Factors Affecting Redd Site Selection, Hatching, and Emergence of Brook Charr, Salvelinus Fontinalis, in an Artificially Enhanced Site

We measured microhabitat characteristics, hatching and emergence success of brook charr, Salvelinus fontinalis, in a series of sites selected and not selected by individuals spawning in an artificially enhanced lake outlet. Differences between the physico-chemistry of surface and interstitial water were small and did not suggest the presence of groundwater seepage. The mean surface water velocity was significantly higher in selected than non-selected sites during the incubation and emergence periods. Differences in interstitial water flow were not detected. Overall, selected substrate was coarser and contained a lower proportion of fine particles than non-selected substrate, as determined by the geometric mean diameter of particles, the proportion of fine particles (<1mm), and the Fredle index. The proportion of fine particles was correlated with sediment loading in incubators. A two-way ANOVA showed no significant effect of sites (selected versus non-selected) but did show a significant effect of the incubation substrate (Astro-turf, selected substrate, non-selected substrate) on both the hatching and emergence success; the percentages of hatching and emergence were significantly higher in Astro-turf than in non-selected substrate, with selected substrate being intermediate. The results of this study suggest that redd site selection by brook charr is based on surface water velocity and substrate characteristics (granulometry and proportion of fine particles) that in turn affect egg survival. It is possible that the lower proportion of fine particles in selected sites (and incubators) is related to their higher water velocity, which could carry away fine particles that reduce the availability of oxygenated water to the embryos. In the same way, higher water velocity could act as a proximate cue in the absence of groundwater seepage or interstitial water flow for individuals to select suitable sites for spawning and egg incubation.     

Dissolved helium distribution in deep groundwaters from the Tono area,central Japan: a tool for tracing groundwater flow in fractured granite

The helium isotopic composition of groundwater collected from boreholes was measured in the Tono area from up to 840m underground. The ³He/⁴He and ⁴He/²⁰Ne ratios ranged from 9.1 × 10^–8 to 1.48 × 10^–6 and from 0.22 to 190, respectively, implying that the groundwater accumulates significant amounts of radiogenic ⁴He as it flows. In groundwater from sedimentary rocks, the levels of accumulated helium increase with depth, whereas those in the samples from fractured granite vary from borehole to borehole. Considering the hydrogeological and topographical model together, dissolved He concentrations in groundwater indicate the groundwater flow direction. Although the groundwater flow in fractured granite is generally thought to be controlled by the fracture pattern, the overall flow of the Tono area inferred from helium isotopes is also controlled by topography.     

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

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

Flow variability and longitudinal patterns in parafluvial water chemistry,aquatic invertebrates and microbial activity

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The influence of groundwater withdrawal and land use changes on brook charr (<Emphasis Type="Italic">Salvelinus fontinalis</Emphasis>) thermal habitat in two coldwater tributaries in Michigan,U.S.A.

Brook charr (Salvelinus fontinalis) is a sentinel fish species which requires clean, cold water habitats. As such, many jurisdictions in the United States where brook charr are present use this species as an indicator of ecosystem health. In Michigan, groundwater-dominated streams are currently being impacted by increased groundwater withdrawal and land use/land cover changes which alter stream temperatures and their flow, and thus have the potential to significantly influence brook charr production and behavior. We quantified the influence of groundwater withdrawal and land use alteration on thermal habitat availability for brook charr using a groundwater modeling tool that estimated changes in baseflow to a stream segment based on changes to the groundwater system due to groundwater withdrawal and changes in rates of recharge related to landscape changes within a watershed. Projected stream temperature changes were calculated using a stream temperature modeling tool and compared to the range of temperature preferenda for brook charr in order to evaluate the potential impact of policy decisions regarding water extraction and land use/cover changes. The models predicted relatively small changes in both stream baseflow and consequently, stream temperature, with increased groundwater withdrawal rates. Land use/land cover alterations which we analyzed were shown to either mitigate or enhance the loss of brook charr thermal habitat as a result of groundwater withdrawal, depending on its relationship to recharge dynamics. This study emphasizes the importance of collaboration between water, land, and fisheries managers to ensure brook charr population viability, productivity, and sustainability in the face of environmental change, increasing water use and development in the watershed.     

The Effects of an Environmental Flow Release on Water Quality in the Hyporheic Zone of the Hunter River,Australia

Environmental flow releases have been advocated as a useful rehabilitation strategy for improving river condition but assessments of their success have typically focused on surface water quality and biota. In this study, we investigated the impacts of an environmental flow release on water temperature, conductivity, dissolved oxygen, and nitrate concentrations in surface and subsurface (hyporheic) water at upwelling and downwelling zones in three sites along the Hunter River, New South Wales, Australia. We hypothesised that the flow pulse would ‘flush’ the sediments with oxygenated water, stimulating hyporheic microbial activity and nitrification, enhancing nitrate concentrations over time. Surface and subsurface samples were collected before, 7 days after, and 49 days after an environmental flow release of 5000 Ml for a period of 3 days. No lasting effects on dissolved oxygen or conductivity were evident at most sites although dissolved oxygen declined over time at the downwelling site at Bowmans Crossing. At the downwelling zones at all sites, hyporheic nitrate concentrations declined initially following the release, but then rose or leveled off by Day 49. This initial drop in concentration was attributed to flushing of nitrate from the sediments. At two sites, nitrate concentrations had increased by Day 49 in the upwelling zones while at the third site, it fell significantly, associated with very low dissolved oxygen and likely reductive loss of nitrate. Electrical conductivity data indicate that potential inputs of agriculturally enriched groundwater may contribute to the nitrogen dynamics of the Hunter River. This study highlights the spatial heterogeneity that occurs in the hyporheic zone within and among sites of a regulated river, and emphasises the need for multiple-site surveys and an understanding of groundwater dynamics to assess physicochemical responses of the hyporheic zone to environmental flow releases.     

Alternative tactics in spawning site selection by brook trout (Salvelinus fontinalis) related to incubation microhabitats in a harsh winter environment

1. Species with distributions that span a broad range of latitudes may have populations that exhibit distinct life history traits associated with environmental gradients. The majority of previous studies have indicated a strong association between spawning site selection by brook trout (Salvelinus fontinalis) and the presence of upwelling groundwater, but does this generalisation extend to the thermal regimes experienced at northern sites? 2. We investigated the role of hyporheic flow in redd site selection by brook trout in a relatively high‐latitude boreal system. Hyporheic flows through streambed substratums can be dominated by groundwater or surface water and may be influenced by the presence of morphological features. For autumn spawners such as brook trout, embryos situated in microhabitats where hyporheic flow in the shallow substratum is groundwater dominant (i.e. warmer in winter) are likely to experience accelerated development rates relative to embryos in redds where there is downwelling surface water (i.e. colder in winter). 3. We measured vertical hydraulic gradients (VHG) at the microhabitat scale and spatial and temporal variation in upwelling/downwelling flow and thermal regimes in brook trout spawning/incubation habitats. Additionally, we noted the proximity of redd sites to stream morphological features (e.g. riffle crests). 4. Our results indicate that upwelling flow was not a decisive cue in redd site selection at the microhabitat scale (10⁰ m) as an approximately equal number of redds were situated in microhabitats with upward flow as compared to microhabitats with downward flow through the redd. Redds situated on bedforms with convex longitudinal profiles (e.g. riffle crests, log steps) were associated with downward flow, whereas redds not immediately adjacent to these bedform features were associated with upward flow. Winter streambed temperatures confirmed that both sites with steady upwelling (i.e. warm incubation regime) and downwelling (i.e. cold incubation regime) were indeed selected by spawners. 5. Our observations that spawners utilised both cold‐regime and warm‐regime sites suggests the existence of distinct reproductive tactics related to hyporheic flow patterns in this boreal system. As temperature is the dominant factor controlling rates of embryonic development, the use of spawning microhabitats with distinct thermal regimes implies substantial differences in the timing of hatching and the phenology of emergence.     

The Chironomid Communities of Woodland Springs and Spring Brooks, Severely Endangered and Impacted Ecosystems in a Lowland Region of Eastern Germany (Diptera: Chironomidae)

The distribution of chironomid species from four springs and twelve spring brooks in a region heavily affected by industrial activity in eastern Germany was studied. The aims were (1) to document the chironomid taxa communities at the species level, as far as possible, and the most important environmental factors of representative springs and spring brooks of the region, (2) to analyse the distribution of the ecological groups within these small ecosystems and (3) to emphasize the importance of the protection of spring areas and spring brooks in this woodland area shown by the chironomid fauna. There was high degree of abiotic variation among the water bodies, with pH ranging from 2.79 to 6.89. While diversity did not correlate with pH nor with conductivity, significant differences existed between the spring mouth and the reaches some metres downstream with respect to several abiotic parameters and the distribution of the chironomids: oxygen concentrations and taxonomic diversities were higher in spring brooks (2.18–8.98mgO₂/l; 5–28 taxa) than in the spring areas (0.13–2.95mgO₂/l; 0–7 taxa). A total of 74 chironomid taxa were recorded. The chironomid communities are characterized by the presence of rheophilic, cold-stenothermic, crenophilic and sometimes tyrphophilic elements in each site. The data show that each of the spring–spring brook systems surveyed is unique both in biotic and abiotic respects. As the spring system is sensitive to changes in landscape functions (e.g. groundwater levels), the fauna can serve as an indicator of landscape health. Therefore, these small ecosystems should be conserved as a reference.     

Effects of flooding duration on species richness, floristic composition and forest structure in river margin habitat in Amazonian blackwater floodplain forests: implications for future design of protected areas

Rivers in central Amazonia experience annual water-level fluctuations of up to 14m, flooding vast areas of adjacent forest for periods ranging from a few to 270 days per year. At different sites, variation in the duration and type of flooding results in a mosaic of habitats that includes lakes, grasslands, forests, and streams. To study the effects of flood duration on plant species richness and floristic composition, two river margin sites were surveyed on the rivers Jaú and Tarumã-Mirim. Both areas are seasonally flooded by blackwaters, and plots were made at different topographic levels (lower, middle and upper slopes). All woody plants with DBH>5cm were inventoried in five 10 × 40m plots in each of the three topographic levels, which varied in length of flood duration and mean water level. Plant species richness did not vary significantly between topographic levels, but species composition varied substantially. At both study sites, the species composition exhibited distinctive distribution patterns with respect to the three topographic levels and river site. Differences in the distribution of dominant species in both sites probably relate to the ability of species to withstand seasonal flooding, although other edaphic factors associated with the topographic levels may also be important, especially for less-dominant, locally rare, and habitat generalist species. Species composition overlap among topographic levels at the two sites was highly variable ranging from 15% to 43%. Knowledge about the complex pattern of species composition and distributions between and among topographic levels and river sites is important for the preservation of the diverse flora of the blackwater forests and for the creation of future conservation management plans and design of protected areas in this ecosystem that will maintain the biodiversity.     

Influence of Intermittent Hydropeaking on the Longitudinal Zonation Patterns of Benthic Invertebrates in a Mountain Stream

The longitudinal zonation patterns of invertebrate species were studied in the River Oriège (Pyrénées, France) from 920 to 819 m a.s.l. At 912 m a.s.l., the river receives hypolimnetic water diverted from a nearby reservoir lake, and the natural flow may be enhanced several times a day from 1 to 11 m³ s^—1 in summer and winter, and from 5 to 15 m³ s^—1 during spring spates. During hydropeaking, the water was cooled in summer and slightly warmed in winter, but this was attenuated 3500 m downstream from the plant. Invertebrate densities were recorded in July (end of spates) and October (low flow period) at ten sampling sites : a reference site upstream of the hydrostation's discharge point (site 1), and nine sites each 400 m below the outlet (sites 2—10). The longitudinal distribution of invertebrate taxa was studied using Factorial Analyses, taxa and sites were clustered using Analysis of Dynamic Cluster. The hydroelectric facility did not clearly modify the qualitative composition of the benthic fauna, but clearly affected the longitudinal zonation of several populations. The low abundance of several species below the outlet reflected the impact of both hydropeaking and zonation. These species were high mountain species, the density of which decreases towards downstream sites in the Pyrenees, and low mountain species, the density of which naturally decreases towards upstream sites. Some taxa disappeared in the regulated section, so their distribution in the River Oriège was primarily influenced by hydropeaking. Finally, some taxa preferentially lived in the lower section of the river where the impact of peaking flows was strongly attenuated, so their longitudinal distribution was first governed by their natural longitudinal zonation. Under this kind of river regulation (natural discharge and temperature except during periods of power generation, intermittent hydropeaking from a separate reservoir) modifications of the thermal regime had a minor effect on the population dynamics, unlike hydraulic disturbances which strongly influenced the structural attributes of benthic communities.     

Root water uptake of field-growing plants indicated by measurements of natural-abundance deuterium

Measurements of stable-isotope ratios of water extracted from stems and, in some studies, soils are increasingly being used to study the integrated root function of field-growing plants. This study explored if additional measurements on water extracted from roots could indicate the activity of roots in different areas of the soil profile and their influence on canopy water sources, so providing advantages over more common sampling strategies. Studies were conducted on trees and shrubs located in diverse habitats: a saline, semi-arid floodplain, a subhumid mountain-range front and a cold desert. At each site, roots, soil immediately surrounding the roots, and plant stems were sampled. Roots were taken from different depths in the soil, to approximately 2 m at one site. Overall, 80% of roots sampled had H isotope ratios different from the surrounding soil. The differences up to 37, were significant (p<0.05) at two of the sites. Thus water in most of the roots sampled did not come entirely, if at all, from the surrounding soil, illustrating movement and possible mixing of water within the root system. This condition was not simply related to the availability of water surrounding the soil, which was also measured. There were also differences in root and stem H isotope ratios (up to 17) in 67% of samples, although the difference was only significant in shallow samples from the floodplain. The general similarity in stem and root ²H values indicates that most roots sampled were involved in the main supply of water to the canopy. Patterns of root function varied between the individual sites. Trees were primarily using groundwater at the floodplain and mountain front sites, as the surface soils had mean matric potentials of-1800 kPa. At the mountain front site, the surface roots were transporting groundwater to the canopy in isolation form the surrounding soil. In contrast, surface roots at the floodplain were taking up water from the surrounding soil, although this water was not a significant source in the trees' overall water supply. This activity of surface roots would not have been evident from the ²H data without the root samples. At the cold desert the roots in moist surface soil provided the main source of water for the shrubs. There too the root data indicated different water uptake patterns than otherwise would have been assumed. The root data showed that groundwater could not have been a water source, a conclusion which had been reached in a previous study. Thus measurements of stable isotope ratios in root water may be a valuable tool in assessing water uptake patterns and root function.     

Wide-Area Estimates of Stand Structure and Water Use of Tamarix spp. on the Lower Colorado River: Implications for Restoration and Water Management Projects

Tamarix spp. removal has been proposed to salvage water and allow native vegetation to recolonize western U.S. riparian corridors. We conducted wide‐area studies on the Lower Colorado River to answer some of the scientific questions about Tamarix water use and the consequences of removal, combining ground surveys with remote sensing methods. Tamarix stands had moderate rates of evapotranspiration (ET), based on remote sensing estimates, averaging 1.1 m/yr, similar to rates determined for other locations on the river and other rivers. Leaf area index values were also moderate, and stands were relatively open, with areas of bare soil interspersed within stands. At three Tamarix sites in the Cibola National Wildlife Refuge, groundwater salinity at the site nearest to the river (200 m) was relatively low (circa 2,250 mg/L) and was within 3 m of the surface. However, 750 and 1,500 m from the river, the groundwater salinity was 5,000–10,000 mg/L due to removal of water by the Tamarix stands. Despite the high groundwater salinity, the sites away from the river did not have saline surface soils. Only 1% of the mean annual river flow is lost to Tamarix ET on the Lower Colorado River in the United States, and the opportunities for water salvage through Tamarix removal are constrained by its modest ET rates. A possible alternative to Tamarix removal is to intersperse native plants among the stands to improve the habitat value of the riparian zone.     

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.     

Changes in agricultural intensity and river health along a river continuum

1. The impact of agricultural activities on waterways is a global issue, but the magnitude of the problem is often not clearly recognized by landowners, and land and water management agencies. 2. The Pomahaka River in southern New Zealand represents a typical lowland catchment with a long history of agricultural development. Fifteen sites were sampled along a 119-km stretch of the river. Headwater sites were surrounded by low-intensity sheep farming, with high-intensity pasture and dairying occurring in the mid-reach and lower reaches. 3. Water clarity decreased significantly from about 6 m in the headwaters to less than 2 m in the lower reaches. Benthic sediment levels increased significantly downriver, peaking at 35 mg m^??2 below several tributaries with high-intensity agriculture in their catchments. Periphyton levels were also significantly greater in the lower reaches than the headwaters, and coincided with increased nitrogen (DIN) and phosphorus (SRP) concentrations. 4. Macro-invertebrate species richness did not change significantly throughout the river, but species composition did with Ephemeroptera, and to a lesser extent, Plecoptera and Trichoptera dominating the headwater sites (where there was high water clarity, and low nutrient and periphyton levels). Downriver these assemblages were replaced by molluscs, oligochaetes and chironomids. 5. Canonical correspondence analysis indicated that agricultural intensity and physical conditions associated with agriculture activity (e.g. impacted waters, high turbidity and temperature) were strongly associated with the composition of benthic assemblages at differing reaches down the Pomahaka River. 6. The present results indicate that quantifying agricultural intensity within a catchment, particularly relative livestock densities, may provide a useful tool for identifying threshold levels above which river health declines.     

物种多样性及生物量与地下水位的关系——以海流兔河流域为例

以3条样带上117块植被群落调查样方为基础资料,研究了海流兔河流域植被物种多样性及生物量与地下水位之间的关系。结果表明:1)地下水位高低及地貌类型均会影响草本层植物群落组成及优势种构成。滩地样地中,随地下水位降低,优势草本的更替方向为寸草,芨芨草,马蔺,狗尾草,碱茅;沙坡样地中,优势草本的更替方向为大针茅,沙鞭,沙蓬,沙打旺。2)地下水位为1.5 m时是草本植物群落生长发育最适宜区域,物种多样性及丰富度达到最大,而灌木层物种多样性及丰富度随地下水位下降呈现波动变化的特征;当地下水位埋深小于5.0 m时,草本层物种多样性及丰富度明显高于灌木层,在地下水位埋深大于5.0 m时,草本层物种多样性指数开始出现低于灌木层的现象。3)草本植物多样性及丰富度和生物量之间关联性不强,滩地样地中,草本层地上生物量及地下生物量在地下水位为1.8 m时具有最大值,但植物群落结构较为单一;沙坡样地中,地上生物量最大值出现在地下水位为5.0 m的区域内,而地下生物量最大值出现在地下水位为3.5 m时。综上,物种多样性、地上及地下生物量与地下水位都不是简单的线性关系,而是有一个最适水位;高于或低于这个最适水位,多样性和生物量都会下降。     

The aquatic macrophytes of an English lowland river system: assessing response to nutrient enrichment

Assessment of the effects of nutrients in running water upon macrophytes is compounded by the variety of additional environmental factors which influence their growth. Some classification schemes have been effective in detecting eutrophication on a national or regional scale, and also downstream changes in large single catchments. However, in lowland rivers with naturally nutrient-rich geologies, detection of change at smaller spatial scales has been difficult. This study examined the macrophyte community at 44 sites on the river Welland, a small lowland catchment rising below 150 m in Leicestershire, England. The community at 23 of these sites was adequate for further analysis. The data show that the clearest effect on community composition is caused by watercourse size. However, sites below sewage works, even small village works, did show a reduction in Mean Trophic Rank, (MTR – an assesment system introduced into the UK over the last three years using a 10–100 scale based upon scores and cover value of indicator species). Overall there was a slight but significant correlation of MTR with soluble phosphate and nitrate. The effectiveness of the MTR method is limited at full catchment scale by low numbers of the indicator taxa at small upstream sites. Catchment-scale assessment of the plant community is probably best served by more detailed phytosociological analysis and by the further development of the habitat templet approach.     

Water utilization of tropical hardwood hammocks of the Lower Florida Keys

Summary Predawn water potential of representative plant species, together with stable isotope composition of stem water and potential water sources were investigated in four low-elevation tropical hardwood hammocks in the Lower Florida Keys, during a one year period. Hammock species had the lowest water potentials when soil water content was low and/or soil salinity was high, but differences in groundwater salinity had no effect on the water potential. Comparison of D/H ratio of plant stem water with soil and ground water corroborates the conclusion that they are primarily utilizing soil water and not groundwater. Thus, tropical hardwood hammocks are buffered from saline groundwater, and are able to thrive in areas where groundwater salinity is as high as 25. The effect of sea level rise on these forests may depend more on changes in the frequency of tidal inundation of the soil surface than on changes in groundwater salinity.     

Growth and survival of tadpoles (Bufo americanus) fed amorphous detritus derived from natural waters

Growth and survival of tadpoles (Bufo americanus) were used to assess the food value of three types of amorphous detritus thought to be derived from dissolved organic matter (DOM) transported in river water or groundwater: 1. Flocculent organic aggregates suspended at the mouth of a humic stained river which drains into Lake Superior; 2. Precipitates formed directly from humic stained river water; 3. The < 35 m fraction of littoral lake sediment. Tadpoles were unable to grow when fed the amorphous detritus, but experienced lower mortality than unfed animals. Although the food quality of certain types of detritus derived from DOM may be inadequate to support the growth of aquatic fine particle feeders it may contribute to the nutrition of facultative detritivores.     

Monitoring organic enrichment of rivers using chironomid pupal exuvial assemblages

Exuvial samples were collected at stations above and below organic effluent inflows at twenty river sites near Bristol, England, during May, July and September, 1989.Exuvial sample data for each station were amalgamated and related to chemical data obtained from the Wessex and the Severn-Trent Regions of the National Rivers Authority. Principal Components Analysis (PCA) and Canonical Community Ordination (CANOCO) were used to derive biplots of taxa and selected environmental factors. From these biplots, lists of taxa were obtained, and ranked in order of closeness of association to selected organically-related environmental factors. Lists of principal taxa, either positively or negatively associated with a given environmental factor, were termed indicator assemblages in respect of that factor.The rank orders of similarity of these indicator assemblages to amalgamated exuvial samples from 51 stations on the River Trent, were significantly correlated (p<0.001) to the same stations ranked in order of ammonia concentrations and biological oxygen demand (BOD.).     

Copper contamination in the Patuxent River,Maryland

Copper contamination was studied in the Patuxent River, Maryland, which flows from the western shore of the Chesapeake Bay. The only heavy industry on this river is a coal-fired power plant situated 35 km from the river mouth. The plant uses river water for cooling purposes and had been implicated in early studies as a source of localized copper pollution from copper: nickel condenser tubing. Average cooling water usage exceeded average natural river flow over the study period by a factor of 3. This investigation showed high levels of both dissolved and particulate copper at this point source, with a high ratio of particulate: dissolved copper at the point of discharge. A copper budget achieved through comparison of industrial intake/outflow data showed that when natural river flow was considered, output from this single point source could conservatively account for a total copper concentration in the river of 6.7 g 1^–1 above background. This considerably exceeded the measured figure of 2.6 g 1^–1 (relative to the upstream station). Part of this discrepancy was probably due to copper deposition close to the power plant. Although copper concentrations declined downstream from this source, they still remained high in absolute terms and were comparable with a much more heavily industrialized river system. Even at the river mouth, copper concentration remained elevated and it was speculated that anti-fouling paints associated with heavy recreational boat traffic may be particularly responsible for this.