing impact, and in Idaho included sites modified for crested wheatgrass production. Birds were sampled by point counts on 9 100-m radius plots at 250-m spacing on each of 20 sites in each area during the breeding season. In sagebrush-steppe, 964 individuals in 8 species of passerine birds were used in analyses. Five metrics were significantly related to impact class, both when analyzed within range type and when analyzed with all range types combined. Species richness, relative abundance of shrub obligate species, and relative abundance of Brewer's sparrow were generally lower for the higher impact classes, whereas the reverse was true for dominance by a single species and for relative abundance of horned larks. In contrast, total number of individuals did not differ significantly as a function of impact class. In salt-desert shrub, a total of 843 birds in 4 species were included in analyses, 98% of which were horned larks. None of the metrics identified above was significantly related to impact class. Two metrics for breeding birds in sagebrush steppe (species richness and dominance) showed little overlap between values for the extremes of impact class, and thus they have potential as indicators of biological integrity. However, the sensitivity of these metrics appears to be greatest at the high impact end of the spectrum, which suggests they may have limited utility in distinguishing between sites having light and moderate impact.     

Littoral diatoms as indicators of recent water and sediment contamination by metals in lakes

We studied the response of benthic diatoms to recent metal contamination in littoral cores collected at 25 sites in 11 lakes situated at different distances from a smelter in the Rouyn-Noranda mining region (Quebec). Diatom response was described in terms of density, diversity, and taxonomic composition of the entire assemblages and as abundance of individual indicator taxa. Metal concentrations were measured in sediment and in the overlying water (as total dissolved and as free-ions). Sediment metal contamination was significantly higher in lakes located <10 km from the smelters than in lakes farther away. Such difference was not significant when metal concentrations in the overlying water were considered. Metal contamination did not affect diatom density, which indeed was highest in the most contaminated lake. Diversity (either measured as number of taxa or as Shannon and evenness indices) was instead significantly higher in lakes close to the smelter than elsewhere. Redundancy analysis indicated that diatom composition changed along a gradient in alkalinity (CO?) and one in sediment metal contamination (Cd, Hg, Cu). We identified three diatom taxa (Fragilaria construens var. venter, F. construens var. pumila, and Brachysira vitrea) that increased in relative and absolute abundance with metal contamination. Benthic diatom responses at the community (density, diversity, assemblage composition) and population levels (abundance of selected benthic taxa) were stronger to the sediment metal contamination than to the contamination of overlying water. Comparisons with available literature indicated that, for monitoring recent sediment contamination, diatoms in littoral sediments are preferable to invertebrates that mostly respond to overlying water. Diatoms in littoral cores are therefore unique as tools for monitoring recent contamination of lake sediments.     

Landscape Correlates of Breeding Bird Richness Across the United States Mid-Atlantic Region

Using a new set of landscape indicator data generated by the U.S.EPA, and a comprehensive breeding bird database from the National Breeding Bird Survey, we evaluated associations between breeding bird richness and landscape characteristics across the entire mid-Atlantic region of the United States. We evaluated how these relationships varied among different groupings (guilds) of birds based on functional, structural, and compositional aspects of individual species demographics. Forest edge was by far the most important landscape attribute affecting the richness of the lumped specialist and generalist guilds; specialist species richness was negatively associated with forest edge and generalist richness was positively associated with forest edge. Landscape variables (indicators) explained a greater proportion of specialist species richness than the generalist guild (46% and 31%, respectively). The lower value in generalists may reflect finer-scale distributions of open habitat that go undetected by the Landsat satellite, open habitats created by roads (the areas from which breeding bird data are obtained), and the lumping of a wide variety of species into the generalist category. A further breakdown of species into 16 guilds showed considerable variation in the response of breeding birds to landscape conditions; forest obligate species had the strongest association with landscape indicators measured in this study (55% of the total variation explained) and forest generalists and open ground nesters the lowest (17% of the total variation explained). The variable response of guild species richness to landscape pattern suggests that one must consider species' demographics when assessing the consequences of landscape change on breeding birds.     

湖泊微生物群落构建机制及研究展望

湖泊微生物生态过程研究是深入了解湖泊生态系统结构与功能的关键。论述了湖泊微生物多样性时空分布规律及群落构建机制研究进展,总结了微生物群落构建机制的分析方法,介绍了微生物生态网络构建原理及应用。群落构建机制分析方法分为统计分析法、模型推断法和生态网络分析法。统计分析法包括群落结构差异分析、群落结构-环境因子关联分析和方差分解分析等,此类方法能够初步识别驱动群落组成与结构时空差异的影响因子,判别空间因素与已知环境变量对群落构建过程的相对贡献;模型推断法包括中性群落模型方法和零模型方法等,能够进一步实现对群落构建生态过程的区分,量化和比较随机性因素及确定性因素的相对重要性;生态网络分析法可用于揭示物种共现模式,探究作为确定性因素的生物相互作用,也可用于物种-环境响应关系的研究,探究环境选择过程对群落结构的影响。     

An assessment of macroinvertebrate assemblages in mosquito larval habitats—space and diversity relationship

The aquatic bodies designated as mosquito larval habitats are diverse in size and species composition. The macroinvertebrate predators in these habitats are elements that influence the abundance of mosquito species, providing a basis for biological control. Assessment of species assemblage in these habitats will indicate the possible variations in the resource exploitation and trophic interactions and, therefore, can help to frame biological control strategies more appropriately. In the present study, the species composition is being investigated in five different mosquito larval habitats at a spatial scale. A random sample of 80 each of the habitats, grouped as either small or large, was analyzed in respect to the macroinvertebrate species assemblage. The species composition in the habitats was noted to be an increasing function of habitat size (species number = 1.653 + 0.819 habitat size) and, thus, the diversity. The relative abundance of the mosquito immatures varied with the habitat, and the number of useful predator taxa was higher in the larger habitats. In the smaller habitats—plastic and earthen structures and sewage drains, the relative and absolute number of mosquito immatures per sampling unit were significantly higher than the pond and rice field habitats. This was evident in the cluster analysis where the smaller habitats were more related than the larger habitats. The principal component analysis on the species diversity yielded four and six components, respectively, for the smaller and larger habitats for explaining the observed variance of species abundance. The species composition in the habitats was consistent with the earlier findings and support that the abundance of coexisting macroinvertebrate species regulates the relative load of mosquito immatures in the habitats. The findings of this study may be further tested to deduce the relative importance of the habitats in terms of the productivity of mosquito immatures at a temporal scale.