ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665102

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A chironomid,Brillia flavifronsJohannsen (Orthocladinii) previously thought to specialize on decaying wood, consumed Tag Alder leaves (Alnus rugosa(Du Roy)) in two Michigan streams, Schwartz Creek and the Ford River. Schwartz Creek's substrate is primarily sand and the principle allochthonous inputs are White Cedar (Thuja occidentalisL.) needles and wood. The Ford River's substrate contains cobble and gravel. The primary inputs are deciduous leaves, with the majority being Tag Alder. Fresh Tag Alder leaves are commonly found in streams in the western Upper Peninsula, owing primarily to high beaver activity and secondarily to wind activity. Substantial green leaf inputs occur at a time when the previous year's leaves have been processed. In Schwartz Creek,B. flavifronsmay be the primary shredder species, as the biomass ofB. flavifronsexceeded the biomass of all other shredder insect species combined on fresh green Tag Alder leaf packs and autumn senescent Tag Alder leaf packs. This chironomid appears to prefer to feed on fresh leaves: Larval mean biomass and field growth rates were significantly higher on fresh than on autumn leaves. In the Ford River,B. flavifronsis not the primary shredder, as the biomass of other shredder species exceeded the biomass ofB. flavifronson both leaf types. In the Ford River,B. flavifronsappears to prefer to feed on fresh leaves more than autumn leaves: Larval mean sizes were significantly higher on fresh than on autumn leaves. We hypothesize that (1) fresh green leaves are chemically richer and have surfaces that are richer in microflora and microfauna to account for the increased growth rates and/or higher mean biomass values forB. flavifronson fresh green leaves, and that 2) increased resource competition by other shredder species in the Ford River may account for the lower growth rates and/or lower mean biomass values ofB. flavifronsobserved on both leaf types in that river.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665103

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Physical and biotic processes of three low-order southeast Alaska streams located on Prince of Wales Island were studied. These streams drained an undisturbed watershed representing a coniferous climax forest, a recently logged watershed with little riparian regeneration, and a logged watershed with heavy riparian growth. Community respiration and production were measured in closed, recirculating 12-L Plexiglas metabolism chambers using the dissolved oxygen method. Gross production among the streams varied from 0.1–2.7 g 02-m−2-d−1; respiration varied from 0.1–1.0 g 02-m−2-d−1. Highest rates of production and respiration occurred in the recently logged stream; lowest rates were measured in the mature, climax forest stream. Seasonal differences in production and respiration were apparently influenced by logging.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665104

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The effects of increased turbidity and epilimnetic phosphorus concentration on the distribution of phytoplankton chlorophyll-a due to short-term disturbances (siltation and humic-stained runoff) were studied in Dunham Pond, CT and Lake Annie, FL. Both stratified systems exhibited similar responses. Well-developed deep chlorophyll layers decreased in intensity and epilimnetic chlorophyll-a increased as a result of the disturbances. The observed similar phytoplankton responses from a temperate dimictic lake and a subtropical monomictic lake are consistent with published theory relating the occurrence of deep chlorophyll maxima with trophic status in stratified lakes.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665105

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Techniques using alternative solvents to the standard acetone extraction procedure are superior and may become widely used for chlorophyll analysis. Dimethyl sulfoxide/acetone and dimethylformamide offer similar advantages of quick, efficient extraction. However, comparisons of methods using these solvents with the method using acetone demonstrated that for the efficient analysis of natural phytoplankton assemblages, glass-fiber filters should be extracted with maximum exposure to solvent. Storage of extracts is not recommended but if necessary, storage should be at −20°C. Furthermore, all investigators proposing to replace the acetone extraction with one of these methods are advised to perform similar comparisons before adopting either alternative.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665106

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Erpobdella octoculata,Glossiphonia complanataandHelobdella stagnaliswere collected from the stony littoral of four productive and four unproductive English lakes at monthly intervals over one year. A serological technique, the precipitin test, was used to identify the presence of lumbriculid, naidid, tubificid and enchytraeid oligochaetes in the gut of the leeches.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665107

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The construction and operation of a portable nearshore water sampling device is described. The device can be extended to collect samples up to 15 metres from shore and operates efficiently under a variety of open water conditions as well as under ice too thin to walk on.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665108

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The assemblage composition, following selective taxa removal, was examined on already colonized rocks in a North Carolina, piedmont stream. The taxa removed were either the net-spinning caddisflyCheu-matopsyche sp.or the case-building chironomidRheotanytarsus sp.. Handled rocks with no removals were the controls. Since both taxa were numerically dominant at the start of this study but occuppied different amounts of rock space, we hypothesized that the colonization dynamics following the removals would be different between the two treatments.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665109

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The aquatic Crassulacean Acid Metabolism (CAM) plant,Littorella unifloravar.americana(Fern.) G1., was the subject of some preliminary investigations to determine (1) if the source of the nocturnally accumulated carbon is endogenous, from respiration, or is exogenous, (2) if this carbon was stored primarily as malic acid, as is typical for the CAM pathway and (3) if the nocturnally accumulated carbon was photosynthetically incorporated during the subsequent light period.Littorellaplants were collected from the field and held in the labor-atory under different levels of CO2, light, and temperature. The diurnal malic acid rhythm in leaves ranged from 46 to 60 μmoles · g−1fresh wt., Radiocarbon studies showed that endogenous CO2(from dark respiration) accounted for 30 to 99% of the nocturnal carbon accumulation. Paper chromatography revealed that the nocturnally incorporated, labelled carbon was primarily in the malate pool, with some labeling of the citrate pool. All of the nocturnally acquired carbon remained within the leaves, as carbohydrate rather than as malate during the light period. These results confirm that nocturnally accumulated carbon is stored as malic acid and is quantitatively incorporated into the plant during the subsequent light period. Evidence indicates that inLittorella, CAM can result in the effective recapture of nocturnally respired CO2and that this endogenous carbon may account for 50% of the nocturnal carbon accumulation under field conditions; however, a more robust experimental approach is needed for confirmation.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665110

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Seasonal changes in species dominance and size structure of littoral Cladocera were investigated in a mainstream reservoir in southwest Virginia. Twenty-four species of benthic, vegetation-dwelling, and pelagic cladocerans were captured during the study. The assemblage was dominated numerically by smallBosminaandChydorus, while larger vegetation-dwelling species such asAlona,Eurycercus,Latona, andSidatypically accounted for the majority of biomass. The number of species captured was relatively constant from May through November with decreasing dominance as the season progressed. Seasonal dynamics of individual species resulted in significant shifts in frequency distributions of numbers and volume across size classes. Overall, the assemblage was divided seasonally as dominance shifted from pelagic to vegetation-dwelling species in mid-July.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665111

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor