Publications

@article{Bouma-Gregson2021,

title = {Taxon-specific photosynthetic responses of attached algal assemblages to experimental translocation between river habitats},

author = {Keith Bouma-Gregson and Mary E. Power and Paula C. Furey and Casey J. Huckins and Yvonne Vadeboncoeur},

url = {https://www.journals.uchicago.edu/doi/pdf/10.1086/713095},

doi = {10.1086/713095},

year  = {2021},

date = {2021-02-25},

journal = {Freshwater Science},

volume = {40},

number = {1},

abstract = {Attached algal and cyanobacterial taxa differ in their ability to exploit and tolerate the diversity of flow, irradiance, and temperature regimes typical of a heterogeneous riverscape. Understanding the drivers of the small-scale variation in algal taxonomic composition helps us predict the riverscape-scale effects of altered flow regimes, but microhabitat-scale variation in algal taxonomy complicates the interpretation of ecosystem-scale estimates of biomass or primary production. Using pulse-amplitude modulated (PAM) fluorometry, we performed 2 manipulative field experiments (in 2014 and 2015) to measure photosynthetic responses of algae and cyanobacteria to depth, temperature, and flow modifications. In 2014, we exposed 6 attached algal assemblages common to the South Fork Eel River (California, USA) to a 24-h incubation on either the river bottom (20 cm deep) or floating at the water surface. In 2015, we incubated 3 algal assemblages for 1 wk in either the thalweg or at the river’s edge. For PAM measurements, we developed a novel method (Photosynthesis–Irradiance Periphyton Experimental System [PIPES]) for manipulating attached filamentous algae, a morphology common in aquatic habitats but underrepresented in photosynthesis experiments. To make the PIPES, we sandwiched thin (<1 mm) layers of filamentous attached algae between 2 layers of mesh so that the algae could be isolated and manipulated for repeated PAM measurements. In the 2014 experiment, incubating Cladophora, Rivularia, Microcoleus, and Anabaena at the water surface tended to decrease photosynthetic rates relative to submerged controls, whereas for Nostoc, the photosynthetic rates were higher in floating treatments. In the 2015 experiment, Cladophora and Oedogonium incubated in the warmer, low-flow river margin had persistently lower photosynthesis rates than their counterparts incubated in the thalweg. The PIPES method improves our ability to make PAM measurements on attached algae. PIPES can be used in conjunction with other methods to evaluate taxon-specific responses to environmental conditions and to help us predict how algal assemblages will shift in dominance under different river management regimes.},

keywords = {algae, benthic, Cladophora, cyanobacteria, electron transport rate, flow, Microcoleus, microhabitat, PAM, photosynthesis, temperature},

pubstate = {published},

tppubtype = {article}

}

@article{Stancheva2019,

title = {First record of the rare freshwater alga Tetrasporopsis fuscescens (Chrysomerophyceae, Ochrophyta) in North America},

author = {R Stancheva and P Škaloud and M Pusztai and CL Loflen and RG Sheath},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/fottea_fot-201902-0006.pdf},

doi = {10.5507/fot.2019.007},

year  = {2019},

date = {2019-10-30},

urldate = {2019-10-30},

journal = {Fottea},

volume = {19},

issue = {2},

pages = {163-174},

abstract = {This study presents the first record of the ochrophyte alga Tetrasporopsis fuscescens in North America, confirmed with light and transmission electron microscopic photomicrographs, cytochemical and molecular phylogenetic analyses. T. fuscescens was recorded rarely, being found in the benthos of only twelve stream sites: nine locations in Southern California and three in Northern California. More than half of the streams were non-perennial, characterized by long dry periods. Tetrasporopsis cells were gold-colored, spherical, with a distinct wall, assembled in the periphery of macroscopical gelatinous colonies, which start as tubular or sac-like structures, but later become membranous. The cells have 1-2 parietal chloroplasts, without a stigma or pyrenoid, and reproduction occurs by longitudinal cell division. Other features of the genus are as follows: cells in the colonies also divide by what appears to be smaller autospores with remnant cell walls remaining, the colonial mucilage consists of cylindrical dichotomously branched tubes radiating from the center of the colony to which attach the peripheral cells, and older cells become filled with large oil droplets. A combined gene tree of sequences from nuclear SSU rDNA, plastid rbcL, psaA, psbA and psbC showed that T. fuscescens specimens from Europe and U. S. A. formed a clade, which clustered with taxa classified in the class Chrysomerophyceae.},

keywords = {algae, freshwater, freshwater ecosystem},

pubstate = {published},

tppubtype = {article}

}

@article{Bouma-Gregson2019,

title = {Impacts of microbial assemblage and environmental conditions on the distribution of anatoxin-a producing cyanobacteria within a river network},

author = {Keith Bouma-Gregson and Matthew R. Olm and Alexander J. Probst and Karthik Anantharaman and Mary E. Power and Jillian F. Banfield},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/ACFrOgCi6hBdMfYejhSBBRhowH7uEzKdYcuAjfK9v1rJWg3ajgn9fFrFZmnWAY1cjZKhRQuhAhjSjhR6b_fShyPM32lKV7Coi7lFfnbS4xgM02VVqWdiTojYom8fl1nvtqMdQfs3mn-oTmwNlMoG-1.pdf},

doi = {10.1038/s41396-019-0374-3},

year  = {2019},

date = {2019-02-26},

journal = {The ISME Journal},

volume = {13},

pages = {1618–1634},

abstract = {Blooms of planktonic cyanobacteria have long been of concern in lakes, but more recently, harmful impacts of riverine benthic cyanobacterial mats been recognized. As yet, we know little about how various benthic cyanobacteria are distributed in river networks, or how environmental conditions or other associated microbes in their consortia affect their biosynthetic capacities. We performed metagenomic sequencing for 22 Oscillatoriales-dominated (Cyanobacteria) microbial mats collected across the Eel River network in Northern California and investigated factors associated with anatoxin-a producing cyanobacteria. All microbial communities were dominated by one or two cyanobacterial species, so the key mat metabolisms involve oxygenic photosynthesis and carbon oxidation. Only a few metabolisms fueled the growth of the mat communities, with little evidence for anaerobic metabolic pathways. We genomically defined four cyanobacterial species, all which shared <96% average nucleotide identity with reference Oscillatoriales genomes and are potentially novel species in the genus Microcoleus. One of the Microcoleus species contained the anatoxin-a biosynthesis genes, and we describe the first anatoxin-a gene cluster from the Microcoleus clade within Oscillatoriales. Occurrence of these four Microcoleus species in the watershed was correlated with total dissolved nitrogen and phosphorus concentrations, and the species that contains the anatoxin-a gene cluster was found in sites with higher nitrogen concentrations. Microbial assemblages in mat samples with the anatoxin-a gene cluster consistently had a lower abundance of Burkholderiales (Betaproteobacteria) species than did mats without the anatoxin-producing genes. The associations of water nutrient concentrations and certain co-occurring microbes with anatoxin-a producing Microcoleus motivate further exploration for their roles as potential controls on the distributions of toxigenic benthic cyanobacteria in river networks.},

keywords = {algae, cyanobacteria, ERCZO},

pubstate = {published},

tppubtype = {article}

}

@article{Bouma-Gregson2018,

title = {Widespread anatoxin-a detection in benthic cyanobacterial mats throughout a river network},

author = {Keith Bouma-Gregson and Raphael M. Kudela and Mary Power},

doi = {https://doi.org/10.1371/journal.pone.0197669},

year  = {2018},

date = {2018-05-18},

journal = {PLoS One},

volume = {13},

number = {5},

abstract = {Benthic algae fuel summer food webs in many sunlit rivers, and are hotspots for primary and 

secondary production and biogeochemical cycling. Concerningly, riverine benthic algal 

assemblages can become dominated by toxic cyanobacteria, threatening water quality and 

public health. In the Eel River in Northern California, over a dozen dog deaths have been 

attributed to cyanotoxin poisonings since 2000. During the summers of 2013–2015, we documented 

spatial and temporal patterns of cyanotoxin concentrations in the watershed, 

showing widespread distribution of anatoxin-a in benthic cyanobacterial mats. Solid phase 

adsorption toxin tracking (SPATT) samplers were deployed weekly to record dissolved 

microcystin and anatoxin-a levels at 10 sites throughout the watershed, and 187 Anabaenadominated 

or Phormidium-dominated cyanobacterial mat samples were collected from 27 

locations to measure intracellular anatoxin-a (ATX) and microcystins (MCY). Anatoxin-a levels were higher than microcystin for both SPATT (mean MCY = 0.8 and ATX = 4.8 ng g resin-1 day-1) and cyanobacterial mat samples (mean MCY = 0.074 and ATX = 1.89 μg g-1 DW). Of the benthic mats sampled, 58.9% had detectable anatoxin-a (max = 70.93 μg g-1 DW), while 37.6% had detectable microcystins (max = 2.29 μg g-1 DW). SPATT cyanotoxin 

levels peaked in mid-summer in warm mainstem reaches of the watershed. This is one of 

the first documentations of widespread anatoxin-a occurrence in benthic cyanobacterial 

mats in a North American watershed.},

keywords = {algae, biodiversity, ERCZO},

pubstate = {published},

tppubtype = {article}

}

@article{Power2009,

title = {Algal mats and insect emergence in rivers under Mediterranean climates: Towards photogrammetric surveillance},

author = {M. Power and R. Lowe and P. Furey and J. Welter and M. Limm and J. Finlay and C. Bode and S. Chang and M. Goodrich and J. Sculley},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_2009_FreshBio.pdf},

doi = {10.1111/j.1365-2427.2008.02163.x},

year  = {2009},

date = {2009-02-23},

journal = {Freshwater Biology},

volume = {54},

number = {10},

pages = {2101–2115},

abstract = {1. In a nitrogen (N)-limited river subject to Mediterranean summer drought hydrology, the colour of macroalgal proliferations changed with successional and seasonal changes in epiphyte assemblages. New growth of the dominant macroalga, Cladophora glomerata, was green, as were proliferations of Oedogonium, Mougeotia and Spirogyra, which did not become heavily colonized with diatoms. Green Cladophora turned yellow as Cladophora filaments became colonized by diatoms that were not N fixers, and turned rust-coloured as later-successional epiphyte assemblages became dominated by dense Epithemia turgida and E. sorex, which both contain N-fixing cyanobacterial endosymbionts. 

2. The rate and composition of insect emergence from floating algal mats differed among proliferations of different colour. The rates of emergence (individuals day−1 500 cm−2) of nematoceran flies were three to 25 times greater from yellow or rusty-coloured Cladophora mats than from green Cladophora, Oedogonium or Mougeotia mats that had lower epiphyte densities. Biomass emergence from Cladophora mats that were rusty in colour was eight to 10 times greater than from yellow Cladophora mats, because larger nematocerans dominated in rusty mats (Chironominae versus Ceratopogonidae in yellow mats). 

3. Proliferations of Epithemia-infested Cladophora occur at and above drainage areas of about 100 km2 (channel widths of 25–30 m) in this river network, coinciding with the drainage area threshold where a step increase in concentration of total dissolved N is observed during summer. 

4. In rivers under Mediterranean climate regimes, algal succession during the prolonged low flow season is less subject to stochastic interruption by spates than in rivers under more continental climates. Under these summer drought conditions, photogrammetric detection of colour changes in algal proliferations may help us track reach or basin-scale change in their ecological functions.},

keywords = {algae, epiphytic algae, Insect emergence, nitrogen fixers, photogrammetric surveillance},

pubstate = {published},

tppubtype = {article}

}

@article{Finlay2001,

title = {Stable-carbon-isotope ratios of river biota: Implications for energy flow in lotic food webs},

author = {Jacques C. Finlay},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/STABLE-CARBON-ISOTOPE-RATIOS-OF-RIVER-BIOTA-IMPLICATIONS-FOR-ENERGY-FLOW-IN-LOTIC-FOOD-WEBS_Finlay_2001.pdf},

doi = {10.1890/0012-9658(2001)082[1052:SCIROR]2.0.CO;2},

issn = {0012-9658},

year  = {2001},

date = {2001-04-00},

journal = {Ecology},

volume = {82},

number = {4},

pages = {1052-1064},

abstract = {Stable-isotope ratios of carbon (13C/12C or δ13C) have been widely used to determine the energy base of stream food webs, but such use is controversial due to unexplained variability in algal δ13C. I used published δ13C data from temperate headwater streams through medium-sized rivers (0.2–4000 km2 watershed area) collected during summer baseflows and original data from streams in northern California to analyze energy pathways through river food webs. The analyses showed three important results. First, epilithic algal δ13C and watershed area are positively related, suggesting that effects of carbon limitation on algal carbon uptake result in 13C enrichment of algal δ13C in larger, more productive rivers. Second, epilithic algae and terrestrial detritus δ13C values are often distinct in small shaded streams but overlap in some larger unshaded streams and rivers. Measurements of δ13C values may be most useful in distinguishing algal and terrestrial energy sources in unproductive streams with supersaturated dissolved CO2 concentrations, and some productive rivers where CO2 concentrations are low relative to photosynthetic rates. Finally, consumer δ13C values are more strongly related to algal δ13C than terrestrial δ13C. The relative contribution of terrestrial and algal carbon sources often varied by functional feeding group within and between sites. However, with the exception of shredders and scrapers, which respectively relied on terrestrial and algal carbon sources, patterns of consumer δ13C clearly show a transition from terrestrial to algal carbon sources for many lotic food webs in streams with ≥10 km2 watershed area. The observed transition to algal carbon sources is likely related to increasing primary production rates as forest canopy cover declines in larger streams, although decreasing retention or quality of terrestrial carbon may also play a role. Improved analyses of algal δ13C and δ15N combined with quantitative study of organic matter dynamics and food web structure should allow the relative importance of these factors to be distinguished in future food web studies.},

keywords = {algae, carbon limitation, energy flow, lotic food webs, stable-carbon-isotope ratios, terrestrial detritus, watershed area, δ13C},

pubstate = {published},

tppubtype = {article}

}

@article{Kupferberg1997,

title = {Bullfrog (Rana catesbeiana) invasion of a California river: the role of larval competition},

author = {Sarah J. Kupferberg},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Kupferberg_Ecology1997.pdf},

issn = {0012-9658},

year  = {1997},

date = {1997-09-00},

journal = {Ecology},

volume = {78},

number = {6},

pages = {1736-1751},

abstract = {I studied the invasion of Rana catesbeiana (the bullfrog) into a northern California river system where bullfrogs are not native. Native yellow-legged frogs, Rana boylii, a species of special concern, were almost an order of magnitude less abundant in reaches where bullfrogs were well established. I assessed the potential role of larval competition in contributing to this displacement in a series of field manipulations of tadpole density and species composition. The impact of R. catesbeiana on native tadpoles in the natural community agreed with the outcome of more artificial experiments testing pairwise and three-way interactions. In 2-m(2) enclosures with ambient densities of tadpoles and natural river biota, bullfrog tadpoles caused a 48% reduction in survivorship of R. boylii, and a 24% decline in mass at metamorphosis. Bullfrog larvae had smaller impacts on Pacific treefrogs, Hyla regilla, causing 16% reduction in metamorph size, and no significant effect on survivorship. Bullfrog tadpoles significantly affected benthic algae, although effects varied across sites. Responses to bullfrogs in field settings were similar qualitatively to results seen in smaller-scale experiments designed to study size-structured competition among disparate age/size classes of species pairs and trios. Competition from large overwintering bullfrog larvae significantly decreased survivorship and growth of native tadpoles. Competition from recently hatched bullfrog larvae also decreased survivorship of R. boylii and H. regilla. Native species competed weakly, both interspecifically and intraspecifically. The only suggestion of a negative impact of a native species on bullfrogs was a weak effect of H. regilla on recent hatchlings. Competition appeared to be mediated by algal resources, and there was no evidence for behavioral or chemical interference. These results indicate that, through larval interactions, bullfrogs can exert differential effects on native frogs and perturb aquatic community structure.},

keywords = {algae, biological invasions, California, grazing, Hyla regilla, Rana boylii, Rana catesbeiana, rivers, size-structured competition},

pubstate = {published},

tppubtype = {article}

}

@article{111bp,

title = {Effect of stream flow regulation and absence of scouring floods on trophic transfer of biomass to fish in Northern California rivers},

author = {Michael S. Parker and Mary E. Power},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/parker-power-flow-regulation-food-webs-tech-report-1997-copy-1.pdf},

year  = {1997},

date = {1997-01-01},

urldate = {1997-01-01},

journal = {Technical Completion Report, University of California Water Resources Center},

volume = {UCAL-WRC-W-825},

number = {825},

abstract = {Scouring winter floods strongly influence the structure and dynamics of food webs in rivers with winter flood, summer drought hydrographs. Reduction or elimination of scouring floods, in addtition to altering physical conditions within rivers, may negatively affect salmonid populations by reducing energy flow to them from lower trophic levels. We compared food webs of two northern California rivers with drastically different flow regimes to assess the effects of differences in food web structure on the distribution and growth of juvenile steelhead trout. The upper Mad River has a highly regulated flow regime and rarely experiences scouring winter floods, while the upper Van Duzen River is free-flowing and experiences frequent scouring floods. Thrroughout spring and summer 1994 densities of the large, grazing caddisfly Dicosmoecus gilvipes exceeded 801m2 in the Mad River, but were < 21m2 in the Van Duzen. Consequently, filamentous green algae was nearly absent in the Mad from June through September, but was relatively abundant in the Van Duzen. Densities of other stream-dwelling insects (primarily Chironomids and mayflies, which are the preferred prey of juvenile salmonids) and juvenile steelhead were consistently mlich lower in the Mad than the Van Duzen. At the end of the summer, Dicosmoecus pupated, and thus became inactive, which resulted in a large bloom of filamentous green algae (primarily Oedogonium and Cladophora) and a several-fold increase in the densities of Chironomids and mayflies in the Mad but not the Van Duzen. River flows in 1995 were much higher than in 1994 and both rivers experienced a number of scouring floods. As a consequence, Dicosmoecus densities were reduced to < 21m2 in both rivers throughout the spring and summer. The Mad experienced a large Cladophora bloom, and densities of Chironomids and mayflies were several times higher in 1995 than 1994. These observations support our hypothesis that eliminating scouring floods favors large, slow-growing benthic insect taxa over smaller, faster-growing taxa whose populations build up rapidly after floods. Since the former are invulnerable to predation by juvenile salmonids, energy flow is reduced and juvenile salmonid populations decline. 

Experimental manipulation of juvenile steelhead in artificial channels with and without Dicosmoecus allowed us to test this hypothesis more directly and without potential influences from factors other than food web structure that may have varied between regulated and unregulated rivers. Experimental results revealed that Dicosmoecus significantly reduced the availability of small prey, which resulted in negative juvenile steelhead growth. Together, our surveys and experimental results show that elimination of scouring floods alters energy pathways in river food webs resulting in reduced biomass available to fish populations. Modifying flow regimes regulated by dams, so they more closely resemble natural hydrographs, may be an important step in restoring salmonid populations in some rivers.},

keywords = {algae, AQUATIC INSECTS, Benthos, Fish Ecology, Flood Control, geomorphology, River Beds, Water Diversion, Watershed Management},

pubstate = {published},

tppubtype = {article}

}

@article{Power1990,

title = {Benthic turfs vs. floating mats of algae in river food webs},

author = {M. E. Power},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_1990_Oikos.pdf},

doi = {10.2307/3565362},

year  = {1990},

date = {1990-05-01},

urldate = {1990-05-00},

journal = {Oikos},

volume = {58},

number = {1},

pages = {67-79},

abstract = {In the Eel River of northern California, as in many other sunlit rivers worldwide, 

large growths of filamentous green algae accumulate during summer low flow periods. Algae initially grow as turfs, attached to the river bed, but over time detach to form floating mats. Floating mats differ from attached turfs as habitats for invertebrates in a number of respects. In paired trials, larval chironomids were 15-16 times more likely to be consumed by fishes when exposed in algal turfs on the river bed than when exposed in floating algal mats on the river surface. On average, 2.7 and 6.1 times more adult insects emerged from floating mats than from benthic algal turfs in shallow (< 30 cm deep) and deep (30-60 cm deep) habitats, respectively. Differences between algal mats and turfs as cover and habitat for resident insects lead to the hypothesis that the timing, abundance, and duration of floating mat habitats strongly influences the routing of insect production in river food webs, to aquatic consumers or to the land.},

keywords = {algae, benthic turfs, floating mats},

pubstate = {published},

tppubtype = {article}

}

@article{Power1988,

title = {Biotic and abiotic controls in river and stream communities},

author = {Mary E. Power and R. Jean Stout and Colbert E. Cushing and Peter P. Harper and F. Richard Hauer and William J. Matthews and Peter B. Moyle and Bernhard Statzner and Irene R. Wais De Badgen},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_1988_BenthoSoc.pdf},

doi = {10.2307/1467301},

year  = {1988},

date = {1988-12-00},

journal = {Journal of the North American Benthological Society},

volume = {7},

number = {4},

pages = {456-479},

abstract = {Lotic ecologists share a major goal of explaining the distribution and abundance of biota in the world's rivers and streams, and of predicting how this biota will respond to change in fluvial ecosystems. We discuss five areas of research that would contribute to our pursuit of this goal. For mechanistic understanding of lotic community dynamics, we need more information on: 

1. Physical conditions impinging on lotic biota, measured on temporal and spatial scales relevant to the organisms. 

2. Responses of lotic biota to discharge fluctuations, including the processes that mediate community recovery following resets caused by spates or droughts. 

3. Movements of lotic organisms that mediate gene flow, resource tracking, and multilevel species interactions. 

4. Life history patterns, with special emphasis on ontogenetic bottlenecks that determine the vulnerability of populations confronting environmental perturbation. 

5. Consequences of species interactions for community- and ecosystem-level processes in rivers and streams. 

Without attempting to be comprehensive in our review, we discuss limits and limitations of our knowledge in these areas. We also suggest types of data and technological development that would advance our understanding. While we appreciate the value and need for empirical and comparative information, we advocate search for key mechanisms underlying community interactions as the crucial step toward developing general predictions of responses to environmental change. These mechanisms are likely to be complex, and elucidation of interacting bilateral, or multilateral, biotic and abiotic controls will progress only with the continuing synthesis of community- and ecosystem-level approaches in lotic ecology.},

keywords = {algae, COMMUNITIES, discharge, disturbance., fish, life histories, rivers, streams, zoobenthos},

pubstate = {published},

tppubtype = {article}

}

@article{Hill1987,

title = {Experimental analysis of the grazing interaction between a mayfly and stream algae},

author = {W. R. Hill and A. W. Knight},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Hill_1987_Eco.pdf},

doi = {10.2307/1939886},

year  = {1987},

date = {1987-12-01},

journal = {Ecology},

volume = {68},

number = {6},

pages = {1955-1965},

abstract = {The interaction between the grazing mayfly Ameletus validus and periphyton in a small, northern California stream was examined by manipulating the density of the mayfly in flow—through plexiglass channels. Containing natural cobble substrate and located in situ, the channels established an initial gradient of A. validus at 0, 0.5, 1, and 4 times the average density of the mayfly in Barnwell Creek. After 23 d, A. validus significantly depressed periphyton standing crop: ash—free dry mass (AFDM) at the 0, 0.5, 1, and 4 N grazer densities was 5.067 ± 1.389 (se), 1.829 ± 0.173, 1.741 ± 0.325, and 1.009 ± 0.199 g/m2 (ANOVA: P < .01). The mayfly also influenced two structural attributes of the periphyton, increasing the amount of chlorophyll a per unit biomass and decreasing the relative contribution of the loose, upper layer to total periphyton biomass. Principal component analysis of algal relative abundances contrasted the effect of grazing on two groups of diatoms. A group of species found primarily in the loose layer of periphyton (Nitzschia spp., Surirella spiralis, Cymatopleura elliptica, and Navicula cryptocephala) was disproportionately reduced in abundance, while an adnate group (Gomphonema clevei, Achnanthes minutissima, Synedra ulna, Rhoicosphenia curvata, and an undescribed species of Epithemia) increased its relative abundance with increasing grazing pressure. The decline in relative abundance of the loose layer diatoms did not appear to result from selective consumption by A. validus, but may have been mediated by a reduction of inorganic sediment in the periphyton by A. validus. Inorganic sediment was highly correlated with the relative abundances of the loose layer group of diatoms, a group of species that are adapted for locomotion on sediment substrates. A. validus growth in the experimental channels was strongly density dependent. Growth in length over 23 d for the 0.5, 1, and 4 N treatments was 2.24 ± 0.17, 1.80 ± 0.23, and 1.15 ± 0.25 mm (ANOVA: P < .01). The significantly greater growth of A. validus at subnormal densities in the experimental channels suggested that the A. validus population in Barnwell Creek was food—limited.},

keywords = {algae, Ameletus, assemblage structure, competition, diatoms, grazing, indirect effects, mayfly, periphyton, standing crop, streams},

pubstate = {published},

tppubtype = {article}

}