Inorganic tripton in the Finger Lakes of New York: importance to optical characteristics

Inorganic particles in the upper waters of the 11 Finger Lakes of New York are morphometrically and elementally characterized by individual particle analysis conducted with scanning electron microscopy interfaced with automated image and X-ray analyses (IPA/SAX). Coupled measurements of Secchi disk transparency (SD), the attenuation coefficient for downwelling irradiance (K_d), the beam attenuation coefficient at 660 nm, and turbidity (T_n) were made to support evaluation of the importance of non-living, inorganic particles (inorganic tripton) in regulating these optical features of water quality. Wide differences in levels of inorganic tripton, represented in terms of particle projected area per unit volume (PAV_in), and the optical measures are reported for these lakes. However, generally similar size distributions are observed for the inorganic tripton for the lakes. Terrigenous suspensoids, in the form of clay minerals, dominated the inorganic tripton particle assemblage of nine lakes, while CaCO₃, formed autochthonously, dominated in the other two and was a noteworthy contributor in four others. PAV_in is demonstrated to be an important regulator of the optical properties of these lakes, performing substantially better than chlorophyll in predicting SD, and T_n, and interlake differences in these optical measures.Contribution No. 226 of the Upstate Freshwater Institute     

Patterns and impacts of inorganic tripton in Cayuga Lake

Inorganic tripton in the upper waters of Cayuga Lake, NY, is characterized, quantified and contrasted for shallow (<6 m) and deep (>100 m) water regions based on analyses with scanning electron microscopy equipped with automated image analysis and X-ray energy spectroscopy (SAX) of samples collected in 1999 and 2000. The impacts of this material on water clarity and the phosphorus (P) pool are evaluated based on paired measurements of turbidity (T_n), Secchi disc transparency (SD), chlorophyll, and four fractions of particulate P (PP) determined according to selective extraction protocols. The major components of inorganic tripton in the lake are reported to be clay minerals and quartz, received from the watershed, and calcium carbonate (CaCO₃), that is produced internally. Clay minerals are the dominant component in a shallow region that receives tributary inflows. CaCO₃, precipitated during a mid-summer whiting event, is reported to be the dominant component of inorganic tripton for the deep water region for a low runoff year, while clays can become dominant in these areas after prolonged intervals of high runoff. It is demonstrated that inorganic tripton, rather than phytoplankton, is the primary regulator of T_n and SD, it represents most of the PP, and is primarily responsible for the higher T_n, lower SD, and higher TP in the shallow area compared to the deep water region. Efforts to improve clarity in this shallow region of the lake should consider the feasibility of controlling the input of terrigenous suspensoids rather than reductions in P loading.     

Prediction of the light attenuation coefficient through the Secchi disk depth: empirical modeling in two large Neotropical ecosystems

The easiest way to evaluate water transparency is from the Secchi disk depth (SD). The behavior of radiation passing through water can also be quantified by the light attenuation coefficient (k) of photosynthetically active radiation (PAR), measured using quanta meters. Due to the high costs of quanta meters, k is usually predicted from SD. This prediction can be made using the index SD × k or using nonlinear models that correlate these variables. The aims of this study were to generate models predicting k through SD in two large Neotropical ecosystems (a reservoir and a floodplain) and to test whether 1.7, the index used worldwide, is adequate for predicting k in these ecosystems. The current paper also tested the effects of time (between seasons and among years) and space (between ecosystems and inside each ecosystem) upon such predictions. A standard 30-cm Secchi disk was used to measure SD. Simultaneously, PAR was measured at two depths to estimate k. A total data set of 2,136 measurements taken from 2001 to 2005 was used. The index generated, 2.26, was significantly different from 1.7 (t test, p < 0.01). This suggests that 1.7 is not adequate for Neotropical ecosystems. In general, both the index and the models generated differed across ecosystems and over time. In addition, the analysis showed that a nonlinear model (k = 2.00 × SD^−0.76, N = 2,136) was more reliable for predictions.     

Factors influencing inorganic turbidity in a great plains reservoir

Nephelometric turbidity and Secchi disc were measured at 16 sampling stations at Lake Carl Blackwell, Oklahoma on 54 dates from 12 February 1982 to 24 January 1983. Measurements of precipitation, wind velocity, effective fetch, water depth, and sediment particle size were also recorded. Turbidity values ranged from 16 to 1 140 NTU and Secchi disc transparency from 2 to 110 cm. Turbidity was generally highest at shallow water sampling stations in the western end and upper arms of Lake Carl Blackwell and decreased with increasing depth. Increases in turbidity during the spring of 1982 were attributed to sediment resuspension and drastic turbidity increases were observed following heavy May rains. Two multiple regression models were developed to predict nephelometric turbidity levels for a given set of climatological and morphometric parameters. One model was based on data for the entire sampling period and is useful in predicting turbidity under high inflow conditions. A second model was derived from data collected prior to periods of heavy rains and is useful in predicting turbidity under more common conditions of moderate winds and rain.     

Effects of suspensoids (turbidity) on penetration of solar radiation in aquatic ecosystems

In mainland Australia and in southern Africa, the aridity of the climate and sparse vegetative cover increase the susceptibility of the soils to erosion, and as a consequence surface waters are usually turbid. The inanimate suspensoids in such waters, the tripton fraction of the limnologist, are responsible for virtually all the light scattering, and also, by virtue of the yellow-brown humic materials adsorbed on their surface, for a substantial part of the light absorption. Spectral absorption data for suspensoids in terms of theirin situ absorption coefficient values, and the contribution of suspensoids to absorption of photosynthetically available radiation (PAR) are given for certain Australian water bodies.To understand the effect of suspensoids on attenuation of the solar flux with depth, the scattering coefficient must also be known, and this can be determined from the nephelometric turbidity or from up- and down-welling irradiance measurements. The effect of particle size on scattering efficiency is discussed.An equation expressing the vertical attenuation coefficient for downward irradiance as a function of absorption coefficient, scattering coefficient and solar altitude is presented, and is used to explore the effects of absorption due to dissolved colour and suspensoids, and the effects of scattering by suspensoids, on the penetration of PAR.Suspensoids, by increasing the rate of attenuation of the solar flux with depth, can greatly diminish the euphotic depth of a water body, with a consequent decrease in the ratio of the euphotic to the mixed depth: thus turbidity can reduce productivity of a water body substantially below that which might be expected on the basis of nutrient availability. Shallow turbid waters of low intrinsic colour can, however, be highly productive. By diminishing the depth of the layer within which solar energy is dissipated as heat, suspensoids can greatly modify the hydrodynamic behaviour of water bodies, and this also has far-reaching ecological consequences.Suspensoids drastically impair the visual clarity of water, a fact of major significance for the aquatic fauna, as well of aesthetic significance for humanity. The reciprocal of the Secchi depth is more correctly thought of as a guide to the vertical contrast attenuation coefficient rather than to the vertical attenuation coefficient for irradiance. The reflectivity of a water body, being at any wavelength proportional to the backscattering coefficient divided by the absorption coefficient, is highly dependent on the concentration, and optical character, of the suspensoids present. This has implications not only for the appearance (colour, muddiness) of the water to an observer, but also for the remote sensing of water composition by air- or satellite-borne radiometric sensors.     

Seasonality and trends in the Secchi disk transparency of Lake Ladoga

Data on Secchi disk transparency in Lake Ladoga, the largest lake in Europe, collected between 1905 and 2003, were used to detect climatic (interannual) trends for lake regions with various depths. The seasonal variations in Secchi depth (D _s) during the ice-free period both for limnetic regions with large differences in bathymetric characteristics and for the whole lake were estimated by more than 7000 transparency measurements. The two-dimensional data sets have a spatial resolution of approximately 20 km and are geo-referenced by latitude and longitude in Lake Ladoga. Monthly mean spatial transparency distributions and their variances were calculated from May to October. The spatial distributions of the transparency for each month are discussed within the context of lake bathymetric patterns. The maximum values of Secchi depth (more than 4 m) occur during May and October in deep regions. Both the minimum mean value of water transparency and minimum horizontal gradients of D _s for the lake occur in August. The regions with significant interannual (climatic) decreasing trends of D _s have been identified. These areas increase in summertime and cover approximately half the lake area. In spring and autumn the areas decrease and occur in the southern near-shore regions. The mean downward climatic trend of water transparency in Lake Ladoga is 0.02 m/year.     

Adaptive neuro-fuzzy inference technique for estimation of light penetration in reservoirs

An adaptive neuro-fuzzy inference technique has been adopted to estimate light levels in a reservoir. The data were collected randomly from Doğanci Dam Reservoir over a number of years. The input data set is a matrix with vectors of time, depth, sampling location, and incident solar radiation. The output data set is a vector representing light measured at various depths. Randomization and logarithmic transformations have been applied as preprocessing. One-half of the data have been utilized for training; testing and validation steps utilized one-fourth each. An adaptive neuro-fuzzy inference system (ANFIS) has been built as a prediction model for light penetration. Very high correlation values between predictions and real values on light measurements with relatively low root mean square error values have been obtained for training, test, and validation data sets. Elimination of the overtraining problem was ensured by satisfying close root mean square error values for all sets.     

Predicting Secchi disk depth from average beam attenuation in a deep,ultra-clear lake

We addressed potential sources of error in estimating the water clarity of mountain lakes by investigating the use of beam transmissometer measurements to estimate Secchi disk depth. The optical properties Secchi disk depth (SD) and beam transmissometer attenuation (BA) were measured in Crater Lake (Crater Lake National Park, Oregon, USA) at a designated sampling station near the maximum depth of the lake. A standard 20 cm black and white disk was used to measure SD. The transmissometer light source had a nearly monochromatic wavelength of 660 nm and a path length of 25 cm. We created a SD prediction model by regression of the inverse SD of 13 measurements recorded on days when environmental conditions were acceptable for disk deployment with BA averaged over the same depth range as the measured SD. The relationship between inverse SD and averaged BA was significant and the average 95% confidence interval for predicted SD relative to the measured SD was ±1.6 m (range = −4.6 to 5.5 m) or ±5.0%. Eleven additional sample dates tested the accuracy of the predictive model. The average 95% confidence interval for these sample dates was ±0.7 m (range = −3.5 to 3.8 m) or ±2.2%. The 1996–2000 time-series means for measured and predicted SD varied by 0.1 m, and the medians varied by 0.5 m. The time-series mean annual measured and predicted SD’s also varied little, with intra-annual differences between measured and predicted mean annual SD ranging from −2.1 to 0.1 m. The results demonstrated that this prediction model reliably estimated Secchi disk depths and can be used to significantly expand optical observations in an environment where the conditions for standardized SD deployments are limited.     

Chemical stratification and partial meromixis in reservoirs in Tasmania

During the first summer after impoundment, chemical stratification occurred in four deep, steep-sided reservoirs of the Pieman River Power Development, Tasmania, under the influence of thermal stratification and anoxic hypolimnia caused by decaying vegetation in the flooded river valleys. Marked increases occurred in temperature, conductivity, pH, and in concentrations of dissolved iron, manganese, calcium, magnesium and bicarbonate in the sulphuretted, reducing, waters which accumulated as monimolimnetic pools adjacent to the dams. This partial, incipient meromixis persisted only in Lake Murchison, where a shallow monimolimnetic pool remained three years later. In the other reservoirs of the Pieman scheme it decayed after one or two years. Reservoir morphometry, degree of shelter, nature of major inflows, and alignment with respect to prevailing winds, are primary factors determining the persistence or eventual decay of chemical stratification in the respective impoundments. In Lake Barrington, another meromictic Tasmanian reservoir, the initial chemical gradient decayed and virtually disappeared, but was reestablished with greater severity than on any previous occasion. The severity of partial meromixis may wax and wane in relation to seasonal or longer-term meteorological events.     

Fish parasite communities in tropical reservoirs along the Perak River, Malaysia

The parasite communities of fish in three reservoirs (Temengor, Kenering and Cenderuh) along the Perak River, as well as in the lower Perak, are compared. A total of 36 species, 51 species, 61 species and 58 species of metazoan parasites from six types of fishes common in all studied locations, were obtained in Temengor, Kenering, Cenderuh Reservoirs, and downstream Perak River, respectively. The various criteria (prevalence, mean intensity, diversity index, similarity index and evenness) of the parasite community were highest at the Cenderuh Reservoir, followed by the downstream river, Kenering, and Temengor Reservoirs. Monogeneans were the most common parasites in all species of fish examined from all study sites. Fish of the same species showed a high degree of similarity of its parasite fauna regardless of study site, but different hosts had a low similarity of their parasite fauna, even within the same study site. This revised version was published online in August 2006 with corrections to the Cover Date.     

Standing crops of chironomidae and tubificidae in two desert reservoirs,Central Arizona

In the two desert reservoirs examined seasonal and spatial variations in both densities and biomasses of chironomid dipterans and tubificid oligochaetes were quite high, but mean values are comparatively low. Densities of both organisms were generally low in summer, larger in autumn, and highest in spring. Disjunct distribution of the two taxa was evident. Distribution of these animals with depth in these desert reservoirs is affected by hypolimnic oxygen depletion, food supply (Chlorophyll-a concentrations), lake morphology and perhaps by substrate composition and predator-prey interactions.     

Navigation by light polarization in clear and turbid waters

Certain terrestrial animals use sky polarization for navigation. Certain aquatic species have also been shown to orient according to a polarization stimulus, but the correlation between underwater polarization and Sun position and hence the ability to use underwater polarization as a compass for navigation is still under debate. To examine this issue, we use theoretical equations for per cent polarization and electric vector (e-vector) orientation that account for the position of the Sun, refraction at the air-water interface and Rayleigh single scattering. The polarization patterns predicted by these theoretical equations are compared with measurements conducted in clear and semi-turbid coastal sea waters at 2 m and 5 m depth over sea floors of 6 m and 28 m depth. We find that the per cent polarization is correlated with the Sun's elevation only in clear waters. We furthermore find that the maximum value of the e-vector orientation angle equals the angle of refraction only in clear waters, in the horizontal viewing direction, over the deeper sea floor. We conclude that navigation by use of underwater polarization is possible under restricted conditions, i.e. in clear waters, primarily near the horizontal viewing direction, and in locations where the sea floor has limited effects on the light's polarization.     

The occurrence of Campylobacter subtypes in environmental reservoirs and potential transmission routes

AIM: To identify potential reservoirs and transmission routes of human pathogenic Campylobacter spp. METHODS AND RESULTS: An enrichment PCR method for the detection and identification of Campylobacter jejuni and/or Campylobacter coli in faecal, food and river water samples was applied to 1450 samples of 12 matrix types obtained from a defined geographical area. PCR-positive samples were cultured to yield isolates for typing, and the data for 616 C. jejuni isolates obtained. Serotyping and SmaI macrorestriction profiling using pulsed field gel electrophoresis revealed a high level of diversity within the isolates from each matrix. Campylobacter jejuni and C. coli subtypes indistinguishable from those obtained from human cases were detected in most of the matrices examined. No Campylobacter isolates were isolated from possum faeces. CONCLUSIONS: Ten of the 12 matrices examined may be involved in the transmission of human campylobacteriosis as they contained Campylobacter subtypes also isolated from clinical cases. SIGNIFICANCE AND IMPACT OF THE STUDY: Results indicate that, for this rural population, a range of potential transmission routes that could lead to campylobacteriosis exist. Their relative importance needs to be assessed from an exposure assessment standpoint.     

Fish mercury levels in relation to characteristics of hydroelectric reservoirs in Newfoundland, Canada

Mercury levels in fish have been demonstrated to increase after impoundment with augmented levels of mercury predicted to decline as the reservoir ages. Previous research in Newfoundland predicted return rates in the order of 10 to 12 years for landlocked Atlantic salmon or ouananiche (Salmo salar) and 7 years for brook trout (Salvelinus fontinalis). In order to test the validity of these predictions on a broader spatial and temporal scale, and develop more generally predictive models, mercury levels in three fish species were studied in 16 older Newfoundland hydroelectric reservoirs of various age (32 to 95 years) and area flooded (21 to 13,000 ha).Mercury concentrations were standardized to fish length and correlated with physical, chemical, and biological characteristics of the sampling sites. Standard length mercury levels ranged from 0.23 to 0.86 ppm in ouananiche, 0.13 to 0.59 ppm in brook trout, and 0.22 to 0.72 in arctic charr (Salvelinus alpinus). Fish in excess of the Canadian Safety Limit (0.5 ppm) were collected from 14 of 16 sites for ouananiche, 8 of 17 sites for brook trout, and 3 of 7 sites for arctic charr, including control lakes. Standard length fish mercury levels were correlated with reservoir age and (log₁₀) area flooded for ouananiche and with pH for arctic charr. A multiple regression model was developed relating standard length mercury in ouananiche with reservoir age and log₁₀ of the flooded area. There were no apparent relationship between reservoir characteristics and brook trout mercury concentrations. Based on this analysis, it is not possible, at present, to develop generally predictive models for all species found in Newfoundland impoundments.     

螺旋藻细胞培养与光能利用的关系

对钝顶螺旋藻(Spirulina platensis Geitler)细胞培养体系的光衰减以及连续培养条件下藻细胞生长对光能的利用特性进行了分析,结果表明改进的Lambert-Beer定律I=I0exp(-αxL)可较好地描述细胞浓度及光程对光衰减的综合影响;引入平均光强和细胞平均比消光量概念,借鉴Monod方程形式,较好地描述了它们与比生长速率之间的关系,并求得最大比生长速率μm、光强半饱和参数kI、光能维持系数m和得率系数YG分别为μm=1.75/d,kI=1.453×10     

The influence of biomass and structure of the crustacean plankton on the water transparency in the Saidenbach storage reservoir

Planktonic crustacean biomass as well as structure are important factors influencing water transparency. The significant dependence of the water quality (Secchi depth) on the concentration and the share of the Daphnia biovolume and not on the total Crustacea biovolume in the Saidenbach reservoir indicates that the density of the Crustacea is only a measure of the cleaning performance, if Daphnia dominates. Using the mean size, the influence of the crustacean structure on the Secchi depth can be recorded. If big size categories prevail (like Daphnia) the water transparency is high. The mainly occurrence of little species (Mesocyclops, Bosmina) results in lower Secchi depths. However, a well defined (significant) relationship is being prevented by the different feeding behaviour of the several species.     

Patterns in the composition and richness of helminth communities in brown trout, Salmo trutta, in a group of reservoirs

Helminth community composition and richness were studied in brown trout, Salmo trutta , in 10 reservoirs of broadly similar age and characteristics situated close to each other in a well-defined region of south-west England. Communities were compared using cluster and ordination analyses, and possible correlations between helminth richness and a number of environmental variables were investigated. The hypothesis that the helminth communities should show high degrees of similarity and that large differences between reservoirs and a high degree of clustering would be unrecognizable was refuted. Levels of community similarity were low and comparable to those determined for helminths in salmonids in natural lakes. Trout in some reservoirs exhibited very distinctive helminth faunas and clustering of reservoirs was apparent. No single factor, including reservoir size and presence of piscivorous birds, had a predominant influence on community richness or composition but rather a multiplicity of local factors was believed to influence these parameters. The results indicate that local factors promoting distinctiveness have a greater influence on the composition and richness of fish helminth communities in lakes and reservoirs than do regional factors promoting similarity.     

Factors which affect the abundance of an invasive cladoceran, Daphnia lumholtzi, in U.S. reservoirs

1.  Daphnia lumholtzi is a subtropical, Old World species which is rapidly spreading throughout reservoirs in the southern U.S.A. It was first recorded in Lake Texoma (Oklahoma–Texas) in September 1991.
2. Southern U.S. reservoirs typically have strong spatial and temporal gradients in temperature, conductivity, turbidity and in the distribution of organisms. Therefore, the present experiments examined the reproductive and moulting rates, and survival of D . lumholtzi in relation to extremes of food concentration, temperature, conductivity and turbidity.
3. Increases in temperature (range = 15–29 °C) and decreases in turbidity (range = 0.6–470 NTU) increased reproductive and moulting rates, whereas food concentration only affected the rate of reproduction, while conductivity had no effects. Survival was affected only by temperature.
4.  Daphnia lumholtzi tolerates high temperatures (27–30 °C) at which other cladocerans in Lake Texoma disappear. Therefore, D . lumholtzi may exploit resources in midsummer, when there are few potential competitors.     

Nutrients,light and primary production by phytoplankton and microphytobenthos in the eutrophic,turbid Westerschelde estuary (The Netherlands)

Abiotic factors and primary production by phytoplankton and microphytobenthos was studied in the turbid Westeschelde estuary. Because of the high turbidity and high nutrient concentrations primary production by phytoplankton is light-limited. In the inner and central parts of the estuary maximum rates of primary production were therefore measured during the summer, whereas in the more marine part spring and autumn bloom were observed. Organic loading is high, causing near anaerobic conditions upstream in the river Schelde. Because of this there were no important phytoplankton grazers in this part of the estuary and hence the grazing pressure on phytoplankton was minimal. As this reduced losses, biomass is maximal in the river Schelde, despite the very low growth rates.On a number of occasions, primary production by benthic micro-algae on intertidal flats was studied. Comparison of their rates of primary production to phytoplankton production in the same period led to the conclusion that the contribution to total primary production by benthic algae was small. The main reason for this is that the photosynthetic activity declines rapidly after the flats emerged from the water. It is argued that CO₂-limitation could only be partially responsible for the noticed decrease in activity.     

The control of diatom and cyanobacterial blooms in reservoirs using barley straw

A potable supply reservoir, with a long history of diatom blooms in spring and cyanobacterial blooms in summer, was treated with barley straw in March 1993 with subsequent additions in December 1993 and June 1994. Within two months of the initial treatment, algal numbers started to fall compared with previous years and have remained consistently lower throughout 1993 and 1994. Cyanobacteria have not bloomed and cell numbers remained low. Chemical analysis of the water showed locally elevated concentrations of geosmin close to the straw on one occasion but the overall concentration of this and a range of other organic molecules remained within acceptable limits and at concentrations similar to those found in other untreated reservoirs in the region. Observed and potential advantages to public health and potable supply management resulting from the use of barley straw are discussed.