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PubMed2004

Escalation and trophic specialization drive adaptive radiation of freshwater gastropods in ancient lakes on Sulawesi, Indonesia.

Species flocks in ancient lakes have long been appreciated as ideal model systems for the study of speciation and adaptive processes. We here present data from a new invertebrate model system with intrinsic parameters distinct from those of other documented radiations. The ancient lakes on Sulawesi harbour an endemic species flock of at least 33 species of viviparous snails. Molecular data reveal multiple independent colonizations of the lakes by riverine ancestors. In each colonizing clade, parallel evolution of conspicuous shell morphologies, followed by a differentiation of trophic morphology and the development of habitat specificity can be observed. Extensive shell crushing experiments and strong dentition of the chelae observed in some lacustrine crab species suggest that coevolution with crabs, i.e. escalation, is the most likely cause of initial shell divergence. By contrast, repeated parallel evolution in radula morphology indicates that speciation within lineages is driven by divergent adaptation to different resources among sympatric taxa. The inclusion of coevolutionary processes is unique in this system compared with diversification models developed for vertebrate radiations.

Adaptation, Biological↗
PubMed2005

Retrospective search for evidence of the 1957 Windscale fire in NE Ireland using 129I and other long-lived nuclides.

The accident at Windscale in October 1957 resulted in the release to the atmosphere of a large quantity of radioactivity. The presented work is a retrospective search for evidence of contamination from the accident in the northeastern region of Ireland. A lake yielding a high-resolution sedimentary record was identified near the northeast coast of Ireland. This site was used to reconstruct the history of radionuclide input to the region, based on the analysis of a set of cores extracted from the lake. A chronology for sediment accumulation within the lake was established using radioisotopic dating techniques (including 270Pb). High-resolution gamma and alpha spectrometry techniques were used to quantify concentrations of 137Cs, 239,240Pu and 241Am, all of which were released during the accident. The primary radioactive component of the release was 131I (T1/2 = 8 days), but this short-lived isotope has long since decayed. However, 129I (T1/2 = 1.57 x 10(7) years) was also released during the accident, and in a known ratio to 131I. Recent advances in accelerator mass spectrometry now make it feasible to measure 129I at ultra-trace level and thereby retrospectively reconstruct 131I deposition. Clearly resolved concentration profiles for 137Cs, 239,240Pu and 241Am in the lake cores reflect known historical fallout trends. The data suggest that any contamination from the Windscale fire that might have reached this catchment has been overwritten by input from the testing of nuclear weapons in the atmosphere. A time-series for 129I in lake sediment shows that concentrations in recent sediments are approximately 10 times greater than concentrations recorded in strata corresponding to the period of maximum fallout of other radionuclides from atmospheric testing of nuclear weapons (1964). These recent increases in 129I are attributed to increased emissions from the nuclear industry. The study yields no evidence of any enhancement in radioisotope concentrations, over and above global fallout, in strata dated to 1957, and we conclude that contamination from the Windscale fire had negligible impact on the northeastern region of Ireland.

Accidents↗
PubMed2003

Nuclear markers reveal unexpected genetic variation and a Congolese-Nilotic origin of the Lake Victoria cichlid species flock.

Phylogenetic analyses based on mitochondrial (mt) DNA have indicated that the cichlid species flock of the Lake Victoria region is derived from a single ancestral species found in East African rivers, closely related to the ancestor of the Lake Malawi cichlid species flock. The Lake Victoria flock contains ten times less mtDNA variation than the Lake Malawi radiation, consistent with current estimates of the ages of the lakes. We present results of a phylogenetic investigation using nuclear (amplified fragment length polymorphism) markers and a wider coverage of riverine haplochromines. We demonstrate that the Lake Victoria-Edward flock is derived from the morphologically and ecologically diverse cichlid genus Thoracochromis from the Congo and Nile, rather than from the phenotypically conservative East African Astatotilapia. This implies that the ability to express much of the morphological diversity found in the species flock may by far pre-date the origin of the flock. Our data indicate that the nuclear diversity of the Lake Victoria-Edward species flock is similar to that of the Lake Malawi flock, indicating that the genetic diversity is considerably older than the 15 000 years that have passed since the lake began to refill. Most of this variation is manifested in trans-species polymorphisms, indicating very recent cladogenesis from a genetically very diverse founder stock. Our data do not confirm strict monophyly of either of the species flocks, but raise the possibility that these flocks have arisen from hybrid swarms.

Africa, Eastern↗
PubMed2003

Trematode metacercariae of fishes as sentinels for a changing limnological environment.

Trematode metacercaria populations infecting cichlids in Lake Kinneret (Sea of Galilee) were used as sentinels for the changing limnological environment. Parasitological data from 0+ cichlid fingerlings (Tilapia zillii, Oreochromis aureus, Sarotherodon galilaeus) were collected from the northwest shore of the lake during 1999 to 2001 and compared with data obtained from 1982 to 1984. The results show that the composition of the metacercarial populations changed significantly between the 2 samplings periods. The total number of metacercarial species found in the Kinneret cichlids was lower in 1999 to 2001 than in 1982 to 1984. Metacercariae transmitted by the snail Bulinus truncatus (Clinostomum tilapiae, Euclinostomum heterostomum, Bolbophorus levantinus and Neascus-type metacercariae--black spot and others) that were commonly found in 1982 to 1984 were absent from the fishes sampled during 1999 to 2001. The other trematode metacercariae (Centrocestus sp. and Haplorchis sp. transmitted by Melanoides tuberculata, Pygidiopsis genata transmitted by Melanopsis costata, as well as Phagicola longa, Strigeidae sp.1, an unidentified metacercaria typically found in the liver, and glochidia) increased in abundance in fishes sampled during 1999 to 2001. The calculated 'true' species richness of the habitat, extrapolated as a function of sampling effort, was significantly lower in the 1999 to 2001 versus 1982 to 1984 samples, while significantly fewer fishes needed to be sampled ('sampling effort') during 1999 to 2001 in order to reach the 'true' species richness. The higher calculated values of species richness and diversity for the 1999 to 2001 samples despite the overall decline in species number is explained by the overall increase in metacercariae prevalence.

Animals↗
PubMed2004

Use of 87Sr/86Sr and delta11B to identify slag-affected sediment in southern Lake Michigan.

Slag is a ubiquitous byproduct of the iron-smelting industry and influences geochemistry and water quality in adjacent geologic units, ground and surface water. Despite extensive slag deposition along the Indiana shoreline of Lake Michigan, definitive evidence that slag has affected lakebed sediments has not been established. Concerns for the protection of water and ecosystem resources in the Great Lakes motivated this study to determine if strontium and boron isotopes could be used to identify and delineate slag-affected bed sediment in Lake Michigan. Sixty-five samples of bed sediment were acquired from the southern lobe of Lake Michigan and analyzed for 87Sr/86Sr and deltat11B. Samples immediately offshore from Indiana steel mills and slag-disposal sites contained higher median 87Sr/86Sr values (0.70881) than shoreline sediments collected elsewhere in the basin (0.70847) and uniquely decreased with increasing distance from the shoreline. The highest delta11B values occurred in sediments from the Indiana shoreline (+12.9 to 16.4/1000) but were also elevated in sediments collected offshore from three Lake Michigan cities (+11.7 to 12.7/1000). Contoured isotope data indicated that 82-154 km2 of bed sediment along the Indiana shoreline had elevated 87Sr/86Sr and delta11B values relative to shoreline sediments elsewhere in southern Lake Michigan.

Boron↗
PubMed1983

Hepatocyte changes following selenium accumulation in a freshwater teleost.

This report provides morphological and analytical data for a group of green sunfish collected from an area relatively free of metals and a second group of the same species collected from a lake into which selenium had been discharged. Neutron activation data of livers (and kidneys) collected from these fish show an average of about 11 ppm selenium (fresh weight) for both organs; other metals were not detected in the liver (or kidneys) of these fish. Ultrastructural examination of livers from fish of this group showed focal necrosis, areas of granular cytoplasm, fatty infiltration, increased numbers of Kupffer cells, and disorganized liver architecture--compared with those of controls. The presence of massive levels of selenium in the liver and concomitant hepatocyte changes suggests a causal relationship between these phenomena.

Animals↗
PubMed2001

Results from the Lake Michigan Mass Balance study: concentrations and fluxes of atmospheric polychlorinated biphenyls and trans-nonachlor.

In this paper, we summarize the data and methods used to estimate atmospheric exchange of polychlorinated biphenyls (PCBs) and trans-nonachlor with Lake Michigan. This work was conducted as part of the Lake Michigan Mass Balance (LMMB) study. For the atmospheric component of the LMMB, more than 400 gas- and particulate-phase samples were collected at eight sites on the shore around the lake (shoreline) and at 14 sites on the lake (over-water). We review the quality of the data set; describe the concentrations in atmospheric gas and particulate phases; report local, instantaneous, net gas fluxes; and estimate annual deposition of the particle-associated compounds. The quality of the data set is high except for a subset of over-water samples where PCB contamination is suspected. Gas-phase trans-nonachlor concentrations (although not the resulting gas fluxes) are inversely correlated with latitude and positively correlated with temperature. Gas-phase sigmaPCBs (sum of 98 congener groups) are highest in concentration at the Chicago site and lowest at the Sleeping Bear Dunes site. The resulting sigmaPCB gas fluxes exhibit a seasonality that reflects elevated summertime gas-phase concentrations not compensated by temperature-corrected Henry's law coefficients. Particulate-phase deposition is much smaller in magnitude than gas fluxes, for either compound. Gas and particulate fluxes are comparable only at the Chicago site and only when large (> 10 microm) particulates are considered.

Hydrocarbons, Chlorinated↗
PubMedDate not supplied

[Comparative analysis of the energy flows in the ecosystem of a small eutrophic lake during three vegetation seasons (balance model)].

Seasonal energy flows were calculated, based on a simulation balance model, from unique data collected during three vegatation seasons, 1986-1988, in the ecosystem of the Lake Bolshoy Okunyonok, Leningrad province. The model is based on principles developed by G.G. Winberg's school of production hydrobiology and was described in detail in an earlier work (Kazantseva, 2003). Analysis and comparison of the results showed that certain regularities of energy transformation processes in any lake ecosystem are apparent in spite of natural differences determined by differences in the environment properties and the levels of development of the ecosystem components. For instance, the extreme importance of the bacteriadetritus element in the food chains of water-body was confirmed. Broad spectrum of food and considerable changes in food composition during a vegetation season were clearly shown for most hydrobionts. The degree of consumption was estimated for the production of the organisms at each trophic level. It was shown that all the consumers eat away ca. 50-60 per cent of the production of the forage phytoplankton, 90 per cent of the production of non-predatory benthos, and 20-50 per cent of the production of the other trophic groups during a season. The proposed coefficient of energy transformation, CET(s, k) = Ps(k)/Pk, where Ps(k) in the production of the consumer s created by consuming the source k, and Pk is the production of the source itself, proved to be more stable than the generally accepted coefficient q = Ps/Ps -1.

Ecosystem↗
PubMed2003

[An artificial neural network model for lake color inversion using TM imagery].

The technology of artificial neural network was used for inversing water quality parameters from TM imagery data in the paper in order to study water quality and eutrophic status of lake. On the basis of satellite synchronous monitoring experiment, a BP neural network model was constructed, in which concentrations of SS, CODMn, DO, T-N, T-P and chlo-a were inversed from Landsat TM data and the accuracy of which was good, the relative error of which could be controlled below 25%. Moreover, the reasons of simulating error, ways of improving model and applications of the model were also analyzed in detail. The results of this research told that based on a small-scale of satellite synchronous experiment, the model could be applied successfully in investigation, analysis and estimation of lake water quality.

Color↗
PubMed2003

N:P ratios, light limitation, and cyanobacterial dominance in a subtropical lake impacted by non-point source nutrient pollution.

A long-term (28-year) data set was used to investigate historical changes in concentrations of phosphorus (P), nitrogen (N), N:P ratios, and Secchi disk transparency in a shallow subtropical lake (Lake Okeechobee, Florida, USA). The aim was to evaluate changes in the risk of N2-fixing cyanobacterial blooms, which have infrequently occurred in the lake's pelagic zone. Predictions regarding bloom risk were based on previously published N:P ratio models. Temporal trends in the biomass of cyanobacteria were evaluated using phytoplankton data collected in 1974, 1989-1992, and 1997-2000. Concentrations of pelagic total P increased from near 50 microg l-1 in the mid-1970s to over 100 microg l-1 in the late 1990s. Coincidentally, the total N:P (mass) ratio decreased from 30:1 to below 15:1, and soluble N:P ratio decreased from 15:1 to near 6:1, in the lake water. Published empirical models predict that current conditions favor cyanobacteria. The observations confirm this prediction: cyanobacteria presently account for 50-80% of total phytoplankton biovolume. The historical decrease in TN:TP ratio in the lake can be attributed to a decreased TN:TP ratio in the inflow water and to a decline in the lake's assimilation of P, relative to N. Coincident with these declines in total and soluble N:P ratios, Secchi disk transparency declined from 0.6 m to near 0.3 m, possibly due to increased mineral turbidity in the lake water. Empirical models predict that under the turbid, low irradiance conditions that prevail in this lake, non-heterocystous cyanobacteria should dominate the phytoplankton. Our observations confirmed this prediction: non-N2-fixing taxa (primarily Oscillatoria and Lyngbya spp.) typically dominated the cyanobacteria community during the last decade. The only exception was a year with very low water levels, when heterocystous N2-fixing Anabaena became dominant. In the near-shore regions of this shallow lake, low N:P ratios potentially favor blooms of N2-fixing cyanobacteria, but their occurrence in the pelagic zone is restricted by low irradiance and lack of stable stratification.

Anabaena↗
PubMed2000

Effects of Great Lakes fish consumption on brain PCB pattern, concentration, and progressive-ratio performance.

This study investigated the effects of consumption of Great Lakes fish on progressive ratio performance, and on the pattern and concentrations of brain polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethene (DDE), and mirex in the rat. Adult, male Sprague-Dawley rats were fed a 30% diet of either Lake Ontario salmon (LAKE), Pacific Ocean salmon, or lab chow control for 20 or 65 days. Following the treatment regimen, half the rats from each group were sacrificed immediately for gas chromatographic analysis of organochlorine contaminants, and the other half were tested on a multiple fixed-ratio-progressive-ratio reinforcement schedule and then sacrificed for analysis. Consumption of Lake Ontario fish resulted in significantly higher levels of brain PCBs, DDE, and mirex relative to controls, but still well within human exposure ranges (<1 microg/g fat). Consumption of Lake Ontario fish for 20 or 65 days produced an average brain PCB concentration of 457 and 934 ng/g fat, respectively. Consumption of laboratory rat chow or Pacific Ocean salmon for 20 or 65 days produced an average brain PCB concentration of 240, 464, and 441 ng/g fat, respectively. Moreover, both LAKE-fed groups showed a much more heavily chlorinated pattern of brain PCBs than all control groups, as evidenced by both significant increases in the most heavily chlorinated PCB congeners and significant increases in the average chlorine biphenyl. All LAKE brains contained significant concentrations of DDE and mirex, whereas no control brains contained any detectable quantities. Analysis of progressive-ratio performance indicated that LAKE rats responded normally during fixed-ratio schedules but quit significantly sooner than control rats on a progressive-ratio 5 (PR5) schedule, indicating reduced persistence on progressively leaner reinforcement schedules. Analysis of brain PCBs indicated that total PCBs were most strongly related to PR5 performance. These data indicate that consumption by rats of contaminated Lake Ontario fish produces (1) increased concentrations of PCBs, DDE, and mirex in the brain, (2) a more heavily chlorinated distribution of PCBs in the brain, and (3) reduced persistence of progressive-ratio reinforcement schedules. While these behavioral changes are related to brain PCB level, more work is necessary before the effects can be directly attributed to PCBs.

Adult↗
PubMed2006

The ideal free pike: 50 years of fitness-maximizing dispersal in Windermere.

The ideal free distribution (IFD) theory is one of the most influential theories in evolutionary ecology. It predicts how animals ought to distribute themselves within a heterogeneous habitat in order to maximize lifetime fitness. We test the population level consequence of the IFD theory using 40-year worth data on pike (Esox lucius) living in a natural lake divided into two basins. We do so by employing empirically derived density-dependent survival, dispersal and fecundity functions in the estimation of basin-specific density-dependent fitness surfaces. The intersection of the fitness surfaces for the two basins is used for deriving expected spatial distributions of pike. Comparing the derived expected spatial distributions with 50 years data of the actual spatial distribution demonstrated that pike is ideal free distributed within the lake. In general, there was a net migration from the less productive north basin to the more productive south basin. However, a pike density-manipulation experiment imposing shifting pike density gradients between the two basins managed to switch the net migration direction and hence clearly demonstrated that the Windermere pike choose their habitat in an ideal free manner. Demonstration of ideal free habitat selection on an operational field scale like this has never been undertaken before.

Animals↗
PubMed2003

Response of acid lakes in the UK to reductions in atmospheric deposition of sulfur.

United Kingdom emissions of sulfur dioxide declined by 82% between 1970 and 2000. This decline has been accompanied by reductions in the atmospheric deposition of anthropogenic sulfur. A further expected response, possibly delayed, is a reduction in sulfur concentrations, as sulphate, in upland surface waters. Associated water quality changes, including an increase in alkalinity and reduction in acidity are also anticipated. We examine annual data from 1988 to the present from 10 lakes in the UK acid waters monitoring network for evidence of changes in water chemistry as a response to reductions in the atmospheric deposition of sulfur. We show that there is a close association between reduction in sulfur deposition and reduction in lake water concentrations of sulphate and this provides some supporting evidence for the efficacy of the international agreements to reduce S emissions. However, only 3 of the 10 lakes show an upward trend in alkalinity, and this is not related in a simple fashion to reductions in sulphate concentrations. This suggests that recovery from acidification, measured as an increase in pH and alkalinity, while requiring a reduction in sulphate concentration, may not occur over the same time scale.

Journal Article↗
PubMed1988

Hominid molars from a Middle Stone Age level at the Mumba Rock Shelter, Tanzania.

Three hominid molars were recovered from a depth of 7.0-7.1 meters in the Mumba Shelter at Lake Eyasi, northern Tanzania. Geological context of the finds and archaeological data indicate that people with a Middle Stone Age technology were using the Mumba locality intermittently whenever retreat of lake waters allowed access to the site. Uranium series dates suggest an age on the order of 130,000 years bp for the teeth and stone tools. Based on morphological analyses, the dental remains probably belonged to one individual and appear to be the crowns of two upper permanent M2s and one lower permanent M2. Crown areas are very small, even in comparison to the variation exhibited by recent African populations. Crown patterns have no archaic features. These teeth are smaller than any verifiable archaic Homo sapiens examples; thus, they may represent early anatomically modern Homo sapiens.

Animals↗
PubMed2005

Distribution patterns of mercury in lakes and rivers of northeastern North America.

We assembled 831 data points for total mercury (Hg(t)) and 277 overlapping points for methyl mercury (CH3Hg+) in surface waters from Massachussetts, USA to the Island of Newfoundland, Canada from State, Provincial, and Federal government databases. These geographically indexed values were used to determine: (a) if large-scale spatial distribution patterns existed and (b) whether there were significant relationships between the two main forms of aquatic Hg as well as with total organic carbon (TOC), a well know complexer of metals. We analyzed the catchments where samples were collected using a Geographical Information System (GIS) approach, calculating catchment sizes, mean slope, and mean wetness index. Our results show two main spatial distribution patterns. We detected loci of high Hg(t) values near urbanized regions of Boston MA and Portland ME. However, except for one unexplained exception, the highest Hg(t) and CH3Hg+ concentrations were located in regions far from obvious point sources. These correlated to topographically flat (and thus wet) areas that we relate to wetland abundances. We show that aquatic Hg(t) and CH3Hg+ concentrations are generally well correlated with TOC and with each other. Over the region, CH3Hg+ concentrations are typically approximately 15% of Hg(t). There is an exception in the Boston region where CH3Hg+ is low compared to the high Hg(t) values. This is probably due to the proximity of point sources of inorganic Hg and a lack of wetlands. We also attempted to predict Hg concentrations in water with statistical models using catchment features as variables. We were only able to produce statistically significant predictive models in some parts of regions due to the lack of suitable digital information, and because data ranges in some regions were too narrow for meaningful regression analyses.

Cities↗
PubMed2004

Risk for human health of some POPs due to fish from Lake Iseo.

Risk evaluation for human health was carried out using PCB and PAH concentrations measured in seven fish species from Lake Iseo (Italy) and comparing the experimental data with legal levels and the two new approaches proposed by the US FDA and the US EPA to protect local populations with different food habits. We verified that none of the persistent organic compounds analyzed exceeded the legal limits set by the US FDA, since no specific limit has yet been proposed by the European Union. The two other approaches have pointed out that the acute and chronic effects do not represent any risk for human health, while a possible carcinogenic risk for the local population can arise when 4 and 8 monthly meals are consumed, based on PCB and PAH content in the edible part of fish, respectively.

Animals↗
PubMed2005

Statistical basis for predicting the need for bacterially induced beach closures: Emergence of a paradigm?

Data collected from four beaches along southern Lake Michigan (USA) during the summer of 2004 were subjected to correlation and time-series regression analyses aimed at identifying an optimal suite of variables that could be used to predict log Escherichia coli concentrations in real time. Although other variables entered into the regression equations, waves, outfalls of bacteria from an adjacent stream, sunshine, temperature, and time of day (morning versus afternoon) turned out to be the most useful and consistent predictive variables. A post-hoc analysis showed that regression models are much more successful than previous day's bacterial concentration at predicting whether or not the beach water quality is above or below the threshold criteria for full body contact established by the USEPA. Additional analyses, using 99% confidence intervals on predicted logE. coli concentrations, indicated that in extreme cases of high or low health threat, model predictions are likely to be accurate about 90% of the time. The findings of this study are consistent with previous work in the region and seem to indicate that real-time monitoring of hydrometeorological variables can provide the basis of an early warning system for protecting the public from the health risk posed by harmful pathogens in beach water.

Bathing Beaches↗
PubMed1997

Confirmation of anatoxin-a(s), in the cyanobacterium Anabaena lemmermannii, as the cause of bird kills in Danish lakes.

Cyanobacterial blooms were implicated in bird kills at lakes in Denmark in July 1993 and June-July 1994. These blooms were dominated by Anabaena lemmermannii and were shown to contain a neurotoxin with anticholinesterase activity. In this study, the toxin was isolated by mouse lethality guided column chromatographies from the field sample collected at Lake Knud sø in 1993. Various spectroscopic data indicated that the toxin was anatoxin-a(s), an irreversible anticholinesterase, first reported in Anabaena flos-aquae. Chemical detection of the same toxin in cultured A. lemmermannii also confirmed this species as the cause of the deaths of the wild birds.

Anabaena↗