Variations à court terme des compartiments planctoniques d'un lac humique du Bouclier canadien

Les variations spatio-temporelles à court terme des compartiments planctoniques ont été étudiées simultanément du 30 juillet au 5 août 1986 dans un lac humique du Bouclier canadien. L'abondance du bactérioplancton fluctue de 1,4 à 1,7.106 cell. ml.-1 (coloration DAPI) ou de 2,7 à 7,7.106 cell. ml-1; (coloration Acridine Orange). La production du bactérioplancton estimée par incorporation de 3H méthyl thimidine, varie de 4 à 24.106 cell. l-1 h-1. Les valeurs d'activité hétérotrophe potentielle bactérienne estimée par assimilation de 14C glucose, s'échelonnent de 0,007 à 0,065 µg C.l-1. h-1. La biomasse pigmentaire (chlore. a et pheopigments) varie de 6,8 à 21,7 mg.m-3 . La production primaire est très faible (max. : 10 mg C. m-3 .h-1; 20 mg C.m-2 .h-1 ) et décroît très rapidement avec la profondeur (25 % à 82 % dans le premier mètre). Le microzooplancton (Rotifères, Bosmina, nauplies) représente plus de 90 % du peuplement zooplanctonique et les taux de broutage global du macrozooplancton sont faibles (25 % j-1). Les compartiments hétérotrophes prédominent dans le métabolisme du lac par rapport au compartiment autotrophe. Les patrons de variation spatiale reflètent la stratification verticale des compartiments et des processus autotrophes et hétérotrophes. Les maxima de photosynthèse, d'ATP et de production bactérienne se situent dans les eaux épilimnétiques tandis que les maxima d'abondance du bactérioptancton et des pigments se rencontrent dans l'hypolimnion. Le zooplancton est plus dense et broute d'avantage dans la strate 1-3 m. Ces variations spatiales semblent influencer l'activité hétérotrophe potentielle du bactérioptancton. Nos résultats montrent aussi des variations temporelles à court terme de la production primaire, de l'assimilation hétérotrophe et du broutage du macrozooplancton. Cette étude préliminaire met en lumière la nécessité de tenir compte des variations à court terme lors des études des relations trophodynamiques dans les écosystèmes planctoniques.Short term spatial and temporal variations in planktonic compartments were studied simultaneously, from July 30th to August 5th, 1986, in a humic lake on the Canadian Shield. Abundance of bacterioplankton ranged from 1,4 to 1,7 106 cell. ml-1 (DAP1) or from 2,7 to 7,7 106 cell. ml-1 (Acridine Orange). Bacterial production, as measured by incorporation of 3H methyl-thimidine, was estimated at 4-24 106 cells. l-1. h-1 and potential heterotrophic bacterial activity ranged from 0,007 to 0,065 µg C.l-1. h-1, as estimated by 14C glucose incorporation. Pigments biomass (chloro. a and phaeopigments) varied from 6,8 to 21,7 mg m-3. Primary production was low (max. : 10 mg C.m-3. h-1; 20 mg C.m-2. h-1) and decreased rapidly with depth (25-82 % in 1 m depth). Microzooplankton (rotifera, Bosmina, nauplii) accounted for more than 90 % of total numbers and macrozooplankton global grazing rates were low (25 % d-1). The heterotrophic compartments play a greater rate in the lake metabolism than the autotrophic compartment. Spatial variations reflect the stratification of the heterotrophic and autotrophic organisms and processes with depth. Maximum levels in primary production, ATP and bacterial production occur in epilimnetic waters, while maxima in bacterial numbers and algal pigments occur in the hypolimnion. Zooplancton density and macrozooplankton grazing rates were higher in the 1-3 m strata. These spatial patterns seem to influence the vertical profiles of the bacterial potential heterotrophic activity. Our results also show short term temporal variations in primary production, potential heterotrophic activity of bacterioplankton and macrozooplankton grazing rates. This preliminary study stresses the importance of short term variations in the assessment of the trophodynamics of the planktonic food wed

B844: Checklist of the Vascular Plants of Maine Third Revision

This is the third revision of the Checklist of Vascular Plants of Maine. Like its predecessors, it lists all ferns and related plants, conifers, and flowering plants native and naturalized in Maine and records their county-level distribution in the state. The first Check- list (Ogden et al. 1948) was based on specimens in herbaria at the University of Maine (hereafter referred to as MAINE), Portland Society of Natural History, New England Botanical Club, Gray Herbarium of Harvard University, and the private collection of Glen D. Chamberlain of Presque Isle, Maine (now part of MAINE). Bean et al. (1966) revised the checklist to include additions to the flora and update the nomenclature to follow Fernald (1950). Richards et al. (1983) added many new state and county records in the second revision. The purpose of this revision is twofold. First, we have included many new county and state records. Since Richards et al. (1983) there has been considerable collecting in Maine, much of it directed at searching for new state and county records in relatively neglected regions of the state. Second, there have been numerous changes in the scientific names of Maine plants since Fernald (1950), the nomenclatural basis of Richards et al. (1983). We have largely followed Kartesz\u27s (1994) nomenclature (see Taxonomy and Nomenclature section). Recent work on rare plants and establishment of an official list of endangered and threatened plants in Maine (Dibble et al. 1989; Maine State Planning Office 1990) also motivate updating the known distribution and taxonomy of Maine\u27s flora.https://digitalcommons.library.umaine.edu/aes_bulletin/1121/thumbnail.jp

Feasibility of trial procedures for a randomised controlled trial of a community based group exercise intervention for falls prevention for visually impaired older people: the VIOLET study

Background Visually impaired older people (VIOP) have a higher risk of falling than their sighted peers, and are likely to avoid physical activity. The aim was to adapt the existing Falls Management Exercise (FaME) programme for VIOP, delivered in the community, and to investigate the feasibility of conducting a definitive randomised controlled trial (RCT) of this adapted intervention. Methods Two-centre randomised mixed methods pilot trial and economic evaluation of the adapted group-based FaME programme for VIOP versus usual care. A one hour exercise programme ran weekly over 12 weeks at the study sites (Newcastle and Glasgow), delivered by third sector (voluntary and community) organisations. Participants were advised to exercise at home for an additional two hours over the week. Those randomised to the usual activities group received no intervention. Outcome measures were completed at baseline, 12 and 24 weeks. The potential primary outcome was the Short Form Falls Efficacy Scale – International (SFES-I). Participants’ adherence was assessed by reviewing attendance records and self-reported compliance to the home exercises. Adherence with the course content (fidelity) by instructors was assessed by a researcher. Adverse events were collected in a weekly phone call. Results Eighteen participants, drawn from community-living VIOP were screened; 68 met the inclusion criteria; 64 participants were randomised with 33 allocated to the intervention and 31 to the usual activities arm. 94% of participants provided data at the 12 week visit and 92% at 24 weeks. Adherence was high. The intervention was found to be safe with 76% attending nine or more classes. Median time for home exercise was 50 min per week. There was little or no evidence that fear of falling, balance and falls risk, physical activity, emotional, attitudinal or quality of life outcomes differed between trial arms at follow-up. Conclusions The intervention, FaME, was implemented successfully for VIOP and all progression criteria for a main trial were met. The lack of difference between groups on fear of falling was unsurprising given it was a pilot study but there may have been other contributory factors including suboptimal exercise dose and apparent low risk of falls in participants. These issues need addressing for a future trial