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  • 1
    Electronic Resource
    Electronic Resource
    ENVIRONMENTAL FACTORS INFLUENCING SUSPENDED SOLIDS IN THE LOXAIIATCHEE ESTUARY, FLORIDA (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 31 (1995), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : A study was initiated to examine the effects of wind speed, wind direction, freshwater inflow, and tide height on suspended solid concentration and distribution in the Loxahatchee estuary, Florida. Recent efforts to increase freshwater flows in this system raised concerns that suspended solid concentrations would increase as well, which might result in negative impacts for the estuary. The data indicated that total suspended solids (TSS) in the estuary are derived primarily from the inlet and not from freshwater tributaries. In addition, total suspended solids and volatile suspended solids were correlated strongly with salinity, suggesting that suspended sediments act conservatively throughout this system. No one environmental factor had an overwhelming influence on suspended solid concentration throughout the estuary; different regions of the estuary were influenced by different factors. Freshwater inflow was negatively related to TSS in the upper reaches of the estuary but was positively related to TSS in the central embayment region of the estuary. We attribute this latter finding to the fact that extremely high inflows both prevented the normal transport upstream of tidal borne suspended sediments and promoted mixing when the freshwater front moving downstream confronted the tidal front moving upstream. Wind speed, wind direction, and tide height had relatively small effects on TSS concentration but were most influential in reaches upstream of the central embayment, where tidal velocity begins to diminish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.1995.tb03360.x
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  • 2
    Electronic Resource
    Electronic Resource
    The influence of phosphorus enrichment on lotic bryophytes (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 31 (1994), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 〈list xml:id="l1" style="custom"〉1 Phosphorus enrichments of 5 weeks' duration were performed in two woodland streams in eastern Tennessee, U.S.A. to determine their effect on the dominant stream bryophyte, Porella pinnata.2 In a second-order reach of Walker Branch, which had an N:P ratio (by atoms) of 3.5:1 in the stream water, the P:C ratio of Porella was not significantly affected by enrichment, but the P:N ratio did increase significantly. In Sludge Creek, which had an N:P ratio of 21.6:1 in the stream water, both P:C and P:N ratios of Porella increased significantly following phosphorus addition. Increased phosphorus ratios may have resulted from either assimilation or adsorption.3 Absolute phosphorus concentrations in Porella tissue were significantly greater prior to enrichment in the control reach of Walker Branch, confounding the effect of phosphorus enrichment. In Sludge Creek, absolute phosphorus content in Porella tissue increased significantly in the treated reach and showed no significant difference in the control reach.4 Although mean primary production increased by approximately 15% following enrichment, the increase was not significantly different from that prior to enrichment.5 Epiphyte structure and abundance were not significantly influenced by enrichment in either stream. It is suggested that grazing pressure by snails may have masked any potential epiphyte response to enrichment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1994.tb00838.x
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  • 3
    Electronic Resource
    Electronic Resource
    Algal responses to experimental nutrient addition in the littoral community of a subtropical lake (1999)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 42 (1999), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. An in situ experiment was performed in the littoral zone of a large, subtropical lake to quantify effects of phosphorus (P) and nitrogen (N) on algal biomass, productivity, nutrient content and phosphate uptake kinetics.2. We hypothesized that resident periphyton rapidly sequester added nutrients from the water column, but once a certain threshold is reached, nutrients remain in the water and permit a shift to a phytoplankton-dominated community.3. Three duplicate sets of 1.2-m diameter mesocosms were treated with 10, 20 or 50 μg P L−−1 in combination with 100, 200 or 500 μg N L−−1, respectively. The nutrients were added thrice weekly for 14 days, after which the treatment doses were doubled for an additional 9 days. The cumulative amounts of P and N added over the course of the study were 700 and 7000 μg L−−1, respectively. Two untreated mesocosms and two open reference sites were used as controls.4. The total P concentration in the water column of nutrient-treated mesocosms remained low, even after prolonged high dosing. However, there was a two-fold increase in the P content of surface algal mats and epiphyton. This indicates that some of the added P was sequestered by those components of the community. In contrast, metaphyton and epipelon displayed little or no increase in their P content. Large quantities of added P could not be accounted for in the periphyton community, and may reflect unmeasured losses to the sediments or other pools.5. Nitrogen also was depleted from the water column, but there were no significant increases in periphyton N content. Much of the added N could not be accounted for in mass balances, and may have been lost from the mesocosms through volatilization or other biochemical processes.6. Chlorophyll-a in epiphyton increased significantly after 14 days in the highest nutrient treatment, where there also was a proliferation of Spirogyra on day 28.7. On day 28, water column samples from the highest nutrient treatment also displayed a significantly higher rate of carbon uptake, and a significantly higher concentration of midday dissolved oxygen.8. The hypothesis that phytoplankton become dominant at high nutrient loading rates was not supported. However, there were dramatic changes in community structure (increased dominance by epiphytic Spirogyra) and function (increased productivity and dissolved oxygen) in response to nutrient additions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.1999.444479.x
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  • 4
    Electronic Resource
    Electronic Resource
    Phosphorus kinetics of planktonic and benthic assemblages in a shallow subtropical lake (1998)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 40 (1998), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Phosphate uptake kinetics and uptake rates were calculated for planktonic (phytoplankton and bacterioplankton) and benthic (epiphyton and epipelon) assemblages in a large, shallow, subtropical lake. Samples were taken bimonthly over the period of 1 year at three different sites to examine spatial and temporal variability in these processes.2. Two of the sites, located at the edge of the littoral zone next to the open water (ecotone sites), had low irradiance at the sediment surface and high total phosphorus (TP) concentration (annual mean TP = 112 μg L–1). The third site, located in the littoral marsh zone, had high irradiance at the sediment surface and low TP concentration (annual mean TP = 7 μg L–1).3. Based on 32P-PO4 turnover time, P availability varied temporally and spatially. At the two high TP ecotone sites, P concentration was lowest in July and August. At the low TP marsh site, P limited algal production throughout the year.4. The quotient of maximum uptake rate to half saturation constant (Vm/Ks) in the plankton increased by over two orders of magnitude during the P-limited (summer) period at the two ecotone sites, suggesting that plankton used the scarce phosphorus more efficiently. The specific uptake rate of plankton was significantly greater than that of periphyton at all sites, suggesting that the plankton were more efficient than periphyton at taking up phosphate.5. Periphyton biomass, as well as absolute and percentage P uptake rate, was greater at the marsh site than at the ecotone sites, despite the lower P concentrations in the marsh. This was probably a result of rapid nutrient cycling, combined with high light availability in the marsh.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.1998.d01-660.x
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  • 5
    Electronic Resource
    Electronic Resource
    Recovery of lotic periphyton communities after disturbance (1990)
    Springer
    Environmental management 14 (1990), S. 589-604 
    Details
    ISSN: 1432-1009
    Keywords: Desiccation ; Disturbance ; Floods ; Periphyton ; Streams ; Succession ; Toxic pollutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Periphyton communities represent potentially excellent candidates for assessing the recovery of lotic ecosystems after disturbance. These communities are ubiquitous, relatively easy to sample and measure (in terms of total community biomass), have short generation times, and may influence the recovery rates of higher trophic levels. The first section of this article analyzes how site availability, species availability, and differential species performance influence periphyton successional dynamics. This background information provides a foundation for understanding how periphytic organisms respond after a disturbance. The second section of this article analyzes how periphyton communities respond to four different types of disturbance (flood events, desiccation, organic nutrient enrichment, and toxic metal exposure). Although data are limited, it is concluded that the fast growth rates and short generation times of periphytic organisms, coupled with their flexible life history strategies and good dispersal ability, allow lotic periphyton communities to recover relatively quickly after a disturbance. In addition, disturbance type and severity, local environmental conditions, and site-specific factors also will influence recovery rates. Future research needs include a better understanding of: (1) what periphyton property(ies) would serve as the best index of recovery; (2) whether or not the robustness of this index varies among different environments and different disturbances; (3) interactions between autotrophs and heterotrophs within the periphyton mat, particularly with respect to nutrient cycling; (4) competitive interactions among organisms; (5) functional redundancy of organisms; and (6) the influence of the riparian zone and channel geomorphology on periphyton recovery rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02394711
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  • 6
    Electronic Resource
    Electronic Resource
    Comparative analysis of Lake Periphyton communities using high performance liquid chromatography (HPLC) and light microscope counts (1999)
    Springer
    Aquatic sciences 61 (1999), S. 307-322 
    Details
    ISSN: 1420-9055
    Keywords: Key words: Periphyton, pigment analysis, HPLC, light microscopy.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract: High performance liquid chromatography (HPLC) and light microscope counts were used to characterize the taxonomic composition of epiphyton and epipelon at seven locations in a subtropical lake. Both methods indicated that algae were dominated by diatoms and cyanobacteria. However, the methods often gave dramatically different estimates of relative biomass among algal divisions, and there was no consistent pattern of co-variation. Large differences in underwater irradiance may have caused variation in accessory pigment to chlorophyll a ratios, invalidating application of the generic HPLC-based model. In large heterogeneous lakes, it may be necessary to use a suite of models, tailored to site-specific environmental conditions, if HPLC is to be used for evaluation of algal community structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000270050068
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  • 7
    Electronic Resource
    Electronic Resource
    Does an increase in irradiance influence periphyton in a heavily-grazed woodland stream? (1992)
    Springer
    Oecologia 91 (1992), S. 163-170 
    Details
    ISSN: 1432-1939
    Keywords: Herbivory ; Light limitation ; Periphyton ; Snails ; Streams
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Irradiance level and grazer density were manipulated in a factorial design to examine the relative effects of biotic and abiotic factors on periphyton biomass, productivity, and taxonomic structure in a heavily grazed, woodland stream. Irradiance levels were increased from 0.26 to 12.42 mol quanta/m2/d by placing metal halide lamps over the stream. The major grazer in this system was the prosobranch snail Elimia clavaeformis. Its densities were reduced from ca. 750 individuals/m2 to near zero by raising platforms off the stream bottom. Experimental treatments were maintained for 48 days. Biomass-specific carbon fixation rates increased significantly in response to higher light levels, indicating that periphyton communities were light-limited at this time of year. However, positive effects of irradiance on areal-specific carbon fixation and biomass were detected only when grazer density was reduced. Basal cells of the chlorophyte Stigeoclonium dominated communities exposed either to low light or high grazing pressure. When light was increased and grazer density reduced, large or upright diatoms became more abundant. Results from this study indicated that limitation of periphyton photosynthesis could be mitigated by increasing the levels of an abiotic resource (light) to this system, but that periphyton biomass was controlled by biotic interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317779
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of grazer type and abundance on plant-herbivore interactions in streams (1995)
    Springer
    Hydrobiologia 306 (1995), S. 179-188 
    Details
    ISSN: 1573-5117
    Keywords: herbivory ; laboratory streams ; periphyton ; feeding ; macroinvertebrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Grazer-periphyton interactions were investigated in 11 laboratory streams holding a range of densities of three herbivore taxa during a 32-d experiment. Effects of grazers on algae were strongest with Dicosmoecus gilvipes caddisflies, intermediate with Juga silicula snails, and weakest with Baetis spp. mayflies. Algal standing crop, export, and gross primary production declined logarithmically with increasing grazer density. Algal turnover rate, however, increased with grazer abundance. At high densities of all grazers, responses in most algal parameters converged, suggesting that high grazing pressure, regardless of taxon, will similarly affect periphyton. Growth of both Dicosmoecus caddisflies and Juga snails was density-dependent, with the highest growth rates occurring at the lowest densities. Caddisflies displayed high growth rates but low efficiency in resource use. Snails had lower growth rates but were more efficient in resource use. The coexistence of Dicosmoecus and Juga, or other competing herbivores, in natural streams may be related to these fundamental differences in life history strategies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017689
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  • 9
    Electronic Resource
    Electronic Resource
    Characteristics of softwater streams in Rhode Island. III. Distribution of macrophytic vegetation in a small drainage basin (1986)
    Springer
    Hydrobiologia 140 (1986), S. 183-191 
    Details
    ISSN: 1573-5117
    Keywords: Rhode Island ; streams ; macrophytes ; macroalgae ; watershed ; drainage ; basin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Wood River watershed, a small well-defined drainage basin in Rhode Island was monitored seasonally for all macrophytic vegetation and various physical variables. Twenty-four segments, 20 m in length were sampled. Mean stream depth, width and current velocity increased by 3 to 8 fold from 1st- to 4th-order segments. Light penetration was positively correlated with the above variables (p 〈 0.05) and increased by 11 fold from the headwaters to the mouth during September when the riparian canopy was maximum. 74 subgeneric taxa of macrophytes were collected in the Wood River basin, 36% algae, 13% bryophytes, 4% vascular cryptograms and 45% angiosperms. The highest diversity occurred in the 4th-order segments throughout the year. Species numbers were positively correlated with depth, width and light penetration (p 〈 0.05). Vascular plants dominated all orders, but their proportion doubled from 1st- to 4th-order streams. Macrophyte cover was twice as high in the 4th-order segments in June and September as in the other orders. Macrophyte abundance was positively correlated to light penetration and negatively correlated to the ratio of nonvascular: vascular plants (p 〈 0.05). Two distinct clusters were found for the predominant species. The first cluster contained mostly large angiosperms, which were rooted in sediments, while the second cluster was composed of small epilithic algae and bryophytes. The moss, Fontinalis antipyretica, was the most frequent species, occurring in 51% of the samples and in all 4 orders throughout the year.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007573
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  • 10
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    Rating impacts in a multi-stressor world: a quantitative assessment of 50 stressors affecting the Great Lakes (2014)
    Wiley-Blackwell
    Details
    Publication Date: 2014-09-08
    Description: Ecosystems often experience multiple environmental stressors simultaneously that differ widely in their pathways and strengths of impact. Differences in relative impact can guide restoration and management prioritization, but few studies have empirically assessed a comprehensive suite of stressors acting on a given ecosystem. To fill this gap in the Laurentian Great Lakes, where considerable restoration investments are currently underway, we used expert elicitation via a detailed online survey to develop ratings of the relative impacts of 50 potential stressors. Highlighting the multiplicity of stressors in this system, experts assessed all 50 stressors to have some impact on ecosystem condition, but ratings differed greatly among stressors. Individual stressors related to invasive and nuisance species (e.g., dreissenid mussels and ballast invasion risk) and climate change were assessed as having the greatest potential impacts. These results mark a shift away from the longstanding emphasis on nonpoint phosphorus and persistent bioaccumulative toxic substances in the Great Lakes. Differences in impact ratings among lakes and ecosystem zones were weak, and experts exhibited surprisingly high levels of agreement on the relative impacts of most stressors. Our results provide a basin-wide, quantitative summary of expert opinion on the present-day influence of all major Great Lakes stressors. The resulting ratings can facilitate prioritizing stressors to achieve management objectives in a given location, as well as providing a baseline for future stressor impact assessments in the Great Lakes and elsewhere. # doi:10.1890/14-0366.1
    Print ISSN: 1051-0761
    Electronic ISSN: 1939-5582
    Topics: Biology
    Published by Wiley-Blackwell on behalf of The Ecological Society of America (ESA).
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