Planktonic algae abundance and diversity are similar in urban stormwater ponds of different geographic locations and natural shallow lakes

Elevated levels of different contaminants are typical to stormwater management ponds. Despite that, a number of works report stormwater ponds serving as habitats for a variety of biota. In this study we aimed to examine phytoplankton communities of urban ponds, as the basis of the aquatic food web, and compare them to those of natural shallow lakes. Stormwater ponds were selected from two distant geographic locations: three in Denmark and three in Canada. As a reference to natural systems, three Danish shallow lakes were sampled. The sampling was carried out in the spring, summer and fall of 2014. The phytoplankton communities in ponds were found to be at least as rich in taxa as natural shallow lakes. Their abundance and biovolume varied highly among the types of water bodies as well as in each pond or lake individually, depending on the sampling month. We did not find any significant differences among ponds and natural shallow lakes at the investigated taxonomic level, despite some distinction observed by multivariate DCA and CCA analyses. Little difference was found between Canadian and Danish ponds as well, even though they are separated by a large geographic distance. This study shows that stormwater ponds are habitats for diverse planktonic algae communities which have some similarities to those of natural shallow lakes. Also, the similarities observed between Danish and Canadian ponds indicate some consistence with the urban homogenization hypothesis, although this should be further looked into by future works examining a larger number and distinct types of ponds.

     

Is there a relationship between socio-economic factors and biodiversity in urban ponds? A study in the city of Stockholm

Urban small water bodies, such as ponds, are essential elements of human socio-economic landscapes. Ponds also provide important habitats for species that would otherwise not survive in the urban environment. Knowledge on the biodiversity of urban ponds and the relationship between their ecological value and factors linked to urbanization and socio-economic status is crucial for decisions on where and how to establish and manage ponds in cities to deliver maximum biodiversity benefits. Our study investigates if the pattern of urban-pond biodiversity can be related to different socio-economic factors, such as level of wealth, education or percentage of buildings of different types. Because of lack of previous studies investigating that, our study is of exploratory character and many different variables are used. We found that the biodiversity of aquatic insects was significantly negatively associated with urbanisation variables such as amount of buildings and number of residents living around ponds. This relationship did not differ depending on the spatial scale of our investigation. In contrast, we did not find a significant relationship with variables representing socio-economic status, such as education level and wealth of people. This latter result suggests that the socio-economic status of residents does not lead to any particular effect in terms of the management and function of ponds that would affect biodiversity. However, there is a need for a finer-scale investigation of the different potential mechanism in which residents in areas with differing socio-economic status could indirectly influence ponds.     

Multiscale drivers of amphibian community occupancy in urban ponds

Urban Ecosystems - Urbanization has driven the loss of natural aquatic habitats while concurrently increasing the abundance of artificial urban ponds. Urban ponds are not typically designed for...     

A balancing act in urban social-ecology: human appreciation,ponds and dragonflies

Green spaces in cities provide cultural ecosystems services (CES) such as nature connection, wildlife interaction and aesthetic appreciation which can improve aspects of human well-being. Recognising these benefits, researchers are now examining the complex relationship between humans and nature in urban social-ecology. Most studies investigate people’s appreciation and valuation of different green space features and their contribution to urban biodiversity. Recommendations arising from such studies are best practices to achieve a balance between landscape aesthetic and ecological objectives, but many knowledge gaps still exist. In a social-ecological project in Greater London, appreciation of ponds and dragonflies in urban green spaces, and the environmental factors determining dragonfly diversity were investigated. We found ponds and their appearance were valued by people as enhancing their green space experience. The preference for wild-looking ponds was moderate. Dragonflies were enjoyed for their colour and high visibility, especially by those who had basic dragonfly knowledge. Species richness of dragonflies was positively associated with habitat heterogeneity in and around a pond. However, people were unable to relate a heterogeneous pond to more dragonfly species. For the first time, some factors that influence the human appreciation-ponds-dragonflies (HPD) relationship in an urban context are revealed. To fully realise the CES potential of ponds and dragonflies in Greater London, a HPD framework is proposed. The framework underpins strategies that foster cultural sustainability for ponds and dragonfly conservation.     

Nesting and foraging behavior of red-winged blackbirds in stormwater wetlands

Stormwater wetlands are a common part of urban and suburban landscapes. These constructed wetlands provide first-order treatment of effluent from roads, parking lots, lawns and other surfaces. They also provide habitat for wetland-associated birds. Thus, there is a concern that birds may be attracted to potentially toxic habitats. This study assesses nesting success and forging behavior of Red-winged Blackbirds (Agelaius phoeniceus) in retention stormwater wetlands based on drainage type. Drainage categories included residential, commercial, and highway sites. Commercial sites had the lowest nesting success and the lowest diversity of invertebrate foods. Mean nest success values for all three types of wetlands, especially for highway drainages, were comparable to published values from natural wetlands. Over two years of study highway ponds collectively served as source populations whereas residential and commercial sites were population sinks in one year and sources in the other. Red-wings using highway sites had the highest foraging efficiency as determined by the frequency and duration of forays. Residential sites had the greatest human disturbance and generally had intermediate-quality habitat and nesting success. We conclude that while stormwater wetlands collect run off and accompanying pollutants, they can still be valuable habitats for nesting birds in urban and suburban areas. We recommend a few management strategies that can increase avian use of these habitats.     

Ecological resilience in urban ecosystems: Linking urban patterns to human and ecological functions

Urban ecosystems evolve over time and space as the outcome of dynamic interactions between socio-economic and biophysical processes operating over multiple scales. The ecological resilience of urban ecosystems—the degree to which they tolerate alteration before reorganizing around a new set of structures and processes—is influenced by these interactions. In cities and urbanizing areas fragmentation of natural habitats, simplification and homogenization of species composition, disruption of hydrological systems, and alteration of energy flow and nutrient cycling reduce cross-scale resilience, leaving systems increasingly vulnerable to shifts in system control and structure. Because varied urban development patterns affect the amount and interspersion of built and natural land cover, as well as the human demands on ecosystems differently, we argue that alternative urban patterns (i.e., urban form, land use distribution, and connectivity) generate varied effects on ecosystem dynamics and their ecological resilience. We build on urban economics, landscape ecology, population dynamics, and complex system science to propose a conceptual model and a set of hypotheses that explicitly link urban pattern to human and ecosystem functions in urban ecosystems. Drawing on preliminary results from an empirical study of the relationships between urban pattern and bird and aquatic macroinvertebrate diversity in the Puget Sound region, we propose that resilience in urban ecosystems is a function of the patterns of human activities and natural habitats that control and are controlled by both socio-economic and biophysical processes operating at various scales. We discuss the implications of this conceptual model for urban planning and design.     

Habitat origins and microhabitat preferences of urban plant species

Urban vegetation is commonly described as dominated by weedy species that are adapted to human disturbance. In this study, we determined the original (pre-agriculture) habitats of urban plant species sampled quantitatively in the spontaneous vegetation of a university campus in Halifax, Nova Scotia (eastern Canada). We sampled 11 distinct patch types corresponding to different built forms. Differences in vegetation among patch types were related in part to environmental variables such as soil moisture and light availability. The urban vegetation was dominated by species from rocky habitats such as cliffs and talus slopes, with lesser representation from grassland and floodplain habitats. When compared to a null model of species origins based on the global area and species richness of different original habitats, species from rock outcrops and grassland habitats were overrepresented in the urban vegetation. These results contrast with the received view that cities represented highly “unnatural” ecosystems: built form appears to replicate the habitat templates required by rock outcrop species. Urban ecological theory should incorporate the replication of habitat analogs by built forms in addition to the creation of ecologically novel habitats.     

Butterfly diversity,habitat and vegetation usage in Hong Kong urban parks

The conservation value of urban parks for butterfly communities remains poorly understood, particularly for tropical butterflies in Asia. We conducted point count and route transect butterfly surveys, and used them to sample four habitats located within 13 urban parks across Hong Kong. We found 1054 individuals and 58 species of butterflies recorded in 60 survey hours over 6 months. This represents approximately one quarter of the entire known Hong Kong butterfly species list. Over 30 % of the individuals counted were Catospilia sp. but six of the species identified are classified locally as rare or very rare. Tree-covered habitats and grasslands showed higher butterfly diversity than open areas. The most common butterfly behavior was “directed flight,” which we also found to be habitat-dependent and most common in ponds and open areas. We additionally observed the use of vegetation in urban parks, which included 40 species of nectar plant and four records of butterfly oviposition. The high butterfly diversity, presence of rare species and usage of vegetation (especially as a nectar resource) we documented in this study suggests that urban parks have some conservation value for Hong Kong. However, the use of pesticides and heavy vegetation clearing may limit significant butterfly reproduction and population growth. Altogether these results emphasize the diversity of uses of urban parks for butterflies in Hong Kong while also providing possible directions for improvement in habitat and vegetation management that could increase urban park value for biodiversity.     

Rural land use bifurcation in the urban-rural gradient

The classic urban-rural gradient concept assumes a decline in land use intensity from an intensively developed urban core outward to residential suburbs, culminating in lightly developed rural areas. The concept provides a common framework directing urban socio-ecological research. Given that rural land use includes woodlands and croplands, and croplands appear as ecologically depauperate as urban lands, we investigated land-use patterns along urban-rural gradients for 30 large metropolitan areas in the eastern United States. We predicted a bifurcation at the rural end of the gradient between woodland and cropland land use that does not correspond with human population density (expected to be relatively low in rural areas regardless of land use type). Our data indicated that ‘rural’ was a poor substitute for ‘natural’ as the rural end of the gradients bifurcated at the rural end between woodland and cropland – croplands being demonstratively poor ecological habitats. Indeed, we found that when defined by habitat quality, the habitat known to be biotically homogenized (urban and cropland) remained steady along the urban-rural gradient. Our results do not undermine the utility of the urban-rural gradient framework, but do suggest that the gradient and/or human population density do not necessarily indicate shifts in habitat quality.     

Bird species assemblages across a rural urban gradient around Kolkata,India

Urban development leads to changes in habitat structure and resource base. Bird communities are known to respond sharply to such changes. Our result from study of bird community along urbanization gradient around Kolkata metropolitan city clearly separated the urban bird community from the rural and rural 3 habitats in terms of species diversity and foraging groups. Rural and rural 3 sites had more number of rare species and higher percentage of unique species as compared to the urban habitats. Functional group analysis showed higher abundance of granivores in urban habitats and absence of insectivore and carnivorous species that were found in the rural and rural 3 habitats. The bird species assemblage along the gradient was significantly nested where bird species recorded in urban areas were subset of the species rich rural areas. There was no difference in individual counts between urban and rural habitats, therefore nullifying the hypothesis that rural areas are more species rich because of higher population size. Bird community in the urban areas was less even as compared to the rural areas due to the dominance of omnivorous guild. Bird diversity was negatively correlated to the density of house lots.     

Use of urban habitats by coyotes in the vicinity of Banff Alberta

Little information is available on the degree to which coyotes (Canis latrans) use urban habitats. In the past, interactions between coyotes and humans have precipitated several instances of coyote aggression towards humans. Consequently, I analyzed use of urban habitats by coyotes and the possibilities for aggressive encounters with humans. In this study, 11 radio-collared coyotes were monitored between July 1991 and September 1992. Use/availability analysis demonstrated a clear difference in use of natural habitats between summer and winter. Urban habitats were used in direct proportion to availability during all time periods, except during the day in summer when coyotes avoided intense human activity. Campgrounds were not an attraction during either season. For the most part, coyotes in the vicinity of Banff used habitats available to them regardless of human activity. Evidence does not suggest the coyote population in the vicinity of Banff is predisposed to aggression due to familiarity with humans. The relationship between the data and coyote aggression towards humans is discussed.     

Urban ornamental trees: a source of current invaders; a case study from a European City

Human made habitats are considered to be important hotspots of biodiversity of native as well as alien plant species. Due to high propagule pressure caused by human activities they serve as a source of introduction of alien plant species. We used the database of planted ornamental trees and shrubs for Brno, Czech Republic, to determine the significance of introduction effort given by intensity of planting as a factor in woody plant naturalization. Of all planted woody taxa, 15% were recognized as spontaneously growing in the urban area and there was a significant relationship between the number of planted individuals and the ability of a species to spontaneously occur in the urban area. The most often spontaneously escaping species originated in Europe (55%), followed by neophytes from North America (21%) and Central and Eastern Asia (14%). Although only a minor portion of planted woody species is able to escape from cultivation, this still could represent a potential risk for the native vegetation.     

Assessing the diversity of the benthic oligochaete communities in urban and woodland ponds in an industrial landscape (Upper Silesia,southern Poland)

Studies were carried out in two mining pond complexes in an industrial landscape. The first complex (consisting of six ponds) was located in an urban area and the second one (consisting of six ponds) in a woodland area. The aims of the study were to assess the diversity of benthic oligochaetes and to evaluate which environmental variables are most important in determining variations in the community structure in ponds of varying location. In total, 21 oligochaete species were recorded (7–11 in the urban ponds, 11–15 in the woodland ponds). Aulodrilus pluriseta, Aulodrilus japonicus and Ophidonais serpentina were only found in the woodland ponds, while Potamothrix bavaricus only occurred in the urban ponds. Limnodrilus hoffmeisteri, Limnodrilus claparedeanus, Chaetogaster diaphanus and Ophidonais serpentina dominated in the woodland ponds, whereas Limnodrilus hoffmeisteri, Limnodrilus claparedeanus, Potamothrix bavaricus and Tubifex tubifex prevailed in the urban ponds. The total density of oligochaetes was higher in the urban ponds thought the values of the diversity indices were higher in the woodland ponds. The local diversity of the ponds was high, while the among-site diversity made only a small contribution to the regional diversity. Nonetheless, a cluster analysis divided all of the ponds into two distinct groups depending on their location. CCA analysis showed that conductivity, pH, total hardness, alkalinity, the concentration of chlorides and the content of organic matter in the bottom sediments were most associated with the distribution of some oligochaete species among the ponds studied.     

Amphibian use of constructed and remnant wetlands in an urban landscape

Urban areas are increasing in number, extent, and human population density worldwide. There is potential to mitigate negative impacts of urbanization to native pond-breeding amphibians by providing habitat in both remnant natural and constructed wetlands. This study examines amphibian use of potential breeding sites in natural and constructed ponds in a large metropolitan area to investigate habitat characteristics that are associated with successful breeding. I surveyed 62 ponds over three breeding seasons in Portland, Oregon, measuring eleven habitat characteristics that may influence their successful breeding: pond depth, nitrate level, aquatic refugia, aquatic vegetation, surrounding vegetation, pond permanence, presence of fish and of introduced bullfrogs, surrounding road density and forest cover, and whether they were constructed or remnant natural ponds. Five of the six native pond-breeding species that occur in the region were regularly found breeding in city ponds. Surrounding forest cover and amount of aquatic vegetation were highly associated with breeding, indicating that preserving and planting vegetation likely benefits urban amphibians. Non-native bullfrogs were not associated with native species richness. Surprisingly, whether a pond was natural or constructed was also only weakly associated with native species breeding, and the trend was towards higher presence for all species in constructed ponds. This indicates that novel, human-dominated areas can provide habitat for these species. Consideration of habitat characteristics associated with breeding success in urban pond management will likely benefit native amphibians in these rapidly expanding landscapes.     

Diversity patterns of alien and native plant species in Trieste port area: exploring the role of urban habitats in biodiversity conservation

Nowadays, urban areas play a crucial role in biodiversity conservation and habitat protection despite the constant pressures on which these habitats are subjected. They may even host relatively new plant communities due to the peculiar ecosystem where they vegetate. The port of Trieste (NE Italy) is characterized by a mixed mosaic of intensely human impacted areas (where commercial activities are still ongoing) flanked by abandoned areas where vegetation persists or has spontaneously recovered. In this study, we sampled the whole port area through a stratified random sampling by placing multiscalar nested plots in four different habitats (strata) previously identified by photo-interpretation. Plant species richness and abundance were assessed in each plot. Each species was then classified as native or alien and patterns of species richness and complementarity were compared among habitats. Results show that there is a significant difference in species richness patterns among habitats, while observed patterns are likely to vary at different spatial scales. As expected, urban plots account for most of the alien species in the sampling, while wooded plots cope better with invasion, accounting for a lower alien/native ratio. These results highlight how habitat diversity enhances biodiversity in urban areas and how it could provide an effective filtering effect able to reduce the spread of alien species. In addition, we provide further evidence for the use of multi-scale approaches in order to study the complex relationships between spatial heterogeneity and plant species richness.     

Ecosystem services provided by urban spontaneous vegetation

Spontaneous vegetation colonizes large areas in and around cities. These unmanaged areas are considered to have low economic value or indicate dereliction, but recent research suggests that these can contribute valuable ecosystem services. This study evaluates indicators of ecosystem services in three habitats: urban spontaneous vegetation (USV), managed lawns, and semi-natural urban forest, in Halifax, Nova Scotia. USV had higher indicator values for habitat provisioning (plant species diversity, invertebrate abundance and taxonomic diversity) than the other habitats. Indicators of climatic regulatory services (albedo and leaf area index) in USV were similar to those in lawn habitats. Organic carbon content of the soils, an indicator of carbon storage, was lowest in USV but only marginally lower than in lawns. Standing biomass, an indicator of production services, was lowest in USV but lawn production may have been overestimated. While USV sites are usually transitory components of the urban landscape, they deserve further consideration due to their provision of ecosystem services, in some cases to a greater extent than conventionally valued urban habitats.     

Patch or mosaic: bat activity responds to fine-scale urban heterogeneity in a medium-sized city in the United States

Many recent studies have suggested that cities are spatially heterogeneous. Only limited research has investigated whether urban heterogeneity influences the distribution of bats in a city. Between 2010 and 2012, we acoustically surveyed bats in Waco, Texas, a medium-sized city in the United States. Seven species were detected, five in adequate quantity for analyses. Three distinct distribution patterns were evident (Mexican free-tailed bats; red bats and evening bats; big brown bats and cave myotis), reflecting the distinct functional guilds of these species. Bayesian conditional autoregressive models indicated that tree-dwelling red bats and evening bats were influenced by variables describing heterogeneity of urban vegetation. Big brown bats and cave myotis were associated with variables related to water sources. Mexican free-tailed bat distribution could be explained well by variables related to urban buildings and other constructions. Our modeling also suggested that urban socioeconomic heterogeneity influenced bat distributions. Distributions of tree-dwelling bats corresponded to income level. Distributions of Mexican free-tailed bats, big brown bats, and cave myotis related to human density. These results support the idea that a city comprises a mosaic of habitats as perceived by various species of bats and likely by other species of wildlife in urban settings.     

Variability of water quality,metals and phytoplankton community structure in urban stormwater ponds along a vegetation gradient

Stormwater Ponds (SPs) are common throughout urbanizing environments, yet their ecological role has not been well established. SPs are primarily designed for hydrological control of stormwater, but many are also designed to attenuate the quality of runoff prior to discharge. Thus, SPs likely serve as an important land-water linkage between terrestrial and aquatic systems in urban areas. In this study, we characterized 22 SPs and 3 natural reference ponds from Durham Region, Ontario, Canada representing a gradient in emergent plant cover. There was high variability and wide ranges in water quality parameters among SPs. The percentage of impervious surface served as a measure of urbanization intensity, and was a significant driver of conductivity, chloride and total suspended solids regardless of emergent vegetation cover. In fact, only water temperature (r?=??0.61) was found to significantly correlate with vegetation cover. This suggests a minimal role for emergent vegetation in mediating SP water quality. SPs had notably higher conductivity and runoff-metals (Cu, Zn, Pb, and Cr) than reference ponds, but nutrients (Total P and Total N) and algal biomass did not significantly differ between SPs and reference ponds. Dominant phytoplankton groups included blue-green and euglenid algae, both of which are indicators of eutrophic and high organic systems, respectively. The blue-green genus Microcystis was detected in all ponds, and was the dominant taxon in most SPs. This raises concern that SPs may serve as reservoirs of toxin-producing algae. Multivariate analyses of metals, water quality variables and algal species composition showed considerable dissimilarity among SPs, yet comparably high similarity among reference ponds. This indicates that SPs are dynamic and diverse systems despite their engineered origins. Such broad gradients in water quality characteristics also imply variable impacts to receiving waters in the same region.     

Invasive <Emphasis Type="Italic">Wisteria</Emphasis> in the Southeastern United States: genetic diversity,hybridization and the role of urban centers

The increasing numbers and negative impacts of invasive species have prompted research on the relationship between human activities and the success of invasive horticultural plants. In this study, we use population genetic relationships to model the escape of a common garden vine, exotic Wisteria, into natural habitats. Urban and naturalized Wisteria populations in Charleston, South Carolina and Tallahassee, Florida were investigated using a combination of chloroplast, mitochondrial and nuclear DNA markers. Fifty-nine of 72 (81.9%) Wisteria collections were hybrids of Wisteria sinensis and W. floribunda. Chi-square analysis of the distribution of shared W. floribunda haplotypes among naturalized and urban populations supports the relationship of time with invasion success. Naturalized populations were more similar to those in historic neighborhoods. The most common haplotype, F1, was encountered 22 times but its distribution was not significantly different between urban and naturalized populations. In contrast, a significantly higher proportion of haplotype F2 found in naturalized populations suggests that selection may also be acting within these populations. Finally, due to extensive human dispersal, there is no relationship between genetic distance and geographical distance among the populations sampled. We conclude that Wisteria’s long history of horticulture, rampant hybridization, and human-aided dispersal are all implicated in the successful ability of these plants to invade natural habitats throughout the USA.     

Urban environments are associated with earlier clutches and faster nestling feather growth compared to natural habitats

Urbanization creates new habitats with novel benefits and challenges not found in natural systems. How a species fares in urban habitats is largely dependent on its life history, yet predicting the response of individual species to urbanization remains a challenge. While some species thrive in urban areas, others do poorly or are not present at all. Mountain chickadees (Poecile gambeli) are year-round residents of montane regions of western North America. Commonly found in higher-elevation coniferous forests, these birds can also be found in urban areas where they will regularly visit bird feeders and nest in nest boxes. We monitored mountain chickadees nesting along a habitat gradient, from natural habitat to suburban areas, to determine if the degree of urbanization was associated with: clutch size and success; nestling growth rates; or variation in parental size and age. Females nesting in urbanized areas initiated clutches earlier in the breeding season than those in natural areas, but neither fledging success nor the rate of nestling mass-change differed between habitats. Nestling feather growth-rate increased with later first egg dates in both habitats, and the magnitude of this increase was greatest in urban habitats. We found no difference in the proportion of first-time breeders versus experienced breeders between habitat types, nor any differences in male or female mass or size. Our results indicate no detriment to nesting in urban habitats, suggesting mountain chickadees are able to adapt to moderate urbanization much like other members of the Paridae family.