Primary production values in Lake Ontario were low in winter, reached a maximum in midspring, declined during summer, and slightly increased in fall. Rate of increase of production for inshore waters (< 20 m depth) was greater especially in spring and early summer with a greater maximum reached earlier than in offshore waters. Assimilation numbers, mgC fixed/mg chlorophyll a per hour, in Lake Ontario were fairly constant over the lake with a yearly range of 1.2–1.6. Primary production showed a linear relationship to chlorophyll a concentration, as also occurred in Lake Erie.Lake Erie primary production varied in its three basins. Seasonally, in the Eastern Basin, production was highest in spring with a midsummer decline, and small peaks in fall. The Western Basin had a maximum in midsummer whereas the Central Basin had peaks in late summer and early fall. Assimilation numbers were highest in the Western Basin (up to 3.5 mgC/mg chlorophyll a per hour) and lowest in the mid-Central Basin and Eastern Basin with values of approximately 1.4 mgC/mg chlorophyll a per hour. A definite westerly increase of assimilation number was observed.Up to early summer, the two lakes were fairly equal in surface production but integral photosynthesis, mgC/m2 per hour was higher in Lake Ontario than in Lake Erie. The same was valid in November and December. In summer, Lake Erie was higher in production on both a mgC/m3 per hour and mgC/m2 per hour basis. For the period, April–December, Lake Ontario's total estimated yield was 170 gC/m2, whereas for Lake Erie values of 160, 210, and 310 gC/m2 were found for the Eastern, Central, and Western basins, respectively.

The Northern Wetlands Study (NOWES) was undertaken to better define the role of northern wetlands and particularly of the large continuous wetland of the Hudson Bay lowland. CO2, CH4, N2O, O3, and nonmethane hydrocarbons (NMHC)between the surface and the atmosphere were measured across a 140‐km transect, representing approximately 5000 years of peatland evolution. This transect was located in the southern portion of the Hudson Bay lowland. A second study of surface exchange was conducted in the subarctic region of the northern Hudson Bay lowland. Regional flux surveys were conducted by aircraft between the two study areas. An integral part of the study was to determine the size of the source/sink of various gases and to compare the flux estimates made by several different techniques.

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1988. Factors affecting the spatial distribution sf diatoms on the sudace sediments of three Precambrian Shield lakes. Can. J. Fish. Aquat. Sci. 45: 469478.Spatial heterogeneity in species cornpsition of surface sediment diatom assemblages was examined in three Precambrian Shield lakes sf different water chemistry and basin morphsmetry. The study revealed that one sample cannot adequately represent the "average'Vdiatom flora sf a lake. The results 0% cluster analysis, multivariate analysis sf variance, and analysis of covariance indicated that the lakes exhibited different patterns of spatial heterogeneity in their sedimentary diatom assemblages. In the morphornetricaily simple Plastic Lake the amount of variability was substantially lower than in the other lakes. In the morphometrically more complex Blue Chalk take and Chub Lake there was considerably more variability; however, very little sf the variability could be attributed to depth or basin shape. The variability in surface diatom assemblages was markedly higher in Chub Lake, probab9y as a result of the influx of diatoms from the wetlands surrounding the lake. Despite a significant amount of heterogeneity in sediment diatom composition within each Bake, between-lake differences were sufficiently high to suggest that comparisons betahreen lakes based on sedimentary diatom remains are probably valid if sampling sites are selected following prescribed criteria. bes auteurs snt 6tudi6 l'h6t4rcsg$n$itc5 spatiale de la composition en esp$ces d'assemblages de diatomees dans des mati&res s4dirnentaires presentes en surface de trois lacs du buclier pr6cambrien prksentapst une chirnie des eaux et une rnorphometrie de bassins differentes. Cktude a rnontre qu'un sesrl kchantillon we perrnettait pas de reprhenter adequatemerit la Fbre a moyenne )) en diatomees d'un lac. t'analyse par grapps, I'analyse de variance de variables multiples et I'analyse de covariance ont montr6 qsle les assemblages de diatom6es sedimentaires des lacs presentaient des regimes diff6rents d%6t&rog&n&it& spatiale. Bans le cas du lac Plastic, de msrphom4trie simple, le niveau de variabilite etait de beaucoup iw%&ieur 2 celui note pour les autres lacs. Dans les lcas Blue Chalk ete Chub, de msrphometrk plus csmplexe, la variabilit6 etait beaucoup plus iirnportante, mais tres pesr de cette variabilit6 puvait Gtae attribuke ia profondew ou % la forme du bassin. La variabilitk des assembiages de diatorn6es de surface &tait, de fason marquGe, plus 6lev&e dans le lac Chub. Ce ph&norn$ne s'explique prsbablernent par un apport de diatomks en provenance des terres humides entourant le lac. En d$pit d'knne het&rog&n&it& appreciable de la composition en diatornees des sgdirnents au sein de chaque lac, les &arts entre lacs 6taient sufTisammewt 6lev4s pour porter 3 croire qu'il serait possible d'effectuer des csrnparaisons entre lacs reposnt skar les diatsrn&s ddimentaires 2 la condition que I'on chsisisse les sites de pr&$vernent en respectant des crit&res bien d6finis. T he siliceous remains of sedimenw diat...