摘要:

Within navigation pools of the upper Mississippi River, the caddisflyOecetis inconspicuauses molluscs for pupation sites. This association apparently forms out of the need ofOecetisfor a solid substrate to pupate on within a habitat dominated by soft shifting substrates.Oecetisgenerally colonized pelecypods and larger gastropods with an exposed shell surface area > 2.5 cm2.Oecetiswas found only on the posterior exposed end of clams, but occurred somewhat randomly on snails. Few pupae were found on dead molluscs.Oecetispupates on molluscs that can maintain a portion of their shell above the surface of the substrate, thus preventing pupal burial.

ISSN:0270-5060    

DOI:10.1080/02705060.1984.9664621

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Small (20 L) enclosures were used to study the effects of phosphorus addition and zooplankton removal on the phytoplankton of an acidic lake in the Adirondack Mountains of New York. Inspite of inorganic mechanisms which are capable of sequestering phosphate under acidic conditions the phytoplankton population bloomed after the addition of 80 μg L−1of phosphate as KH2PO4. The response was measured by cell counts of the dominant phytoplankter,Chlamydomonasand changes in chlorophyllaconcentration. About half the number of algal cells were present after the two week incubation when zooplankton were not removed, indicating that zooplankton herbivory can influence, but not totally control, the algal production.

ISSN:0270-5060    

DOI:10.1080/02705060.1984.9664622

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Two portable water filtration devices were evaluated for their effectiveness in removing potentially pathogenicGiardiacysts using a rigorous testing schedule that simulated in-field use. The units were challenged daily with untreated surface water containing known concentrations ofGiardiacysts and two motile, non-pathogenic protozoans according to a defined protocol, which included both use and non-use periods. Detection and quantitation of any challenge organisms were achieved by concentrating the filtration unit effluents by membrane filtration, backflushing the polycarbonate membranes, centrifuging the resulting backflush, and examining the concentrate microscopically. At no time during the 26-day testing period were anyGiardiacysts or other challenge protozoans isolated from the filtration unit effluents. Therefore, the two portable filtration devices tested are efficient in removing high concentrations ofGiardiacysts and other protozoans.

ISSN:0270-5060    

DOI:10.1080/02705060.1984.9664623

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Hilsenhoff's biotic index (HBI) is used for evaluating the water quality of Wisconsin streams. The variability of the HBI must be known or estimated in order to detect significant differences in water quality of various streams, at different locations in the same stream, or of the same location sampled at different times. Based on our study results, the best estimate of the HBI standard deviation(s) in fall samples is 0.197. From (s) and variance (s2= 0.0388) estimate we present 2 statistical procedures that test for significant differences between paired HBI values—the detectable difference (DD) method for equal sample sizes (statistically preferred), and the t-test for unequal sample sizes.

ISSN:0270-5060    

DOI:10.1080/02705060.1984.9664624

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Two eastern Pennsylvania populations of the cutlips minnow,Exoglossum maxillingua, were studied; one from the Delaware River drainage and the other from the Susquehanna. Specimens were collected by electroshocker during July 1979. Gut content analysis revealed that the cutlips minnow diet varied with age. Major food items included larval trichopterans, especially hydropsychids, and also chironomidlarvae. Cutlips minnows did not exhibit obvious sexual dimorphism outside of their spawning season. Sex ratios tended to emphasize females, presumably related to higher spawning-related mortality among males. Scale analysis and length-frequency showed that individuals ranged up to IV+ years of age, with I+ and II+ age classes predominating. No significant differences between the length-weight relationships of the two populations were evident.

ISSN:0270-5060    

DOI:10.1080/02705060.1984.9664625

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The leachate from a coal pile used to fuel a heating plant, drains into a small second order stream in western Massachusetts. The attendant shifts in pH from 6.8 to 4.4 and A1 from 0.03 to 3.8 ppm were not unlike those associated with acid rain. This similarity prompted a field/laboratory study to examine the effects of low pH and toxic aluminum concentrations on primary productivity of a lotic habitat. Tubular substrates, colonized by the indigenous periphyton of a clean-water tributary (control), were Transferred to the contaminated stream and monitored for structural and functional perturbations. Net productivity, measured by O2evolution, was reduced to zero after 10 days exposure to the polluted stream. Further, all diatom and cyanobacteria motility ceased. To identify the effects of pH a part from those of Al, periphyton colonizing glass coils in the laboratory were exposed to water collected from the test site and the tributary. Subsequently, the control water was acidified with 0.02 N sulfuric acid to a pH of 4.4. Oxygen evolution then declined, after 5 days, to the same levels as the laboratory communities exposed to the test waters. While low pH alone was sufficient to eliminate net productivity, it did not restrict algal movement.

ISSN:0270-5060    

DOI:10.1080/02705060.1984.9664626

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Rates of leaf litter processing were investigated in four Texas streams during fall-winter. Assuming an exponential decay model, processing coefficients (-k) of some leaf species were among the highest yet reported (e.g.Celtis laevigata= 0.0619). Values for % loss day−1ranged from 0.54–6.00. However, when compensated for the higher water temperatures found in these streams compared to more northern streams, processing rates were equivalent or even slightly lower. It is hypothesized that (on a per degree-day basis) this slower processing rate may result from the depauperate shredder fauna in such Texas streams.

ISSN:0270-5060    

DOI:10.1080/02705060.1984.9664627

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The relationships among measurements of turbidity and chlorophyll and phosphorus were examined at six stations in Keystone Lake, Oklahoma from March to October 1981. Maximum chlorophylla, total phosphorus, and turbidity occur red in the upper reaches of the two main arms. It was not possible to predict adequately chlorophyllafrom Secchi disc readings due to interference by non-chlorophyll turbidity. Secchi disc depth represented 30 to 50% of the true photic zone and these two parameters were well correlated. Photic zone measurements were poorly correlated with phosphorus and chlorophylla. Nephelometric turbidity was strongly correlated with all parameters except chlorophylla. Carlson strophicstate index was of limited usefulness due to the weak relationship among parameters such as chlorophyllaand Secchi disc depth. Calculation of this index based on nephelometric turbidity strengthened the relationship.

ISSN:0270-5060    

DOI:10.1080/02705060.1984.9664628

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Organic seston was studied in a 3rd-4th order impounded river in southwestern Virginia, U.S.A. the hypolimnetic release reservoir had an area of 67-ha and was located in a 4860-ha watershed (90% forested). the objective of this study was to determine reservoir effects on seston quality by measuring microbial activity (respiratory electron transport) and chlorophyllaon river and reservoir seston. Seston was significantly more concentrated upstream of the reservoir than at other sites due to lentic sedimentation. Chlorophyllaassociated with reservoir seston was significantly higher than either imports or exports suggesting that reservoir seston was of higher quality than riverine seston. Seston microbial activity data supported this conclusion to some extent, being higher in the reservoir than at upstream sites and immediately below the dam. Five km downstream however, chlorophyllalevels were still low but seston microbial activity increased. We believe this to be a result of both greater numbers of respiratory microbes and increased respiratory activity of individual microbes. Through sedimentation of refractory riverine seston, in-reservoir autotrophic production, and high microbial activity downstream impoundments may contribute to maximizing lotic ecosystem efficiency.

ISSN:0270-5060    

DOI:10.1080/02705060.1984.9664629

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Individuals from three populations ofPectinatella magnificafrom different habitats in Ohio (U.S.A.) were analyzed for a variety of ecological and morphological parameters. Genic variation was analyzed using starch gel electrophoresis. Individuals from a lake and an estuary population showed no difference in length, width or stick attachment diameter. Individuals from stream habitat were significantly narrower than individuals of the same length from either the lake or estuary. Two (peptidase-2 and esterase-1) of seventeen presumptive genetic loci were polymorphic. Percent polymorphism (5.9%) and mean heterozygosity (0.013) were lower than values published for other bryozoans and invertebrates as a whole.

ISSN:0270-5060    

DOI:10.1080/02705060.1984.9664630

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor