Journal of the North American Benthological Society

Published by Society for Freshwater Science
Online ISSN: 1937-237X
Environmental variables measured at each site.
Mean (1 SE) values for each invertebrate community group (IC) of the 12 most significant (p 0.0001) environmental variables distinguishing the groups identified with a Kruskal-Wallis test. IC6 and IC7 were excluded from the ANOVA because they only contained a single site. The significance threshold was set at 0.001 ( 0.05/44 comparisons) after applying a Bonferroni correction to compensate for multiple compar- isons. DO dissolved oxygen.
Relationships between (A) rainfall and family richness, and (B) conductivity and family richness for the major invertebrate community groups (IC) identified by cluster analysis. Values are means 1 SE. Error bars for low SEs are sometimes obscured by symbols.
Ranges of 8 selected water chemistry variables for the 30 most common aquatic macroinvertebrate families collected in southwestern Australia during spring 1997. Limits of detection for color, total N and total P were 5 TCU, 0.02 mg/L, and 0.01 mg/L, respectively. DO dissolved oxygen.
The agricultural zone of southwestern Australia is an extensively modified landscape. Ninety percent of the perennial native vegetation has been cleared and replaced by annual cereal crops and pasture. Consequently, groundwater has risen and much of the region is affected by dryland salinity. River geomorphology and water quality have been severely impacted by land clearing, anthropogenic patterns of land use, and secondary salinization. The objectives of this study were to determine patterns of distribution of aquatic macroinvertebrates in the region, and to identify environmental variables influencing these patterns. Aquatic macroinvertebrates were sampled at 176 river sites during spring 1997 and a range of environmental data were collected at each site. Eighty-one families were collected, with the fauna being dominated by insects. At the family level, macroinvertebrate communities were homogeneous and depauperate, and consisted of families that tolerated a broad range of environmental conditions. The fauna was particularly resilient to high salinities, with some families tolerating salinities orders of magnitude greater than previously reported for lotic waters. The most significant environmental factors influencing the distribution of aquatic invertebrates were rainfall, salinity, land use, and instream habitat.
Periphyton is a key component of shallow littoral zones of lakes and streams because it is an important source of primary production and a food resource for herbivores. Meiofauna are abundant in periphyton, but macroinvertebrate grazer (macrograzers) effects on periphytic meiofauna have not been studied so far. We used a spatially structured field experiment (hierarchical nested design consisting of 3 subsites at each of 3 sites) in Lake Erken (Sweden) to investigate the effect of macrograzers on epilithic meiofauna and algae in periphyton by controlling macrograzer access to littoral periphyton communities. Overall, we found a strong negative effect of macrograzer presence on algal biomass and some evidence for negative macrograzer effects on meiofaunal abundance and community composition. The impact of macrograzers on both algae and meiofauna were highly variable between sites and subsites. The largest spatial differences were for macrograzer effects on meiofaunal abundance and composition. We also investigated the ability of macrograzers to reduce spatial heterogeneity of periphyton biomass, but the presence of macrograzers did not alter the variation in algal biomass and associated meiofauna among replicates. We conclude that strong local variability in algal biomass and meiofauna abundance exists between neighboring sites even in the presence of strong overall macrograzer effects. This local variability could be based on factors known to cause spatial heterogeneity, such as hydrodynamics, nutrients, substrate characteristics (size, texture, exposure), or biotic interactions.
Lake Carpentaria, Australia. The dark lines represent current coastline and rivers, and the dotted lines represent the 2120-m sea level contour with projected river channels (adapted from Voris 2000).
Microsatellite loci developed and used in our study.
Study area with sites and mitochondrial deoxyribonucleic acid (mtDNA) variation. Sites include codes (with prefix indicating catchment) and total sample sizes in brackets. Site codes are Kingfisher Camp (KFC), Adel's Grove (AG), Gregory Downs 1 (GD1), Floraville Station (FL), Augustus Downs Station (AS), Nardoo Station (NA), Lake Moondarra (MO), East Leichhardt Dam (LD), and Iffley Station (IF). The mtDNA network (inset to the upper right) is based on a 396-base pair fragment of the control region. Each haplotype is shaded to correspond with sites where it was sampled. The number of individuals sequenced from each site is found within each circle representing the site.
Results from Analysis of Molecular Variance. Fixation indices that significantly deviate from 0 are marked. KFC = Kingfisher Camp site on the Nicholson River. * = p , 0.05, ** = p , 0.01.
The genetic structure of the freshwater fish Ambassis macleayi Castelnau 1878 was explored across the tropical catchments of the Gulf of Carpentaria Basin, northern Australia. The Gulf of Carpentaria provides a unique opportunity to explore simultaneously contemporary and historical gene flow resulting from unique climatic patterns and historical connectivity among catchments via a freshwater lake that existed during lower sea levels. The control region of the mtDNA genome and 4 microsatellite loci were used to detect significant genetic structure among and within catchments. Within catchments, genetic structure suggested that dispersal of A. macleayi is restricted, despite high levels of connectivity during summer monsoonal events. Among catchments, divergence appeared to be deeper than what would be predicted based on the last opportunity for connectivity via the lake of Carpentaria (10,000 years before present [ybp]). Overall, these results have important implications for A. macleayi and other members of this genus. If individuals are not proficient dispersers, recolonization after disturbance will be limited. Because of historical isolation among catchments, each catchment harbors unique genetic diversity that should be conserved independently. Yes Yes
Photographer and writer Tim Palmer has spent more than 25 years researching and experiencing life on the waterways of the American continent. He has travelled by canoe or raft on more than 300 different rivers, down wide placid streams and rough raging rapids. His journeys have taken him to every corner of the country, where he has witnessed and described the unique interaction of geographical, historical, and cultural forces that act upon our nation's vital arteries.America by Rivers represents the culmination of that grand adventure. Palmer describes the rivers of America in all their remaining glory and tarnished beauty, as he presents a comprehensive tour of the whole of America's river systems. Filled with important new information as well as data gathered from hundreds of published sources, America by Rivers covers: the network of American waterways and how they fit together to form river systems unique features of individual rivers along with their size, length, and biological importance environmental problems affecting the rivers of different regions and what is being done to protect and restore them cultural connections and conflicts surrounding the rivers of each region Chapters address the character of rivers in distinct regions of the country, and each chapter highlights one river with a detailed view from the water. Rivers profiled include the Penobscot, Potomac, Suwanee, Minnesota, Niobara, Salmon, Rio Grande, American, Rogue, and Sheenjek. Eighteen maps guide the reader across the country and 100 photos illustrate the splendor of Palmer's fascinating subject.America by Rivers provides a new way of seeing our country, one that embraces the entire landscape and offers fresh avenues to adventure. It is compelling reading for anyone concerned about the health of our land and the future of our waterways.
The National Wild and Scenic Rivers Act is one of the most important natural areas protection programs ever established at the federal level. It has resulted in the creation of the National Wild and Scenic Rivers System -- a rich American legacy that includes many of our finest waterways. This book is the definitive resource on the National Wild and Scenic Rivers System. Topics covered include: the importance of protecting river ecosystems state and local protection systems the history of the National Wild and Scenic Rivers System descriptions of each of the major rivers in the system how and why rivers are chosen for inclusion river management continuing threats to rivers what can be done to make the system more effective and more inclusive
Entering the Watershed is the product of a two-year project established by the Pacific Rivers Council to develop new federal riverine protection and restoration policy alternatives. It recommends a comprehensive new approach to river protection based on principles of watershed dynamics, ecosystem function, and conservation biology -- a nationwide, strategic community- and ecosystem-based watershed restoration initiative. The book: describes in detail the existing level of damage to rivers and species analyzes flaws and gaps in existing policy provides the framework necessary to develop new policies outlines the scientific underpinnings and management strategies needed in new policy makes specific policy proposals
Diagram of the arena used in the 2-chamber habitat-choice experiment. The passage between the chambers was closed with a removable dividing wall during the set-up phase of each trial. A tile was placed into a notch in each chamber. Fifteen mussels shells (MS) were glued to the surface of the reference tile in 1 chamber. One of 5 habitat treatments (MS, bare tile, living mussels, MS plus biodeposited material, or MS plus biodeposited material and chironomids) was presented on the surface of the tile in the 2 nd chamber.  
Mean (61 SE) difference in the number of individuals (ind.) of Gammarus roeselii (A) and Dikerogammarus villosus (B) in 2 arms of a y-maze experiment testing responses to lake water conditioned with zebra mussels, i.e., containing kairomones, and unconditioned water. Values are the difference in the number of individuals between the arms of the y-maze, averaged at 10-min intervals from 10 to 30 min after initiating the experiment. Positive values indicate preference for the conditioned water; negative values indicate avoidance of the conditioned water. ** p , 0.01, *** p , 0.001.  
In the last decades, zebra mussels (Dreissena polymorpha) have invaded many freshwater systems with severe consequences for entire communities. Most benthic macroinvertebrates, especially amphipods and chironomids, increase in abundance in the presence of zebra mussels. Increased structural complexity and an unknown biotic factor lead to this effect. Dreissena-associated factors that might influence populations of the native Gammarus roeselii and the invader Dikerogammarus villosus in Lake Constance, Central Europe, were investigated in laboratory experiments. These factors were: 1) increased structural complexity related to mussel shells, 2) Dreissena biodeposition, 3) chironomids, the presence of which is increased by biodeposited matter, and 4) Dreissena kairomones. In habitat-choice experiments, the native and omnivorous amphipod G. roeselii showed a preference for mussel shells with biodeposited material and for mussel shells with biodeposited material with chironomids, whereas the invasive and predatory amphipod D. villosus showed a preference only for mussel shells with biodeposited material with chironomids. In a kairomone y-maze experiment, both amphipods avoided zebra-mussel-conditioned lake water. These results indicate that habitat complexity and food availability, mediated directly or indirectly through biodeposited material, are the factors by which amphipod abundances are increased in the presence of Dreissena. Thus, biodeposited material can form an important new food resource, translocated from the pelagic zone to the benthos by zebra mussel filtration, and this biodeposited material might support a new detritus-based food web in the benthos.
The invasive North American amphipod Gammarus tigrinus is successfully established in Lough Neagh, Northern Ireland. Gammarus tigrinus is increasingly recognized as having significant predatory impacts on macroinverebrates, contrary to the accepted functional feeding group status of Gammarus species. The native opossum shrimp Mysis relicta overlaps in habitat use with G. tigrinus. However, its interaction with benthic macroinvertebrates is rarely appreciated. Mutual predatory interactions between G. tigrinus and M. relicta were assessed in a series of laboratory experiments. Gammarus tigrinus actively preyed on adult and juvenile M. relicta at a range of spatial scales. Females and recently molted M. relicta were particularly vulnerable to predation. Mysis relicta did not prey on adult G. tigrinus, but rapidly eliminated juvenile G. tigrinus in microcosms. Changes in dissolved O2 saturation did not alter the predatory interaction between these species. Microhabitat use by M. relicta was altered in the presence of G. tigrinus, and the presence of G. tigrinus facilitated fish predation on M. relicta. A balance of mutual predatory pressure between these invasive and native species may explain their coexistence. Both species are likely to be strongly interactive with other macroinvertebrates in both native and invasive ranges.
Substrate interstices influence the microdistribution and survival of benthic invertebrates. The benefits of interstitial refugium availability were quantified over 4 wk under baseflow conditions that are common to lowland streams in northwestern Europe. Effects on growth, feeding, and behavior of the amphipod Gammarus pulex L. were studied in 8 indoor artificial stream channels. Combinations of 2 near-bed flow velocities (3 and 9 cm/s) and 2 substrate types (medium sand and coarse gravel) were assigned to 32 experimental compartments. Growth of G. pulex was greater at 9 cm/s than at 3 cm/s, and G. pulex avoided bare sand and used gravel patches at both flow velocities. Food consumption was lower and individual growth was greater in gravel than in sand, a result that suggests that energetic costs were lower in gravel than in sand. We suggest that the interstitial refugia in gravel may have benefits beyond providing protection from flow. The presence of interstitial refugia may be of key importance to G. pulex, and the underlying mechanism of interstitial refugium use might be associated with the adaptation of organisms to seek refuge from predators
Sampling locations for atyid shrimp in the Caribbean combined data set consisting of mitochondrial gene sequences for the 16S fragment of ribosomal DNA (16S) and cytochrome oxidase I (COI).  
Sampling locations of Atya-like shrimp from the Indo-Pacific and Caribbean-Atlantic included in the Worldwide data set consisting of mitochondrial gene sequences for the 16S fragment of ribosomal DNA (16S). The dashed rectangle shows the sampling area in Fig. 1. Is. ¼ island, Fr. ¼ French.  
Maximum likelihood (ML) phylogram for atyid shrimp in the Caribbean combined data set consisting of mitochondrial gene sequences for the 16S fragment of ribosomal DNA (16S) and cytochrome oxidase I (COI). The phylogram shows specimen geographic origin. ML bootstrap values are shown above nodes, with Bayesian posterior probabilities below nodes. Nodes with ,60% for both values have been collapsed. Shrimp are shown in correct relative sizes (drawings adapted from Fryer 1977).  
Details for primers used to sequence mitochondrial genes 16S ribosomal DNA (16S) and cytochrome oxidase I (COI). 
The evolutionary relationships of the surface genera of shrimps of the family Atyidae from the Caribbean were inferred using mitochondrial 16S ribosomal DNA and cytochrome oxidase I gene sequences. The genetic divergence among the 4 Caribbean genera (Atya, Jonga, Micratya, Potimirim) is extensive and dates from between the Eocene and Miocene. This result suggests a vicariant origin or the ancient dispersal of some taxa. Most intrageneric divergences date to the late Miocene–Pliocene and, thus, are probably the result of dispersal. Some species show low levels of intraspecific genetic divergence between distant islands, and thus, present-day or geologically recent gene flow is likely. This gene flow is probably a consequence of the amphidromous life histories of most Caribbean freshwater shrimps. Despite the ancient divergences between the genera, the Caribbean surface atyids form a single evolutionary lineage when compared with atyid shrimp from throughout the world, and this result implies an ancient evolutionary radiation in the Caribbean. The sister group to the Caribbean atyids are the large-bodied and robust Atya-like shrimps of the Indo-Pacific, which share a similar size and shape with Caribbean Atya. Thus, the common ancestor probably was also large and robust. In contrast, the other Caribbean atyids are much smaller, and Jonga has a distinct morphology that is associated with a switch from lotic to lentic environments. This radiation may have been the result of the absence from the Caribbean of other small shrimps that are common in the Indo-Pacific. Yes Yes
A.-Location of the study site within The Netherlands. B.-Study site in more detail; black hairlines represent drainage ditches, gray areas indicate larger water bodies. C.-Sampling grid of activity traps established at the study site. The grid consisted of 4 ditches, each containing 9 activity traps, with an intertrap spacing of 0.5 m and a between-ditch spacing of ,50 m.
Log 10 (x)-transformed mean (61 SE) total number of taxa/trap (A) and total number of individuals/trap (B) for attractant treatments and trapping durations. Bars with the same letters are not significantly different.  
Sample-based (A) and individual-based (B) taxon accumulation curves with 95% confidence intervals (CI) of activity trap catches for different trapping durations: t = 48, 96, or 168 h. Sample order was randomized 50 times to obtain means.  
Mean (61 SE) number of predator (P) and detritiherbivore (DH) taxa/trap for trapping durations: t = 48 (A), 96 (B), or 168 h (C). Bars with different letters are significantly (p , 0.05) different. Within groups, bars without letters are not different.  
Mean (61 SE) number of taxa/trap for predators (P) and detritiherbivores (DH) with different modes of locomotion (swimmers [S], nonswimmers [N]) for attractants: control (A), bait (B), or leaves (C). Bars with different letters are significantly (p , 0.05) different. Within groups, bars without letters are not different.
I investigated the effectiveness of activity traps for macroinvertebrate monitoring in shallow, heavily vegetated drainage ditches and explored 2 ways to optimize the use of activity traps for monitoring purposes. I tested the effects of trapping duration (48, 96, and 168 h) and use of attractants (bait and preconditioned leaves). The number of taxa and individuals captured increased with trapping duration. Based on the taxon accumulation curves, deployment times of 48 h and 96 h were equally efficient in capturing new taxa, but a trapping duration of 168 h was much more efficient and resulted in a larger number of taxa collected with every new sample added. Of the attractants offered in the traps, only bait caused differences in the macroinvertebrate assemblage recorded. After 48 h, more predators were captured in traps with bait than in control traps and traps with preconditioned leaves. This effect disappeared with longer trapping duration. Because of their relatively low labor requirements and high level of standardization, activity traps appear to be a valuable tool in lentic biodiversity surveys, especially when deployed for a longer period than has usually been reported. The use of bait is advisable only if capture of specific taxa is required and not for standard monitoring purposes.
Branch Creek West study site within the Conondale Range, southeast Queensland, Australia. Sites are numbered from the home pool (BW0), where the initial translocation took place, upstream to the Branch West plus-five pool (BW+5) and downstream to the Branch Creek minus-five pool (BW25). 
When 2 populations are mixed for whatever reason, the outcome can be difficult to predict. In 1993, 2 populations of an atyid shrimp (Paratya australiensis:Atyidae) from different subcatchments of the Brisbane River, Queensland, Australia, were mixed as a result of a translocation. At the time, they were thought to represent slightly divergent populations of a single species. However, subsequent molecular analysis showed that they were significantly divergent. An analysis of patterns at one of the sites in 2001 suggested that the translocated lineage might be sending the resident population extinct in one of the streams. Analysis of mitochondrial deoxyribonucleic acid (DNA) and 3 allozyme loci indicated that the explanation for the outcome might be related to asymmetrical hybridization and nonviability of hybrids between resident females and translocated males. We present data for 2002 and an analysis of samples that had been collected prior to the 2001 study, but not analyzed. We tested 3 hypotheses: 1) the translocated genotypes would continue to increase in relative frequency at sites above the translocation site because their site of origin was at higher altitudes, to which they were expected to be better adapted; 2) at intermediate sites, the relative frequency of translocated alleles in juveniles would increase relative to in their parents; and 3) resident genotypes would survive better than translocated genotypes within a generation, especially at lower and intermediate elevations. Translocated genotypes increased extremely rapidly at the most upstream site. Consistent evidence was present for higher relative frequency of translocated alleles in juveniles relative to their parents, both in the generation following the 2001 study and in the pre-2001 samples. With the exception of in the upstream site, translocated genotypes had lower fitness within a generation than resident genotypes. Thus, the translocated genotypes had a higher reproductive success but were less well adapted to their local environment than residents, a situation that decreased population fitness overall. Such an outcome demonstrates a rarely reported effect of translocations and mixing of divergent lineages. Yes Yes
Northern Australia and southern Papua New Guinea (PNG) showing regions and drainage basins sampled for Denariusa bandata. Drainage basins are numbered as in Table 1, and the 3 main unsampled populations are indicated with the letters A (Cape Flattery dune lakes), B (Archer and Wenlock River drainages), and C (Bensbach River drainage in southern PNG). The exposed Australia–New Guinea Continental Shelf is shown by the broken black lines, and putative Pleistocene hydrological connections, including Lake Carpentaria, between Australia and PNG and across northern Australia, are indicated by thin black lines. Map redrawn from Voris (2000).  
Two-dimensional multidimensional scaling (MDS) plot of pairwise W ST among drainage basins showing patterns of genetic differentiation among populations of Denariusa bandata from drainage basins and regions. Labels refer to drainage basins; regions are indicated by the fills in the diamonds. CYP = Cape York Peninsula, PNG = Papua New Guinea.  
Plot of estimated coalescent times for pairwise comparisons of regional populations. A = Top End vs northwestern Cape York Peninsula, B = Top End vs Wet Tropics, C = Top End vs Papua New Guinea, D = northwestern Cape York Peninsula vs Wet Tropics, E = northwestern Cape York Peninsula vs Papua New Guinea, F = Wet Tropics vs Papua New Guinea, G = Clade 4-1 vs Clade 4-2.  
Pennyfish, Denariusa bandata, are small freshwater fish widely distributed in northern Australia in 4 highly disjunct regions and in the Fly River and Bensbach River drainages in southern Papua New Guinea (PNG). Alternating phases of exposure of the Australia–New Guinea Continental Shelf (ANGCS) during stands of lowered sea levels during Pleistocene glacial phases created a land bridge and fresh/brackish water habitats that intermittently connected Australia and PNG. Some biogeographic theories and empirical evidence for several freshwater crustaceans suggest that wetlands on the exposed ANGCS during the last glacial maximum were an important conduit for dispersal and gene flow in freshwater species between Australia and PNG and across northern Australia and that connectivity was severed by the most recent sea level rise in the region (6–8 thousand years before present). We used mitochondrial deoxyribonucleic acid (mtDNA) sequence data to test phylogeographic hypotheses concerning the origin of the disjunct distribution in D. bandata in relation to dispersal–vicariant processes and exposure of the ANGCS during Pleistocene sea level changes. Rather than a late Pleistocene origin associated with the last glacial maximum, the coalescence of the regional populations was in the early- to mid-Pleistocene, and the molecular data indicated that the eastern regional populations split before the northern populations split (i.e., sequential vicariance), whereas the northern populations split contemporaneously (i.e., simultaneous vicariance). The complex mtDNA genealogy for D. bandata also indicated a phylogeographic history in which ancestral lineages were retained in the northwestern part of its distribution, and ancestral haplotype diversity was retained in the Fly River (PNG) population because several divergent clusters of PNG haplotypes were more closely related to Australian haplotypes than to each other. Yes Yes
Nonmetric multidimensional scaling ordination plot of invertebrate densities including juvenile Corbicula (A) and excluding juvenile Corbicula (B). Treatment codes are: 0 ¼ bare sand, 1 ¼ shells, and 2 ¼ live adults.  
Analysis of variance results for benthic taxa (.1% of total density). (*) ¼ not significant after sequential Bonferroni adjustment; * ¼ significant with 0.05 . a . 0.01, *** ¼ a , 0.001.
Results of analysis of similarity (ANOSIM) for differences in community composition between treatments.
The Asian clam Corbicula has become established worldwide in a wide range of freshwater ecosystems. Corbicula fluminea invaded Lake Constance (Central Europe) between 2000 and 2002 and has reached densities up to 3520 individuals > 5 mm in length per square meter in sandy areas. However, the effect of this species on other benthic invertebrates remains unclear. Here, we show that ecosystem engineering via shell production by C. fluminea in Lake Constance considerably increases availability of hard surfaces in primarily soft-bottomed habitats. We studied effects of C. fluminea on littoral communities of sandy habitats using boxes containing bare sand, sand with C. fluminea shells (2000/m²), and sand with live clams (1000/m²). After 2 mo of exposure, the overall benthic community did not differ among treatments, but density of the mayfly Caenis spp. increased in boxes containing shells compared to the boxes containing sand or sand with live clams (analysis of variance [ANOVA], p < 0.0001). The density of shells greatly increased after mass mortality of C. fluminea populations. Our results indicate that shells can provide valuable hard surfaces for species that prefer structured habitats, especially in unstructured soft-bottomed habitats. In addition, density of juvenile C. fluminea was lower in boxes containing live adult clams than in boxes containing sand or sand and shells (ANOVA, p = 0.0048), possibly because of a chemical cue that might hinder settlement of juveniles in areas with high intraspecific concurrence.
Box-and-whisker plots of N 2 -fixation (n ¼ 22), NO 3 – -N-uptake (n ¼ 87), NH 4 þ -N-uptake (n ¼ 67), and denitrification (n ¼ 62) rates from the literature-review streams. The box plot shows the median (middle line), 1 st and 3 rd quartiles (top and bottom of box), 95% confidence intervals (whiskers), and outlier values (dots). Rates were converted to hourly rates to facilitate comparison. Plots with the same letters are not significantly different (post hoc Mann–Whitney U tests with a Dunn–Sidak-corrected a value).  
Frequency plots of N 2 -fixation and denitrification rates by month of study (A), stream discharge (Q) (B), and NO 3 À -N concentration (conc) (C), and of NO 3 – -N-and NH 4 þ -N-uptake rates by month of study (D), stream discharge (E), and NO 3 À -N concentration (F). All data are from the literature-review streams (Appendix). For studies done in the Southern Hemisphere, months were coded as the equivalent Northern-Hemisphere month (e.g., January was coded as July).  
Denitrification (A) and N 2 -fixation (B) rates vs NO 3 À -N concentration for studies where NO 3 À -N concentrations were available (denitrification n ¼ 50, N 2 fixation n ¼ 20). Note similarity of both rates at low NO 3 À concentrations.  
We evaluate the current state of knowledge concerning the ecosystem- and community-level importance of N2 fixation in streams. We reviewed the literature reporting N2-fixation contributions to stream N budgets and compared in-stream N2-fixation rates to denitrification and dissolved inorganic N (DIN)-uptake rates. In-stream N2 fixation rarely contributed >5% of the annual N input in N budgets that explicitly measured N2 fixation, but could contribute higher proportions when considered over daily or seasonal time scales. N2-fixation rates were statistically indistinguishable from denitrification and DIN-uptake rates from the same stream reach. However, published N2-fixation rates compiled from a wide variety of streams were significantly lower than denitrification or DIN-uptake rates, which were indistinguishable from one another. The data set we compiled might be biased because the number of published N2-fixation measurements is small (9 studies reporting rates in 22 streams), the range of stream conditions (NO3–-N concentration, discharge, season) under which N2-fixation and other N-processing rates have been measured is limited, and all of the rate estimates have associated methodological artifacts. To broaden our understanding of how N2 fixation contributes to stream ecosystems, studies must measure all rates concurrently across a broad range of stream conditions. In addition, focusing on how N2 fixation supports food webs and contributes to benthic community dynamics will help us understand the full ecological ramifications of N2 fixation in streams, regardless of the magnitude of the N flux into streams from N2 fixation.
The location of a stream reach relative to other landforms in a watershed is an important attribute. We hypothesized that lakes disrupt the frequency of finer, more mobile sediments and thereby change sediment transport processes such that benthic substrates are more stable (i.e., less mobile) below lakes than above lakes. In turn, we hypothesized that this reduced mobility would lead to greater periphyton biomass below lakes. We tested these hypotheses in study reaches above and below lakes in 3 mountain watersheds. To expand this comparison, we analyzed the relationship between sediment attributes and periphyton biomass in one watershed with and one watershed without a lake. We hypothesized that no clear pattern or change in sediment size or chlorophyll a (chl a) would be observed over a 3-km-long study reach without a lake. In contrast, we expected a clear discontinuity in both sediment size and chl a in a 7-km-long study reach interrupted by a lake. Average median sediment size (D50) was significantly larger (p < 0.01) in lake-outlet than lake-inlet reaches (41 mm vs 10 mm). Bed sediments in lake-outlet reaches were immobile during bankfull flows, whereas sediments at lake-inlet reaches were mobile during bankfull flows. Chlorophyll a was ≥10× greater in lake-outlet reaches than in lake-inlet reaches, although this difference was not statistically significant (p = 0.17). The longitudinal analysis clearly showed geomorphic transitions in sediment size and mobility downstream of mountain lakes, and these geomorphic transitions might be associated with changes in periphyton biomass. Geomorphic transitions can alter sediment transport and should be considered in concert with other factors that are considered more commonly in benthic ecology, such as light, nutrients, and temperature.
Study sites on the Big Salmon (A) and Upper Salmon (B) rivers, New Brunswick, that were sampled in 2004.
Season-, site-, and habitat-specific values of invertebrate d 13 C signatures plotted as a function of biofilm (A), macrophyte (B), cyanobacteria (C), and filamentous algae (D) d 13 C signatures. Dashed lines and equations indicate regressions of the data points, and the solid line is the 1:1 line.  
Aquatic food webs use C derived from 2 sources: autochthonous (derived from inside the water body) and allochthonous (derived from outside the water body). Various autochthonous sources are available to consumers (e.g., algae, mosses, macrophytes), and stable isotope analysis can be used to differentiate among C sources and to determine which sources sustain aquatic communities. The goal of our study was to determine which C sources contribute to the autochthonous pathways in 2 oligotrophic rivers, the Upper Salmon and Big Salmon, in New Brunswick (Canada). Samples were taken from headwaters to river mouth (above head of tide) at 17 study sites distributed across subbasins and stream orders. Vegetation samples included macrophytes, filamentous algae, biofilm, and aquatic bryophytes. Macroinvertebrate taxa in the scraper (grazer) functional feeding group were collected to represent primary consumers that feed primarily on autochthonous food sources. Macrophyte and cyanobacteria δ13C values were correlated with scraper δ13C values (r = 0.55 and 0.47, respectively), but δ13C of most scrapers was more depleted than δ13C of these food sources (>40% and >90%, respectively). Trophic fractionation is primarily an enrichment process, so these results indicated that macrophytes and cyanobacteria were not important food sources for primary consumers. Filamentous algae and biofilm δ13C values were poorly correlated with scraper δ13C values (r = 0.36 and 0.40, respectively), and >60% of the values were too depleted for these sources to be important food sources for scrapers. Ninety-eight percent of scraper δ13C values were enriched relative to bryophyte δ13C values, and bryophyte δ13C values were correlated with scraper δ13C values (r = 0.53), particularly when samples from slow-flowing habitats were removed from the analysis (r = 0.76). Spatial distributions of 2 important bryophyte taxa differed. Fontinalis sp. was abundant in headwater streams, and Drepanocladus sp. was abundant in low-order streams. Scrapers in low-order streams seemed to depend more on Fontinalis sp. than scrapers in high-order streams depended on Drepanocladus sp. Our results suggest that in low-productivity, nutrient-limited rivers, reduced availability of more preferred food sources (e.g., epilithic algae) might cause primary consumers to switch to marginal food sources, such as bryophytes. Further research is required to confirm this hypothesis and to eliminate confounding factors. Yes Yes
We examined the food quality of different fungi by determining growth, consumption and survivorship of two caddisflies fed diets of aspen leaves colonized by single fungal species. Mid-to-late fifth instar larvae of Hesperophylax magnus grew better on leaves colonized by Alatospora acuminata, Flagellospora curvula or Tetracladium marchalianum than on leaves colonized by Lemonniera aquatica or on stream detritus, but differences in instantaneous growth rates on these diets were not statistically significant. For early fifth instar larvae of Psychoglypha sp., we detected statistically significant differences in instantaneous growth rates on the following diets: F. curvula = A. acuminata > Heliscus lugdunensis = Articulospora inflata > L. aquatica = stream detritus. Psychoglypha sp. larvae also exhibited high survivorship on these diets through 20 d, but experienced 100% mortality when fed leaves colonized by Filosporella annelidica or T. marchalianum. Psychoglypha sp. larvae grew significantly faster on aspen leaves fully conditioned (10 d and 20 d) by F. curvula and H. lugdunensis than on preconditioned leaves (4 d). For both caddisflies, consumption rates were higher on diets that supported higher growth rates. Food quality of all four fungi in the Hesperophylax experiment and four of the seven fungi in the Psychoglypha experiment corresponded well with caddisfly preferences we have previously determined. Food quality was affected by fungal species and conditioning time. However, even well-conditioned leaves did not support high growth rates in caddisflies if the leaves were colonized by low quality fungi.
H (dD) and C (d 13 C) stable isotope ratios of biofilm and alder leaves from streams in New Brunswick, Canada.  
Stable H isotope ratios (D/H, expressed as dD) hold promise as an additional tool for elucidating food sources for consumers in aquatic ecosystems. We tested the applicability of dD as a food source tracer in streams of New Brunswick, Canada. First, we analyzed dD and d13C in biofilm and terrestrial leaves and compared signal-to-noise ratios (variability within sources vs variability between sources) between the 2 elements. Signal-to-noise ratios were roughly similar, and 23 of the 31 sites had isotopically distinct food sources based on dD compared to 20 of 31 based on d13C. Second, we used mixing models to estimate % aquatic H and % aquatic C for benthic invertebrates at a subset of sites. Of 16 samples, only 1 had d13C that was outside the range of the 2 food sources (yielding % aquatic C . 100%), but 12 of the 16 samples had dD outside the range of the food sources, a result suggesting confounding effects of water and lipids on total body H content. Last, we analyzed dD in laboratory-reared consumers (brook trout and water striders) and in their diet before and after lipid extraction to estimate diet–tissue fractionation. Large differences between consumer and diet were apparent before lipid extraction, but no significant differences were found after lipid extraction. All of these measures indicate that dD could serve as a complementary, but not alternative, isotopic method for estimating food sources for consumers in streams. Further laboratory trials are needed to explore the influence of lipids on dD values. Yes Yes
Rivers at Risk is an invaluable handbook that offers a practical understanding of how to influence government decisions about hydropower development on America's rivers.
Five biological metrics, calculated for the combined spring and autumn sample, plotted against the D5C1 (indicative weights 1-5) (A) and D16C1 (indicative weights 1, 2, 4, 8, 16) (B) discharge dynamics index over one hydrological year. Only the trend lines for significant relations are shown. v-index = current velocity index, sindex = saprobity index, r-index = rarity index, H-index = Shannon diversity, LIFE = Lotic-invertebrate Index for Flow Evaluation.
Mean (+1 SD) difference in the discharge dynamics indices (DDIs) D5C1 and D16C1 for combined discharge exceedances (A) and DDIs D5O1, D16O1, D5U1, and D16U1 for separated over and under exceedances (B) between the current climate situation (scenario Cn) and all other climate or land-and water-use scenarios. Hc = uncorrected Hadley Center prediction, Hp = corrected Hadley Center prediction, HpEn = corrected Hadley Center prediction with Ecological Network landuse change, HpEnBu = corrected Hadley Center prediction with Ecological Network landuse change and riparian buffers, HpEnBuMe = corrected Hadley Center prediction with Ecological Network landuse change, riparian buffers, and stream meandering.  
Despite the uncertainties in the rate of climate change, the Atlantic zone of northwestern Europe is expected to experience warmer, wetter winters and wetter summers than at present. Summer precipitation probably will depend on short, heavy rain showers between dry periods. Changes in the amount, frequency, and intensity of precipitation are expected to change stream discharge patterns, especially in rainwater-fed lowland streams, which will shift toward more dynamic flow regimes. Indices of discharge dynamics were used to assess the effect of changes in climate through changes in hydrology and land and water use on natural lowland stream macroinvertebrate communities. Discharge dynamics were significantly correlated with macroinvertebrate community structure, current velocity, and organic material preference. Our results demonstrate important influences of dynamic discharge regimes and extreme flows on macroinvertebrate community structure. Predictions of the ecological effects of climate change and of changes in land and water use indicate impaired ecological conditions in lowland streams of the Atlantic zone of northwestern Europe. Scenario tests involving different climate and landuse options suggest that current restoration practices and planned restoration activities can positively interact to reduce negative effects of climate change on lowland stream ecosystems.
We measured shell length, hinge length, and height of glochidia from 21 freshwater mussel species occurring in the Sipsey River, Alabama, to test our ability to identify species based on these glochidial morphometrics. Glochidial size and shape differed widely among species; for all 3 dimensions, mean values for the largest species were 5 to 73 greater than for the smallest species. Within-species variation in glochidia size was low for all species with the exception of Pleurobema decisum, which was represented by 2 glochidial morphotypes; variation within each morphotype was similar in magnitude to variation within other species. We were able to classify 72 to 79% of total glochidia (n = 870 or 750, respectively) to the correct species with discriminant function analysis. Percentage of correct classification ranged from 40 to 100% for individual species. Misclassifications were caused by overlap in shell dimensions between some species, but even species with poor classification success were confounded with an average of only 2.2 to 3.0 other species. Unlike previous studies, we found that glochidia of closely related species were not necessarily more similar to each other than to glochidia of more distantly related species. For example, species in the tribe Quadrulini were widely divergent in glochidium size and represented some of both the smallest and largest glochidia in our study. These 3 shell measurements and subsequent application of discriminant function analysis can be useful for identification of unknown glochidia or for rapidly narrowing the range of potential species identifications to smaller groups of species with similar glochidia.
"In Lifelines, Tim Palmer addresses the fate of our waterways. While proposals for gigantic federal dams are no longer common, and some of the worst pollution has been brought under control, myriad other concerns have appeared -- many of them more subtle and complex than the threats of the past.Palmer examines the alarming condition of rivers in today's world, reports on the success in restoring some of our most polluted streams and in stopping destructive dams, and builds the case for what must be done to avoid the collapse of riparian ecosystems and to reclaim qualities we cannot do without. He documents the needs for a new level of awareness and suggests ways to avert the plunder of our remaining river legacy.Lifelines offers a fresh perspective on: the values of natural rivers current threats to streams and possibilities for reform the continuing challenge of hydropower development water quality, instream flows, and riparian habitat ecosystem management and watershed protection the need for vision, hope, and action
Benthic macroinvertebrate families were sampled along 3 rivers in New Brunswick, Canada. Stable isotopes of C and N were compared between body tissue and gut contents of individuals. d13C and d15N of body tissue and gut contents were strongly correlated (r 5 0.94 and 0.93, respectively) over a wide range of d values. In nonpredators, only minor fractionation of d13C and d15N was observed. In predators, diet–tissue fractionation of 13C was minor, but 15N fractionation that may have been related to diet quality (N content) was observed. The influence of diet quality on N-isotope fractionation was inconsistent in direction and strength among families. Our results suggest that subjecting primary consumers to gut clearance prior to processing for stable-isotope analysis is unnecessary, but the guts of predators should be removed before processing. Yes Yes
Lakes can play a large role in structuring the chemical and physical templates of streams, yet they often are overlooked when stream function is evaluated. We examined how lakes within stream networks affect organic matter decomposition. We used a cotton-strip assay to evaluate cellulose decomposition potential (CDP) as loss of cotton-strip tensile strength in streams upstream and downstream of 4 mountain lakes in a lake district in the Sawtooth Mountains, Idaho. In addition, we used this assay to determine decomposition potentials along a longitudinal gradient in 1 stream–lake network. Decomposition coefficients (k) were 43% greater in lake-outflow streams than lake-inflow streams. Temperature explained 65% of the variability in decomposition rates across lake inflows and outflows, and decomposition rates in inflow streams were highly correlated with mean daily temperature (r = 0.99). Conversely, decomposition rates in outflow stream were strongly correlated with total N/total P ratios (TN/TP; r = 0.94). When temperature ranges were small, as was observed across 4 lake outflows and along a longitudinal gradient, decomposition rates appeared to be driven by differences in nutrient availability, mainly TP and, to a lesser extent, TN. Together, these results demonstrate that although temperature is a primary driver of decomposition, when temperature is similar across locations, nutrient availability can drive decomposition rates. Our results indicate that lakes within fluvial networks can modify stream function by altering both temperature and nutrient availability.
Sampling locations in Puerto Rico. Shadings indicating marine regions are used in Fig. 2 to show regional distribution of haplotypes.
Haplotype networks for 11 amphidromous species from Puerto Rico: Atya lanipes (A), Atya scabra (B), Atya innocous (C), Xiphocaris elongata (D), Macrobrachium faustinum (E), Micratya poeyi (F), Micratya sp. (G), Sicydium buscki (H), Sicydium punctatum (I), Sicydium sp. (J), and Neritina virginea (K). Each circle represents a haplotype. The size of the circle represents the relative frequency of the haplotype in the sample, and the colors represent the region where each haplotype was found (see Fig. 1).
Various components of island stream faunas, including caridean shrimps, fish, and gastropods, undertake obligate amphidromous migration, whereby larvae are released in upstream freshwater reaches, drift downstream to estuaries or marine waters, then migrate upstream as postlarvae to freshwater adult habitats. Longitudinal migration from estuaries to headwaters is well documented for many amphidromous species, but the degree of among-river marine dispersal is poorly known for most species. We need better understanding of the potential for marine dispersal in population processes of amphidromous species, particularly recolonization and population recovery in impacted lotic systems, such as those on Puerto Rico, because some theories of dispersal for species with marine larvae predict high rates of self-recruitment. We tested population genetic predictions for widespread marine larval dispersal and self-recruitment to the natal river for 11 amphidromous species, including shrimps, fish, and a gastropod, in Puerto Rico. Population genetic analysis of mitochondrial DNA data showed high rates of gene flow among rivers and indicated that marine dispersal determines the population genetic structure of all 11 species. Difficulty in recruiting to oceanic currents promotes closed population structures in some marine species, but larvae of amphidromous species entrained in downstream river flow might be delivered more readily to ocean currents. Population recovery processes occurred at the island scale rather than at the river scale, but further studies are needed to identify whether population recovery processes are likely at larger spatial scales (e.g., among islands). River management strategies should maintain environmental flows that allow larval export, maintain longitudinal dispersal pathways over dam spillways and via subterranean passages, and maintain open and healthy estuaries. Yes Yes
Originally published in: J. N. Am. Benthol. Soc., 2006, 25(2):304–312Release of P from lake sediments may account for a significant portion of a lake’s total P (TP) load. Previous studies using sediment cores showed that ;65% of the total P load entering Spring Lake, Michigan, came from the sediments, and that an alum concentration of 24 mg Al/L effectively inactivated P release in experimental sediment-core tubes. In 2004, we studied the influence of alum concentration and sediment resuspension on P release rates from the sediments. Based on laboratory incubations using alum concentrations of 0, 5, 10, 15, 20, and 25 mg/L, we determined that P release rates at alum concentrations 15 mg/L were no different than at release rates at concentrations of 25 mg/L. Resuspension of sediments substantially increased TP concentrations, even at high alum concentrations, but total soluble P concentrations remained low in the water when alum was present. Alum application may be an effective tool to reduce P flux from sediments in shallow lakes, but external P load reduction must accompany alum application to address the long-term impacts associated with cultural eutrophication.
Recent developments and perspectives in mountain river research.- Human impact and exploitation of water resources in the Northern Alps (Tyrol and Bavaria).- Model investigations into the influence of renaturalization on sediment transport.- Bedload transport and discharge in the Erlenbach stream.- Sediment transport and water discharge during high flows in an instrumented watershed.- Luminophor experiments in the Saalach and Salzach rivers.- The downstream fining of gravel-bed sediments in the Alpine Rhine River.- River channel adjustment and sediment budget in response to a catastrophic flood event (Lainbach catchment, Southern Bavaria).- The influence of channel steps on coarse bed load transport in mountain torrents: case study using the radio tracer technique 'PETSY'.- The significance of fluvial erosion, channel storage and gravitational processes in sediment production in a small mountainous catchment area.- An attempt at modelling suspended sediment concentration after storm events in an Alpine torrent.- Investigations of slope erosion in the Northern Limestone Alps.- Streambed dynamics and grain-size characteristics of tow gravel rivers of the Northern Apennines, Italy.- Discharge and fluvial sediment transport in a semi-arid high mountain catchment, Agua Negra, San Juan, Argentina.- Sediment transport and discharge in a high arctic catchment (Liefdefjorden, NW Spitsbergen).- Hydraulics and sediment transport dynamics controlling step-pool formation in high gradient streams: A flume experiment.- Short term temporal variations in bedload transport rates: Squaw Creek, Montana, USA and Nahal Yatir and Nahal Estemoa, Israel.- Measuring systems to determine the velocity field in and close to the roughness sublayer.- An attempt at determination of incipient bed load motion in mountain streams.- Quantification of textural particle characteristics by image analysis of sediment surfaces-examples from active and paleo-surfaces in steep, coarse-grained mountain environments.- Some considerations on debris flow rheology.
Sumario: Background and motivation for ecological risk analysis -- Toxicological and ecological data for risk analysis -- An aquatic ecosystem model for risk analysis -- Modeling sublethal toxic effects -- Forecasting risk in aquatic ecosystems -- Evaluation of the risk forecasting methodology -- Comparisons of predicted and measured effects -- Conclusions and future directions.
Measurements of shell growth rate showed that a difference in the population structure of Potamopyrgus jenkinsi between the northern and the southern shore of a small Dutch lake could be a result of food quality of the sediment. In further studies, a series of diets differing in organic C and N content was offered to the snails. There was no functional relationship between growth rate and C or N content of the diets. Growth rate plotted against the C/N ratios of the diets followed an optimum curve with a maximum at a C/N value of 15.9. Highest growth rate was followed by successful reproduction. In the lower C/N range, growth rate rapidly increased with small increases in C/N values. This kind of relationship supports previously disregarded findings for Artemia.
Most suspension-feeding trichopterans spin a fine-silk capture net that is used to remove suspended matter from the water. The efficiency of these nets has previously been studied by considering the geometry of the web structure but the material from which the nets is constructed has received little attention. We report measurements of the tensile strength and extensibility of net silk from Hydropsyche siltalai. These measurements place caddisfly silk as one of the weakest natural silks so far reported, with a mean tensile strength of 221 ± 22 megaNewtons (MN)/m2. We also show that H. siltalai silk can more than double in length before catastrophic breakage, and that the silk is at least 2 orders of magnitude stronger than the maximum force estimated to act upon it in situ. Possible reasons for this disparity include constraints of evolutionary history and safety margins to prevent net failure or performance reduction.
This book presents an analysis of research on the physical, chemical, and biological processes in aquatic systems, including transport/distribution of chemicals, aquatic surface chemistry, and geobiological cycles of trace elements. Attention is given to the solid-solution interface and to the dominant roles of settling particles and the sediment-water interface in regulating concentrations of heavy metals and other reactive substances. Measures for restoring euthrophied lakes are included.
Lake Superior has been known by many names through the centuries, from Kitchi Gami to le lac superieur, but the lake itself remains the same expansive and inspiring body of water. Here, Thomas F. Waters explores the natural and human history of the Superior basin. From the trout and salmon swimming in its icy depths to the red and white pines towering overhead, Lake Superior has an ancient past. As Waters depicts the geology of the region, he traces the development of the rugged shoreline from Duluth to Thunder Bay to Sault Ste. Marie. The Superior North Shore also vividly describes the human history lived out in this sometimes harsh, always spectacular natural setting, from the earliest Native Americans to the voyageurs to the modern fishing industry. Charmingly illustrated by Carol Yonker Waters, this volume conveys to the reader an intimacy with the legends of Lake Superior, as well as a sense of the grandeur behind this unique and vital ecological system. "Waters's vivid prose transports you from the volcanic origins of the Superior Basin, to the Ojibwe Kitchi Gami (the "great lake"), to the wild, daunting days of exploration and exploitation of the area's natural resources, primarily fur and fish." Imprint "Thomas F. Waters gives a detailed account of the region's land and waters, resources, and human settlement. His description of the series of frontiers--the fishermen's frontier, the mining frontier, the lumbering frontier, and the development of recreation--admirably combines human and natural history." Journal of Forest History Thomas F. Waters is a professor emeritus of the University of Minnesota. He is also the author of Streams and Rivers of Minnesota (1998).
The ability of a 3rd order Ozark Plateaus stream to efficiently retain nutrient inputs from a rural wastewater treatment plant (WWTP) was examined using the nutrient spiraling concept. Short-term injections are often used to assess nutrient spiraling, where exponential declines in injected nutrients reflected gross nutrient uptake. However, we applied the same mathematical equations to WWTP nutrient additions, where exponential declines in nutrient concentrations reflected net nutrient uptake. We estimated net nutrient uptake length (Snet), mass transfer coefficient (vnet), uptake rate (Unet) and nutrient flux (NF) at Columbia Hollow, Eucha - Spavinaw Basin, northwest Arkansas. Water samples were collected at a reference site upstream of the Decatur WWTP and six sites increasing in distance downstream of the WWTP. The Decatur WWTP had a significant effect on physicochemical properties and nutrient concentrations at Columbia Hollow; maximum phosphorus concentration was over 9 mg L-1 0.3 km downstream from the Decatur WWTP at Columbia Hollow. Net nutrient uptake lengths were generally in the km scale, suggesting several km were required to temporarily retain about 63% of the nutrients from the WWTP. Mass transfer coefficients were 10 times less than values reported in relatively undisturbed streams whereas net nutrient uptake rates were at least 7 times greater. Stream nutrient retention efficiency was significantly related to level of enrichment, seasonal changes and streamflow.
Tim Palmer weaves natural history into a comprehensive account of the complex problems that plague natural resource management throughout the West, as well as the practical solutions that are available.
Analysis of genetic variation among populations of stream invertebrates provides a measure of the consequences of effective dispersal, and can be used to determine the extent of movement within and between streams and to infer the likely mechanisms involved. In our recent studies of rainforest stream invertebrates, we have found considerable genetic differentiation among populations of fully aquatic taxa, indicating limited in-stream movement on a very small scale. Adult flight appears to be the principal mechanism of dispersal for aquatic insects; however, analysis of the genetic structure of larval populations of some species also suggests that in-stream movement is limited to a small spatial scale. Furthermore, detailed analysis of the genetic structure of larval populations suggests that recruitment at the reach scale is the result of only a few adult matings and most likely from oviposition by only a few females. We propose that dispersal capability and the stochastic effects of recruitment are kev determinants of observed spatial and temporal variation in community structure in some streams.
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N. LeRoy Poff
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Barry J. F. Biggs
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James R Karr
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