Rotifer occurrence in relation to water temperature in Loch Leven,Scotland

Many rotifer species in Loch Leven show a distinct seasonality in occurrence. This appears to be primarily an effect of temperature. While some species seem to be eurythermal, other species show a well-defined range of temperature preference, outside which they are unable to maintain populations. Within this range, there is a close correlation between food availability and rotifer abundance.     

Multi-species patterns of avian cholera mortality in Nebraska's Rainwater Basin

Nebraska's Rainwater Basin (RWB) is a key spring migration area for millions of waterfowl and other avian species. Avian cholera has been endemic in the RWB since the 1970s and in some years tens of thousands of waterfowl have died from the disease. We evaluated patterns of avian cholera mortality in waterfowl species using the RWB during the last quarter of the 20th century. Mortality patterns changed between the years before (1976-1988) and coincident with (1989-1999) the dramatic increases in lesser snow goose abundance and mortality. Lesser snow geese (Chen caerulescens caerulescens) have commonly been associated with mortality events in the RWB and are known to carry virulent strains of Pasteurella multocida, the agent causing avian cholera. Lesser snow geese appeared to be the species most affected by avian cholera during 1989-1999; however, mortality in several other waterfowl species was positively correlated with lesser snow goose mortality. Coincident with increased lesser snow goose mortality, spring avian cholera outbreaks were detected earlier and ended earlier compared to 1976-1988. Dense concentrations of lesser snow geese may facilitate intraspecific disease transmission through bird-to-bird contact and wetland contamination. Rates of interspecific avian cholera transmission within the waterfowl community, however, are difficult to determine.     

Avian cholera in waterfowl in Saskatchewan, spring 1977.

Avian cholera was diagnosed in lesser snow geese (Anser c. caerulescens), Ross' geese (Anser rossii) and individuals of several other waterfowl species in a small area of south-western Saskatchewan over a 1 month period during the 1977 spring migration. Approximately 250 dead birds were found. This is apparently the first time avian cholera has been reported in migrating waterfowl in Canada. The site of the mortality was midway between the wintering and nesting areas of the two principal species, and the significance of the occurrence of the disease this far north is discussed.     

Spectral intensity in some Scottish freshwater lochs

In the course of investigations on the ecology of submerged aquatic macrophytes a narrow-bandwidth spectroradiometer has been used to measure underwater spectral intensity (390–750 nm) in a series of lochs approaching the extremes in optical and chemical properties of Scottish fresh waters. Cosine response and immersion-effect properties of the collector were determined in the laboratory with a colUmated hght source. Diffuse attenuation coefficients, Ee, ranged from 0·55 in Loch Croispol, a calcareous loch, to 2·9 in Loch Leven, a lowland eutrophic loch. Underwater spectral intensity (1 m) relative to subsurface values show a proportional increase in short-wave radiation in the blue-green water of Loch Croispol, while the converse is true of the peaty brown water of Loch Uanagan. Attenuation coefficients were derived over 25 nm wavebands in Lochs Croispol, Leven and Uanagan. The water in the latter two lochs is optically similar although Leven is rich in phytopiankton and has an extinction peak at 675 nm. Uanagan represents the brown-water type of loch most common in Scotland. Loch Croispol has attenuation coefficients for shorter wave-lengths at least ten times lower than the other two lochs and only approaches their values at 750 nm. Croispol resembles Crater Lake, Oregon. The colour range at the maximum colonizable depths by rooted macrophytes of brown (Uanagan 4 m) to blue-green (Croispol 6 m) water is equivalent to 196·0 and 230·6 kJ/Einstein (48·2 and 55·6 kcal/Einstein). Red/far-red ratios even in plankton-rich water (Leven) were at least three times the value for sunlight (1·3) and within the total photic zone reached three-figure proportions. Possible implications for light-sensitive seeds of aquatic species and for morphogenesis and zonation are discussed.     

Community Structure of Wetland Birds During Spring Migration Through the Rainwater Basin

Abstract: Staging areas and migratory stopovers of wetland birds have the potential to function as geographic bottlenecks; entire populations within a flyway may be affected by the quality and quantity of available wetland habitat at stopover sites. Although approximately 90% of playa wetlands in the Rainwater Basin (RWB) region of south-central Nebraska, USA, have been destroyed, the area still provides essential stopover habitat for >10 million waterfowl each spring. We evaluated community patterns and species associations to assess importance of assembly rules in structuring wetland bird communities during migration and to better facilitate multispecies conservation and management strategies. We surveyed 36–40 playas twice weekly in the RWB and observed approximately 2.6 million individual migratory wetland birds representing 72 species during 3 spring migrations 2002–2004. We evaluated spatial and temporal species co-occurrence patterns of geese, dabbling ducks, diving ducks, and shorebirds using null model analysis. Goose species co-occurrence scores did not differ from random in any year of the study, suggesting that goose species frequently use the same habitats during migration. Co-occurrence patterns among dabbling ducks were not different than expected by chance in any year; however, when we evaluated co-occurrence at a weekly scale, dabbling ducks co-occurred less often than expected during weeks of peak migration (high abundance), indicating that dabbling duck species spatially segregated at high densities. Diving duck co-occurrence patterns did not differ from random in any year, suggesting that diving duck species used the same habitats during migration. Shorebird species co-occurred less often than expected in 2002 and 2004, and during weeks of high shorebird abundance, indicating that shorebird communities were distinctly structured during those times. Most association values among lesser snow geese (Chen caerulescens) and dabbling duck species were positive, indicating dabbling ducks did not avoid wetlands with snow geese, a concern for waterfowl managers. However, we frequently observed snow geese and dabbling ducks using different microhabitats within a wetland, which indicate species associations and co-occurrence patterns may have occurred at a finer spatial scale than we measured. This approach of co-occurrence analysis will allow wildlife managers charged with multispecies management at migration stopover sites to make informed conservation and management decisions based on community structure rather than historic single-species approaches.     

New species records and changes in abundance of waterfowl in northwest Greenland

Breeding populations of Nearctic and Palearctic waterfowl have undergone significant changes in abundance and distribution over the past 50 years. The Avanersuaq District in northwest Greenland is home to an assemblage of waterfowl from both geographic areas; however, minimal historic or current information is available on species abundance. In 2008 and 2009, we conducted field surveys in Greenland from 76.00° to 77.35°N for breeding and non-breeding waterfowl and have collected anecdotal field notes of avian observations over a 20-year period (1993–2012). During these periods, we documented the first observation of a Ross’s goose (Chen rossii) and the first confirmed breeding by lesser snow geese (Chen caerulescens caerulescens) in Greenland. Northern pintails (Anas acuta) were observed for the first time in northwest Greenland, and a previously unknown breeding location for brent geese (Branta bernicla hrota) was also identified. Local populations of greater snow (C. c.) and Canada geese (B. canadensis) have increased in size. The Booth Sound and Drown Bay wetland areas and many islands throughout the Avanersuaq District were identified as critical habitat for both breeding and non-breeding waterfowl. Further increases in waterfowl abundance, including more frequent rare and new visitors, are likely in the study area as breeding populations further south continue to increase and an ameliorating climate allows for a longer breeding season. These results will prove useful as a baseline for comparisons with future surveys.     

Changes in nutrient dynamics of midcontinent greater white-fronted geese during spring migration

Waterfowl and other migratory birds commonly store nutrients at traditional staging areas during spring for later use during migration and reproduction. We investigated nutrient-storage dynamics in the midcontinent population of greater white-fronted geese (Anser albifrons; hereafter white-fronted geese) at spring staging sites in the Rainwater Basin of Nebraska during February–April and in southern Saskatchewan during April–May, 1998 and 1999. In Nebraska, lipid content of white-fronted geese did not increase, and protein content changed little over time for most age and sex categories. In Saskatchewan, lipids increased 11.4 g/day (SE = 1.7) and protein content increased 1.6 g/day (SE = 0.6) in the sample of adult geese collected over a 3-week period. A study conducted during 1979–1980 in the Rainwater Basin reported that white-fronted geese gained 8.8–17.7 g of lipids per day during spring, differing greatly from our results 2 decades later. In addition, lipid levels were less in the 1990s compared to spring 1980 for adult geese nearing departure from staging sites in Saskatchewan. This shift in where geese acquired nutrient stores from Nebraska to more northern staging sites coincided with a decrease in availability of waste corn in Nebraska, their primary food source while staging at that stopover site, and an increase in cultivation of high-energy pulse crops in Saskatchewan. White-fronted geese exhibited flexibility in nutrient dynamics during spring migration, likely in response to landscape-level variation in food availability caused by changes in agricultural trends and practices. Maintaining a wide distribution of wetlands in the Great Plains may allow spring-staging waterfowl to disperse across the region and facilitate access to high-energy foods over a larger cropland base. © 2011 The Wildlife Society.     

A history of scientific research at Loch Leven,Kinross, Scotland

Loch Leven is a large, shallow lake in lowland Scotland, UK. Scientific research began here almost 200 years ago. Early research characterised the biodiversity and physical characteristics of the loch, providing an important historical background for future research. In the mid-1960s, this ad hoc approach was superseded by a more structured research programme under the umbrella of the International Biological Programme. This was the beginning of the Loch Leven long-term monitoring programme. Today, the results of these studies form one of the longest and most comprehensive limnological datasets for shallow freshwater lakes in the world, comprising more than 500 physical, chemical and biological variables collected at two-weekly intervals. To celebrate the 40th anniversary of the start of the long term monitoring programme, and to highlight the scientific investigations still being conducted at Loch Leven, the NERC Centre for Ecology & Hydrology (CEH) organised a symposium entitled “Loch Leven: 40 years of scientific research” in Kinross, Scotland, UK, on 11 December 2008. This examined the role of long-term monitoring in developing our understanding of the links between pollution, climate change and ecological responses in shallow lakes. This article introduces a series of papers summarising the scientific results presented at this meeting.     

The relationship between Trichocerca pusilla (Jennings), Aulacoseira spp. and water temperature in Loch Leven,Scotland, U.K.

Loch Leven is a shallow, eutrophic lake in the Scottish lowlands that is famous for its brown trout (Salmo trutta L.) fishery. Studies of planktonic rotifer populations began here in January 1977. Since then, samples have been collected and analysed at more or less weekly intervals. Additional information on the composition and abundance of phytoplankton and crustacean zooplankton species, and on a variety of physical and chemical determinants, has been recorded on each sampling occasion.Long-term datasets, such as that described above, are invaluable for identifying interactions between components of the plankton that only appear for short periods each year, as these interactions would probably be overlooked in data spanning a shorter period of time. This study uses the long-term data from Loch Leven to examine the food and temperature requirements of the summer rotifer species Trichocerca pusilla (Lauterborn). The results suggest that T. pusilla prefers water temperatures above 12 °C and that it feeds, primarily, on the filamentous diatom Aulacoseira spp. During the summer months, its abundance was closely related to the availability of this diatom. When filaments of Aulacoseira spp. were abundant, rotifer densities reached 1000–3000 ind. l^–1 and when they were scarce (e.g. 1980, 1997 and 1998) T. pusilla densities also remained low (i.e. less than 100 ind. l^–1). The reason for the success or failure of Aulacoseira during the summer months each year is unclear but, in general, its abundance was related to the availability of dissolved silica in the water.     

Rotifer sampling — a complete species list from one visit?

This paper describes a possible method of compiling a rotifer species list for any site from a single visit. Sediment samples collected from Loch Leven on one occasion in winter were exposed to light and a range of temperature conditions in the laboratory. Resting eggs in the sediment were induced to hatch. The resultant species list was very similar to that obtained from regular plankton collections over the previous six year period.     

Mercury in waterfowl from a contaminated river in Virginia

Many bodies of water around the world are contaminated with mercury from historic industrial and mining activities or ongoing atmospheric deposition, resulting in numerous fish consumption advisories. However, concerns about mercury have only rarely led to consumption advisories on waterfowl. In contrast with fish, waterfowl frequently disperse long distances to new watersheds, so hunters and wildlife managers do not know whether waterfowl at a pristine site have spent time at a contaminated site elsewhere. We sampled tissue mercury concentrations of mallards (Anas platyrhynchos), wood ducks (Aix sponsa), and Canada geese (Branta canadensis) at a site contaminated with mercury, during the breeding and hunting seasons. We found that many mallards had bioaccumulated mercury to levels that had the potential to produce reproductive effects and exceeded consumption advisories set for fish by regulatory agencies, whereas this was true for only a few wood ducks and Canada geese. We also documented that mercury-exposed waterfowl from this contaminated site were harvested by hunters as far as 1,054 km away. Our results suggest the need for more proactive sampling of waterfowl for mercury, and likely other bioaccumulating contaminants, in order to allow hunters to make more informed choices about consumption of their harvest. © 2012 The Wildlife Society.     

Modelling changes in species’ abundance in response to projected climate change

Aim Existing climate envelope models give an indication of broad scale shifts in distribution, but do not specifically provide information on likely future population changes useful for conservation prioritization and planning. We demonstrate how these techniques can be developed to model likely future changes in absolute density and population size as a result of climate change. Location Great Britain. Methods Generalized linear models were used to model breeding densities of two northerly‐ and two southerly‐distributed bird species as a function of climate and land use. Models were built using count data from extensive national bird monitoring data and incorporated detectability to estimate absolute abundance. Projections of likely future changes in the distribution and abundance of these species were made by applying these models to projections of future climate change under two emissions scenarios. Results Models described current spatial variation in abundance for three of the four species and produced modelled current estimates of national populations that were similar to previously published estimates for all species. Climate change was projected to result in national population declines in the two northerly‐distributed species, with declines for Eurasian curlew Numenius arquata projected to be particularly severe. Conversely, the abundances of the two southerly distributed species were projected to increase nationally. Projected maps of future abundance may be used to identify priority areas for the future conservation of each species. Main conclusions The analytical methods provide a framework to make projections of impacts of climate change on species abundance, rather than simply projected range changes. Outputs may be summarized at any spatial scale, providing information to inform future conservation planning at national, regional and local scales. Results suggest that as a consequence of climate change, northerly distributed bird species in Great Britain are likely to become an increasingly high conservation priority within the UK.     

The sensitivity of phytoplankton in Loch Leven (U.K.) to changes in nutrient load and water temperature

1. Loch Leven is a shallow, eutrophic lake in Scotland, U.K. It has experienced much change over the 30 years that it has been studied; this has primarily been due to reduced nutrient loads to the lake through active catchment management. Its recovery has been slow and, therefore, we used a phytoplankton community model (PROTECH) to test its sensitivity to changing nutrient loads and water temperature.
2. PROTECH was initialized to simulate the observed phytoplankton community in 1995 and was then repeatedly run through a combination of step-wise changes in water temperature and nutrient load (two treatments were simulated for nutrient load: one changing both nitrate and phosphorus, and one changing just phosphorus). The effect on total chlorophyll- a concentration, cyanobacteria abundance and phytoplankton diversity was examined.
3. Whilst changes in temperature had little effect, variations in the nutrient load produced a range of responses. Increasing only the phosphorus load caused a large increase in Anabaena abundance and total chlorophyll- a concentration. However, the opposite response was recorded when nitrate load was changed as well, with Anabaena increasing its biomass under reduced nutrient load scenarios.
4. The key factor determining the type of response appeared to be nitrogen availability. Anabaena , a nitrogen fixer, could exploit the phosphorus resource of Loch Leven under limiting nitrogen conditions, allowing it to dominate under most of the scenarios tested apart from those supplying extra nitrogen to the lake. The model predictions agree with the observed data, which show that Anabaena continues to dominate the summer phytoplankton bloom in Loch Leven despite the considerable reduction in phosphorus supply from the catchment. This research provides a possible explanation for this.     

Invertebrate food sources for waterbirds provided by the reconstructed wetland of Nyirkai-Hany,northwestern Hungary

Detailed studies of the macroinvertebrate benthos and zooplankton communities in Loch Leven, the largest shallow lowland lake in Scotland, UK, were carried out from 1966 to 1973 as part of the International Biological Programme (IBP). The results revealed a reduction in species diversity that was attributed to increasing eutrophication. This work provides a baseline against which the response of the invertebrate communities to subsequent changes in management can be assessed. This article compares macroinvertebrate benthos and zooplankton data from the IBP study with the post-IBP era during which changes at Loch Leven included a 60% reduction in the phosphorus input from external sources and variations in fish stocking rates. Only in recent years has there been evidence of ecological recovery by the invertebrate communities: the number of macroinvertebrate and zooplankton taxa has increased (including taxa considered to be sensitive to nutrient enrichment) and invertebrate abundances have declined. These changes appear to reflect the improvements in water quality and habitat conditions at Loch Leven that have occurred as a result of the recent reduction in nutrient loads, albeit with a substantial delay before any ecological response could be detected. This time lag in recovery has important implications for assessing improvements in the ecological status of other lake systems, as is required by the EU Water Framework Directive.     

Long-term population trends in widespread British moths

The Rothamsted Insect Survey has operated a Great Britain-wide network of light-traps since 1968. From these data we estimated the first ever national abundance indices and 35-year population trends for 338 species of common macro-moths. Although the number of trap sites which run each year is not constant, there is a representative, well-distributed core of traps that have run for 15 years. The proportion of operating sites catching a species and the annual geometric mean catch of successful traps were used to provide estimates of species range and absolute abundance. T, an index of long-term population trends, was used to compare trends among species. T was not biased by trap site turnover. The percentage of species displaying significant decreases (54%) was more than double that displaying increases (22%). Species found throughout Great Britain are decreasing most rapidly in the south and especially the southeast but species with a southerly distribution are increasing. Results of a preliminary overview suggest habitat and climate change may both play a role in changing species dynamics. The existence of estimates of abundances and trends for such a large species pool opens the way for much further research, linking trends with land-use changes, climate change and inter-specific dynamics.     

Fine‐scale genetic diversity and landscape‐scale genetic structuring in three foundational bulrush species: implications for wetland revegetation

The appropriate sourcing of seeds for restoration is critical for establishing foundational plant species that support ecosystem functions and services. Genetic analyses of such species can yield insights into patterns of genetic diversity and structuring to inform seed collections. Here we document, for three foundational bulrush species, distinct genetic patterns to guide restoration of wetlands along the iconic Great Salt Lake, the largest lake in western North America. Specifically, Schoenoplectus acutus and Schoenoplectus americanus had moderate levels of site‐scale genet richness and relatively low genet richness levels within 1‐m² plots. These patterns contrast with Bolboschoenus maritimus, which had higher levels of site‐ and plot‐level genet richness, and has therefore likely experienced more recent seedling establishment. At the landscape scale, we found some evidence for genetic isolation of individuals at more remote sites (namely Fish Springs National Wildlife Refuge in the West Desert of Utah), but all species are relatively well dispersed over hundreds of kilometers, a pattern most likely to occur via avian dispersal. In our mechanistic dispersal assessment, we found abundant bulrush seeds present in waterfowl gizzards and those seeds germinated readily despite (or because of) partial digestion. Migratory waterfowl likely facilitate the broad dispersal of all species and may aid in bulrush establishment by breaking seed dormancy. These findings suggest that seeds for restoration should be collected within and among seed source sites to ensure a diverse restoration seed lot that does not disrupt gene flow patterns.     

Estimating partial observability and nonlinear climate effects on stochastic community dynamics of migratory waterfowl

1. Understanding the impact of environmental variability on migrating species requires the estimation of sequential abiotic effects in different geographic areas across the life cycle. For instance, waterfowl (ducks, geese and swans) usually breed widely dispersed throughout their breeding range and gather in large numbers in their wintering headquarters, but there is a lack of knowledge on the effects of the sequential environmental conditions experienced by migrating birds on the long-term community dynamics at their wintering sites. 2. Here, we analyse multidecadal time-series data of 10 waterfowl species wintering in the Guadalquivir Marshes (SW Spain), the single most important wintering site for waterfowl breeding in Europe. We use a multivariate state-space approach to estimate the effects of biotic interactions, local environmental forcing during winter and large-scale climate during breeding and migration on wintering multispecies abundance fluctuations, while accounting for partial observability (observation error and missing data) in both population and environmental data. 3. The joint effect of local weather and large-scale climate explained 31·6% of variance at the community level, while the variability explained by interspecific interactions was negligible (<5%). In general, abiotic conditions during winter prevailed over conditions experienced during breeding and migration. Across species, a pervasive and coherent nonlinear signal of environmental variability on population dynamics suggests weaker forcing at extreme values of abiotic variables. 4. Modelling missing observations through data augmentation increased the estimated magnitude of environmental forcing by an average 30·1% and reduced the impact of stochasticity by 39·3% when accounting for observation error. Interestingly however, the impact of environmental forcing on community dynamics was underestimated by an average 15·3% and environmental stochasticity overestimated by 14·1% when ignoring both observation error and data augmentation. 5. These results provide a salient example of sequential multiscale environmental forcing in a major migratory bird community, which suggests a demographic link between the breeding and wintering grounds operating through nonlinear environmental effects. Remarkably, this study highlights that modelling observation error in the environmental covariates of an ecological model can be proportionally more important than modelling this source of variance in the population data.     

Explaining co-occurrence among helminth species of lesser snow geese (Chen caerulescens) during their winter and spring migration

The digestive tracts of 771 lesser snow geese (Chen caerulescens) collected from January to May 1983 from 12 locations (27 samples) were examined for helminth parasites to determine whether parasite species present in wintering geese or in spring migrants occurred independently of each other. Nine helminth species were identified. Seven had mean prevalences >5% and were the focus of this study. Six of those species were waterfowl generalists, one was a goose specialist. Our primary objective was to assess the potential contribution of factors, other than species interactions, in determining patterns of co-occurrence between helminth species. There were few negative relationships between helminth species, regardless of whether presence-absence or abundance data were used. However, some species pairs showed recurrent and significant co-occurrences. There were similar and significant effects of timing of sampling, host gender, and host age, on prevalence and mean abundance of particular species. Co-occurrences were found for those species that showed seasonal declines in prevalence, for those expected to have high colonizing ability based on host age profiles (using abundance data), and for abundant species that may have shared vectors or environmental conditions favorable for transmission. Thus, similarities between parasites in their abundance, transmission biology, and phenology seem sufficient to explain species co-occurrences without invoking other processes such as species interactions. Received: 18 March 1996 / Accepted: 20 April 1999     

Spatial and temporal changes in prevalence of a cloacal cestode in wintering waterfowl along the Gulf Coast of Texas

The cloacal cestode Cloacotaenia megalops is one of the most common helminths of waterfowl. We investigated the effect of this parasite on the body condition of wintering waterfowl populations and compared prevalence among age-sex classes, over time and between habitat types on the upper Gulf Coast of Texas (USA) from October 1986-February 2000. Greater than 9,500 birds of 25 waterfowl species were examined for the parasite. There was no statistical difference (P > 0.05) in body condition between birds with and without the parasite. Average prevalence was lowest for geese (mean = 3.7%) versus 21 to 71% in duck species. Average prevalence was similar (P = 0.81) between diving ducks (mean = 46.9%) and puddle ducks (mean = 43.9%). Prevalence varied among age-sex classes and was related to sex rather than age. Variation among age-sex classes suggests differences in diet between sexes of duck species on the wintering grounds. There was no evidence for declining prevalence over the wintering period. Prevalence differed (P < 0.05) between collection sites, and thereby habitat types, for several species. Temporal trends indicate stable prevalence of C. megalops for diving ducks and increasing prevalence for puddle ducks. The increasing trend for puddle ducks may indicate declining habitat conditions resulting in increased exposure to the intermediate ostracod host.     

Microsatellites identify depredated waterfowl remains from glaucous gull stomachs

Prey remains can provide valuable sources of information regarding causes of predation and the species composition of a predator's diet. Unfortunately, the highly degraded state of many prey samples from gastrointestinal tracts often precludes unambiguous identification. We describe a procedure by which PCR amplification of taxonomically informative microsatellite loci were used to identify species of waterfowl predated by glaucous gulls ( Larus hyperboreus ). We found that one microsatellite locus unambiguously distinguished between species of the subfamily Anserinae (whistling ducks, geese and swans) and those of the subfamily Anatidae (all other ducks). An additional locus distinguished the remains of all geese and swan species known to nest on the Yukon–Kuskokwim delta in western Alaska. The study focused on two waterfowl species which have experienced precipitous declines in population numbers: emperor geese ( Chen canagica ) and spectacled eiders ( Somateria fischeri ). No evidence of predation on spectacled eiders was observed. Twenty-six percent of all glaucous gull stomachs examined contained the remains of juvenile emperor geese.