Availability Of Aquatic Habitats Research Articles

Channel Morphology Change after Restoration: Drone Laser Scanning versus Traditional Surveying Techniques

Accurate and precise measures of channel morphology are important when monitoring a stream post-restoration to determine changes in stability, water quality, and aquatic habitat availability. Practitioners often rely on traditional surveying methods such as a total station for measuring channel metrics (e.g., cross-sectional area, width, depth, and slope). However, these methods have limitations in terms of coarse sampling densities and time-intensive field efforts. Drone-based lidar or drone laser scanning (DLS) provides much higher resolution point clouds and has the potential to improve post-restoration monitoring efforts. For this study, a 1.3-km reach of Stroubles Creek (Blacksburg, VA, USA), which underwent a restoration in 2010, was surveyed twice with a total station (2010 and 2021) and twice with DLS (2017 and 2021). The initial restoration was divided into three treatment reaches: T1 (livestock exclusion), T2 (livestock exclusion and bank treatment), and T3 (livestock exclusion, bank treatment, and inset floodplain). Cross-sectional channel morphology metrics were extracted from the 2021 DLS scan and compared to metrics calculated from the 2021 total station survey. DLS produced 6.5 times the number of cross sections over the study reach and 8.8 times the number of points per cross section compared to the total station. There was good agreement between the metrics derived from both surveying methods, such as channel width (R2 = 0.672) and cross-sectional area (R2 = 0.597). As a proof of concept to demonstrate the advantage of DLS over traditional surveying, 0.1 m digital terrain models (DTMs) were generated from the DLS data. Based on the drone lidar data, from 2017 to 2021, treatment reach T3 showed the most stability, in terms of the least change and variability in cross-sectional metrics as well as the least erosion area and volume per length of reach.

Irrigation dams threaten Brazilian biodiversity.

Brazil is among the main contributors to global biodiversity, which, in turn, provides extensive ecosystem services. Agriculture is an activity that benefits greatly from these ecosystem services, but at the same time is degrading aquatic and terrestrial ecosystems and eroding Brazilian biodiversity. This conflict is growing, as emerging unsustainable legislative proposals that will benefit the agricultural sector are likely to accelerate the decline of biodiversity. One such initiative (Bill 1282/2019) would change Brazil's "Forest Code" (Law 12,651/2012) to facilitate construction of irrigation dams in Permanent Preservation Areas, a category that includes strips (with or without vegetation) along the edges of watercourses. Two other similar bills are advancing through committees in the Chamber of Deputies. Here we provide details of these three bills and discuss their consequences for Brazil's biodiversity if they are approved. Expected negative impacts with changes in the legislation include: increased deforestation; siltation; habitat fragmentation; introduction of non-native species; reduction in the availability of aquatic habitats; and changes in biogeochemical process. These proposals jeopardize biodiversity and may compromise the negotiations for an agreement between Mercosur and the European Union.

Assessing downstream aquatic habitat availability relative to headwater reservoir management in the Henrys Fork Snake River

AbstractReservoirs are sometimes managed to meet agricultural and other water demands, while also maintaining streamflow for aquatic species and ecosystems. In the Henrys Fork Snake River, Idaho (USA), irrigation‐season management of a headwater reservoir is informed by a flow target in a management reach ~95 km downstream. The target is in place to meet irrigation demand and maintain aquatic habitat within the 11.4 km management reach and has undergone four flow target assignments from 1978 to 2021. Recent changes to irrigation‐season management to maximize reservoir carryover warranted investigation into the flow target assignment. Thus, we created a streamflow‐habitat model using hydraulic measurements, habitat unit mapping, and published habitat suitability criteria for Brown Trout (Salmo trutta), Rainbow Trout (Oncorhynchus mykiss), and Mountain Whitefish (Prosopium williamsoni). We used model output to compare habitat availability across two management regimes (1978–2017 and 2018–2021). We found that efforts to minimize reservoir releases in 2018–2021 did not reduce mean irrigation‐season fish habitat relative to natural flow, but did reduce overall fish habitat variability during the irrigation season compared to streamflow management in 1978–2017. Field observations for this research led to an adjusted flow target in 2020 that moved the target location downstream of intervening irrigation diversions. Using our model output, we demonstrated that moving the location of the target to account for local irrigation diversions will contribute to more consistently suitable fish habitat in the reach. Our study demonstrates the importance of site selection for establishing environmental flow targets.

Predictions and drivers of sub-reach-scale annual streamflow permanence for the upper Missouri River basin: 1989–2018

The presence of year-round surface water in streams (i.e., streamflow permanence) is an important factor for identifying aquatic habitat availability, determining the regulatory status of streams, managing land use change, allocating water resources, and designing scientific studies. However, accurate, high resolution, and dynamic prediction of streamflow permanence that accounts for year-to-year variability at a regional extent is a major gap in modeling capability. Herein, we expand and adapt the U.S. Geological Survey (USGS) PRObability of Streamflow PERmanence (PROSPER) model from its original implementation in the Pacific Northwest (PROSPERPNW) to the upper Missouri River basin (PROSPERUM), a geographical region that includes mountain and prairie ecosystems of the northern United States. PROSPERUM is an empirical model used to estimate the probability that a stream channel has year-round flow in response to climatic conditions (monthly and annual) and static physiographic predictor variables of the upstream basin. The structure and approach of PROSPERUM are generally consistent with the PROSPERPNW model but include improved spatial resolution (10 m) and a longer modeling period. Average model accuracy was 81 %. Drainage area, upstream proportion as wetlands, and upstream proportion as developed land cover were the most important predictor variables. The PROSPERUM model identifies decreases in streamflow permanence during climatically drier years, although there is variability in the magnitude across basins highlighting geographically varying sensitivity to drought. Variability in the response of perennial streams to drought conditions among basins in the study area was also observed.

A Process-based Model with Temperature, Water, and Lab-derived Data Improves Predictions of Daily Culex pipiens/restuans Mosquito Density.

While the number of human cases of mosquito-borne diseases has increased in North America in the last decade, accurate modeling of mosquito population density has remained a challenge. Longitudinal mosquito trap data over the many years needed for model calibration, and validation is relatively rare. In particular, capturing the relative changes in mosquito abundance across seasons is necessary for predicting the risk of disease spread as it varies from year to year. We developed a discrete, semi-stochastic, mechanistic process-based mosquito population model that captures life-cycle egg, larva, pupa, adult stages, and diapause for Culex pipiens (Diptera, Culicidae) and Culex restuans (Diptera, Culicidae) mosquito populations. This model combines known models for development and survival into a fully connected age-structured model that can reproduce mosquito population dynamics. Mosquito development through these stages is a function of time, temperature, daylight hours, and aquatic habitat availability. The time-dependent parameters are informed by both laboratory studies and mosquito trap data from the Greater Toronto Area. The model incorporates city-wide water-body gauge and precipitation data as a proxy for aquatic habitat. This approach accounts for the nonlinear interaction of temperature and aquatic habitat variability on the mosquito life stages. We demonstrate that the full model predicts the yearly variations in mosquito populations better than a statistical model using the same data sources. This improvement in modeling mosquito abundance can help guide interventions for reducing mosquito abundance in mitigating mosquito-borne diseases like West Nile virus.

The use of wetted perimeter as habitat proxy to assess environmental flows in Southern Quebec rivers (Canada)

Environmental flows assessment in eastern Canada, and particularly in the province of Quebec, is mainly based on hydrological assessment of historical data during low flow periods. The mean 7-day low flow with return periods of two (7Q2) and ten years (7Q10) are two flow metrics currently used by the Quebec Department of Environment and Fight against Climate Change to prescribe minimum flow and/or maximum water abstraction while maintaining the functions and health of riverine ecosystems. This study investigated the use of the wetted perimeter as an additional environmental flows assessment method. This tool can be used by water managers to maintain the availability of river habitats during low flow periods. Twenty flow metrics were computed for inter-annual, summer and winter periods, for 43 sites from 35 rivers, and analysed to study the changes in wetted perimeter with flow. In addition, the flow associated with maximum curvature (breakpoint) of the flow-wetted perimeter function (QMC) was analyzed. Results provided a better understanding of local changes of river hydraulics and possible aquatic habitat availability associated with different flow metrics. The relevance of using a wetted perimeter threshold (WPSQMC) combined with flow thresholds (Tennant method) was also discussed. The two “fair” Tennant flow thresholds, apart from the twenty flow metrics, would provide sufficient available habitat all year long with corresponding WPSQMC thresholds of 88% and 95% of the 43 river sites. The median discharge for August flow metric for summer and the median discharge for the month with the lowest flow metric value for winter (usually February), provided the highest wetted perimeter in relative terms (72% and 79% respectively of the river sites) compared to the WPSQMC threshold. Using the 7Q2 flow metric would mean maintaining sufficient available habitat for 50%, 60% and 72% of the river sites for respectively inter-annual, summer and winter periods. Considering the single WPSQMC threshold, its associated flow provided the highest values for 16% of the river sites and the second highest one for 9% of the river sites with a single seasonal flow metric value high enough for summer or winter. This study showed that the wetted perimeter is a tool providing additional information on both river morphology and changes in potential aquatic habitat as a function of flow for river sites with small catchment size and low mean annual flow values. Indeed, the wetted perimeter can be very useful in the overall assessment of environmental flows.

Evaluation of the impact of urban river bends on the enhancement of aquatic habitats using a two-dimensional habitat suitability model

The complex hydro-morphology of river bends plays an important role for creating and maintaining diverse habitat conditions for aquatic organisms. In this study,a dedicated standalone piece of software for benthic habitat simulation, which couples a two-dimensional (2D) depth-averaged water–sediment mathematical model with an instream flow incremental methodology, was devised to quantitatively evaluate the impact of channel bends on enhancing aquatic habitats. The multi-species integrated suitability index (CSI) curves based on three ecological variables were obtained. The test site was a 1.7-km-long stretch of the Jin Jiang River, which is a tributary of the Min Jiang River that flows through Huayang Town in Chengdu City, China. The potential value of aquatic habitats was quantitatively evaluated using the weighted usable area (WUA). The predicted WUA in the bend reach was 10.2%–16.6% greater than that in the straight reach. Moreover, the mean WUA decline rate was ~7.2% in the straight reach and ~5.6% in the bend reach. With increase in discharge, the WUA decreased more slowly in the bend reach compared to the straight reach. Our study indicates that for improving the aquatic habitats in urban rivers, the channel bends are beneficial. Compared with straight reaches, they not only could improve the availability of aquatic habitats but could also reduce the negative impact of the changes of discharge on the habitat. To summarize, this study provides a specific reference for ecological restoration.

Chinook salmon rearing habitat–discharge relationships change as a result of morphodynamic processes

AbstractRelationships between fluvial aquatic habitat availability and discharge are often assumed to remain static when used with hydrologic datasets to analyze changes in habitat availability over time. Despite this assumption, studies have observed significant changes in aquatic habitat availability before and after restoration projects, dam removals, and extreme flood events. However, research is lacking on how aquatic habitat changes as a result of morphodynamic processes during more commonly occurring hydrologic conditions. This study compared Chinook salmon (Oncorhynchus tshawytscha) rearing habitat availability at 19 discharges before and after a relatively mild 8‐year hydrologic period punctuated with modest floods on the lower Yuba River in California, USA. During this time, the total area of rearing habitat remained relatively consistent at discharges <2× bankfull but decreased by up to 25% at discharges >2× bankfull. Significant decreases in rearing habitat area appeared to be the result of widespread erosion on floodplains, terraces, and lateral bars, even after only modest floods. As a result, spatially delineated areas of lost habitat tended to increase in water depth and velocity at baseflow, bankfull, and floodplain‐filling discharges, while areas of gained habitat decreased in depth and velocity. Although these specific results may not apply to all rivers around the world, the finding that habitat–discharge relationships change as a result of morphodynamic processes likely does transfer globally and should be considered when making long‐term regulatory and management decisions, such as instream flow requirements and habitat restoration plans.

Scale-dependent effects of terrestrial habitat on genetic variation in the great crested newt (Triturus cristatus)

ContextTerrestrial landscapes surrounding aquatic habitat influence the persistence of amphibian spatially structured populations (SSPs) via their crucial role in providing estivation and overwintering sites, facilitating or hampering dispersal and colonisation, and consequently the maintenance or loss of genetic diversity.ObjectivesTo highlight the landscape drivers of genetic variation, we investigated the relationship between the level of genetic variation measured within ponds of the great crested newt (Triturus cristatus), and the composition of the surrounding landscape at various spatial scales.MethodsBased on the sampling of 40 ponds in 13 SSPs, the influence of landscape features on several estimators of genetic variation was investigated via linear mixed models, with effects within and between SSPs incorporated.ResultsThe best models depended on the spatial scale, with more significant associations within radii of 50 and 100 m of core ponds, particularly for allelic richness. Responses within and between SSPs were mostly similar. The availability of aquatic habitat in the landscape had a positive effect, while woodland, arable land and pasture had different effects depending on scale and response variable. Total length of roads within a 250 m radius influenced effective population size negatively.ConclusionsOur results stress the need to investigate the influence of environmental predictors at multiple spatial scales for an adequate understanding of ongoing processes. Generally, the landscape affected genetic variation similarly within and between SSPs. This allowed us to provide general guidelines for the persistence of great crested newt populations, with an emphasis on the importance of the aquatic habitat.

Aquatic habitat changes within the channelized and impounded Arkansas River, Arkansas, USA

AbstractRiver‐wide changes in morphologic character following channelization and impoundment alter the occurrence and distribution of surface water and available habitats for aquatic organisms. Quantifying patterns of creation, redistribution or disappearance of habitats at river‐wide and decadal spatiotemporal scales can promote understanding regarding trajectories of different habitat types following alteration and prospects of direct habitat enhancement projects within altered alluvial rivers. Newly available remote‐sensing tools and databases may improve detection of river‐wide changes in habitat through time. We used a combination of remote‐sensing data and generalized linear models to assess changes in surface water coverage from 1984 to 2015 among aquatic habitats of 496 km of the Arkansas River within Arkansas, USA. Changes through time in surface area of permanent and episodically inundated areas — and thus the availability of aquatic habitat — were variable along the river. Overall, the river lost a total 2.1% of permanent and 12.1% of episodic water surface area. The general trend of loss of off‐main‐channel habitat and increased coverage of permanent water along main‐channel habitats may indicate a long‐term transition (i.e. ramp‐type disturbance) within areas of the Arkansas River where backwaters are transitioning to terrestrial environments, and habitat heterogeneity in the main channel is decreasing. As such, a decadal‐scale change of channel form and backwater habitats may be the dominant pattern with limited regeneration of diverse habitat types. Understanding changes to permanent and episodic water availability may aid predictions regarding ecological effects of channelization and impoundments, including both increases and decreases in riverine productivity, biotic diversity and population abundances through space and time. Water resource managers and biologists can use information regarding river‐wide changes in habitat availability obtained through remote sensing data to direct river management practices, including dredging and side‐channel construction, and to assess ecological responses to such changes.

Cemeteries in Miami-Dade County, Florida are important areas to be targeted in mosquito management and control efforts.

Definable habitats at the neighborhood level provide a wide range of favorable habitats with optimal conditions and environmental resources for mosquito survival. Problematic habitats for controlling mosquitoes in urban environments such as tire shops, bromeliad patches, and construction sites must be taken into consideration in the development of effective mosquito management and control in urban areas. Cemeteries are often located in highly urbanized areas serving as a haven for populations of vector mosquito species due to the availability of natural resources present in most cemeteries. Even though Miami-Dade County, Florida was the most affected area in the United States during the Zika virus outbreak in 2016 and is currently under a mosquito-borne illness alert after 14 confirmed locally transmitted dengue cases, the role of cemeteries in the proliferation of vector mosquitoes is unknown. Therefore, our objective was to use a cross-sectional experimental design to survey twelve cemeteries across Miami-Dade County to assess if vector mosquitoes in Miami can be found in these areas. Our results are indicating that vector mosquitoes are able to successfully exploit the resources available in the cemeteries. Culex quinquefasciatus was the most abundant species but it was neither as frequent nor present in its immature form as Aedes aegypti and Aedes albopictus. This study revealed that vector mosquitoes, such as Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus are successfully exploiting the resources available in these areas being able to thrive and reach high numbers. Mosquito control strategies should consider both long-term strategies, based on changing human behavior to reduce the availability of aquatic habitats for vector mosquitoes; as well as short-term strategies such as drilling holes or adding larvicide to the flower vases. Simple practices would greatly help improve the effectiveness of mosquito management and control in these problematic urban habitats.

Integrated analysis of flow, form, and function for river management and design testing

AbstractThe extent and timing of many river ecosystem functions is controlled by the interplay of streamflow dynamics with the river corridor shape and structure. However, most river management studies evaluate the role of either flow or form without regard to their dynamic interactions. This study develops an integrated modelling approach to assess changes in ecosystem functions resulting from different river flow and form configurations. Moreover, it investigates the role of temporal variability in such flow–form–function trade‐offs. The use of synthetic, archetypal channel forms in lieu of high‐resolution topographic data reduces time and financial requirements, overcomes site‐specific topographic features, and allows for evaluation of any morphological structure of interest. In an application to California's Mediterranean‐montane streams, the interacting roles of channel form, water year type, and hydrologic impairment were evaluated across a suite of ecosystem functions related to hydrogeomorphic processes and aquatic habitat. Channel form acted as the dominant control on hydrogeomorphic processes, whereas water year type controlled salmonid habitat functions. Streamflow alteration for hydropower increased redd dewatering risk and altered aquatic habitat availability. Study results highlight critical trade‐offs in ecosystem function performance and emphasize the significance of spatio‐temporal diversity of flow and form at multiple scales for maintaining river ecosystem integrity. The proposed approach is broadly applicable and extensible to other systems and ecosystem functions, where findings can be used to inform river management and design testing.

Potential barriers to upstream fish passage caused by anthropogenic river modifications: A computer modeling study of emerald shiners (Notropis atherinoides) in the upper Niagara River

Anthropogenic modifications at the head of the Niagara River attributed to land reclamation and the installation of vertical, bulkhead seawalls have altered the river channel, leading to increased water velocities and reduced availability of aquatic habitat. As a result of the increased velocities in the channel, concerns have been raised that the habitat connectivity of the emerald shiner (Notropis atherinoides), a key forage species for sportfish and threatened avian species, has been reduced between Lake Erie and the upper Niagara River. In this study, the influence of water velocity stressors on emerald shiner movement was assessed by identifying potential hydrodynamic barriers to upstream fish movement using a combination of depth-averaged velocities simulated in a 2-D hydrodynamic model and field measurements collected with a current meter. Results indicate that high velocities (in excess of 2.0ms−1) immediately downstream of the Peace Bridge, an international road crossing between Buffalo, NY, USA and Fort Erie, Ontario, Canada, restrict potential emerald shiner movement to within close proximity of either shoreline. Along both shorelines, several additional threats to successful upstream passage exist, the largest of which are located along vertical bulkhead seawalls. The extent of the identified potential barriers fluctuates slightly with water level, but the locations remain consistent. Finally, of the potential barriers identified using the model, the field measurements indicate the seawall along Broderick Park, along the U.S. shoreline, is the most substantial impediment to upstream movement, as velocities within several shiner body-lengths of the shoreline remain between 0.83 and 1.18ms−1 for nearly 200m. The results of this study, in conjunction with empirical estimates of passage success, swimming tests on shiners native to the Niagara River, and additional field measurements will help determine if remediation work is warranted to facilitate upstream passage at the identified impediments.

Seasonal variation in fish trophic networks in two clear-water streams in the Central Llanos region, Venezuela

ABSTRACT Food webs are not static entities; consumer resource interactions vary in both time and space, which complicates depiction and comparisons of food web structures. We estimated fish assemblage structure and diets in two clear-water streams in the Venezuelan Llanos region (Charcote and Charcotico) and constructed trophic networks (sub-webs defined by fishes as the principal consumers) during four periods of the annual flood pulse. As stream conditions changed from high-water to low-water, we hypothesized that: 1) the piscivore-non-piscivore ratio would increase; 2) dietary diversity would decrease; 3) interspecific dietary overlap would decline; 4) fewer allochthonous food items would be consumed; and 5) food-web connectance would increase. The piscivore-non-piscivore abundance ratio was higher in both streams during the low-water period. Dietary diversity declined as water levels dropped and availability of aquatic habitats and resources declined, but interspecific dietary overlap was not lower. Contrary to our hypothesis, average interspecific dietary overlap increased at Charcote as the dry season progressed, even though dietary overlap among species was significantly lower than expected by chance. We did not find strong support for our hypotheses regarding seasonal patterns of consumption of allochthonous resources and food web connectance, both of which revealed little seasonal variation.

Mapping the Relative Probability of Common Toad Occurrence in Terrestrial Lowland Farm Habitat in the United Kingdom.

IntroductionThe common toad (Bufo bufo) is of increasing conservation concern in the United Kingdom (UK) due to dramatic population declines occurring in the past century. Many of these population declines coincided with reductions in both terrestrial and aquatic habitat availability and quality and have been primarily attributed to the effect of agricultural land conversion (of natural and semi-natural habitats to arable and pasture fields) and pond drainage. However, there is little evidence available to link habitat availability with common toad population declines, especially when examined at a broad landscape scale. Assessing such patterns of population declines at the landscape scale, for instance, require an understanding of how this species uses terrestrial habitat.MethodsWe intensively studied the terrestrial resource selection of a large population of common toads in Oxfordshire, England, UK. Adult common toads were fitted with passive integrated transponder (PIT) tags to allow detection in the terrestrial environment using a portable PIT antenna once toads left the pond and before going into hibernation (April/May-October 2012 and 2013). We developed a population-level resource selection function (RSF) to assess the relative probability of toad occurrence in the terrestrial environment by collecting location data for 90 recaptured toads.ResultsThe predicted relative probability of toad occurrence for this population was greatest in wooded habitat near to water bodies; relative probability of occurrence declined dramatically > 50 m from these habitats. Toads also tended to select habitat near to their breeding pond and toad occurrence was negatively related to urban environments.

Simulating riparian disturbance: Reach scale impacts on aquatic habitat in gravel bed streams

Large wood governs channel morphology, as well as the availability of in-stream habitat, in many forested streams. In this paper, we use a stochastic, physically based model to simulate wood recruitment and in-stream geomorphic processes, in order to explore the influence of disturbance history on the availability of aquatic habitat. Specifically, we consider the effects of fire on a range of stream sizes by varying the rate of tree toppling over time in a simulated forest characterized by a tree height of 30 m. We also consider the effects of forest harvesting with various riparian buffer sizes, by limiting the lateral extent of the riparian stand. Our results show that pulsed inputs of wood increase the availability and variability of physical habitat in the postfire period; reach-averaged pool area and deposit area double in small streams, while side channels increase by over 50% in intermediate-sized channels. By contrast, forest harvesting reduces the availability of habitat within the reach, though the effects diminish with increasing buffer size or stream width; in laterally stable streams the effects are minimal so long as buffer width is large enough for key pieces to be recruited to the reach. This research emphasizes the importance of natural disturbance in creating and maintaining habitat heterogeneity and shows that scenario-based numerical modeling provides a useful tool for assessing the historical range of variability associated with natural disturbance, as well as changes in habitat relevant to fish. It can be also used to inform forest harvesting and management.

Modeling channel morphodynamic response to variations in large wood: Implications for stream rehabilitation in degraded watersheds

Anthropogenic modification of forests has often decoupled streams from riparian ecosystems and altered natural wood recruitment processes. Extensive research has shown that large wood significantly impacts channel dynamics, especially in small and intermediate sized forested streams where wood pieces are similar in length to channel width, and many stream rehabilitation efforts now involve the addition of large wood to streams. The primary objective of this research is to investigate the relation between large wood and reach scale channel morphology and hydraulics using a physical model, in order to better inform stream rehabilitation programs and future modeling efforts. Four experiments, each comprising numerous five hour runs, were conducted using a Froude-scaled stream table with wood loads scaled to 0m3/m2, 0.011m3/m2, 0.016m3/m2, and 0.022m3/m2. The addition of large wood significantly decreased the reach-averaged velocity in all experiments, and was associated with decreased sediment transport and increased sediment storage in the reach. Increases in bed and water surface slope compensated for the loss of energy available to transport sediment, and enabled the system to reach a new steady state within the equivalent of 6 to 9years. Adding wood increased pool frequency, as well as the variability in cross-sectional depth, while causing the reach to undergo a transition from a plane-bed to a riffle-pool morphology. Retention of fine sediment increased the availability of fish spawning substrate, while increased water stage improved connectivity between the channel and the floodplain. The changes in habitat complexity were generally related to the wood load added to the reach, but were also dependent on the orientation and arrangement of the pieces. These results demonstrate that wood may exert a primary control on channel morphodynamics and the availability of aquatic habitat in intermediate sized streams, and suggest that the benefits from stream rehabilitation efforts are highly dependent on project scale. The relatively long time needed to realize habitat benefits demonstrates that long term monitoring of rehabilitation projects is necessary.

Aquatic habitat use by amphibians with specific reference toRana temporariaat high elevations (Retezat Mountains National Park, Romania)

Alpine areas are extreme habitats that require special adaptations and involve major trade-offs in terms of life history. Amphibians have the ability to adapt both their life history and developmental traits to alpine environments. Temperate amphibians depend on the quality and availability of aquatic habitats for reproduction. We explored the aquatic habitat used by amphibians in the alpine area of Retezat Mountains, Southern Carpathians, Romania. We surveyed 40 aquatic habitats in a 380 ha area delimited by mountain crests and drained by a steep valley. Each aquatic habitat was characterized using 10 environmental variables. Only three amphibian species occur at elevations above 1900 m, the most widespread being the Common Frog Rana temporaria. The Common Frog showed preference for breeding aquatic habitats, the variables of importance being altitude, solar radiation, water chemistry and grazing. Higher elevation and lower solar radiation decreased frog occurrence, while the impact of grazing favored the use of water bodies. Acidification is eminent in the area with pH dropping below 5 in 20% of the water bodies. Overall, amphibian occurrence in alpine area can be partly explained by the characteristics of aquatic habitats.

Early response of the platypus to climate warming

AbstractCombining a climatic envelope modelling technique with more than two centuries (1800–2009) of distribution records has revealed the effects of a changing climate on the egg‐laying monotreme, the platypus, Ornithorhynchus anatinus. We show that the main factor associated with platypus occurrence switched from aquatic habitat availability (estimated by rainfall) to thermal tolerances (estimated by annual maximum temperature) in the 1960s. This correlates directly with the change in the annual maximum temperature anomaly from cooler to warmer conditions in southeastern Australia. Modelling of platypus habitat under emission scenarios (A1B, A2, B1 and B2) revealed large decreases (>30%) in thermally suitable habitat by 2070. This reduction, compounded by increasing demands for water for agriculture and potable use, suggests that there is real cause for concern over the future status of this species, and highlights the need for restoration of thermal refugia within the platypus’ modelled range.

Spatial and temporal distribution patterns of Anopheles arabiensis breeding sites in La Reunion Island - multi-year trend analysis of historical records from 1996-2009

BackgroundAn often confounding facet of the dynamics of malaria vectors is the aquatic larval habitat availability and suitable conditions under which they can thrive. Here, we investigated the impact of environmental factors on the temporal and spatial distribution of larval habitats of Anopheles arabiensis in different locations on La Reunion Island.MethodsA retrospective examination was made from archival data which provided the complete enumeration of An. arabiensis breeding habitats in three distinct geographic zones - extending North-east, West and South of the island over 14 years, from January 1996 to December 2009. Data on the occurrence and the number of active larval habitats at each of a total of 4376 adjacent ellipsoid grid cells (216,506 square meters each) were used (1) to provide the geographic extent of breeding site availability from year to year and (2) to analyze associations with prevailing environmental factors, habitat types, and locations.ResultsAnopheles arabiensis utilized a spectrum of man-made and natural aquatic habitats, most of which were concentrated primarily in the rock pools located in ravines and river fringes, and also in the large littoral marshes and within the irrigated agricultural zones. The numbers of breeding site per sampling grid differed significantly in different parts of the island. In contrast to an originally more widespread distribution across the island in the 1950s, detailed geographic analyses of the data obtained in the period extending from 1996-2009 showed an intriguing clustered distribution of active breeding sites in three discontinuous geographic zones, in which aquatic habitats availability fluctuates with the season and year. Seasonality in the prevalence of anopheles breeding sites suggests significant responsiveness to climatic factors.ConclusionsThe observed retreat of An. arabiensis distribution range to lower altitudinal zones (< 400 m) and the upward shift in the most remote littoral areas in the northeast and southwest regions suggest the possible influence of biogeographic factors, changes in land use and control operations. The results of this study would allow for a more rational implementation of control strategies across the island.