Interaction between water flow and oxygen deficiency on growth in the infaunal brittle star Amphiura filiformis (Echinodermata: Ophiuroidea)

Interactions between ‘oxygen concentration’ (normoxia: >80% oxygen saturation, and hypoxia: 18% oxygen saturation) and ‘water flow velocity’ (low: 0.1 cm s⁻¹, and moderate: 0.5 cm s⁻¹) were studied on growth rates in the brittle star Amphiura filiformis in a flow-through aquaria system. Effects of ‘sublethal predation’ on growth rates were investigated as ‘number of amputated arms’ (1 and 3 arms) and ‘amputation of the disk’. A significant interaction between oxygen concentration and water flow velocity was observed in mean arm regeneration rate, but in both flow velocities higher mean arm regeneration rates were observed in normoxia compared to hypoxia. In hypoxia a positive response in arm regeneration rate was observed in moderate flow compared to low flow velocity. In normoxia, however, no response to flow velocity was observed. The latter observation indicates that Amphiura filiformis is able to maintain the ventilation of the burrow at low flow velocities, but in low oxygen concentrations hydrodynamic forces seem to affect growth. A significant interaction between oxygen concentration and disk amputation was observed in both arm and disk regeneration rates, indicating that the disk is the major organ for gas exchange in this species. The number of arms amputated, however, did not affect mean arm regeneration rate. The results obtained in this study suggest that the secondary production in subtidal infaunal populations could be negatively affected by low oxygen concentrations and that this response is even more negative in combination with low flow velocities in the near-bottom water.     

长江口和东海海域沉积物粒径对有机质分布的影响

利用2007年11月采集于长江口和东海陆架区域的78个站位的表层沉积物样品,以及2007年11月、2008年4月采集于长江口东南和浙江近岸泥质区的悬浮物样品,对长江口和东海海域表层沉积物以及部分站位的悬浮物进行了粒度、有机碳和总氮的分析和研究,探讨了沉积物粒径对有机质运移和沉积过程的影响.结果表明:(1)水体中悬浮物的...     

Effects of sediment organic matter quality on bioaccumulation, degradation, and distribution of pyrene in two macrofaunal species and their surrounding sediment

Sediment dwelling macrofauna (infauna) are important vectors for the transfer of sediment-associated contaminants to higher trophic levels. Sedimenting organic matter constitutes an important food source for all benthic organisms and changes seasonally in terms of quantity and quality. Sediment organic matter (SOM) quality affects organism activity and feeding behaviour, and is therefore also likely to affect contaminant fate in benthic systems. We investigated the impact of SOM quality (enrichment with either labile Tetraselmis sp. or refractory lignin) on the accumulation and metabolism of sediment-associated pyrene in Nereis diversicolor (Annelida) and Amphiura filiformis (Echinodermata), as well as the combined effect of SOM quality and infaunal bioturbation on pyrene distribution and metabolism in the sediment. After 45 d of exposure, SOM quality almost doubled pyrene bioaccumulation in both species, while pyrene metabolism remained unaffected. Metabolites comprised approximately 80% of the total tissue pyrene in N. diversicolor and approximately 40% in A. filiformis. A. filiformis arms contained one fifth of the disk pyrene concentration. Approximately 20% of the pyrene found in A. filiformis arms was found to be covalently bound to, e.g. DNA, RNA or proteins, thus reducing pyrene bioavailability to arm-cropping predators. The sedimentary pyrene distribution and metabolism was species-dependent, but correlated poorly with prevailing knowledge on species-specific bioturbation patterns. This was attributed to the comparably high biodegradability of the contaminant thus altering its sorptive characteristics and function as inert tracer. Subduction of pyrene and metabolites occurred, and the fraction of pyrene covalently bound to SOM increased with depth, thereby removing pyrene from the bioavailable pool. Our results imply that bioaccumulation and trophic transfer of sediment-associated PAH should increase following fresh organic matter input, e.g. after sedimentation of phytoplankton blooms. We stress the importance of considering behavioural characteristics of infauna and the trophic situation of the system when assessing fate and effects of sediment-associated contaminants.     

Degradation rates of organic matter in the sediment of Mikawa Bay

Sedimentary core samples were collected from Mikawa Bay and analyzed for organic C, N and P, carbohydrate and protein including amino acids. Sedimentation rates for each of the core samples were found to lie in the range of 0.21–0.24 g cm^–2yr^–1 by the²¹⁰Pb method. Degradation rate constants of organic C, N and P, carbohydrate and protein including amino acids had ranges of 3.8–5.5, 4.7–5.9, 6.3–7.4, 5.7–6.8 and 3.9–6.8×10^–2yr^–1, respectively. The rate of degradation of organic matter in the sediment was also calculated and is discussed in relation to the flux of particulate organic matter to the surface of the sediment.     

Impact of halides on the photobleaching of dissolved organic matter

Understanding absorbance photobleaching of marine dissolved organic matter (DOM) is important because DOM chromophores impact oceanic primary productivity by affecting the depth of the photic zone, absorb UV radiation and affect ocean color used in remote sensing. However, the fundamental mechanisms which account for this bleaching are largely unknown. Controlled laboratory studies demonstrated that the presence of seawater concentrations of chloride and bromide ions enhanced absorbance photobleaching reaction rates by ~ 40%, regardless of DOM source or the presence or absence of carbonate ions. In contrast, halide ions generally did not affect fluorescence bleaching rates. Variations in ionic strength did not alter the enhancement in absorbance photobleaching by halide ions. Accordingly, the enhancement in absorbance photobleaching was specific to halide ions, rather than a generalized salinity effect. We confirmed the formation of hydroxyl radical (HO^•) in illuminated samples, and its significant scavenging in the presence of halide salts. Gamma-radiolysis experiments and associated modeling indicated that a small component (~ 12%) of the photobleaching enhancement by halides was consistent with the hypothesis that halide scavenging of HO^• will form reactive halogen radicals that target electron-rich chromophores within DOM more selectively than HO^•. The mechanism responsible for the major component of absorbance photobleaching rate enhancement by halides remains unresolved.     

The fate of terrestrial organic matter in two Scottish sea lochs

Sea lochs are zones of rapid organic matter (OM) turnover. Most of this OM is of allochthonous origin, being introduced into the lochs via freshwater input. In this study the behaviour of terrestrially derived OM was elucidated using a combination of parameters which indicate OM diagenesis in the near surface sediments from two Scottish sea lochs, Loch Creran and Loch Etive. Alkaline CuO oxidation was used to determine lignin phenols which serve as biomarkers for terrestrial OM in sediments. Stable carbon isotope, total carbon and nitrogen and total OM (including the labile and refractory fractions) compositions were also determined.     

Variations in the composition of particulate organic matter in a time-series sediment trap

A time-series sediment trap was used to collect material for organic geochemical analyses as part of the Sediment Trap Intercomparison Experiment. The flux of particulate matter was more likely related to a change in current direction during the course of the experiment than to small-scale changes in surface productivity. Of the compounds measured, the n-alkanes reflected this change most dramatically, decreasing with the change in current direction.Amino acid and lipid components were measured in the samples. Amino acids made up 15–35% of the total organic carbon flux and 35–75% of the total organic nitrogen flux collected in the traps. Specific amino acids indicative of bacterial biomass or activity suggested that microbial growth occurred in the traps, probably as a result of incomplete poisoning by NaN₃. However, the effect of this growth on the bulk composition of particulate matter appeared to be minimal.The amino acid distribution of particulate organic material collected by large volume filtration (LVF) was not significantly different from the sediment trap material, except that the LVF material did not appear to be affected by bacterial growth.     

Differential sorption of organic matter by various sized sediment particles in recent sediment from the bering sea

A recent unconsolidated marine sediment collected from the Aleutian basin of the Bering Sea (5702.9N, 17657.4W) was separated into eight size fractions by sieving. Each of the fractions was analyzed for density, organic carbon, total nitrogen and various organic materials. A detailed analysis of the correlation of organic carbon and total nitrogen to the mean diameter of the particles separated, indicated that the surface sorption processes of organic matter were the determinative factor controlling the concentration of organic carbon and total nitrogen on silt and clay particles of the sediments.Selective sorption of amino acids was found to occur in the 8–20 and 5–8m. fractions of the sediment. This is assumed to be due to their surface active property.     

Transport and fate of Danube Delta terrestrial organic matter in the Northwest Black Sea mixing zone

Within the framework of the European project EROS 21, a biogeochemical study of particles transported from the Danube Delta to the Northwestern Black Sea whose carbon cycle is dominated by riverine inputs was carried out in spring off the Sulina branch of the Danube Delta. The distribution of particulate organic carbon (POC), chlorophyll a (Chl a), C/N, and δ¹³C evidenced an omnipresent contribution of terrestrial organic matter throughout the study area together with a dilution of these inputs by freshwater and marine organisms. Four lipid series, n-alkanoic acids, n-alkanes, n-alkanols, and sterols were analyzed by gas chromatography and gas chromatography/mass spectrometry. Several signature compounds were selected to delineate dispersion of terrestrial organic carbon: (1) long-chain n-alkanoic acids in the range C₂₄–C₃₄, long-chain n-alkanes in the range C₂₅–C₃₅, long-chain n-alkanols in the range C₂₂–C₃₀, 24-ethylcholesta-5,22-dien-3β-ol (29Δ^5,22) and 24-ethylcholesterol (29Δ⁵) for vascular plant-derived material and (2) coprostanol (27Δ^0,5β) for faecal contamination associated with sewage effluents. A marked decrease was observed between the concentrations of different vascular plant markers characterizing the two end members: riverine at salinity 0.3 and marine at salinity 15.5. The decrease observed for marine/riverine end members (expressed as a function of organic carbon) varied in a large range, from 4% for n-alkanes to 18.6%, 20.4% and 24% for n-fatty acids, n-alkanols and sterols, respectively. These values reflect a combination of various processes: size-selective particle sedimentation, resuspension of different particle pools of different sizes and ages, and/or selective biological utilization. The multi-marker approach also suggested the liberation in the mixing zone of terrestrial moieties, tightly trapped in macromolecular structures of the riverine material. The greatest decrease for marine/riverine end members was observed for coprostanol (0.9%), underlining the efficiency of the mixing zone as a sink for sewage-derived carbon.     

A note on the relationships between organic matter and some geotechnical properties of a marine sediment

Abstract

An analysis of the relationship between organic matter and liquid and plastic limits, and grain‐specific gravity of a marine sediment was accomplished by making a stepwise adjustment in the organic content of that sediment. The sample used was from Santa Barbara Basin (off southern California) and is typical of fine‐grained marine sediments: it is a clayey silt with a common suite of minerals and other constituents. During the experiment, texture and composition (except organic content) were constant; only the quantity of natural, indigenous organic matter was changed.

A strong linear relationship exists between the independent variable, the amount of organic carbon present in the sample, and the dependent variables. Liquid limit, plastic limit, and plasticity index all increased with increasing organic content over the range studied (0.57–3.20% organic carbon). Grain‐specific gravity decreased. All had linear correlation coefficients (r) greater than |0.90| and r ² values greater than 90%, except the plasticity index (83%).

Comparing the results of regression analyses from this and several similar studies shows that although there is good qualitative agreement, there are quantitative inconsistencies. In particular there is considerable overall variability in the regression coefficients. Among studies on marine sediments the inconsistencies are less pronounced, yet still evident. The increase in liquid limit as organic carbon increased by 1 % sediment dry weight ranged from 9 to 28% water content; in the plastic limit the range was from 4 to 18%. However, in these marine studies regression coefficients are relatively close in value in some cases, levels of significance of the regressions are high in most cases, and in all cases the relationships appear to be linear over the range of organic carbon percentage studied. Finally, we believe that a relatively clear relationship between plasticity and organic carbon begins to emerge when the latter exceeds a value of 2%.     

Temperature effects on uptake and retention of contaminant radionuclides and trace metals by the brittle star Ophiothrix fragilis

Recent revelations of extensive dumping of radioactive wastes in Arctic seas emphasize the need to understand the processes affecting accumulation of contaminants in polar marine food webs. Little is known, however, about the effects of low temperatures on bioaccumulation of radionuclides and toxic metals. To address this question, we examined the effects of temperature on uptake and retention of 11 dissolved radioisotopes (including both nuclear waste components and required, and toxic metals) by the brittle star Ophiothrix fragilis, typical of species which dominate Arctic benthic communities. Lower temperatures significantly reduced uptake rates of all elements examined, but had little effect on loss rates. These results raise questions about the validity of extrapolating previous work on biological dynamics of dissolved contaminants, largely carried out at temperate zone temperatures, to polar ecosystems. This work suggests that the effects of low Arctic temperatures may need to be taken into consideration in order to understand the potential for food chain accumulation of nuclear wastes and toxic metals in high-latitude seas.     

Effect on marine sediment nitrogen fluxes caused by organic matter enrichment with varying organic carbon structure and nitrogen content

Enrichments with five types of organic carbon, differing in nitrogen content and type of organic carbon, were made to a marine sediment in order to study effects on nitrogen fluxes. The enrichments used were Ulva lactuca, Ascophyllum nodosum, Zostera marina, Ceratium spp., lignin, and mixtures of U. lactuca and A. nodosum. Fluxes of ammonium, nitrate, and phosphate were measured in short-term (48 h) microcosm experiments, using a carbon enrichment loading similar to that at the sampling site. Changes in microbial community growth and structure due to three types enrichments were also detected using molecular methods in a microcosm experiment run for 4 days to allow for detection at DNA-level.Ammonium fluxes changed from an efflux in the control to an influx for all enrichments apart from U. lactuca. The change was significantly related to the added material's C:N ratio when Ceratium spp. was excluded. All enrichments induced an influx of nitrate suggesting the formation of anoxic micro zones, but there was no relationship with C:N ratio. Instead, the magnitude of the nitrate influx is suggested to be related to the structure of the organic carbon, where enrichments containing a large pool of cellulose and lignin (Z. marina and lignin) gave rise to a lower influx, compared to algal material with more easily degraded organic matter like lipids and starch, which induced the highest influx of nitrate (Ceratium spp., U. lactuca, and A. nodosum). The occurrence of an ammonium influx together with increased nitrate influx and a lower efflux of phosphate in the enrichments suggests a growth of heterotrophic bacteria. This was also confirmed using molecular methods (PCR-DGGE) where the relative abundance of bacterial species in the enrichments increased.The sum of ammonium and nitrate fluxes showed that total nitrogen removal was enhanced in all enrichments compared to the nonenriched control sediment, but in different ways. Ceratium spp. induced the highest removal followed by A. nodosum, U. lactuca, Z. marina, and lastly, by lignin. The same pattern was observed also in a second experiment. These results indicate that easily degradable organic carbon, together with a lower C:N ratio of the added material, will remove nitrogen from the water phase, making the recycling of nitrogen to the overlying water mass smaller.     

北极孔斯峡湾表层沉积物中溶解有机质的来源与转化历史

在北极地区孔斯峡湾采集28个表层沉积物样品,测定了其中水溶性有机质(也称溶解有机质,DOM)的分子量分布、紫外/可见吸收光谱和三维荧光光谱特征,并利用平行因子分析(PARAFAC)模型对DOM的荧光组分和来源进行了解析。结果表明:孔斯峡湾表层沉积物中有色溶解有机质(CDOM)及其中的荧光溶解有机质(FDOM)含量均从内湾向外湾方向呈逐渐累积的趋势,但CDOM中的FDOM所占比例逐渐减小,与DOM趋于老龄化密切相关。沉积作用减弱以及长期的光化学降解和微生物降解作用对此起主要贡献,并导致腐殖质和小分子组分在沉积物DOM中所占的比例呈逐渐递增的趋势。沉积物DOM包含陆源类腐殖质、自生源类腐殖质和类蛋白等三个荧光组分,但是其组成比例空间差异很大。吸收光谱斜率比(S_R)随自生源所占百分比增加而减小,随DOM腐殖质组分中陆源与自生源的比值增加而增加;腐殖化指数(HIX)随类腐殖质与类蛋白质比值和水深的增加而增加,生物源指数(BIX)随自生源比例增加而增加。峡湾沉积物DOM的组成和来源存在着高度的空间差异,在冰川湾区由水体颗粒有机质(POM)的近期转化和迁移而来,而在峡湾中央及口门附近以较老的腐殖质为优势,主要源于水体DOM长期迁移和转化。研究表明,FDOM/CDOM,S_R,HIX和BIX等构成的CDOM光谱指纹信息可以作为揭露沉积物溶解有机质来源及迁移转化历史的工具,对探索海洋与冰川相互作用影响下的峡湾环境演变有着重要意义。     

Some characteristic features of the vertical profile of organic matter in recent sediment from the Bering Sea

Sedimentary samples were collected from a site (57°02.9N, 176°57.4W: 3,650 m) in the Aleutian Basin of the Bering Sea and analyzed for organic carbon, total nitrogen and various organic materials. Organic carbon and total nitrogen were measured in the range of 0.1–1.9% and 0.01–0.2% of the dry weight of the sediment, these values tended to decrease with depth, but considerably lower values were obtained in the volcanogenic sediment layers. Carbohydrate, amino acid and protein and lipid carbons accounted for 40% of the total organic carbon on the surface of the sediment, and this value tended to decrease with depth to 20% at 10m depth from the top of the core sample. The carbon to nitrogen (C/N) ratios ranged from 6.3 to 9.0. Vertical change in the values of the ratios can be understood in terms of a higher decay rate of amino acids and proteins.Radiocarbon age determinations on five sedimentary samples yielded sedimentation rates ranging from 37 to 90cm/1,000y.     

Distribution and quality of sedimentary organic matter on the Aquitanian margin (Bay of Biscay)

During the ECOFER experiment (French ECOMARGE program), surficial sediments were sampled on the Aquitanian margin with box corers and analyzed to determine the quantity and quality of organic matter. Sediments from the margin are enriched in organic carbon (mean value 1.35%) in comparison to deep-sea and shelf sediments, due to a fine grain-size sedimentation. As sedimentation rates are high, the margin appears to be an organic depocenter. Some preferential organic enrichment zones were identified in the Cap-Ferret Canyon. There is a supply of continental material from the Gironde estuary, but marine contribution seems more possible than Adour or spanish rivers. No seasonal variations of organic matter were observed at the surface of sediments, suggesting mineralization processes of labile organic matter: average organic carbon consumption was evaluated to 9.0 g C m⁻² yr⁻¹. Rapid biological mineralization processes are lower than on the Mediterranean margin, mainly related to significant differences in water temperature. The great width of the canyon, its distance from the continent, and the current circulation pattern prevent any precise recording of the variable organic inputs to the sediment and favor nepheloı̈d transport, resuspension and shelf break processes, which wipe out any print of fresh material input. An organic carbon budget indicates that an equilibrium between organic inputs and organic mineralization+accumulation is not obtainable. The supply of suspended matter could have been minor during the year in question, and sedimentation rates are still imprecise.     

Seasonal variations of dissolved organic matter and nutrients in sediment pore water in the inner part of Tokyo Bay

At four stations in Tokyo Bay, pore water profiles of dissolved organic carbon (DOC), nitrogen (DON), phosphorus (DOP), and inorganic nutrients were determined at 3-month intervals over 6 years. Concentrations of dissolved organic matter (DOM) and nutrients were significantly higher in pore waters than in the overlying waters. Pore water DOC, DON, and DOP concentrations in the upper most sediment layer (0–1 cm) ranged from 246 to 888 μM, from 14.6 to 75.9 μM, and from 0.02 to 9.83 μM, respectively. Concentrations of DOM and nutrients in pore waters occasionally showed clear seasonal trends and were highest in the summer and lowest in the winter. The seasonal trends in the pore water DOM concentrations were coupled with trends in the overlying water temperature and dissolved oxygen concentration. Benthic effluxes of DON and DOP were low compared with those of inorganic nutrients, accounting for only 1.0 and 1.5 % of the total benthic effluxes of nitrogen and phosphorus, respectively; thus benthic DOM fluxes were quantitatively insignificant to the inorganic nutrient fluxes in Tokyo Bay. The DOM fluxes represented about 7, 3, and 10 % of the riverine discharge of DOC, DON, and DOP to Tokyo Bay, respectively.     

The effects of dissolved organic matter on the aqueous partitioning of polynuclear aromatic hydrocarbons

The partitioning of six polynuclear aromatic hydrocarbons into aqueous solutions containing dissolved organic matter from various coastal environments was investigated by liquid chromatography. Specific hydrocarbon-organic matter interactions were observed. The greatest interactions occurred with the very low solubility hydrocarbons and with organic matter of terrestrial origin. Ultrafiltration experiments suggested that it was the relatively high (greater than approximately 500) molecular weight organic matter that was interacting with the hydrocarbons.     

Particulate organic matter and ballast fluxes measured using time-series and settling velocity sediment traps in the northwestern Mediterranean Sea

Prompted by recent data analyses suggesting that the flux of particulate organic carbon sinking into deep waters is determined by fluxes of mineral ballasts, we undertook a study of the relationships among organic matter (OM), calcium carbonate, opal, lithogenic material, and excess aluminum fluxes as part of the MedFlux project. We measured fluxes of particulate components during Spring and Summer of 2003, and Spring of 2005, using a swimmer-excluding sediment trap design capable of measuring fluxes both in a time-series (TS) mode and in a configuration for obtaining particle settling velocity (SV) profiles. On the basis of these studies, we suggest that distinct OM–ballast associations observed in particles sinking at a depth of 200 m imply that the mechanistic basis of the organic matter–ballast association is set in the upper water column above the Twilight Zone, and that the importance of different ballast types follows the seasonal succession of phytoplankton. As in other studies, carbonate appears to enhance the flux of organic matter over opal. Particles must be at least half organic matter before their settling velocity is affected by ballast concentration. This lack of change in ballast composition with SV in particles with <40% OM content suggests that particle SV reaches a maximum because of the increasing importance of inertial drag. Relative amounts of OM and opal decrease with depth due to decomposition and dissolution; carbonates and lithogenic material contribute about the same amount to total mass, or increase slightly, throughout the water column. The high proportion of excess Al cannot be explained by its incorporation into diatom opal or reverse weathering, so Al is most likely adsorbed to particulate oxides. On shorter time scales, dust appears to increase particle flux through its role in aggregation rather than by nutrient inputs enhancing productivity. We suggest that the role of dust as a catalyst in particle formation may be a central mechanism in flux formation in this region, particularly when zooplankton fecal pellet production is low.     

厦门湾沉积物间隙水中CDOM的荧光特性及其分布研究

研究了2003年4月从厦门湾九龙江口、西海域及同安湾采集的表层沉积物及柱状样间隙水中有色溶解有机物(CDOM)的荧光特性及其水平与垂直分布特征.结果表明,间隙水CDOM中均观测到类腐殖质与类色氨酸两类荧光.它们在表层沉积物间隙水中的相对含量均以九龙江口靠近浮宫红树林区的站位最高,同安湾及西海域养殖区各站位次之,分别反映了河口区红树林生态系以及养殖活动的影响;西海域靠近东渡码头的站位两类荧光的相对含量最低,系受疏浚活动影响所致.表层沉积物间隙水中两类荧光的相对含量均远高于底层水,暗示表层沉积物可成为上覆水体CDOM的一个重要来源.大多数站位间隙水中类腐殖质荧光的相对含量随深度增加而渐增,反映了CDOM在缺氧环境下的成岩作用过程.多数站位在3～6 cm深度处出现类色氨酸荧光峰值,随后递减,反映了近表层沉积物中细菌等微生物活动对蛋白质的降解作用.     

Amino acid biogeochemistry and bacterial contribution to sediment organic matter along the western margin of the Bay of Bengal

Six sediment cores collected from various water depths and sampling locations along the western margin of the Bay of Bengal (BOB) were investigated for the total hydrolysable amino acids (THAA) and d-amino acids (d-AA) to understand their distribution, digenetic alteration and bacterial contribution to organic matter (OM). Irrespective of their location, THAA concentrations and yields generally decreased and mol% glycine increased with increasing water depth indicating that OM was degraded during its transit through the water column. Amino acid based degradation index (DI) indicated that OM of the surface sediments of shallow stations, BOB-1 to BOB-3 was relatively fresher than that of deeper stations, BOB-4, BOB-5 and BOB-6. The concentrations and mol% of the d-AA varied from 0.04 to 0.76 µmol gdw⁻¹ and 0.3 to 8.5 mol%, respectively. Contribution of bacterial peptidoglycan amino acids to THAA (% THAA_pep/THAA) ranged between 4.0% and 55.0%. Both % THAA_pep/THAA and mol% d-AAs were significantly (p<0.01) higher in the surface sediments and decreased with sediment core depth. Based on the d-AA yields, bacterial OM accounted for 1.5–15.6% of TOC, and 3.7–50.0% of TN of the sediments of BOB.