Detecting anthropogenic disturbance in an environment with multiple gradients of physical disturbance,Manukau Harbour,New Zealand

Demonstrating spatial or temporal gradients of effects on macrobenthic communities can be a useful way of providing strong empirical evidence of natural or anthropogenic disturbance. Gradient designs for environmental assessment are sensitive to change for point source data, enabling the scale of the effects of a disturbance to be readily identified. If the spatial scale that is sampled from the point source is adequate, problems of selecting control sites can be avoided. However, sources of spatial variation in macrobenthic communities, which are not related to the impact, can confound the use of gradient designs. This can occur if the natural spatial structure overlaps that of the gradient and cannot be identified either as a location or environmental covariable. The ability to detect point source impacts using a gradient design against natural spatial variability was tested using benthic macrofaunal data collected from Manukau Harbour, New Zealand. Treated sewage wastewater is discharged into the north-west area of the Manukau Harbour. Sandflats in the vicinity of the outfall are also subject to physical disturbance from wind-waves and strong tides. Ordination techniques and the testing of a priori predictions were used to try and separate the relative effects of organic and physical disturbance on the benthic communities. While the occurrence of other environmental disturbances along a gradient of anthropogenic disturbance makes interpretation of community pattern more difficult, the use of a gradient sampling layout, ordination analysis and the testing of a priori predictions enabled impacts of the anthropogenic and natural environmental disturbances to be interpreted. Gradient designs, therefore, provide a method of assessing complex impacts that operate over broad spatial and temporal scales.     

Microsatellite markers provide evidence for sexual reproduction of Mycosphaerella graminicola in Saskatchewan.

This study examined the genetic structure of a Saskatchewan population of Mycosphaerella graminicola, cause of the foliar disease Septoria tritici blotch of wheat. Such knowledge is valuable for understanding the evolutionary potential of this pathogen and for developing control strategies based on host resistance. Nine pairs of single-locus microsatellite primers were used to analyze the genomic DNA of 90 isolates of M. graminicola that were collected using a hierarchical sampling procedure from different locations, leaves, and lesions within a wheat field near Saskatoon. Allelic series at eight different loci were detected. The number of alleles per locus ranged from one to five with an average of three alleles per locus. Genetic diversity values ranged from 0.04 to 0.67. Partitioning the total genetic variability into within- and among-location components revealed that 88% of the genetic variability occurred within locations, i.e., within areas of 1 m(2), but relatively little variability occurred among locations. Low variability among locations and a high degree of variability within locations would result if the primary source of inoculum was airborne ascospores, which would be dispersed uniformly within the field. This finding was confirmed by gametic disequilibrium analysis and suggests that the sexual reproduction of M. graminicola occurs in Saskatchewan.     

Benthic meiofauna as indicator of ecological changes in estuarine ecosystems: The use of nematodes in ecological quality assessment

Estuarine meiofauna communities have been only recently considered to be good indicators of ecological quality, exhibiting several advantages over macrofauna, such as their small size, high abundance, rapid generation times and absence of a planktonic phase. In estuaries we must account not only for a great natural variability along the estuarine gradient (e.g. sediment type and dynamics, oxygen availability, temperature and flow speed) but also for the existence of anthropogenic pressures (e.g. high local population density, presence of harbors and dredging activities).Spatial and temporal biodiversity patterns of meiofauna and free-living marine nematodes were studied in the Mondego estuary (Portugal). Both taxonomic and functional approaches were applied to nematode communities in order to describe the community structure and to relate it with the environmental parameters along the estuary. At all sampling events, nematode assemblages reflected the estuarine gradient, and salinity and grain size composition were confirmed to be the main abiotic factors controlling the distribution of the assemblages.Moreover, the low temporal variability may indicate that natural variability is superimposed by the anthropogenic pressures present in some areas of the estuary. The characterization of both meiofauna and nematode assemblages highlighted the usefulness of the integration of both taxonomic and functional attributes, which must be taken into consideration when assessing the ecological status of estuaries.     

Fish assemblages associated with urban structures and natural reefs in Sydney,Australia

Abstract Fish ecology in urban estuaries is poorly understood. As coastal landscapes are transformed, recognizing the impact that urban structures, such as marinas, seawalls and wharfs, have on local fish populations is becoming increasingly important. The extent to which fish are able to maintain natural ecological assemblages can be measured, to a certain extent, by how closely they mimic natural habitats. In Sydney Harbour, assemblages of fish associated with artificial structures were compared with those associated with natural rocky reefs. Sampling was carried out in five locations, each with a marina, swimming enclosure and natural reef. In each location, different habitats supported different assemblages, but differences between habitats were not consistent among locations. Subsequent sampling compared artificial and natural sites in three different areas in each of three different estuaries. Results indicated that differences in fish assemblages between artificial and natural sites were greater than differences between sites within each habitat, but there were no patterns among different positions in an estuary or from estuary to estuary. This study provides initial evidence that, although artificial habitats generally support the same species as found on natural reefs, assemblages usually differed between natural and artificial habitats. In addition, without knowing if these habitats do, in fact, sustain viable populations of fish, it would be premature to label artificial structures as effective habitat for fish.     

Importance of experimental design in detecting and measuring stresses in marine populations

Environmental sampling to detect and measure the sizesof stresses is made extremely difficult by naturalspatial and temporal variations in most possibleecological measurements. Sound application ofprinciples of experimental design is therefore acrucial component of any study. Temporal replicationbefore and after a disturbance is necessary to ensurethat accurate estimates are made of averageconditions. Otherwise, sampling will only reveal whathappens at the particular time sampled. Spatialreplication of reference or control locations isessential to prevent confounding any interpretation ofa difference between a disturbed and a controllocation. Unless locations are replicated, anydifference may be a stress or may be caused by anyother processes causing a difference. If there is nodifference, this does not mean there is no stress. Environmental stresses are manifested as statisticalinteractions due to changes in time being different indisturbed as opposed to control locations (or,equally, spatial differences between the disturbed andcontrol locations being different before and after thedisturbance). Features of experimental design thatallow the most reliable interpretation of suchinteractions should be the focus of planning ofstudies. Here, an ideal design is considered, withdiscussion of what is lost when (as often happens),idealism cannot be maintained. The discussionidentifies that sound planning, good design andadherence to precautionary principles all require thatunambiguous hypotheses are identified in advance ofsampling. In contrast to other approaches to analysisof stress, this approach has an explicit logicalstructure, assists to prevent confounding ininterpretations, identifies the sizes of stress thatwould elicit different responses from decision-makersand allows advance calculation of power to detect theanticipated stress for any chosen size of sampling. As a result, it is clear that more emphasis is neededon advance categorization of the types, directionsand, above all, magnitudes of stress that might matterin any particular case. Explicit statements about thesize of a possible stress will allow better planning,clearer guidance for development of programmes ofsampling and their interpretation and would reduce theuncertainty that categorizes much of environmentalanalysis.     

A practical protocol to assess impacts of unplanned disturbance: a case study in Tuggerah Lakes Estuary,NSW

Summary Environmental managers are often confronted with unplanned or accidental disturbances that may lead to environmental impacts. Procedures for detecting or measuring the size of such impacts are complicated because of the lack of data available before the disturbance and because of the intrinsic variability of most natural measures. Here, a protocol for detecting impacts is illustrated for single‐measure variables (numbers of individual species) and multivariate measures (relative abundances of invertebrates in assemblages). The present paper describes a case concerning drainage of acidified water into an estuary due to construction of a drainage channel in an area of wetland for which there had been no prior investigations (i.e. no ‘before’ data). The spatial extent of any impact was also unknowable. Sampling was, therefore, designed to allow for impacts of only a few tens of metres (using control sites 50 m from the mouth of the channel) and impacts covering much larger areas (500 m and 1 km from the mouth of the channel). Invertebrates in the mud around the channel and in control sites were sampled in replicated cores and the amount of seagrass in each core was weighed. Average abundances of invertebrate animals and weights of seagrass were compared, as was variation among samples in potentially impacted and control sites (using univariate analyses of variance). Sets of species were compared using multivariate methods to test the hypothesis that there was an impact at one of the scales examined. In fact, there was no evidence for any sort of impact on the fauna or seagrasses; the disturbance was a short‐term pulse without any obvious or sustained ecological response. One consequence of the study was that the local council was able to demonstrate no impact requiring remediation and no penalties were imposed for the unapproved construction of the channel. The implications of this type of study after an environmental disturbance are discussed. The present study identifies the need for clear definition of relevant hypotheses, coupled with rigorous planning of sampling and analyses, so that reliable answers are available to regulators and managers.     

Power, precaution, Type II error and sampling design in assessment of environmental impacts

Increasingly, environmental managers attempt to incorporate precautionary principles into decision making. In any quantitative analysis of impacts, precaution is closely related to the power of the analysis to detect an impact. Designs of sampling to detect impacts are, however, complex because of natural spatial and temporal variability and the intrinsic nature of the statistical interactions which define impacts. Here, pulse and press responses and impacts that affect time courses (temporal variance) were modelled to determine the influences of increasing temporal replication—sampling more times in each of several longer periods before and again after an impact.Increasing the number of control or reference locations and number of replicate sample units at each time and place of sampling investigated the influence of spatial replication on power. From numerous scenarios of impacts, with or without natural spatial and temporal interactions (i.e. not caused by an impact), general recommendations are possible. Detecting press impacts requires maximal numbers of control locations. Shorter-term pulse impacts are best detected when the number of periods sampled is maximized. Impacts causing changes in temporal variance are most likely to be detected by sampling with the greatest possible number of periods or times within periods.To allow precautionary decision making, the type of predicted impact should be specified with its magnitude and duration. Only then can sampling be designed to be powerful, thereby allowing precautionary concepts to be invoked.     

Vegetation patterns in heterogeneous landscapes: The importance of history and environment

Abstract. Throughout the eastern United States, plant species distributions and community patterns have developed in response to heterogeneous environmental conditions and a wide range of historical factors, including complex histories of natural and anthropogenic disturbance. Despite increased recognition of the importance of disturbance in determining forest composition and structure, few studies have assessed the relative influence of current environment and historical factors on modern vegetation, in part because detailed knowledge of prior disturbance is often lacking. In the present study, we investigate modern and historical factors that control vegetation patterns at Harvard Forest in central Massachusetts, USA. Similar to the forested uplands throughout the northeastern United States, the site is physiographically heterogeneous and has a long and complex history of natural and anthropogenic disturbance. However, data on forest composition and disturbance history collected over the past > 90 years allow us to evaluate the importance of historical factors rigorously, which is rarely possible on other sites. Soil analyses and historical sources document four categories of historical land use on areas that are all forested today: cultivated fields, improved pastures/mowings, unimproved pastures, and continuously forested woodlots. Ordination and logistic regressions indicate that although species have responded individualistically to a wide range of environmental and disturbance factors, many species are influenced by three factors: soil drainage, land use history, and C:N ratios. Few species vary in accordance with ionic gradients, damage from the 1938 hurricane, or a 1957 fire. Contrary to our expectation that the effects of disturbance will diminish over time, historical land use predicts 1992 vegetation composition better than 1937 composition, perhaps because historical woodlots have become increasingly differentiated from post-agricultural stands through the 20th century. Interpretations of modern vegetation must consider the importance of historical factors in addition to current environmental conditions. However, because disturbances such as land use practices and wind damage are complex, it is often difficult to detect disturbance effects using multivariate approaches, even when the broad history of disturbance is known.     

Temporal variability in the diversity and composition of stream bacterioplankton communities

Bacterioplankton in freshwater streams play a critical role in stream nutrient cycling. Despite their ecological importance, the temporal variability in the structure of stream bacterioplankton communities remains understudied. We investigated the composition and temporal variability of stream bacterial communities and the influence of physicochemical parameters on these communities. We used barcoded pyrosequencing to survey bacterial communities in 107 streamwater samples collected from four locations in the Colorado Rocky Mountains from September 2008 to November 2009. The four sampled locations harboured distinct communities yet, at each sampling location, there was pronounced temporal variability in both community composition and alpha diversity levels. These temporal shifts in bacterioplankton community structure were not seasonal; rather, their diversity and composition appeared to be driven by intermittent changes in various streamwater biogeochemical conditions. Bacterial communities varied independently of time, as indicated by the observation that communities in samples collected close together in time were no more similar than those collected months apart. The temporal turnover in community composition was higher than observed in most previously studied microbial, plant or animal communities, highlighting the importance of stochastic processes and disturbance events in structuring these communities over time. Detailed temporal sampling is important if the objective is to monitor microbial community dynamics in pulsed ecosystems like streams.     

Modern diatom assemblages in Central Mexico: the role of water chemistry and other environmental factors as indicated by TWINSPAN and DECORANA

SUMMARY. 1. Modern diatom samples, for which physical and chemical environmental conditions were recorded, were collected from forty-seven sites across Central Mexico
2. The results of the diatom counts were analysed using the clustering program TWINSPAN and the ordination program DECORANA.
3. Results from 'Laguna Zacapu and associated sites' showed that where water chemistry varies little between sample sites the effects of habitat are emphasized. This data set highlighted the problems of looking for modern analogues where anthropogenic disturbance is great.
4. TWINSPAN results from the 'Other Sites' data set suggested possible changes in diatom assemblages with chemical composition. The DECORANA analyses, however, again seemed to emphasize habitat.
5. In the context of this study, bottom sediment samples appeared to provide the most useful picture of 'average' conditions and to be the best source of analogues for the interpretation of fossil assemblages.     

Emulating Natural Disturbances for Declining Late-Successional Species: A Case Study of the Consequences for Cerulean Warblers (Setophaga cerulea)

Forest cover in the eastern United States has increased over the past century and while some late-successional species have benefited from this process as expected, others have experienced population declines. These declines may be in part related to contemporary reductions in small-scale forest interior disturbances such as fire, windthrow, and treefalls. To mitigate the negative impacts of disturbance alteration and suppression on some late-successional species, strategies that emulate natural disturbance regimes are often advocated, but large-scale evaluations of these practices are rare. Here, we assessed the consequences of experimental disturbance (using partial timber harvest) on a severely declining late-successional species, the cerulean warbler (Setophaga cerulea), across the core of its breeding range in the Appalachian Mountains. We measured numerical (density), physiological (body condition), and demographic (age structure and reproduction) responses to three levels of disturbance and explored the potential impacts of disturbance on source-sink dynamics. Breeding densities of warblers increased one to four years after all canopy disturbances (vs. controls) and males occupying territories on treatment plots were in better condition than those on control plots. However, these beneficial effects of disturbance did not correspond to improvements in reproduction; nest success was lower on all treatment plots than on control plots in the southern region and marginally lower on light disturbance plots in the northern region. Our data suggest that only habitats in the southern region acted as sources, and interior disturbances in this region have the potential to create ecological traps at a local scale, but sources when viewed at broader scales. Thus, cerulean warblers would likely benefit from management that strikes a landscape-level balance between emulating natural disturbances in order to attract individuals into areas where current structure is inappropriate, and limiting anthropogenic disturbance in forests that already possess appropriate structural attributes in order to maintain maximum productivity.     

Scavenging Rate Ecoassay: A Potential Indicator of Estuary Condition

Monitoring of estuary condition is essential due to the highly productive and often intensely impacted nature of these ecosystems. Assessment of the physico-chemical condition of estuaries is expensive and difficult due to naturally fluctuating water quality and biota. Assessing the vigour of ecosystem processes is an alternative method with potential to overcome much of the variability associated with physico-chemical measures. Indicators of estuary condition should have small spatial and temporal variability, have a predictable response to perturbation and be ecologically relevant. Here, we present tests of the first criterion, the spatio-temporal variability of a potential ecoassay measuring the rate of scavenging in estuaries. We hypothesised that the proposed scavenging ecoassay would not vary significantly among A) sites in an estuary, B) trips separated by weeks, or C) days in a trip. Because not all habitats are present in all estuaries, this test was undertaken in two habitats. When conducted over bare substrate there were occasional significant differences, but no discernible patterns, within levels of the experiment. When conducted over vegetated substrate, days within a trip did not vary significantly, but later trips experienced greater scavenging. This scavenging ecoassay shows potential as a tool for assessing the condition of estuarine ecosystems, and further exploration of this protocol is warranted by implementation in estuaries across a gradient of anthropogenic stress.     

Integrated assessment of heavy metal contamination in sediments from a coastal industrial basin, NE China

The purpose of this study is to investigate the current status of metal pollution of the sediments from urban-stream, estuary and Jinzhou Bay of the coastal industrial city, NE China. Forty surface sediment samples from river, estuary and bay and one sediment core from Jinzhou bay were collected and analyzed for heavy metal concentrations of Cu, Zn, Pb, Cd, Ni and Mn. The data reveals that there was a remarkable change in the contents of heavy metals among the sampling sediments, and all the mean values of heavy metal concentration were higher than the national guideline values of marine sediment quality of China (GB 18668-2002). This is one of the most polluted of the world's impacted coastal systems. Both the correlation analyses and geostatistical analyses showed that Cu, Zn, Pb and Cd have a very similar spatial pattern and come from the industrial activities, and the concentration of Mn mainly caused by natural factors. The estuary is the most polluted area with extremely high potential ecological risk; however the contamination decreased with distance seaward of the river estuary. This study clearly highlights the urgent need to make great efforts to control the industrial emission and the exceptionally severe heavy metal pollution in the coastal area, and the immediate measures should be carried out to minimize the rate of contamination, and extent of future pollution problems.     

Macrozoobenthic community structure in two Portuguese estuaries: Relationship with organic enrichment and nutrient gradients

The aim of this work consists in the study of the structural and functional aspects of the macrozoobenthic communities and their relationships with the organic enrichment and nutrient gradients in water and sediment. The study was carried out in two coastal ecosystems under strong anthropogenic pressure: the Sado estuary and the Aveiro Lagoon. Samples were collected at four stations between October 1994 and April 1995. The results obtained allowed us to state that spatial variability, both horizontal and vertical, was higher than the temporal variability. This was due to local hydrodynamism, organic load and granulometric structure of the sediment. Comparing the community structure at the different stations, it was possible to observe the existence of disturbance cases not directly related to organic enrichment gradients. The interpretation of the functional role of the macrozoobenthic communities at the water-sediment interface was based on the trophodynamic group classification. This approach allowed us to state that the sensitivity of different groups to organic enrichment, confirming the role of burrower subsurface-deposit feeders as opportunists associated with organic enrichment and, on the other hand, the influence of certain trophodynamic groups in the nutrient transfer processes, particularly the association between tube-builder omnivores and burrower carnivore and nitrate content in interstitial water.     

Point pattern analysis under conditions of replicated sampling北大核心CSCD

Aims: The analysis of point patterns, which deals with data sets consisting of mapped locations of organisms in a study region, is especially important to plant ecological studies because the locations of plants can often be approximated as points. However, few studies used point pattern analysis with data collected by replicated sampling. a principle procedure of acquiring data in ecological research. Therefore, we explore the applicability of point pattern analysis under conditions of replicated sampling in this study. Methods: Three replicated 5 m × 5 m plots of homogenous communities were established on a site with eight years of restoration in Nei Mongol steppe. In each plot, the locations of individuals in Leymus chinensis and Stipa grandis populations were mapped. O-Ring function was used to describe the population patterns and species association between L. chinensis and S. grandis for each plot as well as the integrative data of the three replicates. Important findings: Population patterns and species associations differed among the three replicated plots. This illustrates that if point pattern analysis was applied to describe the population patterns and species associations only by using data from a single plot sampling, the results could be misleading. Whereas it would be more reliable to integrate the data of replicated plots in the point pattern analysis because in this way the resulting O-Ring function is a weighted average, where the weight is the number of points in the replicate i divided by the total number of points in all replicated plots.     

Attraction of Wild Coastal Fishes to an Atlantic Subtropical Cage Fish Farms, Gran Canaria, Canary Islands

We assessed the influence of two commercial fish farms on the local aggregation of coastal wild fishes through a 'post-impact' sampling design at Gran Canaria Island (Canary Islands). At each farm, we established two controls and one impact location and estimated fish abundance bimonthly by means of SCUBA diving. Results provide evidence of local aggregation in the associated fish assemblages around sea-cage fish farms. Dissimilarities between control and impact locations for both fish farms were due to differences on the abundance of a few species. However, we detected significant differences by means of some assemblages between controls in one fish farm, as a consequence of the removal and re-location of cages. Moreover, we also detected significant within location small-scale variability for several fish assemblages around both sea-cages farms. Otherwise, we did not observe any effect of sampling times.     

森林衰退与全球气候变化

工业革命以来的人类活动,改变着大气的化学组成,从而改变着全球的气候,气候变率影响着森林的生长,甚至能导致森林衰退,全球气候变化引起森林衰退的机近几年制可能有几种,全球变暖,降水模型的改变以及蒸散作用的提高,将给一些森林带来高温胁迫和水分胁迫,危害植物的生理过程,ＣＯ２的施肥作用及其与气温升高的协同效应,将促进植物的新陈代谢,加速树木的成熟和衰老,在全球气候变化条件下,植物种竞争和分异将加强,气候变     

A Hierarchical Model to Estimate Fish Abundance in Alpine Streams by using Removal Sampling Data from Multiple Locations

The author compares 12 hierarchical models in the aim of estimating the abundance of fish in alpine streams by using removal sampling data collected at multiple locations. The most expanded model accounts for (i) variability of the abundance among locations, (ii) variability of the catchability among locations, and (iii) residual variability of the catchability among fish. Eleven model reductions are considered depending which variability is included in the model. The more restrictive model considers none of the aforementioned variabilities. Computations of the latter model can be achieved by using the algorithm presented by Carle and Strub (Biometrics 1978, 34 , 621–630). Maximum a posteriori and interval estimates of the parameters as well as the Akaike and the Bayesian information criterions of model fit are computed by using samples simulated by a Markov chain Monte Carlo method. The models are compared by using a trout (Salmo trutta fario) parr (0+) removal sampling data set collected at three locations in the Pyrénées mountain range (Haute‐Garonne, France) in July 2006. Results suggest that, in this case study, variability of the catchability is not significant, either among fish or locations. Variability of the abundance among locations is significant. 95% interval estimates of the abundances at the three locations are [0.15, 0.24], [0.26, 0.36], and [0.45, 0.58] parrs per m². Such differences are likely the consequence of habitat variability.     

Intermediate Pond Sizes Contain the Highest Density,Richness, and Diversity of Pond-Breeding Amphibians

We present data on amphibian density, species richness, and diversity from a 7140-ha area consisting of 200 ponds in the Midwestern U.S. that represents most of the possible lentic aquatic breeding habitats common in this region. Our study includes all possible breeding sites with natural and anthropogenic disturbance processes that can be missing from studies where sampling intensity is low, sample area is small, or partial disturbance gradients are sampled. We tested whether pond area was a significant predictor of density, species richness, and diversity of amphibians and if values peaked at intermediate pond areas. We found that in all cases a quadratic model fit our data significantly better than a linear model. Because small ponds have a high probability of pond drying and large ponds have a high probability of fish colonization and accumulation of invertebrate predators, drying and predation may be two mechanisms driving the peak of density and diversity towards intermediate values of pond size. We also found that not all intermediate sized ponds produced many larvae; in fact, some had low amphibian density, richness, and diversity. Further analyses of the subset of ponds represented in the peak of the area distribution showed that fish, hydroperiod, invertebrate density, and canopy are additional factors that drive density, richness and diversity of ponds up or down, when extremely small or large ponds are eliminated. Our results indicate that fishless ponds at intermediate sizes are more diverse, produce more larvae, and have greater potential to recruit juveniles into adult populations of most species sampled. Further, hylid and chorus frogs are found predictably more often in ephemeral ponds whereas bullfrogs, green frogs, and cricket frogs are found most often in permanent ponds with fish. Our data increase understanding of what factors structure and maintain amphibian diversity across large landscapes.