Swiss Lakes Research Articles

Amino acid nitrogen isotopic composition patterns in lacustrine sedimenting matter

Amino acids (AAs) comprise a large fraction of organic nitrogen (N) in plankton and sedimenting matter. Aquatic studies of organic N compounds in general and of AAs in particular, mostly concentrate on marine environments. In order to study the cycling and fate of organic N and AAs in lakes, we measured the N isotopic composition (δ15N) of bulk organic matter (OM) and of single hydrolysable AAs in sediment trap and sediment samples from two Swiss lakes with contrasting trophic state: Lake Brienz, an oligotrophic lake with an oxic water column, and Lake Zug a eutrophic, meromictic lake. We also measured the N isotopic composition of water column nitrate, the likely inorganic N source during biosynthesis in both lakes. The δ15N–AA patterns found for the sediment trap material were consistent with published δ15N–AA data for marine plankton. The AA composition and primary δ15N–AA signatures are preserved until burial in the sediments. During early sedimentary diagenesis, the δ15N values of single AAs appear to increase, exceeding those of the bulk OM. This increase in δ15N–AA is paralleled by a decreased contribution of AAs to the total OM pool with progressed degradation, suggesting preferential AA degradation associated with a significant N isotope fractionation. Indicators for trophic level based on δ15N–AAs were determined, for the first time in lacustrine systems. In our samples, the trophic AAs were generally enriched in 15N compared to source AAs and higher trophic δ15N–AA values in Lake Zug were consistent with a higher trophic level of the bulk biomass compared to Lake Brienz. Especially the difference between average trophic δ15N–AAs and average source δ15N–AAs was sensitive to the trophic states of the two lakes. A proxy for total heterotrophic AA re-synthesis (ΣV), which is strongly associated with heterotrophic microbial reworking of the OM, was calculated based on δ15N values of trophic AAs. Higher ΣV in Lake Brienz indicate enhanced heterotrophic bacterial reworking of AAs under oligotrophic conditions. Despite changes in the δ15N–AA values within the sediments, the proxies based on these values were consistent over the studied sediment profile, indicating the preservation of trophic signatures; therefore, our results underscore that δ15N–AA analysis of sedimentary records represents a promising tool to assess trophic levels and bacterial re-synthesis in lakes.

Maleimides in recent sediments – Using chlorophyll degradation products for palaeoenvironmental reconstructions

Maleimides (transformation products of chlorophylls and bacteriochlorophylls) were studied in recent sediments from the Swiss lake Rotsee and the Romanian Black Sea Shelf to investigate chlorophyll degradation, the role of oxygen in maleimide formation, and to identify their sources. Naturally occurring maleimides (i.e. “free” maleimides) and maleimides obtained after chromic acid oxidation of sediment extracts (i.e. “bound” maleimides) were analysed. 2-Methyl-maleimide (Me,H maleimide), 2,3-dimethyl-maleimide (Me,Me maleimide), 2-methyl-3-vinyl-maleimide (Me,vinyl maleimide), 2-methyl-3-ethyl-maleimide (Me,Et maleimide) and traces of 2-methyl-3-iso-butyl-maleimide (Me,i-Bu maleimide) occurred naturally in the sediment with a large predominance of the Me,Et homologue. Tetrapyrrolic pigments related to chlorophylls were the main source of maleimides, although variable contributions of other sources such as cytochromes and/or phycobilins cannot be completely ruled out. The predominant Me,Et maleimide and Me,vinyl maleimide most likely originate mainly from chlorophyll a related pigments. The same holds for Me,H maleimide, which might be formed following degradation of ring E from the tetrapyrrolic nucleus. Alternatively, Me,H maleimide and Me,Me maleimides might be formed by a recently discovered transformation pathway involving the oxidation of vinylic chlorophyll substituents and the formation of an aldehyde intermediate. 2-Methyl-3-n-propyl-maleimide (Me,n-Pr maleimide) and Me,i-Bu maleimide arising from bacteriochlorophyll related pigments traced the presence of phototrophic sulfur bacteria (Chlorobi), indicating photic zone euxinic and anoxic conditions in Rotsee during the last 150years and throughout the Black Sea history, including the limnic phase of the Black Sea (Unit 3). Some other minor maleimides with specific alkylation pattern also originate from bacteriochlorophylls, while the source of others could not be identified. Free maleimides were mainly formed in the sediment in the absence of oxygen. Novel maleimide degradation indices are proposed to estimate the degree of OM degradation (OM freshness/degradability). These proxies are applicable on longer timescales than e.g. the chlorin index.

The use of long‐term monitoring data for studies of planktonic diversity: a cautionary tale from two Swiss lakes

Summary Long‐term data have been suggested as resources for investigating environmental influences on biodiversity and, in turn, the role of biodiversity for ecosystem dynamics. However, scientists analysing biodiversity patterns in long‐term data need to recognise that multidecadal time series are likely to suffer from inconsistencies in methodology, which might strongly complicate the interpretation of diversity patterns. Unfortunately, such inconsistencies are usually difficult to detect, and consequently, it is not known how strongly they affect the conclusions drawn. Here, we highlight two long‐term data sets sampled by one laboratory to analyse patterns in phytoplankton richness in two Swiss lakes, Lake Zurich and Lake Walen. Apparent patterns in the long‐term species richness in the two lakes arise from: (i) inconsistencies in species identification (changes in taxonomic literature and/or taxonomic expertise of the counting personnel) and (ii) changes in the detection limits of taxa. Hence, bias in these two case studies was strong enough to obscure any possible effects on species richness of environmental change (oligotrophication). We show that in the case of these two data sets, inconsistency confounds estimates of phytoplankton richness not only at the species level but even at the generic and familial levels. This suggests that a solution often proposed for inconsistency, that is, reanalysis of the data after aggregation to genus or family, may be insufficient. We suggest the use of two diagnostic plots, which may be used in other studies examining richness patterns in either long‐term time series or comparative studies in which several scientists/laboratories contributed to data acquisition. These plots illustrate temporal or spatial patterns in (i) the percentage of taxa identified only to genus and (ii) in the 5% percentile of the concentrations of individual algal taxa. They will help to identify inconsistency problems due to changes or differences in (i) taxonomic expertise and (ii) detection limits.

Adaptive plasticity and genetic divergence in feeding efficiency during parallel adaptive radiation of whitefish (Coregonusspp.)

Parallel phenotypic divergence in replicated adaptive radiations could either result from parallel genetic divergence in response to similar divergent selection regimes or from equivalent phenotypically plastic response to the repeated occurrence of contrasting environments. In post-glacial fish, replicated divergence in phenotypes along the benthic-limnetic habitat axis is commonly observed. Here, we use two benthic-limnetic species pairs of whitefish from two Swiss lakes, raised in a common garden design, with reciprocal food treatments in one species pair, to experimentally measure whether feeding efficiency on benthic prey has a genetic basis or whether it underlies phenotypic plasticity (or both). To do so, we offered experimental fish mosquito larvae, partially burried in sand, and measured multiple feeding efficiency variables. Our results reveal both, genetic divergence as well as phenotypically plastic divergence in feeding efficiency, with the phenotypically benthic species raised on benthic food being the most efficient forager on benthic prey. This indicates that both, divergent natural selection on genetically heritable traits and adaptive phenotypic plasticity, are likely important mechanisms driving phenotypic divergence in adaptive radiation.

The use of calibration-in-time to reconstruct temperature from biological proxies preserved in lake sediments: examples using chironomids preserved in two Swiss lakes

The use of calibration-in-time to reconstruct temperature from biological proxies preserved in lake sediments: examples using chironomids preserved in two Swiss lakes

Late Holocene Climate, Land-use and Floodplain Sedimentation In the Culm Catchment, UK

In this paper the most important problems in dating lake sediments with unsupported 210Pb are summarized and the progress in gamma-spectrometry of the unsupported 210Pb is discussed. The main topics of these studies concern sediment samples preparation for gamma-spectrometry, measurement techniques and data analysis, as well as understanding of accumulation and sedimentation processes in lakes. The vertical distributions of artificial (137Cs, 241Am, 239Pu) and natural radionuclides (40K, 210,214Pb, 214Bi) as well as stable trace elements (Fe, Mn, Pb) in sediment cores from four Swiss lakes were used as examples for the interpretation, inter-comparison and validation of depth–age relations established by three 210Pb-based models (CF-CSR, CRS and SIT). The identification of turbidite layers and the influence of the turbidity flows on the accuracy of sediment dating is demonstrated. Time-dependent mass sedimentation rates in lakes Brienz, Thun, Biel and Lucerne are discussed and compared with published data.

Natural and anthropogenic trace elements records from low and high altitudes Swiss lakes

Natural and anthropogenic trace elements records from low and high altitudes Swiss lakes

Effects of changes in the driving forces on water quality and plankton dynamics in three Swiss lakes – long‐term simulations with BELAMO

Summary1. With a modified version of the lake model BELAMO, we were able to describe the essential features of the dynamics of nutrients, dissolved oxygen, phyto‐ and zooplankton in three lakes of different trophic status over periods of 19–30 years, with essentially the same model parameters for all three lakes. This is remarkable, as the measured nutrient inputs decreased considerably during the simulated time period.2. Despite having done this before for a period of 4 years with an earlier version of the model, a considerable effort was required that led to a series of model modifications without which the data could not be matched. This demonstrates that long‐term calibration of a model that combines processes in the water column with mineralisation in the sediment can be difficult.3. Due to the necessarily simplified processes within the model, there is a bias in its output. We applied a recently developed technique for model calibration and uncertainty analysis to address bias and multiple calibration criteria. To account for the demanding long‐term simulations, a simplified numerical implementation of this technique was used.4. Our results demonstrate good understanding of the chemical state of the lake during the calibration period but less of the biological variables. The credibility intervals used to visualise this knowledge widen substantially during the prediction period (consisting of the last 10 years of the simulation).5. The joint calibration of the model with long‐term data from lakes of different trophic status is possible but only with considerable prediction uncertainty. Due to the explicit consideration of bias in our calibration technique, we are able to estimate quantitatively the uncertainty of our knowledge about chemical and biological variables in the lake.

Speciation leads to divergent methylmercury accumulation in sympatric whitefish

Central European lake whitefish (Coregonus spp.) colonized Swiss lakes following the last glacial retreat and have undergone rapid speciation and adaptive radiation. Up to six species have been shown to coexist in some lakes, and individual species occupy specific ecological niches and have distinct feeding and reproductive ecologies. We studied methylmercury (MeHg) accumulation in sympatric whitefish species from seven Swiss lakes to determine if ecological divergence has led to different rates of MeHg bioaccumulation. In four of seven lakes, sympatric species had distinctly different MeHg levels, which varied by up to a factor of two between species. Generally, species with greater MeHg levels were smaller in body size and planktivorous, and species with lower MeHg were larger and benthivorous. While modest disparities in trophic position between species might be expected a priori to explain the divergence in MeHg, δ15N of bulk tissue did not correlate with fish MeHg in five of seven lakes. Results of a nested ANCOVA analysis across all lakes indicated that only two factors (species, lake) explained substantial portions of the variance, with species accounting for more variance (52 %) than inter-lake differences (32 %). We suggest that differences in MeHg accumulation were likely caused by diverging metabolic traits between species, such as differences in energy partitioning between anabolism and catabolism, potentially interacting with species-specific prey resource utilization. These results indicate substantial variability in MeHg accumulation between closely related fish species, illustrating that ecological speciation in fish can lead to divergent MeHg accumulation patterns.

Modes and mechanisms of aDaphniainvasion

Whether exotic species invade new habitats successfully depends on (i) a change in the invaded habitat that makes it suitable for the invader and (ii) a genetic change in the invading taxon that enhances its fitness in the new habitat, or both. We dissect the causes of invasions of Swiss lakes, north of the Alps, by Daphnia galeata (a zooplankter typical of eutrophic lakes, e.g. those south of the Alps, which are also warmer) by comparing the fitness performance of eight geographically distributed clones that were fed algal-food typical of oligotrophic versus eutrophic conditions at two temperatures. Daphnia longispina, native to oligotrophic Swiss lakes, served as a reference. Daphnia galeata requires eutrophic food to persist, whereas D. longispina survives and grows on oligotrophic food but does even better on eutrophic food. Invasion by D. galeata is further explained because invading clones from the north perform better on eutrophic food and at cooler temperatures than native clones from the south, suggesting a local response to countergradient selection. Our data support the hypothesis that populations of the invader in northern lakes are dominated by well-adapted genotypes. Our results illustrate how environmental change (i.e. eutrophication) and local adaptation can act together to drive a successful invasion.

Interfacing a one‐dimensional lake model with a single‐column atmospheric model: Application to the deep Lake Geneva, Switzerland

A single column atmospheric model (SCM) coupled to a one‐dimensional lake model devised for climate simulations is described in this paper. As a test case, this coupled model is applied to the deepest section of Lake Geneva in Switzerland. Both atmospheric and lake models require a minimal set of adjustable parameters to reproduce the local observations of temperature, moisture, and wind as well as those of the lake thermal profiles. A number of simulations have been performed to produce a sorted set of optimal model parameters that reproduces the mean and the variability of the seasonal evolution of the thermal profiles in the lake as well as those of the mean and the variability of the surface air temperature, moisture, and winds. The lake water temperature is reproduced realistically using the optimal calibration parameter values with a seasonal‐ and depth‐averaged error of 0.41°C in summer, −0.15°C in autumn, 0.01°C in winter, and 0.27°C in spring when compared to the lake observations. Also, the errors of the seasonally averaged simulated anemometer‐level wind speed, screen‐level air temperature, and specific humidity to the station‐derived values are 0.04 m s−1, 1.04°C, and 0.74 g kg−1, respectively. Results of this study contribute to the understanding of the air‐lake interactions present over the deep Lake Geneva. In addition, the sensitivity experiments carried out in this paper serve as the basis for experiments aiming at studying the thermal response of the deep Swiss Lake Geneva under future global climate change conditions reported in a companion paper.

Preface: Ostracoda: biostratigraphy and applied ecology

The series of International Symposia on Ostracoda started in 1963, when ISO1 was organised in the historic Zoological Station of Naples by Dr Harbans Singh Puri. Matzke-Karasz et al. (2007) analysed the content of the 15 first ISO proceedings and grouped the 906 papers published in the various proceeding volumes (in stand-alone books and in journals) into several categories. Biostratigraphy and (palaeo-) ecology have always constituted strong components in this series of proceedings, and this inspired the organisers of the ISO16 to determine biostratigraphy and applied ecology as the main themes of their symposium. The 16th International Symposium on Ostracoda was held in Brasilia, Brazil, between 26 and 30 July 2009. The scientific communities from 25 different countries had representatives among the 107 participants, who brought to the meeting an amount of 102 contributions: 46 oral communications, 52 poster presentations and four keynote lectures given by invited speakers. The present proceedings volume comprises ten papers, a small selection of these contributions, and will serve as a legacy to the memory of this highly successful event. As always, the communication of scientific results is of prime importance, but the personal contacts with distant colleagues often leads to fertilisation of ideas and to successful collaborations. The ISO16 meeting scored on both accounts! Furthermore, by holding an ISO for the first time in South America, we hope to have helped foster ostracodology on this continent. In spite of the emphasis given in the current version of the symposium to biostratigraphy and applied ecology, contributions comprised also other research lines, such as Taxonomy, Morphology, Biogeography, Systematics and Evolution. In terms of geological time, the present proceedings contain six papers on Recent faunas, one on Tertiary, two on Mesozoic and one on Palaeozoic Ostracoda. The papers in this volume are loosely organised to follow this chronological sequence. The volume opens with the paper by Decrouy et al. (this volume), who studied the Sediment Penetration Depth of epiand infaunal ostracods in the Swiss Lake Geneva. The relevance of this paper is clear: ostracods have to moult 8–9 times during their development and each time have to calcify their valves using chemical Guest Editors: D. A. Do Carmo, R. L. Pinto & K. Martens / Ostracoda – Biostratigraphy and Applied Ecology

Separate introductions but lack of genetic variability in the invasive clam Corbicula spp. in Swiss lakes

This study documents the spread of the invasive clam Corbicula spp. in Switzerland since its first record in the River Rhine in 1995. Clams were newly recorded in several Swiss lowland lakes whose interconnecting rivers have not yet been colonized. We present evidence for separate introductions of an identical haplotype of Corbicula fluminea into five lakes in Switzerland in the years 2003–2010 based on the mitochondrial DNA-sequence of the COI in specimens sampled. This suggests passive dispersal of the clam by human activities and/or waterfowl. All but one of the 72 genetically analysed individuals were assigned to a single haplotype FW5 and to the species name C. fluminea. Recent records of specimens, which were not genetically analysed, displayed all the shell morphology of C. fluminea, confirming the dominance of this clam in Swiss rivers and lakes.

Does water depth or diet divergence predict progress towards ecological speciation in whitefish radiations

Question: Is the extent of genetic divergence between sympatric whitefish ecotypes – a proxy for progress towards speciation – related to the extent of ecological divergence in spawning depth or diet? Study system: Whitefish (Coregonus spp.) that have diversified into two or more sympatric ecotypes in subalpine Swiss lakes. Sympatric ecotypes vary in the extent of reproductive isolation. Analytical methods: We measured the degree of spawning depth differentiation based on the depth-at-capture of different ecotypes. We estimated diet differentiation between ecotypes as Mahalanobis distances from stable isotopes. We compared each of these to genetic differentiation measured from AFLP data, using modified correlation tests and phylogenetically independent contrasts to account for non-independence of comparisons in lakes with more than two ecotypes. Results: We found that the magnitude of divergence in spawning depth was generally – albeit only marginally significantly – associated with the extent of genetic divergence between sympatric ecotypes. This effect was clearly stronger than the effect of diet divergence, which was not associated with genetic differentiation. Furthermore, there was no evidence for an interactive effect of depth and diet divergence on progress towards speciation.

Subaqueous morphology of Lake Lucerne (Central Switzerland): implications for mass movements and glacial history

Bathymetric data available for Swiss lakes have typically only low to moderate resolution and variable quality, making them insufficient for detailed underwater geomorphological studies. This article presents results of a new bathymetric survey in perialpine Lake Lucerne using modern hydrographic equipment. A digital terrain model (DTM) of the lake floor (raster dataset with 1 m cell size) covering the Chrüztrichter and Vitznau basins documents signatures of major Holocene mass movements and relics from the glacial history of the lake. Combining the bathymetry data with reflection seismic profiles and an existing event chronology allows investigating the morphology in its geological context. Subaqueous sediment slide scars with sharp headwalls cover large areas on moderately inclined slopes. The particularly large Weggis slide complex, correlated with an historical earthquake (ad 1601), features a ~9 km long and 4–7 m high headwall and covers an area of several square kilometers. Large debris cones of prehistoric rockfalls and the deposits of recent rockfall events imaged on the almost flat basin plain document mass-movement activity on steep slopes above the lake. Six transverse moraines, visible as subaqueous ridges, as lake-floor lineaments, or only imaged on reflection seismic profiles, indicate a complex glacial-inherited morphology. As many of the documented features result from potentially catastrophic events, high-resolution bathymetry can significantly improve natural hazard assessment for lakeshore communities by extending classical hazard maps to the subaqueous domain.

Anthropogenic eutrophication shapes the past and present taxonomic composition of hybridizing Daphnia in unproductive lakes

It has been proposed that anthropogenic eutrophication of lakes facilitated the establishment of populations of the cladoceran Daphnia galeata into the originally oligotrophic lakes north of the European Alps in the 1960s. This hypothesis lacks the support of studies on unproductive lakes, in which the past eutrophication is assumed to have never been on the level necessary for D. galeata to reach high abundances and to establish permanently. In order to investigate if such species shifts also happened in unproductive systems, we studied the past and present taxonomic composition of three ultra‐oligotrophic Swiss lakes that were only marginally affected by eutrophication using molecular methods on diapausing eggs sampled from sediment cores. D. galeata temporarily established in unproductive lakes, but its colonization success seemed to depend on the general trophic state of the lake and the magnitude of eutrophication. In two of the studied lakes, D. galeata could establish a significant population size, whereas it was not successful in the most unproductive lake with the weakest eutrophication. Even in unproductive lakes, eutrophication led to partly irreversible species changes, providing evidence that this anthropogenic disturbance is responsible for species shifts in many pre‐alpine lakes in Central Europe.

Distribution of branched and isoprenoid tetraether lipids in an oligotrophic and a eutrophic Swiss lake: Insights into sources and GDGT-based proxies

Distributions of isoprenoid (isoGDGT) and branched glycerol dialkyl glycerol tetraethers (brGDGTs) were measured in the water column and sediments of the eutrophic Lake Lugano and the oligotrophic Lake Brienz, Switzerland. Absolute concentrations of isoprenoid, i.e. archaeal GDGTs, were highest in the euphotic zone of both lakes, as well as in sediments deposited at times when lake eutrophication occurred. This indicates that GDGT concentrations may be used as indicators for primary productivity. Both lakes, including the anoxic bottom water of Lake Lugano, are characterised by GDGT distributions typical for group I Crenarchaeota with GDGT-0/crenarchaeol ratios of around 1. Comparison of the distribution of brGDGTs with isoGDGTs and other terrestrial biomarkers throughout the Lake Lugano water column, together with CBT/MBT-derived temperatures that resemble that of the lake, suggest significant in situ production. BIT index values for Lake Brienz sediments (ca. 0.4) were significantly higher than water column values (ca. 0.1), most probably because terrestrial run off events were not captured during water sampling. TEX 86 – derived temperatures reflect surface water conditions to within a few degrees, while lower values obtained from deeper water layers suggest a contribution of in situ produced isoGDGTs. For both lake sediments, TEX 86-derived temperatures could be matched reasonably with mean annual lake surface water temperature variation, albeit with a larger offset for Lake Lugano. This suggests that absolute temperatures can only be reconstructed from lake sediments for which a local calibration is known.

Patterns of morphological changes and hybridization between sympatric whitefish morphs (Coregonus spp.) in a Swiss lake: a role for eutrophication?

Whitefish, genus Coregonus, show exceptional levels of phenotypic diversity with sympatric morphs occurring in numerous postglacial lakes in the northern hemisphere. Here, we studied the effects of human-induced eutrophication on sympatric whitefish morphs in the Swiss lake, Lake Thun. In particular, we addressed the questions whether eutrophication (i) induced hybridization between two ecologically divergent summer-spawning morphs through a loss of environmental heterogeneity, and (ii) induced rapid adaptive morphological changes through changes in the food web structure. Genetic analysis based on 11 microsatellite loci of 282 spawners revealed that the pelagic and the benthic morph represent highly distinct gene pools occurring at different relative proportions on all seven known spawning sites. Gill raker counts, a highly heritable trait, showed nearly discrete distributions for the two morphs. Multilocus genotypes characteristic of the pelagic morph had more gill rakers than genotypes characteristic of benthic morph. Using Bayesian methods, we found indications of recent but limited introgressive hybridization. Comparisons with historical gill raker data yielded median evolutionary rates of 0.24 haldanes and median selection intensities of 0.27 for this trait in both morphs for 1948-2004 suggesting rapid evolution through directional selection at this trait. However, phenotypic plasticity as an alternative explanation for this phenotypic change cannot be discarded. We hypothesize that both the temporal shifts in mean gill raker counts and the recent hybridization reflect responses to changes in the trophic state of the lake induced by pollution in the 1960s, which created novel selection pressures with respect to feeding niches and spawning site preferences.

PERSISTENT ORGANIC POLLUTANTS: Melting Glaciers Release Frozen Toxicants

The melting of glacial ice that formed in the middle of the twentieth century may be a source of a cocktail of persistent, bioaccumulative toxic substances that can threaten human health and the environment, according to a study by Christian Bogdal, a postdoctoral research fellow at the Swiss Federal Institute of Technology, Zurich, and colleagues in the 1 November 2009 issue of Environmental Science & Technology. Their findings, along with those of a handful of other studies, suggest the release of toxics once bound within glaciers may be a little-recognized consequence of ongoing climate change. The Swiss team analyzed sediment samples taken from Lake Oberaar, a glacier-fed lake in central Switzerland. They measured sediment levels of several pollutants that would have entered the lake over the period 1953–2006 and compared the measurements with those from three lower-altitude Swiss lakes that aren’t glacier fed. The substances analyzed included 17 dioxins and furans, 18 polychlorinated biphenyls (PCBs), 10 synthetic musk compounds, DDT and two of its transformation products (DDE and DDD), 4 additional organochlorine pesticides (hexachlorobenzene, hexachlorocyclohexane, dieldrin, and heptachlor epoxide) and their transformation products, and polychlorinated naphthalenes. The Lake Oberaar and lower-altitude samples reflected a generally consistent pattern of increased influx of the compounds into the lakes from the 1950s through a peak in the 1960s–1970s, followed by a decrease to relatively low levels in the 1980s and 1990s. The exception was musk compounds, whose sediment influx was fairly steady from the 1950s to the mid-1990s. These patterns parallel the widespread increase in production and use of these substances from the 1950s through the 1970s, and the subsequent decline (except in the case of musk compounds) as concerns about toxic effects often resulted in restrictions or bans on use. These patterns also mesh with the premise that the primary source of the sediment toxics to that point was deposition of airborne pollutants generated in urban, industrial, and agricultural areas. Beginning in the late 1990s, however, the influx of all the compounds into Lake Oberaar—but not the lower-altitude lakes—increased moderately to sharply. In some cases, the new peak influxes were 2–5 times higher than the 1960s–1970s peaks. These increases coincide with a total reduction in Alpine glacier volume of about 12% between 1999 and 2008, according to a report by Daniel Farinotti and colleagues in the August 2009 issue of Global and Planetary Change. About one-quarter of that reduction occurred following the unusually hot summer of 2003. Bogdal and colleagues hypothesize that the sources of the later contaminant influxes they observed likely were not distant, because production and use of these chemicals had decreased substantially. Instead, they conclude the glacial meltwater was the source. Studies they are conducting at Lake Oberaar and elsewhere support this hypothesis, says Bogdal. The evidence to date suggests the release of these and other persistent toxics, such as lead and mercury, may be a concern for many glaciated settings. Among areas of potential concern, say Bogdal and other experts in this field, are locations in the Arctic region, Antarctica, the Alps, the Himalayas, and the Caucasus, Andes, Rocky, Cascade, and Sierra Nevada mountain ranges. “Melting of glaciers is releasing a huge amount of water containing dangerous contaminants used in the past,” says Roberta Bettinetti, an assistant professor of freshwater ecology at Italy’s University of Insubria. “Now these pollutants can contaminate great basins even at low altitudes where water is used for drinking and fishing purposes.” In the October 2008 issue of Chemosphere, Bettinetti and colleagues reported on their study of the toxic effects of melting glaciers on biota of two southern Alpine lakes. They found that the amount of DDT and its metabolites released by melting glacial ice increased the concentrations in lake mussels and fish above the threshold considered safe for human consumption. Silvana Galassi, a professor of ecology at the University of Milan and coauthor of that report, recommends implementation of monitoring to identify areas where mitigation, such as limiting fish consumption or avoiding disturbance of sediments, may be warranted.

Inter- and intra-specific characterization of tapeworms of the genus Diphyllobothrium (Cestoda: Diphyllobothriidea) from Switzerland, using nuclear and mitochondrial DNA targets

Human diphyllobothriosis is caused by at least 14 species of cestodes belonging to the genus Diphyllobothrium. Molecular analysis by sequencing of nuclear and mitochondrial targets identifies some species at inter- and intra-specific level, and helps to reconstruct their phylogenetic relationships. Nevertheless, the suitability of further molecular targets deserves to be widened, and the comparison of samples of different geographical origin could allow their intra-specific characterization, which could also be useful for epidemiological purposes. In this study, we investigated inter- and intra-specific variability among tapeworms of the genus Diphyllobothrium, with focus on Diphyllobothrium latum, originated from Switzerland. Samples were analyzed by comparing the sequences of two nuclear and two mitochondrial DNA targets. We analyzed 27 samples belonging to 4 species ( D. latum, Diphyllobothrium nihonkaiense, Diphyllobothrium dendriticum and Diphyllobothrium ditremum), 15 of which isolated from clinical cases (adults and eggs), 2 from wild canines, and 2 from fish of Swiss lakes (plerocercoid larvae); 8 samples of homologous species from other geographic origins were also sequenced and compared with the Swiss ones. Sequences of partial small subunit ribosomal RNA (18S rRNA) gene and partial internal transcribed spacers 1 and 2 (ITS1-2) were not useful even in inter-specific identification, whereas sequences of complete cytochrome c oxidase subunit 1 ( cox1) and cytochrome b ( cob) genes allowed us to assess inter- and intra-specific variations among the samples. Cox1 and cob could differentiate 3 and 5 haplotypes within the species D. latum. The results are discussed in the light of the anamneses provided by part of the patients.