摘要:

An underwater corer has been developed capable of taking 10-cm diam cores up to 1 m long from unconsolidated, fine-grained fluvial and lacustrine sediments including organic-rich (gyttja-like) deposits. The corer is lightweight and compact for transport and hand operation from float planes and small boats. It is of the piston type and has a sphincter valve for core retention. A miniature optical sensor triggers the corer when the sediment–water interface is penetrated. The corer is compatible with a system to subdivide the cores by vertical extrusion.Key words: corer, sediment, piston, sampling

ISSN:0706-652X    

DOI:10.1139/f79-039

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A simple exponential model is used to interpret the simultaneous uptake and clearance ofp,p′-DDT by euphausiids and copepods to and from seawater,where [C] and [W] are the concentrations in the organism and seawater, respectively. The clearance rate constant for euphausiids,kj = 0.043/d, is not significantly different from that observed for copepods, 0.048/d. No trend inkivalues is detected over the range ofp,p′-DDT concentrations in seawater used, 27.8–1388 ng/L. Furthermore, there is a great deal of overlap in the uptake rate constant values between organisms. Uptake rate constants range from 0.76 to 1.21 × 104/d for euphausiids and from 1.04 to 2.51 × 104/d for copepods. There appears to be no need to use a surface-area term if the concentration ofp,p′-DDT in the organism is expressed per unit dry weight even though the euphausiids are 2 orders of magnitude larger than copepods. Knowing levels of ΣDDT present in planktonic crustaceans in nature, back calculations suggest that there must beΣDDT/L in seawater. A considerable amount of the ΣDDT reported in seawater must therefore be unavailable to plankters because it is "bound" to particles.Key words:p,p′-DDT, uptake, clearance, surface area, euphausiids, copepods

ISSN:0706-652X    

DOI:10.1139/f79-040

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Pleomerism, the increase in vertebral number with maximum recorded length for species within a family, may be explained for fish by hydrodynamic considerations. A model is developed that suggests that the upper limits of the slope of the relation between log vertebral number and log length should be 0.43 in laminar flow and 0.35 in turbulent flow. These slopes are compared with those of previous studies only with difficulty because (1) those values were for predictive rather than functional regressions, (2) the slope will depend on the range in length of various species across temperature zones, and (3) no distinction was made between structural and locomotor vertebrae. Variations in shape also complicate the relation between vertebral count and length, there are latitudinal factors involved, and maximum length is probably only a weak correlate of the length at which natural selection may be concentrated. When these factors are considered, it is to be expected that observations would provide only a rough approximation to theory.The theory underlying the model is also used to derive a formula for the stride length of fish motion that is then compared with empirical results.Key words: vertebrae counts, body size, locomotion, hydrodynamic equations, mathematical model, stride length

ISSN:0706-652X    

DOI:10.1139/f79-041

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Concentrations of Cd, Pb, and three essential metals (Cu, Mn, and Zn) in stocked bluegill (Lepomis macrochirus) and eight resident species of fish were studied in an acidic, highly organic pond on the southeastern U.S. coastal plain. Concentrations of Cu, Mn, and Zn in stocked and resident fish were apparently homeostatically controlled in liver tissue, axial musculature, and whole body. Concentrations of all metals studied in axial muscle tissue and whole body of stocked bluegill remained relatively constant after 200 d of residence in the pond. Analysis of concentration factors from pond water to whole stocked bluegill indicated that Pb in this system was less available to fish than in hardwater lakes. In contrast, Cd in the pond was as available to fish as in harder waters. Differences in relative availabilities of Cd and Pb were explained by the tendency of Pb to form complexes with naturally occurring organics. The need for metal-specific analysis of biological availability of metals in highly organic softwater systems is stressed.Key words: trace metal, availability, fish, soft water, concentration factor, organic water

ISSN:0706-652X    

DOI:10.1139/f79-042

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Atlantic salmon (Salmo salar) were found to be as susceptible as coho salmon (Oncorhynchus kisutch) to Maine–New Hampshire strains ofVibrio anguillarumused in both injection and water transmission exposure. Exposure to 1–2.5 × 105organisms/mL of one strain (569) in the water for 1 h killed 80–100% of Atlantic salmon at 10 and 15 °C. Should similar water exposure conditions occur in Maine estuaries, newly released Atlantic salmon smolts may encounter lethal levels ofV.anguillarum.Key words:Vibrio anguillarum,Salmo salar, Atlantic salmon, susceptibility, marine bacteria.

ISSN:0706-652X    

DOI:10.1139/f79-043

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Iodine balance was studied in immature rainbow trout (Salmo gairdneri) held at 12 °C in water of iodine content 1.85 μg/L and fed daily 1% of body weight with food containing 0.48 μg I/g. Iodide flux into the plasma pool was 148 ng I∙h−1∙100 g−1of which < 1% was contributed by peripheral deiodination of thyroid hormones, up to 16% was obtained from the diet, and at least 84% was derived from the water. Less than 5% of iodide intake was required to satisfy thyroidal secretory demands. Testosterone injections elevated plasma iodide and protein levels, but did not alter the rate of plasma iodide turnover.Key words: trout, iodine balance, thyroid function, testoste

ISSN:0706-652X    

DOI:10.1139/f79-044

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Phosphorus is undoubtedly the major plant nutrient controlling phytoplankton growth in the upper Great Lakes and the nutrient responsible for accelerated eutrophication in the lower Great Lakes. No studies published before 1970 provide conclusive evidence of the specific roles of phosphorus and other nutrients as growth limiting factors for phytoplankton. Improper citation of references can inadvertently cast doubt on the key role of phosphorus, or denigrate uncited work, depending on the reader's background.Key words: phosphorus, nitrogen, eutrophication, phytoplankton, limiting nutrients, Lake Michigan, Lake Superior, Lake Huron

ISSN:0706-652X    

DOI:10.1139/f79-045

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f79-046

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Sampling variability in benthic studies may result from sampling device operation, physical features of the environment, laboratory sorting procedures, and biological features of study populations. Selected factors and procedures that influence variability, samplers affected, and proposed remedies are presented. Consequences of not considering autecological components in sampling designs are illustrated by analysis of larval counts ofCheumatopsyche pettiti(Banks), a multiple cohort caddisfly with an aggregated population. The range of mean numbers ofC.pettitiwas great with low sample numbers. Aggregation is more reliably measured at low sample numbers with the Index of Dispersion and the Mean Crowding Index than with the dispersion parameterk, the calculation of which from the maximum-likelihood equation, is integrally related to sample size. Nonrandom patterns ofC.pettitiobserved from samples collected in an Indiana, USA, stream riffle, may result from a failure to consider hyporheic distributions, spatial influences (e.g. sampling both favored and nonfavored microhabitats), instar-specific differences, and behavioral features. Variability in secondary production estimates of an aggregated population ofCeraclea ancylus(Vorhies) from a Kentucky, USA, stream indicated similar relationships to sample size.The size of the mean, the degree of aggregation, and the desired precision of the mean estimate will influence the number of samples required to estimate densities of benthic populations. Sample size requirements calculated from data reported in previous studies were high to achieve accepted levels of precision. Habitat stratification may reduce the numbers of samples required.Dicosmoecus gilvipes(Hagen) exhibited nonaggregated patterns and required fewer samples to estimate density in uniform substrate areas of a California, USA, river pool than did aggregated populations in both mixed substrate areas and the entire pool.Ceraclea ancylusrequired fewer samples for density estimates in stratified (by habitat or substrate type) than unstratified habitats, the fewest samples being necessary when the individual stone was the sampling unit. Judicious choice of study populations may permit larger numbers of samples to be collected and processed with reduced cost, as an alternative to stratification. Larvae ofC.ancylusandD.gilvipescould be separated in the field; density underestimation due to a hyporheic population component was eliminated because of surface dwelling behavior or by choice of study sites; and compounded spatial distributions due to co-occurring instar-specific patterns were absent because the populations have a single cohort.Larger numbers of samples may be necessary than are generally taken in benthic studies. Further research is needed to assess variability in secondary production estimates and community diversity analyses. Improved methods for substrate surface area estimation and increased use of experimental approaches and sequential sampling techniques should be considered in future benthic sampling designs.Key words: sampling, benthos, aquatic, macroinvertebrate, Trichoptera, insect, experimental design, autecology, life history, variability

ISSN:0706-652X    

DOI:10.1139/f79-047

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Life history of benthic freshwater invertebrates, excluding insects, may influence a number of features of sampling programs, such as the environment sampled, sampling technique or equipment used, frequency and timing of sampling, and mesh sizes of nets or sieves. Consideration of the life history should increase the effectiveness of the program and, in the extreme, may allow one to recognize artifacts that would otherwise lead to incorrect conclusions.Aspects of life history that influence sampling programs are (1) direct or indirect embryonic development and the extent to which young are sampled simultaneously with adults during the breeding season, (2) times of year when various developmental stages are present, (3) differences in size between various life stages necessitating use of more than one sampling method during the year, (4) change in habitat due to migrations or assumption of a pelagic, parasitic, or aerial existence for part of the life cycle, (5) change in mobility over the life cycle, (6) sex differences in size or behavior, and (7) adaptations to adverse conditions. Examples of ways in which life history affects sampling are based on the literature and on original data on the opposum shrimp,Mysis relicta, and the crayfish,Orconectes virilis.We recommend that quantitative studies of benthic invertebrate communities be started with a pilot study employing at least two complementary sampling techniques and sufficiently frequent sampling times to allow the development of a reliable strategy for the objective.Key words: life history, sampling, benthic invertebrates, Crustacea,Mysis relicta,Orconectes virilis

ISSN:0706-652X    

DOI:10.1139/f79-048

出版商:NRC Research Press    

年代:1979

数据来源: NRC