Light Penetration Levels Research Articles

A study of water depth on the growth and productivity of seaweed <i>Kappaphycus alvarezii</i>

This study aims to investigate the impact of varying the depth of water on the growth and productivity of seaweed Kappaphycus alvarezii. The study was carried out in the seas of Pallette. The research methodology used in this study incorporates three different planting depth treatments, specifically 1.5 meters, 3 meters, and 4 meters. In each treatment, 50 grams of Kappaphycus alvarezii seeds per bunch were used. The findings of this study indicate that seaweed cultivation at a depth of 1.5 m yields significantly favourable outcomes compared to the treatments conducted at depths of 3 m and 4 m, where growth is comparatively less optimal. This occurrence can be attributed to the diminished level of light penetration at such a depth. There is an inverse relationship between the depth of seaweed planting and the rate of weight gain. The optimal depth for seaweed cultivation for 42 days is 1.5 meters, with an average specific growth rate of 3% daily. On the contrary, the treatment carried out at a depth of 1.5 m showed the most substantial increase in biomass, averaging 122 g. Additionally, the maximum yield of seaweed was observed in the same treatment, precisely measuring 1,208 g/m2.

Effect of light microclimate on the quality of ‘d’Anjou’ pears in mature open-centre tree architecture

Light availability within trees is an important factor for canopy and fruit development as light drives photosynthetic processes. The effect of pre-harvest light microclimate on ‘d’Anjou’ pear fruit quality from harvest through to cold storage and ripening on fruit grown in open vase pear tree canopy was investigated. Light penetration was used to determine the light availability at different positions within the tree canopy. Five light penetration levels were predefined as 0–20%, 20%–40%, 40%–60%, 60%–80%, and 80%–100% and 60 fruits were selected from each level for quality assessment during three-month cold storage and postharvest ripening period. At harvest, upper canopy portions had a greater number of fruit than lower portions, but average single fruit mass was similar. During the cold storage and ripening period, the IAD index, a measure of chlorophyll degreening indicating fruit maturity, decreased. Fruit mass decreased for all light penetration levels during cold storage. No significant difference was found in fruit mass between light penetration levels following cold storage. Fruit soluble solids increased with light penetration while firmness exhibited an inverse relationship with light penetration level. Fruit from 80% to 100% light penetration level had significantly lower titratable acidity compared to other levels. This study indicated that light microclimate had consequential effects on ‘d'Anjou’ pear fruit quality, and effects of light penetration on quality were most pronounced in extreme light conditions, which are suggested to be the focus of further research.

Noninvasive Subsurface Analysis Using Multiple Miniaturized Raman Probes, Part I: Basic Study of Thin-Layered Transparent Models of Biomedical Tissues

This study describes a basic theory for reconstructing pure Raman signals of materials composing a multilayer sample from Raman spectra obtained using two types of miniaturized Raman probes. An illustrative example is demonstrated using a multilayer system of samples composed of the transparent plastics polymethylmethacrylate (PMMA) and polyethylene (PE) as a model of thin-layered biomedical tissues. When the same region of an object is measured using Raman probes with different focal properties, the Raman spectra provide different depth profile information depending on the level of light penetration. Thus, a detailed comparison of the spectra can provide an interesting opportunity to probe the differences between the layers. A simple analytic form is presented for reconstructing the pure Raman spectra of the embedded layer. The method applies an understanding of the Raman sampling volume in layered transparent materials to the interpretation of Raman spectra experimentally measured by multiple probes. The basic theory described here is necessary for the expansion of the technique to turbid media, such as biological samples, where light-scattering effects must be considered. The potential applications of the proposed method include material and catalyst subsurface probing through different embedded materials, such as assessment of silicon wafers, effective noninvasive screening for catalyst synthesis, and biomedical tissue research.

Impacts of light penetration on the bathymetry of reef microboring communities: implications for the development of microendolithic trace assemblages

Sediment samples recovered from three proximate reef environments in north Jamaica, characterised by different light penetration regimes, reveal marked variations in the bathymetric range of sediment microboring communities. In contrast to clear water environments, assemblages developed in turbid water conditions undergo both bathymetric restriction and compression in their range. In clear water sites, the upper photic–lower photic zone transition occurs between depths of 20–30 m. This is marked by a shift from a predominance of cyanobacterial (e.g., Eurygonum nodosum, Scolecia filosa, Fasciculus frutex and Fasciculus dactylus) and chlorophyte (e.g., Rhopalia catenata, Fasciculus grandis, Reticulina elegans and Scolecia botulifera) traces, to assemblages dominated by the traces E. nodosum and S. filosa (cyanobacteria), F. grandis (chlorophyte), Palaeoconchocelis starmarchii (rhodophyte) and Orthogonum fusiferum and Saccomorpha sphaerula (fungi). At sites characterised by intermediate levels of turbidity this same assemblage transition occurs at around 15–20 m depth and at the most turbid site at depths of only 5–10 m. Integration of assemblage data and light readings indicates that this transition occurs where percentages of surface light illumination are reduced to around 10–15%. Compression of the lower photic zone is so extreme at the most turbid site, that microboring assemblages at only 30 m depth show evidence of a transition to an assemblage associated with dysphotic (<1% of surface illumination) conditions. This is dominated by fungal boring traces. Given that microendolithic assemblages have been widely considered to represent useful palaeobathymetric indicators, this study illustrates that it is more accurate to regard assemblages as indicative only of photic zones. The bathymetric range and extent of zones clearly varies significantly as light penetration levels change. Caution is thus needed in the extrapolation of assemblage or ichnocoenosis data to specific bathymetric ranges.

Variation of climatic and physical co-determinants of phytoplankton community in four nictemeral sampling days in a shallow tropical reservoir, southeastern Brazil.

Spatial and temporal variation of climatic and physical characteristics in a shallow tropical reservoir in the city of São Paulo, Southeastern Brazil, and their possible influence on the dynamics of the phytoplankton population. Samples were taken at 5 depths of the water column (subsurface: 1% Io, 10% Io, 2 m, and bottom) and at 4 hour intervals (6:00, 10:00, 14:00, 18:00, 22:00, 2:00, and 6:00 h) during summer (March 3-4), fall (June 13-14), winter (August 29-30), and spring (November 29-30) of 1994 at a single sampling station. Garças Reservoir (23 degrees 39'S, 46 degrees 37'W) is a kinetic turbulent system, highly influenced by winds, with stratification that may last for days or weeks, and which undergoes mixing periods more than once in a year. A thermal pattern of this type is comparable to the warm discontinuous polymetric. Considering its optical properties, the water body was classified as an ecosystem with moderate turbidity, which decreases basically due to increased phacopigment concentration during the spring. Also, the reservoir is an ecosystem whose phytoplanktonic community is subjected to stress, the degree of which depends on level of light penetration.

Factors influencing the recovery of submersed macrophytes in four coastal marshes of Lake Ontario

In this study, we investigated the impact of carp and turbidity on the growth of macrophytes from propagules in four Lake Ontario marshes with low submersed macrophyte abundance. A healthy propagule bank was transplanted into 4 m2 carp exclosures (5-cm-mesh cages), turbidity exclosures (enclosed in plastic), and open control sites, with four replicates per treatment used in each marsh. Carp exclosures were intended to protect the transplanted propagule banks from carp and other large aquatic organisms; turbidity exclosures were intended to also reduce wind exposure and inflowing suspended sediments, thus increasing the amount of light reaching bottom sediments. The mean density of shoots produced in the turbidity exclosures (256±46 shoots·m−2) was significantly higher than that produced in carp enclosures (20±7 shoots·m−2) and open controls (10±5 shoots·m−2); above-ground biomass (AGB) was also significantly greater in turbidity exclosures. The difference in protection afforded the developing submersed macrophyte shoots can be attributed to the lower concentration of total suspended solids and greater level of light penetration in the turbidity exclosures. There was a strong linear relationship between photosynthetically active radiation (PAR) reaching the substrate surface and shoot growth in terms of both shoot density and AGB. The growth response was more sensitive to PAR in the field than it was in a growth chamber, suggesting that light levels are more critical to shoot development when multiple stressors are involved. The two marshes exposed to high wave energy had very high levels of suspended solids, and the introduced propagule bank was eroded away in controls and carp exclosures. In such marshes, both turbidity and exposure would have to be addressed for macrophyte recovery.

Effects of Silvicultural Edges on the Distribution and Abundance of Amphibians in Maine

Amphibians share several biological characteristics that may cause them to be sensitive to abrupt transitions in microhabitat and microclimate that occur across forest edges. To better understand the importance of edge effects on amphibians in a forested landscape, we sampled the distribution of populations along drift fences placed perpendicular to silvicultural edges of varying contrast in central Maine. Within the community of amphibians sampled (14 species), salamanders generally were more sensitive to even‐aged harvesting and associated edge effects than were anurans, but forest habitat generalists and specialists were identified within both groups. We conservatively estimated the depth of edge effects at 25–35 m for a subset of management‐sensitive species (Plethodon cinereus, Ambystoma maculatum, A. laterale, and Rana sylvatica). An index of edge contrast, calculated using ambient light penetration levels, was valuable in predicting the magnitude of edge effects among sites that included silvicultural edges of different age and origin (old field plantations versus recent clearcuts). Some structural microhabitat variables relevant to forest management were identified as potentially limiting to amphibians near forest edges, including canopy cover, litter cover, and a measure of stumps, snags, and their root channels. Our observations are consistent with the results of other work on biotic edge effects in the eastern United States and suggest that impacts from intensive forest management practices extend beyond the boundaries of harvested stands.Efectos de Bordes Silviculturales en la Distribución y Abundancia de Anfibios en MaineLos anfibios comparten diversas characterísticas biológicas que pueden ser la causa de que sean sensitivos a transiciones abruptas en microhábitats y microclimas que ocurren a lo largo de los bordes de bosques. Para entender mejor la importancia de los efectos de bordes en anfibios en un paisaje boscoso, muestreamos la distribución de poblaciones a lo largo de vallas de desvío colocadas perpendicularmente a bordes silviculturales de contrastes variantes en la parte central de Maine, USA. Dentro de la comunidad de anfibios muestreados (14 spp), las salamandras generalmente fueron más sensitivas a la tala de edad constante y efectos asociados al borde que los anuros, pero tanto especies generalistas y especialistas de hábitat boscoso fueron identificadas dentro de ambos grupos. Conservativamente estimamos la profundidad del efecto de borde a 25–35m para un subset de especies sensitivas al manejo (Plethodon cinereus, Ambystoma maculatum, A. Laterale y Rana sylvatica). Un índice de constraste de borde, calculado usando niveles de penetración de luz ambiental fue valioso para predecir la magnitud de los efectos de borde entre sitios que incluyeron bordes silviculturales a diferentes edades y origenes (plantaciones viejas contra clareados recientes). Algunas variables estructurales de microhábitat relevantes para el manejo forestal fueron identificadas como potencialmente limitantes para anfibios cercanos a los bordes de bosques, incluyendo la cobertura del dosel, cobertura de hojarasca y una medición de varas, tocones y sus canales de raíces. Nuestras obsevaciones son consistentes con los resultados de otro trabajo en efectos bióticos de borde en el este de los Estados Unidos y sugieren que los impactos de prácticas de manejo forestal intensivo se extienden mas allá de los límites de los sitios cosechados.

Conservation headlands for rare arable weeds: The effects of fertilizer application and light penetration on plant growth

In addition to promoting agricultural wildlife in general, conservation headlands may be a method of providing a refuge to endangered arable weeds. The conservation headland technique excludes herbicide and insecticide use in the outer 2–3 m of the arable field, but does not restrict fertilizer inputs. We studied the effects of fertilizer application on the weed vegetation in relation to light penetration in three crop edges in the vicinity of Wageningen, The Netherlands. Furthermore, the growth response of five endangered arable weeds to different fertilizer treatments and light penetration levels was examined. Species richness and weed growth were significantly reduced in the fertilized crop edges but individual species showed both significant increases and decreases. In the fertilized crop edges, light penetration was directly related to weed performance, limiting species richness and plant growth of both the total weed vegetation and individual species, while in the unfertilized crop edges no such relation existed. Likewise, light penetration proved to be the most important correlate of plant growth of all five endangered arable weeds. Assuming that biomass production is closely related to seed production, fertilizing conservation headlands will result in reduced viability of populations of rare weeds. If preservation of rare arable weeds is one of the main goals of conservation headlands, cessation of fertilizer inputs may be required.

Drought Effect on Water Management and Limnology of Kainji Lake, Nigeria

The paper defines drought comprehensively after Havens (1954). It then reviewed the works of Nedeco & Balfour Beatty (1961) and Abiodun (1974). The former studied the two types of inflows (white & black floods) into the Kainji Lake and the correlation between rainfall and run-off in the river Niger basin prior to the formation of the lake; while the later studied the effect of drought on the performance of the Kainji Hydroelectric scheme and made recommendations on steps for combating drought. This present paper shows the effect of drought on rainfall, the inflows into the lake, water management techniques, water transparency, and plankton life in the lake by comparing data obtained in a drought-free year with those of a drought year.The data on total annual rainfall indicate a deficit of 46% during the drought year. This deficit affected the inflowsinto the lake such that the peaks of the two floods were 32% and 18% lower respectively than those of the drought-free year. This drought further affected the normal management operation of the lake water for hydroelectric production and extended the exchange ratio for the lake to 2:1 in contrast to a ratio of 4:1 in the drought-free year. In the drought year water transparency was generally lower and the 1% level of light penetration in the lake was nearer the surface. These affected the abundance of plankton life in the lake during the drought year.

Hygiene in Modern Bench-Grafting

Long-term investigations and experiments in modern bench-grafting at the Institute for Vine-Breeding and Vine-Grafting of the Hessian Research Institute (Geisenheim, West Germany) are reviewed. Treatment of grafting material with a Chinosol solution (8-hydroxychinol sulfate-potassium sulfate) has proven effective against <i>Botrytis cinerea</i> Pers., <i>Phomopsis viticola</i> Sacc., and other fungus infections and has significantly increased the successful take and rooting of grafts. The factors determining the success of the treatment were shown to be concentration, temperature, and contact period. Found most effective for a prestorage treatment was a concentration of 0.5% and a soaking period of 15 hours at 10-18°C. Grafting material cut to length ahead of time can then be stored in plastic sacks at 1°C in the presence of free water. Chinosol is also effective in treating material freshly cut to proper length as well as one-year-old rooted grafts and cuttings. Hygienic methods of paraffining and callusing are reviewed. Treatment with 0.05% Chinosol solution, as well as a new agent, is recommended. Recent experiments have demonstrated that sterile Perlite is the best material for topping-off the callusing boxes and that it can perhaps eliminate the need for grafting wax. Perlite allows a significant level of light penetration and the young shoots begin their photosynthetic activity earlier.

Hygiene in Modern Bench-Grafting

Long-term investigations and experiments in modern bench-grafting at the Institute for Vine-Breeding and Vine-Grafting of the Hessian Research Institute (Geisenheim, West Germany) are reviewed. Treatment of grafting material with a Chinosol solution (8-hydroxychinol sulfate-potassium sulfate) has proven effective against <i>Botrytis cinerea</i> Pers., <i>Phomopsis viticola</i> Sacc., and other fungus infections and has significantly increased the successful take and rooting of grafts. The factors determining the success of the treatment were shown to be concentration, temperature, and contact period. Found most effective for a prestorage treatment was a concentration of 0.5% and a soaking period of 15 hours at 10-18°C. Grafting material cut to length ahead of time can then be stored in plastic sacks at 1°C in the presence of free water. Chinosol is also effective in treating material freshly cut to proper length as well as one-year-old rooted grafts and cuttings. Hygienic methods of paraffining and callusing are reviewed. Treatment with 0.05% Chinosol solution, as well as a new agent, is recommended. Recent experiments have demonstrated that sterile Perlite is the best material for topping-off the callusing boxes and that it can perhaps eliminate the need for grafting wax. Perlite allows a significant level of light penetration and the young shoots begin their photosynthetic activity earlier.