摘要:

Decomposition of leaves was compared among sites in a stream that originates deep in a cave and then emerges as a spring brook. White oak (Quercus alba) leaf packs and plastic controls were placed in four similar riffle areas: (1) in the cave above a sink hole; (2) in the cave below a sink hole; (3) in the spring under an overhang; and (4) in the spring exposed to direct sunlight (through a forest canopy). Flow, temperature, and other aspects of physical-chemical water quality were constant among sites while availability of natural leaf liter, food abundance and variety, light, and the number and types of invertebrates varied. Processing rates (−k) at the cave sites (1 = 0.0075, 2 = 0.0085) were faster than rates for white oak reported for surface streams, despite a paucity of invertebrates in the cave and similar temperatures. Leaf packs which received sunlight had ten times more invertebrates associated with them than those under the overhang, but similar processing rates (0.019 and 0.024 respectively). Because of these results, we suspect that the decomposition rates outside the cave were faster due to factors other than macroinvertebrates.

ISSN:0270-5060    

DOI:10.1080/02705060.1988.9665175

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Transport of seston and DOC was examined during storm flows in a disturbed and a natural blackwater, coastal plain stream. The disturbed stream had fewer retentive devices due to destruction of riparian vegetation by thermal effluents. Concentrations of seston declined linearly in both streams as the storms progressed. Particulate organic carbon concentrations were higher in the natural streams. However, at baseflow the relationship was reversed. Dissolved organic carbon did not change during storm flows. The retentive devices in the natural stream were ineffective at reducing transport during storm flows. The relationship between storm flows, retentiveness, and carbon transport may effect the diversity and density of invertebrates.

ISSN:0270-5060    

DOI:10.1080/02705060.1988.9665176

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Changes in the vertical distribution of sediment redox potential and nutrient availability were examined during the growth of freshwater macrophytes in a greenhouse facility.Sagittaria latifolia, an emergent macrophyte species with an extensive root system, markedly affected sediment redox, resulting in a change from reduced to oxidized conditions within six weeks. In contrast,Hydrilla verticillata, a submersed macrophyte species with a relatively minor root system, did not appreciably alter sediment redox. Nutrient uptake by both species substantially reduced concentrations of nitrogen and phosphorus in sediments. Decreased concentrations of sediment nutrients appear to have resulted primarily from nutrient uptake by macrophytes rather than from change in sediment redox potential.

ISSN:0270-5060    

DOI:10.1080/02705060.1988.9665177

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The problem of variability in benthic density estimates from stream sampling was reassessed using data from a number of stream studies, including our own. When data were analyzed assuming a negative binomial distribution and a tolerated precision of 40% of the mean, it was apparent that earlier estimates of hundreds of samples required to estimate density were inaccurate. Based on total numbers of organisms, in most cases, six samples were sufficient for a precision of 40%. Notably, from three samples on, variability (as measured by the coefficient of variation) actually increased with increased number of samples. Examination of two long-term studies revealed that taking three samples yielded reliable estimates of benthic density with reasonable coefficients of variation. However, such sampling schemes yielded significantly lower numbers of species than when six or 12 samples were taken. We suggest that six replicates, each a composite of two samples, would be sufficient for stream studies, by providing a reliable estimate of total density and a fairly complete species list.

ISSN:0270-5060    

DOI:10.1080/02705060.1988.9665178

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Twenty-three species of freshwater mussels (Mollusca: Unionidae) were collected by divers in May, 1987, at 32 sites on and between wing dams in Pool 7 of the upper Mississippi River. Five species (Amblema plicata, Obliquaria reflexa, Obovaria olivaria, Lampsilis ventricosaandQuadrula pustulosa) comprised 90% of the fauna and were found at 88–100% of the sites. Specimens ofActinonaias ligamentina, Plethobasus cyphyus, andStrophitus undulatus, last reported in 1930, and the endangeredLampsilis higginsi, last reported in 1966, were collected alive.

ISSN:0270-5060    

DOI:10.1080/02705060.1988.9665179

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Sampling of littoral cladoceran populations was conducted in the Fall of 1986 at four sites in Pennsylvania: a small man-made pond, a swamp, a natural glacial lake (Lake Lacawac), and an embayment of Lake Erie. Microhabitats sampled included various plant species, rocks, and the water column. Densities and percentages of individual species in the microhabitats were used to calculate community coefficients of similarity among and within microhabitats, and to perform ANOVA and SNK tests. Cladoceran communities were more similar within than between microhabitats, indicating there is significant variation in community structure among littoral microhabitats. Densities of some cladoceran species varied significantly among microhabitats.Acroperus harpae, Camptocercus rectirostris, andPleuroxus procurvuswere more abundant on plants than on rocks in the embayment.Chydorus brevilabrisandAlona guttatawere more abundant onMyriophyllumthanUlothrixin the pond. In Lake Lacawac,A. harpaewas more abundant on plants than rocks, whileAlona rusticaandC. brevilabrispreferred rocks.Bosminasp. showed significant diel density variation in Lake Lacawac. Also in this system, coexisting species ofAlonaandChydorusin the littoral zone showed evidence of density variation among microhabitats. Some species of cladocerans therefore seem to be specialized for certain microhabitats, and these specializations may be the basis for spatial partitioning of resources inmultispecificcommunities of these animals.

ISSN:0270-5060    

DOI:10.1080/02705060.1988.9665180

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Adults of the freshwater pulmonate snailPlanorbella trivolviswere maintained in aquaria at four pH levels of approximately 4.9, 5.9, 6.8 and 7.8. Adult mortality was moderate over 82 days (10–32%) and not related to the magnitude of pH reduction. Decrease in both shell calcium per unit tissue dry weight and shell calcium per unit maximum shell diameter were significantly related to both time of exposure and pH level. Both measures were significantly reduced after 53 days of exposure to acid water such that for mean Ca mg−1, pH 4.9=5.9 < 6.8 < 7.8 and for mean Ca mm−1, pH 4.9=5.9 < 6.8=7.8. Empty (ashed) shells without a periostracum lost CaCO3about 4.6 times faster than did shells of live snails with periostracum intact.

ISSN:0270-5060    

DOI:10.1080/02705060.1988.9665181

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Growth and community organization of submersed macrophytes were studied in a southern Wisconsin impoundment in relation to macroinvertebrates, fishes, and phytoplankton. Macrophytes covered 50 to 70% of the lake bed in summer, growing to a water depth of 3.5 m. Total biomass peaked in late July at 130 to 200 g dry wt/m2. Undisturbed macrophyte beds were stratified into canopy, midwater, and basal layers. Narrow-leaved pond-weeds (Potamogetonspp.) dominated among 13 vascular plant species. But mechanical harvesting, in the fourth and fifth years of the study, disrupted vertical stratification and exposed the lake bed to monotypic growths of water stargrass (Heteranthera dubia(Jacquin) MacMillin).

ISSN:0270-5060    

DOI:10.1080/02705060.1988.9665182

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Organic matter content was measured in 84 sediment profiles collected in navigation Pools 7, 8, and 9 along the upper Mississippi River. Organic matter content ranged from 0.25 to 22.80% with a mean content of 3.53 ± 2.06% but did not vary significantly (p = 0.05) with depth. Organic matter content in Pool 7 was significantly (p = 0.05) higher (4.81%) than that measured in Pool 8 (3.09%) or Pool 9 (3.20%). Organic matter content of sediment deposited between 1964–1977 was generally less than that in sediments deposited between 1954–1964 which was usually less than that in sediments deposited prior to 1954. Based on measured sediment accumulation rates in Pools 7, 8, and 9, the average influxes of organic matter for the period between 1954 and 1977 were 421, 265, and 328 g m−2yr−1, respectively.

ISSN:0270-5060    

DOI:10.1080/02705060.1988.9665183

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Estimates of density and biomass ofUrnatella gracilisLeidy, a freshwater filter-feeding entoproct, were made from samples obtained with a Petite Ponar grab sampler from a newly constructed riffle habitat in an abandoned channel of the Tombigbee River, near Columbus, Mississippi. Colonies of one (47%), two (49%), three (4%) and occasionally four stalks (individuals) were observed on gravel substrata. An average of 144,614 stalks·m−2were found. Ash-free dry weight biomass averaged 876.7 mg·m−2. This organism was dominant in terms of both density (92%) and biomass (51%).Urnatella graciliswas found to be a significant early colonizer of new substrata and an important member of the macroinvertebrate community.

ISSN:0270-5060    

DOI:10.1080/02705060.1988.9665184

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor