The effect of deposition of organic matter on phosphorus dynamics in experimental marine sediment systems

The effect of deposition of organic matter on phosphorus dynamics in sandy marine sediments was evaluated using an experimental system (boxcosms) and three different strategies: (1) no supply (2) one single addition (3) weekly additions of a suspension of algal cells (Phaeocystis spec.). Macrofauna (3 species, 6 individuals of each) were added to half of the boxes. Both in the case of the single and weekly additions a clear effect of increased organic matter loading on phosphorus dynamics was found. Following the organic matter addition, porewater phosphate concentrations in the upper sediment layer increased, phosphate release rates from the sediment increased by a factor 3–5 and in the boxes to which a single addition was applied NaOH-extractable phosphorus increased substantially. The increase in phosphate release rates from the sediment was attributed to mineralization of the added material and to direct release from the algal cells. No clear effect of the presence of macrofauna on sediment-water exchange of phosphate could be discovered. The macrofauna were very effective at reworking the sediment, however, as illustrated by the organic carbon profiles. It is hypothesized that the sediment-water exchange rates of phosphate were regulated by the layer of algal material which was present on the sediment surface in the fed boxes. In the boxes to which the single addition was applied porewater phosphate concentrations were lower and NaOH-extractable phosphorus was higher in the presence of macrofauna, suggesting that macrofauna can stimulate phosphate binding in the sediment.Publication no. 40 of the project Applied Scientific Research Netherlands Institute for Sea Research (BEWON)     

A comparison of genetic diversity levels in marine, freshwater, and anadromous fishes

Electrophoretic data were analysed from 49 species of freshwater fish, 57 species of marine fish, and seven anadromous species. For each species, at least 15 individuals had been assayed for at least 15 loci in two or more subpopulations. The results showed that while average total heterozygosity ( _T ) was approximately equal in freshwater and marine species (0·062 and 0·064 respectively), subpopulation heterozygosity ( _s ) was significantly less in the former group (0·046 and 0·059 respectively). Consequently the average degree of genetic subpopulation differentiation ( _ST ) was significantly greater for freshwater species (0·222 v. 0·062). On average, it is likely that marine subpopulations exchange between 10 and 100 times more migrants per generation than freshwater subpopulations, presumably because of the relative absence of barriers to dispersal in the marine environment. The reduced values of H_s in freshwater species are likely to reflect reduced effective subpopulation sizes relative to marine species. The few andromous species that have been analysed show intermediate levels of G_ST .     

Arsenic speciation in marine sediments: A comparison between two sequential extraction procedures

ABSTRACT

Arsenic distribution and mobility in marine sediments was investigated by means of total extraction and two sequential extraction procedures i.e. a modified sequential extraction procedure proposed by the European Standard, Measurementand Testing (SM&T) program, formerly the Community Bureau of Reference (BCR) procedure and a five steps sequential extraction based on the Wenzel extraction procedure, called modified Wenzel extraction. Sediments were collected from Cagliari’s harbour and Cagliari’s gulf, in Western Mediterranean Sea, Italy. The modified Wenzel extraction provided a more detailed As binding pattern and turned out to be much more appropriate than the modified SM&T procedure for gaining information regarding the mobilization of As within marine sediments. In the harbour, the largest part of As is contained in the residual fraction. At the contrary, As concentration, which is higher in the Cagliari’s gulf, is primarily associated with amorphous and crystalline hydrous Fe(Mn, Al) oxide. Moreover, this study suggests the possibility to segregate different types of marine sediments depending of human or industrial activities and to trace As contaminated marine sediments to determine the origin of contamination following the percentile of As contained in each extraction steps.     

Mass balance models of phosphorus in sediments and water

Models are presented in order of progressively more complex spatial resolution in which the effects on the sediment-water interactions are emphasized. For simple models, the diagnostic approach of calculating the net settling and return of total phosphorus is demonstrated with data from Lake Erie. For more complex models, the effects of interbasin transport and vertical mixing are shown to be important in determining the pathways of the sediment-released or sediment-bound phosphorus in the water column.     

A modified method for studies of electron transport system activity in freshwater sediments

A method for measuring respiratory electron transport system activity (ETSA) in freshwater sediments is presented. It is a modification of the methods used for marine sediments by Christensen & Packard (1977) and Olànczuk-Neyman & Vosjan (1977). The assay is based on the reduction of the electron acceptor 2-(p iodophenyl) 3 (p nitrophenyl) 5 phenyl tetrazolium chloride (INT) by cell-free homogenates of sediment samples. This study shows that the method is sensitive, has good accuracy and can be used for freshwater sediments. The accuracy decreases at high turbidity and as yet has only been tested for sediments of the gyttja type. Untreated samples can be stored at low temperature for several weeks without any loss of activity. ETSA decreases with the depth of sediment and with increased amount of allochthonous material in the sediment.     

Nutrient (N,P, Si) fluxes between marine sediments and water column in coastal and open Adriatic

Nutrient benthic fluxes, as well as sediment phosphorus concentration at the open sea and coastal water stations of the Central and South Adriatic were studied during 1997–98. The fluxes were in the ranges: 0.16–2.67 mmol m^–2 d^–1 (silicate); –0.031–0.164 mmol m^–2 d^–1 (phosphate); –0.51–2.03 mmol m^–2 d^–1 (ammonia); and –1.32–1.62 mmol m^–2 d^–1 (nitrate + nitrite). Silicate flux showed a gradient from the coastal area to the open sea. Ammonia was the main nitrogen species in the flux at the estuary and bay stations, while the sum of nitrate and nitrite was predominant at the open sea stations. Relationships between phosphate and ammonia fluxes (r = 0.699, p<0.01) as well as phosphate and silicate (r = 0.529, p<0.01) were established.     

Effects of benthic macroinvertebrates on the exchange of solutes between sediments and freshwater

Infaunal macrobenthos (tubificid oligochaetes, chironomid larvae, and unionid bivalves) were studied in laboratory microcosms to determine their effects on freshwater sediment diagnesis and the exchange of solutes between sediments and water. Tubificids enhanced the flux of ammonium, bicarbonate, and silica from sediments. After the onset of anoxia, they decreased the flux of iron and phosphate. Chironomids increased the flux of nitrate, bicarbonate, and silica, but did not affect the flux of phosphate. Pore water concentrations were low within the irrigated burrowed zone for chemical species normally high in reduced sediments. Concentration gradients were less steep in the actively irrigated burrow zone, but radial diffusion to and from burrows, increased rates of organic decomposition, and enhanced diatom frustule dissolution rates result in enhanced mass transport from sediments. Data from an experiment with unionid clams demonstrated the presence of radial diffusion gradients. These clams enhanced the chloride and nitrate flux from sediments, decreased the bicarbonate flux, but did not affect the flux of either phosphate or silicate. Although the clams did not actively irrigate their burrows, their effect on sediments was similar to that of chironomids. Comparison of direct and indirect flux estimates showed that both types of estimates could be highly variable. In general, indirect flux estimates were higher than direct flux estimates.     

湿地沉积物对磷的吸附-解吸动力学模型概述

介绍了常用的吸附-解吸动力学模型(Freundlich方程、Langmuir方程及Temkin模型),分析比较了不同模型之间的相互关系,对目前国内外关于磷吸附-解吸动力学模型研究进行了简要概述,介绍了不同模型的统一表达形式,并提出应加强对不同类型湿地中沉积物对磷的吸附-解吸过程及其动力学模型、对吸附-解吸过程的长期监测和不同环境因子间的交叉效应研究等建议,以深化对动力学模型的认识,从净化机理层面充分理解湿地生态系统的运行机制.     

Viral abundance and genome size distribution in the sediment and water column of marine and freshwater ecosystems

The size distribution of viral DNA in natural samples was investigated in a number of marine, brackish and freshwater environments by means of pulsed field gel electrophoresis (PFGE). The method was modified to work with both water and sediment samples, with an estimated detection limit for individual virus genome size groups of 1-2 x 10(4) virus-like particles (VLP) mL(-1) water and 2-4 x 10(5) VLP cm(-3) sediment in the original samples. Variations in the composition and distribution of dominant virus genome sizes were analyzed within and between different habitats that covered a range in viral density from 0.4 x 10(7) VLP mL(-1) (sea water) to 300 x 10(7) VLP cm(-3) (lake sediment). The PFGE community fingerprints showed a number of cross-system similarities in the genome size distribution with a general dominance of genomes in the 30-48, 50-70 and 145-200 kb size fractions, and with many of the specific genome sizes detected in all the investigated habitats. However, large differences in community fingerprints were also observed between the investigated sites, and some virus genome sizes were found only in specific biotopes (e.g. lake water), in specific ecosystems (e.g. a particular lake) or even in specific microhabitats (e.g. a particular sediment stratum).     

Microbial metabolism in surface sediments and its role in the immobilization of phosphorus in oligotrophic lake sediments

Rapid microbial metabolism and a large phosphorus uptake potential were observed in surface sediments of Lake George, New York. This sediment (termed the flocculent layer) also exhibited a phosphorus limited condition and a large reservoir of inorganic phosphorus associated with humic substances. These observations suggest that the empirically observed phosphorus retention in oligotrophic lake sediments may be promoted by a rapid cycling of phosphorus between microflora and its associated organic matter.     

乳山湾东流区沉积物中不同形态磷的分布特征

对2003年8月在乳山湾东流区采集的沉积物样品中的不同形态磷的平面和垂直分布特征进行了分析,并探讨了这些磷的形态分布与贝类养殖的关系,结果表明,不同形态磷在贝类高密度养殖区含量大于低密度养殖区.养殖区的垂直分布比较复杂,在1～20cm范围含量均出现较大波动,这与贝类养殖活动有关.Fe-P、Al-P含量出现较大波动还与污染程度有关,Or-P还与浮游植物活动有关.养殖区Ex-P、Fe-P、NAIP占TP的平均百分含量大于非养殖区,De-P、Oc-P恰好相反.Ca-P是乳山湾沉积物中含量最高的磷形态,Fe-P 和Or-P是最主要的两种生物可获得磷.TP、Or-P含量在养殖区与非养殖区之间没有显著差异,养殖区Fe-P含量高于非养殖区,3种磷的平均含量一般大于其它海区.非生物可获得磷约占TP的60%左右.     

Factors influencing fractional phosphorus composition in sediments of Spanish reservoirs

Total phosphorus in sediment (P_sed) and its fractional composition (reactive phosphate extracted with NaOH, NaOH-RP, reactive phosphate extracted with HCl, HCl-RP, and residual phosphate, residual-P) have been determined in superficial sediments of 43 Spanish reservoirs located in different limnological regions and with different trophic states. Data were evaluated by statistical analysis to examine the influence of regional distribution and trophic status. Relations with calcium, manganese, iron and aluminium contents have also been studied.In the western part of Spain, reservoirs presented the highest values on average of P_sed, NaOH-RP and residual-P (1296, 328 and 877 µg g^–1 dw., respectively) and the lowest values of HCl-RP (91.0 µg g^–1 dw.). The main phosphorus fractions were residual-P (> 50%) and NaOH-RP (>10%). In the eastern area, P_sed NaOH-RP and residual-P attained the lowest values on average (502, 4 and 330 µg g^–1 dw., respectively), whereas HCl-RP presented the highest values (167 µg g^–1 dw.). The main fractions were residual-P (> 50%) and HCl-RP (> 25%).Trophic status seemed to be a secondary factor controlling P_sed. The highest contents of P_sed were found in eutroohic reservoirs, but only when those of the same region were compared, and the statistical significance (ANOVA F test) of the observed differences was very small (p < 0.057).     

Distribution and release of sedimentary phosphorus in Lake Ladoga

Sedimentary phosphorus fractions and phosphorus release from the sediments were studied in Lake Ladoga at altogether 46 sampling sites, representing the full range of sediment types encountered in the lake. Determination of P fractions and physico-chemical analyses were made of surface sediment cores (10–20 cm long, each sampled at 3–4 levels) and in the overlying water. The range of total phosphorus per dry weight of sediment was 0.2–3.3 mg g^–1, and that of inorganic P 0.1–2.5 mg g^–1. The levels of interstitial soluble phosphorus, range 2–613 µg 1^–1 for total P and 1–315 µg 1^–1 for inorganic P, were higher than those of dissolved P concentrations in the overlying water. Diffusive fluxes of phosphate from sediment to the overlying water were estimated using three independent methods. The estimated range was 4–914 µg P m^–2 d^–1; the mean value for the whole bottom area, 0.1 mg P m^–2 d^–1, is lower than previously published estimates. The estimated annual contribution of sedimentary inorganic P flux to Lake Ladoga water is equal to 620 tons of P per year, which amounts to more than 10% of the estimated external P load into the lake. 68% of the total diffusive flux emanates from deep water sediments, which are not exposed to seasonal variation of conditions. In deep lakes, such as Lake Ladoga, phosphorus release from the sediments is controlled primarily by diffusive mechanisms. Wave action and currents as well as bioturbation are probably of importance mainly in shallow near-shore areas. Phosphorus release by gas ebullition and macrophytes is considered negligible.     

Nutrient and hydrologic budgets of a great lakes coastal freshwater wetland during a drought year

A coastal wetland along Lake Erie (Ohio, U.S.A.) was studied to determine hydrologic and phosphorus budgets and spatial and temporal variation of phosphorus and related chemical parameters. The wetland was influenced by changing Lake Erie water levels, seiches, shifting shoreline sediments, and watershed inflow during a year of severe drought. The water budget for a 7-month period (March – September, 1988) had average inflow of 15 200 m³ day^–1 from the watershed and 3.5 m³ day^–1 from Lake Erie. The wetland increased in volume by 700 m³ day^–1 despite a drought that resulted in 80% more evapotranspiration than rainfall as a barrier beach isolated the wetland from Lake Erie for 77% of the study period. Conductivity decreased by 34% as water flowed through the wetland and turbidity and total suspended solids were variable and statistically similar at inflow and outflow. Average total phosphorus concentrations in the inflow and outflow were also similar (247 and 248 µg P l^–1 respectively) although total soluble phosphorus and soluble reactive phosphorus decreased significantly (=0.05) from inflow to outflow (averages 94 to 45 µg P l^–1 and 7.5 to 4.0 µg P l^–1 respectively). Nutrient budgets from field data estimate a retention of 36% of the phosphorus, presumably in the sediments (0.8 mg P m^–2 day^–1). A general nutrient retention model, an estimated deposition rate from a sediment core and a simulation model predicted higher mass retention of phosphorus but similar percentage retention.SommaireUn marecage qui côtoie le lac Erie (USA) a servi de site expérimental pour en déterminer les budgets d'eau et de phosphore, de même que pour la variation spatiale et temporelle du phosphore et d'autres facteurs chimiques. Le marécage a été influencé par: niveaux d'eau qui changeaient; seiches; sédiments mouvants du littoral; et afflux de la ligne de partage des eaux dans une année de grande sécheresse. Le budget d'eau dans une période de 7 mois (mars–septembre 1988) montre un afflux de 15 200 m³ jour^–1 de la ligne de partage, et 3.5 m³ jour^–1 du lac Erie. Le volume du marécage a augmenté par 700 m³ jour^–1 malgré une sécheresse qui a produit plus d'évapotranspiration (80%) que de pluie pendant qu'une plage-obstacle a isolé le marecage du lac Erie pendant 77% de la période d'observation. La conductivité a diminué par 34% pendant que l'eau coulait, et la turbidité et les TSS ont varié, tout en démontrant des statistiques similaires à l'afflux et au déversement. Les moyennes pour les concentrations du total du phosphore à l'afflux et au déversement ont été similaires (247 and 248 µg P l^–1), quoique le TSP et le SRP ont diminué (=0.05) de l'afflux au déversement (donant des moyennes de 94 à 45 µg P l^–1 et de 7.5 à 4.0 µg P l'^–1). Les budgets de substances nutritives pour les données suggèrent une reténtion de 36% du phosphore, évidemment dans les sédiments (0.8 mg P m^–2 jour^–1). Un modèle pour la rétention des nutrients, un taux de déposition, estimé par un noyau de sédiments, et une simulation avaient prédit un plus grand taux de rétention de phosphore, mais un pourcentage similaire pour la rétention.From a paper presented at the Third International Wetlands Conference, 19–23 September, 1988, University of Rennes, France.     

The origin of the salmonid fishes: marine, freshwater... or neither?

The evolutionary origins of the salmonidfishes, whether in freshwater or the sea, havebeen debated for centuries. Early viewsfavoured a group of marine ancestry invadingfreshwaters; more recently, there was a shifttowards a freshwater ancestry, on grounds thata return to freshwater to spawn indicates theancestral biome. Salmonids are widely believedto share an ancient common ancestry with thenorthern hemisphere Osmeridae and southernhemisphere Retropinnidae and Galaxiidae. Salmonidae are diadromous, as are Osmeridae,Retropinnidae and Galaxiidae. This suggeststhat diadromy is an ancient behavioralphenomenon across all these groups, that theshared common ancestry of these groups was alsodiadromous, and that the ancestry of Salmonidaewas neither marine nor freshwater, but wasamongst diadromous fishes. This begs thequestion of whether this common ancestor wasmarine or freshwater, a question for which ananswer seems likely to be elusive.