Benthic foraminifera and bottom water evolution in the middle-southern Okinawa Trough during the last 18 ka

Changes of the deep-water circulation and chemicalcompositions in related water masses in the oceanshave played a significant role in the evolution of theglobal climate system[1].Many studies have shownthat the characteristics of the deep-water during theglaciations were distinctly different from that of to-day[2,3].In the northern Pacific,Duplessy et al.[4]foundthat the ventilation of the deep-water(at water depthbetween700―2600m)during the last glaciation wasstronger than that of today,and …     

The Impact of Snail (Bellamya aeruginosa) Bioturbation on Sediment Characteristics and Organic Carbon Fluxes in an Eutrophic Pond

A mesocosm experiment was conducted for 32 days in an eutrophic pond to study the effects of the bioturbation of the freshwater snail, Bellamya aeruginosa, on the benthic environment and to further understand cycling of organic carbon in water containing algal blooms. Chlorophyll‐a (chl‐a), phaeopigment, and organic matter contents of sediment, sediment oxygen consumption (SOC), and dissolved organic carbon (DOC) fluxes were determined on day 1, 16, and 32, respectively. The SOC decreased on day 16 and increased on day 32 significantly with the increase in snail density. DOC fluxes showed a net sediment uptake in all enclosures throughout the experiment. DOC fluxes in the high and mid density treatments were lower than those of the control. The concentrations of chl‐a and phaeopigment in the sediment increased significantly with snail density, indicating that the presence of snails reduced the biomass of phytoplankton. The results suggest that freshwater snails, B. aeruginosa, could influence the algal biomass (chl‐a) of small water bodies by their bioturbation effects on sediment characteristics and the fluxes of organic carbon.     

巢湖西湖心底泥蓝藻对水体蓝藻生物量的贡献

2018年10月-2019年10月对巢湖西湖心水体浮游藻类群落结构以及水体和底泥蓝藻生物量进行了月度调查.结果表明:巢湖西湖心浮游藻类的主要优势种属为微囊藻属、席藻属、十字藻、卵形隐藻和鱼腥藻属.蓝藻优势种属在5-10月为微囊藻属,11-12月为鱼腥藻属,1-4月为席藻属.巢湖水体和底泥蓝藻生物量峰值分别出现在9月和2月,水体蓝藻的衰亡下沉会导致底泥蓝藻生物量的上升.巢湖蓝藻主要分布在水体,底泥蓝藻生物量相对较低,单位面积水柱与底泥蓝藻生物量6月的比值大于100,在11-3月相对较低,最低值小于2.底泥蓝藻主要分布在底泥表层0～2 cm.通过安装原位捕获器,监测了蓝藻在西巢湖湖心水柱和底泥中的垂直迁移过程和通量.结果表明:11月和2月蓝藻有明显从水柱向底泥迁移的过程;底泥蓝藻全年向水体的静态迁移量都很低,而动态迁移在11月和6月出现两个峰值,主要受底泥蓝藻生物量和再悬浮的影响.本研究结果表明削减巢湖西湖心底泥种源的最佳时期为10月至来年2月,但是由于底泥蓝藻生物量远远小于水柱蓝藻生物量,底泥蓝藻向水体复苏迁移的通量也较低,即使削减了底泥种源,也不能有效降低水体蓝藻生物量.     

The Bay of Bengal — A major nutrient source for the deep Indian Ocean

The distribution of nutrient elements and dissolved oxygen in the deep Indian Ocean suggests that the Bay of Bengal Fan sediment serves as a major nutrient element source and oxygen sink. The distribution of nutrient element excesses and oxygen deficiences away from the fan is consistent with diffusion along isopycnal surfaces with circumpolar deep water acting as a sink for nutrient elements and source for dissolved oxygen. In the course of the entire GEOSECS program only at the Bengal Fan station were nutrient element excesses and oxygen deficiencies (relative to the overlying water column) observed in the benthic mixed layer. The unique aspect of this station is likely the result of very high rates of respiration and particle dissolution coupled with a high stability of the water column overlying the benthic mixed layer.The chemical data show that for each mole of organic carbon oxidized 1.5 moles of CaCO₃ must dissolve and that for each mole of CaCO₃ dissolved about one mole of silica go into solution. The NO₃ and PO₄ excesses are about two thirds those predicted from the Redfield ratios (i.e., O₂ : NO₃ : PO₄ = 135 : 15 : 1).     

Field studies on factors affecting very fine and ultra fine particulate organic matter deposition in low‐gradient sand‐bed streams

The knowledge on particle deposition in streams is mainly based on investigations in mountain streams. No data exist from low‐gradient sand‐bed streams that largely differ in the morphological and hydraulic factors proposed to affect deposition. To identify physical control on particle deposition in low‐gradient streams, we assessed deposition of very fine and ultra fine organic particulate matter in 18 sand‐bed stream reaches. We added particles derived from lake sediment and assessed the mean transport distance S_P and the deposition velocity v_dep. Additionally, reach hydraulics were estimated by injections of a conservative solute tracer (NaCl). Among the low‐gradient streams, particle deposition kinetics were variable but similar to deposition in mountain streams. S_P was solely related to the flow velocity. This relation was confirmed when comprising published data on deposition of fine organic particles. An association between particle deposition and transient storage factors was insignificant. We found significance of the transient storage to S_P only for repeated measures within a single reach, when flow velocity and benthic conditions were nearly constant. Measured v_dep/v_fall ratios were much larger than unity in most reaches. Evidence from this relation suggests that the vertical transport of very fine and ultra fine organic particulate matter through the water column was caused mainly by vertical mixing. Copyright © 2006 John Wiley & Sons, Ltd.     

Influence of macroinvertebrates on physico‐chemical and microbial processes in hyporheic sediments

The objective of this study was to measure the effects of invertebrates on the physical characteristics and microbial processes in hyporheic sediments. We investigated the impacts of an assemblage of three taxa (asellids, chironomid larvae, and tubificid worms) on sediment distribution, water fluxes, sediment organic carbon, biofilm (attached bacteria) characteristics, and O₂, dissolved organic carbon NO₃^?, NO₂^?, and NH₄⁺ concentrations in slow filtration sand–gravel columns. The results showed that invertebrates clearly modified the distribution of particles in the sediment column, probably because of the structures (tubes, macropores, and faecal pellets) produced by the three taxa in the sediment. Our assessment of water fluxes indicated that invertebrate activities led to an increase in the porosity of the sediment columns. In addition, aerobic (O₂ consumption) and anaerobic (denitrification and fermentative decomposition of organic matter) microbial processes occurring in the sediment were stimulated in the presence of invertebrates. Finally, the present study demonstrates that invertebrates can act as ecosystem engineers in heterogeneous sediments that are under the influence of an advective flux of water. The solute residence time increased in columns containing the faunal assemblage. Micro‐organisms used more dissolved organic matter and nutrients in the presence of invertebrates because invertebrate activities increased the contact between the biofilm and water. We conclude that engineering by invertebrates in natural conditions modifies characteristics of the hyporheic zone and thereby enhances both the porosity of the sediment and the solute transport across the benthic interface. Copyright © 2002 John Wiley & Sons, Ltd.     

Sedimentary inputs and oxygen uptake by the sediment in Lake Geneva (Switzerland)

Sediment cores and sediment traps were collected twice a month in two 35 m deep stations of Lake Geneva (Switzerland). The organic input sedimenting to the bottom is equal to 157 g C m⁻²y⁻¹ in station 1, to 214 g C in station 2. In spite of this difference, the oxygen uptake by the sediment (OUS) is similar in both locations (46–47 g C m⁻²y⁻¹). The oxygen uptake by the matter sedimenting to the bottom (OUSM) is respectively 45 g C m⁻²y⁻¹ and 41 g C in stations 1 and 2. The equivalence between OUS and OUSM implies that most of the sedimented matter arriving to the bottom is directly oxidized at the sediment surface. In station 1, OUS is positively correlated to OUSM, and OUSM is positively correlated to chlorophyll-a concentrations in the water column (0–20 m) one week before sediment sampling. In location 2, OUS is positively correlated to the percentage of organic carbon and nitrogen in the sedimented matter, negatively to its C:N ratio. Increasing allochthonous inputs have a negative influence on benthic respiration. At both sites, OUS is not directly related to macrobenthic biomass or to temperature of bottom water.     

湖泊污染底泥疏浚后新生沉积物-水界面溶解氧的动态响应

借助微氧电极测试技术对太湖贡湖湾试验区疏浚后的新生界面溶解氧动态进行一年的跟踪调研,分析溶解氧在新生微米级界面的分布特征、扩散通量以及界面附近有机质矿化速率.结果表明疏浚后半年内,溶解氧在表层沉积物的侵蚀深度增大,氧化层明显加厚.氧气在新生界面表层沉积物中呈指数下降,但衰减相对较缓.在连续一年的跟踪调查中发现,仅秋季新生界面附近溶解氧浓度明显高于对照,而在其他月份无差异.污染底泥疏浚后一个月内氧扩散通量及有机碳矿化速率下降最为明显,仅为疏浚前的13%,其他月份沉积物-水界面氧的扩散通量、氧气的消耗速率、有机碳的降解速率均有不同程度下降,疏浚后新生界面氧气交换速率下降以及由此导致的有机碳矿化过程变缓可能深刻影响界面生源要素的迁移过程.     

Bottom layer anoxia in the central part of the Gulf of Trieste in the late summer of 1983

Anoxic conditions in the near-bottom layer below the pycnocline were observed in September 1983 causing mass mortality of benthic macrofauna in the central part of the Gulf of Trieste. The vertical transport of particulate organic matter and decomposition of abundant pelagic and benthic organic matter during the summer produced a low oxygen level in the near-bottom layer below the pycnocline when this layer was sufficiently close to the bottom. A high sea water temperature and vertical stability contributed to the development of anoxic conditions in September 1983 in the near-bottom layer.     

Diatom thanatocoenosis in a middle Galician Ría: Spatial patterns and their relationship to the seasonal diatom cycle in the water column and hydrographic conditions

Modern diatom distribution patterns in the surface sediment of the Ferrol Ría and their relationship to the hydrography and diatom patterns in the water column were studied to determine the hydrographic influence on the record of these biogenic components. Diatom abundance in the water column was assessed for different oceanographic periods and compared with the biosiliceous sedimentary record. Very low abundances were found in the water column during the winter, whereas in spring and summer, diatoms proliferated. Chaetoceros spp. formed the bulk of the water column community during spring and summer, followed by Thalassionema nitzschioides and Rhizosolenia spp. Nitzschia longissima represented a significant portion of the winter assemblage, together with Paralia sulcata and benthic taxa. Leptocylindrus danicus, N. longissima and Skeletonema costatum characterized the autumn campaign, when stratification of the waters occurs, with L. danicus being especially abundant in the outer ría.Seasonal hydrographic and associated productivity patterns govern the abundance and assemblage of the diatoms preserved in surface sediments. Samples located in the inner ría area and its margins exhibited the highest abundances of diatoms, and were primarily dominated by benthic species. The freshwater group, crysophycean cysts and phytoliths were present in the landward stations influenced by river runoff. The middle ría was characterized by P. sulcata and Thalassiosira spp., with minor occurrences of the benthic and freshwater group. Chaetoceros R.S., L. danicus R.S. and T. nitzschioides typified the outer ría, an assemblage that corresponds to nutrient-rich coastal areas of high productivity influenced by oceanic waters, demonstrating the impact of oceanic waters flowing into the embayment due to enhanced tidal mixing through the narrow channel. Therefore, sediment diatom assemblages reflect diatom production patterns in the water column of the Ría. However, we must proceed with caution when interpreting the paleorecord in the inner area due to the high contribution of allochthonous taxa, which is indicative of low water depths. This paper contributes to a better understanding of diatom thanatocoenosis in the Galician Rías, where very few studies of this kind have been done to date.     

Consequences of spring phytodetritus sedimentation on the benthic compartment along a depth gradient in the Eastern English Channel

Phaeocystis blooms are of major importance in the Eastern English Channel, where they significantly contribute to spring organic matter input with chlorophyll concentrations commonly higher than 30 microgl(-1) in the water column. Post-bloom deposition of Phaeocystis derived mucilaginous compounds has been shown to have a major importance on benthic intertidal systems, but resulting mineralization processes and consequences on the macrobenthic compartment remain poorly documented in subtidal areas. In this frame, a study was performed along the French coast of the English Channel to quantify mineralization processes, as well as potential consequences on subtidal sediments, especially their geochemistry and associated macrofaunal communities. Seven stations were studied along a depth gradient during four cruises: before (March), during (April, May) and after (June) the spring bloom. Sediment characteristics and organic carbon content were described, as well as sediment-water fluxes of oxygen and ammonium. Macrofaunal characteristics were also analyzed. Stations were chosen as representative of the various benthic communities present in the area, which are directly linked to the granulometric characteristics of the sediments. To account for the general functioning of the water column, characterized by a coastal flow where higher concentrations of Phaeocystis are generally recorded, similar communities were sampled inshore and offshore, when possible: (i) the Abra alba community located only close to the coast, (ii) the Ophelia borealis community located inshore and offshore, and (iii) the Amphioxus lanceolatus community located inshore and offshore. Generally, low exchange rates of oxygen and ammonium were measured (respectively, in the range 50-150 micromol O2 m(-2)h(-1) and -25 to 35 micromol NH4+ m(-2)h(-1)) between the water column and the muddy-sand to coarse sand permeable sediments, as a consequence of the low organic carbon content due to the high hydrodynamic forcing. As a consequence of organic matter accumulation in surficial sediments probably resulting from Phaeocystis post-bloom deposition, an increase of sediment oxygen demand and ammonium release was clearly evidenced up to 660 micromol O2 m(-2)h(-1) and 205 micromol NH4+ m(-2)h(-1) in May, only in stations located close to the coast (<8 kms), in the A. alba community. Despite those significant biogeochemical changes in surficial sediments, no significant consequence was pointed out on macrofauna, neither in the O. borealis and A. lanceolatus communities, nor in the coastal A. alba community. Most of the temporal variations recorded might be attributed to the common spring population dynamics, but this study highlights the potential use of geochemical parameters as a forewarning signal of benthic disequilibrium.     

Coupling Suspension Feeders to the Chesapeake Bay Eutrophication Model

A model predicting suspension-feeding bivalve biomass and its interactions with water quality has been developed and coupled with the Chesapeake Bay Eutrophication Model. This coupling included deposition of filtered particulate matter to the sediments and the recycling of inorganic nutrients back to the water column. Because individual size is a crucial determinant of bivalve filtration and respiration rates, an empirical function, was developed from data, relating computed areal biomass to size, which was then used to adjust these rates during the simulation. Biomass was strongly related to the eutrophication model's predictions of organic and total solids distributions, as well as to bottom water dissolved oxygen. The tight coupling between seasonal organic matter concentration and biomass suggested that food, or the ability of suspension feeders to ingest it given present total solids loadings, is a limiting factor baywide. Hypoxia and anoxia also reduced benthic biomass in affected locations. High site-specific temporal variability observed in the data may contain a large component of spatial patchiness, on scales below which the present estuarine eutrophication model could resolve. Further insights will be needed to incorporate the effects of patchiness, as well as other important spatial and temporal signals, such as predation and recruitment.     

兴凯湖春季水体悬浮颗粒物和CDOM吸收特性

为了分析兴凯湖水体光学活性物质的吸收特性、来源和空间分布以及对400~700 nm范围内总吸收的贡献,于2013年5月对该水体进行野外实验,对水体中浮游藻类、非藻类颗粒物和有色可溶性有机物的吸收特性和水质参数进行测定.结果表明:总悬浮颗粒物的吸收光谱与非藻类颗粒物相似,色素颗粒物含量较少且单一,非藻类颗粒物在总悬浮颗粒物吸收中占主导地位,其贡献率始终在50%以上.CDOM吸收曲线的拟合函数斜率值Sg均高于其它水体.440 nm处总悬浮颗粒物和非藻类颗粒物的吸收系数ap(440)、ad(440)与总悬浮颗粒物、无机悬浮颗粒物和有机悬浮颗粒物浓度相关性均较好,与叶绿素a(Chl.a)浓度的相关性较差.兴凯湖与其它Ⅱ类水体的差异性表现在440 nm处CDOM吸收系数ag(440)与Chl.a浓度、溶解性有机碳(DOC)浓度均无显著相关性,说明DOC以无色部分为主.总体上,大兴凯湖各吸收系数和水质参数均值均低于小兴凯湖,后者水质受农耕区退水及周围渔业、旅游业的影响较大.     

Late Cretaceous paleoenvironment and lake level fluctuation in the Songliao Basin,northeastern China

Study of Late Cretaceous lacustrine sedimentary strata in the eastern Songliao Basin, China revealed that the paleoclimate was relatively arid and hot during sedimentation of the upper Santonian of the Yaojia Formation, but became relatively humid and warm during deposition of the lower Campanian Nenjiang Formation. The upper Yaojia Formation was deposited in a freshwater lake environment, while the lower Nenjiang Formation was deposited in a slightly brackish to brackish environment. The average total organic carbon content in the upper Yaojia Formation is 0.15%, while the hydrogen index is 36 mg_HC/g_TOC, implying poor source rock for oil generation and the organic matter comprised of a mixture of woody and herbaceous organic matter. In contrast, the hydrogen index of oil shale and black shale of the lower Nenjiang Formation is 619 mg_HC/g_TOC, and total organic carbon content on average is 3.37%, indicating a mixed algae and herbaceous source of kerogen and an increase in aquatic bioproductivity. The black shale and oil shale have low Pristane/Phytane and C₂₉ 5α,14α,17α(H) ? stigmastane 20R/(20R + 20S) ratios, with maximum concentration of n‐alkanes at n‐C₂₃, implying an anoxic depositional environment with algae, bacteria and higher plants providing most of the organic matter. Relatively abundant gammacerane and a higher Sr/Ba ratio in the oil shales suggest the presence of brackish water and development of salinity stratification in the lake. During sedimentation of the upper Yaojia through the lower Nenjiang Formations, the level of Songliao lake increased and a deep‐lake environment was formed with bottom waters being oxygen depleted. Concomitantly, as the lake deepened bottom conditions were changing from oxic to anoxic, and the input of organic matter changed from predominantly higher plants to a mixture of bacteria, algae and higher plants providing favorable conditions for oil source rock accumulation.     

Bacteria and organic matter dynamics during a bioremediation treatment of organic-rich harbour sediments

We studied the dynamics of bacteria and organic matter in the Ancient Port of Genoa (Italy) during a bioremediation treatment of sediment (during summer-autumn 1998) in an area characterised by continuous sewage discharge. A strong increase in total benthic bacterial density (TBN) was recorded at the end of the study, from 14 x 10(8) to 58-172 x 10(8) cell g(-1) in different parts of the treated area. The TBN increase was linked to organic matter depletion, from more than 40 to less than 20 mg x g(-1). In order to highlight the main ecological mechanisms involved in bioremediation, a laboratory experiment based on both water and sediment from the basin studied was carried out. We observed an increase in TBN during the first 20 days and a decrease in sediment organic matter (up to about 20%). Increases of organic matter (about 2-fold) and TBN (from 21 to 33 x 10(9) cell l(-1)) occurred in the overlying water, suggesting a strong association between the sediments and water column processes. Hydrolytic activities, which double in the sediment and increase up to a 300-fold in the water, are consistent with the decrease in sediment organic matter and with the water fraction dynamics.     

近40年来太湖梅梁湾底栖动物群落演变特征及驱动因素

梅梁湾是太湖北部最大湖湾,也是太湖生态环境问题最严重的区域之一,近年来对太湖治理力度不断加大,然而对其生态状况演变的认识尚不清晰。本文基于长期监测及文献资料,获得1980s以来太湖梅梁湾底栖动物及环境因子数据,分析底栖动物种类组成、优势种、丰度的时空变化,应用非度量多维尺度分析(NMDS)和随机森林(RF)分析群落结构演变及其与环境因子的关系。结果表明,梅梁湾1980—2019年共记录到44属(种)底栖动物,以摇蚊幼虫和软体动物为主,总丰度年际变化显著,40年来底栖群落结构发生显著变化,优势种经历了由较敏感的软体类为主到以耐污寡毛类、摇蚊幼虫等为主的转变。综合NMDS和随机森林分析结果,梅梁湾底栖动物群落演变大致可分为4个阶段:1980s及以前,物种多样性丰富,以河蚬(Corbicula fluminea)等大型软体动物为优势种;1990s—2007年,底栖动物群落快速退化,以耐污种占优;2008—2016年,水生态略有恢复,河蚬等清洁种略有回升;2017—2019年,耐污种优势度和丰度反弹。近40年来梅梁湾底栖动物群落变化主要受底质氮磷、有机质和水体营养盐、蓝藻水华等环境因子变化的影...     

Responses of benthic macrofauna and biogeochemical fluxes to various levels of mussel biodeposition: An in situ “benthocosm” experiment

An in situ experiment was done to evaluate the dose-dependent response of mussel biodeposition on benthic communities and biogeochemical fluxes. Natural benthic communities were exposed to 7 different levels of mussel biodeposition (equivalent to that produced by 0-764 mussels m⁻²) over 50 days. Benthic communities responded as predicted from the Pearson, T.H., Rosenberg, R., 1978. Macrobenthic succession in relation to organic enrichment and pollution of the marine environment. Oceanogr. Mar. Biol. Annu. Rev. 16, 229-311 model of organic enrichment. Total abundance and species richness decreased with increasing biodeposition. The abundance and biomass of opportunistic species (Capitella spp.) increased in the mesocosms subject to the greatest biodeposition. Sensitive species Tellina agilis and Pherusa plumosa tended to decrease in abundance and biomass with increasing biodeposition. The biotic index M-AMBI responded clearly to increased biodeposition and may be a useful tool for assessing the effect of mussel biodeposition on the benthic environment. These results are important for the construction of predictive models for determining environmental carrying capacity for bivalve aquaculture.     

Effects of pollen leaching and microbial degradation on organic carbon and nutrient availability in lake water

Nutrient fluxes across terrestrial-aquatic boundaries and their subsequent integration into lake nutrient cycles are currently a major topic of aquatic research. Although pollen represents a good substrate for microorganisms, it has been neglected as a terrestrial source of organic matter in lakes. In laboratory experiments, we incubated pollen grains of Pinus sylvestris in water of lakes with different trophy and pH to estimate effects of pollen input and its subsequent microbial degradation on nutrient dynamics. In this ex situ experiment, we measured concentrations of organic carbon, phosphorus and nitrogen in the surrounding water as well as microbial dynamics (bacteria and fungal sporangia) at well-controlled conditions. Besides leaching, chemical and microbial decomposition of pollen was strongest within the first week of incubation. This led to a marked increase of soluble reactive phosphorus and total dissolved nitrogen (up to 0.04 and 1.5 mg L⁻¹, respectively, after 5 days of incubation) in the ambient water. In parallel, pollen grains were rapidly colonized by heterotrophic bacteria and aquatic fungi. Leaching and microbial degradation of pollen accounted for ≥80, ≥40, ≥50% for organic C, N and P, respectively, and did not significantly differ among water samples from the studied lakes. Thus, pollen introduces high amounts of bio-available terrestrial organic matter and nutrients into surface waters within a short time. A rough calculation on P input into oligotrophic Lake Stechlin indicates that pollen plays an important ecological role in nutrient cycling of temperate lakes. This requires further attention in aquatic ecology.     

Application of Hydrophobic Interaction Chromatography (HIC) in Water Analysis Anwendung der Hydrophobizitätschromatographie (HIC) in der Wasseranalytik

Dissolved high molecular weight organic substances, like humic substances, can be characterized with regard to their molecular weight distribution using gel filtration chromatography (GFC). In addition, the adsorption properties, for example on activated carbon, can be described, if the substances are separated by hydrophobic interaction chromatography (HIC) in different fractions using a chromatographic column with a hydrophobic matrix. The retention time (Rt) of single chemical substances in this column can be used to characterize the hydrophobicity or hydrophility of each compound as well as of the high molecular weight organic matter. The hydrophobic interaction between the matrix of the column and the dissolved chemical compounds also depends on the hydrophobicity of the gel and the composition of the eluent. Relations between retention times, log P-coefficients (octanol/water partition) and K-values of isotherms on activated carbon (Freundlich equation) were found.