Die Miesmuschel Mytilus edulis als Indikator für die Bleikonzentration in Weserästuar und in der Deutschen Bucht

Common mussels were collected at 13 stations of the Weser Estuary and the German Bight in 3 size catagories: 14 to 16 mm, 21 to 23 mm, 35 to 40 mm shell length. Equal numbers of the 3 groups from each station were analyzed separately for lead concentration by flameless atomic-absorption spectrophotometry. The lead concentration of the soft parts decreases from 6.4 μg/g dry weight 15 km northwest of Bremerhaven to 1.9 μg/g at Helgoland. At the same station, the concentration in small musels is significantly higher than in larger mussels. The lead concentration is exceptionally high in the kidney, quite high in the intestine (with the digestive glands) and in the adductor muscle, and rather low in the foot, gills, and mantle with gonads. Unpublished results of my laboratory experiments reveal that mussels directly reflect the actual lead concentration of their environment. The observed gradient in lead contents of M. edulis in the Weser Estuary can thus be explained by the dilution of the highly lead-polluted river water by the sea water of the German Bight. With this physiological property, M. elulis is, therefore, highly suitable as an indicator organism for lead, and possibly other heavy metal pollutants.     

The prevalence of heavy metals in Cladophora glomerata L. from Farahabad Region of Caspian Sea – Iran

The presence of toxic heavy metals in the environment is considered as a risk factor for adverse human and environmental health effects. Farahabad Region is a tourist center in the southern coast of Caspian Sea in Mazandaran Province of Iran. Environmental monitoring of this site is important for public health for individuals visiting and residing in this region. Although numerous biomonitoring data are available globally, very few if any apparent investigations have been conducted in this region. In this study, concentration of three heavy metals chromium (Cr), lead (Pb), and cadmium (Cd) was determined for one year in Cladophora glomerata, the predominant macroalga species present in this region. Detection of heavy metals was performed with atomic absorption spectrophotometer using standard methods. Results showed that the range of Cr metal in various algal samples was 29–55 ppm/g dry weight. The levels of Pb in algal samples (Cladophora) ranged from 2 to 8 ppm/g dry weight. The Cd concentrations in C. glomerata biomass ranged from 1.5 to 8.2 ppm/g dry biomass. In view of potential threats of such high metal concentrations in coastal waters and in algal tissues, it is necessary to adopt conservation measures to ensure public health safety.     

Lead uptake from sea water and food,and lead loss in the common mussel Mytilus edulis

Common mussels, Mytilus edulis (shell length 19 to 21 mm, average dry weight 30 mg) were maintained for 6 weeks in sea water containing different concentrations of lead (0.005 to 5 mg · l^-1). The lead concentration in the mussels' whole soft parts was analysed at different times during the experiment. A constant rate of lead uptake, linearly dependent on the lead concentration of the medium, was observed. Thus, the temporal change of the concentration factor is also linear (regression coefficient 149.9 daily). Rate of lead loss, measured after transferring the mussels into natural sea water, is linearly dependent on the original lead concentration in the soft parts. Rates of uptake and loss in large mussels (shell length 45 to 55 mm, average dry weight 750 mg) are less than those in small mussels (shell length 19 to 21 mm, average dry weight 30 mg). During a much more extended experimental period, adjustment to a steady state is expected to occur; rates of lead uptake and loss are then non-linear. Lead uptake by individual organs (kidney, gills, adductor muscle, digestive gland, foot, mantle with gonads) of large M. edulis (shell length 45 to 55 mm, average dry weight 750 mg) was analysed in 2 test series. In the test series medium, the mussels were kept in a seawater medium containing 0.01 mg. Pb.l^-1. In the test series food, the mussels were kept in natural sea water but fed with the green algae Dunaliella marina containing lead (approximately 600 g.g^-1 dry weight). The lead quantity given per mussel per day was about 2 g in both test series. Within 35 days, the mussels of test series medium took up 29% of the total amount of lead given, those of test series food took up 23.5%. In all organs, lead concentration increased, but rates of uptake differed; the kidney displayed by far the highest rate of uptake. With these physiological properties M. edulis is an ideal indicator organism for lead pollution in the marine environment. A biologic calibration curve, the relationship between lead concentration in the mussels' whole soft parts at equilibrium and lead concentration in sea water, is presented.This paper forms part of a doctoral thesis in biology at Hamburg University     

Biosorption of lead and cadmium using marine algae

The use of algae (Ulva fasciata, green and Sargassum sp., brown) to reduce lead and cadmium levels from mono-metal solutions was investigated. The brown algae showed higher efficiency for the accumulation of lead (～1.5 times) and cadmium (～2 times) than green algae. The optimum pH value is found to be between 4 and 5.5. Regarding biomass concentration, an increase in metals percentage removal and a decrease in metal uptake capacity coincided with the increase in biomass concentration. All light metals (Ca, Mg and Na) showed a suppressive effect on biosorption capacity. The enhancement of biosorption in the case of NaOH was obvious. The biosorption process (65–90%) occurred within 3?min. Experimental data were in high agreement with the pseudo-second-order kinetic model and Freundlich model for lead and cadmium biosorption using different biosorbents. In the desorption study, 0.2?mol?L^?1 HCl recorded the best concentration for the elution of metals from the biomass. The biosorption capacity decreased over the four operational cycles for both lead and cadmium. Infrared analysis showed that amino, hydroxyl and carboxyl functional groups provide the major biosorption sites for metal binding. Use of the above-mentioned algae for cheap metal absorbance is considered as one water treatment criterion.     

Freshwater Mussel,Lamellidens Marginalis (Lamarck) (Mollusca: Bivalvia: Unionidae) As an Indicator of River Pollution

Abstract

Analyses were made of heavy metals, manganese, nickel, copper, zinc and lead in water samples and soft body, shell and different tissues (gills, digestive glands, mantle and viscera) of the Unionid mussel, Lamellidens marginalis collected from two tributaries of the Cauvery river. Water samples from Station I contained higher concentrations of the metals than those from Station II. the concentration of metals in water at both stations were in the descending order: Mn > Zn > Pb > Ni > Cu. However, the concentrations of metals in the soft body were in the descending order: Zn > Mn > Pb > Ni > Cu at both stations in all size groups of mussels tested. the concentration of zinc maintained a linear relationship with the size of the mussels, but manganese showed a reverse trend. Small size (4-5 cm) mussels accumulated more manganese (105.5 μg.g^?1 dry wt.) than larger ones (7-8 cm; 6.5 μg.g^?1 dry wt.). Both young and old is accumulate the same level of lead, copper and nickel in the soft body. the order of concentrations of metals (Mn, Pb, Zn, Ni and Cu) in the shell of mussels from both stations coincided with the order of concentrations of background water except for lead. the accumulation of lead was higher in shell (30.4-36.2 μg.g^?1 dry wt.) than in soft body (6.4-12.0 μg.g^?1 dry wt.). the pattern of concentration of metals in the various tissues reveal that the digestive glands have greater ability than other tissues to concentrate most metals under study. the concentration factors for soft body, shell and different tissues are presented. the advantages in using the common mussel for biomonitoring of contaminants in water is also discussed.     

Ultrastructural analysis of dissolution of shell of the bivalve Mytilus edulis by the accessory boring organ of the gastropod Urosalpinx cinerea

The shell penetrating mechanism of the muricid gastropod Urosalpinx cinerea follyensis Baker was examined with reference to solubilizing effects of the secretion of the accessory boring organ (ABO) on the ultrastructural organic and mineral components of the shell of the bivalve Mytilus edulis Linné. The fine structure of shell etched by the secretion was contrasted with normal shell and shell solubilized artificially by acids, a chelating agent, and enzymes as an aid in interpreting the pattern etched by the secretion. A synoptic series of scanning electron micrographs of representative regions of the normal shell of M. edulis was prepared to serve as a standard for ultrastructural interpretation of the patterns of dissolution. Intercrystalline conchiolin of the mosaicostracal, prismatic, myostracal, and nacreous strata was dissolved as readily as the periostracum by the ABO secretion. In the prismatic region, maximum depth of dissolution of intercrystalline organic matrix occurred when long axes of prisms were approximately perpendicular to the surface being dissolved. Microscopic solubilization of organic matrix noticeably preceded dissolution of mineral crystals, revealing subsurface prisms and lamellae similar in size and form to the distinctively shaped normal shell units. After solubilization of intercrystalline conchiolin, further dissolution by the ABO secretion revealed a variety of what appeared like internal structures in prisms and lamellae. The form of these subunits varied from that of platelets to nodules in prisms and from laths to nodules in lamellae. These intracrystalline patterns of dissolution probably resulted from preferential etching of (a) soluble intracrystalline conchiolin membranes or other internal aggregates of nacrin, (b) heterogeneously distributed trace and minor elements, or (c) from both. Carriker and Williams (1978) hypothesized that a combination of HCl, chelating agents, and enzymes in a hypertonic mucoid secretion released by the ABO dissolve shell during hole boring. The similarity of patterns of dissolution etched by the ABO secretion and those produced artificially by HCl and EDTA in the present study support the hypothesis that these chemicals, or chemicals similar to them, are constituents of the ABO secretion. Lactic and succinic acids and a chitinase-like enzyme were also suggested by Carriker and Williams as possible agents in shell dissolution. Alteration of the shell surface by experimental application of these, and other, chemical agents was not sufficiently comparable to that etched by the ABO secretion to support the suggestion. Preferential dissolution of shell matrix by the ABO secretion is functionally advantageous to boring gastropods because it increases the surface area of mineral crystals exposed to solubilization and facilitates removal of shell units from the surface of the borehole by the radula.     

Total body zinc concentration and allometric growth ratios in Mytilus edulis collected from different shore levels

Body zinc concentrations (on a soft parts dry weight basis) in 18 composite collections of mussels (Mytilus edulis) taken from different shore levels within a single mussel bed on the north shore of the Tyne estuary at Tynemouth, on 25 October, 1980, showed highly significant correlations with 4 allometric, size-related factors. A negative correlation was found between body zinc concentration and a flesh condition (FC) index defined as mg dry flesh wt per g dry shell wt. Positive correlations were found between body zinc concentration and width: height ratio, width: length ratio and shell valve inequality index (SVI) defined as the weight of heavier shell valve/weight of lighter shell valve. Unlike earlier observations on a single population taken from a single habitat, this heterogeneous collection showed no significant relationship between body zinc concentration and body size as determined by soft-parts dry weight. Body zinc concentration and allometric ratios were, however, related to position on the shoreline. It is suggested that, where mussels are collected from different habitats, environmental factors probably have a greater influence on body size than age. Therefore, normalization of trace metal concentrations to a standard body weight may not be appropriate where specimens are collected from a variety of habitats. Allometric ratios are related to age, but are independent of absolute size, and may therefore provide a more suitable basis for normalization of trace metal concentration within a monitoring programme.Contribution No. 1222 of the Center for Estuarine and Environmental Studies of the University of Maryland     

Growth and content of energy reserves in juvenile sea scallops,Placopecten magellanicus,as a function of swimming frequency and water temperature in the laboratory

The effects of swimming frequency and water temperature on shell growth, tissue mass, and stored energy reserves of juvenile sea scallops, Placopecten magellanicus Gmelin, were examined in a factorial laboratory experiment spanning six weeks in July and August 1992. Individually tagged scallops of similar initial size (22.5±0.1 mm shell height, n=240) were induced to swim to exhaustion at three different swimming frequencies (every day, twice a week, or not at all) in two different water temperature regimes (4 to 7 or 7 to 13°C). The scallops were fed an ad libitum mixture of cultured microalgae. At the end of the experiment, cumulative increase in shell height, dry weight of soft tissues, condition index of dry adductor muscle (adductor muscle dry weight/soft tissue dry weight x 100) and total carbohydrate content of dry adductor muscle were measured for each scallop. Scallops at the higher temperature had significantly greater shell heights, and were in better metabolic condition as evidenced by significantly higher condition indices and muscle carbohydrate contents. The dry soft tissue weights did not differ significantly from their low temperature counterparts. Swimming frequency had no significant effect on shell height, dry tissue weight, or carbohydrate content, but condition index of the adductor muscle increased significantly with swimming frequency. These results show that not only was there no cumulative cost of swimming in terms of shell growth, total soft tissue weight, or carbohydrate content in young scallops, but that condition of adductor muscle tissue was higher in scallops that swam.     

Determination of average individual dry weights and ash-free dry weights in different sieve fractions of marine meiofauna

Individual dry weights and ash-free dry weights for different meiofauna taxa from two soft bottom localities (31 and 117 m depth) in Gullmar Fjord on the Swedish west coast were determined. Samples from August 1980 and February 1981 of about 100 to 600 formalin-preserved specimens of each of the different taxa from each of four sieve fractions were weighed on a microbalance. Individual dry weights ranging from 0.12 g (nematodes in the 0.040-mm fraction) to 172 g (polythalamous, arenaceous Foraminifera in the 0.500-mm fraction) and ash-free dry weights ranging from 0.10 g (nematodes in the 0.040-mm fraction) to 37 g (polychaetes in the 0.500-mm fraction) were obtained. Great similarities were noted between corresponding values from the two stations as well as between summer and winter values. The percentage of organic matter, determined by ashing, in the body weight differed greatly among taxa. Some standard individual dry weight and ash-free dry weight values, to be used for re-calculation of abundance values into biomass, are presented.     

Encapsulated development of the marine prosobranch gastropod Nucella lapillus

Nucella (=Thais) lapillus (L.) develops to the juvenile stage within an egg capsule. This study was undertaken to investigate nutritive and bacteriostatic properties of the intracapsular fluid for this species. Capsules were collected intertidally at Nahant, Massachusetts, USA, in the summers of 1982 and 1983. The average capsule contained only 1.1 l of intracapsular fluid per embryo. A statistically significant correlation was observed between capsule height and number of developing embryos contained therein, although the number of embryos per capsule was more closely related to capsule volume. Total dry weight of encapsulated, shelled embryos increased exponentially as a function of shell length. However, weight increases may be entirely due to shell calcification; the average dry tissue weight of shelled embryos was significantly below that for pre-shelled individuals, suggesting a net loss of biomass during development. Aliquots of intracapsular fluid failed to inhibit the growth of the 13 bacterial strains tested. Despite the above results, pre-shelled embryos generally survived only several days following their premature removal from egg capsules at 12°C. Shelled veligers were reared outside of the capsules with no apparent ill effects. An explanation for these survivorship results is elusive.     

Examples of post-mortality alteration in Recent brachiopod shells and (paleo)ecological consequences

Post-mortality alteration of brachiopod shells under normal environmental conditions leads to high taphonomic loss, and to a poor contribution to the biodetrital soft sediment. The successive stages of alteration which shells undergo are: (bio)degradation of the organic matrix shell softening structural disaggregation or/and mechanical fragmentation; these processes depend on the shell structure (number of layers) and composition (organic and inorganic components), but very little on environmental conditions, except for the dissolution of inorganic shell constituents. Among the Brachiopoda, three types of alteration occur to different types of shells — Type I: two-layered chitino-phosphatic shell (species ofLingula andGlottidia) displays a rapid degradation of the organic matrix and mechanical abrasion, leading to total disappearance of the shell in 2 to 3 wk; Type II: two-layered carbonate shell, e.g.Terebratulina spp. [but notNotosaria nigricans (Sowerby) which may constitute a fourth shell type], exhibits degradation of the organic matrix of the secondary layer, shell softening, and structural disaggregation leading to shell disintegration in 6 to 7 mo with a concomitant contribution of calcitic microfibres to the sediment; Type III: three-layered carbonate shell, e.g.Gryphus vitreus (Born), undergoes organic degradation of the secondary layer, fragmentation of the anterior two-thirds of the shell, and slow degradation (because of the thick tertiary layer) of the posterior portion of the shell, with dissolution of the inorganic components (mainly in the tertiary layer) which make a relatively minor contribution to the sediment.     

Effect of diet on growth rate and reproductive fitness of Turbo sarmaticus (Mollusca: Vetigastropoda: Turbinidae)

Experiments were conducted to determine the effect of four algal diets (Corallina spp., Gelidium pristoides, Ulva rigida and an equal volume mixture of these seaweeds) on growth and reproduction of the South African gastropod Turbo sarmaticus Linnaeus, 1758. The best growth rate of juveniles (up to 13.8 mm shell length and 34.26 g wet body weight increase in 12 months), reproductive fitness of mature specimens (gonad index up to 33%) and energy reserves (up to 4.76 mg glycogen/100 mg foot tissue) were achieved when T. sarmaticus was fed U. rigida or a mixed diet. In addition, the gonad index of individuals fed these diets was almost twice that of similar-sized field specimens. Juveniles fed Corallina spp. only, grew very little (only 2.4 mm shell length and 4.23 g wet body weight increase in 12 months). The reproductive fitness of adults fed on such a diet was also poor (gonad index <4.5%) and energy reserves were low (<3.5 mg glycogen/100 mg foot tissue). Along the southeastern coast of South Africa, T. sarmaticus has a distinct reproductive cycle with gametogenesis occurring from March/April until August/September, whilst maturity (gonad index = 15%) was maintained until December, after which spawning occurred until March. Received: 6 July 1998 / Accepted: 8 March 1999     

Macrozoobenthic assemblages in relation to environments of the Yangtze-isolated lakes

Eutrophication can shift lakes from a clear, macrophyte-dominated state to a turbid, algae-dominated state, and different habitat condition supports different fauna. Macrozoobenthos are good indicators of water environment, and studies on macrozoobenthic assemblage characteristics can help us to know which state a lake is in, thus provide the basis for its eutrophication control. In this study, a systematic investigation on macrozoobenthos was conducted in 17 Yangtze-isolated lakes to explore the macroecological laws of macrozoobenthic assemblages. Detrended correspondence analysis (DCA) revealed that variance of benthic assemblage structure occurred in two types of lakes. In macrophytic lakes, altogether 51 taxa of macrozoobenthos were identified. The average density and biomass of total macrozoobenthos were 2231 individuals·m^?2 and 1.69 g dry weight·m^?2, respectively. Macrozoobenthic assemblage was characterized by dominance of scrapers (i.e. gastropods). In algal lakes, altogether 20 taxa of macrozoobenthos were identified. The average density and biomass of total macrozoobenthos were 2814 individuals·m^?2 and 1.38 g dry weight·m^?2, respectively. Macrozoobenthic assemblage was characterized by dominance of collector-gatherers (i.e. oligochaetes). Wet biomass of submersed macrophytes (B _Mac) and phytoplankton chlorophyll a concentration (Chl a) were demonstrated as the key factor structuring macrozoobenthic assemblages in macrophytic and algal lakes, respectively.     

Direct production of hydroxymethylfurfural from raw grape berry biomass using ionic liquids and metal chlorides

We report for the first time the direct conversion of raw grape berry biomass to hydroxymethylfurfural (HMF) using ionic liquid solvents with metal chloride catalysts. Exploiting raw plant biomass as a biorefinery feedstock is innovative for sustainable chemical industry. The use of the raw biomass to synthesize compounds can indeed lead to less energy consumption and less CO₂ emissions. Using raw plant biomass skips pretreatment steps that are required to produce biomaterials such as carbohydrates or cellulosic biomass. Here, grape berry biomass was used as a raw chemical feedstock for the production of hydroxymethylfurfural, a key platform intermediate for syntheses of future renewable biofuels. We examined 3 ionic liquid solvents, 3 reaction temperatures, 5 chloride catalysts, and 5 concentrations of HCl. We found an increasing HMF yields depending on reaction conditions. 1-octyl-3-methylimidazolium chloride was most effective for HMF synthesis. Addition of HCl or metal chlorides alone showed little improvement. The highest HMF yield of about 100 mg HMF per mL of grape biomass extract was obtained using 0.3 M HCl, [OMIM]Cl, and CrCl₂ at 100°C for 3 h. Our study provides a model system of sustainable production of valuable compounds from raw plant biomass.     

Biomass and trophic structure of the macrobenthos in the south-west lagoon of New Caledonia

The biomass of the macrobenthic communities of the southwest lagoon of New Caledonia is analysed with special reference to tropical soft-bottom assemblages. The samples were obtained in 1986 from 350 Smith-McIntyre grabs as well as by diving over an area of 3 500 m², and covered a wide size-range of benthic organisms. The classification of the biomass data into taxonomic groups revealed the following: (1) a zoobenthic biomass (mean=13 g ash-free dry wt m^-2) that is high compared to values previously published for tropical systems, but fairly low compared to those recorded for medium and high latitudes; (2) a large macrophytic biomass (45% of ash-free dry wt); (3) dominance by weight of sponges, molluscs and cnidarians over the other faunal groups. The distribution of the biomass among the trophic groups revealed the following: (1) the dominance by weight of suspension-feeders, which account for 67% of the total zoobenthic ash-free dry wt; (2) the absence of trophic group amensalism between filter-feeders and deposit-feeders whatever the degree of bottom muddiness; (3) the existence of a relationship between the biomass of surface deposit-feeders and ATP at the surface layer of the sediment, suggesting that this group feeds preferentially on living particles. Differences in trophic structure between the muddy-bottom, greysand and white-sand communities of the lagoon reflect the functional characteristics of each bottom type.     

Response of winter wheat yield and soil microbial biomass to fertilization with ridge mulching-furrow planting in the dry highlands of the Loess Plateau北大核心CSCD

As the typical planting pattern of winter wheat in the dry highlands of the Loess Plateau, ridge mulching-furrow planting (RMFP) has played an important role in fertilizer efficiency of different fertilizers, and the differences in fertilizer efficiency further influence the diversity of the structure of soil microbial communities. The effects of different fertilization practices on winter wheat yield formation, soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), and soil microbial biomass phosphorus (SMBP) were investigated by field experiments during 2014-2016 in the winter wheat growing region of the dry highlands in southern Shanxi. The treatments included four groups, farmer fertilization (FF), monitoring fertilization (MF), monitoring fertilization combined application of manure (MFM), and monitoring fertilization combined application of bio-organic fertilizer (MFB). Results showed a significant increase in winter wheat yield by optimized and balanced fertilization, and the grain yield of MFB was highest among all treatments, with a value of 4 107-5 400 kg/hm2, which was 14.5%-23.2% (P < 0.05) higher than that of FF. The effects of different fertilization treatments on the winter wheat yield formulation mainly depended on spike number; however, no effect was found on kernel number per spike and 1 000-grain weight. Soil microbial biomass was affected by both growth period and fertilization patterns, i.e., the content of SMBC from jointing to flowering stage was highest during the winter wheat growth period, whereas the maximum values of SMBN and SMCP were found during the jointing stage. Changes in the rates of SMBC, SMBN, and SMBP during the entire growth period were less than 50%; however, the average contribution rate of optimized fertilization on SMBC, SMBN, and SMBP reached 90%. Compared to single chemical fertilizer applications, the combined application chemical fertilizer and manure or bio-organic fertilizer significantly improved the contents of SMBC, SMBN, and SMBP; however, the contents of SMBC and SMBN between MFM and MFB had no significant difference, whereas the SMBP of MFB was 19.8%-47.1% (P < 0.05) higher than that of MFM owing to the effect of mixed phosphorus bacteria. The soil microbial biomass C/N and C/P of the different treatments were 6.9-9.8 and 14.4-41.0, respectively, and maximum values occurred during the flowering stage. Given the above, the combined application of reasonable chemical fertilizer and bio-organic fertilizer can effectively improve the winter wheat yield and soil microbial biomass under RMFP cultivation in the dry highlands of the Loess Plateau. © 2018 Science Press. All rights reserved.     

Lead and cadmium bioaccumulation in fowl eggs depending on different food concentrations

Cadmium and lead bioaccumulation in eggs from four groups of laying hens was studied. The birds were fed on foods containing different quantities of cadmium and lead, exceeding the official technological standards for three of the groups. Bioaccumulation was studied using two criteria: coefficient of biological intake (CBI), which is the ratio between the concentration of the chemical element in a unit of dry biomass and its fodder concentration, and Klarck of concentration /Kc/ ‐ a dynamic value which includes both the fodder and water concentrations of the elements needed for acquiring a unit of biomass. For the high cadmium and lead concentrations, dissipation of the studied elements in the egg mass was established with lower values of both CBI and Kc.     

全氟辛烷磺酸短期暴露对不同作物苗期生长的影响

全氟辛烷磺酸(PFOS)作为一种新型持久性有机污染物,目前国内外对其生态毒性研究主要集中在水环境领域,而高等植物的生态毒性数据尚不完善。因此,本研究采用内培养方式,选取小麦、大麦、小白菜、三叶草、绿豆作为供试植物,利用根伸长、芽伸长、地上部分生物量等评价指标,研究了PFOS短期暴露对不同供试作物苗期生长的影响,建立了PFOS和作物苗期生长的剂量-效应关系,并对不同的评价指标进行相关性分析,筛选出表征PFOS生态毒性的敏感植物。结果表明,不同供试作物培育3 d后,PFOS对其于不同毒性终点的最小EC₅₀值为：小麦352 mg·kg^-1(根伸长)、大麦434 mg·kg^-1(根伸长)、三叶草794 mg·kg^-1(地上部分生物量鲜重)、小白菜829 mg·kg^-1(地上部分生物量鲜重)、绿豆>1 000 mg·kg^-1,因此敏感程度依次为：小麦>大麦>三叶草>小白菜>绿豆。须根系作物小麦、大麦较直根系作物三叶草、小白菜和绿豆敏感,而须根系作物各评价指标的敏感程度依次为：根伸长>地上部分生物量鲜重>芽伸长>地上部分生物量干重,可见小麦的根伸长对PFOS污染最为敏感。各评价指标间均呈正相关关系,表明PFOS对同种植物的不同评价指标影响趋势一致。     

Primary-Production measurements for the green seaweed Codium fragile in long island sound

Rates of primary production and compensation depths were determined for Codium fragile by 3 different measurements: (1) growth rate; (2) rate of ¹⁴C-fixation; (3) rate of O₂ evolution. The radiocarbon assay employed liquid scintillation counting of homogeneous suspensions of seaweed tissue in gelled fluor. Maximum rates of primary production ranged between 2.6 and 3.9 mg C-fixed/g dry weight/h. The compensation depth is regulated by local turbidity, as is vertical distribution. All 3 methods for the determination of compensation depth, when used simultaneously, gave the same value. Chlorophyll levels were found to vary inversely with available light, hence depth, whereas starch levels were found to vary directly with available light.     

Physical and biological gradients in a submarine cave on the Western Mediterranean coast (north-east Spain)

Submarine caves are semi-closed subsystems within the marine littoral ecosystem. One of the most striking features is the progressive reduction of the number of phyla, species, and biomass towards the interior of such a cave. The decrease in biomass has been explained as the result of low exchange rates of the water inside the caves which limit the supply of oxygen and food particles from the exterior. Many authors have proposed that this reduced exchange rate is associated with the occurrence of marked gradients in temperature, salinity, oxygen and light. Measurement of faunal abundance of a cave in the littoral zone of the Medes Islands (Catalonia, north-east Spain) made between June 1983 and July 1984, revealed a zonation similar to that in other Mediterranean caves. Animal biomass decreased from 260 g ash-free dry weight m^-2 at the entrance to 80 g ash-free dry weight m^-2 at the end of the cave (50 m from the mouth). A special technique for remote water-sampling was developed to avoid problems due to turbulence caused by divers in this semi-closed system. This involved the installation of a series of plastic tubes at different points along the axis of the cave. The water was brought to the surface using a battery-powered electric pump. The reliability of this method was verified by comparing the results with samples collected directly by divers. Sampling both in winter and summer showed no longitudinal gradients for temperature, salinity, oxygen, chlorophylla and the number and volume of suspended particles. These results suggest that there is a constant circulation within the cave which guarantees water-exchange. The decrease in biomass cannot be explained by physico-chemical gradients due to insufficient exchange with the external system. On a finer scale, however, along the walls of the cave there may exist boundary layers that are not affected by the general circulation. This could account for the observed decrease in the biomass of benthic organisms.