Vertical distribution and seasonal variation of eelgrass beds in Iwachi Bay,Izu Peninsula,Japan

The vertical distribution and population structure of eelgrass beds were surveyed in Iwachi Bay, along the Pacific coast of central Japan. Samplings were conducted from May through November 1977 by SCUBA. Eelgrass was distributed between 3 and 11 m in depth. The relative light intensity at 12 m depth was 11% at the lower range. The highest population density was 290 shoots/m² in September and the fresh weight of biomass was 888 g/m² in July at 7 m depth. The maximum mean leaf area index was about 3 at 10 m depth in July. The ratio of reproductive shoots to the total shoots was about 36% at 7 m depth in June. Eelgrass showed good growth at 7–10 m depth, which is comparatively deeper than other eelgrass habitations. The high values of water transparency and sunshine duration, as well as solar radiation compared with other localities was believed to contribute to the growth of eelgrass in deeper waters in Iwachi Bay.     

The response of interstitial ammonium in eelgrass (Zostera marina L.) beds to environmental perturbations

Natural and human-induced perturbations of eelgrass (Zostera marina L.) beds were used to examine the interaction between the sediment interstitial ammonium pool and nitrogen uptake by the plants. Eelgrass colonization of unvegetated areas was accompanied by a substantial decrease in the interstitial ammonium pool over a 4-yr period. The changes in interstitial ammonium and shoot density during colonization support an already determined relationship between shoot density and ammonium pool measurements. In field perturbation experiments, removing eelgrass leaves and sealing the sediment surface altered the flux of ammonium from the interstitial ammonium pool, and resulted in a rapid increase in interstitial ammonium concentrations. Measurements of ammonium accumulation under the various perturbation conditions and a control permitted calculation of the sediment ammonium flux. These estimates include uptake by eelgrass roots, regeneration in the root zone, and diffusion from the sediments. Nitrogen limitation was observed in some eelgrass beds.     

Ecology and systematics of a new species of Uromunna (Crustacea: Isopoda) from Spanish eelgrass beds

Uromunna naherba sp. nov. is described from eelgrass beds (Zostera marina and Z. noltii) of the NW Iberian Peninsula. This is the second species of the genus reported from the NE Atlantic, after U. petiti. The new species was more abundant on rhizomes than on the leaves of the plants. Seasonal samples show that ovigerous females are present throughout the year, but become more abundant in late spring and summer, when adult males decrease in frequency. Ovigerous females appear in only one size class. Owing to the yearly productivity cycle of the eelgrasses, these data suggest that the species is semelparous and completes its lifecycle within 1 year. The taxonomic characters of the genus are discussed.     

Population structure and genetic diversity among eelgrass (Zostera marina) beds and depths in San Francisco Bay

The seagrass Zostera marina is widely distributed in coastal regions throughout much of the northern hemisphere, forms the foundation of an important ecological habitat, and is suffering population declines. Studies in the Atlantic and Pacific oceans indicate that the degree of population genetic differentiation is location dependent. San Francisco Bay, California, USA, is a high-current, high-wind environment where rafting of seed-bearing shoots has the potential to enhance genetic connectivity among Z. marina populations. We tested Z. marina from six locations, including one annual population, within the bay to assess population differentiation and to compare levels of within-population genetic diversity. Using 7 microsatellite loci, we found significant differentiation among all populations. The annual population had significantly higher clonal diversity than the others but showed no detectible differences in heterozygosity or allelic richness. There appears to be sufficient input of genetic variation through sexual reproduction or immigration into the perennial populations to prevent significant declines in the number and frequency of alleles. In additional depth comparisons, we found differentiation among deep and shallow portions in 1 of 3 beds evaluated. Genetic drift, sweepstakes recruitment, dispersal limitation, and possibly natural selection may have combined to produce genetic differentiation over a spatial scale of 3-30 km in Z. marina. This implies that the scale of genetic differentiation may be smaller than expected for seagrasses in other locations too. We suggest that populations in close proximity may not be interchangeable for use as restoration material.     

Long-term change in water transparency before and after the loss of eelgrass beds in an estuarine lagoon,Lake Nakaumi,Japan

Long-term changes in Secchi disk transparency in Lake Nakaumi, Japan, from 1932 to the present, which includes the periods before and after the loss of eelgrass (Zostera marina L.) beds, were compiled from previous reports. During the first (July 1932–February 1934) and the second (January 1949–November 1950) periods, the mean transparency was greater than 3 m at all observed stations. Data during the third period (July 1954–March 1956) are only available for the station at the center of the lake. The mean transparency during the third period was significantly lower than that of the second period but higher than the mean during the fourth period. This observation suggests that the decrease of transparency occurred during the third period. Because the decline of eelgrass beds in Lake Nakaumi occurred in the mid-1950s, the decrease of transparency most likely resulted from the shift in primary producers from submerged macrophytes to phytoplankton. Although the maximum transparency sometimes exceeded 3 m, mean transparencies during the fourth period (May 1975–December 2003) were less than 2 m at all stations, significantly lower than those during the first and second periods. The shift in the chief primary producer, from benthic macrophytes to phytoplankton, caused a subsequent shift in secondary producers. The opportunistic filter-feeding bivalve Musculista senhousia, regarded as a biofouling species of local fisheries, increased in Lake Nakaumi. The long-term monitoring data of transparency suggested that restoration of submerged aquatic vegetation may be indispensable for the remediation of the lake environment in this shallow eutrophic lagoon.     

Sulfur accumulation in eelgrass (Zostera marina) and effect of sulfur on eelgrass growth

Eelgrass (Zostera marina) was grown under exposure to high levels of sediment sulfides to examine their ability to reoxidize sulfides intruding into the plants. The plants were kept under full light (control and high sulfide level) and at 10% of light saturation (high sulfide level) for 3 weeks and growth and accumulation of elemental sulfur (S⁰) in the plants were examined. The growth rate was reduced with ∼75% in the low light treatment, whereas there was no significant difference between the rates at full light saturation. S⁰ was accumulating in the below-ground structures of the plants exposed to high sulfide concentrations with highest concentration in the youngest roots and oldest internodes. There was no accumulation of S⁰ in the leaves, suggesting that the intruding sulfides were reoxidized in the below-ground structures before reaching the leaves. The accumulation of S⁰ was higher in the roots of the low light treatment (up to two times) suggesting a larger intrusion of sulfides. These plants also appeared highly affected by the treatment with rotting meristems and increased mortality after the 3-week growth period. These results are the first to show an accumulation of sulfur compounds internally in seagrasses as a result of reoxidation of sulfides. The reoxidation is facilitated by the internal transport of oxygen and is an example of the advantage of the internal lacunae system in seagrasses.     

Application and assessment of a nutrient pollution indicator using eelgrass (Zostera marina L.) in Barnegat Bay-Little Egg Harbor estuary, New Jersey

Eutrophication degrades numerous estuaries worldwide and a myriad of assessment metrics have been developed. Here, we apply an example of a previously developed metric (Lee et al., 2004) designed to indicate incipient estuarine eutrophication to validate this technique in an already eutrophic estuary end-member, Barnegat Bay-Little Egg Harbor, New Jersey. The metric, termed ‘Nutrient Pollution Indicator’ (NPI) uses eelgrass (Zostera marina L.) as a bioindicator and is calculated as the ratio of leaf nitrogen content (%N) to area normalized leaf mass (mg dry wt cm⁻²). Eelgrass samples were collected along the entire length of the Barnegat Bay-Little Egg Harbor from June to October 2008 to determine if leaf chemistry and morphology reflect eutrophication status and a north-south gradient of nitrogen loading from the Barnegat Bay watershed. Nitrogen content, area normalized leaf mass, and NPI values all significantly (p < 0.05) varied temporally but not spatially. NPI values did not significantly correspond to the north-south gradient of nitrogen loading from the Barnegat Bay watershed. The NPI metric is therefore not deemed to reliably indicate estuarine eutrophic status. Differences between sampling effort (number of stations) and replication did not bias the overall conclusions.     

Comparative life cycle assessment of re-use and replacement for video projectors

Purpose

The current focus of environmental legislation for energy-using products is an efficient energy consumption in the use stage. However, the production and waste treatment of electronic products are also related to environmental impacts in terms of declining metal resources and growing waste streams. This paper investigates the environmental impacts of life time extension versus energy efficiency for the product group video projector using life cycle assessment (LCA).

Methods

The product under study was an average video projector based on three LCD projectors. The studied systems included two possibilities after a regular first usage period: reconditioning for a second use or replacement by a primary successor with an energy efficiency increase of 5 and 10%. All impacts addressed were accounted using the ReCiPe 2008 method. The impact contribution of projector components was identified at midpoint and endpoint levels, while life cycle impacts were calculated with a focus on three impact categories. Furthermore, the amortization period of production emissions was quantified.

Results and discussion

LCA results showed that the use stage dominates life cycle impacts of the global warming potential and primary energy demand. For the metal depletion potential, the production stage accounts for most of the total life cycle load. The highest shares in production emissions were identified for electronic components, namely printed wired boards and integrated circuits. Reconditioning and reuse of a secondary projector resulted in minor environmental impacts compared to the replacement and use of a primary projector with an energy efficiency increase of 5%. The saving potential of the primary energy demand is higher only in the case of a 10% more efficient device as compared to the secondary projector.

Conclusions

The study concluded that production emissions and their amortization period are relevant factors offsetting any environmentally beneficial measures applied during the use phase. The study suggests that life time extension of video projectors can provide higher environmental improvement potentials, while energy efficiency increase during usage is less beneficial, given that major improvements in energy efficiency do not occur. Recommendations are valid for this particular case study. The study suggests that the current focus of mandatory product requirements for energy-using products on energy efficiency increase should be extended to measures of life time extension in order to serve the intent of an integrated product policy.

     

Continuous cell suspension processing using magnetically stabilized fluidized beds

The behavior of a cell suspension in a continuous magnetically stabilized fluidized bed (MSFB) was investigated both experimentally and theoretically. The low, constant pressure drop and fluidity of the solids phase in the MSFB allowed a continuous countercurrent separator to be constructed. The magnetic field eliminated all motion of the solids phase (nickel spheres) and produced a device similar to a packed-bed depth filter. Yeast cells were used as the suspended solids and the performance of the MSFB filter was assessed as a function of the bed height, solids velocity, cell concentration, and liquid composition. Removal rates could be adjusted by controlling the cell/support interaction and were found to be as high as 99%. A mathematical model was used to aid in understanding this filtration and was found to agree qualitatively with all experimental observations. Comparison of the model with the data suggests that both cell/cell binding and cell shadowing are occurring.     

The structure and organization of an eelgrass fish fauna

Summary Ten species of fish made up more than 95 percent of the standing crop of the total fish assemblage of a shallow-water eelgrass meadow in southeastern Australia. The relative abundance of each species remained fairly constant from year to year during a four and a half year period. Four species were permanent residents, three moved over the meadow at high tide, and the juveniles of three species changed residence status as they grew. Most species exhibited distinct diel patterns of activity, four species were diurnal and five were nocturnal. Species foraged in different microhabitats and dietary overlap was very low amongst all but two species which had overlapping habitat, prey and prey size preferences, but had different diel activity periods. Data on production by prey and consumption of prey by these two fish species indicated that competition for food was probably responsible for the temporal separation of feeding niches. Predation by birds and fish appeared to be the major influence on the diel activity period of one fish species. The maintenance of the patterns of resource allocation among the remaining species is discussed and the organization of different seagrass fish faunas is compared.This is publication number 265 in the Ministry for Conservation, Victoria publication series. — Present address: Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada     

Electric-field exposure of persons using video display units

Electric fields produced by a selection of video display units have been measured over a frequency range from DC to 1 MHz. The magnitude and the time variation of the electric fields were both recorded by means of a single broadband capacitive sensor located on the surface of a simple simulation of the human body. The electric field at a given location was found to be the sum of three discrete components, each having a different spatial and time variation. These components are produced by, respectively, the charged CRT screen, the flyback transformer, and the low-voltage circuitry. For the units tested, operator exposures are substantially below the limits of existing workplace guidelines.     

An evaluation of video playback using Xiphophorus helleri

Video playback is being increasingly used as a technique for behavioural research. The importance of critically evaluating the effectiveness of video playback is clear, as available video technology is not designed for nonhuman visual systems. We discuss several aspects concerning the perception of video images that could lead to inconclusive or erroneous results. Researchers should verify that behaviour observed in response to video playback is comparable to behaviour observed in response to live animals. We conducted such a verification using live and video playback methods to measure female response to swords of varying lengths in the green swordtail, Xiphophorus helleri. Using both methods, female response appeared to be an increasing function of male sword length. Females did not differ in their response to live and video versions of noncourting, noninteractive males, however, females tended to prefer video playbacks of males with longer swords, a result that has also been found in experiments using live males. These results suggest that females express the same qualitative mating preference, but not necessarily the same quantitative preference, for sword length when viewing video stimuli. Several methodological factors that may contribute to an apparent difference in the strength of the preference are discussed. Despite these differences, both methods produced comparable results; female response to sworded males tended to increase as sword length increased. These experiments demonstrate that video playback is an effective method to measure female preferences accurately in X. helleri and provide an example of how video playback can be evaluated in other species. Copyright 2000 The Association for the Study of Animal Behaviour.     

Nitrate removal from three different effluents using large-scale denitrification beds

Simple technologies that remove nitrate from effluents and other point discharges need to be developed to reduce pollution of receiving waters. Denitrification beds are lined containers filled with organic carbon (typically wood chip or coarse sawdust) and are a technology that is proving promising. Water containing NO₃^? (treated effluent or agricultural drainage) is passed through the bed and the wood chips act as an energy source for denitrifying bacteria that convert NO₃^? to N gases. There are few data on the efficiency of NO₃ removal in large-scale beds. We report here NO₃^? removal results from three large denitrification beds with volumes of 83, 294, and 1320 m³ treating dairy shed effluent, treated domestic effluent and glasshouse effluent, respectively. Nitrate was nearly completely removed from the dairy shed effluent (annual load of 31 kg N) and domestic effluent (annual load 365 kg N). In these beds, NO₃^? removal, presumably by denitrification, was limited by NO₃^? concentration. However, the bed treating glasshouse effluent was overwhelmed by very high NO₃^? concentration (about 250 g N m^?3) and high flow rates (about 150 m³ d^?1) but still reduced NO₃^? concentration to about 150 g N m^?3. For this bed, long-term NO₃^? removal was between 5 and 10 g N m^?3 of bed material when NO₃^? was non-limiting and was similar to rates reported for other smaller denitrification beds. As expected, organic N, ammonium and phosphorus were not removed from any of the effluents following passage through the beds. Our results suggest that denitrification beds are a relatively inexpensive system to construct and operate, and are suitable for final treatment of a range of NO₃^?-laden effluents.     

Measurement of fluorescence using digital integration of video images

The authors describe a system for the quantitation of fluorescence light output by individual cells using the signal obtained from a silicon intensifier target video camera. The video image is digitized to 4 bits (16 levels), and a 512 X 512 matrix is constructed and stored in 128K of video memory. Areas to be measured are user-specified by means of a light pen entry system. Recorded intensities are integrated under microprocessor control to provide a measure of total fluorescence in the selected areas. The distribution of light intensities per pixel over the 16-level gray scale as well as morphometric data are also obtainable. Linear response to transmission and fluorescence standards was verified. Reproducibility of the system was evaluated using fluorescent beads and glutaraldehyde-fixed chick red blood cells, which gave coefficients of variation comparable to those obtainable from other systems. Measurements of DNA per nucleus of human diploid fibroblasts using Hoechst dye 33258 yielded the two sharp peaks corresponding to the 2C and 4C values of DNA expected from such cells. We conclude that digital video measurement of fluorescence provides meaningful data and has considerable promise as a sensitive tool for the quantitation of fluorescence at the cellular level.     

Sources of uncertainty in estimation of eelgrass depth limits

In coastal areas seagrasses have considerable ecological importance and respond to eutrophication pressures. Seagrasses have, therefore, become an important parameter for assessing ecological status of marine water bodies. In this study we analyzed the sources of uncertainty associated with the monitoring of the maximum depth limit of eelgrass (Zostera marina). Based on a long-term marine monitoring of eelgrass depth limit in Danish coastal waters we estimated the uncertainty contribution of years, divers, transects, and replicates in water bodies and their sub-areas. For all these components the absolute uncertainty increased with the maximum depth limit. We used either a Spheric or a Gaussian function to describe the relationship between uncertainty and the maximum depth limit for each variable. This parameterization of the depth-specific uncertainty allowed estimation of the total variance associated with monitoring, which can be used to evaluate monitoring designs. The variance components were included in a time budget for optimizing eelgrass monitoring. With a maximum time limit of 100 or 200 h allocated for monitoring, the design that resulted in the lowest variance of the estimated maximum depth limit used 2 or 3 divers, respectively, and involved 2 or 3 years of monitoring and 4–8 transects.     

Estimation of fish activity costs using underwater video cameras

Swimming speed and activity costs of dace ( Phoxinus eos × P. neogaeus ) were estimated in the field using underwater video cameras. Activity costs were estimated by converting swimming speeds and the number of movements into swimming costs. Average swimming speed ranged from 6.7 to 12.2 cm.s⁻¹ across 2 h periods and varied significantly among dates and time of day. The time spent swimming by dace ranged from 616 to 17 640 s 2 h⁻¹. Activity costs per 2h period ranged from 2.1 to 4O.2J 2h⁻¹ and were strongly correlated to the time spent swimming. Daily activity cost estimated using the cameras averaged 128.9J day⁻¹ and was equivalent to 1.7 times the standard metabolic rate. Activity cost predicted using a bioenergetic model in conjunction with independent estimates of consumption and growth rates averaged 138.8J day⁻¹. This study indicated that swimming characteristics and activity costs of dace varied significantly both within and among days. These analyses also indicated that equally valid activity costs for fish in the field can be estimated using video cameras and the difference between Consumption and growth rates.     

Visualization of intracellular ice formation using high-speed video cryomicroscopy

A high-speed video cryomicroscopy system was developed, and used to observe the process of intracellular ice formation (IIF) during rapid freezing (130 °C/min) of bovine pulmonary artery endothelial cells adherent to glass substrates, or in suspension. Adherent cells were micropatterned, constraining cell attachment to reproducible circular or rectangular domains. Employing frame rates of 8000 frames/s and 16,000 frames/s to record IIF in micropatterned and suspended cells, respectively, intracellular crystal growth manifested as a single advancing front that initiated from a point source within the cell, and traveled at velocities of 0.0006-0.023 m/s. Whereas this primary crystallization process resulted in minimal change in cell opacity, the well-known flashing phenomenon (i.e., cell darkening) was shown to be a secondary event that does not occur until after the ice front has traversed the cell. In cells that were attached and spread on a substrate, IIF initiation sites were preferentially localized to the peripheral zone of the adherent cells. This non-uniformity in the spatial distribution of crystal centers contradicts predictions based on common theories of IIF, and provides evidence for a novel mechanism of IIF in adherent cells. A second IIF mechanism was evident in ∼20% of attached cells. In these cases, IIF was preceded by paracellular ice penetration; the initiation site of the subsequent IIF event was correlated with the location of the paracellular ice dendrite, indicating an association (and possibly a causal relationship) between the two. Together, the peripheral-zone and dendrite-associated initiation mechanisms accounted for 97% of IIF events in micropatterned cells.     

Mapping of epicardial deformation using a video processing technique

A method has been developed to measure deformation of the canine epicardium during the cardiac cycle simultaneously in a number (eight) of small regions (1 X 1 cm2). Approximately 50 white markers (diameter 1.5 mm) are attached to the epicardium and their motion is recorded on tape by a video camera. Marker positions are detected by computer processing of the digitized images. In each region the three deformation parameters are calculated from the displacements of all markers in that region by means of a least-squares criterium. In the experimental situation in the center of the area of the epicardium analyzed the accuracy of measuring circumferential strain, base-to-apex strain and shear is +/- 0.005, +/- 0.005 and +/- 0.002 rad, respectively. The method has been applied in an experiment in which local ischemia of the left ventricular wall was induced by occluding the anterior descending branch of the left coronary artery. Healthy and ischemic regions could clearly be distinguished by the differences in deformation.     

Analysis of spermatozoa movement using a video imaging technique

 The aim of this paper is to present methods for a fully computerised analysis of spermatocyte movement. The technique were designed for processing pure images of spermatozoa captured from a light microscope. The techniques described allowed for the reduction of background light inhomogeneity and for the correct detection of moving cells and involved densitometric equalisation of background inhomogeneity and implementation of the dynamic threshold, adopted for the recognition of objects. The method for relating cells (found in each frame processed) to movement trajectories used heuristic rules, describing the behaviour of moving cells. This permitted samples containing high numbers of spermatocytes within the observed area to be processed with maximum accuracy. Accepted: 7 June 1996