摘要:

The planktonic, periphytic (both submerged and emergent vegetation) and benthic rotifer communities of an alkaline freshwater marsh were studied from May 1979-May 1980. Of 32 species of rotifers recorded, 17 were common.Rotaria rotatoriadominated the four habitats examined throughout the entire study period. A succession of several other species appeared as dominants in concert withRotaria rotatoriaat various times of the year, in various habitats. Significant coefficients of correlation (p ≤.01) were found among 9 dominant species, also grouped by factor analysis as responsible for 53.1% of the community variance. Several physical-chemical characteristics were found to correlate significantly (p ≤.05) with the marsh rotifer community population dynamics. Differences in-diversity and population sizes among the benthic, periphytic, and planktonic communities were found.

ISSN:0270-5060    

DOI:10.1080/02705060.1983.9664596

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The influence of elevated water temperatures on fecundity ofCaenissp. emerging from large outdoor channels was investigated during the summer of 1980. Four temperature levels were provided: Ambient (Tennessee River, U.S.A.), and approximately 3°, 6°, and 9° C above ambient. Number of eggs per female ranged between 212 and 1787 at all temperature levels. A median test indicated a significantly lower number of eggs in females from +9 channels than from the other temperature levels.

ISSN:0270-5060    

DOI:10.1080/02705060.1983.9664597

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Filtering comb areas were greatest forDaphnia pulexandD. similis, and least forD. parvula, relative to body length. The slopes of the regressions of comb area body length were different from expected (based on simple geometry) forD. pulexandD. similis. Filtering rates of these daphnids in suspensions of inert sediment particles were less related to comb areas than they were to the gut filling capacity of these particles.

ISSN:0270-5060    

DOI:10.1080/02705060.1983.9664598

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A permanent pond at 3100 meters elevation was studied for an entire year to monitor zooplankton populations as they changed seasonally and associate those changes with biotic and abiotic factors. Conductivity, alkalinity, and dissolved solids were low during the summer but increased dramatically in the winter due to “freezing out.” Chlorophyll measurements indicated that phytoplankton reached its population maximum during the winter. The summer zooplankton community was dominated by the cladocerans,Holopedium gibberumandDaphnia rosea; the copepod,Diaptomus leptopus; the rotifers,Keratella cochlearis, Conochilus unicornis, andPolyarthra dolichoptera; andChaoboruslarvae.D. roseadisappeared from the plankton in August, possibly due to a combination of predation and competition. All limnetic Crustacea disappeared during ice cover, leaving rotifers as the most successful winter plankters. The posterior spine ofK. cochleariswas long in the summer, and short or absent in the winter. This seasonal change in morphology may be a means of reducing mortality due to predation.

ISSN:0270-5060    

DOI:10.1080/02705060.1983.9664599

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Large variation in presence and size of barbels and development of barbel papillae in longnose dace (Rhinichthys cataractae) is described. Larger dace seemed to have larger barbels and more papillae but the correlation coefficients for these relationships are low.

ISSN:0270-5060    

DOI:10.1080/02705060.1983.9664600

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

We investigated the distribution of benthic macroinvertebrates in four aquatic habitat types in the lower Mississippi River: dike fields, a natural bank, a secondary channel, and an abandoned channel over a high flow (flood stage), two moderate, and two low flow periods. The biotas present in the natural bank, the secondary channel, and the abandoned channel showed only minor changes in composition over the various flow regimes. The natural bank was consistently dominated by the burrowing mayfliesTortopus incertusandPentagenia vittigeraand hydropsychid caddisflies; the consistently most common taxa in the secondary channel were the sand-dwelling chironomidsRobackia clavigerandChernovskiia orbicus; phantom midges, tubificid oligochaetes, and fingernail clams were always the most abundant macroinvertebrates in the abandoned channel. The dike fields, however, showed large changes in biotic composition over the different flow regimes. These compositional changes correlated with changes in river stage and resultant alterations in current and substrate. This study indicates that the distribution of macroinvertebrates in the lower Mississippi River is a function of the physical characteristics of the system, notably current velocity and substrate composition.

ISSN:0270-5060    

DOI:10.1080/02705060.1983.9664601

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A new extractant consisting of 0.2N acetic acid, 0.25N ammonium nitrate, 0.015N ammonium fluoride, 0.012N nitric acid, and 0.002N ethylenediaminetetracetic acid was used to extract P, K, Ca, Mg, Fe, and Cu from a natural lake substrate and from artificially prepared substrates. The precision and effect of extraction time on nutrient yield were measured on the natural substrate. The growth response of hydrilla (Hydrilla verticillata, Royle) to concentrations of the nutrients estimated with the extractant and to N was measured. Extractable P and Fe increased with extraction time whereas extractable Cu decreased. Extraction time had no effect on extractable K and only the 5 min extraction time resulted in significantly lower yields of Ca and Mg. Hydrilla shoot weight increased linearly under laboratory conditions as nutrient concentrations increased in the rooting media, suggesting that growth was limited by nutrient availability to the roots. High correlation among the nutrients prevented determination of a single limiting nutrient. Concentrations of P and K in rooting media were positively related to concentrations in hydrilla tissue, but when there was 153 μg P/g and 8 μg K/g or more in the rooting media, P and K content of hydrilla tissue remained constant. Concentrations of N, Ca, Mg, Fe, and Cu remained constant throughout the range of these nutrients in the rooting media.

ISSN:0270-5060    

DOI:10.1080/02705060.1983.9664602

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The distribution of the turbulent component of vertical diffusivity for heat (Khz′), and the relative contributions of vertical mixing and solar radiation to heating, in the stratified layers of the mixolimnion of bio-genitally meromictic Green Lake, Jamesville, NY, were evaluated for a six month period of 1978. Field measurements included temperature and PAR (photo-synthetically active radiation) extinction profiles, collected biweekly on 13 occasions, and continuously monitored incident PAR. Khz′ varied temporally and vertically. The values were particularly low in the metalimnion, where the major mechanism of vertical heat transfer was absorption of solar radiation coupled with molecular diffusivity. Most of the heating in the hypolimnion was accomplished through turbulent processes. The vertical distribution of Khz′ was well described by Khz′ = b(N2)m, where b and m are ecosystem specific constants, and N is the Brunt-Vaisala frequency, supporting a previous theoretical prediction and the results of a similar field investigation. The specific distribution in Green Lake (m = −0.60) indicates the turbulence is largely generated by local small scale processes.

ISSN:0270-5060    

DOI:10.1080/02705060.1983.9664603

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Comparisons of Surber sampling of natural substrates and multiplate artificial substrates were made in Trout Creek, a mountain stream in northwest Colorado. Multiplate samplers were placed in the stream and allowed to be colonized for five weeks. Surber samples were taken when multiplates were collected. Multiplate samples generally provided statistically lower density and biomass estimates and number of species than the Surber samples although species diversity was similar with both methods. The seasonal pattern in abundance was dissimilar for the two methods. Greatest density from Surber sampling was found in fall whereas multiplate artificial substrates had their lowest density in fall. Coefficients of variation for biomass values were consistently lower on the multiplates than for the Surber samples but varied considerably for density and number of species. It was concluded that multiplate samplers were not as practical as natural substrate sampling in Rocky Mountain streams.

ISSN:0270-5060    

DOI:10.1080/02705060.1983.9664604

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The role of grazing fish in the phytoplankton dynamics of solar silo microcosms was examined by following the quantitative effects of grazing as measured by chlorophyll a (chla), total protein (TP), and phytoplankton cell counts for 15 weeks. Qualitative effects during this period were measured by recording phytoplankton community composition changes. Three treatments were used: a control silo with no fish, two “low” density silos containingOreochromis aureusat 8 m−3, and two “high” density silos containingO. aureusat 17 m−3.

ISSN:0270-5060    

DOI:10.1080/02705060.1983.9664605

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor