2nd Order Streams Research Articles

Response of Periphytic Algae to Gradients in Nitrogen and Phosphorus in Streamside Mesocosms

In this study we manipulated both nitrogen and phosphorus concentrations in stream mesocosms to develop quantitative relationships between periphytic algal growth rates and peak biomass with inorganic N and P concentrations. Stream water from Harts Run, a 2nd order stream in a pristine catchment, was constantly added to 36 stream-side stream mesocosms in low volumes and then recirculated to reduce nutrient concentrations. Clay tiles were colonized with periphyton in the mesocosms. Nutrients were added to create P and N concentrations ranging from less than Harts Run concentrations to 128 μg SRP l−1 and 1024 μg NO3-N l−1. Algae and water were sampled every 3 days during colonization until periphyton communities reached peak biomass and then sloughed. Nutrient depletion was substantial in the mesocosms. Algae accumulated in all streams, even streams in which no nutrients were added. Nutrient limitation of algal growth and peak biomass accrual was observed in both low P and low N conditions. The Monod model best explained relationships between P and N concentrations and algal growth and peak biomass. Algal growth was 90% of maximum rates or higher in nutrient concentrations 16 μg SRP l−1 and 86 μg DIN l−1. These saturating concentrations for growth rates were 3–5 times lower than concentrations needed to produce maximum biomass. Modified Monod models using both DIN and SRP were developed to explain algal growth rates and peak biomass, which respectively explained 44 and 70% of the variance in algal response.

Coarse Particulate Organic Matter Distribution in the Pools and Riffles of a Second-order Stream

Coarse particulate organic matter distribution was investigated in a 270-m interval of a 2nd-order forest stream, the Yanase River. The dominant tree type was Keyaki (Zelkova serrata). CPOM sampling was conducted, and the sampled CPOM was sorted into leaves and branches, and water depth and current velocity were measured along with stone width, stone height and distance between the stones in the riffles. The collected CPOM was categorized by their accumulation type: LSS, SLP, SLPi, SLPo and DD. LSS was leaf packs at the leading edge of the stones, SLP was the sinking leaf packs in the pools, SLPi was the sinking leaf packs at the inner side of the stream bend in the pools, while SLPo was the sinking leaf packs at the outer side of the stream bend, and finally, DD was the leaf packs in the debris dams. The accumulated CPOM amounts at each leaf pack type were correlated with the measured physical stream variables. From the results, CPOM accumulation in riffles is controlled by stones projecting above the water surface and by their arrangements. In pools, CPOM accumulation occurs at high stream flow where the pools provide low velocities and a thick boundary layer of relatively quiescent flow. At stream meandering points, CPOM accumulation occurs by production of a secondary flow. Finally, CPOM accumulation in debris dams is important where they occur frequently. LSS was the largest in CPOM amount, and the stones in the riffles were the most retentive structures. On the other hand, SLP and SLPo were the least CPOM amounts, and the pools in the mainstream and at the outer side of the stream bend were the least retentive stream morphologies.

Food quality and feeding preferences ofPhylloicussp. (Trichoptera:Calamoceratidae)

AbstractThe aim of our study was to determine experimentally the influence of the chemical composition of native leaf species on feeding preferences and growth of the tropical shredder Phylloicus sp. We tested whether Phylloicus was able to discriminate among leaf species, and whether leaf species affected its growth rate. The native leaf species selected for the study were: Anacardiumexcelsum (Anacardiaceae), Ficus sp. (Moraceae), Huracrepitans (Euphorbiaceae), and Tabebuiarosea (Bignoniaceae). Phylloicus larvae and leaves of native tree species were collected from Cano Carichuano, a 2nd-order intermittent stream located in northwestern Venezuela. Larvae were acclimated to laboratory conditions, and leaves were air dried and stored before beginning the experiments. Additional leaves were used to determine initial chemical composition (P, lignin, N, and polyphenols). Feeding experiments were conducted in which larvae were given a choice of different leaf species. Phylloicus preferred to feed on leaf speci...

Effects of patchy shade on stream water temperature: how quickly do small streams heat and cool?

Summer field observations in five 2nd order streams (width 1–2 m, depth 5–15 cm, velocity 5–10 cm s–1) in Western Australia and south-east Queensland showed that daily maximum temperatures changed by ±4°C over distances of 600–960 m (travel time 2–3 h) immediately downstream from 40–70% step changes in riparian shade. There was a strong linear relationship between the rate of change of daily maximum temperature and the change of shade such that downstream from a 100% change of shade the heating/cooling rates are ±4°C h–1 and ±10°C km–1 (upper bound ±6°C h–1 and ±15°C km–1) respectively. These high rates only apply over short distances and travel times because downstream water temperatures adjust to the new level of shade and reach a dynamic equilibrium. Shade was too patchy in the study streams to measure how long water takes to reach equilibrium, however, using an existing computer model, we estimate that this occurs after ~1200 m (travel time 4 h). Further modelling work is desirable to predict equilibrium temperatures under given meteorological, flow and shade conditions. Nevertheless, landowners and regulators can use this information to determine whether the presence/absence of certain lengths of bankside shade are likely to cause desirable/undesirable temperature decreases/increases.

Hydromorphological and biological factors influencing sediment and phosphorus loss via bank erosion in small lowland rural streams in Denmark

AbstractBank erosion was measured at 91 stream banks located in 15 Danish rural 1st and 2nd order streams over a 2‐year period. Our aims were firstly to examine factors controlling spatial variation in bank erosion, secondly to estimate sediment and phosphorus (P) loss via bank erosion. The overall mean bank erosion rate was 11 mm year−1. Bank erosion rate over the 2‐year period was significantly related to a number of site‐specific characteristics, including bank angle, bank vegetation cover, overhanging bank and estimated stream power. An empirical model for bank erosion based on these descriptive variables yielded a 55% explanation of the observed spatial variation in bank erosion rate. Bank erosion was higher at the lower 50‐cm bank section (20 mm year−1) than at the upper bank (6 mm year−1). Cattle fencing in grazed areas and buffer zones with riparian woodland lowered bank erosion rates. We found that total P content of bank material was high (0·64 g P kg−1) and at the same level as found in agricultural topsoil along the streams. The overall annual catchment loss of bank‐derived clay–silt sediment and total P to streams amounted to 58–72 kg sediment ha−1 and 0·23–0·28 kg P ha−1, respectively. In comparison, the mean annual suspended sediment (SS) and total P losses from 14 similar sized Danish agricultural catchments were 122 kg SS ha−1 and 0·58 kg P ha−1 over the 2‐year study period. Thus, bank erosion seems to be a major contributor of suspended sediment and P in this type of small channelized lowland stream. Copyright © 2003 John Wiley & Sons, Ltd.

Mapping the spatial and temporal distributions of woody debris in streams of the Greater Yellowstone Ecosystem, USA

The objectives of this study were: (1) to document spatial and temporal distributions of large woody debris (LWD) at watershed scales and investigate some of the controlling processes; and (2) to judge the potential for mapping LWD accumulations with airborne multispectral imagery. Field surveys were conducted on the Snake River, Soda Butte Creek, and Cache Creek in the Greater Yellowstone Ecosystem, USA. The amount of woody debris per kilometer is highest in 2nd order streams, widely variable in 3rd and 4th order streams, and relatively low in the 6th order system. Floods led to increases in woody debris in 2nd order streams. Floods redistributed the wood in 3rd and 4th order streams, removing it from the channel and stranding it on bars, but appeared to generate little change in the total amount of wood throughout the channel system. The movement of woody debris suggests a system that is the reverse of most sediment transport systems in mountains. In 1st and 2nd order tributaries, the wood is too large to be moved and the system is transport-limited, with floods introducing new material through undercutting, but not removing wood through downstream transport. In the intermediate 3rd and 4th order channels, the system displays characteristics of dynamic equilibrium, where the channel is able remove the debris at approximately the same rate that it is introduced. The spatial distribution and quantity of wood in 3rd and 4th order reaches varies widely, however, as wood is alternatively stranded on gravel bars or moved downstream during periods of bar mobilization. In the 6th order and larger channels, the system becomes supply-limited, where almost all material in the main stream can be transported out of the central channel by normal stream flows and deposition occurs primarily on banks or in eddy pool environments. Attempts to map woody debris with 1-m resolution digital four-band imagery were generally unsuccessful, primarily because the imagery could not distinguish the narrow logs within a pixel from the surrounding sand and gravel background and due to problems in precisely coregistering imagery and field maps.

Diversity and habitat preference of aquatic insects along the longitudinal gradient of the Macaé River basin, Rio de Janeiro, Brazil.

Diversity and habitat preference of macroinvertebrates were studied in Macaé River basin, Rio de Janeiro State, Brazil, along its longitudinal gradient. We selected stream reaches corresponding to 1st, 2nd, 4th, 5th and 6th orders. A Surber sampler was used to collect four macroinvertebrates samples of each substrate (sand, litter in pool areas, stones, and litter in riffle areas) during the three sampling periods, defined based on the rain regime: April (end of the rainy season), July (dry season), and October (beginning of the rainy season). We identified 46,431 specimens corresponding to 117 taxa. Analysis of diversity numbers (both for family or genus level) indicated that all insect taxonomic orders had higher numbers on 2nd order stream reach, except for Ephemeroptera, on 4th order. However when considering morph-species taxonomic level, the higher diversity number occurred on 4th order stream. The highest richness and diversity numbers were found at the dry season. Considering habitat preference, both litter in pool areas and litter in riffle areas had the highest faunal richness.

Relationship of soil properties to parent material and landscape position in eastern Madre de Dios, Peru

Properties of soils in the eastern part of Madre de Dios, Peru, were characterized and related to landscape position and parent material texture. Level uplands, dissected side slopes and recent flood plains dominate the topography in this region. Soil textures vary from clayey to sandy, depending on the texture of sedimentary materials from which each pedon formed. Parent material textural variation is a result of differences in the energy of the meandering rivers that deposited the ancient alluvium. Fourteen soil profiles were described and sampled in the field and analyzed in the laboratory. Data for eight soil profiles representative of the region are presented here. The profiles include soils formed in both sandy and fine-textured parent materials and soils with moisture status ranging from well drained to poorly drained. Soil moisture conditions vary with position on the landscape, such that as distance from streams increases, average depth to the fluctuating water table decreases. Redoximorphic features are present in all mineral soils. The average depth to redoximorphic features is least in locations furthest from streams. Soils in landscape positions that are poorly or somewhat poorly drained contain significant amounts of plinthite. In all soils, kaolinite is the dominant mineral in the <0.2 μm fraction, while quartz is the dominant mineral in very fine and fine sand fractions. All soils have low cation exchange capacity (CEC), low base saturation, and acid pH. Coarse-textured spodic soils with well developed zones of iron and organic matter translocation are formed in recent sand deposits of flood plains of 2nd-order streams. Organic soils are found in the wetlands associated with flood plains of some 3rd-order streams. Most properties of these soils appear to be controlled by the textures of their sedimentary parent materials and by their position on the landscape. The soils classify as Paleustults, Plinthaquults, Kandiustults, Placaquods and Troposaprists according to Soil Taxonomy. New subgroups of Paleustult are proposed.

Hydrologic Context and Macroinvertebrate Community Response to Floods in an Appalachian Headwater Stream

-The response of aquatic macroinvertebrates to two floods was examined in a 2nd-order stream draining a 132-ha watershed on the Fernow Experimental Forest in West Virginia. Floods with recurrence intervals of 18 and 12 yr occurred in February and May 1994. Benthic organic matter and macroinvertebrate abundance and community structure were affected by the floods. Most of the common macroinvertebrate taxa decreased in abundance 70-95% immediately following the February flood. For most physical and biotic variables, recovery to preflood levels was complete before the May flood (42 days) based on preflood levels. Shifts in community structure following floods were small compared to seasonal variation. By August following the May flood, few differences could be detected from August of the previous year. Taxa associated with organic matter accumulations such as leaf packs and organic debris dams were affected less by the February flood than were most riffle taxa; one common leaf pack taxa, Pteronarcys, increased in abundance in riffles following the flood. I attribute the rapid recovery of the benthic community to abundant refugia, including organic debris dams, deep interstitial habitat, and 1st-order tributaries. Analysis of the long-term flow record for the Fernow Experimental Forest suggests that a probabilitybased hydrologic criterion for a flow disturbance is inadequate for Appalachian headwater streams.

A Tailed Frog (Ascaphus truei) Nest Site in Northwestern California

The tailed frog (Ascaphus truei) inhabits streams in the Pacific Northwest, Idaho, and Montana (Nussbaum and others 1983). Few nests of A. truei have been reported and nest sites and time of oviposition are not well known. Daugherty and Sheldon (1982) determined oviposition occurred in June in Montana populations. Brown (1989) collected females with mature eggs in early July in NW Washington. Adams (1993) discovered a nest with 27 eggs in the Oregon Coast Range in August 1991 that may have consisted of 3 different clutches, based on varying developmental stages. Nest sites of A. truei have not been documented previously in California. On 16 August 1994, we discovered an A. truei nest site approximately 15 km N of Trinidad, Humboldt County, California in the McDonald Creek drainage. Twenty-eight eggs were attached to the underside of a boulder (44x28 cm) in a pool of a 2nd-order stream (4.3-m wide), 8 km inland from the Pacific Ocean. The pool (40x20x10 cm) received continuous water flow. The nest site occurred on private forest land in a SW-facing stream with 18% gradient. Water temperature was 15.9°C at 1700 hr. Overstory vegetation was primarily 45 yr-old coast redwood (Sequoia sempervirens) and red alder (Alnus rubra), with 90% canopy closure (measured with a densiometer). The nest site was 23.5 m below a road culvert and 0.7 m above the stream's confluence with a 3rd-order fishbearing stream. We observed the nest from 16 August through 20 September 1994. Three eggs were destroyed when the boulder was turned over, but 25 eggs remained intact in a loose string beneath the boulder. The eggs were cream-colored, each approximately 5 mm in diameter. No potential predators were seen in the pool during the observation period, but 5 larval Pacific giant salamanders (Dicamptodon tenebrosus) and 1 adult A. truei were found within the 24.2 m stream reach surveyed on 16 August 1994. The tailed frog nest site was located 0.7 m above the downstream end of the surveyed reach. On 26 August, 8 tadpoles were observed in the pool, and 8 eggs remained attached to the boulder. On 2 September, 23 tadpoles were observed in the pool, and no unhatched eggs remained. Tadpoles were easily counted due to the depth of the pool (10 cm), substrate size (sand <2 mm in diameter), and the clarity of the water. During the observation period varying numbers (8 to 23) of tadpoles were observed in the pool, indicating movement of tadpoles between the natal pool and other regions of the stream. No attempts were made to locate tadpoles outside of the pool. On 20 September, 5 tadpoles were measured and averaged 20 mm. The tadpoles were dark gray in color, and each had developed the characteristic white tail spot. Three tadpoles were attached to a boulder, indicating functioning oral discs. We filled a plastic container with decaying leaf litter and gravel, punched numerous holes in all sides, and anchored it in the stream with boulders. Two tadpoles were placed in the container for future measurements. On 20 October, no tadpoles were observed around the nest site. The 2 tadpoles in the plastic container were measured (22 mm and 23 mm, respectively) and released. Oviposition by A. truei apparently occurs between late June and early August (Adams 1983, Daugherty and Sheldon 1982). The clutch found in California probably was deposited in late July and consisted of only 1 clutch because of the uniform developmental stage of the eggs upon discovery, the brief period over which hatching occurred, and their attachment to the boulder in 1 continuous string. Mean clutch sizes reported for inland areas range from 63 eggs in Washington (Brown 1975) to 75 eggs in Montana (Franz 1970). Although we do not know if any predation of eggs occurred before their discovery, the clutch size (N = 28) of the California nest is consistent with others reported for coastal A. truei (Adams 1993, Noble and Putnam 1931). This supports the hypothesis (Adams 1993) that coastal populations may have smaller clutch sizes than inland populations.

Aggregations of Sharptail Snakes (Contia tenuis) on the East Slope of the Cascade Range in Washington State

formed in some boxes over pools (30% of boxes in December, 30% in January, 0 in February) and riffles (50% of boxes in December, 20% in January, 20% in February). In all cases, water was flowing under the surface ice, and no anchor ice had formed on the bottom of the streams. No A. truei were found in the boxes. However, using a dip net we found A. truei in 4 of 4 streams searched: in 1 stream in November, 2 streams in December, 1 stream in January, and 4 streams in February. We found 9 adults and 12 larvae under rocks (< 35-cm diameter) in riffles. These had not burrowed into the stream bed. There may be geographic variation in overwintering locations, as A. truei in western Washington appear to burrow into the stream substrate (H. A. Brown, pers. comm.). The presence of anchor ice in some streams may preclude their use by this species. In the 10 streams observed, the water flowed all winter under deep layers of snow, and we suspect that the snow protected the streams from freezing and allowed the frogs to overwinter in the water. If anchor ice had formed in the study streams, the frogs probably would have been frozen. Because A. truei remain in the streams in winter, it is imperative that management activities near these 1Stand 2nd-order streams preserve the integrity of the stream structure and adjacent habitat. In particular, management activities that affect winter stream flow and icing conditions may adversely affect A. truei. Additional research is warranted on distribution of A. truei relative to winter stream conditions, winter survivorship, and to determine if A. truei also are buried in the substrate

Microhabitat use by two small benthic stream fish in a 2nd order stream

Microhabitat use by two small benthic stream fish in a 2nd order stream

A track count for estimating mountain lion Felis concolor californica population trend

Reliable estimates of status and population trend are critical for conservation of large terrestrial carnivores, but are usually lacking due to the high costs of sampling across large geographic areas. For detecting population trends of mountain lion Felis concolor californica, we evaluated counts of track sets on 48 randomly chosen quadrats in California. Each quadrat contained 33.8 km of transect on dusty, dirt roads, which were chosen by local wildlife biologists. A count of track sets by one person on all quadrats was more efficient than recording presence/absence by local survey teams. We estimated an efficient sample size of 44 quadrats in California after applying our data to a general formula for contagious distributions. This sample size can be reduced substantially by choosing new transect locations based on associations of tracks with topography and habitat. Tracks were most likely found on roads along 1st- and 2nd-order streams, on mountain slopes and knolls/peaks and in oak woodland and montane hardwood conifer forest. A changing mountain lion population can be detected with an inexpensive, periodic track survey and self-stratifying, non-parametric tests. Each track survey across California can be finished in 30 days. The many mountain lions and the variety of environmental conditions included at this extraordinarily large spatial scale permit estimates of: (1) trends among population strata in quadrats that are clustered according to typical number and age/sex class of track sets; (2) population size and demography after individuals are identified by their tracks, and after linear density on roads is calibrated from spatial density at intensive study, sites: and (3) spatio-temporal associations with bobcat Felis rufus, black bear Ursus americanus, coyote Canis latrans, and fox Vulpes vulpes and Urocyon cinereoargenteus.

Habitat Selection by the Stream Mayfly Paraleptophlebia guttata

The causes and consequences of habitat distribution of larvae of the mayfly Paraleptophlebia guttata were analyzed in a 2nd-order stream in west-central Kentucky. Among macrohabitats, larvae were typically significantly more dense in runs and riffles than in pools. Densities were positively related to the percentage of coarse substrata in macrohabitats, but were not correlated with current velocity, predatory fish densities, or the quantity of fine particulate organic matter (food) in macrohabitats. This relationship between density and substratum coarseness was further evidenced in an in-situ colonization experiment in which larvae selected gravel and pebble substrata over sand. Among microhabitats, larvae were more abundant in leaf litter and in gravel/pebble than in silt/sand. Laboratory manipulations showed that predation rates by fish were significantly lower on mayflies in leaf litter and gravel than in fine substrata. The combined effects of substratum particle size and fish predation determine hab...

Short-Term Colonization of Rough and Smooth Tiles by Benthic Macroinvertebrates and Algae (Chlorophyll a) in Two Streams

We examined the importance of substratum texture and the colonization dynamics of stream macroinvertebrates and algae (measured as chlorophyll a) using artificial substrata and two sampling designs in two ecologically different streams. Rough and smooth clay tiles were used in two short-term colonization studies, which were conducted in a 2nd-order Rocky Mountain foothill stream and a 2nd-order stream in the boreal mixed woodland of Alberta, Canada. At both streams, two sampling designs were used concurrently: (1) simultaneous placement and sequential removal of substrata, and (2) sequential placement and simultaneous removal of substrata. Three hypotheses were tested: there was no difference in the density of macroinvertebrates or quantity of chlorophyll a (1) on rough and smooth tiles, (2) for different colonization periods (1-14 d), and (3) for both sampling designs. Density of most macroinvertebrates and the quantity of chlorophyll a was greater on the rough tiles in both sampling designs and in both streams. Both sampling designs gave consistent results for the effect of texture for most taxa over eight colonization periods. Similar results for the sampling designs and in both streams provide strong evidence for the importance of substratum texture in streams. Some macroinvertebrate colonization patterns indicated early and late colonizers, while other patterns indicated no colonization trend. Several taxa showed similar trends in colonization to the quantity of chlorophyll a on the tiles. But after 1-4 d, when there was little chlorophyll a on the tiles (mean chlorophyll a < 0.1 μg/cm²), density of total number of organisms and most taxa was greater on rough tiles than on smooth tiles in both sampling designs. In contrast to most macroinvertebrates, Epeorus (Ephemeroptera: Heptageniidae) nymphs were more abundant on smooth tiles than on rough tiles.

Estimation of Fine Particulate Transport in Streams Using Pollen as a Seston Analog

We describe a new method for estimating the distance that fine particulate organic matter (FPOM) is transported in streams. Corn pollen (diameter = 87 μm, ρ = 1092 kg/m³) was injected into Dry Brook, a 2nd-order stream in Allegany State Park, New York. Loss of pollen from the water column was measured by filtering pollen from ∼250-mL grab samples, staining with basic fuschin, and counting. Loss rates were fit to an exponential decay function; mean travel distances on three release dates ranged from 122 to 190 m, consistent with predictions of a model that assumes particle loss is proportional to the settling velocity of a particle in still water and the depth of the water column. Pollen, as a seston analog, would provide a comparative tool to measure transport in streams that differ in critical geomorphic and hydraulic characteristics. This technique can be applied to questions on how bed structure and near-bed flow affect retention and transport of seston, and on the importance of still water settling velocities, stream temperature, and biological uptake in determining FPOM travel distances.

Changes in biologically controlled carbon fluxes in a small stream following continuous supply of excess organic load

The consequences of a constant supply of organic load from a pigsty to a small 2nd order stream are analysed through simultaneous consideration of amount of carbon stored in benthic biomass and of main biologically controlled carbon fluxes. The results show that the allochthonous load induced a general increase in all fluxes and therefore stimulated processes of carbon elimination from the receiving system. The increase of biologically controlled fluxes was due to qualitative changes of populations toward specialization for an optimal use of the newly supplied organic substrates. This was especially evident in this stream for macro-invertebrate biomass production and for insect emergence. Effects of trophic pollution ranged from drastic modifications near the input of the pig waste to a place where the additional supply of organic substrate increased the numbers of individuals of macroinvertebrate populations without any change in their specific diversity. Variations of CO2 production appeared to be more related to biomass of microbial populations in the downstream station and to macroinvertebrates in the upstream station. Although the allochthonous load caused significant increases in several processes involved in its own elimination, the magnitude of these increases was small compared to the influx of organic carbon from upstream and from the pigsty.

An assessment of short-term depletion of stream macroinvertebrate benthos by drift

A study was conducted to determine if emigration of drifting macroinvertebrates from a stream riffle which was blocked for one week from immigration by upstream colonists significantly reduced the abundance of drift collected from the tail of the riffle. The head of a 9 m long riffle of a 2nd order stream in Maryland (USA) was blocked from incoming drift by a 250 μm mesh weir. Upstream immigration of invertebrates into the riffle was largely prevented by a partition placed at the tail of the riffle which held the drift nets. Benthos and drift samples were collected from the riffle prior to weir placement and following its removal, and drift was collected at dusk on each day. No difference in drift or in benthic abundance between the beginning and end of the study was observed. This is largely attributed to recruitment of immature insects (primarily hatching of eggs present at the outset), particularly of Dolophilodes distinctus and species of Tanytarsini, from within the riffle. Results suggest that recruitment of riffle species is of sufficient magnitude to more than compensate for short-term riffle depletion due to drift. Samples of drifting and non-drifting (benthic) animals were held without food for 12 h after collection and mortality within each group was determined. The mortality of drifting animals was three-fold that of benthic animals.

Tungsten exploration in the Valnesfjord region, Nordland, Northern Norway

A tungsten exploration programme in the Valnesfjord region was carried out during two short summers by drainage and follow-up investigations. At each sampling site a heavy-mineral concentrate and a stream sediment sample were collected in either 1st or 2nd order streams. Soil samples were collected from the C horizon at a depth of 30–120 cm, in most cases at the top of the bedrock. Five litres of soil were sampled, 200 g for chemical analysis and the rest was preconcentrated by panning and the scheelite grains counted. The raw data from the stream sediments were all normalized to one litre of the −1-mm fraction of the panned sediment. The threshold value is 30 grains of scheelite in the normalized samples and the peak value from the regional survey was 131 grains of scheelite. The majority of the anomalous samples (8) were related to a “shear zone”. A detailed follow-up survey revealed that the scheelite mineralization is associated with a zone in the lowermost part of the shear zone in a dolomite-limestone sequence and/or a calcareous biotite schist. The peak anomaly in the stream sediments was 1000 grains of scheelite, while the soil samples gave a peak value of 2500 grains of scheelite. Three types of mineralization were found by UV investigations in the field: (a) tourmalinites with large scheelite crystals in vugs; (b) small crystals of scheelite in quartz pegmatites; and (c) disseminated scheelite in calcareous biotite schists. The latter is the most interesting from an economical point of view.

Characteristics of Sediment and Organic Carbon Export from Pristine Boreal Forest Watersheds

Estimates of the amount of material moving annually from terrestrial ecosystems to the ocean are largely based on an incomplete understanding of events occurring throughout the hydrologic year, and only a vague comprehension of in-stream processes controlling that export. Discharge, suspended sediment, particulate organic matter (POM; &gt; 0.5 μm), dissolved organic carbon (DOC; &lt;0.5 μm diameter), and the percentage of organic matter were measured from 1979 to 1981 in five pristine Quebec streams: First Choice Creek (1st order; watershed area: 0.25 km2), Beaver Creek (2nd order; 1.83 km2), Muskrat River (5th order; 204 km2), Matamek River (6th order; 673 km2), and the Moisie River (9th order; 19 871 km2). All streams, with the exception of First Choice Creek, have a strong spring freshet when 43–55% of the annual discharge occurs. By describing sediment and organic carbon export throughout the annual hydrologic cycle, 1 showed that during the 2-mo spring freshet 71–92% of the annual sediment load is exported but only 59–65% of the annual POM load, and only 47–51% of the annual DOC load. Sediment yield is relatively constant between watersheds (1.5–7.6 g∙m−2∙yr−1), as is POM export (1.0–6.7 g ash-free dry-weight [AFDW]∙m−2∙yr−1); however, export DOC varies from 3.1 g C∙m−2∙yr−1 in First Choice Creek to 48.4 g C∙m−2∙yr−1 in Beaver Creek. There appears to be rapid loading of carbon between 1st- and 2nd-order streams in boreal forests, followed by biological and physical processing as watershed area increases. Thus, for the Moisie River watershed, export of total organic carbon (TOC) is reduced to only 4.7 g C∙m−2∙yr−1. Export of coarse particulate organic matter (&gt; 1 mm) is negligible (normally &lt; 0.1 mg∙L−1), as is oxidation of the suspended load (&lt; 0.5%∙d−1). Effects of summer storms, natural diel variations, and depth of sample from the water column are shown to have a minimal influence on concentrations. Rating curves (kg∙d−1 vs. discharge) are developed to estimate the annual yield of sediment, POM, and DOC, and to evaluate long-term variations. From the results I suggest that in-stream processing and retention devices exert considerable control over the quantity and nature of suspended organic material. Physical processes such as the discharge regime and stream power are relatively less important in determining organic concentrations, but more important in determining sediment concentrations.Key words: seston, carbon, sediment, boreal forest, watershed, river, stream, export