Tributary Sites Research Articles

Longitudinal changes in microbial assemblages of the Ogeechee River

Summary 1 Bacteria are common and important constituents of aquatic ecosystems but little is known about their populations; most measurements commonly employed are at a grosser, assemblage-level. The purpose of this study was to compare longitudinal patterns in microbial assemblages and populations along a river ecosystem. 2 Water samples were collected under base flow conditions from 13 main stem and four tributary sites along the Ogeechee River spanning the piedmont and coastal plain of Georgia, USA. Based on the detection of active cells with abundant ribosomes, two species of bacteria, Acinetobacter calcoaceticus and Pseudomonas putida, represented 0.4–4.9% of individuals in the Domain Bacteria. The abundance of P. putida was low in the headwater region of the river, perhaps because of lower concentrations of aromatic compounds. 3 The abundance of members of the Domain Bacteria peaked in the upper and lower orders of the river and were low in the mid-orders, where protozoa were numerous. 4 Higher DOC quality (based on bacterial growth) in the headwaters and peak protozoa numbers in the mid-section of the river, may have contributed to the spatial patterns observed in the bacterial assemblage. Results suggest that there is a longitudinal pattern of changing relationships between labile DOC, protozoa and bacteria but that, within the bacterial assemblage, species differ in their responses.

Determining Primary Productivity of Lake Roosevelt with 14 C

During two sampling trips in 1997, primary productivity was measured at 11 stations in Lake Roosevelt using a radioactive carbon tracer capable of determining subtle changes in water quality. Both spatial and temporal variations in productivity were observed. For the August 1997 field trip, productivities on the mainstem reservoir ranged from 485 to 1,243 mgC/m2/d, with an average value of 783 mgC/m2/d. Temporal differences between the August and October trips varied by as much as 880 mgC/m2/d. The data are compared to measurements taken over a four-year period to determine subtle, long-term changes in the water quality. Productivity at Lake Roosevelt is heavily influenced by tributary inflow, and generally increased in the reservoir reaches below the mouths of the tributaries. Mainstem sites between the tributaries had lower productivities than the upstream and downstream tributary sites, indicating that nutrients may be rapidly utilized in the immediate vicinity of the inflows. However, productivities i...

Distribution of trace elements in streambed sediment associated with mining activities in the upper colorado river basin, colorado, USA, 1995-96

Streambed-sediment samples were collected in the Southern Rocky Mountains physiographic province in the Upper Colorado River Basin in Colorado to characterize the occurrence and distribution of trace elements in mined and nonmined areas of the basin. During October 1995 and September 1996, streambed sediment was collected at 37 sites, and the samples were analyzed for trace elements. The ranges in concentrations of As, Cd, Cu, Pb, and Zn at mining sites generally were orders of magnitude higher than the ranges of concentrations at nonmining sites. Sampling sites located in two predominant rock types in mining areas were not significantly different (p > 0.05) for concentrations of As, Cd, Pb, and Zn. Cu was significantly different (p < 0.05) between sites in the two predominant rock types. Concentrations of As, Cd, Cu, Pb, and Zn were not significantly different (p > 0.05) between main-stem sites and tributary sites. Concentrations of As, Cd, Cu, Pb, and Zn exceeded established guidelines for adverse effects on aquatic biota at some sites in the study area. The patterns in concentrations of Cd and Zn, Cd and Pb, and Pb and Zn were highly correlated to one another in this study. Concentrations of trace elements in the <63-&mgr;m fraction were higher than in the total particle-size fraction analysis. Comparison of reference sites to sites affected by a mine source indicated that trace-element concentrations initially increased downstream of the source and then gradually decreased in concentration with distance from the source.http://link. springer-ny.com/link/service/journals/00244/bibs/37n1p7.html

A mass-balance approach to quantifying the importance of in-stream processes during nutrient transport in a large river catchment

The importance of riverine processes in the River Swale catchment in Yorkshire, UK, have been assessed during three intensive monitoring campaigns of approximately 100-h duration in the autumn, spring and winter of 1995/1996. This was done by monitoring dissolved silicon, calcium, soluble phosphorus, nitrate, nitrite, ammonium and total phosphorus concentrations at 2-h intervals at the main river and major tributary sites and daily at 15 minor tributaries. These data, together with water discharge data from gauging stations on the main river and major tributaries as well as manual measurements of the minor tributaries, have been used to calculate mass-balances. The difference between the inputs and outputs from the section, enable within-reach losses and gains to be estimated and compared with the water-balance for the river. Dissolved silicon was relatively conservative compared with calcium which did show losses from the river water in the Spring and Autumn, probably associated with precipitation of calcite. Relatively large decreases in soluble phosphorus were found which may be associated with uptake by bed-sediments and riverine flora during conditions of low-flow. Uptake of soluble phosphorus by suspended sediments was also important in a storm event as shown by increases in the mass-balance of particulate phosphorus. Mass-balances for nitrate indicated smaller changes compared with dissolved phosphorus, with losses in the autumn, gains in the spring and little evidence of riverine processes in the winter storm. Ammonium was also lost from the water during all three campaigns but not in sufficient amounts to account for concomitant increases in nitrate or nitrite by nitrification. Exports of soluble reactive phosphorus, total phosphorus and nitrate were calculated for each of the campaigns. The export of total phosphorus was compared with predicted values using suitable export coefficients for different land-use in the UK. The results are consistent, with the export predictions falling in the measured ranges for the catchments. The exports of nitrate were particularly large during the storm event compared with literature data for annual exports.

Multiscale Analysis of Natural Variability in Stream Fish Assemblages of a Western Great Plains Watershed

Much debate about natural variability of stream fish assemblages may stem from investigating them at different spatial and temporal scales, and analyzing data of different resolution. We assessed variability of stream fish assemblages over an 11yr period in a southeastern Colorado plains watershed based on surveys of 12 river and five tributary sites during 1983/1984, 1987/1989, and 1993/1994, and surveys of 40-48 pools along five tributaries during the last two periods. We analyzed across space and time using species presence/absence and relative abundance to assess how conclusions depended on scale and resolution of data. Assemblage similarity through time based on both types of data was higher for whole river or tributary faunas than at individual sites, because rare species that occurred sporadically at sites were consistently present at larger spatial scales. Assemblage similarity among river sites based on species presence/absence was moderate during 1987 and 1993 but lower during 1983 because of differences in passive sampling gear used. It was also low among tributary pools because of spatial variability in both rare and common species. In contrast, assemblage similarity among river sites based on species relative abundance was high for each survey because the same species were dominant but was often low at individual sites among surveys because of an unexplained 92% decline in Cyprinella lutrensis abundance from 1983 to 1993. Assemblage similarity among tributary pools based on species relative abundance in 1993/1994 was high for two tributaries where Lepomis cyanellus was dominant but low in others where it was often absent. The greatest change through time in assemblages at most tributary sites was apparently caused by drought after 1987/1989, which eliminated small pools and limited opportunities for recolonization. Conclusions about the natural variability of these fish assemblages depended strongly on scale, emphasizing the importance of multiscale investigations.

Composition and spatial organization of fish assemblages in the lower Guadiana basin, southern Iberia

Abstract— A survey of fish assemblages (composition and spatial organization) was made in the lower Guadiana basin (southern Iberia) during the summer of 1994. A total of 6937 specimens belonging to 18 species were collected in 44 channel units and 30 sites (i. c. a series of channel units), comprising all the freshwater species previously recorded in the area except the exotic Esox lucius and the endemic endangered cyprinid Anaecypris hispanica. The endemic cyprinids Chondrostoma lemmingii and Barbus sclateri were rarely encountered, whereas the exotic Lepomis gibbosus was the predominant species found. The lower Guadiana fish community changed in space from assemblages characterized by the high relative abundances of Leuciscus pyrenaicus, smaller size‐classes of Barbus spp. and Tropidophoxinellus alburnoides (all Iberian endemisms), to assemblages characterized by the high relative abundances of L. gibbosus, Micropterus salmoides, Cichlasoma facetum (all exotic species) and the larger size‐classes of Barbus comiza and Barbus microcephalus. The former assemblages used smaller (i. e., narrow and shallow) sites and channel units, usually in tributaries and closer to headwaters, with smaller L. pyrenaicus being dominant in sites located in the tributaries discharging to the brackish Guadiana. This group was also related to channel units rich in emergent macropthytes. The latter assemblages were related to the largest sites and channel units, typically found in the main river or in tributary sites far from the source. Besides these two groups, some species were associated to noticeable environmental conditions; Blennius fluviatilis to channel units with current velocity and heterogeneous substrate, typically found in the main river, and Cobitis paludica to channel units with heterogeneous substrate.

Results of a prototype surface water network design for pesticides developed for the San Joaquin River Basin, California

A nested surface water monitoring network was designed and tested to measure variability in pesticide concentrations in the San Joaquin River and selected tributaries during the irrigation season. The network design and sampling frequency necessary for determining the variability and distribution in pesticide concentrations were tested in a prototype study. The San Joaquin River Basin, California, was sampled from April to August, 1992, a period during the irrigation season where there was no rainfall. Orestimba Creek, which drains a part of the western San Joaquin Valley, was sampled three times per week for 6 weeks, followed by a once per week sampling for 6 weeks, and then three times per week sampling for 6 weeks. A site on the San Joaquin River near the mouth of the basin, and an irrigation drain of the eastern San Joaquin Valley, were sampled weekly during the entire sampling period. Pesticides were most often detected in samples collected from Orestimba Creek. This suggests that the western valley was the principal source of pesticides to the San Joaquin River during the irrigation season. Irrigation drainage water was the source of pesticides to Orestimba Creek. Pesticide concentrations of Orestimba Creek showed greater temporal variability when sampled three times per week than when sampled once a week, due to variations in field management and irrigation. The implication for the San Joaquin River basin (an irrigation-dominated agricultural setting) is that frequent sampling of tributary sites is necessary to describe the variability in pesticides transported to the San Joaquin River.

Species traits in relation to temporal and spatial heterogeneity in streams: a test of habitat templet theory

1. The habitat templet approach depends on defining templet axes appropriate to the organism(s) of interest, predicting the traits of species associated with different parts of the templet, and testing these predictions in a range of habitats whose positions in the templet have been determined.2. In this study of thirty‐five benthic insect taxa at fifty‐four tributary sites of the Taieri River on the South Island of New Zealand, we chose as the temporal axis the intensity/frequency of disturbance, defined in terms of bed movement during high discharge events. As the spatial axis, we postulated that three features would provide refugia and therefore ameliorate disturbance—percentage of the bed with low shear stress, percentage of the bed made up of large substratum particles and availability of interstitial space in the bed—from which we derived a combined multivariate refugium axis.3. More disturbed communities contained a significantly higher percentage of individuals possessing the following traits: small size, high adult mobility, habitat generalist (each predicted to confer resilience in response to disturbance), clinger, streamlined/flattened and with two or more life stages outside the stream (each predicted to confer resistance in the face of disturbance). When analyses were performed on the percentage of taxa having particular traits, the predicted positive relationships with average bed movement were found for high adult mobility and habitat generalist traits.4. The percentage of variance in trait scores explained by intensity of disturbance was generally higher in sites with less refugia available and lower in sites further from the headwaters. The percentage of variance explained was higher in sites recently subject to a major high discharge disturbance, suggesting that disturbances tend to strengthen the pattern of preponderance of resilience/resistance traits.5. We mapped insect taxa onto the two‐dimensional templet, following Grime et al.’s triangular terrestrial plant classification. The full variety of resistance and resilience traits were represented in insect species throughout the templet, but taxa associated with more disturbed conditions generally displayed a larger number of resilience and resistance traits, combined, than taxa associated with more stable stream beds.

Relative effects of in‐stream habitat and land use on fish distribution and abundance in tributaries of the Grey River, New Zealand

Abstract The distribution and abundance offish was investigated over 2 years at 78 sites in Redjacks Creek and adjacent tributaries draining native, exotic, and mixed forest catchments within the Grey River system, South Island, New Zealand. The abundance of diadromous fish decreased with altitude and distance from the sea, whereas the abundance of non‐diadromous fish species, especially dwarf galaxias (Galaxias divergens), increased with altitude and distance from the sea. Species abundance varied with average stream depth and velocity, generally in accordance with micro‐habitat preferences. The relative influences of diadromy, land use, and physical habitat on fish distribution and abundance were difficult to separate. Differences in fish abundance in the three land‐use categories were often attributable to differences in physical habitat. Nevertheless, there were indications that land use and its effect on the stream environment was influencing the distribution of some fish species. Ammocoetes (Geotria...

A Rapid Assessment Procedure for the Enumeration of Salmonine Populations in Streams

Abstract Population enumeration is a key component of fisheries investigations for riverine salmonines. We examined the reliability of a rapid population assessment technique for stream salmonines that depends on a single episode of electrofishing rather than traditional multiple fishing, removal, or mark–recapture methods. We show that for 12 sites sampled in 1992 on Wilmot Creek, a small, coldwater tributary to Lake Ontario, the catch of salmonines from a single electrofishing episode predicted the population estimate obtained with a more time-consuming multiple-pass removal method. When we collected similar data from eight additional Lake Ontario tributary sites in 1994, the relationship was not significantly different from that obtained in 1992. We also conducted nonparametric analyses of covariance on subsets of these data and found no significant differences in the above relationship for rainbow trout Oncorhynchus mykiss versus brown trout Salmo trutta or for age-0 versus older fish, although the st...

Chlorophyll content of seston in a regulated Rocky Mountain river, Idaho, USA

The chlorophyll content of seston at four sites in a regulated mid-order Rocky Mountain river, Henry's Fork of the Snake River, Idaho, USA, was examined. Spectrometry was used to determine the amount of chlorophyll a, b, c and in seston and potential organic matter sources including macrophytes, algae, plankton, and terrestial plant litter. The amount of chlorophyll in seston varied among size fractions, sites, and seasons. Coarse seston (6–1 mm) contained the most chlorophyll a (2.3 mg g−1 ashfree dry mass [AFDM]) followed by ultra fine seston (53–0.3 µm; 1.9 mg g−1 AFDM), very coarse seston (> 6 mm, 1.8 mg g−1 AFDM), very fine seston (250–53 µm; 1.3 mg g−1 AFDM), and fine seston (1–0.25 mm; 0.7 mg g−1 AFDM). Chlorophyll content of coarse seston was similar at all sites reflecting a common source, aquatic macrophyte debris. Chlorophyll content of coarse and fine seston were highest in fall reflecting the importance of phenology of aquatic plants on sestonic pigment levels. Very fine seston from below a reservoir contained more chlorophyll than seston from downstream and tributary sites suggesting a reservoir source. Terrestial plant litter was chlorophyll depleted compared to autochthonous materials and seston. Most seston was autochthonously-derived from a variety of macrophyte, algal, and planktonic sources. The chlorophyll content of Henry's Fork seston was higher than that reported for similar rivers. Island Park Dam moderates river temperature and flow, enhances autotrophy, and accounts for the consistently high sestonic chlorophyll levels.

Selenium source identification and biogeochemical processes controlling selenium in surface water and biota, Kendrick Reclamation Project, Wyoming, U.S.A.

The major tributaries draining the Kendrick Reclamation Project (KRP) account for an average of 52% of the total Se load measured in the North Platte River downstream from Casper, Wyoming. The Casper Creek drainage basin contributed the largest Se load of the five tributary sites to the North Platte River. The 4-d average Se concentration in water samples from one site in the part of the North Platte River that receives irrigation return flows exceeded the 5 μg/l U.S. Environmental Protection Agency's aquatic life criterion five time during a 50-d monitoring period in 1989. In agreement with the water-quality data, muscle and liver tissue rom rainbow trout collected from the same part of the North Platte River had Se concentrations exceeding levels known to cause reproductive failure and chronic Se poisoning. On the basis of Se: Cl, 18O/ 16O and D/H ratios in water from Goose and Rasmus Lee Lakes (closed-basin systems), the large Se concentrations in those lakes were derived by natural evaporation of irrigation water without leaching of soluble forms of Se from soil or rocks. Water samples from Thirtythree Mile Reservoir and Illco Pond (flow-through systems) showed considerable enrichment in Se over evaporative concentration, presumably due to leaching and desorption of Se from soil and rock. The Se: Cl ratios of irrigation drain water collected from the KRP indicate that leaching and desorption of soluble forms of Se from soils and rocks are the dominant processes in drain water. Results of a Wilcoxon matched-pairs test for 43 paired drain-water samples collected during June and August 1988, indicated there is a statistically larger concentration of Se (0.01 significance level) during the June sampling period. The larger concentrations of Se and other chemical constitutents during the early part of the irrigation season probably were due to dissolution of seleniferous salts that have accumulated in soils within the KRP since the last irrigation season. The large Se concentrations in water samples from wetland sites in the KRP were reflected in the aquatic-bird food chain. Most waterfowl and shorebirds nesting at the KRP showed Se concentrations in livers and eggs greater than levels suspected of causing adverse reproductive effects.

Biological availability of dissolved organic carbon along the Ogeechee River

Quality of dissolved organic C (DOC) from main‐stem and tributary sites along the Ogeechee River was compared to that of chemically defined organic C substrates in terms of biological availability. Availability was determined by measuring bacterial growth on natural river water (collected at high and low discharges) and defined organic substrates (humic standards and high‐quality sources of C). Availability of DOC to the natural (native) stream bacterial assemblage was compared to that of a defined bacterial inoculum, selected for ability to readily utilize high‐quality substrates. Availability of DOC declined downriver, and DOC in highly colored tributaries was of lower quality than DOC from other sites. In most cases, quality of DOC decreased at high discharge.

Effect of land use on the distribution and abundance of native fish in tributaries of the Waikato River in the Hakarimata Range, North Island, New Zealand

Abstract The effect of land use on fish community structure was examined at fifty‐five sites in tributaries draining exotic, indigenous forest and pastoral catchments in the Hakarimata range in March and April 1987. Using a model containing percentage woody debris, temperature, and substrate coarseness, 76% of the sites were classified into correct land uses by discriminant analysis. This indicated that differences in stream habitat, and hence of the fish fauna, were related to effects of changed land use rather than other confounding physical or geographical features of the streams in the catchments. Tributaries in indigenous forest were numerically dominated by banded kokopu (Galaxias fasciatus) and longfinned eel (Anguilla dieffenbachii), with redfinned bully (Gobiomorphus huttoni) and giant kokopu (G. argenteus) occasionally being caught. Pastoral streams below the forest generally supported higher densities and contained more species including the forested species above, Cran's bully (G. basalis), and shortfinned eel (A. australis). As the amount of indigenous forest in the catchment decreased the fauna became less abundant and less diverse and was dominated by both species of eel and Cran's bully.

LONGITUDINAL AND SEASONAL WATER CHEMISTRY VARIATIONS IN A NORTHERN APPALACHIAN STREAM1

ABSTRACT: Quaker Run, a fourth order stream located in southwestern New York State, exhibits a highly unusual chemical gradient along its upper reaches. Weekly water samples showed an increase in the mean annual pH from 5.07 to 7.01 along a stretch of only 2.2 km. Mean alkalinity, calcium, magnesium, sodium, potassium, nitrate‐nitrite‐nitrogen, silica, and conductivity also increased appreciably over this distance. The study area receives some of the most highly acidic atmospheric deposition in the United States. Minimal buffering of these acidic inputs in the extreme upper watershed, and an abrupt downstream increase in buffering associated with changes in soil type, apparently produce the observed streamwater chemistry gradient. In contrast, a comparison between 11 midstream, downstream, and tributary sites showed relatively little variation in streamwater chemistry. In addition to the pronounced longitudinal chemistry changes along the upper portion of the stream, pronounced temporal chemistry variations were also observed at all sampling sites. High flow during snowmelt and heavy rains produced more dilute, acidic conditions, while streamwater pH and dissolved base cations were generally highest during low flow. Much of this temporal variation in streamwater chemistry is attributed to seasonal variation in residence times of soil water.

Dissolved humic substances of the Amazon River system1

Aquatic humic and fulvic acids from nine mainstem and seven major tributary sites in the Amazon River Basin are characterized by their elemental and lignin phenol compositions. Combined humic substances represent 60% of the riverine dissolved organic carbon (DOC), with fulvic to humic acid (FA : HA) ratios in the mainstem averaging 4.7±1.0. All dissolved humic and fulvic acids have clearly recognizable lignin components at levels (8 and 3% of the carbon) suggesting a predominantly allochthonous source. Lignin compositional characteristics are dominated by diagenetic transformations, which include preferential loss of methoxylated structural units and oxidative degradation of lignin side chains. Fulvic acids have consistently lower lignin levels, lower lignin phenol methoxylation, higher acid : aldehyde ratios, and higher C: N ratios than coexisting humic acids, all indicative of greater aerobic degradation of the fulvic acid fraction. An extreme example of lignin degradation is seen in the Rio Negro humic and fulvic acids, which differ significantly in lignin and elemental compositions from other blackwater tributary and mainstem samples.Over most of the mainstem humic and fulvic acids behave conservatively. However, downstream of the Rio Negro confluence, humic acids appear to be selectively adsorbed onto fine suspended particles. Approximately 25 and 40% of the total fluxes of lignin and of carbon are represented in the dissolved humic substances. The annual flux of dissolved, chemically recognizable lignin in the Amazon River at Obidos is calculated to be 1.2 × 1011 g yr−1.

Recruitment and turnover of populations of brown trout, Salmo trutta, in the upper River Wye, Wales

The age structure, abundance, net immigration and loss of trout populations were investigated in eleven tributary sites and two main river sites on the River Wye. Marking experiments indicated that recruitment to the site populations was mainly by immigration which began during the O‐group phase and continued, with seasonal fluctuations, throughout life. Immigrant fish had a higher probability of being lost from the populations than residents providing a statistical distinction between mobile and sedentary components of the population. The turnover of the site populations is described using a simple exponential model, and half‐times at different sites (stream length, 50 m) ranged from 140 to 430 days. Some factors affecting half‐times are briefly discussed.