scholarly journals Light attenuation by periphyton on Vallisneria americana

2020 ◽  
Vol 116 ◽  
pp. 106498 ◽  
Author(s):  
Jing Guan ◽  
Charles A. Jacoby ◽  
Thomas K. Frazer
Keyword(s):  
Light Attenuation ◽  
Vallisneria Americana

Domain shifts in the aquatic vegetation of shallow urban lakes: the relative roles of low light and anoxia in the catastrophic loss of the submerged angiosperm Vallisneria americana

2004 ◽  
Vol 55 (8) ◽  
pp. 749 ◽  
Author(s):  
Kay Morris ◽  
Katherine A. Harrison ◽  
Paul C. E. Bailey ◽  
Paul I. Boon
Keyword(s):  
Dissolved Oxygen ◽  
Aquatic Vegetation ◽  
Plant Biomass ◽  
Light Attenuation ◽  
Field Trials ◽  
Vallisneria Americana ◽  
Low Light ◽  
Shade Cloth ◽  
Eastern Australia ◽  
Catastrophic Loss

The catastrophic loss of Vallisneria americana from a shallow urban lake in south-eastern Australia following nutrient enrichment has been reported previously. Two experiments are reported here to determine whether light attenuation or shifts in dissolved oxygen were more important in mediating this loss of submerged plants. The first experiment tested the response of dense beds of Vallisneria to different levels of shade in the field. The second tested the effect of (i) shading and (ii) anoxia on the performance of Vallisneria grown in the glasshouse. In the field, plants persisted after 3 months beneath 100% shade cloth, although with significantly reduced biomass (63%). In contrast, plant biomass beneath 70% shade cloth was reduced by only 9%. The field trials indicate that Vallisneria is highly tolerant to severe light attenuation. In the glasshouse, microcosms that were not artificially aerated become anoxic, and all plants died within 24 days in two of the three replicate microcosms. In shaded microcosms that were artificially aerated, plant biomass was reduced by 48% but no plants died. Severe reductions in dissolved oxygen associated with shading were primarily responsible for the rapid loss of Vallisneria, rather than light attenuation alone was concluded from the current study.

Predicting cold-water bleaching in corals: role of temperature, and potential integration of light exposure

2020 ◽  
Vol 642 ◽  
pp. 133-146
Author(s):  
PC González-Espinosa ◽  
SD Donner
Keyword(s):  
Coral Bleaching ◽  
Cold Water ◽  
Light Exposure ◽  
Light Attenuation ◽  
Florida Keys ◽  
Cold Temperature ◽  
Warm Water ◽  
Coral Tissue ◽  
Effect Of Temperature ◽  
Type I

Warm-water growth and survival of corals are constrained by a set of environmental conditions such as temperature, light, nutrient levels and salinity. Water temperatures of 1 to 2°C above the usual summer maximum can trigger a phenomenon known as coral bleaching, whereby disruption of the symbiosis between coral and dinoflagellate micro-algae, living within the coral tissue, reveals the white skeleton of coral. Anomalously cold water can also lead to coral bleaching but has been the subject of limited research. Although cold-water bleaching events are less common, they can produce similar impacts on coral reefs as warm-water events. In this study, we explored the effect of temperature and light on the likelihood of cold-water coral bleaching from 1998-2017 using available bleaching observations from the Eastern Tropical Pacific and the Florida Keys. Using satellite-derived sea surface temperature, photosynthetically available radiation and light attenuation data, cold temperature and light exposure metrics were developed and then tested against the bleaching observations using logistic regression. The results show that cold-water bleaching can be best predicted with an accumulated cold-temperature metric, i.e. ‘degree cooling weeks’, analogous to the heat stress metric ‘degree heating weeks’, with high accuracy (90%) and fewer Type I and Type II errors in comparison with other models. Although light, when also considered, improved prediction accuracy, we found that the most reliable framework for cold-water bleaching prediction may be based solely on cold-temperature exposure.

scholarly journals The Purple Leaf (pl6) Mutation Regulates Leaf Color by Altering the Anthocyanin and Chlorophyll Contents in Rice

Plants ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 1477
Author(s):  
Asadullah Khan ◽  
Sanaullah Jalil ◽  
Huan Cao ◽  
Yohannes Tsago ◽  
Mustapha Sunusi ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Anthocyanin Biosynthesis ◽  
Light Attenuation ◽  
Transcript Level ◽  
Underlying Mechanism ◽  
Anthocyanin Accumulation ◽  
Morphological Marker ◽  
Chlorophyll Contents ◽  
Rice Mutant ◽  
Purple Coloration

The anthocyanin biosynthesis attracts strong interest due to the potential antioxidant value and as an important morphological marker. However, the underlying mechanism of anthocyanin accumulation in plant tissues is not clearly understood. Here, a rice mutant with a purple color in the leaf blade, named pl6, was developed from wild type (WT), Zhenong 41, with gamma ray treatment. By map-based cloning, the OsPL6 gene was located on the short arm of chromosome 6. The multiple mutations, such as single nucleotide polymorphism (SNP) at −702, −598, −450, an insertion at −119 in the promoter, three SNPs and one 6-bp deletion in the 5′-UTR region, were identified, which could upregulate the expression of OsPL6 to accumulate anthocyanin. Subsequently, the transcript level of structural genes in the anthocyanin biosynthesis pathway, including OsCHS, OsPAL, OsF3H and OsF3′H, was elevated significantly. Histological analysis revealed that the light attenuation feature of anthocyanin has degraded the grana and stroma thylakoids, which resulted in poor photosynthetic efficiency of purple leaves. Despite this, the photoabatement and antioxidative activity of anthocyanin have better equipped the pl6 mutant to minimize the oxidative damage. Moreover, the contents of abscisic acid (ABA) and cytokanin (CK) were elevated along with anthocyanin accumulation in the pl6 mutant. In conclusion, our results demonstrate that activation of OsPL6 could be responsible for the purple coloration in leaves by accumulating excessive anthocyanin and further reveal that anthocyanin acts as a strong antioxidant to scavenge reactive oxygen species (ROS) and thus play an important role in tissue maintenance.

Seagrass depth range and water quality in southern Moreton Bay, Queensland, Australia

1996 ◽  
Vol 47 (6) ◽  
pp. 763 ◽  
Author(s):  
EG Abal ◽  
WC Dennison
Keyword(s):  
Water Quality ◽  
Chlorophyll A ◽  
Suspended Solids ◽  
Light Attenuation ◽  
River Mouth ◽  
Total Suspended Solids ◽  
Quality Parameters ◽  
Depth Range ◽  
Moreton Bay ◽  
A Site

Correlations between water quality parameters and seagrass depth penetration were developed for use as a biological indicator of integrated light availability and long-term trends in water quality. A year-long water quality monitoring programme in Moreton Bay was coupled with a series of seagrass depth transects. A strong gradient between the western (landward) and eastern (seaward) portions of Moreton Bay was observed in both water quality and seagrass depth range. Higher concentrations of chlorophyll a, total suspended solids, dissolved and total nutrients, and light attenuation coefficients in the water column and correspondingly shallower depth limits of the seagrass Zostera capricorni were observed in the western portions of the bay. Relatively high correlation coefficient values (r2 > 0.8) were observed between light attenuation coefficient, total suspended solids, chlorophyll a, total Kjeldahl nitrogen and Zostera capricorni depth range. Low correlation coefficient values (r2 < 0.8) between seagrass depth range and dissolved inorganic nutrients were observed. Seagrasses had disappeared over a five-year period near the mouth of the Logan River, a turbid river with increased land use in its watershed. At a site 9 km from the river mouth, a significant decrease in seagrass depth range corresponded to higher light attenuation, chlorophyll a, total suspended solids and total nitrogen content relative to a site 21 km from the river mouth. Seagrass depth penetration thus appears to be a sensitive bio-indicator of some water quality parameters, with application for water quality management.

scholarly journals A Novel Thin-Film Technique to Improve Accuracy of Fluorescence-Based Estimates for Periphytic Biofilms

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1464
Author(s):  
Leon Katona ◽  
Yvonne Vadeboncoeur ◽  
Christopher T. Nietch ◽  
Katie Hossler
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Light Attenuation ◽  
Pulse Amplitude ◽  
Light Signal ◽  
Photosynthetic Parameters ◽  
Pam Fluorometry ◽  
Attenuation Coefficients ◽  
Thin Film Technique ◽  
Relative Errors

Recent studies suggest that photophysiological parameters for intact substrates with depth (e.g., periphytic biofilms, microphytobenthos) are overestimated by pulse-amplitude modulated (PAM) fluorometry. This overestimation results from depth-integration effects, following the activation of deeper photosynthesizing layers by an attenuated light signal. To mitigate this error, we propose a novel slide-based thin-film technique in which fluorescence is measured on a vertically representative subsample of the biofilm, spread evenly on a microscope slide. We compared bias and precision for photosynthetic parameters estimated through conventional PAM fluorometry on intact biofilms and through our novel slide-based technique, both theoretically and empirically. Numerical simulations confirmed the consistent overestimation of key parameters for intact biofilms, with relative errors up to 145%, compared to, at most, 52% on thin films. Paired empirical observations likewise demonstrated that estimates based on intact biofilms were consistently higher (up to 248%, p<0.001) than estimates from thin films. Numerical simulation suggested greater precision with the slide-based technique for homogeneous biofilms, but potentially less precision for heterogeneous biofilms with improper subsampling. Our empirical comparison, however, demonstrated some improvement in precision with the slide-based technique (e.g., the coefficient of variation for the maximum electron transport rate was reduced 30%, p=0.009). We recommend the use of the slide-based technique, particularly for biofilms that are thick or have small light attenuation coefficients. Care should be taken, however, to obtain vertically representative subsamples of the biofilm for measurement.

scholarly journals Improved estimation of PM2.5 brown carbon contributions to filter light attenuation

Particuology ◽  
2021 ◽  
Author(s):  
Judith C. Chow ◽  
L.-W. Antony Chen ◽  
Xiaoliang Wang ◽  
Mark C. Green ◽  
John G. Watson
Keyword(s):  
Light Attenuation ◽  
Brown Carbon

Light attenuation through turbid slabs calculated by solutions of the Maxwell equations

2007 ◽  
Author(s):  
J. Schäfer ◽  
A. Kienle ◽  
F. K. Forster ◽  
A. Strey
Keyword(s):  
Maxwell Equations ◽  
Light Attenuation

Particulate light attenuation in a large subtropical lake

1995 ◽  
Vol 52 (8) ◽  
pp. 1803-1811 ◽  
Author(s):  
Karl E. Havens
Keyword(s):  
Surface Water ◽  
Trophic State ◽  
Nutrient Loading ◽  
Light Attenuation ◽  
Algal Growth ◽  
Progressive Increase ◽  
Trophic State Index ◽  
Littoral Region ◽  
Relative Contribution ◽  
Total Light

Deviations among Carlson's trophic state index values were used to quantify a 12-year history of seston composition and underwater light attenuation in Lake Okeechobee, Florida, U.S.A. Deviations between chlorophyll a, total phosphorus, and transparency-based trophic state indices indicated that (i) light attenuation is generally dominated by phosphorus-rich abiotic particles; (ii) abiotic light attenuation is maximal in a central lake region overlying soft mud sediments, and minimal in a near-littoral region overlying hard sand; and (iii) there has been a progressive increase in the relative contribution of algal pigments to total light attenuation between 1980 and 1992. Coincident with that 12-year trend, there have been declines in external nitrogen loads, lake water nitrogen:phosphorus ratios, and wind velocities. Surface water temperatures in the lake have significantly increased. Explanations for the trend in light attenuation include (i) more favorable meteorological conditions for algal growth, which increased the contribution of algae to overall light attenuation and (ii) reduced nitrogen:phosphorus ratios favoring proliferation of buoyant cyanobacteria, which are more effectively sampled by surface water monitoring. In either case, the trend did not coincide historically with enhanced nutrient loading, the common cause of algal proliferation in lakes.

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