Decreased Light Penetration Research Articles

Cereal Rye Cover Crop Termination Management for Palmer Amaranth (Amaranthus palmeri) Suppression in Soybean

Abstract Palmer amaranth is a troublesome weed species displaying the ability to adapt and evolve resistance to multiple herbicide modes of action, and there is a need for additional weed suppression tactics. Growing interest in the use of cover crops (CC) has led to questions regarding the most appropriate forms of CC management prior to cash crop planting in order to maximize weed suppression benefits. Experiments were conducted between 2021 to 2023 to test: 1) cover crop termination timing (i.e., green or brown), 2) CC biomass amount and 3) CC termination method (i.e., rolled or left standing) on Palmer amaranth suppression. Treatments included “planting brown” (cereal rye terminated two weeks before soybean planting), “planting green” (cereal rye terminated at soybean planting), and a no CC (winter fallow) check. Palmer amaranth emergence was evaluated at 4 and 6 weeks after soybean planting, and yield was calculated at harvest. CC reduced Palmer amaranth emergence when compared to the no CC check, and more suppression was observed as CC biomass increased. This decrease in emergence is potentially due to a decrease in light penetration reaching the soil surface and physical suppression as CC biomass increased. Yield, however, was unaffected by any CC management practice, indicating that growers can tailor CC termination practices for weed suppression. This information will provide better recommendations for farmers interested in using cover crops for weed suppression. Overall, the importance of CC biomass accumulation to achieve weed suppression is highlighted in our findings. Additionally, we add to the growing body of documentation that soybean yield may be variable from year to year as a result of CC presence.

Potential gap in understanding cyanoHABs: Light-dependent morphological variations in colonial cyanobacterium Microcystis

Colony formation is a crucial characteristic of Microcystis, a cyanobacterium known for causing cyanobacterial harmful algal blooms (cyanoHABs). It has been observed that as Microcystis colonies grow larger, they often become less densely packed, which correlates with a decrease in light penetration. The objective of this study was to investigate the effects of light limitation on the morphological variations in Microcystis, particularly in relation to the crowded cellular environment. The results indicated that when there was sufficient light (transmittance = 100 %) to support a growth rate of 0.11±0.01 day−1, a significant increase in colony size was found, from 466±15 μm to 1030±111 μm. However, under light limitation (transmittance = 50 % – 1 %) where the growth rate was lower than 0, there was no significant improvement in colony size. Microcystis in the light limitation groups exhibited a loose cell arrangement and even the presence of holes or pores within the colony, confirming the negative correlation between colony size and cell arrangement. This pattern is driven by regional differences in growth within the colony, as internal cells have a significantly lower frequency of division compared to peripheral cells, due to intra-colony self-shading (ICSS). The research demonstrates that Microcystis can adjust its cell arrangement to avoid excessive self-shading, which has implications for predicting and controlling cyanoHABs. These findings also contribute to the understanding of cyanobacterial variations and can potentially inform future research on the diverse phycosphere.

Mathematical Isothermal Modeling of Remazol Black B Biosorption by Aspergillus flavus

Azo dyes, like Remazol Black B, form covalent bonds with textile fibers like cotton, setting them apart from traditional dyes. Due to their advantageous qualities of vivid color, water resistance, straightforward application processes, and low energy consumption, they are widely used in the textile industry. Major environmental effects of their discharge into receiving streams include reduced photosynthesis in aquatic life as a result of decreased light penetration. Seven isotherm models—Henry, Langmuir, Freundlich, BET, Toth, Fritz-Schlunder IV, and Fritz-Schlunder V—were used to analyze the biosorption isotherm data of Remazol Black B dye biosorption by Aspergillus flavus and were fitted using non-linear regression. Based on statistical analysis, the Fritz-Schlunder IV was determined to be the best model using root-mean-square error (RMSE), adjusted coefficient of determination (adjR2), bias factor (BF), accuracy factor (AF), corrected AICc (Akaike Information Criterion), Bayesian Information Criterion (BIC), and Hannan-Quinn information criterion (HQC). The calculated Fritz-Schlunder IV parameter, bFS value was found to be 3.812 mg/g (95% confidence interval of 0.312 to 7.311) and qmFS value of 0.0224 (95% confidence interval of -21725.002 to 21725.047).

Influence of glacial turbidity and climate on diatom communities in two Fjord Lakes (British Columbia, Canada)

Inputs of glacial meltwater and changes in climate can profoundly influence lake ecosystems. Anderson and Seton lakes, two morphologically and chemically similar fjord lakes within the Fraser River Basin, British Columbia, experience a common biogeoclimatic setting, yet contrasting turbid-water influences from a hydroelectric development which diverts glacially-turbid water into Seton Lake, but not Anderson Lake. We conducted a comparative paleolimnological study of these two lakes to infer climatic and hydro-system influences affecting the freshwater algal community over the past ~ 200 years. Paleolimnological analysis of multiple cores for sedimentary diatom assemblages from Seton Lake revealed substantial diversion-related reductions in diatom concentrations and fluxes following the completion of the Bridge River Diversion (ca. 1950). Diatom compositional changes in Seton Lake were consistent with decreased light penetration due to increased turbidity. These changes did not occur in Anderson Lake, indicating the changes in the Seton Lake cores were likely driven by inflow of the glacially-turbid waters. Both lakes exhibited diatom compositional changes ca. 1980, with a rise in Lindavia comensis coincident with significant increases in local mean annual air temperatures and presumably associated limnological changes. Modern phytoplankton data, collected as part of this study, provides support for the occurrence of different L. comensis morphs throughout the sampling period (May–October) in Anderson Lake and in the fall in Seton Lake. The rise of L. comensis in both Anderson and Seton lakes is conceivably linked to the recent ice-free conditions enabling this taxon to persist throughout the year.

Capillary microphotoreactor packed with TiO2-coated glass beads: An efficient tool for photocatalytic reaction

A novel capillary microphotoreactor (MPR) packed with TiO2-coated glass beads was developed in this work and its photocatalytic performance was evaluated using degradation of methylene blue (MB) as a model reaction. As compared to conventional wall-coated MPR, the use of glass beads as packing material not only provides a larger surface area for catalyst immobilization and shortens the mass transfer route, but also introduces flow perturbation. An appropriate size of glass beads should be chosen for packing because there is a tradeoff between increased catalysts coating area and decreased light penetration. It was found out that nearly 100 % degradation efficiency could be achieved in 80# glass beads packed MPR within short residence time (20 s), which was more than 2 orders of magnitude larger than value obtained in wall-coated MPR under the same operational conditions. Moreover, the packed MPR showed good durability, which declined by about 17 % after 6 h of operation and then remained stable for next 19.5 h.

THE IMPACT OF LIGHT PENETRATION INTO CANOPY AND SEASONALITY ON PHOTOSYNTHETIC INDICES IN APPLE TREE LEAVES

The aim of this study was to analyse the impact of light penetration into canopy and the effect of distances between technological tools and seasonality on photosynthetic behaviour. Apple tree cultivar ‘Auksis’ was grafted onto superdwarfing rootstock P22 and planted at different distances (from 0,25 m to 1 m in rows, while space between rows was 3 m). Photochemical reflectance and plant senescence reflectance indices were measured at two heights: 1.0 – 1.2 m above ground and 1.8 – 2.0 m above ground; specific leaf area, fresh and dry weight were evaluated from all the canopy. Strong positive correlations were determined between photochemical reflectance index and plant senescence reflectance index in higher and lower levels of the canopy. Strong negative correlations were determined between photochemical reflectance index and plant senescence reflectance index and between specific leaf area and dry and fresh mass ratio. Increasing density between apple trees from 1 m to 0.5 m led to increase in photochemical reflectance index and specific leaf area, but plant senescence reflectance index decreased. Meanwhile, seasonality had significant impact on specific leaf area formation and dry to fresh weight ratio. Dry and fresh weight ratio increased by 5% in autumn compared to summer. Our results indicated that with decreased light penetration into canopy photochemical reflectance index decreased, but plant senescence reflectance index increased. Moreover, in autumn, trees prepare for winter by storing more nutrients and leaves accumulate more dry mass.

Invasive shrubs modify rodent activity timing, revealing a consistent behavioral rule governing diel activity

Abstract Animals adjust the timing of their activity to maximize benefits, such as access to resources, and minimize costs, such as exposure to predators. Despite many examples of invasive plants changing animal behavior, the potential for invasive plants to alter the timing of animal activity remains unexplored. In eastern North America, invasive shrubs might have particularly strong effects on animal activity timing during spring and fall, when many invasive shrubs retain their leaves long after native species’ leaves senesce. We experimentally removed an invasive shrub (buckthorn, Rhamnus cathartica) and monitored the activity timing of a ubiquitous small-mammal species (white-footed mouse, Peromyscus leucopus) in spring, summer, and fall. We captured nearly 3 times as many P. leucopus in plots invaded by R. cathartica compared with plots with R. cathartica removed, and P. leucopus were captured 2 h earlier in invaded plots. Regardless of invasion treatment, P. leucopus appear to follow a common rule to set activity timing: P. leucopus were only active below a threshold of ground-level moonlight illuminance (0.038 lux). Diel and monthly lunar cycles play an important role in regulating small-mammal activity, but our data suggest that decreased light penetration dampens the influence of moonlight illuminance in habitats invaded by R. cathartica, allowing P. leucopus to remain active throughout the night. By changing the temporal niche of ubiquitous native animals, invasive shrubs may have unappreciated effects on many ecological interactions, including processes that alter community diversity and affect human health.

Genomes of Novel Microbial Lineages Assembled from the Sub-Ice Waters of Lake Baikal.

We present a metagenomic study of Lake Baikal (East Siberia). Two samples obtained from the water column under the ice cover (5 and 20 m deep) in March 2016 have been deep sequenced and the reads assembled to generate metagenome-assembled genomes (MAGs) that are representative of the microbes living in this special environment. Compared with freshwater bodies studied around the world, Lake Baikal had an unusually high fraction of Verrucomicrobia Other groups, such as Actinobacteria and Proteobacteria, were in proportions similar to those found in other lakes. The genomes (and probably cells) tended to be small, presumably reflecting the extremely oligotrophic and cold prevalent conditions. Baikal microbes are novel lineages recruiting very little from other water bodies and are distantly related to other freshwater microbes. Despite their novelty, they showed the closest relationship to genomes discovered by similar approaches from other freshwater lakes and reservoirs. Some of them were particularly similar to MAGs from the Baltic Sea, which, although it is brackish, connected to the ocean, and much more eutrophic, has similar climatological conditions. Many of the microbes contained rhodopsin genes, indicating that, in spite of the decreased light penetration allowed by the thick ice/snow cover, photoheterotrophy could be widespread in the water column, either because enough light penetrates or because the microbes are already adapted to the summer ice-less conditions. We have found a freshwater SAR11 subtype I/II representative showing striking synteny with Pelagibacterubique strains, as well as a phage infecting the widespread freshwater bacterium PolynucleobacterIMPORTANCE Despite the increasing number of metagenomic studies on different freshwater bodies, there is still a missing component in oligotrophic cold lakes suffering from long seasonal frozen cycles. Here, we describe microbial genomes from metagenomic assemblies that appear in the upper water column of Lake Baikal, the largest and deepest freshwater body on Earth. This lake is frozen from January to May, which generates conditions that include an inverted temperature gradient (colder up), decrease in light penetration due to ice, and, especially, snow cover, and oligotrophic conditions more similar to the open-ocean and high-altitude lakes than to other freshwater or brackish systems. As could be expected, most reconstructed genomes are novel lineages distantly related to others in cold environments, like the Baltic Sea and other freshwater lakes. Among them, there was a broad set of streamlined microbes with small genomes/intergenic spacers, including a new nonmarine Pelagibacter-like (subtype I/II) genome.

Eelgrass Bed Structure, Leaf Nutrient, and Leaf Isotope Responses to Natural and Anthropogenic Gradients in Estuaries of the Southern Gulf of St. Lawrence, Canada

Seagrasses are declining globally; understanding and monitoring these trends forms an important basis for management practices. This study examined eelgrass (Zostera marina) structural and isotopic indicators as a means of characterizing stress from the impacts of agricultural land use in four estuaries in the Southern Gulf of St. Lawrence, Canada. These estuaries ranged from 5 to 62% agricultural land use in their respective watersheds. Anthropogenic stressors such as increased nutrient loading and decreased light penetration (from sedimentation and phytoplankton) and natural stressors such as low salinity and temperature were measured concurrently with plant structural indicators, e.g., aboveground biomass, belowground biomass, canopy height, and root-to-shoot ratio, across the spatial range of eelgrass presence in each estuary. Plant isotopic indicators included leaf tissue concentrations of C, N, S, and stable isotopes thereof and were measured at each station in eelgrass leaf tissue. Eelgrass plant indicators varied significantly across the gradients within each estuary as well as throughout the growing season, but due to the very high within-estuary variability indicators did not vary significantly between estuaries. Eelgrass leaf nutrients and stable isotopes also varied significantly between stations within estuaries though in this case, among-estuary differences were detected. A distance-based linear model was employed to examine the ability of estuarine characteristics and plant isotopic and elemental variables to predict the plant structural indicators. Results showed that factors related to both salinity and nitrogen loading influenced the biomass and structure of this plant but in different ways. Belowground biomass most correlated to salinity, and aboveground biomass most related to nitrogen loading with a strong relationship with light attenuation. Overall, the high level of within-estuary variability, and the strong influence of salinity, suggests that comparison of plant structural indicators between estuaries may have limited utility as a monitoring tool; eelgrass coverage throughout an estuary may better reflect the influence of land use at a regional scale.

Macrobenthic assemblages in an artificial reef in central-west Portugal: Preliminary results

Macrobenthic assemblages in an artificial reef in central-west Portugal: Preliminary results

Enhancement of glycerol metabolism in the oleaginous marine diatom Fistulifera solaris JPCC DA0580 to improve triacylglycerol productivity.

BackgroundMicroalgal oil is a promising alternative feedstock for biodiesel fuel (BDF). Mixotrophic cultivation with glycerol, the primary byproduct of BDF production, may be used to optimize BDF production. This strategy would reduce costs through glycerol recycling and improve lipid productivity and biomass productivity by overcoming the growth retardation caused by decreased light penetration in high-density culture.ResultsOverexpression of the endogenous glycerol kinase (GK) gene in an oleaginous marine diatom, Fistulifera solaris JPCC DA0580, accelerates glycerol metabolism and improves lipid and biomass productivities. Two candidates were selected from a collection of 90 G418-resistant clones, based on growth and confirmation of genome integration. GK gene expression was higher in the selected clones (GK1_7 and GK2_16) than in the wild-type culture. The GK2_16 clone achieved a 12% increase in lipid productivity.ConclusionWe have demonstrated the potential of metabolic engineering in oleaginous microalgae to improve lipid productivity. Metabolic engineering techniques can be used to optimize BDF production.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-014-0184-9) contains supplementary material, which is available to authorized users.

Escaped Miscanthus sacchariflorus reduces the richness and diversity of vegetation and the soil seed bank

Prioritizing management efforts and funds for invasive species relies upon knowledge of their ecological impacts. Often, however, novel species have unknown effects and can exhibit long time lags before proliferating, making early management decisions difficult. The grasses Miscanthus sinensis, M. sacchariflorus, and their sterile hybrid M. × giganteus have been introduced to North America and elsewhere for horticultural and agricultural purposes, but little is known about their impacts on resident vegetation upon escape from cultivation. We compared the vegetation communities and soil seed bank of paired areas invaded and uninvaded by escaped M. sacchariflorus at ten sites in Ontario, Canada. Invaded plots had very few species other than M. sacchariflorus and had lower plant species abundance, richness, and diversity than did uninvaded plots, and effects were greater on the vegetation than on the seed bank. Invaded plots also had more live and dead standing biomass, taller vegetation, and greater litter biomass, along with decreased light penetration to the soil surface than in uninvaded plots. However, M. sacchariflorus did not produce a germinable seed bank. Our results suggest that the regional spread of M. sacchariflorus is currently limited by a lack of seed production/viability, but its occurrence along disturbance-prone roadways and drainages facilitates its local vegetative spread. The strong negative effects of M. sacchariflorus on the resident plant community should be considered in risk assessments and management planning for this and other Miscanthus species.

A chemical approach for the mitigation of Prymnesium parvum blooms

Known as Golden Algae in popular media, the harmful algal bloom causing organism Prymnesium parvum secretes increased amounts of toxic chemicals called prymnesins when stressed, resulting in major fish kills in Texas. Although many options exist for mitigation of blooms, a feasible protocol for control of blooms on large-scale impoundments has yet to be identified. Chemical control of P. parvum using six different enzyme inhibiting aquatic herbicides was explored in laboratory experiments. Of the six chemicals screened, one (flumioxazin) was selected for further study due to a significant decrease in P. parvum cell numbers with increasing chemical concentration. It was applied to natural plankton communities during in-situ experiments (Lake Granbury, Texas). The first experiment was conducted during a period of P. parvum bloom initiation (March) and the second experiment conducted during a post bloom period (April). Experiments were carried out in 20 L polycarbonate carboys covered in 30% shade cloth to simulate natural light, temperature and turbulence conditions. Through cell counts via light-microscopy, the chemical flumioxazin was found to cause significant decreases in P. parvum, but no significant differences in zooplankton abundance during the period of bloom initiation. However, significant decreases in adult copepods were observed during the post bloom period, with no significant decreases in P. parvum most likely due to decreased light penetration and inhibition of the photosensitive mode of action.

Modeling suspended solids in a Northern Chilean Patagonia glacier-fed fjord: GLOF scenarios under climate change conditions

Suspended solids play an ecologically important role in glacier-fed fjords, given its dominant effect on their primary production arising from the generation of turbid water plumes by retreating glaciers, which increase light attenuation. Glacial-lake outburst floods, GLOFs, are sudden releases of lake-water impounded by a glacier which may affect either locally or regionally depending on the amount of water and suspended solids released. Chilean Patagonia has been characterized by some of the fastest glacial retreats worldwide and by an increase in GLOFs events. In this article we describe the development of a hydrodynamic model to study the distribution of suspended solids in the Baker channel, a glacier-fed fjord located in Northern Chilean Patagonia. We further describe the simulation of three climate change induced GLOF scenarios and discuss their potential effects on fjord's primary production. The model was implemented as a two-level, one-way, nested hierarchy using the MOHID water modeling system. The large extent, oceanic, level corresponded to a one-layer barotropic model, while the smaller extent, fjord, level corresponded to a 3D baroclinic model with 31 Cartesian layers. Velocities, salinity and suspended solids concentrations were calibrated using field measurements. Results show that the most likely scenario is a decrease in light penetration within the inner fjord's area. Only the most catastrophic scenario, equivalent to a large recorded paleo-discharge, would affect outer areas of the Northern Chilean fjords.

Variability of protistan and bacterial communities in two Arctic fjords (Spitsbergen)

Krossfjorden and Kongsfjorden are Arctic fjords on the western side of Spitsbergen. These fjords share a common mouth to the open sea, and both are influenced by the input of sediment-rich glacial meltwater leading to decreased surface salinity, increased turbidity and decreased light penetration during summer. Earlier classical taxonomic studies had described the pelagic protistan composition of the Kongsfjorden during summer, revealing the dominance of flagellates of often unresolved taxonomic origin. Only little information existed on microbial eukaryote composition of the Krossfjorden as well as the bacterial composition of both fjords. The aim of the present study was to analyze and compare surface summertime protistan and bacterial communities in both fjords, using molecular approaches (16S and 18S rRNA DGGE, sequencing). Samples were collected three times a week from the central Kongsfjorden over a 1-month period. Additionally, 10 marine and 2 freshwater sites were sampled within a 1-week period in both Kongsfjorden and Krossfjorden. The central Kongsfjorden revealed a relatively stable protistan community over time with dinoflagellates, chlorophytes and small heterotrophs dominating. In contrast, the bacterial community varied over time and appeared to be correlated with the inflow of glacial meltwater. The Kongsfjorden and Krossfjorden were found to harbor distinctive bacterial and eukaryotic communities. We speculate that differences in glacial meltwater composition and fjord bathymetry affect the surface water properties and therefore the observed spatial variability in the community fingerprints.

Variation in brachiopod preservation along a carbonate shelf-basin transect (Red Sea and Gulf of Aden): Environmental sensitivity of taphofacies

A bathymetric transect ranging from coral habitats down to a 1500-m-deep basin in the Red Sea and Gulf of Aden allows us to test the sensitivity of taphofacies to depth and sediment grain size in a tropical to subtropical carbonate basin, to partition variation in brachiopod preservation into extrinsic (environmental) and intrinsic (shell-specific) components, and to quantify residual variation that remains unexplained by such components. Factoring out environmental effects, thin-shelled, organic-poor rhynchonellids are more affected by fragmentation and fine-scale surface alteration and degrade rapidly compared to the more frequently bioeroded, organic-rich terebratulids. The negative role of shell organic content is overridden by shell thickness, and preservation rates of organic-rich brachiopods are enhanced by syndepositional cement precipitation. Environmental trends in preservation are confounded by shell-specific factors that account for 16% of variation in preservation: the amounts of multivariate variation explained by environment increase from 29% using combined brachiopod preservation to 46% using terebratulid preservation. Environmental sensitivity of taphofacies is driven by present-day variation in environment but also by past Pleistocene conditions. First, reduction in fragmentation, encrustation, and bioerosion is consistent with a decrease in light penetration and primary productivity. Second, brachiopods are coated with aragonite cement in basinal sites with lithified oozes and microbial carbonates that originated during the last glacial maximum when syndepositional aragonite cementation was favored by high temperature and salinity, and thus can be affected by millennial-scale time averaging. Skeletal preservation rates are thus not in steady state over the duration of time averaging, and the bathymetric reduction in alteration is partly related to past conditions amenable to cement precipitation.

Field assessment of oxytetracycline exposure to the freshwater macrophytes Egeria densa Planch. and Ceratophyllum demersum L.

In a microcosm study, two aquatic macrophytes, Egeria densa and Ceratophyllum demersum were exposed to nominal concentrations of 0, 5, 20, 50, and 250 μg/L oxytetracycline ( n = 3), plus 20 μg/L oxytetracycline amended with additional nitrogen (N) and phosphorus (P). Responses were monitored bi-weekly over a six-week exposure period. Both plant species exhibited a significant decline in growth in the 250 μg/L oxytetracycline and the N- and P-amended units. Decreased light penetration resulting from accumulating oxytetracycline by-products appears to be the primary modifier in the growth of these plants. Increased susceptibility to oxytetracycline exposure was noted in some paired plantings (e.g., E. densa root development), relative to individual plants in these treatments, however, no clear explanation for this response is available. Based on the toxicity data generated in this study, we estimate that current concentrations of oxytetracycline in freshwater environments do not pose a direct risk to E. densa and C. demersum.

Agrochemical and nutrient impacts on estuaries and other aquatic systems.

This paper summarizes the "Agrochemical and Nutrient Impacts on Estuaries" symposium held at the 220th National Meeting of the American Chemical Society. The focus of the symposium was to highlight ongoing research efforts to understand estuarine function and pollutant fate in these important ecosystems. Expanding urbanization and agricultural activity can result in increased particulate and chemical loads, resulting in decreased light penetration and degraded aquatic habitats. Legislative and regulatory protections, such as the Clean Water Act and Total Maximum Daily Loads (TMDLs), are considered here. Measurement of nutrient and pesticide loads and their ecotoxicological impacts are explored, as well as potential mitigation practices. The complexity and high visibility of estuarine ecosystem health will require continued examination to develop more effective agricultural and land management strategies and sound science-based regulations.

Methods for research on immune complement activation on modified sensor surfaces

We have developed a methodological system consisting of a new surface sensitive quartz crystal microbalance with dissipation monitoring (QCM-D) sensor surfaces together with different surface modification methods for the investigation of surface associated complement activation in human sera. The QCM-D surface, 10 mm in diameter, was modified by spin-coating of poly(urethane urea) (PUUR) and polystyrene (PS). Some sensor surfaces were also sputtered with titanium (Ti) or modified by hydrophobic self-assembled monolayer (SAM) of an 18-carbon alkane thiol with a CH 3 end group. The amount of surface deposited complement protein was investigated by incubation of the modified sensor surfaces in human sera, followed by incubation with antibodies directed against complement factor 3c (C3c). The amounts of bound anti-C3c were then used as an arbitrary measure of surface induced complement activation. The order of complement activation of the different surfaces, as judged by three separate measurements per surface modification, was PUUR>PS=SAM>Ti. The Ti surface had a similar low degree of anti-C3c binding as the negative controls (heat inactivated sera). The novel QCM-D methodology was found to be very simple, accurate, sensitive and well suited as a screening method for complement activation and protein adsorption on different materials. We also compared the sensitivity of QCM-D method with surface plasmon resonance (SPR) for the quantification of protein adsorption and complement activation on gold sensor surfaces. The QCM-D method was equally sensitive as the SPR for the detection of protein adsorption from a solution independently if low flow rate (5 μl/min) was used. A slight increase in sensitivity was found at higher flow rate (30 μl/min). However, we found it difficult to use the SPR method on the Ti, PS and PUUR surfaces due to decreased light penetration of the modified SPR sensor chip.

Effect of inorganic sediment on whole-stream productivity

Sediment from agricultural, logging, and mining activities impairs more miles of rivers and streams in the United States than any other type of pollutant, including bacteria, nutrients, oxygen-depleting substances, and metals. However, specific impacts of sediment to streams have not been well studied or understood. To study the effect of inorganic sediment on plant and animal communities in stream ecosystems, we added clay to outdoor experimental streams 520 m long and 3.5 m wide at the Monticello Ecological Research Station (MERS). The streams take water from the Mississippi River and are designed to represent higher order streams in the upper midwestern United States. The sediment loading rates were 300, 200, 100, and 50 mg l−1. Our first dosing period (mid-August to November 1994) began at the start of a fall bloom in autotroph productivity, and the second (May to August 1995) began before the summer communities were established. During both treatment seasons, the addition of clay significantly increased turbidity and sedimentation, and decreased light penetration in treated streams corresponding roughly to 30–35, 25–30, 15–20, and 5–10 NTU, respectively. In general, the macrophyte and periphyton communities responded quickly after only a few weeks exposure to the sediment additions. Whole-stream respiration was significantly lower in treated streams, decreasing as the amount of sediment added increased. Periphyton biomass (chl a) on tiles and percent cover of macrophytes was significantly lower in treatment streams than in controls. In contrast to expectations and previous findings in two sets of field streams, total whole-stream productivity in the MERS streams was not significantly lower in streams receiving sediment loads than in control streams because the overall photosynthetic efficiency by the plant community compensated for the loss in irradiance.