Impact of acidification on diatoms and chemistry of Dutch moorland pools

Old (ca 1920) and recent (1978) diatom assemblages from sixteen pristine moorland pools are compared by analysis of pH-spectra, diversity (Hill's index), (dis)similarity (number of species in common, Dyer dissimilarity) and principal component analysis. The pH-spectra of clear water pools indicate that the formerly wide range of pH (4–6) is very narrow now (3.7–4.6). No significant change of pH (ca 4.5) is observed in brown water moorland pools. Diversity significantly declines in clear water pools and has a tendency to rise in brown water pools. The number of species in common does not change. The Dyer dissimilarity significantly decreases in clear water lakes, no change is found in brown water lakes. The first principal component (PC 1) explains 61% of total variance between samples and is nearly completely determined byEunotia exigua. PC 1 has a strong positive correlation with both the absolute and relative sulfate concentration and other factors related to acidification (Ca²⁺, Al³⁺, Mg²⁺, electrical conductivity). PC1 has a negative correlation with factors characterizing humic acid waters (K MnO₄-consumption, Fe, (Na⁺ + K⁺)/ (Ca²⁺+Mg²⁺) etc.). Old samples have low scores on PC 1. Recent samples from clear waters have high scores on PC 1. The original variation, caused by regional factors, is replaced by a sulfate controled variation. The factors which are responsible for the recent differences in sulfate concentrations between pools are discussed (sulfate reduction, accumulation by dry deposition in adjacent pine forests and drought). Some observations contribute to the opinion that acidification may be considered as eutrophication and not as oligotrophication.     

Acidification of freshwaters by red soil in a subtropical silicate rock area,Okinawa, Japan

Two samples of red soil, one from Gushikawa Recreation Center (GRC) and one from Okinawa Royal Golf Club (ORGC), were examined for particle size distribution, textures, minerals, and chemical compositions. The effects of particle size and grinding of clay minerals on pH, electrical conductivity (EC), and dissolved chemical species were studied in deionized water and river water. The results of red soil solutions were compared with those of acidic waters found in red soil dominated areas. The minimum pH values of soil solutions extracted by deionized water were 4.38–5.36 and 5.16–5.89 and the maximum values of EC were 4.91–16.98mSm^–1 and 3.54–11.23mSm^–1 for GRC and ORGC, respectively. In the river water samples equilibrated with red soils, the minimum pH values were 4.48–5.10 and 4.77–5.91 and the maximum EC values were 19.6–34.2mSm^–1 and 17.5–25.0mSm^–1 for GRC and ORGC, respectively. The values of pH and EC varied with the soil–solution ratio and the particle size. The chemical composition of river water without mixing with red soil shows Na⁺K⁺ and Ca²⁺Mg²⁺. After mixing with red soil, the trend of the concentrations changed to Na⁺K⁺ and Mg²⁺Ca²⁺, which is the same as that of soil solutions in deionized water as well as that of acidic waters found in the red soil area. The pH of the acidic waters was 4.95–5.81 and EC was 7.76–30.0mSm^–1. Laboratory experimental results agreed well with those found in the field in terms of trend of concentrations of the chemical species and pH. Therefore, the results of this study suggest that the low pH and trend of the concentrations of chemical species of the acidic waters found in the red soil dominated areas were the result of the interaction of natural water and red soil.     

Aquatic Hyphomycetes in Polluted Groundwater Habitats of Central Germany

Polluted groundwater wells located in a former copper shale mining district (11 sites; Mansfelder Land, Central Germany) and in meadows of the Mulde and Elbe rivers (2 sites) were assessed for occurrence and species richness of aquatic hyphomycetes. Water temperatures at all sites were relatively low and fluctuated less than in surface waters. Oxygen concentrations were always below saturation, whereas sulfate, nitrate, and phosphate levels reached extremely high values in several of the wells. Relatively high levels of Pb, Mn, and Fe were found in some of the wells, but overall few concentrations of individual metals and metalloids exceeded European guidelines for drinking water. Pollen tube growth inhibition, used to assess cytotoxicity of the water, ranged between 4 and 50%. Between 1 and 10 distinct species of aquatic hyphomycetes colonized sterile Alnus glutinosa leaves exposed at the Mansfelder Land sites; for the meadow sites, 8-20 species were found. Heliscus lugdunensis and Anguillospora sp. were the two most widespread species. Fungal colonization occurred much more slowly than in surface water, as demonstrated by scanning electron microscopy and the release of conidia from recovered leaves. The conidial output from exposed alder leaves ranged from 0.2 to 95 conidia mg (-1) dry mass, corresponding to 10% of the values for contaminated surface waters in the same region. Overall, groundwater appears to be a marginal habitat for aquatic hyphomycetes, but may nevertheless play a vital role as long-term reservoir facilitating rapid recolonization following a collapse in fungal communities in surface waters.     

Formation and volatilisation of alkyl-iodidesand -selenides in macrotidal estuaries

The occurrence of alkylated volatile iodide andselenide species was evidenced and investigatedin water, sediments and overlying atmosphere ofthree major European estuaries, such as theGironde (F), the Rhine (NL) and the Scheldt(B/NL), along with the salinity gradient. Foriodine, up to eight volatile species wereobserved as alkyl-iodides in estuarine waters.The major one (ca. 40%) was methyl-iodide(MeI) with average seasonal concentrationsranging from 1 to 100 pmol l^–1. Otherspecies observed were found to correspond toseveral halomethane derivatives and lightalkyl-iodide species. For selenium, dimethylselenide (Me₂Se) was the main compound(ca. 90%) over three methyl-selenidesencountered in estuarine waters. Me₂Seaverage seasonal concentrations were found torange between 0.2 and 100 pmol l^–1 in thewater column. The occurrence of methylatediodides and selenides seems to be mainlyrelated to the algae's biomass turnover asindicated by photosynthetic pigment tracers(i.e. chlorophyll a and phaeopigments) andseasonal variation of surface waterconcentrations. The production and release ofgaseous iodide and selenide compounds may thenresult from natural biological pathways leadingto the methylation of their inorganic form.Finally, significant volatilisation rates wereevaluated leading to average seasonal fluxrates for total volatile iodide and selenidecompounds ranging from 4 to 100 and from 1 to75 nmol m^–2 d^–1, respectively.Estuarine mass balance estimated from MeI andMe₂Se distributions indicates thatvolatilisation to the atmosphere represents aprimary sink for MeI and Me₂Se fromestuarine surface waters.     

Gelatinous zooplankton of the Arctic Ocean: in situ observations under the ice

The gelatinous zooplankton of the Canada Basin were observed with a deep-diving remotely operated vehicle (ROV) during August–September, 2002. Taxa observed fell into four main groups: cnidarians, ctenophores, chaetognaths, and pelagic tunicates. We provide detailed data on the vertical distributions of many taxa from three sites which span the Canada Basin. The most common gelatinous organisms in the surface waters were the ctenophores Mertensia ovum and Bolinopsis infundibulum. These two species were found in very large numbers in the near-surface mixed layer. In the mesopelagic zone, below the transition from the Pacific water layer and the Atlantic water layer, the most common species was Sminthea arctica. Surprising numbers of the scyphomedusa Atolla tenella were found in the deep waters of the basin, along with an undescribed species of narcomedusae. The vertical distributions of the gelatinous zooplankton observed with the ROV show several trends related to the physical properties of the water and geographic location within the basin.     

The Effects of Infrared Loading and Water Table on Soil Energy Fluxes in Northern Peatlands

Increased radiative forcing is an inevitable part of global climate change, yet little is known of its potential effects on the energy fluxes in natural ecosystems. To simulate the conditions of global warming, we exposed peat monoliths (depth, 0.6 m; surface area, 2.1 m²) from a bog and fen in northern Minnesota, USA, to three infrared (IR) loading (ambient, +45, and +90 W m^–2) and three water table (–16, –20, and –29 cm in bog and –1, –10 and –18 cm in fen) treatments, each replicated in three mesocosm plots. Net radiation (Rn) and soil energy fluxes at the top, bottom, and sides of the mesocosms were measured in 1999, 5 years after the treatments had begun. Soil heat flux (G) increased proportionately with IR loading, comprising about 3%–8% of Rn. In the fen, the effect of IR loading on G was modulated by water table depth, whereas in the bog it was not. Energy dissipation from the mesocosms occurred mainly via vertical exchange with air, as well as with deeper soil layers through the bottom of the mesocosms, whereas lateral fluxes were 10–20-fold smaller and independent of IR loading and water table depth. The exchange with deeper soil layers was sensitive to water table depth, in contrast to G, which responded primarily to IR loading. The qualitative responses in the bog and fen were similar, but the fen displayed wider seasonal variation and greater extremes in soil energy fluxes. The differences of G in the bog and fen are attributed to differences in the reflectance in the long waveband as a function of vegetation type, whereas the differences in soil heat storage may also depend on different soil properties and different water table depth at comparable treatments. These data suggest that the ecosystem-dependent controls over soil energy fluxes may provide an important constraint on biotic response to climate change.     

Effects of ecological engineered oxygenation on the bacterial community structure in an anoxic fjord in western Sweden

Oxygen-depleted bodies of water are becoming increasingly common in marine ecosystems. Solutions to reverse this trend are needed and under development, for example, by the Baltic deep-water OXygenation (BOX) project. In the framework of this project, the Swedish Byfjord was chosen for a pilot study, investigating the effects of an engineered oxygenation on long-term anoxic bottom waters. The strong stratification of the water column of the Byfjord was broken up by pumping surface water into the deeper layers, triggering several inflows of oxygen-rich water and increasing oxygen levels in the lower water column and the benthic zone up to 110 μmol l⁻¹.We used molecular ecologic methods to study changes in bacterial community structure in response to the oxygenation in the Byfjord. Water column samples from before, during and after the oxygenation as well as from two nearby control fjords were analyzed. Our results showed a strong shift in bacterial community composition when the bottom water in the Byfjord became oxic. Initially dominant indicator species for oxygen minimum zones such as members of the SUP05 clade declined in abundance during the oxygenation event and nearly vanished after the oxygenation was accomplished. In contrast, aerobic species like SAR11 that initially were restricted to surface waters could later be detected deep into the water column. Overall, the bacterial community in the formerly anoxic bottom waters changed to a community structure similar to those found in oxic waters, showing that an engineered oxygenation of a large body of anoxic marine water is possible and emulates that of a natural oxygenation event.     

Barley yield under saline water cultivation

Summary In a microplot experiment conducted during the winter seasons of 1979–80 and 1980–81 on a sandy loam soil in the semi-desert tract, the accumulation of salts was found to be highest in March after harvest of the barley crop grown with saline water of EC values ranging from 2.2 to 24 mmhos/cm. The average EC of saturation extract of the surface soil layer (0–15 cm) was 0.79 times that of the applied irrigation water at the time of crop harvest, however, accumulated salts of the winter season were leached by the following monsoon rains. The average SAR of saturation extract of soil was 1.5 times that of the irrigation water in March but quite low in November. Highly significant correlations, (+0.90 to 0.99) at the post irrigated period between ECse of soils and EC of waters and SARse of soils and SAR of waters have been observed. Barley could be grown economically with irrigation water upto EC 16 mmhos/cm; however an average reduction in grain yield or not more than 43.5% compared to the yield under irrigation with tube well water of EC 2.2 mmhos/cm, was obtained. The starch, N and P contents decreased and that of K and Na increased in the grain with the use of saline waters. The performance of DL-85 variety was best and its K/Na ratio was also higher than that of other tested varieties.     

Distribution of four narrowly endemic Niphargus species (Crustacea: Amphipoda) in the western Dinaric region with description of a new species

The distribution of four morphologically similar and narrowly endemic Niphargus species living mainly in surface waters of the western Dinaric region was studied. The study area consists of limestone and marls-sandstone (flysch) patches. The variable chemical structure of the flysch affects water conductivity and carbonatic hardness. N. timavi inhabits surface and subterranean waters of low conductivity and carbonatic hardness, both on limestone and flysch. N. spinulifemur is restricted to surface waters with high conductivity and higher carbonatic hardness, exclusively on flysch areas. N. vinodolensis sp. n., described herein, lives both on karst and flysch, where waters exhibit intermediate values of conductivity and carbonatic hardness. N. krameri inhabits surface and subterranean waters with high conductivity and high carbonatic hardness, both on limestone and flysch. This species is in the course of morphological differentiation with three morphological races, probably due to low dispersal ability. The studied species probably do not constitute a monophylum. The easternmost species, N. vinodolensis shows (morphologically, molecularly) close relations with the northeast-Italian N. elegans and with middle-Dalmatian N. illidzensis dalmatinus. It is possible that they differentiated from a common ancestor which inhabited the dry bottom of the northern Adriatic, exposed during the last glacial. We assume that the reasons for the high degree of endemism are historical changes of hydrographical regimes and sea transgressions–regressions. Poor migratory abilities in a geologically diverse landscape restricted further dispersal.     

Semiterrestrial meiofauna inhabiting a wet campo in central Brazil, with special reference to the Copepoda (Crustacea)

The wet campo (campo úmido) marsh type is widely distributed in the cerrado region of central Brazil. These marshes develop on slopes along margins of gallery forests where the water table persists at or near the soil surface year-round. Their grass and sedge vegetation covers spongy, highly organic (not peaty) soils. Ground and surface water seeping through the wet campos tends to be slightly acidic (pH about 5), ion-poor (conductivity less than 10 µS cm^–1) and well oxygenated.A typical freshwater meiofaunal community develops in those wet campos where soils remain moist throughout the year (moisture content more than about 60% of soil wet weight). Such a community was studied from 1979–1982 in a wet campo in a protected natural area on the Fazenda Água Limpa of the Universidade de Brasília. It was dominated by nematodes, rotifers and harpacticoid copepods, and included protozoans, turbellarians, cyclopoid copepods, cladocerans, ostracods, oligochetes, hydracarines and several families of aquatic insect larvae. This community was most fully developed in the wetter areas.Species richness of the copepod community is the highest yet recorded in a freshwater system. The 29 species of harpacticoid copepods and 4 species of cyclopoid copepods displayed pronounced zonation which seemed best correlated with soil moisture content and water regime.     

Assessment of potential sources of protozoan contamination between two avian feeding guilds in a conservation area

Occasional screening of food and water quality available to organisms in protected areas could be beneficial to their successful conservation. This is important for areas receiving regular human visitors and exhibiting activities that may be detrimental to ecosystem health. This study determined the intestinal protozoan species harboured by insectivorous and granivorous birds within the Jos Wildlife Park, Nigeria and whether the two avian feeding guilds are more susceptible to protozoan infection through water or food (grass seeds and insects). Special boxes were used to collect faecal samples from trapped birds. Samples were later analysed in the laboratory for protozoans. Both food and water utilised by the birds in the area were microscopically screened. The composition and abundance of intestinal protozoans between the two feeding guilds did not show significant differences. However, considering parasite species individually, the degree of infection by protozoans such as Giardia lamblia was highly related to the range of infection sources that a feeding guild was exposed to. The composition of parasites observed in the two feeding guilds was strongly linked to both water bodies and avian diet obtainable in the Park. These observations showed that birds in the Park are orally susceptible to infection with protozoans, some of which have been reported to cause health implications in birds. Thus, any measure to curtail environmental contamination by the parasites may improve ecosystem health and survival of avian species in the Park.     

Total organochlorine and organobromine in Finnish water courses

Methods were developed for analyzing total organochlorine (TOCl) and total organobromine (TOBr) in different kinds of water, sediment and biological samples. Sediment samples were extracted with alkaline propanone and biological samples with a neutral propanone + water solution. Neutron activation analysis (NAA) was used for the halogen determination. The detection limits for TOCl and TOBr are respectively 5 and 0.5 µg l^–1 for water (sample size 100 ml) and 0.3 and 0.1 µg g^–1 dw (sample size 1 g) for sediment and biological samples. Recoveries for common organochlorine compounds were usually over 90%.TOCl concentrations measured in waters in a natural condition were below 15 µg l^–1; and in polluted waters, from 100 to 500 µg l^–1, and occasionally to 2000 µg l^–1. TOBr concentrations were generally well below 10 µg 1^–1.     

Evaluation of F+ RNA and DNA Coliphages as Source-Specific Indicators of Fecal Contamination in Surface Waters

Male-specific (F+) coliphages have been investigated as viral indicators of fecal contamination that may provide source-specific information for impacted environmental waters. This study examined the presence and proportions of the different subgroups of F+ coliphages in a variety of fecal wastes and surface waters with well-defined potential waste impacts. Municipal wastewater samples had high proportions of F+ DNA and group II and III F+ RNA coliphages. Bovine wastewaters also contained a high proportion of F+ DNA coliphages, but group I and IV F+ RNA coliphages predominated. Swine wastewaters contained approximately equal proportions of F+ DNA and RNA coliphages, and group I and III F+ RNA coliphages were most common. Waterfowl (gull and goose) feces contained almost exclusively F+ RNA coliphages of groups I and IV. No F+ coliphages were isolated from the feces of the other species examined. F+ coliphage recovery from surface waters was influenced by precipitation events and animal or human land use. There were no significant differences in coliphage density among land use categories. Significant seasonal variation was observed in the proportions of F+ DNA and RNA coliphages. Group I F+ RNA coliphages were the vast majority (90%) of those recovered from surface waters. The percentage of group I F+ RNA coliphages detected was greatest at background sites, and the percentage of group II F+ RNA coliphages was highest at human-impacted sites. Monitoring of F+ coliphage groups can indicate the presence and major sources of microbial inputs to surface waters, but environmental effects on the relative occurrence of different groups need to be considered.     

Microbial diversity in arctic freshwaters is structured by inoculation of microbes from soils

Microbes are transported in hydrological networks through many environments, but the nature and dynamics of underlying microbial metacommunities and the impact of downslope inoculation on patterns of microbial diversity across landscapes are unknown. Pyrosequencing of small subunit ribosomal RNA gene hypervariable regions to characterize microbial communities along a hydrological continuum in arctic tundra showed a pattern of decreasing diversity downslope, with highest species richness in soil waters and headwater streams, and lowest richness in lake water. In a downstream lake, 58% and 43% of the bacterial and archaeal taxa, respectively, were also detected in diverse upslope communities, including most of the numerically dominant lake taxa. In contrast, only 18% of microbial eukaryotic taxa in the lake were detected upslope. We suggest that patterns of diversity in surface waters are structured by initial inoculation from microbial reservoirs in soils followed by a species-sorting process during downslope dispersal of both common and rare microbial taxa. Our results suggest that, unlike for metazoans, a substantial portion of bacterial and archaeal diversity in surface freshwaters may originate in complex soil environments.     

Hydrologic and Vegetative Removal of Cryptosporidium parvum,Giardia lamblia,and Toxoplasma gondii Surrogate Microspheres in Coastal Wetlands

Constructed wetland systems are used to reduce pollutants and pathogens in wastewater effluent, but comparatively little is known about pathogen transport through natural wetland habitats. Fecal protozoans, including Cryptosporidium parvum, Giardia lamblia, and Toxoplasma gondii, are waterborne pathogens of humans and animals, which are carried by surface waters from land-based sources into coastal waters. This study evaluated key factors of coastal wetlands for the reduction of protozoal parasites in surface waters using settling column and recirculating mesocosm tank experiments. Settling column experiments evaluated the effects of salinity, temperature, and water type (“pure” versus “environmental”) on the vertical settling velocities of C. parvum, G. lamblia, and T. gondii surrogates, with salinity and water type found to significantly affect settling of the parasites. The mesocosm tank experiments evaluated the effects of salinity, flow rate, and vegetation parameters on parasite and surrogate counts, with increased salinity and the presence of vegetation found to be significant factors for removal of parasites in a unidirectional transport wetland system. Overall, this study highlights the importance of water type, salinity, and vegetation parameters for pathogen transport within wetland systems, with implications for wetland management, restoration efforts, and coastal water quality.     

Diffusive exchange of linear alkylbenze suifonates (LAS) between overlying water and bottom sediment

Linear alkylbenzenesulfonate (LAS) was detected in a 0–30 cm deep sediment column collected in Lake Teganuma (one of the most polluted lakes in Japan). The range of the LAS concentration in sediments was between 0.1 and 500 µg g^–1 (C₁₁-C₁₄ homologs per dry solid) and its vertical profile showed a seasonal variation. A mathematical model, which includes a diffusion term and a biodegradation term, was used to simulate the temporal variation of LAS in the sediment column and to calculate the diffusive flux rate of LAS across the sediment/water interface. An averaged diffusion coefficient of 2.4 × 10^–5 cm² s^–1 for the sediment interstitial water was obtained from sediment core samples located in Lake Teganuma. The biodegradation rate constant (0.002 d^–1) of LAS in the sediment obtained from the model analysis was considerably less than that reported for LAS in anaerobic waters. These results confirm that a model describing diffusive transport and biodegradation of LAS in the sediments can simulate the temporal variation of LAS in near surface sediments. The diffusive flux rate from overlying water to bottom sediment was calculated to be between –0.20 and 0.52 (C₁₁-C₁₄ LAS) mg m^–2 h^–1 and the annual net flux rate was 0.7 g m^–2 y^–1.     

Survival of allochthonous bacteria in still mineral water bottled in polyvinyl chloride (PVC) and glass

The mortality of Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae and Pseudomonas aeruginosa, based on the culturability of these bacteria, was assessed in non-carbonated mineral water, bottled in polyvinyl chloride (PVC) containing the indigenous flora, sterile mineral water bottled in PVC, sterile mineral water in glass containers, and sterile tap water in glass containers. There was a general decrease in the culturability of these organisms in the four test waters, except that Ps. aeruginosa grew in sterile tap water. Escherichia coli and Kl. pneumoniae had the highest mortality rates under the conditions tested, while Ent. cloacae had a very low and constant mortality rate that would have resulted in the persistence of this organism in mineral water for a long period of time. After a sharp initial decrease in culturability, Ps. aeruginosa also had a very low mortality rate in mineral water bottled in PVC.     

Superficial and hyporheic oligochaete communities as indicators of pollution and water exchange in the River Moselle, France

Benthic oligochaetes were sampled on three occasions (June, August and October 1992) in the upper (0–10 cm) and hyporheic (35–45 cm depths) sediments at five sites of the River Moselle, from upstream of the town of Epinal to Velle-sur-Moselle. The first site (upstream from Epinal) is considered as unpolluted and the four remaining sites are polluted by industrial effluents. The most polluted stations were generally dominated by the pollution tolerant taxon Limnodrilus. Numbers of individuals of this taxon decreased at the less polluted last site in recovery zone, and were also scarce in the first unpolluted site. It is noteworthy that these tendencies were observed in both superficial and hyporheic substrates and to the greatest degree in hyporheic ones. At the unpolluted site, the hyporheic habitat is dominated by the groundwater species Propappus volki, Pristina spp., Pristinella spp. At the less polluted site (last site), the deep sediments are dominated by groundwater species and the Tubificidae without hair setae decrease from June to October. As a result of water exchange between superficial and subterranean waters, superficial substrates of the first and the last stations tend to be colonised by a high proportion of hyporheic species that suggests that flow is primarily from subterranean to superficial waters. The contrary is the case at other polluted stations which are characterised by the invasion of hyporheic substrates by the pollution tolerant superficial taxa Limnodrilus. This suggests that water flows from the river to the deeper groundwater. These two stations are located near drinking water plants which utilise groundwater, thus increasing the vulnerability of groundwater to surface contaminants.     

Benthic foraminiferal distribution and abundance changes in Skagerrak surface sediments: 1937 (Höglund) and 1992/1993 data compared

Both living (stained) and dead (unstained) foraminiferal assemblages from surface sediments (0–2 cm) in the northwestern part of the Skagerrak have been studied in order to (1) define and characterize the distribution of various modern benthic environments and (2) by comparing these findings with surface samples collected 40–60 years ago, to document possible faunal changes that might have occurred. The investigated area is physiographically divided into the Norwegian slope, the Skagerrak Basin, and the Danish slope. The latter is under the influence of the Jutland Current, while the basin and the investigated parts of the Norwegian slope are bathed in Atlantic water. All areas have bottom waters with a high oxygen concentration. Three living (stained) and three dead (unstained) assemblages occupy the three physiographic areas. Only one assemblage (on the Norwegian slope) is common to both the living and dead assemblages but the boundaries between them lie at comparable depths. The higher standing crops are found on the fertile Danish slope while the lower ones are in the deep basin where the diversity is at a maximum. In the dead assemblages, the relative abundance of agglutinated tests increases with depth. Comparison with data collected 40 to 60 years ago shows increases in absolute numbers of tests, especially in the deep basin. There are changes in assemblage compositions in all areas. The dominant species found in 1937 are different from those of 1992/1993. There is a major change in the basin where one agglutinated species has changed its depth distribution downslope and two present day abundant species are new arrivals. These faunal events are probably linked to environmental changes.     

Use of a Sentinel System for Field Measurements of Cryptosporidium parvum Oocyst Inactivation in Soil and Animal Waste

A small-volume sentinel chamber was developed to assess the effects of environmental stresses on survival of sucrose-Percoll-purified Cryptosporidium parvum oocysts in soil and animal wastes. Chambers were tested for their ability to equilibrate with external chemical and moisture conditions. Sentinel oocysts were then exposed to stresses of the external environment that affected their viability (potential infectivity), as indicated by results of a dye permeability assay. Preliminary laboratory experiments indicated that temperatures between 35 and 50°C and decreases in soil water potential (−0.003 to −3.20 MPa) increased oocyst inactivation rates. The effects of two common animal waste management practices on oocyst survival were investigated on three dairy farms in Delaware County, N.Y., within the New York City watershed: (i) piling wastes from dairy youngstock (including neonatal calves) and (ii) spreading wastes as a soil amendment on an agricultural field. Sentinel containers filled with air-dried and sieved (2-mm mesh) youngstock waste or field soil were wetted and inoculated with 2 million oocysts in an aqueous suspension and then placed in waste piles on two different farms and in soil within a cropped field on one farm. Controls consisted of purified oocysts in either phosphate-buffered saline or distilled water contained in sealed microcentrifuge tubes. Two microdata loggers recorded the ambient temperature at each field site. Sentinel experiments were conducted during the fall and winter (1996 to 1997) and winter (1998). Sentinel containers and controls were removed at 2- to 4-week intervals, and oocysts were extracted and tested by the dye permeability assay. The proportions of potentially infective oocysts exposed to the soil and waste pile material decreased more rapidly than their counterpart controls exposed to buffer or water, indicating that factors other than temperature affected oocyst inactivation in the waste piles and soil. The effect of soil freeze-thaw cycles was evident in the large proportion of empty sentinel oocysts. The potentially infective sentinel oocysts were reduced to <1% while the proportions in controls did not decrease below 50% potentially infective during the first field experiment. Microscopic observations of empty oocyst fragments indicated that abrasive effects of soil particles were a factor in oocyst inactivation. A similar pattern was observed in a second field experiment at the same site.