Optical characteristics of Lake Baikal waters and their cross-correlations

Correlations between the optical characteristics of Lake Baikal waters and relations of optical characteristics with the content of suspended matter and chlorophyll in waters of the lake have been found. The formulas obtained for Lake Baikal waters have been compared with similar formulas of relations in other water basins.     

Spectral contributions of the components of seawater to the beam attenuation coefficient in surface waters of the Mediterranean Sea

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).     

三峡工程一期蓄水后长江口悬浮体形态及物质组成

2003年6月1—10日为长江三峡工程一期蓄水期,为了研究长江三峡工程蓄水对长江口环境的影响,2003年6月15—25日组织了长江口及其邻近海域环境综合调查,对该次调查所取得的悬浮体样品进行了显微观察和X射线衍射测定,分析了不同水体中悬浮体颗粒的形态特征和物质组成。结果表明:从徐六泾到长江口邻近海域,悬浮体颗粒形态特征不同,徐六泾至南支主槽,悬浮体颗粒以单颗粒为主;拦门沙最大浑浊带,悬浮体颗粒以大絮团、团状絮团和絮网为主;长江口邻近海域,悬浮体颗粒以有机质絮团和单颗粒并存为主。长江口区悬浮体矿物颗粒主要以粒状或片状形式存在。悬浮体矿物颗粒主要由石英、长石等碎屑矿物和黏土矿物组成。从河道到长江口外的邻近海域,石英和长石含量逐渐降低,伊利石和绿泥石含量逐渐增加,高岭石含量先降低后增加。与蓄水前相比,蓄水后徐六泾附近小絮团数量有所增加,蓄水前后拦门沙和长江口邻近海域悬浮体形态特征和长江口地区悬浮体物质组成并未发生明显变化。     

Freshening of near-bottom waters in Lake Baikal triggered by the Mw6.2 Kultuk earthquake of August 2008

In September 2008, freshening of near-bottom water and an increase in concentration of suspended particles were observed in the western part of southern Lake Baikal. The reduction in the content of total dissolved solids was about 0.4–0.7?mg/kg (0.7?%), and average suspended particle concentration increased strongly to 6–9?mg/l, the background value being 0.2?mg/l. The spatial distribution of these waters was virtually identical to the focal area of the M_w6.2 Kultuk earthquake that occurred on 27 August 2008. It is suggested that there was a causal relationship between these two phenomena. Freshening of a significant amount (about 20?km³) of near-bottom waters was plausibly caused by an input of poorly mineralized pore waters from bottom sediments as a result of dissociation of methane gas hydrates suspected to occur in the area. The energy radiated by the earthquake source was four orders of magnitude smaller than that needed to explain the observed freshening of near-bottom waters. This points to other mechanisms leading to seismic-induced sediment failure and possible subsequent hydrate dissociation in the case of the Kultuk earthquake.     

太湖水体光学衰减系数的特征及参数化

利用2001-2002年周年太湖全湖不同湖区湖泊光学及表层水样的实测资料,分析了太湖水体表层光学衰减系数与透明度、无机和有机颗粒物质及叶绿素a的相关关系,建立了表层水光学衰减系数与无机、有机颗粒物质及叶绿素a多元线性回归方程。结果表明,光学衰减系数与透明度的关系为：Kdg0.096 1.852/ST;表层水光学衰减系数与无机、有机颗粒物质及叶绿素a多元线性回归方程为：Kd=0.219 0.0768Ciss 0.214Cdet 0.006Cchl;光学衰减系数变化的主要影响因子是无机及有机颗粒物。     

南海三沙永乐龙洞悬浮体组分及其来源

三沙永乐龙洞位于南海北部永乐环礁上,水深达300m,是世界已知最深的海洋蓝洞。采用扫描电镜和能谱仪对2016年10月和2017年3月在永乐龙洞从表层到270m的24个不同深度采集的水体悬浮体组分进行了分析,发现悬浮体组分种类丰富,粒度差异大,来源/成因多样,可分为生源碎屑、陆源碎屑、自生矿物颗粒、有机包膜-海洋雪花和人工产物碎屑等5类。生源碎屑以碳酸盐为主,主要来自现代珊瑚礁的松散沉积物,是悬浮体的主要组分。陆源碎屑主要是造岩矿物如石英和长石,以及一些包括重矿物的副矿物,其中细小的陆源造岩矿物碎屑,有可能来自气溶胶沉降,粗粒碎屑可能来自附近琛航岛工程散落的海南岛沿岸海砂。自生矿物颗粒包括重晶石、球状微粒氧化铁集合体和纳米黄铁矿。纳米黄铁矿及其集合体出现在130m以深水体中,是含硫化氢的无氧极端水体的特定产物。有机包膜在生物降解过程中形成,有时包覆多个不同组分的颗粒,常呈片状漂浮在水体中,形成海洋雪花。人工产物碎屑包括多种金属碎屑、微塑料纤维丝和过硫化铅丝。金属碎屑可能来自船只金属部件耗损,微塑料纤维可能来自渔网残余。本文是首次有关海洋蓝洞悬浮体组分的系统报道。永乐龙洞悬浮体组分特色鲜明,对认识其生态系统和沉积记录有重要意义。     

Single particle analysis of suspended matter in the Makasar Strait and Flores Sea with particular reference to tin-bearing particles

Suspended matter samples filtered from surface waters and two depth profiles from the Flores Sea and Makasar Strait were investigated by electron probe X-ray microanalysis (EPXMA) and laser microprobe mass analysis (LAMMA). EPXMA yielded discrete morphological and chemical analysis of the major particle types of suspended matter. Cluster analysis revealed that thirteen main particle types described the composition of suspended matter of the Flores Sea and Makasar Strait. Silicates, aluminosilicates and Fe-oxyhydroxides were the predominant particle types. Suspended matter of the basins studied contained high levels of tin-bearing particles. On the basis of their composition, tin particles can be divided into three groups: (1) tin oxide/hydroxides (cassiterite, romarchite, hydroromarchite); (2) iron-oxyhydroxides with adsorbed tin; and (3) mixed oxidation state tin hydroxysulphates. Only ultra-fine cassiterite particles enter the seawater in suspended state. Dissolved tin species entering the sea have three alternatives: (1) to be scavenged by Fe-oxyhydroxides; (2) to precipitate as tin oxide/hydroxides (romarchite, hydroromarchite); (3) to precipitate as tin hydroxysulphates. The conclusion is that dissolved and suspended tin originate from local sources in the land frame of the basins as well as from remote sources in the Indonesian Archipelago. Four different sectors of the waters studied have suspended matter with different composition: (1) the Mahakam River–Delta zone; (2) the open Flores Sea; (3) the landlocked Saleh Bay; (4) the Makasar Strait proper. The depth distribution of suspended particle types is mainly influenced by: (1) the bottom nepheloid layer and calcite lysocline in the Flores Sea; (2) the high bioproduction in the surface water layer and the vertical distribution of organic matter in the Makasar Strait.     

Relationship between the suspended particulate matter and microorganisms in the White Sea waters

During the summer periods of 2003–2005, the spatial and vertical distributions of the suspended particulate matter and bacteria in stratified and homogeneous waters of the White Sea was studied. The results of the study of various quantitative characteristics of the suspended particulate matter (first of all, the area of the surface and the volumetric and mass concentrations) and the abundance of microorganisms in the water are discussed. A direct correlation between the value of the surface area of the suspended particulate matter and the total number of bacteria in the water is revealed. However, it was manifested only during the early summer period of the observations and was not expressed at the end of the summer. The enhanced surface area of the suspended particulate matter can indicate the higher biochemical activity of its particles. The influence of the pelitic fraction on the bacteria abundance in different parts of the sea during the summer is estimated.     

The distribution of the suspended matter concentration in the Kara Sea in September 2007 based on ship and satellite data

The distribution of the suspended particulate matter concentration in the Kara Sea is analyzed based on ship and satellite data. The statistical relationships between the suspended matter concentration and the optical characteristics were revealed. Charts of the distribution of the suspended matter concentration in the Kara Sea were plotted, which confirmed that the application of optical methods for analyzing the spatial distribution of the suspended matter is effective. The most turbid waters were observed in the Ob Gulf, Yenisei Bay, the Baidaratskaya Gulf, and the adjacent regions. The smallest concentrations of suspended matter were observed in the central and western parts of the Kara Sea.     

Suspended matter regime in the Yellow Sea

Winter and summer oceanographic conditions in the Yellow Sea produce distinctly different distributions and compositions of suspended particles within the water column. During the winter, strong northwest winds cool and mix the local water column and generate surface waves which resuspend bottom sediment in the north Yellow Sea and in the shoal regions of the western Yellow Sea near Jiangsu Province, and transport it southwards. Wintertime suspended particle concentrations in nearbottom waters can exceed 500 mg/l in nearshore areas and 20 mg/l in offshore waters.During the summer, light southerly winds and a strongly stratified water column localize the distribution of resuspended sediments. Nearbottom concentrations of suspended particulates are generally less than 10 mg/l. Nearsurface concentrations generally are not dissimilar from those seen during the winter, but the particles are primarily biogenic rather than resuspended mineral grains.     

Size distribution of detrital mineral grains suspended in surface waters of the Yellow Sea and East China sea

Anisotropic detrital mineral grains were segregated microscopically from the suspended matter in surface waters of the Yellow Sea and East China Sea. Microscopic grain-size measurements of the anisotropic minerals were carried out for more than 80 slide specimens which are distributed homogeneously in the Yellow Sea and East China Sea. The distribution maps of mean grain size and sorting coefficients indicate that the mean size becomes coarser as one goes offshore, and the sorting coefficients are larger in the southern portion and smaller in the northern portion of this region. The clay-sized minerals in the suspended sediments carried out by the deltaic rivers of the continent were deposited in the nearshore area while coarser silt-sized minerals were suspended in offshore waters. The larger sorting coefficients (standard deviations) in the southern portion may imply that the silt-sized grains of offshore waters contain coarser sand-sized grains. The sand-sized grains may be supplied from offshore Taiwan and the Bashi Channel and transported by the main flow of the Kuroshio current.     

Distribution of sterol and fatty alcohol biomarkers in particulate matter from the frontal structure of the Alboran Sea (S.W. Mediterranean Sea)

Sterol and fatty alcohol biomarkers were analyzed in suspended and sinking particles from the water column (20–300 m) of the Almeria–Oran frontal zone to characterize the biogenic sources and biogeochemical processes. Diatom- and haptophyte-related sterols were predominant at all sites and vertical distributions of sterol, and fatty alcohol biomarkers in sinking particles were markedly different from suspended particles. In contrast to the relatively fresh sinking particles with elevated concentrations of phyto- and zooplanktonic sterols, suspended particles were extensively degraded with increasing depth and exhibited a more terrestrial and zooplanktonic signature with depth.Sterol and alcohol biomarkers distributions and δ¹³C values from the jet core and the associated gyre of Atlantic waters showed a decoupling between the sinking particles of 100- and 300-m depth, demonstrating the influence of lateral advection in the frontal zone. In contrast, vertical transport of the particulate organic matter in Mediterranean waters was interpreted from the similar isotopic and molecular composition at both depths. The high abundance of phytosterols and phytol below the euphotic zone at 100 m signified that downwelling of biomass occurred on the downstream side of the gyre. The high concentrations of phytosterols and POC, in combination with the high phytosterols/phytol ratio, indicated the accumulation of detrital plant material in the oligotrophic Mediterranean waters near the frontal zone.A higher contribution of phytol in the sinking particles collected during the night at the surface of the jet and at the upstream side of the gyre provided evidence of diel vertical zooplankton migration and important grazing by herbivorous zooplankton.Carbon isotope ratios of sterols confirmed that the 24-ethylcholest-5-en-3β-ol, commonly associated with terrestrial sources, was a substantial constituent of the phytoplankton in this area. However, the more δ¹³C depleted values obtained for this compound in suspended particles suggested that there was some terrestrial contribution that only becomes evident after degradation of the more labile marine organic matter.     

Faunal communities at sites of gas- and oil-bearing fluids in Lake Baikal

Macro- and meiofaunal communities were examined at four geomorphologically distinct sites with different gas- and oil-bearing fluid characteristics in the northern, central and southern basins of Lake Baikal. All sites had elevated concentrations of bicarbonate, nitrate, sulphate and chloride ions in pore fluids, with highest values at the Frolikha vent. Elevated levels of iron ions were found in pore waters of the St. Petersburg methane seep and the Gorevoy Utes oil seep. The chemical composition of pore waters at the Malenky mud volcano was similar to that reported in earlier work. Consistent with published data, the Frolikha vent (northern basin) and the St. Petersburg methane seep (central basin) were characterised by methane of mixed genesis (thermogenic + biogenic), whereas the methane source was mainly thermogenic at the Gorevoy Utes oil seep (central basin) and biogenic at the Malenky mud volcano (southern basin). In contrast to marine seep ecosystems, the macrofauna was dominated only by amphipods, giant planarians and oligochaetes, whereas bivalves were absent; the meiofauna was similar to its marine counterpart, being dominated by nematodes, cyclops, harpacticoids and ostracods. A statistically significant positive relationship was revealed between faunal abundance and the availability of bacterial mats on seep sediments. Moreover, ANOVA tests showed significant increases in both meiozoobenthic and macrozoobenthic densities at “hot spot” vent/seep sites relative to discharge-free reference sites. The isotopic composition of carbon and nitrogen at various trophic levels of these benthic vent/seep communities was found to differ markedly from that reported by earlier studies for the pelagic and other benthic food webs in Lake Baikal. As in marine seeps, the macrofauna had variable isotopic signatures. Light δ¹³C and δ¹⁵N values suggest the utilization of chemosynthetically fixed and/or methane-derived organic matter. By contrast, the heavy δ¹³C signatures of some mobile amphipods likely reflect consumption of photosynthetically derived carbon. These findings would at least partly explain why Lake Baikal is a notable outlier in global temperature–biodiversity patterns, exhibiting the highest biodiversity of any lake worldwide but at an extremely cold average temperature.     

Manganese recycling in coastal waters

Both water and suspended particulate matter in the deep water of the Gulf of St. Lawrence are greatly enriched in manganese. Maximum dissolved manganese concentrations are encountered close to the sediment-water interface whereas the particulate matter with highest manganese content occurs 30–100 m above the bottom. The elevated concentrations are attributed to the diagenetic release of dissolved manganese from the underlying fine-grained sediments and its subsequent precipitation in the water column. The rate of manganese precipitation is rapid compared to the rates of diffusion and mixing in the bottom water. Part of the manganese-enriched particulate matter becomes mixed throughout the water column by advection and diffusion. Thus, particles enriched in manganese can ultimately be carried into the open ocean by prevailing currents. This process, which appears to be widespread in eastern Canadian coastal waters, enables manganese originally associated with rapidly settling terrigenous particles to be transferred to slowly settling fine-grained suspended particles entering the ocean from coastal environments. In this way, riverborne manganese of terrigenous origin may well account for a major proportion of the excess manganese in pelagic sediments.     

A spectral model of underwater irradiance in the Black Sea

We develop a semiempirical spectral model of penetrating irradiance taking into account the biooptical characteristics of the Black Sea. The evaluation of the contributions of the principal optically active components to the total absorption of light in the sea shows that, in the short-wave range (400–500 nm), light is mainly absorbed by the dissolved organic matter (41–77%). The contribution of phytoplankton to the total absorption attains its maximum values (26–37%) in the abyssal part of the sea in the period of spring blooming of diatoms. In the coastal waters, the absorption of light by suspended nonalgae particles in summer is almost twice as intense (20–30%) as in the open sea (8–13%). The analysis of the sensitivity of our model shows that the absorption of light by dissolved organic matter is more significant for the estimation of the photosynthetically active radiation in the Black Sea than the concentration of pigments and backscattering of light by suspended particles. The comparison of the results of model computations with the data of measurements of the underwater irradiance reveals high accuracy of the proposed model.     

黄河口海域悬沙光谱特征的研究

分析了５７组含沙水体光谱反射曲线特征，定量描述悬浮水体光谱反射峰值处波长的“红移”现象。在此基础上得出黄河口区野外实测悬浮体含量与光谱反射率呈较好的相关关系，相关系数为０．８９，且在４个波段中，ＭＳＳ７相关系数最低，ＭＳＳ６最高。因而用分段回归或复相关模式来研究悬沙含量，效果较好。文中最后讨论了提高遥感信息－悬沙相关关系精度的方法，提出增加参与回归模型参数的设想，特别是增加悬沙粒度参数。     

Investigating the effect of ballasting by CaCO3 in Emiliania huxleyi, II: Decomposition of particulate organic matter

The quantitative relationship between organic carbon and mineral contents of particles sinking below 1800 m in the ocean indicates that organisms with mineral shells such as coccolithophores are of special importance for transporting carbon into the deep sea. Several hypotheses about the mechanism behind this relationship between minerals and organic matter have been raised, such as mineral protection of organic matter or enhanced sinking rates through ballast addition. We examined organic matter decomposition of calcifying and non-calcifying Emiliania huxleyi cultures in an experiment that allowed aggregation and settling in rotating tanks. Biogenic components such as particulate carbon, particulate nitrogen, particulate volume, pigments, transparent exopolymer particles (TEP), and particulate amino acids in suspended particles and aggregates were followed over a period of 30 d. The overall pattern of decrease in organic matter, the amount of recalcitrant organic matter left after 30 d, and the compositional changes within particulate organic matter indicated that cells without a shell are more subject to loss than calcified cells. It is suggested that biogenic calcite helps in the preservation of particulate organic matter (POM) by offering structural support for organic molecules. Over the course of the experiment, half the particulate organic carbon in both calcifying and non-calcifying cultures was partitioned into aggregates and remained so until the end of the experiment. The partial protection of particulate organic matter from solubilization by biominerals and by aggregation that was observed in our experiment may help explain the robustness of the relationship between organic and mineral matter fluxes in the deep ocean.     

Analysis of ocean color spectra (III)

The spectral measurements of the attenuation coefficient of sea water and the absorption coefficient of suspended particles and of yellow substance were made with a spectrophotometer for the sea waters sampled in Tokyo Bay. These parameters can be used to compute the expected spectral irradiance reflectance. Some relationships between the optical properties of sea water and the concentration of dissolved organic carbon, the dry weight of suspended matter and chlorophyll-a concentration are presented. On the basis of these results, the possibility of modelling the relationship between optical and material properties is discussed.     

Application of data on seawater light scattering for the study of marine particles: a selective review focusing on Russian literature

This paper presents a selective review of applications of data on seawater light scattering for the study and monitoring of marine particles. Particular emphasis is placed on ocean waters and the seas surrounding Russia, where earlier studies by the author with his coworkers are little known because published mostly in Russian. In those assessments, methods of solving the inverse problem of seawater light scattering have been developed. Low-parametric models of optical properties were created by means of statistical analyses of experimental data, solving the inverse problem and comparing results derived from optical methods with those based on particle counts. Estimates of the volume and mass concentrations of suspended matter and its components were derived from light-scattering data for different regions. The potential of using optical methods for assessing spatiotemporal variability in suspended matter supply, propagation, and distribution is also considered.     

Rare earth elements in seawater during an iron-induced phytoplankton bloom of the western subarctic Pacific (SEEDS-II)

During an iron-enrichment experiment in the western subarctic Pacific (SEEDS-II), concentrations of dissolved and acid-soluble rare earth elements (REEs) were determined in shallow waters. Detailed vertical profiles of dissolved REEs were compared with those of nutrients in a preliminary survey. The results showed good correlation, except for Ce and Y. Along with phytoplankton growth within the iron-enriched patch, dissolved REEs were decreased in surface waters. The changes in REE concentrations were small but systematic: light REEs were adsorbed preferentially over heavy REEs. This systematic trend is consistent with results of earlier studies of REE adsorption onto biogenic particle surfaces. However, we were unable to detect a decrease of acid-soluble REEs in surface waters. During the phytoplankton bloom decline phase, dissolved REEs were elevated to concentration levels at the preliminary survey, although nutrients were decreased. The liberation of REEs from the suspended particles might be related to disaggregation from large particles to colloid particles, desorption from the particulate phase, and remineralization from organic matter. Outside the Fe-patch, time variations of REEs were also observed during SEEDS-II, indicating that both artificially induced phytoplankton blooms and natural variation of biogenic particles can affect the biogeochemical cycles of REEs in shallow waters within a short time.