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1.
The attenuation of lateral propagating light(LPL) in sea ice was measured using an artificial light source in the Canadian Arctic during the 2007/2008 winter. The apparent attenuation coefficient μ(λ) for lateral propagating light was obtained from the measured logarithmic relative variation rate. In this study an analytical solution based on the strict optical theories is developed to validate the measured result. There is a good consistency between theoretical solution and measured data, by which a quite simple but very rigorous relationship among the light source, measurement geometry, and measured irradiance is established. The attenuation coefficients acquired by measurement and theory are the diffusion attenuation as an apparent optical property of ice, independent of the light source and shining condition. The attenuation ability of sea ice should be caused by the microstructure of sea ice, such as crystal size, ice density, brine volume, air inclusion, etc. It also includes the leak from both interfaces by directional scattering. It is verified that the measuring approach is operational and accurate to measure the attenuation of the LPL. The solution from this study did not tell the connection among the extinction and the inclusions of sea ice theoretically because of insufficient understanding. 相似文献
2.
Estimating the diffuse attenuation coefficient from optically active constituents in UK marine waters 总被引：1，自引：0，他引：1
M.J. Devlin J. Barry D.K. Mills R.J. Gowen J. Foden D. Sivyer N. Greenwood D. Pearce P. Tett 《Estuarine, Coastal and Shelf Science》2009
We report a study of the attenuation of submarine Photosynthetically Active Radiation (PAR) in relation to the concentrations of Optically Active Constituents (OACs) in a range of water types around the United Kingdom. 408 locations were visited between August 2004 and December 2005. The diffuse attenuation coefficient (Kd) was estimated from profiles of downwelling PAR. Concentrations of Suspended Particulate Matter (SPM) were measured gravimetrically and concentrations of phytoplankton chlorophyll (chl) were measured by fluorometrically. Chromophoric Dissolved Organic Matter (CDOM) was measured either by fluorescence or as its proxy, salinity. 相似文献
3.
A simple estimation of light penetration in tidal flat sediments was developed using various sediment size fractions and their
attenuation rate of irradiance. The attenuation coefficients of the sediment size fractions of 63–125, 125–250, 250–500, 500–1000
μm and 1000–2000 μm were 8.10, 4.08, 2.92, 2.12 and 1.44 mm−1, respectively. Using the average attenuation coefficient of the particle size fractions in the sediment, the calculated attenuation
coefficient agreed well with the actual attenuation coefficient. The method presented gives a photo-parameter to predict productivity
in intertidal sediments, given only the particle size fraction. 相似文献
4.
海洋桡足类氨基酸组成及与饵料和光照的关系 总被引：4，自引：0，他引：4
桡足类氨基酸含量受其饵料浮游植物的影响。同一种桡足类因采集地不同，氨基酸的总量也不相同；19种氨基酸重量百分比随不同桡足类而异，但是不同桡足类各种氨基酸占总氨基酸的比例除胱氨酸和牛磺酸的变化比较大以外，其它都基本相同；胱氨酸和牛磺酸的变化与总氨基酸不成正比。各海区不同植食性桡足类的氨基酸组成和海区浮游植物氨基酸的组成有着很好的相关性，相关系数R^2在0．85以上。桡足类胱氨酸占总氨基酸的比例与采样站海水1％光衰减深度有很好的相关关系，其回归方程为y=0．28091nx 0．131，R^2=0．6427，n=13；随海水1％光衰减深度的增加，胱氨酸的含量以对数形式递增。桡足类氨基酸与UV的关系有待进一步研究。 相似文献
5.
Walker O. Smith 《Estuarine, Coastal and Shelf Science》1982,15(4):459-465
The attenuation of light by chlorophyll, particulate and dissolved material, and seawater off the coast of north-west Africa showed distinct cross-shelf variations. Attenuation was most rapid nearshore because of absorption by non-biological particles. This particulate matter was probably aeolian material from the nearby Sahara Desert of resuspended sand from the sediment. Regardless of the source, the marked light extinction resulted in decreased phytoplankton growth nearshore. Light attenuation characteristics of the region were anomalous when compared to those of other ocenic regimes. 相似文献
6.
The solar light field within the ocean from the sea surface to the bottom of the mesopelagic zone was simulated with a radiative transfer model that accounts for the presence of inelastic radiative processes associated with Raman scattering by water molecules, fluorescence of colored dissolved organic matter (CDOM), and fluorescence of chlorophyll-a contained in phytoplankton. The simulation results provide a comprehensive characterization of the ambient light field and apparent optical properties (AOPs) across the entire visible spectral range within the depth range 200–1000 m of the entire mesopelagic zone for varying chlorophyll-a concentration and seawater optical properties in the mixed surface layer of the ocean. With increasing depth in the mesopelagic zone, the solar irradiance is reduced by ~9–10 orders of magnitude and exhibits a major spectral maximum in the blue, typically centered around a light wavelength of 475 nm. In the green and red spectral regions, the light levels are significantly lower but still important owing to local generation of photons via inelastic processes, mostly Raman scattering and to a lesser extent CDOM fluorescence. The Raman scattering produces a distinct secondary maximum in irradiance spectra centered around 565 nm. Comparisons of our results with light produced by the radioactive decay of the unstable potassium isotope contained in sea salt (40K) indicates that the solar irradiance dominates over the 40K-produced irradiance within the majority of the mesopelagic zone for most scenarios considered in our simulations. The angular distribution of radiance indicates the dominance of downward propagation of light in the blue and approach to uniform distribution in the red throughout the mesopelagic zone. Below the approximate depth range 400–500 m, the shape of the angular distribution is nearly invariant with increasing depth in the green and red and varies weakly in the blue. The AOPs at any light wavelength also assume nearly constant values within the deeper portion of the mesopelagic zone. These results indicate that the mesopelagic light field reaches a nearly-asymptotic regime at depths exceeding ~400–500 m. 相似文献
7.
Dag O. Hessen JoLynn Carroll Berit Kjeldstad Anton A. Korosov Lasse H. Pettersson Dmitry Pozdnyakov Kai Sørensen 《Estuarine, Coastal and Shelf Science》2010
Spectral light attenuation profiles and concentrations of total and dissolved carbon (C), nutrients and chlorophyll a (Chla) were studied along transects running from the river mouth to the Kara Sea during late summer 2003 for the Yenisey and fall 2005 for the Ob estuaries. Earth Observation data were used to generate composite images of water color and Chla distribution over the estuaries and the Kara Sea to reveal the spatial impact of the river efflux in terms of optical properties. 相似文献
8.
Dynamics of microphytobenthic biomass in a coastal area of western Seto Inland Sea, Japan 总被引：2，自引：0，他引：2
Hitomi Yamaguchi Shigeru Montani Hiroaki Tsutsumi Ken-ichiro Hamada Naoko Ueda Kuninao Tada 《Estuarine, Coastal and Shelf Science》2007,75(4):423-432
This study focused on the causes of the variation in microphytobenthic biomass and the effects of this variation on macrobenthic animals in the western Seto Inland Sea, Japan, where the importance of microphytobenthos as the primary food source for benthic animals has been recently reported. We investigated the microphytobenthic biomass together with light attenuation of seawater, phytoplanktonic biomass, macrobenthic density and biomass at eight stations (water depth = 5–15 m) during four cruises in 1999–2000. The increased light attenuation coefficient of the water column associated with increased concentration of the phytoplanktonic Chl-a caused a decrease in light flux that reached the seafloor. The biomass of the microphytobenthos within the upper 1 cm of the sediment, 1.9–46.5 mg Chl-a m−2, was inversely correlated with the phytoplanktonic biomass in the overlying water column, 10.9–65.0 mg Chl-a m−2. Thus, interception of light by phytoplankton is considered to be a main cause of the variation in the microphytobenthic biomass. The microphytobenthos biomass showed a significant positive correlation with the macrobenthic density (78–9369 ind. m−2) and biomass (0.4–78.8 gWW m−2). It appears that the increase in oxygen production by the microphytobenthos allowed macrobenthic animals to become more abundant, as a consequence of oxygenation of the organically enriched muddy sediments (14.5 ± 2.69 mg TOC g−1). This study suggests that the variation in the microphytobenthic biomass is influenced by the phytoplanktonic biomass due to shading effect, and the balance between these two functional groups might affect the variability in the macrobenthic density and biomass. 相似文献
9.
《Estuarine, Coastal and Shelf Science》2005,62(1-2):169-181
Taxonomic composition and productivity of winter and spring phytoplankton in a eutrophic estuary have been investigated in order to elucidate the carbon flux under conditions of limitation by physical factors – light and temperature. In spite of the important differences in nutrients, solar radiation and water temperature between winter and spring season, mean concentrations of particulate organic carbon were equal to 13.2 and 13.0 mgC l−1, respectively. Chlorophyll a averaged at 79 μgChl l−1 in winter, that is 69% of spring. Although community respiration accounted for only 6–26% of light saturated photosynthesis, integrated net primary production of the 1.2 m deep water column was negative until April. High attenuation of the water body (Ko = 2.9 m−1) lead to a negative carbon balance (net heterotrophy) below 35 cm for all sampling dates. Thus, the high winter POC and phytoplankton values can only originate from summer or autumn primary production. This assumption was supported by a carbon loss rate of just 3% of total organic carbon per day for the whole water column. The composition of phytoplankton was very constant through both seasons: 39% Chlorophyceae, 33% Cyanobacteria and 25% Bacillariophyceae. As expected, phytoplankton was low light acclimated, having high α values (slope of light limited photosynthesis), but moderate maximum photosynthesis rates at saturating irradiances, which were heavily affected by temperature. Calculation of net carbon flux yet showed net heterotrophy of the Bodden waters in winter and early spring were caused by external physical limitation (low surface irradiance and low temperature) in combination with a high light attenuation of the water body. 相似文献
10.
参对光照变化非常敏感，研究刺参对光照的分子响应非常重要。本研究应用RNA测序获取了刺参暴露于强光（“强光”）、正常光照（“对照”）和完全黑暗（“黑暗”）环境下体壁的基因表达谱情况，通过“对照”与“黑暗”，“对照”与“强光”和“黑暗”与“强光”的比较，在|log2 ratio|≥1和FDR≤0.001的标准下分别发现了1161、113和1705个差异表达基因（DEGs）。基因本体分析表明，“cellular process”和“binding”在“生物过程”和“分子功能”类别中的DEGs富集最多，而“cell”和“cell part”在“细胞组分”类别中的DEGs富集最多。将DEGs与Kyoto Encyclopedia基因和基因组数据库上的于214、41和229条通路进行比对，发现了51、2和57条通路分别显著富集。本研究发现的光特异性DEGs可作为深入研究刺参对光照变化的生化适应机制的重要目标基因。 相似文献
11.
Spatial variation in the photophysiology of symbiotic dinoflagellates (zooxanthellae) of the scleractinian coral Pocillopora damicornis was examined along an environmental gradient in the Whitsunday Islands (Great Barrier Reef) at two depths (3 m and 6 m). Chlorophyll a fluorescence of photosystem II (PSII) and PAR-absorptivity measurements were conducted using an Imaging-PAM (pulse-amplitude-modulation) fluorometer. Most photophysiological parameters correlated with changes in environmental conditions quantified by differences in water quality along the gradient. For example, maximum quantum yield (Fv/Fm) increased and PAR-absorptivity decreased as water quality improved along the gradient from nearshore reefs (low irradiance, elevated nutrients and sediments) to outer islands (high irradiance, low nutrients and sediments). For apparent photosynthetic rate (PSmax) and minimum saturating irradiance (Ek), the direction of change differed depending on sampling depth, suggesting that different mechanisms of photo-acclimatisation operated between shallow and deep corals. Deep corals conformed to typical patterns of light/shade acclimatisation whereas shallow corals exhibited reduced PSmax and Ek with improving water quality coinciding with greater heat dissipation (NPQ241). Furthermore, deep corals on nearshore reefs exhibited elevated Q241 in comparison to outer islands possibly due to effects of sedimentation and/or pollutants rather than irradiance. These results highlight the importance of mesoscale sampling to obtain useful estimates of the variability of photophysiological parameters, particularly if such measures are to be used as bioindicators of the condition of coral reefs. 相似文献
12.
13.
The picophytoplankton evolved to become extremely effective harvesters of light and, thus, dominating productivity in the open ocean. In this study, their distribution in relation to the underwater light field was examined in the Azores Front region of the North Atlantic. In this region, attenuation coefficients of downward irradiance varied between 0.038 and 0.065 m− 1. Maximum absorptions were at the red and green parts of the light spectrum, typical of the oligotrophic ocean. The euphotic zone ranged from 70 to 120 m. The deep chlorophyll maximum (DCM) was found at depths where subsurface light ranged between 0.1 and 1% of its surface values. Prochlorococcus was the dominant phytoplankton group while Synechococcus (cyanobacteria) and picoeukaryotes were much less abundant. The ability of chlorophyll to absorb light, i.e., the absorption coefficient of chlorophyll (a⁎), was found to be dependent on the photoacclimation of the cells and was lower at low-light intensities. Due to a packaging effect and probable pigment changes, a⁎ at the DCM was the lowest while the chlorophyll per Prochlorococcus cell was the highest. This is a major adaptation of the picophytoplankton to low light (less than 1% surface light), which allows them to bloom at the DCM. This study indicates that the Atlantic Ocean models for the estimation of phytoplankton concentration and/or primary production should not use a constant carbon biomass-to-chlorophyll ratio for phytoplankton based on phytoplankton size, and should take into account the variation in chlorophyll-absorption ability. 相似文献
14.
A two-dimensional steady-state model of light-driven phytoplankton productivity and biomass in partially mixed estuaries has been developed. Effects of variations in river flow, suspended sediment concentration, phytoplankton sinking, self-shading and growth rates on distributions of phytoplankton biomass and productivity are investigated.Numerical simulation experiments show that biomass and productivity are particularly sensitive to variations in suspended sediment concentrations typical of natural river sources and to variations in loss rates assumed to be realistic but poorly known for real systems. Changes in the loss rate term within the range of empirical error (such as from dark bottle incubation experiments) cause phytoplankton biomass to change by a factor of two. In estuaries with adequate light penetration in the water column, it could be an advantage for phytoplankton to sink. Species that sink increase their concentration and form a phytoplankton maximum in a way similar to the formation of the estuarine turbidity maximum. When attenuation is severe, however, sinking species have more difficulty in maintaining their population. 相似文献
15.
Atsushi Matsuoka Pierre Larouche Michel Poulin Warwick Vincent Hiroshi Hattori 《Estuarine, Coastal and Shelf Science》2009
The chlorophyll a specific absorption coefficient of phytoplankton, aφ∗(λ) is an important parameter to determine for primary production models and for the estimation of phytoplankton physiological condition. Knowledge of this parameter at high latitudes where nutrient rich cold water submitted to low incident light is a common environment is almost nonexistent. To address this issue, we investigated the light absorption properties of phytoplankton as a function of irradiance, temperature, and nutrients using a large data set in the southern Beaufort Sea during the open water to ice cover transition period. The aφ∗(λ) tended to increase from autumn when open water still existed to early winter when sea ice cover was formed, resulting from a biological selection of smaller-size phytoplankton more efficient to absorb light. There was no significant correlation between aφ∗(λ) and irradiance or temperature for both seasons. However, aφ∗(λ) showed a significant positive correlation with NO3 + NO2. Implications of the results for phytoplankton community adaptation to changing light levels are discussed. 相似文献
16.
千里崖海域真光层光衰减 总被引：2，自引：0，他引：2
根据1986年6月在黄海中部的千里崖海域的水光学实测资料和实验室光学测量,讨论了真光层内光衰减系数在遥感和初级生产力中的应用,定量估算影响光衰减的主要物质成分对光衰减的贡献;并探讨了真光层深度、光衰减系数和透明度三者之间的统计关系。 相似文献
17.
Average values of inherent optical properties for the 400–700 nm waveband were estimated from quantum irradiance measurements on 27 New Zealand lakes of diverse optical character, using published nomograms. Secchi disc depths, turbidity, algal pigment, non‐volatile suspended solids, and absorption by membrane‐filtered samples at 440 nm (g 440 ) were also measured. Turbidity (NTU) correlated closely with the scattering coefficient (m‐1) and these quantities were almost numerically equal, as found in other studies. The data were found to conform to an expression in the oceanographic literature relating Secchi disc depth to the beam attenuation and diffuse attenuation coefficients. Specific beam attenuation, scattering, and absorption coefficients were estimated from the coefficients of linear multiple regressions of the measured total coefficients on the variables: total pigment (chlorophyll a + phaeopigment), non‐volatile suspended solids, and g 440. The estimated values were in reasonable agreement with similar specific coefficients reported in the oceanographic literature. The coefficients provide a basis for predicting clarity in new impoundments or for predicting the effects of loading changes (e.g., of nutrients) on the clarity of existing lakes. The coefficients can be used for classifying lake waters into different optical types. 相似文献
18.
V. I. Man’kovsky 《Physical Oceanography》2012,21(5):305-319
We compute model spectra of the beam attenuation coefficient in surface waters of the Mediterranean Sea. These spectra are
used to determine the contribution of the components of seawater (suspended matter, yellow substance, pigments of phytoplankton,
and pure water) to the beam attenuation coefficient in different types of seawater. For the surface waters, we establish the
relationship between the light scattering coefficient and the attenuation coefficient at a wavelength of 547 nm and determine
the background (limiting minimum) value of the coefficient of absorption by the yellow substance in waters of the Mediterranean
Sea. It is compared with the values of the same parameter for some other basins (Black Sea, Lake Baikal, Baltic Sea, and oceanic
waters). 相似文献
19.
Yongsheng Wu Charles C.L. Tang Shubha Sathyendranath Trevor Platt 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2630
The impact of bio-optical heating on the properties of the upper Labrador Sea water was investigated by considering changes in light attenuation in water associated with the seasonal change of chlorophyll distribution. The time- and depth-dependent attenuation coefficients were obtained from remotely sensed SeaWiFS ocean-colour data. Sea-surface temperature (SST) and mixed-layer depth (MLD) were computed from a three-dimensional ocean circulation model. The model was integrated from 1999 to 2003 with 6-hourly atmospheric forcing. The changes in SST and MLD attributable to bio-optical heating were determined by comparing the model results using the observed attenuation coefficients (chlorophyll) to those using a weak and constant attenuation (clear water). The model results show that bio-optical heating is controlled mainly by chlorophyll concentration and MLD. The increase in SST is around 1 °C in most parts of the Labrador Sea and the shelves, and up to 2.7 °C in areas of shallow MLD and high chlorophyll concentrations (the Grand Banks and Northeastern Newfoundland Shelf). The increase is much higher than that found in previous studies, which was typically a fraction of a degree. Bio-optical heating also can enhance the stratification of the upper ocean and reduce the MLD by 20–50%. 相似文献