Drift-pump and drift-net—two devices for the collection of bottom-near drifting biota

A low-volume submersible drift-pump unit is described for the collection of demersally drifting biota, particularly for shallow aquatic situations. This unit collects less motile biota quantitatively (so far zooplankton, larvae of macrofauna, and meiofauna are successfully collected). It can easily be modified for the sampling of a variety of other aquatic organisms, in particular nano- and picoplankton (algal, bacterial, fungal and viral plankton) at high temporal and spatial resolution. A new drift-net unit allows qualitative comparisons of demersally drifting invertebrates. Both light-weighted stationary systems can be modified for sampling at varying distances from the bottom and are suggested for fine-scale appliances at moderate depths from shore, pier, boat, or deployed by divers.     

Biomechanics and energy cost of the amphipod Corophium volutator filter-pump

The integrated function of the setal filter-basket and the pleopodal pump in the burrowing amphipod Corophium volutator was studied by video-microscopy in order to evaluate the energy costs of filter feeding. Video-microscope observations indicated that, in general, nine short, water-pumping beat cycles of the pleopods are succeeded by one slow cycle that coincides with cleaning of the setal filter and transient slowdown of inhalant water velocity. The position of the plumose setal filter on the second pair of gnathopods ensures that all water runs through the filter-basket. The fine V-shaped bristles on the setae enlarge the total filter area so that the velocity of water flowing through the filter is relatively slow, about 2.5 mm s(-1), giving rise to a resistance of about 2.9 mm H(2)O, which is the most important contribution to the total pressure drop in the system. In "standard" individuals of C. volutator with lengths of 3 and 6 mm, the normal operating pump pressure and pumping rate were, respectively, 2.6 and 3.1 mm H(2)O, and 18.3 and 85.5 ml h(-1); the overall pump efficiencies were 5.1% and 11.6%, respectively. These results show that the Corophium filter-pump is comparable to other low-pressure biological pumps in filter-feeding marine invertebrates, such as mussels, polychaetes, ascidians, and bryozoans.     

Relative Sensitivity Distribution of Freshwater Planktonic Crustaceans to Trace Metals

Cladocerans and copepods are common inhabitants of ponds and lakes, but assessments of the toxic effects of chemicals on aquatic organisms are often based mainly on toxicity data for cladocerans of the genus Daphnia. The paucity of toxicity data for copepods and other species of cladocerans raised the question whether toxicity data derived primarily from daphniids can be extrapolated to protect other planktonic organisms. In this study, we address this question by systematically comparing between the sensitivities of cladocerans and copepods to the metals Cd, Cu, Pb, Ni, and Zn using the species sensitivity distributions. Our results indicate that cladocerans are consistently more sensitive than copepods to Cd and Cu. Most importantly, sensitivities of D. magna, D. pulex, and Ceriodaphnia dubia, the three most commonly tested cladocerans, to these metals are higher than those of most copepod species and fall within the range of those exhibited by other cladocerans. C. dubia, a cladoceran with relatively small body size, is more sensitive to all metals than most other cladoceran species. Our results imply that water quality criteria of trace metals derived from datasets dominated by Daphnia are likely also protective to copepods and most other cladocerans.     

A vacuum benthos sampler suitable for diverse habitats

The vacuum benthos sampler consists of a vacuum chamber equipped with a collecting net connected to the intake of a 12 volt pump, a battery, and a standpipe. Contents of the standpipe are vacuumed while substrate is removed and washed with the exhaust hose. The vacuum chamber is designed for rapid changing of nets during replicate sampling. This sampler is equally efficient in flowing and standing water. It was more effective than a modified Hess sampler for collecting a large variety of benthos from flowing (ca 0.25–0.75 m/s) riffles. Required operation time is variable, but 93% of invertebrates caught in 10 min were captured in the first 5 min during our tests, and there was a 94% mean recovery of released organisms during 10 min of subsequent operation. Advantages over previous suction samplers include interception of organisms before they pass through a pump, return of outlet water to the standpipe, capability of sampling in shallow (20–30 mm) water, and that it can be carried and operated by one person.     

Diel variation in feeding rate and prey composition of herring and mackerel in the southern Gulf of St Lawrence

Diel feeding patterns of herring Clupea harengus and mackerel Scomber scombrus in the southern Gulf of St Lawrence were examined based on samples obtained by midwater trawling between 19 and 26 June 2001. Within 3 h time periods, stomach contents tended to be more similar between fish from the same tow than between fish from different tows. Thus, in contrast to previous diet studies, which have used individual fish stomachs as independent observations, tow was used as the experimental unit in statistical analyses in this study. Diel patterns in stomach fullness were identified using generalized additive models. Two peaks in stomach fullness occurred for herring, one in the morning and the other in the evening. Mackerel showed an increase in feeding intensity throughout the day with a peak in mid‐afternoon. The diel changes in stomach contents suggested rapid gastric evacuation rates for both species, especially for herring. The estimate of the instantaneous evacuation rate for herring was twice that for mackerel. Calanus copepods (mainly C. hyperboreus ), fishes (mainly capelin Mallotus villosus ) and euphausiids were the main prey found in the stomachs of both species. Calanus copepods dominated the diet of herring regardless of time period. They also dominated the diet of mackerel during the late afternoon, evening and night while fishes and euphausiids were dominant during the morning and early afternoon. These diel patterns emphasize the need for sampling throughout the day and night in order to estimate ration and diet composition for bioenergetic and ecosystem models.     

A Comparison of the Efficacy of Pond-Net and Box Sampling Methods in Turloughs - Irish Ephemeral Aquatic Systems

Two methods were used to sample aquatic macroinvertebrates in three turloughs. Turloughs are systems that flood periodically from groundwater, in response to local rainfall patterns and contain rare aquatic species and assemblages. The first method used a standard pond net that was swept through the water column, while the second involved fixing a rectangular, open-bottomed box to the substrata and removing all organisms with a net. Similar overall sampling effort was applied to each method and individual box samples were found to take longer to gather than pond net samples. The box method, however, gave the maximum yield for a given sampling effort. Significantly more beetle species and individuals were recorded per unit area of bottom at all three turloughs using the box method. Multivariate analysis segregated samples, firstly according to site and secondly, with respect to method. The box method is a viable alternative to sampling with a pond net. It is more quantitative, objective, specific and reliable. This is particularly important in habitats distinguished by rare species and assemblages, and for which monitoring is driven by legislative needs.     

Preparation of cell envelopes of large numbers of individual bacterial strains with the use of an automatic cell disruptor

Analysis of the cell envelopes of large numbers of bacterial strains is used for the epidemiological and taxonomic investigation of clinical, veterinarian, and ecological isolates. Isolation of cell envelopes requires lysis of the bacteria. We developed an apparatus to disrupt bacterial cells of 200 different isolates in suspension by ultrasonication automatically. It is composed of modified standard laboratory equipment (fraction collector, cooling unit, pump), a standard ultrasonifier, and a newly designed control unit, which includes a sampler. This apparatus was applied to the analysis of cell envelope proteins of 96 Haemophilus influenzae strains on sodium dodecyl sulfate-polyacrylamide gel electrophoresis within 3 days after the first culture.     

Effect of hydropower peaking flow fluctuations on community structure and feeding guilds of invertebrates colonizing artificial substrates in a large impounded river

Artificial substrates were used to monitor the invertebrate communities below a power peaking impoundment and a flow re-regulating impoundment on the Missouri River on northeastern Nebraska, USA. Invertebrate communities on shallow samplers subjected to exposure from diel fluctuations in flow averaged 3 taxa per sampler and 91 organisms per square meter. In the absence of diel fluctuations, number of taxa per sampler increased to 12 and mean densities increased to 743 per square meter. Fluctuating discharges had no significant effect on numbers of taxa or densities on continually submerged artificial substrates. However, greater numbers of taxa and total densities were observed on deep (107 cm) versus shallow (30 cm) samplers below both impoundments.Polycentropodidae (Trichoptera), Chironomidae (Diptera) and Oligochaeta were observed to tolerate diel fluctuations and exposure below Fort Randall Dam while Hydropsychidae (Trichoptera) and Heptageniidae (Ephemeroptera) were extremely intolerant.Collector-gatherers and predator-engulfers were the predominant functional groups colonizing samplers below both impoundments. Higher numbers of collector-gatherers, collector-filterers and scrapers were observed from samplers in the absence of diel flow fluctuations.This study corroborates results from a number of other investigations, separated in space and time. Examined collectively, these studies provide the framework for understanding power peaking as a stress to benthic stream communities.     

Comparison of nets and pump sampling gears to assess zooplankton vertical distribution in stratified lakes

The efficiency of a cantilevered bridle net was tested in comparisonwith a Wisconsin net and a pumping system to sample zooplanktonorganisms in three water layers (epi-, meta- and hypolimnion)of three Canadian Shield lakes. Variations among samplers werecompared to variations due to within-lake vertical distributionof zooplankters and among lake variations. For each lake andwater layer, we also assessed the efficiency of the three methodsaccording to the catches of zooplanktonic taxa. The highestpercentages of variation were generally due to lake or water-layereffects; interaction between sampling gears and water layerswas above 50% for most taxa, except cladoceran. Sampling methodsexplained more variation than the lake effect for some zooplanktontaxa, indicating that using different sampling devices couldpotentially alter the among-lake variation interpretation ofzooplankton abundance. The pumping system captured higher densitiesof animals per taxa than the cantilever and the Wisconsin nets.The cantilever net generally captured mobile taxa more efficiently(Polyarthra vulgaris, copepods, Daphnia sp., Diaphanosoma brachyurumand chaoborids) than the Wisconsin net and the pumping system,but its efficiency varied among water layers.     

Comparison of two samplers for quantitatively collecting larval fishes in upper littoral habitats*

Performance of two larval fish samplers, a hand–towed net and a dropbox enclosure, was similar when tested in shallow (x water depth, 20 cm) upper littoral–zone habitats. There was no significant difference between means of larval fish density (by total catch and by species) estimated from the catch in each gear, during the day and at night. Mean length of larvae (total catch) from the tow net was significantly longer than that from the dropbox during the day, but mean length did not differ between gear at night. Mean lengths of larvae of each species between gear were not significantly different within each period. Both gears collected significantly longer larvae (total catch and by species) during the day than at night probably because of diel movements of larvae of different sizes and species.     

Comparison of three zooplankton samplers: a taxon-specific assessment

We compared densities of zooplankton captured by three commonzooplankton samplers during 24 h. A tube sampler generally yieldedzooplankton densities equal to or greater than those from avertical net tow or a Schindler-Patalas trap. Exceptions includedherbivorous rotifers and Diaphanosoma. Because rotifer densityusually was greatest in the deepest stratum sampled (i.e. nearthe bottom of the tube), water loss with lifting probably accountedfor reduced rotifer capture. Why the tube and the Schindler-Patalastrap were less efficient than the net for Diaphanosoma remainsunclear. Because tubes sample the entire water column, providingzooplankton densities comparable with traditional gear, theyare a time-saving alternative for zooplankton sampling in shallowlakes and weedy littoral zones. ²The Unit is sponsored jointly by The United States Fish andWildlife Service, Ohio Department of Natural Resources, TheOhio State University and the Wildlife Management Institute.     

Modifications of the Ekman Sampler

Many types of sediment samplers have been designed for specific purposes and for sampling in different aquatic environments. The objective of this technical note has been to introduce two specific improvements of the traditional Ekman grab sampler, which is a well-known apparatus for sampling of soft sediments, especially in bottom faunistic contexts. The two new modifications concern the automatic closing mechanism. The jointed quadrant and the jointed, hooked axis, both made of brass, provide a much handier and more reliable operation than, e.g., the traditional automatic mechanism.     

Field studies measuring the aerosolization of endotoxin during the land application of Class B biosolids

Endotoxins are a component of Gram-negative bacteria cell walls and are known to be present in biosolids. Endotoxins have been shown to be potent stimulators of the innate immune response causing airway irritation and shortness of breath. Class B biosolids are routinely applied to agricultural lands to enhance soil properties and can be used as an alternative to chemical fertilizers. This study investigated the aerosolized endotoxin dispersed during the land application of Class B biosolids on agricultural land and a concrete surface at two sites in Colorado, USA. Aerosolized endotoxin was captured using HiVol samplers fitted with glass fiber filters, polycarbonate filter cassettes (both open and closed) and BioSampler impinger air samplers. Endotoxins were also measured in the biosolids to allow for correlating bulk biosolids concentrations with aerosol emission rates. Endotoxin concentrations in biosolids, impinger solutions and filter extracts were determined using the kinetic Limulus amebocyte lysate assay. Aerosolized endotoxin concentration was detected from all sites with levels ranging from 0.5 to 642 EU/m³. The four types of sampling apparatus were compared, and the HiVol and open-faced cassette samplers produced higher time-weighted average (TWA) measurements (EU/m³) than the impinger and closed cassette samplers. Ambient wind speed was found to be the variable best describing the observed results with optimal wind speed for highest deposition estimated at 5 m s^?1. It is argued that HiVol air samplers are a particularly reliable approach and subsequent analyses relating TWA measurements to wind speed and biosolids characteristics were based on the measurements collected with those samplers.     

In situ isolation of allelochemicals released from soft corals (Coelenterata : Octocorallia): A totally submersible sampling apparatus

A submersible apparatus has been developed which permits in situ sampling of allelochemical substances released from sessile marine organisms. Concentration of the allomones from sea water is achieved by adsorption on SEP-PAK C-18, reverse-phase cartridges. The procedure is performed under water and causes minimal disturbance to the organism while in its natural habitat. Design and application of this apparatus are detailed.

The isolation and identification of toxins released by two species of alcyonarian corals (order Alcyonacea) are described. This represents the first direct in situ isolation of water-borne allelochemicals released from a marine organism.     

A marine biological underwater depuration system (MUDS) to process waste waters

An underwater device, able to favour the sea auto-cleaning capacities, is herein described. This system, called MUDS (marine underwater depuration system), consists of a percolating filter and is placed at sea over an urban sewage outflow of a submarine pipeline. Due to the density difference, the water effluent flows through the percolating filter: this favours the mixing and a prompt recycling of organic matter, activating a marine trophic web. Rich microbenthic communities develop on the MUDS, both interstitially, inside the filter, and on the structure. The community mainly consists of ciliates, nematodes, harpacticoid copepods and polychaetes, all of which being organisms that increase the depuration efficiency by consumption of organic matter. This structure acts also as a deterrent for the illegal trawling activity in the area, and attracts large numbers of several finfish species, thus working as a fish aggregating device (FAD). It is possible to utilise this underwater device for medium littoral towns with strong differences in effluent discharges during the year, where the use of land-built effluent treatment plants is too expensive.     

池塘养殖匙吻鲟与鳙胃肠道饵料生物的比较

通过对同一试验池中匙吻鲟（Polyodon spathala）和鳙（Aristichthys nobilis）胃肠道内含物的连续3次分析,揭示他们滤食的天然饵料生物组成及差异。首先根据物种鉴定结果对2种鱼的胃肠道内饵料生物组成进行了UPGMA聚类分析,结果显示:相同采样时间同一池塘内2种鱼饵料生物组成存在差异,分别聚为不同的分枝;分析匙吻鲟和鳙胃肠道内饵料生物种类时还发现不同采样时间前者枝角类和桡足类种类数均多于后者。同时对2种鱼胃肠道内各饵料生物的生物量进行分析,结果显示:当大型饵料生物充足时,枝角类和桡足类的生物量在2种鱼胃肠道内没有显著差异（P0.05）;当大型饵料生物减少时,匙吻鲟摄食强度减小,但其枝角类和桡足类的生物量仍显著较大（P0.05）;当大型饵料生物消失后,轮虫生物量在匙吻鲟胃肠道内显著增加 （P0.05）;相比较,鳙在各采样期则主要滤食较小型的浮游动物和浮游植物。另外,当动物性饵料减少后,匙吻鲟和鳙均通过大量滤食植物絮团来补充能量。综上,同一试验池养殖的匙吻鲟和鳙存在摄食竞争压力,该压力的大小与环境中大型饵料生物的丰富度密切相关。       

Survival of genetically engineered Escherichia coli in natural soil and river water

Twelve derivatives of Escherichia coli strain HB101 which contained different sizes of plasmids ranging from 3.9 Kb to 48 Kb and encoding resistance to various antibiotics were used. When these organisms were introduced into natural river water, the population declined rapidly and by day 3, the majority (i.e. more than 99.9%) of them could no longer be detected on antibiotic-amended culture plates. If the river water was filter sterilized first, the added organisms maintained their population for up to 7 d without any significant decrease in numbers. Similar results were also observed in sterilized tap water or distilled water. This indicated that the disappearance of these organisms in the aquatic environment was caused mainly by biotic factor(s). The loss of the ability to grow in the presence of antibiotics by some of the E. coli was not observed unless they were allowed to grow in the antibiotic-free environment first. When the test organisms were added to natural silt loam, a large portion of the original population still remained viable after 16 d. There was no relationship between the percentage survival of E. coli in natural river water and the sizes of plasmid harboured. On the other hand, when these bacteria were added to natural soil, survival appeared to increase as plasmid size increased. and accepted 19 August 1989     

Survival of genetically engineered Escherichia coli in natural soil and river water

Twelve derivatives of Escherichia coli strain HB101 which contained different sizes of plasmids ranging from 3.9 Kb to 48 Kb and encoding resistance to various antibiotics were used. When these organisms were introduced into natural river water, the population declined rapidly and by day 3, the majority (i.e. more than 99.9%) of them could no longer be detected on antibiotic-amended culture plates. If the river water was filter sterilized first, the added organisms maintained their population for up to 7 d without any significant decrease in numbers. Similar results were also observed in sterilized tap water or distilled water. This indicated that the disappearance of these organisms in the aquatic environment was caused mainly by biotic factor(s). The loss of the ability to grow in the presence of antibiotics by some of the E. coli was not observed unless they were allowed to grow in the antibiotic-free environment first. When the test organisms were added to natural silt loam, a large portion of the original population still remained viable after 16 d. There was no relationship between the percentage survival of E. coli in natural river water and the sizes of plasmid harboured. On the other hand, when these bacteria were added to natural soil, survival appeared to increase as plasmid size increased.     

Evaluation of four sampling devices for Burkholderia pseudomallei laboratory aerosol studies

Previous field and laboratory studies investigating airborne Burkholderia pseudomallei have used a variety of different aerosol samplers to detect and quantify concentrations of the bacteria in aerosols. However, the performance of aerosol samplers can vary in their ability to preserve the viability of collected microorganisms, depending on the resistance of the organisms to impaction, desiccation, or other stresses associated with the sampling process. Consequently, sampler selection is critical to maximizing the probability of detecting viable microorganisms in collected air samples in field studies and for accurate determination of aerosol concentrations in laboratory studies. To inform such decisions, the present study assessed the performance of four laboratory aerosol samplers, specifically the all-glass impinger (AGI), gelatin filter, midget impinger, and Mercer cascade impactor, for collecting aerosols containing B. pseudomallei generated from suspensions in two types of culture media. The results suggest that the relative performance of the sampling devices is dependent on the suspension medium utilized for aerosolization. Performance across the four samplers was similar for aerosols generated from suspensions supplemented with 4% glycerol. However, for aerosols generated from suspensions without glycerol, use of the filter sampler or an impactor resulted in significantly lower estimates of the viable aerosol concentration than those obtained with either the AGI or midget impinger. These results demonstrate that sampler selection has the potential to affect estimation of doses in inhalational animal models of melioidosis, as well as the likelihood of detection of viable B. pseudomallei in the environment, and will be useful to inform design of future laboratory and field studies.