Water Body Size Research Articles

Evidence of alternative states in freshwater lakes: A spatially-explicit model of submerged and floating plants

Freshwater systems provide iconic examples of ecological tipping points. In some lakes and ponds, changes to nutrient levels can drive sudden shifts between primary producer communities dominated by either submerged or floating plants. Several models, ranging in complexity, have been developed to understand the interaction between these primary producer groups. Previous field studies suggest that spatial (e.g., water body size) and temporal (e.g., seasonality) processes are important for the dynamics of this system in nature, but these processes cannot be included in most models without a significant increase in model complexity. Therefore, I developed a spatially- and temporally-explicit model of this system with moderate model complexity that extends a previous model, in which alternative states are known to occur. I found that under low (approximately ≤2mg total nitrogenL−1) or high (approximately ≥6mg total nitrogenL−1) nutrient levels, either submerged or floating plants dominated, respectively. At intermediate nutrient levels, simulations resulted in different final plant states, depending on the initial cover of floating and submerged plants, providing evidence for alternative states. Under most conditions, stable intermediate states were uncommon. Water body size had a large effect on the dynamics of the system, as observed in the field, but only if wind strengths increased with water body size and there was a prevailing wind direction. Surprisingly, species composition and trait diversity did not appear to have major effects on the final plant states. This model allows the integration of processes on multiple scales of biological organization, from species traits and composition, to climate and seasonality or ecosystem-level properties, and it complements the growing realization that spatial context has significant impacts on the dynamics of alternative states in nature.

The relative importance of aquatic and terrestrial variables for frogs in an urbanizing landscape: Key insights for sustainable urban development

Globally, urbanization threatens ∼950 amphibian species with extinction. Yet a lack of knowledge on the factors influencing common and infrequently encountered species in landscapes that are under increasing pressure from urban development is limiting effective conservation. We examined the relative importance of aquatic variables (pond) and terrestrial variables (at three spatial scales: 10m, 100m and 1km), for commonly and infrequently encountered frogs in an urbanizing forested landscape in southeastern Australia. Species richness and the occurrence of four common species were influenced by the aquatic environment (water body size, aquatic vegetation). Species richness also decreased with increasing urbanization within 1km. This trend was driven by a strong decrease in richness of infrequently encountered species with increasing road length within 1km from breeding ponds. Richness of infrequently encountered species also decreased with a reduction in forest cover within 10m to 1km from breeding ponds. Our findings suggest that frog conservation in urbanizing landscapes requires a mix of strategies across different spatial scales. Maintaining or re-establishing common frogs in urbanizing forested landscapes is likely to be achieved by providing ponds with suitable habitat. However, to conserve several frog species that are sensitive to forest loss and urbanization, breeding habitats need to be maintained within a network of large forest reserves.

REMOTELY-SENSED URBAN WET-LANDSCAPES: AN INDICATOR OF COUPLED EFFECTS OF HUMAN IMPACT AND CLIMATE CHANGE

Abstract. This study proposes the concept of urban wet-landscapes (loosely-defined wetlands) as against dry-landscapes (mainly impervious surfaces). The study is to examine whether the dynamics of urban wet-landscapes is a sensitive indicator of the coupled effects of the two major driving forces of urban landscape change – human built-up impact and climate (precipitation) variation. Using a series of satellite images, the study was conducted in the Kansas City metropolitan area of the United States. A rule-based classification algorithm was developed to identify fine-scale, hidden wetlands that could not be appropriately detected based on their spectral differentiability by a traditional image classification. The spatial analyses of wetland changes were implemented at the scales of metropolitan, watershed, and sub-watershed as well as based on the size of surface water bodies in order to reveal urban wetland change trends in relation to the driving forces. The study identified that wet-landscape dynamics varied in trend and magnitude from the metropolitan, watersheds, to sub-watersheds. The study also found that increased precipitation in the region in the past decades swelled larger wetlands in particular while smaller wetlands decreased mainly due to human development activities. These findings suggest that wet-landscapes, as against the dry-landscapes, can be a more effective indicator of the coupled effects of human impact and climate change.

REMOTELY-SENSED URBAN WET-LANDSCAPES: AN INDICATOR OF COUPLED EFFECTS OF HUMAN IMPACT AND CLIMATE CHANGE

This study proposes the concept of urban wet-landscapes (loosely-defined wetlands) as against dry-landscapes (mainly impervious surfaces). The study is to examine whether the dynamics of urban wet-landscapes is a sensitive indicator of the coupled effects of the two major driving forces of urban landscape change – human built-up impact and climate (precipitation) variation. Using a series of satellite images, the study was conducted in the Kansas City metropolitan area of the United States. A rule-based classification algorithm was developed to identify fine-scale, hidden wetlands that could not be appropriately detected based on their spectral differentiability by a traditional image classification. The spatial analyses of wetland changes were implemented at the scales of metropolitan, watershed, and sub-watershed as well as based on the size of surface water bodies in order to reveal urban wetland change trends in relation to the driving forces. The study identified that wet-landscape dynamics varied in trend and magnitude from the metropolitan, watersheds, to sub-watersheds. The study also found that increased precipitation in the region in the past decades swelled larger wetlands in particular while smaller wetlands decreased mainly due to human development activities. These findings suggest that wet-landscapes, as against the dry-landscapes, can be a more effective indicator of the coupled effects of human impact and climate change.

A Multiscale Framework for Deconstructing the Ecosystem Physical Template of High-Altitude Lakes

An ecosystem is generally sustained by a set of integrated physical elements forming a functional landscape unit—ecotope, which supplies nutrients, microclimate, and exchanges matter and energy with the wider environment. To better predict environmental change effects on ecosystems, particularly in critically sensitive regions such as high altitudes, it is imperative to recognise how their natural landscape heterogeneity works at different scales to shape habitats and sustain biotic communities prior to major changes. We conducted a comprehensive survey of catchment physical, geological and ecological properties of 380 high-altitude lakes and ponds in the axial Pyrenees at a variety of scales, to formulate and test an integrated model encompassing major flows and interactions that drive lake ecosystems. Three composite drivers encompassed most of the variability in lake catchment characteristics. In order of total percentage of variance explained, they were (i) hydrology/hydrodynamics—responsible for type and discharge of inlets/outlets, and for waterbody size; (ii) bedrock geomorphology, summarising geology, slope and fractal order—all dictating vegetation cover of catchment slope and lake shore, and the presence of aquatic vegetation; and (iii) topography, that is, catchment formation type—driving lakes connectivity, and the presence of summer snow deposits. Although driver (i) appeared to be local, (ii) and (iii) showed gradient changes along altitude and latitude. These three drivers differentiated several lake ecotopes based on their landscape similarities. The three-driver model was successfully tested on a riparian vegetation composition dataset, further illustrating the validity and fundamental nature of the concept. The findings inform on the relative contribution of scale-dependent catchment physical elements to lake ecotope and ecosystem formation in high-altitude lakes, which should be considered in any assessment of potentially major deleterious effects due to environmental/climate change.

Changes in Menidia beryllina Gene Expression and In Vitro Hormone-Receptor Activation After Exposure to Estuarine Waters Near Treated Wastewater Outfalls.

Fishes in estuarine waters are frequently exposed to treated wastewater effluent, among numerous other sources of contaminants, yet the impacts of these anthropogenic chemicals are not well understood in these dynamic and important waterways. Inland silversides (Menidia beryllina) at an early stage of development [12days posthatch (dph)] were exposed to waters from two estuarine wastewater-treatment outfall locations in a tidal estuary, the Sacramento/San Joaquin Delta (California, USA) that had varied hydrology and input volumes. The genomic response caused by endocrine-disrupting compounds (EDCs) in these waters was determined using quantitative polymerase chain reaction on a suite of hormonally regulated genes. Relative androgenic and estrogenic activities of the waters were measured using CALUX reporter bioassays. The presence of bifenthrin, a pyrethroid pesticide and known EDC, as well as caffeine and the anti-inflammatory pharmaceutical ibuprofen, which were used as markers of wastewater effluent input, were determined using instrumental analysis. Detectable levels of bifenthrin (2.89ng L(-1)) were found on one of the sampling dates, and caffeine was found on all sampling dates, in water from the Boynton Slough. Neither compound was detected at the Carquinez Strait site, which has a much smaller effluent discharge input volume relative to the receiving water body size compared with Boynton Slough. Water samples from both sites incubated in the CALUX cell line induced estrogenic and androgenic activity in almost all instances, though the estrogenicity was relatively higher than the androgenicity. Changes in the abundance of mRNA transcripts of endocrine-responsive genes and indicators of general chemical stress were observed after a 96-h exposure to waters from both locations. The relative levels of endocrine response, changes in gene transcript abundance, and contaminant concentrations were greater in water from the Boynton Slough site despite those effluents undergoing a more advanced treatment process. The availability of a widely geographically distributed estuarine model species (M. beryllina) now allows for improved assessment of treated effluent impacts across brackish, estuarine, and marine environments.

Land Use and Agricultural Change Dynamics in SAT Watersheds of Southern India

Impact of dynamic land use and land cover changes on the livelihood of local communities and ecosystem services is a major concern. This is particularly evident in most dryland agricultural systems in South Asia. We study land use/land cover (LULC) changes over the last two decades in a watershed (9589 ha) located in semi-arid eco-region in South India (Anantapuram district) using Landsat and IRS imagery. We captured additional data through field observations and focused group discussions. The high resolution 30 m data and the spectral matching techniques (SMTs) provided accuracy of 91–100% for various land use classes and 80–95% for the rice and groundnut areas. The watershed studied has undergone significant land use changes between 1988 and 2012. Diminishing size and number of surface water bodies, and contrastingly increased areas under irrigation clearly explain that the system has evolved significantly towards groundwater-irrigated groundnut production. Such changes could be beneficial in the short run, but if the groundwater withdrawal is without sufficient recharge, the long-term consequences on livelihoods could be negative. The water scarcity could be aggravated under the climate change. The construction of checkdams and dugout ponds to recharge groundwater is a potential solution to enhance recharge.

Detection of decreased quantities of actively spawning female Fundulus heteroclitus in tidally restricted marshes relative to restored and reference sites

Hydrologic restriction of salt marshes and subsequent invasion by Phragmites australis could influence the reproductive success of Fundulus heteroclitus, a common salt marsh resident that forages and spawns on the marsh surface at flood tide. Previous research in our laboratory using data from 2010 to 2011 examined the proportion of actively spawning F. heteroclitus residing in altered New England salt marshes as part of a larger experiment to examine the physiological condition of fish in restricted and restored marshes relative to paired unrestricted (reference) sites. We detected a significant decrease in the proportion of actively spawning fish in restricted relative to paired unrestricted marshes, but no difference between restored and paired unrestricted marsh fish. In this manuscript, we conduct a re-analysis of a portion of that data (July 2011) to explore potential mechanisms behind previous results. Using forward stepwise selection and generalized linear mixed models, we determined that the reduction in actively spawning restricted marsh fish was due to a single predictor (lipid mass); there were no effects of water temperature, body size, parasite prevalence, parasite density, and growth rate on the response. Previous results indicate healthy restricted marsh fish already have reduced energy reserves. Since investment in oocytes is energetically costly (this analysis), the effect could manifest at the population level as a reduction in actively spawning fish. In addition, oocyte quality is reduced in restricted marshes (as measured by % lipid; 13.9 ± 1.6 % SD) relative to paired unrestricted marshes (15.9 ± 2.3 % SD). Although these data are preliminary and represent a single lunar cycle, additional studies are warranted to explore relationships between P. australis invasion, restoration, and effects on the fecundity of this ubiquitous salt marsh fish.

Effect of Start of Hunting Season on Behaviour of Greylag GeeseAnser anser

Hunting is a key source of disturbance which affects geese populations directly through killing and indirectly through shooting disturbance. Movements of individuals in response to hunting disturbance may expose geese to reduced feeding opportunities and higher predation risks, which can have consequences on the population level. Thus geese should use habitats that provide access to food and minimize encounters with hunters. Our study focused on differences in the proportion of hunting-free area used and in the total area used by individuals, size of water bodies used by birds, and flight distance between roosting and feeding areas, during two periods — before and after the start of the hunting season. In south Bohemia (Czech Republic), in 2012, 2014 and 2015, we attached seventeen GPS/GSM-transmitters to moulting Greylag Geese Anser anser. We analysed data from nine transmitters, recording two or twelve logs per day, using minimum convex polygons home range estimates and Wilcoxon matched pairs test. We s...

Small lakes in big landscape: Multi-scale drivers of littoral ecosystem in alpine lakes

In low nutrient alpine lakes, the littoral zone is the most productive part of the ecosystem, and it is a biodiversity hotspot. It is not entirely clear how the scale and physical heterogeneity of surrounding catchment, its ecological composition, and larger landscape gradients work together to sustain littoral communities.A total of 113 alpine lakes from the central Pyrenees were surveyed to evaluate the functional connectivity between littoral zoobenthos and landscape physical and ecological elements at geographical, catchment and local scales, and to ascertain how they affect the formation of littoral communities. At each lake, the zoobenthic composition was assessed together with geolocation, catchment hydrodynamics, geomorphology and topography, riparian vegetation composition, the presence of trout and frogs, water pH and conductivity.Multidimensional fuzzy set models integrating benthic biota and environmental variables revealed that at geographical scale, longitude unexpectedly surpassed altitude and latitude in its effect on littoral ecosystem. This reflects a sharp transition between Atlantic and Mediterranean climates and suggests a potentially high horizontal vulnerability to climate change. Topography (controlling catchment type, snow coverage and lakes connectivity) was the most influential catchment-scale driver, followed by hydrodynamics (waterbody size, type and volume of inflow/outflow). Locally, riparian plant composition significantly related to littoral community structure, richness and diversity. These variables, directly and indirectly, create habitats for aquatic and terrestrial stages of invertebrates, and control nutrient and water cycles. Three benthic associations characterised distinct lakes. Vertebrate predation, water conductivity and pH had no major influence on littoral taxa.This work provides exhaustive information from relatively pristine sites, and unveils a strong connection between littoral ecosystem and catchment heterogeneity at scales beyond the local environment. This underpins the role of alpine lakes as sensors of local and large-scale environmental changes, which can be used in monitoring networks to evaluate further impacts.

On the variability of the Priestley‐Taylor coefficient over water bodies

AbstractDeviations in the Priestley‐Taylor (PT) coefficient αPT from its accepted 1.26 value are analyzed over large lakes, reservoirs, and wetlands where stomatal or soil controls are minimal or absent. The data sets feature wide variations in water body sizes and climatic conditions. Neither surface temperature nor sensible heat flux variations alone, which proved successful in characterizing αPT variations over some crops, explain measured deviations in αPT over water. It is shown that the relative transport efficiency of turbulent heat and water vapor is key to explaining variations in αPT over water surfaces, thereby offering a new perspective over the concept of minimal advection or entrainment introduced by PT. Methods that allow the determination of αPT based on low‐frequency sampling (i.e., 0.1 Hz) are then developed and tested, which are usable with standard meteorological sensors that filter some but not all turbulent fluctuations. Using approximations to the Gram determinant inequality, the relative transport efficiency is derived as a function of the correlation coefficient between temperature and water vapor concentration fluctuations (RTq). The proposed approach reasonably explains the measured deviations from the conventional αPT = 1.26 value even when RTq is determined from air temperature and water vapor concentration time series that are Gaussian‐filtered and subsampled to a cutoff frequency of 0.1 Hz. Because over water bodies, RTq deviations from unity are often associated with advection and/or entrainment, linkages between αPT and RTq offer both a diagnostic approach to assess their significance and a prognostic approach to correct the 1.26 value when using routine meteorological measurements of temperature and humidity.

Classification efficiency of the B-IBI comparing water body size classes in Chesapeake Bay

The Benthic Index of Biotic Integrity (B-IBI) was developed and is currently employed for environmental assessment in Chesapeake Bay. The index consists of a variety of benthic community metrics (e.g. abundance, biomass, diversity, stress tolerance groups, etc.) scored by thresholds applied to seven benthic community habitats (tidal freshwater, oligohaline, low mesohaline, high mesohaline mud, high mesohaline sand, polyhaline mud, and polyhaline sand) This index was verified as being a sensitive and robust tool for summarizing the status of benthic communities. In our study we tested the classification efficiency of the index using new benthic data by characterizing each sample a priori as degraded or undegraded using criteria of sediment contaminant levels, bioassays and bottom dissolved oxygen levels. A primary objective of our study was to test the classification efficiency of the B-IBI in small water bodies connected to larger water bodies of the mainstems of the large rivers of Chesapeake Bay, as well as the efficiency of the index over time (1990 through 2009). The B-IBI was affected by the size of the water body, e.g., index accuracy was higher for water bodies in small watersheds in lower salinity habitats, whereas large water bodies of the mainstem of rivers were better classified by the B-IBI in habitats with higher salinities. Across the seven benthic habitat types overall correct classification was moderate to low and lower for correctly classifying undegraded sites. In general the index metrics showed some deficiencies that suggest improvements could be made by recalibrating existing metric thresholds or selecting new suitable metrics.

A Multifactorial GIS-Based Analytical Method to Determine the Quality of Urban Green Space and Water Bodies

The type, size, and spatial distribution of public green spaces and water bodies are key factors for the microclimatic quality of urban areas, particularly within densely built-up districts, where they influence the quality of life. The analytical method presented in this paper looks at entire cities in a GIS-based approach that identifies potential critical areas of the city (with regard to heat stress or the accessability of green spaces) and quantifies their size and location in relation to green space and water bodies. The advantage of this method is that analysing the urban environment can be largely automated by the use of available geo base data. This requires the application of algorithms from the field of landscape ecology to the urban environment. The method is based on multifactorial evaluation. Comparisons between cities are made possible by extremum normalisation. Densely built-up areas as well as all green spaces and water bodies within settlements are quantified in the form of areal indicators. Thus the proximity of densely built-up areas to green space or water bodies is measured by the indicator “Euclidian distance.” By correlating the resulting potential heat islands with population data from the 2011 National Census, it is possible to determine the likely number of residents affected. The method presented, which has been tested on seven cities in Germany, is part of a wide-ranging investigation into urban densities aimed at improving efficiency and environmental quality.

Genetic diversity and temporal dynamics of phytoplankton viruses in East Lake, China.

Phytoplankton viruses are important components of aquatic ecosystems. However, their prevalence and genetic diversity in marine and freshwater systems are largely under estimated owing to the immense size of water bodies and limitations in virus discovery techniques. In this study, we conducted a 1-year survey of phytoplankton virus communities by collecting surface water monthly from an inland lake (East Lake) in China between May 2012 and April 2013. We examined four phytoplankton viruses, i.e., myoviruses, podoviruses, siphoviruses, and phycodnaviruses, and seven sets of primers were used to target conserved genes within these four species. In this year-long investigation, a total of 358 different virus-related sequences from four virus families were obtained. All virus families were detected in all months, except for cyanopodoviruses, which were only identified during eight of the 12 months surveyed. Moreover, virus abundance and diversity changed dynamically over time. Phylogenetic analysis revealed that the majority of viral sequences from East Lake, China displayed distinct clustering patterns compared with published sequences. These results supported the existence of a highly diverse and unique phytoplankton virus community in East Lake, China.

Organic Carbon Burial in Lakes and Reservoirs of the Conterminous United States.

Organic carbon (OC) burial in lacustrine sediments represents an important sink in the global carbon cycle; however, large-scale OC burial rates are poorly constrained, primarily because of the sparseness of available data sets. Here we present an analysis of OC burial rates in water bodies of the conterminous U.S. (CONUS) that takes advantage of recently developed national-scale data sets on reservoir sedimentation rates, sediment OC concentrations, lake OC burial rates, and water body distributions. We relate these data to basin characteristics and land use in a geostatistical analysis to develop an empirical model of OC burial in water bodies of the CONUS. Our results indicate that CONUS water bodies sequester 20.8 (95% CI: 9.4-65.8) Tg C yr(-1), and spatial patterns in OC burial are strongly influenced by water body type, size, and abundance; land use; and soil and vegetation characteristics in surrounding areas. Carbon burial is greatest in the central and southeastern regions of the CONUS, where cultivation and an abundance of small water bodies enhance accumulation of sediment and OC in aquatic environments.

Patterns of occurrence and abundance of roosting geese: the role of spatial scale for site selection and consequences for conservation

AbstractRoosting site selection by geese is a key factor for survival during migration and wintering. Birds should select sites that minimize thermoregulation demands and predation risk, and maximize foraging efficiency. We used data on the spatial location of geese roosting sites in Poland to compare landscape features and the conservation status of roosting and non‐roosting sites at different scales ranging from 5 to 50 km. Logistic regression revealed that the sites selected by geese had larger waterbody size than non‐selected sites, and surrounded by a smaller coverage of woodland at the scale of 50 km. They also were more often Natura 2000 sites. The most important factors positively affecting the abundance of geese were the size of waterbody and low coverage of artificial area (mostly urban) within a 50 km radius. Several further factors also influenced the roosting site selection. Regardless to the scale a large coverage of farmland (mostly rapeseed) positively affected roosting geese whereas forest coverage had a negative effect. Spatial hierarchical clustering analysis showed that the roosting sites were densely located in regions characterized by the most intensive agriculture. Farming intensity therefore seems to increase the abundance of geese, and consequently, to increase a possible conflict between goose conservation and food production. To alleviate the conflicts we delineated areas that may be most affected and where the conservation measures should be implemented first. As geese respond to environmental factors at different spatial scales this scale‐dependency should be included in the conservation and management of goose populations.

Assessing aquatic biodiversity of zooplankton communities in an urban landscape

Aquatic ecosystems are common in urban environments. A solid understanding of aquatic species’ distributions in urban habitats will both advance urban ecology and preserve biodiversity in cities. In particular, zooplankton are central components of aquatic food webs and their biodiversity patterns thus warrant further characterization and understanding. We examined sources of variation and biodiversity patterns of zooplankton communities across eighteen waterbodies in the urban landscape of Canada’s large island city of Montreal. We report a total of 80 zooplankton taxa of which rotifers and cladocerans were major contributing taxa to biodiversity. We found a lack of agreement between contributions of individual waterbodies to rotifer and cladoceran beta diversity. Littoral vegetated zones proved to be important habitats for zooplankton biodiversity, contributing considerably to the species richness pool, often with a different species composition. Further variation in zooplankton community composition was attributable to local factors such as waterbody size, algal biomass and composition, and macroinvertebrate predators, but also to urban management practices such as waterbody draining during winter. We show that urban waterbodies can represent important reservoirs of biodiversity. Management practices favoring a large diversity of permanent and temporary habitats with littoral vegetated zones should be incorporated in urban design and conservation plans.

Functional phytoplankton distribution in hypertrophic systems across water body size

Distribution of algae was studied in a series of water bodies ranging from 10−2 to ~109 m2 in the lowland region of the Carpathian basin in a late summer period. It has been demonstrated that lake size has pronounced impact on the morphological and chemical properties of the water bodies, and acting through these variables it shapes the distribution of the various algal groups in the water bodies of different sizes. Changes of the relative abundance of the various algal groups along the spatial scale showed four apparently distinct patterns. We found increasing relative abundance of heterocytic cyanobacteria, dinoflagellates and those taxa which have no capability of active locomotion and are characterised by high sinking rate in the large water bodies. The flagellated algae (Chlamydomonas spp., euglenophytes, Synura spp.) and the tichoplanktonic elements were characteristic for small-sized water bodies. Most of the chrysophytes and several other flagellated taxa showed hump-shaped distribution along the size scale of water bodies. The group of large colonial flagellated chlorophytes, non-heterocytic filamentous cyanobacteria and filamentous chlorophytes occasionally occurred in high relative abundance both in small and large-sized water bodies. Our findings suggest that water body size has pronounced impact on the composition of algal assemblages.

Understanding urban wetland dynamics: cross-scale detection and analysis of remote sensing

This study aimed to detect and understand remotely sensed urban wetland dynamics as a sensitive indicator of the combined effects of human disturbances and climate impacts in the course of global change. To address this objective, the study developed technical approaches to detect and interpret wetland changes across spatial scales in complex urban landscapes. Using a series of Satellite Pour l’Observation de la Terre (SPOT) images covering 1992–2010, the study was conducted in the Kansas City metropolitan area of the USA, which has experienced significant urban sprawl in recent decades. As a fine-tuning of the traditional supervised image classification, a knowledge-based classification algorithm was developed to identify fine-scale, hidden wetlands that cannot be appropriately detected based on their spectral differentiability. The analyses of wetland change were implemented at the metropolitan, watershed, and sub-watershed scales as well as being based on the size of surface water bodies in order to reveal real pictures of urban wetland change trends in relation to major driving factors. The results of the study indicated that the knowledge-based classification approach improved the detection capability and accuracy of urban wetlands by fine-tuning the traditional classification results. The cross-scale analysis of detected land covers revealed that wetland dynamics varied in trend and magnitude from metropolitan, watersheds, to sub-watershed scales. The study found that increased precipitation swelled wetlands, which inflated the findings of remotely sensed wetland cover and related trend interpretation. During an 18 year study period, human development activities in the study area resulted in a large increase in impervious surfaces, which was mainly at the expense of farmland/grassland areas and some small wetlands in all urban watersheds. In contrast, increased precipitation in the region swelled large wetlands in particular. This mixed picture of urban wetland dynamics, associated with the analysis of underlying driving factors, provides a new baseline for relevant urban planning, management, and research in a global change perspective.

Effects of temperature, body size, and starvation on feeding in a major echinoderm predator

The common sea star, Asterias rubens, is a major predator in rocky subtidal ecosystems in the northern Gulf of St. Lawrence and along the Atlantic coasts of Nova Scotia and Newfoundland, Canada. We carried out two laboratory experiments to test the effects of water temperature, starvation, and body size, on mussel (Mytilus edulis) consumption and size selection in A. rubens from southeastern Newfoundland. Experiment 1 examined rates of consumption of medium (15–30 mm) mussels by small (9–15 cm) sea stars fed or starved moderately (for 3 weeks) at three temperatures representative of late summer highs (8, 11, and 15 °C) and one temperature representative of late winter lows (2 °C). Temperature and starvation did not affect consumption in summer, which was two times higher than in winter. Starvation also did not affect consumption in winter. Experiment 2 examined consumption of small (5–15 mm), medium, and large (30–45 mm) mussels by small and large (25–30 cm) sea stars fed or starved moderately or severely (for 6 weeks). Small sea stars consumed similar proportions of mussels regardless of starvation. However, large, moderately starved sea stars consumed at least two times more mussels than large, fed and large, severely starved individuals, indicating that the need to feed after a short starvation was higher in large than small A. rubens. Consumption of small, medium, and large mussels was, respectively, affected by the sea star’s size only, size and starvation independently, and size and starvation interactively. Collectively, our findings indicate that starvation, body size, and their interaction are key modulators of feeding in A. rubens, while suggesting that feeding is adaptable to thermal conditions. They also speak of the importance of considering the interplay between organismal traits and ongoing changes in ocean climate to better predict causes and consequences of alterations in predator–prey interactions.