The ecology of European ponds: defining the characteristics of a neglected freshwater habitat

There is growing awareness in Europe of the importance of ponds, and increasing understanding of the contribution they make to aquatic biodiversity and catchment functions. Collectively, they support considerably more species, and specifically more scarce species, than other freshwater waterbody types. Ponds create links (or stepping stones) between existing aquatic habitats, but also provide ecosystem services such as nutrient interception, hydrological regulation, etc. In addition, ponds are powerful model systems for studies in ecology, evolutionary biology and conservation biology, and can be used as sentinel systems in the monitoring of global change. Ponds have begun to receive greater protection, particularly in the Mediterranean regions of Europe, as a result of the identification of Mediterranean temporary ponds as a priority in the EU Habitats Directive. Despite this, they remain excluded from the provisions of the Water Framework Directive, even though this is intended to ensure the good status of all waters. There is now a need to strengthen, develop and coordinate existing initiatives, and to build a common framework in order to establish a sound scientific and practical basis for pond conservation in Europe. The articles presented in this issue are intended to explore scientific problems to be solved in order to increase the understanding and the protection of ponds, to highlight those aspects of pond ecology that are relevant to freshwater science, and to bring out research areas which are likely to prove fruitful for further investigation. Guest editors: R. Céréghino, J. Biggs, B. Oertli and S. Declerck The ecology of European ponds: defining the characteristics of a neglected freshwater habitat     

Seasonal patterns of carbohydrate translocation and synthesis of structural carbon components in <Emphasis Type="Italic">Typha angustifolia</Emphasis>

Quantitative studies of material budgets and resource allocation patterns of emergent plants are needed to fully understand nutrient and carbon cycling in wetlands. Whole-plant translocation patterns of nonstructural carbohydrates and synthesis of structural carbon were documented using two (shallow and deepwater) populations of Typha angustifolia in floodplain habitats of the Arakawa River, Japan. Monthly and bimonthly measurements of the concentrations of total carbon, non-structural carbohydrates, and water-soluble carbohydrates, as well as, estimates of standing stocks of aboveground (AG) and belowground (BG) biomass for both populations from 2002 to 2004 are described here. Annual patterns of carbon gain, rates of carbohydrate translocation between AG and BG organs, and rates of synthesis of structural carbon were estimated. Upward translocation supported all AG production for approximately 30 days. Afterward, the fraction of AG production supported by upward translocation decreased linearly with time, and completely diminished by Day 80 (counted from first day of growth; March 15). At Day 80, material translocation was directed downward and the percentage of downward translocation relative to AG net production increased until Day 170; there was a vigorous increase in downward translocation prior to senescence. In early summer (Day 80–110), more than half of the translocated materials were transformed into structural components, but by Day 125 only 30% was synthesized into total structural carbohydrates. Prior to senescence, there was a greater percentage of nonstructural carbohydrates in the rhizomes. Across the growing season (Day 60–153), the total amount of downward translocation was found to be proportional to AG production and the quantitative evaluation of the carbon budget shed further insight into the translocation process of this rhizomatous aquatic plants. In addition, insights on the differences between shallow and deepwater populations were gained. Especially, the deepwater population supported a higher fraction of vertical rhizomes compared to individuals sampled from the shallow water population. Handling editor: S. M. Thomaz.     

Sawgrass (Cladium jamaicense) responses as early indicators of low-level phosphorus enrichment in the Florida Everglades

Anthropogenic phosphorus (P) inputs to the Florida Everglades have produced dramatic changes in the wetland vegetation of this otherwise oligotrophic system. While the proliferation of undesirable plant species in response to enrichment has been well documented, nutrient-related changes in the physiological and morphological attributes of existing vegetation, prior to any shifts in species composition or changes in the spatial extent of certain taxa, have yet to be adequately characterized. In this experiment, three sawgrass-dominated areas were enriched with P for 3 years at rates of 0.4 g P/m²/year (HP), 0.1 g P/m²/year (LP), or 0 g P/m²/year (controls) to assess potential impacts of P-enriched discharges from stormwater treatment areas into the Everglades. Elevated concentrations of TP in rhizomes and leaves and reduced ratios of leaf N:P were detected in HP plants within ~1 year at most sites. Live leaf densities, plant heights, and plant densities of the HP groups were generally higher than LP and control groups after 2 years, a pattern that was evident even after major fire events. Total aboveground biomass was significantly elevated in both HP and LP treatments at two of the three sites after 3 years. No change in species composition was detected during the study. Planned hydrologic restoration measures will increase P loads into parts of the Everglades that have not previously experienced anthropogenic P enrichment. Monitoring native vegetation such as sawgrass can be a sensitive and relatively robust means of detecting unintended P enrichment in these areas prior to shifts in vegetation community composition or changes in area cover of key species.     

Wetlands and global climate change: the role of wetland restoration in a changing world

Global climate change is recognized as a threat to species survival and the health of natural systems. Scientists worldwide are looking at the ecological and hydrological impacts resulting from climate change. Climate change will make future efforts to restore and manage wetlands more complex. Wetland systems are vulnerable to changes in quantity and quality of their water supply, and it is expected that climate change will have a pronounced effect on wetlands through alterations in hydrological regimes with great global variability. Wetland habitat responses to climate change and the implications for restoration will be realized differently on a regional and mega-watershed level, making it important to recognize that specific restoration and management plans will require examination by habitat. Floodplains, mangroves, seagrasses, saltmarshes, arctic wetlands, peatlands, freshwater marshes and forests are very diverse habitats, with different stressors and hence different management and restoration techniques are needed. The Sundarban (Bangladesh and India), Mekong river delta (Vietnam), and southern Ontario (Canada) are examples of major wetland complexes where the effects of climate change are evolving in different ways. Thus, successful long term restoration and management of these systems will hinge on how we choose to respond to the effects of climate change. How will we choose priorities for restoration and research? Will enough water be available to rehabilitate currently damaged, water-starved wetland ecosystems? This is a policy paper originally produced at the request of the Ramsar Convention on Wetlands and incorporates opinion, interpretation and scientific-based arguments.     

Irrigators’ attitudes towards environmental flows for wetlands in the Murrumbidgee, Australia

In Australia and many countries worldwide environmental flows are becoming an increasingly popular tool for reducing the negative impacts of river regulation. However, there are many factors that restrict the effectiveness of these flows such as thermal pollution, existing physical infrastructure and the limited volume of water available. Since environmental flows result in reduced water allocations for irrigators, the aim of the present study was to investigate whether irrigators’ attitudes towards environmental flows for wetlands are influenced by the effectiveness of these flows. Three focus groups were used to engage with farmers in the Murrumbidgee Catchment, eastern Australia. A simulation model of the Murrumbidgee River was created to provide focus groups with a tool for examining the effectiveness of wetland-watering releases and exploring alternative management scenarios. The results showed that participants support the principle of environmental flows for wetlands. However, they believed that the flows could be more effective if the restrictions imposed by physical infrastructure were removed. They also suggested that the volume of translucency releases should be lowered, as these flows reduce the amount of water available for wetlands and lower early season allocations for general-security water users. The participants provided numerous suggestions for altering the management of water resources so that both the Mid Murrumbidgee Wetlands and farmers would benefit.

Application of a multi-cylinder evapotranspirometer method for evapotranspiration measurements in wetlands

This paper introduces a multi-cylinder evapotranspirometer method, which can directly measure evapotranspiration (ET) from emergent plants in different species and states as well as simultaneously measure evaporation (E_W) from an open water surface. Values of daily ET from three contrasting reed (Phragmites australis) stands, with different leaf area indexes (LAI), were obtained through in situ measurements of the Baiyangdian wetland using this method during the growing seasons in 2008 and 2009. The results showed that the ET rate of the reed belt was very high, even exceeding 20 mm d⁻¹ under extreme weather conditions. Depending on the LAI change, the annual ET from the different reed canopies ranged from 970 to 2035 mm, whereas the ET/E_W ratios ranged from 2.05 to 3.98. Accuracy analysis results showed that the errors of the measurement from this method were no more than 2 mm. The relative errors of the measurement were correspondingly from 0.04% to 0.33%. It is indicated that the accuracy of our measurement is good enough for the requirements of the ET measurement.     

Coastal Wetlands Planning, Protection, and Restoration Act: A programmatic application of adaptive management

The Coastal Wetlands Planning, Protection, and Restoration Act (CWPPRA), commonly referred to as ‘The Breaux Act’, has provided some of the resources necessary to begin implementing a comprehensive, large-scale, long-term coastal wetland restoration program for Louisiana USA. Due to the dynamic nature of this ecosystem and the uncertainty associated with large-scale restoration, adaptive management principles were embedded throughout CWPPRA’s organizational structure, planning process, project implementation, and monitoring program to facilitate achieving the mandates associated with the Breaux Act. Feedback loops were established within and between each of the programmatic components to encourage continuous learning, which is central to adaptive management. The knowledge gained has led to institutionalized change in projects as well as the program. This paper describes how the formation of the CWPPRA Task Force and associated committees and groups resulted in an integrated coast-wide process for planning, selection, construction, operation, maintenance, monitoring, and scientific evaluation of 84 restoration projects implemented or scheduled for implementation throughout coastal Louisiana.     

Temporal variability in the way local habitat affects duck population growth

Climate change is expected to lead to greater temporal climatic variability across broad spatial extents. A potential consequence is that shifts in climatic conditions might alter how local habitat affects the population growth of animals dependent on those habitats for at least part of their life cycle. We tested whether such a phenomenon occurred when the North American Prairie Pothole Region transitioned through periods of wet and dry conditions by modeling the population growth of seven duck species over 52 years (1961–2012). We found that the influence of local habitat quality—indexed by wetland availability—on duck population growth varied in magnitude and direction on an annual basis. While the effect of wetlands was relatively small in most years, there were some years in which wetlands strongly affected duck population growth in both positive and negative directions (e.g., negative in 2002 and positive in 2008). Contrary to our expectation, inter-annual variability in the effect of wetlands on duck population growth did not depend on regional precipitation. We also found that for two species—American Wigeon (Anas americana) and Green-winged Teal (A. carolinensis)—duck population growth in the presence of wetlands rarely differed from what would be expected solely under density dependence. Our study is the first to demonstrate that the effect of local habitat on population growth varies over time even if the cause of that variation remains unexplained. Consequently, any study that attempts to identify a species’ critical habitat using time series abundance data must consider that local relationships are non-stationary. More complicated measures of climate change may reveal how local drivers of population growth depend on broader temporal climatic patterns.     

Impacts of hydroperiod on growth and survival of larval amphibians in temporary ponds of Central Pennsylvania,USA

The effects of variable hydroperiod (three levels) and initial density of amphibians (two levels) on survival, growth rate, and time to and mass at metamorphosis were studied for wood frogs (Rana sylvatica), Jefferson salamanders (Ambystoma jeffersonianum), and spotted salamanders (A. maculatum). Experiments were carried out in 260-1 mesocosms set up outdoors in a forest. These pond simulations were designed to mimic conditions that occur in palustrine temporary wetlands in central Pennsylvania. No animals reached metamorphosis in the short hydroperiod (56 days). However a greater proportion (66%) of tadpoles of R. sylvatica survived to the end of the 56-day, treatment than the 84- or 158-day treatments (29 and 14%, respectively), from which all survivors metamorphosed. In contrast, neither of the salamanders metamorphosed by 84 days; survival to metamorphosis at 158 days was 15% for A. jeffersonianum and 10% for A. maculatum. Average instantaneous growth rates for A. jeffersonianum decreased with each increase in hydroperiod. Growth of R. sylvatica was greater in the 56-day hydroperiod than in hydroperiods of 84 or 158 days. Initial amphibian density had no effect on growth or survival of any species. It appears that salamander larvae were predatory on tadpoles, since survival of R. sylvatica was negatively correlated with survival of A. jeffersonianum in 84-day treatments and with growth of A. maculatum in 158-day treatments.