Effects of different management regimes on aquatic macroinvertebrate diversity in Australian rice fields

The maintenance of invertebrate diversity within agricultural environments can enhance a number of agronomically important processes, such as nutrient cycling and biological pest control. However, few Australian studies have been undertaken which specifically address the effects of commercial management regimes on rice field biodiversity. In this study, we compared aquatic macroinvertebrate communities within Australian rice fields cultivated under three commercial management regimes: conventional-aerial (agrochemicals applied, aerially sown), conventional-drill (agrochemicals applied, directly drill-sown) and organic-drill (agrochemical-free, directly drill-sown). These comparisons were undertaken using a combination of community assessment approaches, including morphospecies richness, abundance, diversity and community composition. In general, greater biodiversity existed within macroinvertebrate communities that developed under organic management regimes than under conventional regimes (i.e., higher morphospecies richness and Shannon diversity). Although there were significant differences in several parameters across management regimes early in the rice-growing season, as the growing season progressed the invertebrate communities that developed in the different management regimes became more similar. Only community composition analyses showed significant differences late in the growing season, with functional differences across aquatic faunal assemblages suggested by increased predator abundance in communities sampled from the organic management regime. In order to improve biodiversity within these aquatic environments, management techniques need to be examined individually and the most disruptive processes identified. Alternative management procedures can then be developed that minimise biodiversity loss whilst still delivering required agronomic outcomes.     

Accessing microbial diversity for bioremediation and environmental restoration

Biological methods for decontamination promise an improved substitute for ineffective and costly physico-chemical remediation methods, although so far only a fraction of the total microbial diversity (i.e. the culturable fraction with metabolic potential) has been harnessed for this purpose. Exploring and exploiting the "overlooked" genetic resource might ameliorate concerns associated with the degradation of recalcitrant and xenobiotic pollutants that are not degraded or only poorly degraded by known culturable bacteria. Recent advances in the molecular genetics of biodegradation and in knowledge-based methods of rational protein modification provide insight into the development of "designer biocatalysts" for environmental restoration. The application of such genetically engineered microorganisms (GEMs) in the environment has been limited, however, owing to the risks associated with uncontrolled growth and proliferation of the introduced biocatalyst and horizontal gene transfer. Programming rapid death of the biocatalyst soon after the depletion of the pollutant could minimize the risks in developing these technologies for successful bioremediation.     

Patterns in aquatic metacommunities are associated with environmental and trait heterogeneity

1. Metacommunities are structured by a combination of different ecological factors that vary in their importance depending on environmental heterogeneity and species functional equivalence. However, empirical tests of such context-dependence at regional scales are still missing.
2. We investigated associations between deterministic (e.g. environmental filtering and biotic interactions) and stochastic factors (e.g. dispersal related) and metacommunity structure of macroinvertebrates and diatoms across streams in four regions with contrasting levels of environmental and organismal trait heterogeneity.
3. Environmental filtering was most strongly associated with the region that showed moderate environmental heterogeneity and comprised communities with the highest trait heterogeneity. Associations with stochastic factors in the regions were more variable and difficult to predict. Environmental factors and the degree of genus-level association were generally more strongly associated with macroinvertebrates than with diatoms, whereas stochastic factors had consistently lower influence on macroinvertebrates.
4. These results suggest that the degree to which deterministic versus stochastic factors influence aquatic metacommunities depends on environmental and trait heterogeneity. Furthermore, organismal characteristics such as dispersal potential, habitat specialisation and sensitivity to environmental variation can also generate considerable context dependency in metacommunity structure.

     

Beta diversity of aquatic macroinvertebrate assemblages associated with leaf patches in neotropical montane streams

Over 70% of the total channel length in all river basins is formed by low order streams, many of which originate on mountaintops. Headwater streams play fundamental roles in processing and transporting terrestrial and aquatic organic matter, often harboring high biodiversity in bottom leaf patches deposited from riparian vegetation. The objective of this study was to assess the variation in taxonomic composition (measured by beta diversity of aquatic macroinvertebrates) among stream sites located in the Espinhaço Meridional Mountain Range, part of a UNESCO Biosphere Reserve in eastern Brazil. We tested two hypotheses. (a) Taxa turnover is the main reason for differences in aquatic insect assemblages within stream sites; we predicted that turnover would be higher than nestedness in all stream sites. (b) Stream site altitude and catchment elevation range are the main explanatory variables for the differences in beta diversity; we predicted that local stream site variables would account for only minor amounts of variation. In both dry and wet seasons, we sampled twice in two habitat types (five leaf patches in pools and five in riffles) in each of nine stream sites distributed in three different river basins. We computed average pairwise beta diversity among sampling stations and seasons in each stream site by using Jaccard and Bray–Curtis indices, and calculated the percentages of diversity resulting from turnover and nestedness. Finally, we tested the degree that local‐ or catchment‐level predictor variables explained beta diversity. We found that turnover was the main component of beta diversity and that both dissolved oxygen and elevation range best explained Bray–Curtis beta diversity. These results reinforce the importance of leaf patches in montane (sky islands) Neotropical savanna streams as biodiversity hotbeds for macroinvertebrates, and that both local and landscape variables explained beta diversity.     

Fish diversity in tidepools: assembling effects of environmental heterogeneity

Tidepools are considered ecosystems of high interchangeable fish biota. However, natural and anthropogenic actions that alter negatively marine ecosystems functioning (e.g., algal exploitation) are causing homogenization of fish biodiversity. Here, we describe the functional and taxonomic assembling of fishes in beach rocks of northeastern Brazil. Traits of fish species were retrieved from Fishbase and beta diversity was assessed by the dispersion of abundance, presence-absence and functional diversity in the multivariate space. We explained spatial-temporal variation in: alpha diversity, taxonomic and functional community composition; as well as temporal variation in functional, beta and gamma diversities. We found an annual stability in fish diversity and composition, and that fish biota was assembled mainly per tidepools’ depths. Substrate heterogeneity was correlated to depth, highlighting the role of local features as filters to organize the fish fauna vertically in tidepools, especially a cultivation of algae that influences the local assembling. We also highlight the uniqueness status of beach rocks in the Brazilian tropical region.     

Success criteria and adaptive management for a large-scale wetland restoration project

We are using a 20+ year photographic history of relatively undisturbed and formerly diked sites to predict the restoration trajectories and equilibrium size of a 4,050 ha salt marsh on Delaware Bay, New Jersey (USA). The project was initiated to offset the loss of finfishes from once-through cooling at a local power plant. We used a simple food chain model to estimate the required restoration size. This model assumed that annual macrophyte detritus production and benthic algal production resulted in production of finfishes, including certain species of local interest. Because the marsh surface and intertidal drainage system are used by many finfishes and are the focal points for exchange of detrital materials, the restoration planning focused on both vegetational and hydrogeomorphological parameters. Recolonization bySpartina spp. and other desirable taxa will be promoted by returning a natural hydroperiod and drainage configuration to two types of degraded salt marsh: diked salt hay (Spartina patens) farms and brackish marsh dominated byPhragmites australis. The criteria for success of the project address two questions: What is the “bound of expectation” for restoration success, and how long will it take to get there? Measurements to be made are macrophyte production, vegetation composition, benthic algal production, and drainage features including stream order, drainage density, channel length, bifurcation ratios and sinuosity. A method for combining these individual parameters into a single success index is also presented. Finally, we developed adaptive management thresholds and corrective measures to guide the restoration process.     

Success criteria and adaptive management for a large-scale wetland restoration project

We are using a 20+ year photographic history of relatively undisturbed and formerly diked sites to predict the restoration trajectories and equilibrium size of a 4,050 ha salt marsh on Delaware Bay, New Jersey (USA). The project was initiated to offset the loss of finfishes from once-through cooling at a local power plant. We used a simple food chain model to estimate the required restoration size. This model assumed that annual macrophyte detritus production and benthic algal production resulted in production of finfishes, including certain species of local interest. Because the marsh surface and intertidal drainage system are used by many finfishes and are the focal points for exchange of detrital materials, the restoration planning focused on both vegetational and hydrogeomorphological parameters. Recolonization bySpartina spp. and other desirable taxa will be promoted by returning a natural hydroperiod and drainage configuration to two types of degraded salt marsh: diked salt hay (Spartina patens) farms and brackish marsh dominated byPhragmites australis. The criteria for success of the project address two questions: What is the bound of expectation for restoration success, and how long will it take to get there? Measurements to be made are macrophyte production, vegetation composition, benthic algal production, and drainage features including stream order, drainage density, channel length, bifurcation ratios and sinuosity. A method for combining these individual parameters into a single success index is also presented. Finally, we developed adaptive management thresholds and corrective measures to guide the restoration process.Corresponding editor: R.E. Turner     

Plant species diversity and environmental heterogeneity: spatial scale and competing hypotheses

Questions: What is the observed relationship between plant species diversity and spatial environmental heterogeneity? Does the relationship scale predictably with sample plot size? What are the relative contributions to diversity patterns of variables linked to productivity or available energy compared to those corresponding to spatial heterogeneity? Methods: Observational and experimental studies that quantified relationships between plant species richness and within‐sample spatial environmental heterogeneity were reviewed. Effect size in experimental studies was quantified as the standardized mean difference between control (homogeneous) and heterogeneous treatments. For observational studies, effect sizes in individual studies were examined graphically across a gradient of plot size (focal scale). Relative contributions of variables representing spatial heterogeneity were compared to those representing available energy using a response ratio. Results: Forty‐one observational and 11 experimental studies quantified plant species diversity and spatial environmental heterogeneity. Observational studies reported positive species diversity‐spatial heterogeneity correlations at all points across a plot size gradient from ～1.0 × 10^?1 to ～1.0 × 10¹¹ m², although many studies reported spatial heterogeneity variables with no significant relationships to species diversity. The cross‐study effect size in experimental studies was not significantly different from zero. Available energy variables explained consistently more of the variance in species richness than spatial heterogeneity variables, especially at the smallest and largest plot sizes. Main conclusions: Species diversity was not related to spatial heterogeneity in a way predictable by plot size. Positive heterogeneity‐diversity relationships were common, confirming the importance of niche differentiation in species diversity patterns, but future studies examining a range of spatial scales in the same system are required to determine the role of dispersal and available energy in these patterns.     

Scales of spatiotemporal variability in macroinvertebrate abundance and diversity in monsoonal streams: detecting environmental change

1. We quantified spatial and temporal variability in benthic macroinvertebrate species richness, diversity and abundance in six unpolluted streams in monsoonal Hong Kong at different scales using a nested sampling design. The spatial scales were regions, stream sites and stream sections within sites; temporal scales were years (1997–99), seasons (dry versus wet seasons) and days within seasons. 2. Spatiotemporal variability in total abundance and species richness was greater during the wet season, especially at small scales, and tended to obscure site‐ and region‐scale differences, which were more conspicuous during the dry season. Total abundance and richness were greater in the dry season, reflecting the effects of spate‐induced disturbance during the wet season. Species diversity showed little variation at the seasonal scale, but variability at the site scale was apparent during both seasons. 3. Despite marked variations in monsoonal rainfall, inter‐year differences in macroinvertebrate richness and abundance at the site scale during the wet season were minor. Inter‐year differences were only evident during the dry season when streams were at base flow and biotic interactions may structure assemblages. 4. Small‐scale patchiness within riffles was the dominant spatial scale of variation in macroinvertebrate richness, total abundance and densities of common species, although site or region was important for some species. The proportion of total variance contributed by small‐scale spatial variability increased during the dry season, whereas temporal variability associated with days was greater during the wet season. 5. The observed patterns of spatiotemporal variation have implications for detection of environmental change or biomonitoring using macroinvertebrate indicators in streams in monsoonal regions. Sampling should be confined to the dry season or, in cases where more resources are available, make use of data from both dry and wet seasons. Sampling in more than one dry season is required to avoid the potentially confounding effects of inter‐year variation, although variability at that scale was relatively small.     

Application of clustering techniques for the characterization of macroinvertebrate communities to support river restoration management

The European Water Framework Directive prescribes that the development of a river assessment system should be based on an ecological typology taking the biological reference conditions of each river type as a starting point. Aside from this assessment, water managers responsible for river restoration actions also need to know the steering environmental factors to meet these reference conditions for biological communities in each ecological river type. As such, an ecological typology based on biological communities is a necessity for efficient river management. In this study, different clustering techniques including the Sørensen similarity ratio, ordination analysis and self-organizing maps were applied to come to an ecological classification of a river. For this purpose, a series of sites within the Zwalm river basin (Flanders, Belgium) were monitored. These river sites were then characterized in terms of biotic (macroinvertebrates), physical–chemical and habitat variables. The cluster analysis resulted in a series of characteristic biotic communities that are found under certain environmental conditions, natural as well as human-influenced. The use of multiple clustering techniques can be of advantage to draw more straightforward and robust conclusions with regard to the ecological classification of river sites. The application of the clustering techniques on the Zwalm river basin, allowed for distinguishing five mutually isolated clusters, characterized by their natural typology and their pollution status. On the basis of this study, one may conclude that river management could benefit from the use of clustering methods for the interpretation of large quantities of data. Furthermore, the clustering results might enable the development of a cenotypology useful for efficiently steering river restoration and enabling river managers to meet a good ecological status in most of the rivers as set by the European Water Framework Directive.     

Predicting the constraint effect of environmental characteristics on macroinvertebrate density and diversity using quantile regression mixed model

Various factors, such as habitat availability, competition for space, predation, temperature, nutrient supplies, presence of waterfalls, flow variability and water quality, control the abundance, distribution and productivity of stream-dwelling organisms. Each of these factors can influence the response of the density of organisms to a specific environmental gradient, inflating variability and making difficult to understand the possible causal relationship. In our study, we used quantile regression mixed models and Akaike’s information criterion as an indicator of goodness to examine two different datasets, one belonging to Italy and one belonging to Finland, and to detect the limiting action of selected environmental variables. In the Italian dataset, we studied the relationships among five macroinvertebrate families and three physical habitat characteristics (water velocity, depth and substratum size); in the Finnish dataset the relationships between taxa richness and 16 environmental characteristics (chemical and physical). We found limiting relationships in both datasets and validated all of them on different datasets. These relationships are quantitative and can be used to predict the range of macroinvertebrate densities or taxa richness as a function of environmental characteristics. They can be a tool for management purposes, providing the basis for habitat-based models and for the development of ecological indices.     

When humans work like beavers: riparian restoration enhances invertebrate gamma diversity and habitat heterogeneity

Restoration has the potential to increase habitat heterogeneity through the creation of unique habitat patches that, in turn, increase regional species richness or gamma diversity. While biological diversity and habitat heterogeneity are important factors to consider under a shifting climate, restoration actions and outcomes rarely examine these components. In this study, we examined the effects of riparian beaver dam analog (BDA) restoration on aquatic invertebrate diversity and habitat heterogeneity. Although the effects of BDAs on hydrology, geomorphology, and salmonid habitat have been explored, we are unaware of any studies assessing their effects on aquatic invertebrate diversity and the food web that supports them. We sampled aquatic invertebrates, basal carbon resources, dissolved nutrients, turbidity, and water temperature in pre- and post-BDA pond, side channel, and mainstem habitat over a three-year period. The BDAs functioned similarly to natural beaver dams and created slow-water environments that accumulated fine particulate organic material and increased pelagic phytoplankton production. Nonmetric multidimensional scaling, permutation multivariate analysis of variance, and Mantel's tests demonstrated that these changes led to the formation of a unique invertebrate community populated by lentic macroinvertebrates and zooplankton, which increased beta-diversity and gamma diversity. Further, BDAs in our study maintained high densities of invertebrates and buffered water temperatures in comparison to adjacent lotic habitats. These results support our hypothesis that BDAs can enhance invertebrate beta and gamma diversity through the creation and colonization of unique pond habitat and improve habitat and resource heterogeneity for native fishes under variable climate conditions.     

Floral variation and environmental heterogeneity in a tristylous clonal aquatic of the Pantanal wetlands of Brazil

MethodsStyle morph frequencies were sampled from 73 populations distributed across four flooding regimes differing in depth and duration. Measurements of flower size, sex-organ dimension, pollen size and pollen production were made in selected populations, and pollinator assemblages and their functional traits were recorded.ConclusionsThe similar morph structure and evenness of populations, regardless of flooding regime, suggest that sexual reproduction and clonal dispersal are sufficiently common to prevent the signature of founder events from dominating in a region. However, the pervasive occurrence of biased morph ratios in most populations suggests that many are in a non-equilibrium state. The reduced frequency of the mid-styled morph in trimorphic and dimorphic populations may be associated with the weak self-incompatibility of this morph resulting in selfing and inbreeding depression. Clonality in E. azurea and the weak self-incompatibility of the mid-styled morph may make it more vulnerable to geitonogamous selfing.     

Geographic patterns and environmental correlates of taxonomic and phylogenetic diversity of aquatic plants in China

Studies on large-scale geographic patterns of aquatic plant diversity can promote research on the generality of macroecological patterns in different ecosystems. Here, we compiled a checklist of 889 aquatic angiosperms in China, including 738 helophytes (emergent and marshy plants) and 151 hydrophytes (submerged, free-floating, and floating-leaved plants). We explore the geographic patterns and environmental correlates of aquatic plant diversity based on six metrics including species richness (SR), weighted endemism (WE), phylogenetic diversity (PD), phylogenetic endemism (PE), the standardized effect size of phylogenetic diversity (PDses), and the standardized effect size of mean phylogenetic distance (MPDses). Our results show that the diversity of aquatic plants in China is extremely uneven, with high diversity in southeastern China and low diversity in northwestern China, and the geographic patterns of taxonomic and PD are generally consistent. The pattern of helophytes differs from that of hydrophytes. Notably, the wavy-shaped pattern of aquatic plant diversity (especially SR and PD for hydrophytes) across the latitude observed in this study is not consistent with those previously observed for aquatic plants in other continents. Climatic variables and water environmental variables are the main drivers of aquatic plant diversity in China; however, the effects of individual variables differ between helophytes and hydrophytes. Water environmental variables have a greater impact on PDses and MPDses of hydrophytes than those of helophytes. Overall, our work provides insight into understanding the large-scale patterns of aquatic plant diversity and is a critical addition to previous studies on the macroecological pattern of terrestrial organisms.     

河流微生境异质性与大型底栖动物空间分布的关系

大型底栖动物是河流生态系统较好的指示类群,越来越广泛地应用于河流生态状况评价.识别大型底栖动物空间分布的影响因素可以分为宏观尺度因子、中观尺度因子和微观尺度因子.前人的研究较多集中于中观尺度.本研究基于10 m河段微生境因子与大型底栖动物调查,采用地统计学方法,在微观尺度上分析了大型底栖动物空间分布特征及其与微生境的关系.结果表明:不同生境类型中底栖动物指标存在差异性,激流、深潭和急流的Shannon指数平均值分别为2、1.9、1.78;大型底栖动物密度、生物量、丰富度指数及Shannon指数具有空间自相关性,存在一定的扩散效应;微生境因子与大型底栖动物指标及物种的空间关系存在差异性,其中,水深和流速与大型底栖动物关系的拟合度较弱,底质组成与大型底栖动物的拟合关系相对较好,底栖动物密度与粒径<4 mm底质体积百分比呈现正空间自相关,生物量、丰富度指数、Shannon指数与粒径>32 mm底质体积百分比呈现正空间自相关.本研究结果可为底栖动物扩散机制研究、调查样方设置、物理生境修复等提供参考.     

Relationships between spatial environmental heterogeneity and plant species diversity on a limestone pavement

No empirical studies have examined the relationship between diversity and spatial heterogeneity across unimodal species richness gradients. We determined the relationships between diversity and environmental factors for 144 0.18 m² plots in a limestone pavement alvar in southern Ontario, Canada, including within-plot spatial heterogeneity in soil depth, microtopography and microsite composition. Species richness was unimodally related to mean soil depth and relative elevation. Microsite heterogeneity and soil depth heterogeneity were positively correlated with species richness, and the richness peaks of the unimodal gradients correspond to the maximally spatially heterogeneous plots. The best predictive models of species richness and evenness, however, showed that other factors, such as ramet density and flooding, are the major determinants of diversity in this system. The findings that soil depth heterogeneity had effects on diversity when the effects of mean soil depth were factored out, and that unimodal richness peaks were associated with high spatial heterogeneity in environmental factors represent significant contributions to our understanding of how spatial heterogeneity might contribute to diversity maintenance in plant communities.     

Local heterogeneity of coral reef diversity and environmental stress provides opportunities for small-scale conservation

Aim

Strong social-ecological trade-offs between resource extraction and protection have created challenges for large, protected area management in natural resource-dependent countries. Therefore, local governments and community conservation activities are becoming common and information about low environmental exposure and high biodiversity can provide for planning localized conservation activities.

Location

The western Indian Ocean.

Methods

Coral reef sites were evaluated for local-scale environmental and species richness to elucidate local patterns in spatial heterogeneity. Local coral and fish taxonomic richness and coral community susceptibility to stress were normalized to partially account for common and heterogenous disturbances to coral cover and fish biomass. Residuals of these three response variables were evaluated for local geographic patterns and specific relationships with 21 environmental variables using machine learning methods.

Results

Richness was highly variable at local geographies and had a double-peaked shape with latitudes. Thirteen of the 21 examined variables were selected and indicated complex, spatially heterogeneous and weak cumulative predictive relationships with specific environmental and human influences. For example, each selected variable contributed 7% to 25% of the variance but with different relationships for the three responses. Coral fish richness and coral community susceptibility correlations were positive but weak and therefore produced different local spatial patterns. Nevertheless, these spatial patterns exhibited some coarse-scale similarities indicating locations with shared positive community attributes and potential climate refugia. Shared richness variables included depth and wave energy, temperature variables of SST skewness, excess heat and rate of rise. Human influences of distance to shore, human populations and cities were also selected for richness and community susceptibility responses.

Main Conclusions

Planning to include local stress and richness patterns variability could contribute to species persistence. From these specific data, sites in the Pemba Channel between the Tanzanian mainland and Pemba Island, and northern Mozambique and Madagascar fit refugia characteristics.     

Aquatic macroinvertebrate richness and diversity associated with native submerged aquatic vegetation plantings increases in longer-managed and wetland-channeled effluent constructed urban wetlands

Macroinvertebrate community structure and assemblages associated with the planted, native submerged aquatic vegetation (SAV) species Heteranthera dubia (Jacq.) MacMillan and Potamogeton nodosus Poiret were examined in a series of constructed urban floodway wetlands, the Dallas Floodway Extension Lower Chain of Wetlands, Dallas, TX, USA. Macroinvertebrate community metrics, including abundance, richness, diversity, and evenness associated with SAV and three different wetlands of varying construction completion dates, water sources (direct or wetland-channeled wastewater effluent), and ecosystem management stage (established/reference or developing) were compared and analyzed. Assemblages at sampling sites were also classified and related to vegetation and wetland physicochemical parameters. Plant species affected only macroinvertebrate abundance, with the less-dissected P. nodosus supporting higher counts than H. dubia. Wetland age and water-effluent type had the most substantial effect on macroinvertebrate communities. The older, longer-managed wetland and wetland-channeled effluent habitat consistently demonstrated higher quality metrics and biodiversity than newly constructed, direct effluent wetland habitat. Increased vegetation cover and wetland age, coupled with moderate water temperature, pH, and DO levels were characteristics of more rich and diverse macroinvertebrate communities, including pollutant-sensitive taxa, such as Ephemeroptera and Trichoptera.