Invertebrate drift in a glacial river and its non-glacial tributary

1. Invertebrate drift was studied in a glacially fed river and a non-glacial tributary in western Norway. Samples were taken during two consecutive 24-h periods in May, July and October 1997. The 3 months are characterized by snowmelt, ice melt and rainfall runoff, respectively. The main glacial river has colder, more turbid water, especially during the period of maximum ice melt during summer.
2. Chironomidae, especially the genus Diamesa , dominated the drift in the main river in May and October, constituting 97 and 99% of total numbers, respectively. Simuliidae, Plecoptera, Ephemeroptera and Trichoptera were the other main components.
3. A comparison of drift and benthos data revealed that the tributary was of little significance for colonization of the main glacial river. Only some additional species in very low numbers were recorded downstream of the confluence.
4. During July significant differences in diel drift pattern of Chironomidae and Simuliidae existed between the glacial and non-glacial reaches. There was a mid-day peak independent of discharge in the glacial river, but this peak was not noted in the tributary. Species of the genus Diamesa appear to be adapted for daytime drift, possibly evolved through the absence of predators and competitors that are typical of rhithral systems where nocturnal drift is more usual.     

A numerical analysis of counts of diatom frustules,and other algae,in water samples from the River Wey

During May 1978, samples of water were collected from 24 sites on, or associated with, the River Wey between its source south of Haslemere and Send just downstream of Guildford (approx. 57.5 km). Counts of diatom frustules, and other algae surviving the sampling technique, were analyzed by numerical taxonomic techniques. On the basis of community structure, the river was clearly separated into two regions. The seven sites along the first 18 km formed a cluster, and those of the remaining stretch formed a second cluster, which was more similar to Broadwater, a large shallow pond that discharges into the river between Godalming and Guildford (approx. 34.2 km below the source). Two methods are compared for reducing the counts obtained for each sample to a single index.     

西江颗粒直链藻种群生态特征

西江肇庆段是珠江干流汇入珠三角河网水域的咽喉通道,结合长期定点连续采样和空间季节性调查,重点对2009年西江干流肇庆段的颗粒直链藻(Aulacoseira granulata)的种群生态学特征进行系统分析。结果显示:全年中,颗粒直链藻在总种群中所占百分比均值为25.37%,与总种群丰度存在极显著正相关关系,这表明颗粒直链藻是西江浮游植物群落的重要优势种。调查期间发现了颗粒直链藻的4种形态,包括原变种(var.granulata)、极狭变种(var.angustissima)、弯曲变种(var.curvata)和极狭变种螺旋变型(var.angustissima f.spiralis)。其中,原变种占有绝对优势地位,其相对百分组成的年均值为91.47%,推测为原变种的形态结构比其它3种形态更容易适应外界环境变化,进而形成优势群体。颗粒直链藻总密度的周年变化呈现明显的双峰型,两个峰值分别出现在8月和11月,主要得益于适宜的水温、相对稳定的水体和较高的营养盐水平,这些均有助于颗粒直链藻的生长繁殖。第一个高峰之前,颗粒直链藻总密度未出现明显的波动,这很可能是由于水体径流量增大导致的稀释作用和频繁降雨导致的水体剧烈波动对颗粒直链藻增长的负作用掩盖了水温上升所带来的益处。从空间分布来看,颗粒直链藻总丰度的最大值一般出现在S1、S5和S6站点,这与营养盐最大值的空间分布格局是一致的。     

Benthic diatom assemblages and their response to human stress in small-sized volcanic-siliceous streams of central Italy (Mediterranean eco-region)

The river typology ‘volcanic rivers’ represents a unique typology in the Mediterranean eco-region in Europe but its type-specific diatom assemblages are still poorly investigated. The main aims of this study were (i) to analyse the diatom diversity of this river type, (ii) to investigate the relationships between diatom diversity and environmental variables and (iii) to identify the characterizing diatom community structure of different environmental groups. To this end, we selected 13 streams located in central Italy, belonging to a single river type and covering the whole quality range from human impacted sites to those in ‘reference conditions’. Most frequent and abundant diatom species found were Cocconeis placentula var. lineata, Planothidium lanceolatum, Rhoicosphenia abbreviata and Amphora pediculus. Species richness in reference and less impacted sites was not higher than in intermediate and heavily degraded ones, but non-metric multidimensional scaling (N-MDS) analysis revealed a substantial difference among their diatom community structure. The indicator species analysis defined the characteristic species of three environmental groups identified by N-MDS. The findings of this study represent a contribution to the knowledge on diatom communities of Mediterranean volcanic-siliceous rivers and provide information for a data-driven implementation of the Water Framework Directive in Italy for this specific river typology.     

Downstream changes in phytoplankton composition and biomass in a lowland river–lake system (Warnow River, Germany)

To determine longitudinal changes in phytoplankton composition and biomass in the Warnow River (Germany), single water parcels were followed during their downstream transport in August and October 1996 and April 1997. In summer, the phytoplankton assemblage was dominated by centric diatom and cyanobacteria species. Stephanodiscus hantzschii, Pseudanabaena limnetica, Planktothrix agardhii and Aulacoseira granulata var. angustissima were the most frequent species. In autumn, small centric diatoms dominated the whole river course. Irrespective of the season, in the fluvial lakes of the upper river, a substantial increase of phytoplankton biomass was observed. Shallow upstream river stretches were associated with large biomass losses. In the deep, slow flowing lower regions, total biomass remained constant. Longitudinal changes in biomass reflected downstream variations in flow velocity and river morphology. Cyanobacteria, cryptophytes and diatom species were subjected to large biomass losses along fast flowing, shallow river sections, whereas chlorophytes were favoured. Diatoms and cryptophytes benefited from low flow velocity and increased water depth in the downstream river. Changes in water depth and flow velocity have been found as key factors that cause the longitudinal differences in phytoplankton composition and biomass in small rivers.     

Downstream variations of phytoplankton in the St.Lawrence River (Québec, Canada)

Longitudinal variations of phytoplankton biomass and composition were assessed in a 250 km-long section of the St.Lawrence River, which alternately runs through narrow (< 2 km) river cross sections and wide (up to 10 km) fluvial lakes. In the main river stem, concentrations of suspended matter and total phosphorus increased with distance downstream, whereas light penetration decreased. Seasonal changes in plankton composition and biomass were more important than those resulting from differences in water mass (tributary) of origin. Sampling at three cross river sections and in two fluvial lakes showed a progressive downstream decrease in phytoplankton biomass and changes in size structure and taxonomic composition. River plankton was primarily composed of small (< 10 µm equivalent spherical diameter), truly planktonic cells belonging to Cryptophyceae and diatoms, with Chlorophyceae in summer. Plankton sampled in summer among rooted macrophytes in fluvial lakes exhibited a higher biomass of resuspended periphytic algae than in the main river stem, which contributed slightly to downstream phytoplankton biomass.Successive river cross sections always shared about 50% of their taxa, indicating a rapid downstream transport of algae within the main water mass. However, the proportion of species common to all cross sections was highest during the spring freshet, and lowest during summer low discharge, likely resulting from the development of a distinct flora in fluvial lakes during summer. Conversely, about 30% of the identified taxa were exclusive to a cross section and were replaced by others occurring downstream. Overall, phytoplankton composition along the St.Lawrence River is primarily controlled by advective forces, which result in a homogeneous flora in the main river stem, with a local contribution of resuspended periphyton from fluvial lakes.     

Effects of water quality and season on diatom community structure in the Damour River,Lebanon

The diatom flora in the lower Damour River, a small coastal river in Lebanon, was studied during 1981. The study area included the Damour estuary and a tributary, the el-Hamam River. Achnanthes minutissima was the most abundant diatom in the flora. Other dominant taxa included Nitzschia dissipata and Navicula cryptocephala var. veneta in the spring and Anomoeoneis vitrea in the fall. The diatom community structure was characterized by 1 or 2 dominant taxa, a few common and many rare taxa, but the taxa in these categories varied according to season and locality. The freshwater flora had a group of 20 taxa which were widely distributed in the study area throughout the study period. These taxa, in addition to a few taxa of more restricted seasonal occurrence, were the major contributers to the flora and are characteristic of this river system. Certain aspects of the flora were resistant to change. Others were more sensitive to environmental conditions. The estuarine flora reflected brackish conditions beginning in June and extending through October.     

Diatom assemblages of the Cuyahoga river,N. E. Ohio (USA)

The Cuyahoga River is a heavily polluted tributary of Lake Erie located in N. E. Ohio (USA).One hundred seventy taxa of diatoms were identified from seven locations along the Cuyahoga River. The most frequently collected diatoms from each station were Cyclotella meneghiniana, Gomphonema parvulum, Navicula cryptocephala, N. cryptocephala var. veneta, N. lanceolata, N. menisculus, N. minima, N. minuscula, N. pelliculosa, Nitzschia amphibia, N. ovalis, N. palea, and Rhoicosphenia curvata.In the most heavily damaged region of the river these widely-distributed taxa were the only frequently collected diatoms.The relatively undamaged section of the river contained 94% more taxa than the most heavily damaged section. Chief among these additional taxa were Achnanthes lanceolata, A. lanceolata var. dubia, Cocconeisplacentula, Fragilaria vaucheriae, Melosira varians, Meridion circulare, Navicula mutica var. tropica, N. symetrica, Nitzschia dissipata, Stephanodiscus astraea, and Synedra rumpens.The degree of similarity between diatom assemblages along the Cuyahoga River as measured by a modification of Sørensen's index of similarity in species-frequency of occurrence composition was related to the degree of chemical-physical water quality similarities and to the extent of similarity between areas of geologic and biologic substrates. The most dissimilar diatom assemblages usually occurred between locations that were the most dissimilar with respect to chemical-physical water quality conditions rather than to dissimilarities with respect to sediment-substrate composition.     

Tributary and mainstem benthic macroinvertebrate communities linked by direct dispersal and indirect habitat alteration

Benthic communities in tributary–mainstem networks might interact via downstream drift of invertebrates or material from tributaries and adult dispersal from the mainstem. Depending on the strength of these interactions, mainstem downstream communities are expected to be more similar to tributary communities due to drift or habitat alteration. Communities not connected by flow are expected to be similar due to adult dispersal but decreasing in similarity with distance from the mainstem. We investigated interactions between invertebrate communities of a 7th order river and 5th order tributary by comparing benthic community structure in the river upstream and downstream of the tributary confluence and upstream in the tributary. Non-metric multidimensional scaling showed invertebrate communities and habitat traits from river locations directly downstream of the tributary clustered tightly, intermediate between tributary and mid-channel river locations. In addition, Bray–Curtis dissimilarity increased between the mainstem and tributary with distance upstream in the tributary. Our results indicate that similarities between mainstem and tributary communities are potentially caused by direct mass effects from tributary to downstream mainstem communities by invertebrate drift and indirect mass effects by habitat restructuring via material delivery from the tributary, as well as potential effects of adult dispersal from the river on proximal tributary communities.     

Ichthyoplankton transport in relation to floodplain width and inundation and tributary creek discharge in the lower Savannah River of Georgia and South Carolina

We report the results of a 3-year study of ichthyoplankton in the lower Savannah River and its coastal plain tributaries. Sampling was weekly from February through July in 1983, 1984 and 1985. Ichthyoplankton transport was used as an estimate of ichthyoplankton production. Ichthyoplankton transport in the river, for both total and most common taxa, was highest in 1983 and lowest in 1985. Ichthyoplankton transport into the river from tributary streams was also highest in 1983 and lowest in 1985. Ichthyoplankton transported from these tributaries sometimes comprised a significant percent of the larval transport at the next river station downstream from the tributary mouth. The highest larval transport occurred when the spring flood pulse was most elevated for the longest time, and larval transport at particular river stations or creeks was correlated with floodplain width in 1983 and 1984, years when flood pulses were high enough so that the adjacent floodplain was inundated during or following spawning. In 1985 the flood pulse was brief, inundation levels were low, and inundation occurred in February before most fish had spawned. Except for American shad and sunfishes, larval transport for all common taxa was greatly reduced in 1985 compared to 1983.     

Diatom Flora of the Grand River,Ontario, Canada

Summary This paper describes the diatom flora of the Grand River, Ontario, Canada. Samples were collected systematically from the river over a period of several years at tweleve stations. The diatom flora of the river is typical of temperate alkaline rivers. The flora is rich in species and variaties, and is similar to that from many parts from North Eastern United States. A total of 273 taxa of diatoms were identified. There is a tendency for the number of species per sample to increase downstream. The flora of the estuary in characteristic with a great variety of taxa occuring in small numbers. Most of the species are alkaliphilous and indifferent in the halolian spectra. Part of Ph. D. thesis (1970) of senior author     

Benthic diatoms of the Vistula River estuary (Northern Poland): Seasonality,substrata preferences,and the influence of water chemistry

Seasonal studies of water bodies in separate branches of the Vistula River estuary in Northern Poland were conducted over 30 months from May 2005 to October 2007. Diatom samples were collected from different substrata from two sites located in the river mouth, which has physical characteristics as a result of a complex interplay of natural and human influences that have taken place over the last 100+ years. The diatom flora growing on hard surfaces near the river banks such as sand, muddy sand, rocks, macroscopic green algae and/or vascular aquatic plants was recorded. All diatom taxa collected were distinguished based on their morphological features using light (LM) and scanning electron microscopy (SEM). A total of 187 species belonging to 61 genera were identified. A canonical correspondence analysis indicated that the diatom assemblages were definitely associated with salinity as well as nutrient concentrations and substratum type. During the study, malformations of diatom valves were observed in 48% of the microphytobenthos samples. Abnormal outline morphology and ornamentation deformities in several individuals of nine different species were recorded, which were mainly in epilithic and epiphytic communities collected from spring to autumn.     

Distribution patterns of diatom surface sediment assemblages in the Laptev Sea (Arctic Ocean)

The modern diatom distribution in the Laptev Sea, Arctic Ocean, was investigated in 89 surface sediment samples. Diatom concentrations are relatively low showing values between 0.01×10⁶ and 6.7×10⁶ valves per gram dry sediment. Based on a factor analysis using seventeen taxa or taxa groups five diatom surface sediment assemblages can be defined: the ice diatom assemblage of the central region of the Laptev Sea, the Chaetoceros assemblage of the eastern and southeastern shelf, the Thalassiosira antarctica assemblage of the continental slope and deep sea, the freshwater diatom assemblage in the vicinity of river mouths and deltas, and the Thalassiosira nordenskioeldii assemblage which shows a patchy occurrence on the central Laptev Sea shelf. The distribution pattern of diatom assemblages in surface sediment is significantly related to oceanographic conditions of surface water masses. The main factors controlling the distribution of diatoms in the Laptev Sea are the riverine freshwater input during the summer which strongly affects the salinity conditions, and the sea-ice extent. Furthermore, the composition of the Thalassiosira antarctica assemblage of the continental slope is largely influenced by dissolution and lateral transport processes.     

Distribution of chromobacteria in a lowland river

A selective medium was used to estimate the numbers of purple pigmented bacteria in the River Wey. Chromobacteria were never isolated from the springs at the source of the river, but they appeared within a short distance and their numbers generally increased over the first 30 km. Counts were always low but were much higher during the winter than during the summer.Records of water temperature and turbidity, as well as daily rainfall, were maintained during the sampling period. An unweighted multiple regression analysis of some of the results has shown that much of the variability in the counts of chromobacteria was correlated with turbidity (r=0.67,P<0.001). After turbidity was allowed for, a significant inverse correlation with temperature (r=0.60,P < 0.001) became apparent and these two factors together accounted for 64.7% of the variation in counts. Allowing for these two factors revealed a significant correlation with rainfall during the previous 4 days (r=0.27,P<0.05), and the three factors together accounted for 67.2% of the variability in counts.In an attempt to discover the source of chromobacteria, samples of silt, soil, and storm overflow effluents were studied. In general, chromobacteria were present in highest numbers in soil or silt containing substantial quantities of organic material.     

The influence of floodplain habitat on the quantity and quality of riverine phytoplankton carbon produced during the flood season in San Francisco Estuary

Primary productivity, community respiration, chlorophyll a concentration, phytoplankton species composition, and environmental factors were compared in the Yolo Bypass floodplain and adjacent Sacramento River in order to determine if passage of Sacramento River through floodplain habitat enhanced the quantity and quality of phytoplankton carbon available to the aquatic food web and how primary productivity and phytoplankton species composition in these habitats were affected by environmental conditions during the flood season. Greater net primary productivity of Sacramento River water in the floodplain than the main river channel was associated with more frequent autotrophy and a higher P:R ratio, chlorophyll a concentration, and phytoplankton growth efficiency (α^B). Total irradiance and water temperature in the euphotic zone were positively correlated with net primary productivity in winter and early spring but negatively correlated with net primary productivity in the late spring and early summer in the floodplain. In contrast, net primary productivity was correlated with chlorophyll a concentration and streamflow in the Sacramento River. The flood pulse cycle was important for floodplain production because it facilitated the accumulation of chlorophyll a and wide diameter diatom and green algal cells during the drain phase. High chlorophyll a concentration and diatom and green algal biomass enabled the floodplain to export 14–37% of the combined floodplain plus river load of total, diatom and green algal biomass and wide diameter cells to the estuary downstream, even though it had only 3% of the river streamflow. The study suggested the quantity and quality of riverine phytoplankton biomass available to the aquatic food web could be enhanced by passing river water through a floodplain during the flood season.     

Characterization of the diatom flora in the Lower Mountain Fork (Oklahoma,USA), a novel regulated river with a disjunct population of the diatom Didymosphenia geminata (Bacillariophyta)

Regulated rivers are novel ecosystems with altered temperature and flow regimes that can be used to test distribution patterns of microscopic organisms, such as diatoms. Our objective was to describe the spatial and seasonal patterns of diatoms in a cold-water, oligotrophic river within a region of warm-water, mesotrophic rivers. The Lower Mountain Fork, in south-east Oklahoma (USA), is maintained as a year-around, stocked fishery by the release of cold, hypolimnetic water from Broken Bow Lake and is the southern-most known site of Didymosphenia geminata in North America. Epilithic diatoms were sampled six times at nine sites over a distance of 15.5 km and, within this area, 27 times at the site of the main Didymosphenia bloom. Percentage composition data were analysed for assemblage composition using multivariate analysis, nutrient specificity using a diatom-based metric, and species associations using similarity profiles. Eighty-eight taxa were found, of which 10 were unidentifiable and included local undescribed species and species clusters. Three species [Gomphonema (parvulum morph), Achnanthidium rivulare and Achnanthidium minutissimum] comprised over 60% of the diatom abundance at all sites, and downstream and seasonal patterns were evident for both these and less abundant taxa. Notably, diatom assemblages in the three sites below the dam were similar to that at the lowermost site, below a much smaller dam. The oligotraphentic diatom assemblage reflected the water chemistry of the river. The Didymosphenia bloom had been scoured by a large spate prior to the study and the species was present at two of the nine sites in low numbers but failed to bloom during the study, possibly because of a trend towards increasing phosphorus concentrations in the reservoir (Didymosphenia blooms under low P concentrations). No other species shared Didymosphenia’s distribution pattern over the study reach, highlighting the novelty of Didymosphenia’s presence in the river.     

Palaeolimnological evidence for the independent evolution of neighbouring terminal lakes,the Murray Darling Basin,Australia

Phytoplankton composition and production are highly unpredictable within an estuary, due to the high variability of forcing factors, such as freshwater flow, salinity, nutrients and light. The Guadiana estuary has shown sharp inter-annual differences in freshwater flow, related to variable precipitation, which is expected to affect nutrient loadings, light availability and phytoplankton succession. Water retention due to dam construction will further enhance changes in river flow and ecosystem dynamics. The main goal of the present study was to describe and relate phytoplankton succession and environmental conditions, namely nutrients and light, in the Guadiana upper estuary (south-western Iberian Peninsula), a dam regulated temperate estuary. From March 2004 to October 2005, water samples were collected in three stations along a longitudinal transect covering the upper estuary. Several water variables were determined and phytoplankton composition was studied through inverted and epifluorescence microscopy. A typical freshwater phytoplankton succession was observed, from a diatom spring bloom to cyanobacteria dominance in the summer, and a second diatom bloom in the autumn. Neither nutrients nor light availability seemed to be related to the observed succession, especially the seasonal variation of diatom abundance. During summer, nutrient concentrations (especially Si) were high and non-limiting, whilst light was available in the mixing layer. However, diatoms were present in low numbers. Grazing pressure was probably responsible for the regulation of diatom seasonal succession in the Guadiana upper estuary, which should be addressed in future studies. Handling editor: K. Martens     

The effects of coal industry pollutants on the macroinvertebrate fauna of a small river in the South Wales coalfield

SUMMARY. The effects of pollutants from the coal industry on the macroinvertebrate fauna of a small river in the South Wales coalfield were investigated during 1972 and 1973.
Three major types of pollution, each spatially separate, affected the river and its tributaries. The upper reaches received acidic drainage from coal stockpiles. The lower reaches received a discharge from a drift mine, bearing high loads of suspended coal particles which caused siltation of the river bed downstream to its confluence with the R. Taff (3.5 km). The largest tributary was subjected, under neutral pH, to siltation by ferric hydroxide, derived from seepage from an abandoned mine.
In the upper reaches, a few acid-tolerant invertebrate species survived in low numbers. Downstream recovery was not complete before the discharge of coal particles. In the reaches silted by ferric hydroxide or coal there was a pronounced reduction (80–90%) in faunal abundance. Clear differences in sensitivity of invertebrate groups to these types of siltation were apparent.
The data are used to assess the various methods of biological surveillance involving invertebrates.     

Short-term fluctuations in benthic diatom numbers on an intertidal sandflat in the Westerschelde estuary (Zeeland,The Netherlands)

During the period March–May 1991, sediment samples were taken every two or three days at one intertidal station in the brackish part of the Westerschelde estuary. Quantitative cell counts were made in order to investigate the short-term temporal changes in diatom numbers and assemblage structure.Throughout the whole sampling period, the diatom assemblage was dominated by epipsammic diatoms. Three species, Achnanthes delicatula, Opephora cf. perminuta and Catenula adhaerens on average accounted for almost 67% of all valves counted. The epipsammic diatom fraction showed no significant changes in absolute numbers; its species composition appeared relatively stable. In contrast, epipelic diatom densities significantly increased towards the end of the study period. Species composition within this fraction was less stable. Multivariate analysis (Principal Components Analysis), in combination with multiple regression, indicated that total sky irradiance (on the second and third day preceding sampling) and percentage organic matter were related to the short-term fluctuations of the epipelic diatom fraction.     

Comparative monitoring of diatoms, macroinvertebrates and macrophytes in the Woluwe River (Brussels, Belgium)

The river Woluwe in Brussels and Flanders (Belgium) is a small tributary of 15 km length that drains an area of 9400 ha in the Schelde river basin. The headwaters of the Woluwe are highly fragmented by diverse pond systems and are vaulted in the Brussels agglomeration. Hyporheic zones locally influence the water quality. The downstream stretch of the river receives sewage waters from households and industry. As the river Woluwe within a short distance represents a typical gradient from groundwater-fed sources in the forest towards severely polluted water, a comparative monitoring using diatoms, macroinvertebrates and macrophytes was done. The saprobic index based on diatoms, the Belgian Biotic Index (BBI) for macroinvertebrates and a macrophyte index based on the N-values of Ellenberg were used in this comparison and for estimating the correlation with the bimonthly measured chemical variables in 16 sampling stations. The diatom saprobic index and the macrophyte index were strongly correlated. Both groups showed strong correlations with phosphate, ammonium and chemical oxygen demand. The Belgian Biotic Index showed lower correlations with the nutrient variables, but was slightly better correlated to chemical oxygen demand, chloride and dissolved oxygen. None of the indices showed a correlation with nitrate. Local substrate or light conditions could interfere with the indicator system, especially for the macrophytes and occasionally for the macroinvertebrates. It was concluded that at least in this particular river system, the indices based on the primary producers were more indicative for the trophic status, whereas the BBI showed a broader relationship to the general degree of pollution. Therefore, these three indices are considered as complementary for monitoring the biological quality and the ecological status of a river system.