Density Of Protozoa Research Articles

Toxicity and Bioaccumulation of Lead in Marine Protozoa Communities

The toxicity and bioaccumulation of lead has been studied using marine protozoa communities developed in laboratory microecosystems. The concentrations tested were 500 and 1000 μg · L−1of lead as lead acetate. The protozoan was able to bioaccumulate 27.02–504 μg Pb · g−1dry weight. Bacteria also bioaccumulated lead, but always to a lesser degree than protozoa. Lead caused a significant reduction in the density of protozoa, which could be an indirect response to the cellular increase of lead. On the other hand, the toxicant did not determine a decrease in the number of bacterial cells; this could be due to their capacity to bioaccumulate a lesser amount of lead, the increase in the number of dead cells, and the elimination of their predators by the toxicant. After 120 h, a recovery of the community was observed.

Response of soil biota to elevated atmospheric CO2 in poplar model systems.

We tested the hypotheses that increased belowground allocation of carbon by hybrid poplar saplings grown under elevated atmospheric CO2 would increase mass or turnover of soil biota in bulk but not in rhizosphere soil. Hybrid poplar saplings (Populus×euramericana cv. Eugenei) were grown for 5 months in open-bottom root boxes at the University of Michigan Biological Station in northern, lower Michigan. The experimental design was a randomized-block design with factorial combinations of high or low soil N and ambient (34 Pa) or elevated (69 Pa) CO2 in five blocks. Rhizosphere microbial biomass carbon was 1.7 times greater in high-than in low-N soil, and did not respond to elevated CO2. The density of protozoa did not respond to soil N but increased marginally (P < 0.06) under elevated CO2. Only in high-N soil did arbuscular mycorrhizal fungi and microarthropods respond to CO2. In high-N soil, arbuscular mycorrhizal root mass was twice as great, and extramatrical hyphae were 11% longer in elevated than in ambient CO2 treatments. Microarthropod density and activity were determined in situ using minirhizotrons. Microarthropod density did not change in response to elevated CO2, but in high-N soil, microarthropods were more strongly associated with fine roots under elevated than ambient treatments. Overall, in contrast to the hypotheses, the strongest response to elevated atmospheric CO2 was in the rhizosphere where (1) unchanged microbial biomass and greater numbers of protozoa (P < 0.06) suggested faster bacterial turnover, (2) arbuscular mycorrhizal root length increased, and (3) the number of microarthropods observed on fine roots rose.

The diversity status of freshwater protozoans and the pollution stress on protozoa in China

The present paper introduced a broad outline of the diversity of protozoa on the globe, the position in the biology and the relation to the human being. Considering that the protozoa in freshwater as an aggregate group ecologically, its diversity and stress could be discussed. The stress resulting from anthropogenic sources in an eutrophication lake—Donghu Lake in a period of half a century resulted in a ten fold increase of protozoan density and a succession of dominant species. The industrial pollution from the bank of the Three Gorges Area of the Yangtze River damaged at least 70% species of protozoans. In the largest tributary of the Yangtze River, the Hanjiang River, a resource of drinking water, the protozoan diversity index indicated that water quality was in a critical status. In the unexploited Wuling Mountains Area in southwestern China, the protozoan diversity demonstrated that the aquatic ecosystem in this area was healthy and stable.

Interactions between earthworms and soil protozoa: A trophic component in the soil food web

Earthworms and protozoa are, in terms of biomass, the most important groups of soil fauna in beech forests on limestone in southern Lower Saxonia (Germany). To investigate the effect of high protozoan numbers on earthworm distribution, a multiple choice feeding experiment was set up in fumigated soil, reinoculated with different numbers of naked amoebae, protozoa commonly found in that soil. Distribution of Aporrectodea caliginosa (Savigny) after 1 wk was correlated with numbers of amoebae in soil. Other experiments confirmed digestion of protozoa by earthworms. The weight gain of young A. caliginosa in soil with amoebae was twice that in soil without protozoa. Direct observations of fresh cast material confirmed that active protozoa were digested by A. caliginosa. Lower protozoan numbers in faeces of Octolasion lacteum (Örley) than in the surrounding soil were found by dilution series, indicating grazing on the active part of soil protozoa by earthworms. The experiments provide evidence that A. caliginosa is actively searching for places with high protozoan densities and that protozoa may play a significant role in earthworm nutrition.

下水中のＧｉａｒｄｉａシストおよびＣｒｙｐｔｏｓｐｏｒｉｄｉｕｍオーシスト濃度と下水処理における除去性

In order to investigate the occurrence of Giardia cysts and Cryptosporidium oocysts in raw sewage and the removal in sewage treatment processes, we conducted a field survey at 9 sewage treatment plants. The results can be summarized as follows : 1) In all plants, Giardia cysts were detected in raw sewage and effluent of primary sedimentation. Cyst densities in raw sewage ranged from 130 to 5,500 cysts·l-1 (geometric mean 1,350 cysts·l-1). Cyst densities in effluent of primary sedimentation ranged from 150 to 5,200 cysts·l-1 (geometric mean 800cyst·l-1). 2) Cryptosporidium oocysts were detected from only one raw sewage sample with the density of 28 oocysts·l-1. 3) Indicator bacteria counts tested, C.perfringens spores, coliforms and E.coli, were statistically correlated with Giardia cyst densities and the most significant relationship was observed between C.perfringens spore counts and Giardia cyst densities. 4) No correlation was observed between Giardia cysts removal and indicator bacteria removal. However, significant relationship was observed between average removal of C.perfringens spores and Giardia cysts. These results indicated that C.perfringens spores can be useful indicator for the evaluation of protozoan densities and removal. 5) Turbidity appeared to be the most appropriate indicator for Giardia cysts removal in activated sludge treatment process.

Protozoan communities and contamination of several fluvial systems

Eleven stations in six rivers in the Comunidad Autonoma de Madrid (Spain) were studied during February 1993 to describe the protozoan communities and analyze the presence of lead and cadmium. The most polluted areas were Fuente del Fresno (Jarama River), where the levels of dissolved heavy metals were 10 μg/L of cadmium and 1 140 μg/L of lead acid, Torrej6n de Ardoz (Henares River) where there was 15 μg cadmium and 1 140 μg/L of lead. These two areas showed the greatest amount of industrial effluents, and the protozoan response expressed itself by the presence of resistant species such Euglena gracilis; density and biomass were not affected, although there were changes in the trophic structure, with a predominance of bacterivore and nonselective protozoans. The effects of the heavy metals were masked by the organic pollution. In the stations in well‐oxygenated waters, there was a predominance of photoautotrophs and diatoms. In all zones a significant correlation between the density of bacteria and protozoans was observed. The trophic structure of the protozoan communities in the different water courses was influenced by the amount of food available and by organic pollution.

Functional Effects of the Bacterial InsecticideBacillus thuringiensisvar.kurstakion Aquatic Microbial Communities

Epilithic microbial communities were colonized on leaf disks and exposed to commercial preparations ofBacillus thuringiensisvar.kurstaki(Btk) in aquatic microcosms. Responses in terms of microbial respiration, bacterial cell density, protozoan density, and microbial decomposition activity were measured. Test concentrations for treatments with Dipel 64AF and Dipel 8AF in microcosms were the expected environmental concentration (EEC) of 20 IU/ml, 100× the EEC, and 1000× the EEC. Bacterial cell density in the biofilm of leaf disks was significantly increased at concentrations as low as the EEC. There were no concomitant alterations in protozoan density. Microbial respiration was significantly increased, and decomposition activity was significantly decreased, but only at the artificially high concentration of 1000× the EEC. This effect was attributed to the spore–crystal component rather than formulation ingredients. Microbial decomposition of leaf material was also determined in outdoor stream channels treated at concentrations ranging from the EEC to 100× the EEC. Although there tended to be reduced decomposition activity in treated channels, there were no significant differences in mass loss of leaf material between treated and control channels. Various regression, classification, and ordination procedures were applied to the experimental data, and none indicated significant treatment effects. These results from laboratory and controlled field experiments indicate that contamination of watercourses with Btk is unlikely to result in significant adverse effects on microbial community function in terms of detrital decomposition.

Role of microplankton in the diet and daily ration of Antarctic zooplankton species during austral summer

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 143:15-23 (1996) - doi:10.3354/meps143015 Role of microplankton in the diet and daily ration of Antarctic zooplankton species during austral summer Froneman PW, Pakhomov EA, Perissinotto R, McQuaid CD Predation rates of the 9 most abundant Antarctic meso- (4 copepods) and macrozooplankton (3 euphausiids, 1 hyperiid and 1 salp) species on microplankton (20 to 200 µm) were estimated using in vitro incubations during the fourth cruise of the South African Antarctic Marine Ecosystem Study (SAAMES IV) to the ice-edge region of the Lazarev Sea during austral summer (Dec/Jan) 1994/1995. Chlorophyll a concentrations during the incubations ranged between 0.187 and 1.410 µg l-1 and were dominated by ice-associated chain-forming microphytoplankton (>20 µm) of the genera Nitzschia and Chaetoceros. The microplankton assemblages were entirely dominated by protozoans comprised of ciliates and dinoflagellates. Densities of protozoans ranged from 1375 to 2690 cells l-1. Based on previously published results, meso- and macrozooplankton species generally consumed >120% of their minimum daily ration, i.e. minimum carbon uptake (MCU), when offered microplankton. Exceptions were Euphausia crystallorophias and Vibilia antarctica for which microplankton carbon contributed 68 and 30% of MCU, respectively. Microplankton carbon contributed between 17 and 24% of the total carbon requirements for the 4 copepod species examined and between 21 and 73% for the macrozooplankton. The daily rations of juveniles were, however, twice those of the adults, suggesting that the relative importance of microzooplankton to the daily ration of macrozooplankton shifts with life stage. Carnivory by metazoan grazers may, therefore, potentially reduce the high grazing impact of microzooplankton on the local phytoplankton stock. Antarctica · Carnivory · Zooplankton · Microzooplankton Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 143. Publication date: November 14, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

A study of the natural antifouling mechanisms of the green musselPerna viridisL. (Mytilidae)

The green mussel Perna viridis L. (Mytilidae) is commonly found on hard substrata in the littoral zone of the upper Gulf of Thailand. Mussels appeared to be less densely colonized by epibionts than other artificial and natural hard substrata. The number of epibionts (bacteria, diatoms, protozoa, fungi, macroorganisms) on Perna viridis shells and their potential defence mechanisms were studied. The number of epibionts on isolated mussels and those in patches were compared. Densities of protozoa and macrofauna were much higher on isolated specimens than on aggregated (patch forming) mussels. Among possible antifouling mechanisms which were studied sloughing, shell surface tension and surface‐pH proved to be non effective in preventing fouling. Toxicity assays of shell extracts showed limited activity against bacteria and fungi. Grazing by two different gastropod species (Planaxis sulcatus, Thais sp.) reduced the number of protozoa and macroorganisms on isolated and aggregated mussels. Diatoms were restricte...

Bathymetric patterns of deep-sea benthic communities from bathyal to abyssal depths in the western South Pacific (Solomon and Coral Seas)

Ten stations were sampled from bathyal to abyssal depths (695–4350 m) in the Solomon and Coral Seas to determine variations in densities of Protozoa, meiofauna and macroinfauna in relation to environmental conditions and bacterial densities and productivity. Densities of large flagellates and amoebae did not change with water depth, whereas the abundance of other microbenthic groups either decreased (Foraminifera, ciliates) or increased (yeasts) significantly with increasing ocean depth. Numerically, the microbenthos was dominated by Foraminifera, followed in decreasing order of abundance by yeasts, large flagellates, amoebae and ciliates. Densities of total metazoan meiofauna and macroinfauna were low at most stations compared to communities of other regions at equivalent depths, and declined significantly with ocean depth, although many taxa and total macroinfaunal biomass did not. Differences in the rate of decline between total metazoan meiofaunal and macroinfaunal densities with depth were not significant. When the effect of water depth was held constant, only a few protozoan, meiofaunal and macroinfaunal taxa correlated with bacteria and sediment characteristics. Depth-related variables (e.g. low temperatures) appear to be the dominant factors regulating bathymetric patterns. However, there is some evidence that rapid transport of turbidites and other shallow-water materials (wood, vascular plant and fresh algal detritus) lead to episodes of erosion and deposition that may influence the distribution and standing crop of these deep-sea benthic communities. These events may be influential in other tectonically active basins within tropical oceans bordered by steep continental margins and dominated by extensive reefs and large rivers.

Regulation of Fusarium oxysporum populations introduced into soil: the amoebal predation hypothesis

Inoculation of fungi into soil has been suggested for biological control of plant diseases. The aim of our work was to test the ability of protozoa to reduce the density of introduced fungal populations. The survival of Fusarium oxysporum in non-sterile soil was studied after introduction at densities of: 1 × 104, 1 × 106 and 5 × 107 cfu/g soil. The dynamics of protozoa were also followed. The fungal populations remained close to the initial inoculation densities and did not induce the growth of indigenous protozoa. A bacterial population (Enterobacter aerogenes) was used to promote and stimulate the predatory activity of amoebae. Then, after simultaneous inoculation with bacteria and fungi, the density of protozoa increased but this had no effect on the fungal population, although some amoebae are able to feed on small fungal propagules such as conidia. The physiological state of Fusarium in soil and intraspecific competition seem to be more important in regulating introduced fungal populations than amoebal predation. We conclude that the regulation of bacterial and fungal populations in soil depend on different mechanisms.

Meiobenthic communities of the Santa Maria Basin on the California continental shelf

The Santa Maria Basin encompasses the bulk of the continental shelf off the central coast of California. Meiofauna communities on this shelf are very abundant. The average density of metazoa plus protozoans to a sediment depth of 10 cm was 4040 per 10 cm 2. Metazoan meiofauna were restricted to the surface sediments, where 84% were found in the top 4 cm. Over a 3-year period the average density within the top 4 cm of sediment was 1910 per 10 cm 2 in water depths of 90–410 m. At a depth of 565 m the density was much lower, 218 per 10 cm 2. The decrease in density correlated with a decrease in dissolved oxygen with depth. The percent of fine sediments and total organic carbon (TOC) content increased with water depth, therefore clay and carbon content were inversely correlated with density. There appears to be a seasonal cycle of increasing densities in the autumn and winter and decreasing densities in the summer. This cycle could be related to the seasonal cycle of storms and upwelling, which contribute energy to the benthos. The community structure of harpacticoid copepods was very complex. There were 115 species among 371 samples, and about 100 were undescribed species. Community structure was homogeneous between 90 and 410 m, but very different at 565 m. These changes correlated with changes in depth and sediment texture. Harpacticoid diversity also decreased with water depth. A suite of three factors; decreasing oxygen concentration and sediment grain size, and increasing TOC content; correlated with decreasing population density with water depth and with decreasing latitude across the basin.

Microbial and chemical responses to pulsed and gradual acid additions in dark- and clear-lake enclosures

Responses of lake bacteria, protozoans, and chlorophyll a, to two applications of sulfuric acid were observed in lake enclosure experiments. Acid was applied all at once (pulsed addition) or gradually over a 2 week period (gradual addition) to decrease pH to 3.5. These experiments were carried out simultaneously in a dark-dystrophic lake and a clear-oligotrophic lake on the Katherine Ordway Preserve, near Gainesville, Fla. Pulsed acid addition in the clear lake caused bacterial densities and biomass to increase, and bacterial growth to decrease. This indicated decreased grazing of bacteria by protozoans and/or zooplankton. Gradual addition caused some positive effects on bacterial biomass and metabolic processes indicating changes to more acid tolerant bacteria. Bacteria did not have time to adapt in the pulsed acid addition, while they did in the gradual acid addition. Acid additions had no significant effects on protozoan densities or chlorophyll a. Acid additions did not significantly affect bacterial densities or biomass in the dark lake. Glucose assimilation and glucose mineralization were significantly higher on day 6, while only glucose assimilation was higher on day 12 in the pulsed addition. Pulsed acid addition caused a decline in protozoans and chlorophyll a. Gradual acid addition caused increased protozoan densities and decreased chlorophyll a. Either the bacteria were better adapted to acid conditions or the dark lake chemistry buffered them against the effects of acidification.

Density‐dependent effects of protozoans on specific growth rates in pico‐ and nanoplanktonic assemblages

We experimentally assess nutrient feedback of oligotrichous ciliates and phagotrophic flagellates on growth in naturally occurring Mediterranean autotrophic microbial populations as well as on the microphytoplankton. Dialysis bags were used to separate cultured protozoa from the &lt;7‐µm plankton filtrates yet allow nutrient exchange. Growth rates in microbial autotrophic populations increased with protozoan densities added to bags. Microbial growth half‐saturation constants, expressed in terms of protozoan densities added, varied from 11 to 17 ciliates ml−1 and 2–5 × 103 flagellates ml−1. The “transdialysis contact” of protozoa with microbial planktonic populations led to growth rates 2 to &gt; 10 times higher than those observed without added protozoa. These findings suggest that in situ, autotrophic pico‐ and nanoplanktonic growth is limited by protozoan standing stocks. Lower generation times and half‐saturation constants were obtained for autotrophic nanoplankton (∼3 h, Kµ = 10 ciliates ml−1 and 1.7 × 103 phagotrophic flagellates ml−1, respectively). Microphytoplankton (e.g. diatoms and dinoflagellates) showed no significant functional responses to the addition of microprotozoa, suggesting a possible dependence of the latter on new rather than on recycled nutrients.

Microbiology and chemistry of acid lakes in Florida: II. Seasonal relationships

To determine relationships of chemistry and microbiology in lakes exposed to acid precipitation, three clear and two dark acid lakes on the Katharine Ordway Preserve near Gainesville, Florida were monitored from February 1986 to July 1987. Chemical measurements included Dissolved Organic Carbon (DOC), pH, acidity, temperature, dissolved oxygen, and nutrients. Bacterial densities, bacterial biomass, bacterial growth, bacterial assimilation of glucose, protozoan densities, and chlorophyll a were also measured. Rainfall and rainfall chemistry data were obtained from the Bradford Forest Acid Deposition station approximately 34 kilometers NNW of the preserve.

Populational Changes of the Enteric Protozoans Opalina spp. and Nyctotherus cordiformis During the Ontogeny of Anuran Tadpoles

ABSTRACT. We studied ontogenetic population changes of Opalina and Nyctotherus cordiformis in eight species of tadpoles from 10 sites in east‐central Mississippi. Most tadpoles acquired Opalina early in development, while the acquisition of N. cordiformis was variable. Developmental stage, species and collection site explained significant amounts of the variation in Opalina density of tadpoles (F= 11.6; df = 27, 235; P &lt; 0.0001) and metamorphs (F= 7.31; df = 24, 84; P &lt; 0.0001). Relationships between Opalina density and host stage showed either (1) a gradual decrease or (2) a gradual increase throughout host ontogeny. Opalina densities declined during metamorphosis. Density variations of N. cordiformis were explained by host species of tadpoles (F= 9.30; df = 7, 142; P &lt; 0.0001) and by host species and stage of metamorphs (F= 5.85; df = 8, 62; P &lt; 0.0001).The length of larval period, habitat duration and generation time of the protozoans are suggested as major modifiers of the protozoan densities. Hosts with long larval periods show a decreasing population density and hosts with short developmental periods show a pattern of increasing density. Neither pattern was detected in tadpoles from temporary sites. Metamorphic declines in protozoan density, but not necessarily the loss of protozoans, reflect metamorphic alterations of the gut common to all hosts.

Rates of Protozoan Bacterivory in Three Habitats of a Southeastern Blackwater River

Although protozoa have been largely disregarded in the trophic structure of lotic systems, they have been shown to be important in lentic and marine environments. As part of a larger study concerning the basis of secondary production in the Ogeechee River, GA, preliminary experiments were done using fluorescently-labelled bacteria to directly measure bacterial grazing by protozoa. Protozoan grazing rates can be as high in moving lotic waters as in still waters as demonstrated by comparing a main channel site, a backwater, and a floodplain pond. In the main channel site during April and May 1988, flagellates and ciliates ingested an average of 17 and 320 bacteria/individual/hr, respectively. When this is multiplied by the high protozoan densities present, an average of 47% of the water-column in the main channel is estimated to be cleared of bacteria by protists each day. Protozoan bacterivory could facilitate carbon flow to higher trophic levels by turning bacteria into larger parcels of carbon and nutrients which are available to a greater portion of the filter-feeding members of communities.

Population dynamics and activity of bacteria and protozoa in relation to their spatial distribution in soil

The effects of protozoan inoculum density and spatial separation of (prey) organisms on the turnover and transport of specific microbial populations in sterilized soil were studied in soil microcosms, applying a combination of techniques. The fate of introduced microbial biomass was followed by monitoring 14C-CO 2 evolution. Dynamics of and genetic transfer between genetically marked bacteria were followed by selective plating using appropriate antibiotics. Three levels of protozoan densities, i.e. no protozoa, protozoa and a 1: 10 diluted protozoan inoculum were established. Two methods of soil inoculation, i.e. joint introduction and separate introduction of protozoa with a donor population and of a 14C-labelled recipient population, respectively, were applied. The activity of protozoa, as judged from increased CO 2 evolution compared to soils not inoculated with protozoa, was larger when 100% of the soil was inoculated with protozoa (joint introduction) compared to inoculation of protozoa into only 33% of the soil which was mixed with 66% of a soil portion not inoculated with protozoa (separate introduction). The activity of protozoa accelerated the turnover of 14C compared to soils without protozoa. The more protozoa added, the faster 14C was respired both in soils with joint, and in soils with separate, introduction. The transfer of genetic material between introduced donor and recipient cells was not influenced by the presence of protozoa but was reduced when separate introduction was applied compared to joint introduction. Transfer of genetic material was only found during the first 2 days of the incubation. Substantial loss of genetic material (plasmid RP4) in the donor population was detected; the presence of protozoa enhanced both donor survival and plasmid maintenance. A stimulating effect of protozoa on cellular metabolism of substrate used by the donor population is hypothesized. These results picture soil as a system in which the distribution of microorganisms in the absence of fluctuations in climatic conditions is not changing in time: protozoa hardly moved through the soil and minimal translocation of bacteria was found.

Fluctuations in the community composition of water-column protozoa in two southeastern blackwater rivers (Georgia, USA)

This study addresses protozoan population dynamics of two southeastern blackwater rivers in Georgia: the sixth order Ogeechee River and fourth order Black Creek. The density and composition of the protozoan community was assessed by counting the protozoans into size classes. Particularly abundant flagellate types (bloom forms) and ciliates were enumerated separately. Protozoan density in these blackwater rivers is high. Observations during a two week and a ten month census showed that the rate of community change is rapid and that the range in diversity is great. A backwater site showed the highest percentage of bloom forms, while the main channel sites of Black Creek and the Ogeechee River had fewer bloom forms. Rapid increases in density during a two week microcosm study were attributed to isolation of the water-column from filter-feeders, the benthos, and different source areas. An analogous situation may exist in the low order swamp streams and backwater habitats where many dense blooms occur. The high protozoan population densities observed were partially due to rapid changes in the physical characteristics of the environment, reactions of the protozoa to such changes, growth in the swamp tributaries and backwater areas, subsequent washing into the river, and further growth as the water moves toward the sea.

Densities of Benthic Protozoa and Nematodes in a Piedmont Stream

Densities of protozoa in sediments and leaf accumulations in a first-order spring seep, and in sediments and on stones in a third-order stream reach were determined over a 17-mo period. Higher densities were obtained from microscopic counts than from determinations of most probable number (a statistical estimate of number derived from growth responses when serial dilutions of sample are inoculated into replicate cultures of bacterized Cerophyl). Protozoa densities were higher per unit area of sediment than per unit area of leaves or rock surfaces. Microflagellate densities in sediments ranged from 9.00 × 10⁵ to 2.29 × 10⁷/cm² (x̄ ± 1 SD = 5.32 ± 7.36 × 10⁶, n = 15) in the seep and from 6.00 × 10⁵ to 1.04 × 10⁷/cm² (2.06 ± 2.32 × 10⁶, n = 18) in the stream. Ciliate densities ranged from 5.00 × 10³ to 3.32 × 10⁴/cm² (1.54 ± 1.09 × 10⁴, n = 5) in the seep and from 5.00 × 10³ to 3.65 × 10⁴/cm² (1.09 ± 0.88 × 10⁴, n = 12) in the stream. Nematodes were separated from sediments by a combination of sieving, flotation in sucrose, and centrifugation, and were counted microscopically. Nematode densities in sediments in the stream ranged from 0.90 to 8.85/cm² in fine sediments (x̄ ± 1 SD = 4.2 ± 1.9, n = 15) and from 0.20 to 1.80/cm² (1.1 ± 0.2, n = 7) in coarse sediments.