Water Body Size Research Articles

Thermal and hydrodynamic environments mediate individual and aggregative feeding of a functionally important omnivore in reef communities.

In eastern Canada, the destruction of kelp beds by dense aggregations (fronts) of the omnivorous green sea urchin, Strongylocentrotus droebachiensis, is a key determinant of the structure and dynamics of shallow reef communities. Recent studies suggest that hydrodynamic forces, but not sea temperature, determine the strength of urchin-kelp interactions, which deviates from the tenets of the metabolic theory of ecology (MTE). We tested the hypothesis that water temperature can predict short-term kelp bed destruction by S. droebachiensis in calm hydrodynamic environments. Specifically, we experimentally determined relationships among water temperature, body size, and individual feeding in the absence of waves, as well as among wave velocity, season, and aggregative feeding. We quantified variation in kelp-bed boundary dynamics, sea temperature, and wave height over three months at one subtidal site in Newfoundland to test the validity of thermal tipping ranges and regression equations derived from laboratory results. Consistent with the MTE, individual feeding during early summer (June-July) obeyed a non-linear, size- and temperature-dependent relationship: feeding in large urchins was consistently highest and positively correlated with temperature <12°C and dropped within and above the 12–15°C tipping range. This relationship was more apparent in large than small urchins. Observed and expected rates of kelp loss based on sea temperature and urchin density and size structure at the front were highly correlated and differed by one order of magnitude. The present study speaks to the importance of considering body size and natural variation in sea temperature in studies of urchin-kelp interactions. It provides the first compelling evidence that sea temperature, and not only hydrodynamic forces, can predict kelp bed destruction by urchin fronts in shallow reef communities. Studying urchin-seaweed-predator interactions within the conceptual foundations of the MTE holds high potential for improving capacity to predict and manage shifts in marine food web structure and productivity.

염수 대수층 내 담수 주입양 변화에 따른 주입정과 양수정 사이의 담수체 거동에 관한 수치적 연구

In this study, the behavior of fresh water body between the injection and production wells with the fresh water injection rate in a saline aquifer is numerically analyzed by using a three-dimensional numerical model. 8 injection wells are arranged at equidistant intervals on a concentric circle and one production well is located at the center of this circle. In the case that the fresh water injection rate is relatively small, the fresh water body around a injection well screen is not mixed with neighboring ones and is independently distributed. However, when the injection rate is increased, the size of the fresh water body is continuously increased, and the areas, where saline and fresh water among injection wells are mixed, are appeared. The mixed degree is increased as the injection rate is increased. This phenomenon is identically generated around the production well. Moreover, when the injection rate is increased, the ratio of saline water in and around the production well is decreased.

The Impact Analysis of Water Body Landscape Pattern on Urban Heat Island: A Case Study of Wuhan City

Based on the LST and the landscape metrics of water body with remote sensing technique and spatial analysis, the relationship between the mean LST and the attributes of water body was revealed via Pearson’s correlation analysis and multiple stepwise regression analysis. Result showed that, in 32 class-based metrics we selected, the proportion of water body, average water body size, the isolation and fragmentation of water body, and other eight metrics have high correlation with the LST. As a resultant force, the quantity, shape, and spatial distribution of water body affect the forming of temperature. We found that the quantity and spatial pattern of city water body could be allocated reasonably to maximize its cooling effect.

Analysis of the impact of spatial resolution on land/water classifications using high-resolution aerial imagery

Long-term monitoring efforts often use remote sensing to track trends in habitat or landscape conditions over time. To most appropriately compare observations over time, long-term monitoring efforts strive for consistency in methods. Thus, advances and changes in technology over time can present a challenge. For instance, modern camera technology has led to an increasing availability of very high-resolution imagery (i.e. submetre and metre) and a shift from analogue to digital photography. While numerous studies have shown that image resolution can impact the accuracy of classifications, most of these studies have focused on the impacts of comparing spatial resolution changes greater than 2 m. Thus, a knowledge gap exists on the impacts of minor changes in spatial resolution (i.e. submetre to about 1.5 m) in very high-resolution aerial imagery (i.e. 2 m resolution or less).This study compared the impact of spatial resolution on land/water classifications of an area dominated by coastal marsh vegetation in Louisiana, USA, using 1:12,000 scale colour-infrared analogue aerial photography (AAP) scanned at four different dot-per-inch resolutions simulating ground sample distances (GSDs) of 0.33, 0.54, 1, and 2 m. Analysis of the impact of spatial resolution on land/water classifications was conducted by exploring various spatial aspects of the classifications including density of waterbodies and frequency distributions in waterbody sizes. This study found that a small-magnitude change (1–1.5 m) in spatial resolution had little to no impact on the amount of water classified (i.e. percentage mapped was less than 1.5%), but had a significant impact on the mapping of very small waterbodies (i.e. waterbodies ≤ 250 m2). These findings should interest those using temporal image classifications derived from very high-resolution aerial photography as a component of long-term monitoring programs.

Morphological characteristics of urban water bodies: mechanisms of change and implications for ecosystem function.

The size, shape, and connectivity of water bodies (lakes, ponds, and wetlands) can have important effects on ecological communities and ecosystem processes, but how these characteristics are influenced by land use and land cover change over broad spatial scales is not known. Intensive alteration of water bodies during urban development, including construction, burial, drainage, and reshaping, may select for certain morphometric characteristics and influence the types of water bodies present in cities. We used a database of over one million water bodies in 100 cities across the conterminous United States to compare the size distributions, connectivity (as intersection with surface flow lines), and shape (as measured by shoreline development factor) of water bodies in different land cover classes. Water bodies in all urban land covers were dominated by lakes and ponds, while reservoirs and wetlands comprised only a small fraction of the sample. In urban land covers, as compared to surrounding undeveloped land, water body size distributions converged on moderate sizes, shapes toward less tortuous shorelines, and the number and area of water bodies that intersected surface flow lines (i.e., streams and rivers) decreased. Potential mechanisms responsible for changing the characteristics of urban water bodies include: preferential removal, physical reshaping or addition of water bodies, and selection of locations for development. The relative contributions of each mechanism likely change as cities grow. The larger size and reduced surface connectivity of urban water bodies may affect the role of internal dynamics and sensitivity to catchment processes. More broadly, these results illustrate the complex nature of urban watersheds and highlight the need to develop a conceptual framework for urban water bodies.

Microclimatic variation in multiple Salamandra algira populations along an altitudinal gradient: phenology and reproductive strategies

Salamandra algira is one of the southernmost species of the genus , and most of its ecology remains poorly known. We studied the microhabitat conditions of the sites occupied by several populations of S. algira along an altitudinal gradient, and the use of water bodies for reproduction. The microclimate conditions were analysed at six sites in northern Morocco: one site in Beni Snassen massif ( S. algira spelaea ), two in the Middle Atlas and central Rif mountains ( S. algira splendens ), and three in the western Rif mountains and Peninsula Tingitana ( S. algira tingitana ), where a viviparous population also occurs. The microclimate was characterized using temperature and relative humidity data loggers for a period of two years. We also measured the surface area and depth of the water bodies where we found S. algira larvae. Our results showed an autumn-winter reproductive period for all ovoviviparous populations studied . In most of the aquatic habitats examined, larvae appeared between November and March, although this period could extend to May at higher altitudes. Larval abundance and their size variability did not correlate with water body size or microclimate conditions. The decrease in the number of larvae per water body coincided with the existence of suitable conditions for post-metamorphic dispersal. Salamandra algira occurred in regions with moist conditions (annual average relative humidity greater than 64 %) and with mean annual temperatures of 13.6-18.6 °C, but populations were largely segregated along a gradient of humidity, with some showing higher and more constant values than others. The viviparous population occurs in a region with maritime influence and greater microclimate stability than the other sites studied.

Habitat requirements of charophytes—Evidence of species discrimination through distribution analysis

Charophytes play an important role in aquatic ecosystems but there is a lack of knowledge on the ecology of these macroalgae. Our aim was to characterise the habitat of 12 charophyte species from 78 sites in Switzerland characterised by a set of environmental variables considered critical to the physiology and survival of these plants (climate, land-use, morphometry and chemistry). We searched (i) to evaluate how environmental gradients explain the distribution of species; and (ii) to identify if some species have narrower habitat range than others (“specialist” vs “generalist” species). The Outlying Mean Index (OMI) measures the distance between the mean habitat conditions used by a given species and the mean habitat conditions of all studied waterbodies and was used to analyse the distribution of species. Waterbody size, conductivity and altitude were the most discriminating habitat variables of 7 of the 12 species, followed by calcium and total phosphorus. Chara strigosa is considered a specialist of cold oligotrophic hard waters, and three as generalists (Chara contraria, Chara globularis, Chara vulgaris) with respect to our set of charophyte sites. We demonstrate that charophyte species occur together in a narrow environmental envelope but do not occupy exactly similar habitats. Despite a discrepancy among absolute optima of species in different countries, the relative position of species is likely to be transferable to other regions. Improving our understanding about the ecology of charophyte species by considering a broader scale dataset and more fine-scale biotic and abiotic factors is proposed as an important perspective.

Will charophyte species increase or decrease their distribution in a changing climate?

Most charophyte species are threatened across Europe. Understanding their current and future distribution is a challenge for their conservation. We looked for species distribution models (SDM) and for increasing or decreasing species occurrence under a future climate scenario in Switzerland. Firstly, we modeled the occurrence of charophyte species in 1402 Swiss localities using presence–absence data and environmental variables (waterbody size, mean July temperature, July precipitation, soil calcium carbonate content and proportions of land used by agriculture and forest cover in the catchment area and in the surroundings). We used generalized additive models (GAM) to analyze the data. Secondly, based on the models, we predicted the occurrence of the species in 21,092 localities listed in Switzerland. Thirdly, we applied a climate scenario to our models (2°C mean July temperature increase and 15% reduction in July precipitation) and predicted species occurrence under these new conditions. Twelve charophyte species were modeled successfully. The major driver of species distribution was the waterbody size, followed by climate and land-use variables. We detected predicted impacts of climate changes on the species occurrence and identified the potential winners and losers. About half of the species are predicted to become losers; they colonize the littoral zone of lakes. Other charophytes are potential winners; the majority of them colonize small waterbodies.

The Dragonfly Association Index (Insecta: Odonata)—a Tool for the Type‐Specific Assessment of Lowland Rivers

AbstractSpecies traits of 57 Odonata species occurring in the Austrian bioregion Eastern Ridges and Lowlands (ecoregion Hungarian Lowlands; Illies, ) were defined by factor loadings of 12 habitat parameters: stream sections crenon, rhithron and potamon; flow velocity; standing water; temporary water; size of water body; open water; open banks; submerged macrophytes; reed; and riparian trees. On the basis of the species‐specific configurations of these habitat parameters, cluster analysis revealed seven dragonfly associations with different habitat needs: association of open waters, association of sparsely vegetated banks, association of reed and riparian trees, association of reed and submerged macrophytes, association of temporary waters, rhithron association and potamon association. Correlations between the associations' habitat requirements and the habitat parameters of the seven (near‐)natural river types, which are present in this bioregion were performed to define river type‐specific association compositions. From these results, a dragonfly association index was created to assess the ecological status of these rivers within the five‐tiered system of the European Union Water Framework Directive, emphasizing hydro‐morphological aspects by comparing the type‐specific reference situation with the actual status quo of dragonfly colonization. The method was applied at different rivers, particularly for the purpose of evaluating restoration measures. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Angler effort and catch within a spatially complex system of small lakes

Spatial layout of waterbodies and waterbody size can affect a creel clerk’s ability to intercept anglers for interviews and to accurately count anglers, which will affect the accuracy and precision of estimates of effort and catch. This study aimed to quantify angling effort and catch across a spatially complex system of 19 small (<100ha) lakes, the Fremont lakes. Total (±SE) angling effort (hours) on individual lakes ranged from 0 (0) to 7,137 (305). Bank anglers utilized 18 of the 19 lakes, and their mean (±SE) trip lengths (hours) ranged from 0.80 (0.31) to 7.75 (6.75), depending on the waterbody. In contrast, boat anglers utilized 14 of the 19 lakes, and their trip lengths ranged from 1.39 (0.24) to 4.25 (0.71), depending on the waterbody. The most sought fishes, as indexed by number of lakes on which effort was exerted, were anything (17 of 19 lakes), largemouth bass Micropterus salmoides (15 of 19 lakes), and channel catfish Ictalurus punctatus (13 of 19 lakes). Bluegill Lepomis machrochirus, crappie Pomoxis spp., and largemouth bass were caught most frequently across the lakes, but catch rates varied considerably by lake. Of the 1,138 parties interviewed, most parties (93%) visited a single lake but there were 77 (7%) parties that indicated that they had visited multiple lakes during a single day. The contingent of parties that visited more than one lake a day were primarily (87%) bank anglers.. The number of lake-to-lake connections made by anglers visiting more than one waterbody during a single day was related to catch rates and total angling effort. The greater resolution that was achieved with a lake specific creel survey at Fremont lakes revealed a system of lakes with a large degree of spatial variation in angler effort and catch that would be missed by a coarser, system-wide survey that did not differentiate individual lakes.

Variation analysis of lake extension in space and time from MODIS images using random sets

Understanding inundation in wetlands may benefit from a joint variation analysis in changes of size, shape, position and extent of water bodies. In this study, we modeled wetland inundation as a random spread process and used random sets to characterize stochastic properties of water body extents. Periodicity, trend and random components were captured by monthly and yearly random sets that were derived from multitemporal images. The Covering-Distance matrix and related operators summarized and visualized the spatial pattern and quantified the similarity of different inundation stages. The study was carried out on the Poyang Lake wetland area in China, and MODIS images for a period of eleven years were used. Results revealed the substantial seasonal dynamic pattern of the inundation and a subtle interannual change in its extension from 2000 to 2010. Various spatial properties including the size, shape, position and extent are visible: areas of high flooding risk are very elongated and locate along the water channel; few of the inundation areas tend to be more circular and spread extensively; the majority of the inundation areas have various extent and size in different month and year. Large differences in the spatial distribution of inundation extents were shown to exist between months from different seasons. A unique spatial pattern occurred during those months that a dramatic flooding or recession happened. Yearly random sets gave detailed information on the spatial distributions of inundation frequency and showed a shrinking trend from 2000 to 2009. 2003 is the partition year in the declining trend and 2010 breaking the trend as an abnormal year. Besides, probability bounds were derived from the model for a region that was attacked by flooding. This ability of supporting decision making is shown in a simple management scenario. We conclude that a random sets analysis is a valuable addition to a frequency analysis that quantifies inundation variation in space and time.

Patterns of habitat use and selection by the capybara (Hydrochoerus hydrochaeris): a landscape‐scale analysis

AbstractHabitat selection analysis provides useful information on how animals become distributed in response to spatial heterogeneity. Here, we analyze the habitat use and selection of different water bodies (marsh, swamps and round shallow lakes) by capybaras (Hydrochoerus hydrochaeris) and their relation to environmental variables during contrasting climate‐hydrological seasons in the Esteros del Iberá (Corrientes, Argentina). We evaluated the intensity of use by capybaras through the total number of individuals (abundance) in each water body, the number and mean size of social groups, and the physical and vegetation characteristics of the environment. The capybaras used marsh and swamps according to availability in both seasons, while they used rounded shallow lakes less than their available would suggest in summer. The use intensity of different rounded shallow lakes estimated based on group size did not show significant differences. In contrast, significant differences were observed when evaluated by the number of individuals in each rounded shallow lake. Different intensity of use was closely associated with environmental and vegetation characteristics. The results show that habitat suitability for capybaras is associated with vegetation cover and “embalsados” in the low‐lying area rather than with the morphometry of the rounded shallow lakes. The pattern of habitat selection may depend on forage quality, water availability for thermoregulation and mating, and presence of shelter and resting sites. On the other hand, the present study shows how the size, shape and the abundance of different types of water bodies affect population abundance and density.

Old world versus new world: life-history alterations in a successful invader introduced across Europe

We examined differences in pumpkinseed (Lepomis gibbosus) life-history traits between native North American and introduced European populations, and tested three life-history predictions related to the effect of temperature, growth, waterbody size, and the presence/absence of predators on native and non-native populations. Pumpkinseed populations exhibit more ‘opportunistic’ traits (earlier maturity, smaller size at maturity, and higher reproductive allocation) in their introduced European range than those in their native range. Predictions of life-history traits were improved when indicators of juvenile growth rate (mean length at age 2), waterbody size (surface area), and thermal regime (air temperature degree-days above 10 °C) were incorporated into models along with continental location, but European pumpkinseed populations exhibit more opportunistic life-history traits than North American populations even when these factors are accounted for. Native pumpkinseed in waterbodies containing piscivores mature later and at a larger size, and have lower gonadosomatic indices than those in waterbodies lacking piscivores, whereas there is no significant difference in the same three life-history traits between European waterbodies containing or lacking piscivores. Because congeneric competitors of the pumpkinseed are absent from Europe, the apparent absence of a predator life-history effect there could also be due to the absence of the major sunfish competitors. In either case, the evolution and maintenance of more opportunistic traits in European pumpkinseed can likely be attributed to enemy release, and this may explain the successful establishment and spread of pumpkinseed in many parts of Europe.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-013-2776-7) contains supplementary material, which is available to authorized users.

Effects of isolation and environmental variables on fish community structure in the Brazilian Amazon Madeira-Purus interfluve

Due to the existence of terrestrial barriers to freshwater fish dispersion, it is believed that its distribution is strongly associated with historical factors related to the formation of the habitats they occupy. By the other hand, some studies reveal the influence of abiotic conditions (such as size of water bodies, pH, conductivity) on the composition of fish fauna occurring in small streams. This study aimed to investigate whether drainage basins, because catchment boundaries are potential barriers to fish dispersion, or the physical structure and physico-chemical characteristics of water have a greater influence on fish community structure in small streams. We sampled 22 streams belonging to five drainage basins in the Madeira-Purus interfluve. Fish were caught with dip nets and a small trawl, and data were simultaneously obtained on structural characteristics of the streams and physico-chemical characteristics of the water. Community composition was analyzed using Non-Metric Multidimensional Scaling (NMDS), and variables related to structural and physico-chemical characteristics were summarized by Principal Component Analysis (PCA). Two explanatory models relating faunal composition to environmental factors were constructed: the first using only continuous variables and the second including the drainage basin as a categorical variable. The Akaike Information Criterion (AIC) and AIC weight were used to select the best model. Although structural and physico-chemical variables significantly contributed to explaining faunal composition, the model including the drainage basin was clearly the better of the two models (more than 90% support in the data). The importance of drainage basins in structuring fish communities in streams may have significant consequences for conservation planning in these environments.

Combined influence of water temperature, salinity and body size on energy budget in the sea cucumber Apostichopus japonicus Selenka

The worldwide demand for sea cucumber is outpacing the sustainable harvest capabilities of fisheries. Sea cucumber ranches and farms are striving to supplement wild harvest, but variable temperature and salinity conditions in pond culture systems make sea cucumber production challenging. In this study, we evaluated how water temperature, salinity and body size affected the energy budget of pond-cultured sea cucumber Apostichopus japonicus Selenka. An orthogonal design was used to identify the most suitable conditions for energy consumption and scope for growth (SFG). After the 42-day experimental period, we found that water temperature, salinity and body size significantly influenced energy consumption, while salinity and body size were the main influencing factors on SFG. Based on these results, we suggest that a water temperature of 16 A degrees C and a salinity of 30 g L-1 are optimal conditions for stocking sea cucumber A. japonicus with a body size of 37.34 +/- A 4.63 g. As such, the optimum stocking seasons for sea cucumber A. japonicus may be April in the spring and October in the autumn.

GIS analysis reveals the high diversity and conservation value of mollusc assemblages in the floodplain wetlands of the lower Bug River (East Poland)

The distribution and species richness of aquatic molluscs were analysed within a 186-km-long section of a large (755-km-long) lowland river floodplain using GIS maps. Special attention was paid to threatened species. An attempt was made to identify local ‘hotspots’ of molluscan diversity and to determine the most important areas for conservation based on species richness, number of threatened species and indices of synthetic conservation (Q) and centres of population density (ICD). Over four years of investigation, carried out in 176 water bodies, a rich malacofauna was identified: 58 species including 20 of elevated conservation concern. GIS maps revealed numerous ‘hotspots’ of mollusc species richness and higher incidence of threatened species, as well as areas characterized by raised Q and ICD indices. Water body size and hydrological connectivity positively influenced species richness and Q values. The highest values of these variables were found in large water bodies having limited surficial connectivity with the river channel. Species richness, numbers of threatened species, and Q and ICD values were significantly higher in younger permanent water bodies compared with semi-permanent or temporary ones representing advanced successional stages. Spatial visualization data collected in the study area indicate that the most valuable sites for the conservation of aquatic molluscs include both sides of the river in the lower part of the middle stretch of the lower Bug River valley. Copyright © 2013 John Wiley & Sons, Ltd.

Using new electrofishing technology to amp‐up fish sampling in estuarine habitats

A prototype, boat-mounted electrofisher capable of operation in estuarine waters (where electrical conductivities often exceed 20 000 µS cm(-1)) was assessed. Electrofishing was compared to fyke and mesh netting in four riverine estuaries and to seining in a lagoonal estuary (consisting of a series of brackish coastal lakes separated from the sea by a barrier system of sand dunes). Fish assemblage composition, length distributions and the probability of detecting ecological fish guilds (relating to estuary use, position in the water column and body size) were compared among gears. The assemblage composition of electrofishing samples differed from those of fyke nets in all riverine estuaries and from mesh netting in two. The assemblage composition of electrofishing samples differed from those of seining in structured seagrass habitats of the lagoonal estuary. When all species were pooled, the electrofisher sampled a broader range of lengths than either fyke or mesh netting in riverine estuaries or seining in lagoonal estuaries. The bias of electrofishing and netting towards particular species and size classes affected the probability of detecting some ecological guilds, highlighting the potential implications of gear choice on understanding estuarine ecological function. The detection of guilds varied with gear type and environmental conditions, including stratification, water depth and surface electrical conductivity. Assessments with the aim to characterize the structure of fish assemblages will benefit from the use of multiple gears. Electrofishing shows immense promise for discretely sampling highly structured habitats to test hypotheses about their use.

Water Body Distributions Across Scales: A Remote Sensing Based Comparison of Three Arctic Tundra Wetlands

Water bodies are ubiquitous features in Arctic wetlands. Ponds, i.e., waters with a surface area smaller than 104 m2, have been recognized as hotspots of biological activity and greenhouse gas emissions but are not well inventoried. This study aimed to identify common characteristics of three Arctic wetlands including water body size and abundance for different spatial resolutions, and the potential of Landsat-5 TM satellite data to show the subpixel fraction of water cover (SWC) via the surface albedo. Water bodies were mapped using optical and radar satellite data with resolutions of 4mor better, Landsat-5 TM at 30mand the MODIS water mask (MOD44W) at 250m resolution. Study sites showed similar properties regarding water body distributions and scaling issues. Abundance-size distributions showed a curved pattern on a log-log scale with a flattened lower tail and an upper tail that appeared Paretian. Ponds represented 95% of the total water body number. Total number of water bodies decreased with coarser spatial resolutions. However, clusters of small water bodies were merged into single larger water bodies leading to local overestimation of water surface area. To assess the uncertainty of coarse-scale products, both surface water fraction and the water body size distribution should therefore be considered. Using Landsat surface albedo to estimate SWC across different terrain types including polygonal terrain and drained thermokarst basins proved to be a robust approach. However, the albedo–SWC relationship is site specific and needs to be tested in other Arctic regions. These findings present a baseline to better represent small water bodies of Arctic wet tundra environments in regional as well as global ecosystem and climate models.

Are cladoceran diversity and community structure linked to spatial heterogeneity in urban landscapes and pond environments?

Biodiversity patterns in cladoceran communities were investigated in urban waterbodies in relation with residential land use, pond management, and waterbody environments. We evaluated species richness in the pelagic and littoral zones of eighteen waterbodies of a large Canadian city. Gamma diversity (26 species) observed at a small scale in the urban survey was important comparatively to large-scale surveys of lakes. Beta diversity ranged from 1 to 8 species among waterbodies. We tested if littoral species greatly contributed to regional diversity in urban waterbodies. Littoral species (Chydoridae, Ilyocryptidae, Macrothricidae, Polyphemidae) accounted for 58% of the total species pool. We distinguished five cladoceran assemblages associated to different waterbodies (temporary ponds, permanent lakes, and wetlands). Cladoceran communities were more diverse and variable in permanent lakes than in temporary ponds. Changes in cladoceran species assemblages among waterbodies were driven by variations in waterbody size and phosphorus enrichment, macrophyte and algal biomass, urban density, pond management practices, and the presence of potential predators as fish and macroinvertebrates. Our study indicates that both artificial ponds and lakes and natural wetlands are valuable habitats for the conservation of cladoceran biodiversity and rare endemic species in urban regions. Further research on pond management strategies promoting urban aquatic biodiversity should be undertaken.

Spatiotemporal dynamic of surface water bodies using Landsat time-series data from 1999 to 2011

Detailed information on the spatiotemporal dynamic in surface water bodies is important for quantifying the effects of a drying climate, increased water abstraction and rapid urbanization on wetlands. The Swan Coastal Plain (SCP) with over 1500 wetlands is a global biodiversity hotspot located in the southwest of Western Australia, where more than 70% of the wetlands have been lost since European settlement. SCP is located in an area affected by recent climate change that also experiences rapid urban development and ground water abstraction. Landsat TM and ETM+ imagery from 1999 to 2011 has been used to automatically derive a spatially and temporally explicit time-series of surface water body extent on the SCP. A mapping method based on the Landsat data and a decision tree classification algorithm is described. Two generic classifiers were derived for the Landsat 5 and Landsat 7 data. Several landscape metrics were computed to summarize the intra and interannual patterns of surface water dynamic. Top of the atmosphere (TOA) reflectance of band 5 followed by TOA reflectance of bands 4 and 3 were the explanatory variables most important for mapping surface water bodies. Accuracy assessment yielded an overall classification accuracy of 96%, with 89% producer’s accuracy and 93% user’s accuracy of surface water bodies. The number, mean size, and total area of water bodies showed high seasonal variability with highest numbers in winter and lowest numbers in summer. The number of water bodies in winter increased until 2005 after which a decline can be noted. The lowest numbers occurred in 2010 which coincided with one of the years with the lowest rainfall in the area. Understanding the spatiotemporal dynamic of surface water bodies on the SCP constitutes the basis for understanding the effect of rainfall, water abstraction and urban development on water bodies in a spatially explicit way.